CA2249237A1 - Catheter apparatus and methodology for generating a fistula on-demand between closely associated blood vessels at a pre-chosen anatomic site in-vivo - Google Patents

Abstract

The present invention provides catheter apparatus (10, 200) and catheterization methodology for generating an arteriovenous fistula or a veno-venous fistula on demand between closely associated blood vessels and at a chosen anatomic site in vivo. The catheter apparatus is preferably employed in pairs, each catheter of the pair being suitable for percutaneous introduction into and extension through a blood vessel. The catheterization methodology employs the catheter apparatus preferably in conjunction with conventional radiological techniques in order to place, verify, and confirm a proper alignment, orientation, and positioning for the catheters in vivo prior to activating the perforation means for generating a fistula. The invention permits the generation of arteriovenous fistulae and veno-venous fistulae anatomically anywhere in the vascular system of a patient; nevertheless, the invention is most desirably employed in the peripheral vascular system as exists in the extremities of the body to aid in the treatment of the patient under a variety of different medical ailments and pathologies.

Description

W O 97/33522 PCTrUS97/02800 CATHETER APPARATUS AND METHODOLOGY FOR GENERATING A
FISTULA ON-DEMAND BETWEEN CLOSELY ASSOCIATED BLOOD
VESSELS AT A PRE-CHOSEN ANATOMIC SITE IN-VIVO

FIELD OF THE INVENTION

The present invention is conce" ~ed with improvements in catheter 10 design and usage in-vivo; and is particularly directed to catheleri~alion apparatus and methods for creating an arteriovenous fistula or a veno-venous fistula between adjacently positioned blood vessels.

BACKGROUND OF THE INVENTION
A catheter is a long flexible tube introd! ~ced into a blood vessel or a hollow organ for the purpose of introducing or removing fluids; implanting medical devices; or for pel rur",i"y diagnos~ic tests or therapeutic interventions. Catheters are conventionally known and frequently used; and 20 a wide range and variety of catheters are available which are exl,e",ely diverse in shape design and specific features.
Typically a catheter is a long thin tube of fixed axial length with two discrete unique ends. One end is designed and engineered to be inserted in the body; the other end yenerally ~er~ains outside the body and is so 25 designed. Most ~II,eter~ have at least one inler~,al lumen of a volume sufficient to allow for on-de~a~ ~-1 p~ss~e of a diverse range of wires rods liquids gases lrans~,itlingenergy fiberoptics andspecificallydesigned medical instruments.
The fundamental principles and requirements for constructing a 30 guiding flexible catheter exist as conventional knowledge in the relevant technical field; and all of the essential info"naliol1 is publicly known widely disseminated and published in a variety of authoritative texts. The medical and technical literature thus provides an in-depth knowledge and understanding of the diagnoslic and lherapeutic uses of conventional 35 catheters and co~r,r"o,)ly used catl ,eteri a~ion techniques. Merely represe,)lali~e of the diversity of publications now publicly available are the SlJL.;~ 1 l l UTE SHEET (RULE 26~

.. ., ., ~. ~ . .

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following, each of which is expressly incorporated by referellce here:
Diaqnostic And Therapeutic Cardiac Catheterization, second edition (Pepine, Hill, and Lambert, editors), Williams & Wilkins, 1994 and the refetences cited therein; A Practical Guide To Cardiac Pacing, fourth edition (Moses et. al., 5 editors), Little, Brown, and Company, 1995 and the references cited therein;
Abrams An~ioqraPhy~ third edition (H.L. Abrams, editor), ~ittle, Brown & Co., 1983; Dialvsis Therapy, second edition (Nisse"son & Fine, editors), Hanley &
Belfus Inc., 1992; and Handbook of Dialysis, second edition (Daugirdas &
Ing, editors), Little, Brown and Co., 1994.
Thus, in accordance with established principles of conventional catheter construction, the axial length of the catheter may be composed of one single layer or of several layers in combination. In most multilayered constructions, one hollow tube is stretched over another tube to form a bond;
and the components of the individual layers determine the overall 15 characteristics for the catheter as a unitary construction. Many multilayeredcatheters comprise an inner tube of Teflon, over which is another layer of nylon, woven Dacron, or stainless steel braiding. A tube of polyethylene or polyurethane typically is then heated and extruded over the two inner layers to form a firm bond as the third extemal layer. Other call ,eter constructions 20 may consist of a polyurethane inner core, covered by a layer of stainless steel braiding, and a third external jacket layer formed of polyurethane.
In addition, a number of dual-lumen o~LI ,elers are known today which differ primarily in the size and spatial relationship between their individual lumens. Typically, a dual-lumen calheler can take many dirrerent forms such 25 as: two co-axially positioned lumens where one small di~"~eter tube exten.ls axially through the internal volume of a larger diameter tube; or the catheter is a single large diameter tube and has a centrally disposed inner septum which divides the i"lerior volume into two equal or unequal intemal lumens;
or where the material suhst~rlce of the call ~eter tube contains two disc, ete 30 bore holes of differing diameters which serve as two ir~le" ,al lumens of unequal volume Iying in parallel over the axial length of the cdll,eter. All of these variations present clirrere"l dual-lumen constructions for catheters having a similar or identical overall diameter size.
Calheter~ are generally sized by external and intemal dia",eter and 35 length. The internal dia~eter is specified either by actual diameter (in thousandll ~s of an inch or millimeters or French size). Many newer thin-SUBSTITUTE SHEET (RULE 26) CA 02249237 1998-09-1~

W O 97/33522 PCT~US97/02800 walled catheter designs provide a much larger internal lumen volume to external diameter ratio than has been previously achieved tnis has resulted in catheters which can acco~ odate much more volume and allow the passage of much larger sized articles through the internal lumen. External diameter is typically expressed in French sizes which are obtained by multiplying the actual dia~eter of the catheter in millimeters by a factor of 3.1415 (7~). Conversely by traditional habit the actual size of any caU,eter in millimeters may be calculated by dividing its French size by a factor of tl. As an illustration of size usage. French sizes from 4-8 are currently used for 10 diagnostic angiography. In addition because of the variation between slai,darcJ thin-walled andsuperhigh-flow~ll,eterconstructiondesigns a wide variety of external and internal lumen diameter sizes exist today.
In order to perform effectively in speci~li7ed medical procedures and in particular anatomical areas specific c~te~ories or classes of catheters have 15 been developed. Among the presently known specific types of catheters are:
peritoneal catheters employed for peritoneal dialysis and which provide dialysate inflow and oufflow for the removal of the by-products of metabolism from the blood; acute and ch~ onic urinary calhet~r~ introduced into the bladder the urethra or directly into the renal pelvis for the removal of urine;
20 central venous catheters are designed for inse, lion into the internal jugular or subclavian vein; right heart catheters such as the Cournand and Swans-Ganz catheters designed specifically for right heart catheteri~alio"; transeptal ~ll ,eters developed specifically for crossing from right to left atrium throughthe inte, dlrial septum at the fossa ovalis; angiographic cathete, ~ which are 25 used for right or left ventriculograpl ~y and angiog~apl ,y in any of the major vessels; corona~ y anyioyl a~c)l)ic cath~ler~ which include the .lirrerenl series of grouping including Sones Judkins Amplatz multipurpose and bypass graft catheters; as well as many others developed for specific purposes and medical conditions.
An illustrative and representative example of traditional catheter usage is provided by the medical specialty of hemodialysis - the process by which extra water and toxic metabolites are removed from the blood by a dialysis machine when the kidneys are impaired by illness or injury. A summary review therefore of renal insufficiency or failure the technique of hemodialysis and the role of specialized c~lhet~r~ in ~achi.,e dialysis will de",onsl~ale and evidence conventional limitations.

SI~S ~ ITE SHEET (RULE 26) CA 02249237 1998-09-1~

A wide variety of pathological processes can affect the kidneys. Some result in rapid but transient cessation of renal function. In patients so affected temporary artificial filtration of the blood is sometimes necessary.
With time renal function gradually improves and may approach normal; and dialysis is therefore usually required only for a short duration. The time required for the kidneys to recover will depend on the nature and severity of the injury which typically varies from a few days to several months Thus if the acute condition lasts for more than three or four days the patient will probably require hemodialysis at least once while awaiting retum of renal 1 0 function.
Other pathological conditions result in a gradual deterioration of renal function over months or years. These patients can go for quite some time before toxic concentrations of metabolites accumulate. Once they reach the stage where dialysis is necessary however it is usually required for the rest of their lives. Some of these patients retain tow levels of renal filtration andcan thererore be dialyzed as infrequently as once a week. Many progress to total renal failure and require hemodialysis two or three times each week.
Still other types of renal injury result in rapid onset of per",al1ent renal failure necessilalin~ life long dialysis.
The dialysis machine serves as an artificial kidney to reduce harmful concentrations of the by-products of metabolism and to remove excess water from the blood. The machine is essentially a special filter in series with a blood pump. The filter is connected to the patient via t~o blood lines. Blood drains from the patient to the dialysis machine through the drrerenl line; and avolume displace"~el-l pump provides suction to assist drainage. The same pump pressurizes the blood to over~;o",e the resistance imposed by the filter.
The filter makes use of a semiper",eal,le n,e"lbr~r,e which separales the blood path from that of dialysate a speci~l buffered solution used to clear rillered s~bst~nces. Unwanted molecules diffuse through the se",ipe",~iable ",embra,)e into the rapidly flowing dialysate and are carried out of the filter in a manner analogous to that of urine flowing through a renal tubule. The membrane is incGr~oraled as multiple pleated sheets or small caliber tubes to increase the surface area across which diffusion may take place. Blood leaving the filter returns to the patient through the second or efferent blood line.

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W O 97/33522 PCTrUSg7/02800 The ability to perform dialysis effectively is dependent on high flow of blood through the filter. Furthermore, blood must be returned to the patient as rapidly as it is withdrawn to prevent the hemodynamic consequences of large fluctuations in intravascular volume. It is therefore necessary that both arrere, It and errere~ ll blood conduits be connected to the patient by way of transcutaneous c~lheter~ inserted into large bore, high flow blood vessels.
For patients in whom renal recovery is anticipated, percutaneous intravenous access is used frequently. This technique makes use of a large bore flexible two-lumen catheter. This caLheter, measuring 10 French, (roughly 3mm in diameter) is introduced into the central venous circulation via the subclavian or internal jugular vein. Place",enl of transcutaneous venipuncture in conjunction with the SeJdinger technique and serial dilation is used; and the tip of the cdlhe~er is positioned at the junction of the superior vena cava and the right atrium. Alternatively, the call,eter is placed percutaneously in the femoral vein. Blood is withdrawn from one lumen and returned through the other. The afferent lumen ends 2 or 3 cenlimelers from the catheter tip which inl ,ibils recirculation of ~rerel1l blood. The large size and high blood flow of the superior vena cava per",ils very effective dialysis with this technique.
Unfortunately, however, this r"etl~Gd of percutaneous intravenous Acc:ess is not well suited for patients who will require long term or permanent dialysis. The presence of a foreign body (the Access catheter) breaching the skin is Associ~ted with a high risk of ir~rectiG". This risk increases with time, and in long term applications, is prohibitive. BecA~Ise the foreign body is in an intrav~ca IlAr location, the i~ Irection is usually Assooiate~l with sepsis, or infection of the blood stream, which can be lethal. Special c~tl,eter~ are designed to be implanted or "tunneled" subcutaneously for several ce,lli",eters to decrease the incidence of sepsis; and if ~t~solntely sterile technique is used when manipulating the c~LI ,eter (and the skin exit site is meticulously cleaned and dressed), these tunneled catheters can be used for several months without incident. Despite pristine care, however, infection is inevitable with extel1c~ecl use; and all such cdLheters eventually must be removed. Aside from sepsis, long term central venous Access is also associated with a time relaled increase in the risk of endocal~ilis, cardiac pe,ro,dLion from cdll,eter tip erosion, and superior vena cava lillo",bosis.

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Patients who require permanent or lifetime hemodialysis therefore must be attached to the dialysis machine in a different way.
Two methods have evolved to provide long term v~sc~ r access in patients on permanent dialysis. The first method involves surgically 5 implanting a 6 or 8mm dacron or gortex tube graft subcutaneously in the upper extremity. A small transverse incision is made in the p,u~imal fo~ea~,...
just below the crease. One end of the tube graft is anasto~osed to the side of the brachiai artery and the other to the side of a large antecubital vein.
The body of the graft between the two anasto~oses is tunneled just below 10 the skin in a horseshoe configuration with the bend at the mid rorea"".
Blood flowing through the tube bypasses the capillary bed and as such represents a very low resistance pathway. This surgically created "short circuit" in the circulatory system is referred to as a shunt. The low resistancein the shunt results in a high blood flow. To perform hemodialysis two large 15 bore needles are sterilely introduced into the graft lumen through the intactskin. This can be readily accol",l~lished as the graft in its subcutaneous location is easily palpated. The large lumen and high blood flow provide excellent drainage for dialysis. After hemodialysis is colllpletecl the needles are removed so no per" ,a,)enl breecl, in the skin exists. Each time the 20 patient is dialyzed needles are reintrod~ ~ced.
The second method involves the creation of a direct arteriovenous fistula between the radial artery and an ~dj~cent vein - without the use of a prosthetic graft material. Once again the capillary network is byp~ssed and a low resistance "short circuit" in the circulatory system results. The direct 25 and increased volume of biood flow through the fistula leads to massive venous dilation. Dialysis catheters are then introduced into the dilated veins.
To create an al leriovenous fistula for permanent h emodialysis an incision is made at the wrist and the radial artery identified and mobilized. Anacljacent vein is mobilized as well. After obtaini"g vascular isolation with 30 vess~l loops or soft cla,nps the artery and vein are opened longitudinally for a distance of ~ to 8mm. Using fine monofilament suture and magnified visualization the arteriotomy and vel,oton,y are sewn together creating a side-to-side anaslo",osis (or aller"~ ely the end of the vein is sewn to the side of the artery). This surgically created connection allows blood to bypass 35 the capillary bed and results in d~ a"~alically increased flow through the ~on:d"" veins. In contrast to the shunt technique of the first ~eti,od there is SUBSTITUTE SHEET (RULE 26) , .

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WO 97/33522 PCTt~JS97/02800 no easily palpable prosthetic graft just beneath the skin that can be entered transcutaneously. However, because the arteriovenous fistula is performed at the wrist, the thin-walled forearm veins are subjected to high blood flow;
and, over a short period of time, dilate to 2-3 times their initial size. The 5 massively dilated veins are easily identified and can be ~ccessed by two large bore needles as described above for the shunt.
Each of the two surgical techniques has retative advantages and disadvantages. The shunt, although simple to construct, involves implantation of a foreign body. Each time a needle is introduced 10 percutaneously, there is risk of infection of the graft with skin organisms. The risk of infection is not as great as was described for the indwelling intravenous dialysis catheters, but is still present. With meticulous aller,lionto sterile technique, shunts of this type can be mainLail ,ed for years.
Hemodialysis patients often have impaired immune systems, however, and 15 infection requiring shunt removal is not u"cor"",on. A second problem seen with prosthetic shunts is that of lI,rc",llJosis necessilali"g lh,o,),bectomy orrevision. Reactions take place between the prosthetic material and the platelets in the blood that result in liberation of clotting factor~. These factors stimulate aL,nor",al growth of the intima, or lining of the vein, at the venous 20 anaslon,osis. This ab"or~al growth narrows the anaslo",osis resulting in decreased flow through the graft and tl " on)L,osis. Hemodialysis patients often require multiple operations for tl " ur"bectomy and shunt revision throughout their lives to maintain vascular access.
The direct arteriovenous fistula ",elho.l is highly desirable and 25 advantageous in that no prosthetic material is implanted; and the risk of infection is the,erGre dra",~tically reduced In addition, all blood carrying surface are lined with living intima, and intimal proliferation is very u"col"l"on. Moreover, the vein, being composed of living tissue, has the ability to mend itself and is less likely to form pseuclo~rleurysms as is 30 occasionally seen with proslhelic shunts after extended use. For these reasons, most sur~eons prefer to perform this procedure when it is technically feasible.
~ Unfortunately, in many palients, use of an arteriovenous fistula is technically not possible by conventional means. As described above, the 35 radial artery is dissected out at the wrist; and a distal dissection zone is preferred in that more veins will be subjected to increased flow and dilation, SU~;, 1 l l UTE SHEET (RULE 26) CA 02249237 1998-09-1~

WO 97/33522 PCT/US97tO2800 resulting in more potential sites for hemodialysis needle insertion. However, the radial artery is somewhat small at this distal location which makes anastomosis technically more demanding, especiaily in smaller patients.
Furthermore, because a direct anastomosis must be constructed, a relatively large vein is needed in the immediate vicinity of the radial artery, and this isnot always present. In the allernati"e, if a vein more than a centimeter away is mobilized and brought over to the artery, venous kinking can occur which results in decreased flow and early Illlolllbosis. In addition, mobilization of the vein disrupts the tenuous vasovasorum, the miniscule arteries that provide blood supply to the vein wal itself, which can result in fibrosis of thevein wall and constriction of the vein lumen. This sets the conditions for earlyfistula failure.
Note also that each of the procedures described above must be done in the operaling room. Most of the patients thus receive intravenous sedation and must be monitored postoperatively in a recovery room envirc"""ent.
Some remain hospitalized for a day or more as per the surgeon's prererence.
It is well known that individuals with renal failure exhibit illl,uailt:d wound healing and a co~promised immune function. These patients are therefore at increased risk for developing posloperali~e wound complications.
The conventional and limited usage of speci~li7ed cali,eters as examplified by the medical practice of hemodialysis is thus well demonsl, aled and rcvcalcd. Clearly, despite the recognized desi(ability and advantage of creating an arteriovenous fistula for long-term or life-use patients needing dialysis, the use of catheters has remair,ed limited and used primarily for the 2~ introduction and removal of fluids while the creation of arteriovenous fistulae remains the result of skilled surgical effort alone. Thus, although there is a long sla"d;ng and well recognized need for an improved procedure and/or vehicle for generating arteriovenous fistulae, no ,,,ear,ir,yrul alle",ali~/e has been developed to date; and no catheter-based ",etnodology or protocol has ever been envisioned as suitable for on-demand generalio, I of an arteriovenous fistula in-vivo.

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SUMMARY OF THE INVENTION

The present invention has multiple aspects and formats. One aspect of the invention provides a catheter for generating an arteriovenous fistula or a veno-venous fistula on-demand ~etween closely associated blood vessels at a chosen anatomic site in-vivo said catheter being suitable for percutaneous introduction into and extension through a blood vessel and comprising:
(a) a tube having a fixed axial length a d,screte proximal end a discrete distal end and at least one internal lumen of preclete""ined volume;
(b) a distal end tip adapted for intravAsc~ r guidance of said tube through a blood vessel in-vivo to a chosen anatomic site;
(c) magnet means positioned at said discrete distal end and set in axial aliy",l,e"l with said distal end tip of said tube said ~"agnet means having sufficient magnetic force to cause an adjusl",e"~ in position for said tube when in proximity with a source of ",agnetic attraction disposed within a closely associated blood vessel;
(d) vAscul~r wall pe, roralion means positioned at said discrete distal end a~jace"t to said ",ay"et means and set in axial aliyn",e"l with said distal end of said catheter said ",a~" ,et means having sufficient ",agnelic sl, e nylll to cause an adjust",enl in position for said ~li ,eter when in proximity with an aller"alive source of magnetic attraction disposed within a closely associdted blood vessel;
(d) vascular wall perforation means positioned at said discrete distal end AdJ-cenl to said mag"et means and set in axial aliy"menl with said distal end tip of said tube said vascular wall ,~.el roraliGn means becor"ing intravAsclJ~~~ly A-ljusted in position via the magnetic force of said magnet means when in proximity with a source of magnetic attraction disposed within a closely Associ-te~l blood vessel in-vivo; and (e) means for activating said vAscl~lAr wall pe~roralion means of said tube on-~lel "and wherein said vAsc ul:~r wall pel roralion means pe, ror~tes the ~;hosen al ,atGr"ic site to generate a fistula in-vivo between the closely A~sori ~ted blood vessels.
A second aspect of the present invention provides a calheterization 3~ method for generating an arteriovenous fistula or a veno-venous fistula on-SUBSTITUTE SHEET (RULE 26) . ,.. _ .. ..... ,. ., ... . .... ~ .......

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W O 97/33522 PCTrUS97/02800 demand between closely associated blood vessels at a chosen anatomic site in-vivo, said catheterization method comprising the steps of:
procuring at least one catheter suitable for percutaneous introduction into and extension through a blood vessel in-vivo to a chosen anatomic site, 5 said catheter being comprised of (a) a tube having a fixed axial length, a disc(ete proximal end, a discrete distal end, and at least one internal lumen of predetermined volume, (b) a distal end tip adapted for intravascular guidance of said tube through a blood vessel in-vivo to a chosen anato",ic site, (c) magnet means positioned at said discrete distal end and set in axial aliy"",enl with said distal end tip of said tube, said magnet means having sufficient magnetic force to cause an intravascular adjustment in position for said catheter when in pl U~ ily with a source of magnetic attraction disposed within a closely associdled blood vessel in-vivo.
(d) vascular wall pe, foraliorl means positioned at said discrete distal end adjace~ ll to said magnet means and set in axial alignment with said distal end tip of said tube, said v~scl ll~r wall pe, foration means becoming intravascularly adjusted in position via the " ,aynelic force of said magnet means when in proximity with a source of may"elic atl,acliû,) disposed within a closely ~ssoci~ted blood vessel in-vivo, (e) means for activating said v~scl ~ r wall p~, furalion means of said catheter on-demand wherein said v~scl ll~r wall ~ue, roralion means pe,rurales a chosen anatomic site in-vivo between closely associated blood vesseJs;
percutaneously introducing said catheter into a first blood vessel and extending said call ,~ter intravasc~ rly to a chosen analo"~ic site adjacent to a closely associated blood vessel;
percutaneously introducing a source of ",aynelic attraction into a closely associated second blood vessel and extending said source of magnetic attraction intravascularly to the chosen analoi"ic site to be in transv~sa II:~r proximity to said extended catheter;
permitting a transvascular ",ay"etic attraction to occur between said magnetic means of said extended catheter in the first blood vessel and said source of magnetic attraction in the closely associated second blood vessel whereby said v~sc~ r wall pe~ foralion means of said call ,eter comes into SUBSTITUTESHEET(RULE26) .. . . .............. . .. . . . .
. .. . ..... .

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transvascular alignment with the closely associated second blood vessel; and then activating said vascular wall perforation means of said catheter on-demand wherein said v~scul~r wall perforation means perforate the vascular 5 walls of said closely associated blood vessels concurrently at the chosen anatomic site to generate a fistula in-vivo.

BRIEF DESCRIPTION OF THE FIGURES

The present invention may be more completely and easily underslood when taken in conjunction with the acco",panying drawing in which:
Figs. 1 A-1 E illustrate of the modified Seldinger technique as a series of manipulative steps;
Fig. 2 is an overhead view showing a pre~e"ed embodiment of a 15 venous catheter used to generate an arteriovenous fistula;
Fig. 3 is an overhead view showing a p,eferled embodiment of an arterial calileter used to generate an arteriovenous fistula;
Fig. 4 is an overhead view of the venous introducer cylinder forming a col"!~onent part of the ~Jrefer,~d venous catl,eter of Fig. 2;
Fig. 5 is an overhead view of the venous obturator fitting into the introducer cylinder of Fig. 4 and forming a component part of the preferred venous call ,eler of Fig. 2;
Fig. 6 is an overhead view of the venous introducer cylinder of Fig. 4 and the venous obturator of Fig. 5 in col"bi,)alion;
Fig. 7 is an overhead view of the tubular cutting tool forming a componenl part of the ~u~e~r~ ed venous cdll ,eter of Fig. 2;
Fig 8 is a partial sectional view of the distal end of the tubular cutting tool of Fig. 7;
Figs. 9A-9D are sequential sectional views .le,)lo"sllaling the consequence of activating the v~scul~r well perforation means in the tubular cutting tool of Fig. 7;
Fig. 10 is an overhead view showing the venous introducer cylinder of Fig. 4 and the tubular cutting tool of Fig. 7 in combinalion;
Fig. 11 is a side view of the distal end of the arterial catheter of Fig. 3;

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Fig. 12 is a partial sectional view of the preferred venous catheter of Fig. 2 and the preferred arterial catheter of Fig. 3 in proper parallel alignment as a consequence of magnetic attraction and ir,teracLion;
Fig. 13 is a side view of the distal end of a second alternative 5 embodiment of a catheter suitable for generating an arteriovenous fistula in-vivo;
Fig. 14 is an axial-section view of the altemative catheter embodiment of Fig. 13;
Fig. 15 is a cross-section view of the second alternative catheter 10 embodiment of Fig. 13 along the axis W;
Fig. 16 is an axial-section view of a pair of alternative embodiment catheters in proper parallel alignment for generating an arteriovenous fistula;
Fig. 17 is an illustration of the vascular system in the human forearm in which an intravascular ultrasound probe has been extended into the radial 1 5 artery;
Fig. 18 is an illustration of an intravascular ultrasound-created image showing the radial artery wall and the ~1; cerl~ly positioned veins using the probe of Fig. 17;
Fig. 19 is an illustration of an extended intrav~sc~ ~lar ultrasound probe 20 within the radial artery at a site of arterial-venous proximity;
Fig. 20 is an illustration of an ultrasound-created image showing the radial artery wall and immediately adjacent veins using the probe of Fig. 19;
Fig. 21 is an illustration showing the percutaneous introduction of a venous cylinder-obturator complex and its place",e, ll near the ultrasound 25 probe in the radial artery;
Fig. 22 is an illusl~ alio, I of an ultrasound-created image showing the exislence of the venous cylinder-obturator complexed in the selected vein at the site of arterial-venous proximity;
Fig. 23 is an illustration showing the venous catheter and the arterial 30 ~Ihe~er in the ~ cer,l blood vessels under simulated in-vivo conditions;
Fig. 24 is an illustration of a fluoruscopic-created image showing the aliyl ""e"l between the venous catheter and the arterial catheter of Fig. 23;
Fig. 25 is a sectional view of the aliy,)r"ent overlap between the distal end of the venous catheter and the distal end of the arterial catheler under 35 simulated in-vivo conditions; and Sll~ UTE SHEET (RULE 26) ,. ... . . . . . . . ... ... .. .

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Fig. 26 is a cross-section illustration of the aligned venous call,eter and arterial catheter showing the act of perforating vascular walls to generate an arteriover10us fistula.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The present invention is a percutaneous arteriovenous fistula catheter (hereinafter "PAVFC") apparatus and methodology which will generate a fistula between an ~ cenll~/ located artery and vein or an adjacently located 10 pair of veins in the peripheral v~scul~r system. The arteriovenous (hereinafter "AV") fistula or veno-venous fistula (hereinafter '~") is created in a controlled manner between closely ~ssoci?led blood vessels! ideally in the distal extremities (arms or legs) of the patient. However usage at any anatomic site is possible; and the AV (or W) fistula can be generated on-15 demand at a prechosen v~sa~l~r site under carefully n,or,ilored clinicalconditions. As such the present invention provides multiple advantayes and unique benefits to both the physician and the patient some of which include the following.
1. The present invention is not a surgical procedure as such. To 20 the cG"Ifary the PAVFC appaldtus and ~l~ethodology is a radiological technique which avoids the use of surgical incisions and procedures and eliminates the need for surgically created AV (and W) fistulas. It is well recognized that chronically ill patients such as renal failure patients have an i,npairecJ wound healing capacity; are subject to an increased incidence of 25 infe~;tior~ after surgery; and are subject to a high risk of l1e,llo,ll,aye as a consequence of surgical procedures. The present invention ~e~ ils the generation of AV (or W) fistulas without necessilali"g surgery or surgical incision thereby reducing the risk to the chronically ill patient. In addition by the avoidance of surgical procedures as such the need for an operating 30 room an anesthesiologist and surgical nursing staff is obviated.
2. The prese,)l invention allows for AV or W fistula for" ,alion in al)a~u~ical areas where surgical procedures would be difficult if not i,npossible to perform. For e~call,~le in I ,e",o.lialysis surgical ~ccess for the creation of an AV fistula is often limited to the distal radial artery. However 35 often there is not an ~ cel Illy posilio~ ~ed or closely ~ssociqted distal vein of sufficient size in the same anatomical area which is surgically ~ccessible. In SUBSTITUTE SHEET(RULE26) . . .

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comparison the PAVFC technique comprising the present invention generates fistula in the peripheral v~scul~r system between closely associated arteries and veins where traditional surgical exposure would be impossible in most instances. Accordil1gly the present invention allows for and has the potential to utilize many more v~cul~r sites in the peripheral circulation as locations for the generation of an AV fistula on-demand.
3. The present invention allows for the identification and evaluation of juxtapositioned blood vessels in the entire extremity (preferably by use of intrav~sc~ r ultrasound to identify the most favorable a"at~",ical 10 site) in order to provide an accurate assessment of venous diameter at a specific vascular site prior to pei ru~ inSJ the technique to generate an AV or W fistula. Peripheral veins of small diameter or having thin walls which are typically unsuitable for surgical a"aslG",osis are easily located and now become available for use; and the deter",ination of whether or not a portion of the venous vascular wall is closely associated with and lies ~djacent to an artery (or vein) can be routinely made.

4. The present appa~&l~s and methodology allows the radiologist to determine with subslanlial certainty whether or not a suitable vein exists inthe vicinity of a closely ~ssocialed peripl ,eral artery (or vein) prior to beginning the requisite sequence of steps necessary to generate a fistula.
Not only is the juxtapositional determination made but also the specific site ischosen in advance which provides the best combination of anatomical circumstal ,ces (including anatomic location arterial venous proximity arterial diameter and venous dia",eter). In this manner the radiologist may thoroughly consider a given v~sclll~r site for ye"e,ali,lg the fistula; determine whether or not to seek a more favorable lo~lio" in the same closely assoçii~d vein and artery or in another artery and vein in the same exl, ~" ,ily; or whether to redirect the Cdll ,eter appardlus into another exl, ~"~ily in order to find a more favorable analo",ical site.

5. The apparatus and method of the presei ,l invention also provide a most i,nporla"l benefit in that the blood vessels are not ~issected out or manipulated as a prerequisite of AVfistula ~Illldlion. The tenuous vaso vasorum lt,ererore remains preserved in the naturally occurring state a circu",slance which improves v~scul~r pale,)cy. This benefit stands in conl, ast to the loss of the vaso vasorum and other undesirable consequences of v~sc~ r manipulation necessitated by conventional surgical AV or W

SUBSTITUTESHEET(RULE2~) .. ~ . .. ..

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~5 fistula creation which cause injury to the delicate vein wall and result in contraction of the vein - a condition which limits the vein s ability to dilate and may contribute to early fistula failure. Moreover although introducing the catheter of the present invention into a vein may be traumatic to the venous 5 endothelium at the site of entry the injured segment of the vein wiJI be distal to the AV fistula and patency of this injured segment is not necess~ry for proper fistula function. In addition as the p~ocedure for fistula formation is performed at sites of close arterial venous approximation no venous distortion or kinking occurs or is necess~ry in the creation of the fistula.

6. The present invention provides far less risk to the critically or chronically ill patient in cG",~rison to conventional surgical procedures for creation of AV (or W) fistulae. The PAVFC technique offers fewer potential problems than routinely occur with conventional surgical procedures; and these relatively few potential problems relate primarily to the risk of 15 he",o"i~age. However even this potential risk of he",or,l,age is deemed to be small; is clinically obvious if and when it occurs; and is readily controlledwith direct pressure using a conventional blood pressure cuff or manual cGIl~presslon.

7. The present invention is il~ ed to be employed in multiple 20 use circu~slances and "ledical applications. An envisioned and particularly desi,a~le circu~"sla"ce of usage is to provide long term vascular ~ccess for hemodialysis for those patients requiring permanent or long term dialysis.
Additionally the PAVFC technique can be used to create AV fistulae for the ad~"il1isl,ation of caustic chem~tl,erapeutic agents. In each of these 25 instances the PAVFC technique will not only identify one or more favorable vascular sites in the radial and ulnar arteries along their peripheral length but also will identify other ~dj~cenlly positioned veins and the most desirable al)alo~ al sites within the closely Assoc!-ted vein particularly when Iying within the distal portion of the fored~ . In addition to these particular usa~es30 the ,~ . esent invention allows for the generation of an AV or W fistula for any othermedicalpurpose condition orcircu",sla"ce. Thus thePAVFC
technique can also be desirably used for creation of acJ~iliGi ,al v:~scul~r interc~""ections in the peripheral blood circulation between arteries and veins; to generate a greatly enlarged blood vessel seyl"e"t in the peripheral 35 vascular system which then would be surgically e3~cised and employed as a vascular bypass graft or harvested on a pedicle in anolher a"dlon,ical area SUc~ UTE SHEET (RULE 26) CA 02249237 l998-09-l~

W O 97133522 PCTrUS97/02800 and to generate on-demand aller"alive blood circulation pathways between arteries and veins in the peripheral vascular system when blockages and other vascular obstructions exist.
In order to facilitate ease of understanding and to provide a complete 5 and comprehensive descri~lio,l of the present invention in all its aspects, a detailed disclosure of the catheter apparatus and methodology will be presented in separate sections seriatim. The presentation will be made in the following sequence: A description of the theoretical support for the technique; a summary of conventional prDcedures for surgically introducing 10 and routing a catheter into the body of a living human; a description of the preferred and several alternative catheter embodiments comprising the present invention; an illustrative example showing the intended usage of the catheter apparatus in-vivo; and a representative description of some intended applications and use circu",s~a"ces for the present invention. Taken 15 cumulatively and collectively, the entirety of the disclosure not only describes embodiments of the prefer~ ed and alle" ,dli~/e calheter apparatus but also enables the reader to make and use the present invention productively without major difficulty or doubt.

I. Theorelical Support for the Invention The present invention inte,1-Js and expects the radiologist or attending physician to create a fistula in-vivo between an acJ~acently positioned and closely associated vein and artery (or between two closely associated veins) in the peripheral v~scul~r system of a chronic or critically ill patient. In effect and result, ti ,erefore, the present invention generates a direct flow connection between a functioning artery and vein (or between two functioning veins) without the existence or usage of intervening capillaries.
To generate the AV fistula, the present invention pe, roraLes the immediately ~ c~l ,t v~scul~r walls of both the vein and the artery concurrently, directly, and in tandem. Moreover, unlike conventional surgical procedures to create fistulas and shunts, there are no sutures used to join the v~scul~r walls at the point of perforation; and no synthetic or artificially introduced means for joining or attaching the pe~ rur~led vein to the ~e, roraled artery are employed in order to obtain hemostasis at the point of a~,aslo",osis. It may therefore seem counterinluitive to the reader that an AV
fistula can be generated as described without exsanguination into the arm or SU..~ UTE SHEET (RULE 26) ... . ..... . . . . . .

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leg of the patient and without risk of blood loss or even death as a consequence of performing the methodology.
The principle that enables an arteriovenous fistula to be created in this way, however, is clearly demonstrated clinically and is encountered 5 frequently. Unintended acquired arteriovenous fistulas are encountered occasionally in evaluation of patients with penetrating trauma such as knife stabbings, gun-shot hoies, and other perforations of the body c~used by violent acts. Physical exam of the wound in these individuals demonsl,a~es venous engorgelllenl of the involved extremity in conjunction with an audible 10 bruit or even a palpabte venous thrill. Subsequent arteriogram of the wound area demonstrates an arteriovenous fistula in the vicinity of the knife or missile tract. Other patients also with vascular injury after penel,dling trauma, however, do not develop arteriovenous fistulae. Most of these patients are found instead to have a pulsatile mass without pronounced 15 venous engorgement; and an a,leriog,d", of these patients del~,onsl,ales a pseudoaneurysm or contained rupture of the injured vessel. Note that these two types of injuries are almost never seen in tandem. It is extremely unusual for a patient with an arteriovenous connection to have a pseudoaneurysm, and vice-versa. Similarly, some patients develop an arteriovenous 20 conne-:tion bet~een the common fel"oral artery and the femoral or sapl ,enous vein as a complication of percutaneous arterial ~ccess, whereas others develop pseudoaneurysms; but the two clinical findings are almost never seen together in one patient. Yet all of these patients are similar in that they have sustained substantial injury to a sizable artery. The difrarence 25 in clinical ri"dinys thus lies in the spatial relationship existing between the injured blood vessels in-vivo.
In each example cited above, the patient has sustained an arterial vascular injury, either by knife, bullet, or angioy~ d,lJhic needle. The tissuessurrounding the peripheral artery are adherent to the adventia (or outer layer 30 of the artery wall), but can be dissected off by an ex~,ar,cJi"g hel"a~o,~,a. The blood extravasating through the arterial injury does so at arterial pressure which provides the force necessary for the continued expansion. The h~",alol"a (or clotted blood collection) Iyses within a day or two, leaving a juxta-arterial cavity that communicates with the vessel lumen. The resulting 35 clinical finding is that of pseudoaneurysm. In some patients, however, there is also a closely associated venous injury concurrent with the arterial SUBSTITUTE SHEET (RULE 26) ., . , . . . , . ., , . , , . ~ ~ .. . .

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damage. If the venous injury is of sufficient size and appropriate orientation, an arteriovenous fistula results. Blood leaves the artery through the arterial injury; flows along the knife or missile tract; and enters into the vein throughthe venous injury. Moreover, bec~use the venous system has such tow 5 resistance, the hydrodynamic pressure generated in the vicinity of the injury is not sufficient to cause a dissecting hemalo",a. The high flow velocity between the artery and vein maintains the patency of the fistula thereafter.
It can be properly believed that every penetrating injury to an extremity is ~ssoci~ted with multiple arterial and venous injuries of various sizes. The 10 likelihood of developing an arteriovenous fistula after penetrating injury isthus related to the caliber of the blood vessels injured and the v~scl li~r geometry of the injury. If clean, linear perforations are made in in",lediately ~r~j~cent walls of 34mm blood vessels1 a fistula would almost certainly develop; and extravasation and pseudoaneurysm f~r-llalion would be most 15 improbable and highly unlikely.
The present invention thus relies on this clinical basis for support;
provides a catheter apparal.Js and a Illetilodology by which to ~ccess a~jacer,lly located arteries and veins in the extremities; and presents the means by which to gel lerate a pe, ror~lion on-d~mar,.l at a cl ,oseo anal~l "ic20 site in the peripi ,eral v~sa II:~r system between a closely associated artery and vein such that an aperture or hole is bored or otherwise created concurrently through both the acljace"l arterial and venous walls. A direct blood flow connection is thus generaled by which arterial blood passes through the perforation in the arterial wall and into the vein lumen, through 25 the aligned pe~ roralion in the immediately ~5 ~ce, IL, low resistance vein. The underlying principle and basis is clinically established and documented; and there is no meaningful doubt or unc~ lainty that an AV fistula can be created on demand and in-vivo within the extremities of the patient in a safe and reliable manner using the apparalus of the present invention, standard 30 catncteri~alion techniques, and conven~i~nally known radiological procedures.

SUBSTITUTE SHEET (RULE 26) CA 02249237 1998-09-1~

Il. Surgical Introduction And Routing Of A Catheter Into The Body Of The Living Human Catheterization involves a great deal of technical skill, complex instrumentation and mature judgment in order to choose among the 5 appropriate procedures and the various techniques which are now conventionally known and commonly available. Clearly, because the present PAVFC technique utilizes catheter intervention in critically or chronically ill patients, the physician must be very familiar with the available anatomical alternatives for ~ccessing the peripheral vascular system in order to select 10 the best site for introducing the catheter, the best route to the desired area of the body, and the optimal timing and other operative conditions in order to achieve the best results.
Catheterization as a general technique can be performed using any duct, tube, channel, or p~ss~eway occurring naturally or surgically created 15 for the specific purpose. Thus, among the naturally occurring passageways are the anus, the alimentary canal; the mouth, ear, nose, or throat; a bronchus; the urethrs; the vaginal canal andlor cervix; and any blood vessel.
However, clearly the most cor~ IO~ l used and critical route of ~ccess for the present invention is the introduction of calhelers into the vascular system.
20 For this reason, it is useful to describe conventional guiding catheters, and to briefly su~ ari~e the technique currently in use for introduction of catheters into the vasclllAr system as an illustrative example of general cathete~i~alion techniques.

25 Catheter introduction techniques There are two general methods currently in use for call ,ete~ i~alion.
These are: (a) percutaneous introduction using needles and guidewires; and (b) direct introduction after surgical isolation of the blood vessel of choice.
While either general method may be utilized at any site of the v~scular 30 system, practical and anatomical considerations will g~nerally dictate which - ap~cruach is most appro~l iale under the individual circun,sld"ces. Most often, however, the modified Seldinger technique is favored for use.
The percutaneous introduction of a calheter is best illusl, dled by the modified Seldinger technique which is conventionally known and shown by 35 Figs. 1A-1 F. Fig. 1A shows a blood vessel being punctured with a small gauge needle. Once vigorous blood return occurs, a flexible guidewire is SUBSTITUTE S~EET (RULE 26) CA 02249237 1998-09-1~

placed into the blood vessel via the needle as shown by Fig. 1 B. The needle is then removed from the blood vessel, the guidewire is left in place, and the hole in the skin around the guidewire is enlarged with a scalpel as shown by Fig. 1 C. Subsequently, a sheath and a dilator is placed over the guidewire as 5 shown by Fig. 1 D. Thereafter, the sheath and dilator is advanced over the guidewire directly into the blood vessel as shown by Fig. 1 E. Finally, the dilator and guidewire is removed while the sheath remains in the blood vessel as illustrated by Fig. 1 F. The catheter is then inserted through the sheath and fed through the blood vessel to reach the desired location.
The other general method for the introduction of c~ eters into the blood circulation is direct surgical cutdown. The surgical cutdown approach is generally used for the brachial approach or the femoral approach.
Cutdown procedure is often a complex surgical procedure and is used only when percutaneous arterial puncture (as described above) has been 15 unsuccessfully alle" ~ted. A far more complex and fully ~lesc, ipli~/e review of both these general catheteri~ation techniques is provided by the texts of:
Dia~noslic And Therapeutic Cardiac Call ,eteri~ion, second edition, 1994, Chapter eight, pages 90-110 and the references cited therein.
Accordillgly, for purposes of practicing the ~ ,ese"t methodology, any 20 and all generally known catheterization procedures, apparatus, and techniques which are conventionally employed and are in accordance with good medical practice are explicitly intended to be utilized as necess~ry in their original format or in a modified form. All of these general catheteri~aLion routing and use techniques are thus envisioned and are deemed to be within 25 the scope of the present invention.

General rules for choosinq an aPpr(,uriate site of bodY entry:
An axiomatic or general set of rules by which a physician can choose a proper or appropriate site of entry for introducing a guiding catheter into the 30 v~scul~r system of a patient for purposes of pe, ror",ing diaynoslic tests ortherapeutic interventions in-vivo is as follows: (a) always pick the shortest and straightest pathway possible or available; (b) identify the patency of an existing and ~ccessible artery or vein, the larger the diameter of the blood vessel the better; and (c) avoid arteries with obvious calcification or 35 atheromatous involvement.

SUBSTITUTE SHEET (RULE 26) .. ... .... . . . .. . .... .. . ....
.. . ... .. ..

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WO 97/33522 PCTtUS97/02800 A favored approach to introducinq the catheter into the body:
(1 ) The intended site for entry is prepared and draped in a sterile fashion.
(2) The skin over the large bore artery or vein is infiltrated with 1%
5 lidocaine for local anesthesia.
(3) A small skin nick is made over the anesll ,eti~ed area.
(4) Via the skin nick the large bore artery or vein is punctured using a single wall puncture needle.
(5) The amount and nature of blood returning through the needle is 10 evaluated for proper needle position.
(6) A 0.035 inch or 0.038 inch guide wire is passed via the needle into the blood vessel.
(7) A 4-9 French dilator is p~ssed coaxially over the wire and then is removed.

(8) A hemostatic 4-9 French introducer sheath and obturator are passed coaxially over the wire; and the obturator and wire are then removed.

(9) Via the he,noslalic introducer sheath the guiding cali)eter is passed through the blood vessel and located at the intended use site.
The des~i, ipliol, provided herein is merely a summary review of the 20 means and manner by which a catheter is properly introd~ ~ced into the body of a living human patient. The physician is presumed to be well acquainted and sufficiently experienced in all these general catheteri~alion techniques;
and the choices of which manner or mode or usage is preferable to a,lolher must be left to the medical discretion and judgment of the physician given the 25 specific problems and ailme~,ls of his patient.

Ill. The Unique Catheter Apparatus The call ,eter apparatus comprising the presel ,t invention can take many different and alternative forms and be constructed in a diverse range of 30 widely dir~erent el"bodime"ls. As a favored approach it is generally desirable that the catheter app~ratus col"plise two discrete catheters introduced into the body indeper,de, Illy but employed in ta~ ,deln in order to ger,e~ale an AV fistula in-vivo. Nevertheless in certain limited medical instances and under demanding medical circulllslallces it is both envisioned 35 and acceplable to employ a single callleter alone for percutaneous introduction and extensiol I through a vein or artery in order to generate an AV
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WO 97t33522 PCT/US97/02800 fistula on-demand. Thus although the use of a single catheter independently is the least desirable format and mode of usage of the present invention the single catheter construction and usage nevertheless will serve and provide the means for generating an AV fistula between an adjacently positioned 5 artery and vein at a chosen a,1atol"ic site in-vivo. However if the physician has a choice given the particular circu",sLdnces and ailments of his patient it is far more desirable that a pair of cdll ,eters be employed concurrently and intandem in order to achieve a far greater degree of certainty and reliability in the outcome.
A. A r~fer,~d First Embodiment.
A highly preferred embodiment of the catheter apparalus able to generate an AV fistula on-demand between a closely associated artery and vein at a chosen anatomic site in-vivo employs a pair of uniquely constructed 15 catheters concurrently and in-ta~ ,den~. The first cdllleter of the pair is suitable for percutaneous introduction and extension through a vein in-vivo to a chosen intravenous location and is illusl,aled by Fig. 2. As exemplified by Fig. 2 a venous catheter 10 is seen having a hollow tubular wall 12 of fixed axial length; an interlocking proximal end 14 the catl,eter 10; a discrete distal 20 end 16 and a co-axial internal lumen 18 which exte"Js from the interlocking proximal end 14 to the distal end 16. Other features of the venous catheter 10 are described hereinafter.
The second of the pair in this IJrefe,,ed e"~bodi"~ent of the catheter apparatus is exemplified by Fig. 3 which illustrates a second catheter suitable 25 for percutaneous introduction into and extension through an artery in-vivo toa chosen i"lraai lerial site. As exempiified by Fig. 3 an arterial catheter 200 is seen having a hollow tubular wall 202 of fixed axial length; two proximal portals 204 206 which toyether form a discrete proximal end 208 for entry into the internal volume of the c~ eter 200; a single discrete distal portal 21030 for passage of a guidewire; and a discrete distal end 212; and an internal lumen 214. Additional details for the arterial catheter are described hereinafter.
In this prerer,ed embodiment the construction some speciricfeatures and the designated purpose for each catl ,eter in the pair are markedly 35 different. While each c~tl)eter in the pair share conlr"on features for purposes of location finding and place",ent intrav~scul~rly this p,erer,ed SUBSTITUTE SHEET (RULE 26) ... . . . ... .... . ... ..

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embodiment of the apparatus emptoys the venous catheter as the active source and physical means by which the vascular walls are perforated in order to generate an AV fistula. In CGI Ill ast the intended arterial catheter serves as a passive source of reinforcement of aliy~ ,me,)l and of abutment 5 intrav~-scul~rty Due to these different functions and construction features the details of each catheter in the pair will be described in detail independentfrom the other.

The construction and orqanization of the venous catheter ~he essential component parts and their interrelationship is illustrated by Figs. 4-8 respectively. As seen therein Fig. 4 shows a hollow introducer cylinder 20 which is a thin wall tube having a large dia~eter internal lumen 22. The proximal end 24 is configured as a locking arrangement 26 comprising two anti-rotation support bars 28 30 an interlocking notch 32 and a flat interlocking surface 34. The internal lumen 22 extends through the entirety of the locking arrange",e"t 26. In comparison the distal end 36 terminates as a planar surface 38 and contains a cutout slot 40 in the tubular wall of the introducer cylinder 20. The internal lumen 22 extends through the planar surface 38 at the distal end 36; and the cutout slot 40 exposes a pol lion of the intemal lumen volume to the ambient environment.
A co""~onent part of the venous catheter is the internal obturator shown by Fig. 5. An obturator by definition is a structure which closes or stops up an opening such as a fora",el, or intemal lumen. As illustrated within Fig. 5 the obturator 50 is an extended rod-like hollow shaft of fixed axial length but having an external shaft clia",eter which is slightly smaller in size than the internal lumen 22 of the introducer cylinder 20 of Fig. 4. The obturator 50 has a small diameter internal lumen 52 which continues axially from the proximal end 54 to the distal end 56. The proximal end 54 is purposely configured as a semi-circular disc 58 having a exlended finger portion 60. The small diameter internal lumen 52 of the obturator 50 extends through the semi-circular disc portion 58 as shown. In co",pariso" the distal end 56 terminates as a tapered end tip 62 and contains a portal 64 of sufficient size for a conventional guidewire to pass there through into the lumen 52.
It is intended and expected that the obturator 50 of Fig. 5 will be fitted into the proximal end 24 of the introducer cylinder 20 (illustrated by Fig. 4) SUBSTITUTE SHEET (RULE 26) CA 02249237 1998-09-1~

WO 97t33522 PCT/US97/02800 and be extended through the large diameter internal lumen 22 along the entire axial length to form a cyiinder-obturator composite as shown by Fig. 6.
As seen therein, the locking arrangement 26 at the proximal end of the introducer cylinder 20 interlocks with the extended finger 60 and semi-circular 5 disc 58 of the obturator 50 to form a composite proximal end 70. Similarly, the distal tapered end tip 62 of the obturator 50 passes through the distal end 38 of the cylinder 20 to form a composite distal end 72.
Note that in this composite orientation illustrated by Fig. 6, the small diameter internal lumen 52 of the obturator 50 is longer in axial length than 10 the large diameter internal lumen 22 of the introducer cylinder 20; and that the cutout slot 40 of the introducer cylinder 20 exposes the obturator distal end 62 to the ambient environment at the composite distal end 72. Moreover, the portal 64 of the obturator 50 passes through the planar surface 38 of the introducer cylinder 20 and extends into the ambient enviro, ~ e~ ~t with the 15 concurrent exposure of the distal tapered end tip 62 and the portal 64 beyond the composite distal end 72.
The cylinder-obturator co",posite of Fig. 6 is the article to be percutaneously introduced into a peripheral vein and is to be extended intravenously through the peripl ,eral vein until a desired location is reached.20 The percutaneous introduction is achieved typically by positioning a guidewire in the desired vein, utilizing percutaneous venipuncture, guiding catheters, fluoroscopy, and conl(asl ve~oy,a,~hy. The back of the guidewire is first passed through the portal 64 at the distal end tip 62 and then passed through the internal lumen 52. The entire cylinder-obturator co",,l~osite is 25 then Qxtended over the guidewire into the vein. The guidewire introduced at the portal 64 will travel over the entire axial length of the inle~al Iumen of the obturator and exit at the composite p,oxi",al end 70 in a conventionally known manner. The cylinder-obturator composite is then extended intravascularly using the guidewire as the means for extension through the 30 vein. In this manner, the obturator acts as a support vehicle and stiffening rod for the venous catheter during initial introduction and place" ,e"l of the catheter in the vein.
When a v~sc~ site is chose" which is deemed suitable for use, the entirety of the obturator 50 is removed from the internal lumen 22 of the 35 introducer cylinder 20. The obturator of Fig. 5 is then to be entirely replaced and be substituted for by the tubular cutting tool illustrated by Figs. 7 and 8 S~Jts~ JTE SHEET (RULE 26) CA 02249237 1998-09-1~

W O 97/33522 PCTrUS97/02800 respectively. Fig. 7 shows the entirety of the tubular cutting tool as configured for this preferred first embodiment; and Fig. 8 shows particular details and individual structures existing at the distal end of the cutting tool.
As shown in Fig. 7 the tubular cutting tool 80 is an extended hollow tube 82 whose external diameter is sized to be only slightly smaller than the internal lumen diameter 22 for the introducer cylinder 20 of Fig. 4. The tubular cutting tool 80 itself has a small bore internal lumen 84 whose volume provides several capabilities. In part the internal lumen 84 serves as a communication p~ss~geway for carrying an actuation wire 86 which is 10 inserted at the proximal end 88 and conveyed via the internal lumen 84 to thedistal end 94 of the cutting tool 80. The ~ctuation wire 86 is employed by the physician to activate the vAscul~r wall pe, rordlio" capability on-demand. In addition the internal lumen 84 serves as a volumetric ,r Ass~geway for the conveyance of pressurized carbon dioxide gas from the proximal end 88 to 15 the distal end 94. A gas conduit 85 is allacl ,ed to and lies in fluid flow continuity with the internal lumen 84 at the proximal end 88. A source of pressurized carbon dioxide gas (not shown) is controlled by a stopcock 87 which introd-lces a flow of pressurized carbon dioxide gas at will into the volume of the internal lumen 84 for conveyance to the distal end 94. An 20 aperture 97 in the tubular cutting tool 80 at the distal end 94 provides for egress of the pressurized carbon dioxide gas after being conveyed through the internal volume 84.
Note also that the proximal end 88 is configured as an oval disc 90 having a rib 92 extending therefrom. The proximal end 88 thus forms part of 25 an interlocking system suitable for e"~ayell,ent with the locking a" dr,ge",ent 26 of the introducer cylinder 20 illustrated previously by Fig. 4 herein. The r~di~p~ e components of the cutting tool are non-axisymmetric which allows the polar (rotational) orientation of the cutting tool-introducer cylinder c~",posite to be determined fluoroscopically. The cutting tooi-introducer 30 cylinder composite can then be rotated by manipulating the proximal end to adjust polar orientation.
Fig. 8 (as a cutaway view) reveals the details of the distal end 94 of the tubular cutting tool 80. The distal end 94 has three specific parts: a tapered end tip 96; v~sc~ lr wall perforation means 98; and first and second 35 magnet means 1 OOa and 1 OOb positioned adjacent to and in axial alig""~enl with the v~scul~r wall pe~ ~ora~ion means. It will be recognized and SUBSTITUTE SHEET (RULE 26) CA 02249237 1998-09-1~

W O 97/33522 PCT~US97/02800 appreciated that (as shown within Fig. 8) the vascular wall pel roralion means 98 is situated near the tapered end tip 96 and is flanked by first and second magnet means 1 OOa and 1 OOb. However, the placement and ordered sequence of the magnet means 100a and 100b and the vascutarwall 5 perforation means 98 can be altered and i~ ,lerchanged in location as acceptable variations to the ordered sequence of parts presented by Fig. 8.
Furthermore, a single magnet means rather than use of a pair is acceplable as another variation of the construction and structure.
In addition, it will be seen that the actuation wire 86 extends from the 10 proximal end through the lumen 84 to the distal end 94 and connects with the v~-scul~- wall perForation means 98 such that the ,l~el ~oralion mechanism can be activated at will and on-demand by the physician retaining possession of the proxi,l,al end of the tubular cutting tool 80 which remains exposed to the ambient environment outside the skin.
Fig. 8 also reveals several notable features about the magnet means 1 OOa and 1 OOb and the vascular wall pe, ~o(alion means 98 respectively. The magnet means are housed within and conLail ~ed by the tubular wall of the cutting tool 80 entirely. The magnet means are desirably rare earth magnets or electromagnets having sufficient magnetic power and sl~l Iyll, to attract 20 and align another source of " ,ay, letic attraction such as a second catheterwith the magnetic properties in-vivo. The magnet means may be a solid rod or a configured bar of matter within the lumen of or integral to the tubular wall of the cutting tool. While the actual dimensions may vary widely and radically, a typical rare earth magnet will be configured as a cylindricai mass 25 8-1 Omm in length and 2-3mm in diameter. The magnetic means are firmty embedded within the inlerior of the tubular cutting tool and will not shift or change position or orientation after the tubular cutting tool 80 has been manufactured and completely assembled.
Note also that the vascular wa~l perforation means of Fig. 8 rests 30 completely within the interior volume of the cutting tool in the passive state but is elevated to become exposed to the ambient environment in the activated state. As is shown within Fig. 8, a fenestration 112 permits ambient exposure of a pe,roralil,g ",ecl,al)ism through the tubularwall of the cutting tool 80 via elevation onto a tracked template 1 10 which escalates the 35 pel rorali~n mechanism to a yl eater height from within the interior of th cutting tool 80. The particular pelroralion ",echanism illustrated within Fig. 8 SUBSTITUTE SHEET (RULE 26) CA 02249237 1998-09-1~

W O 97/33522 PCTrUS97/02800 is shown as a sliding electrode 1~4 through which radiofrequency cutting current is passed.
The means by which the pe, ~oraLion mechanism is activated and placed in appropriate elevated position to achieve pe~ roralion is shown by Figs. 9A-9D respectively. The actuation wire 86 provides the physician with the point of control. As the actuation wire 86 is pulled by the attending physician at the proximal end the sliding electrode 114 is elevated and moves along a set track on the template 110. The non-linear geometry of the track c~ Ises the electrode 1 14 to protrude through the fenestration 1 12 and 10 become exposed to the ambient environment over the entire length of the template distance. Sl~hse~uently when the actuation wire is advanced towards the distal end the electrode 114 travels in the reverse direction and returns to its original position within the interior of the tubular cutting tool 80.
In this manner the attending physician can activate and inactivate the 1~ perforation means at will; and cause the sliding electrode 114 to become exposed as a consequence of moving along a set track and distance; and then to subsequently withdraw and reverse its direction of travel such that it becomes enclosed again and protected by the tubular wall of the cutting tool 80.
During the activation of the sliding elecl,u.Je 114 a radiofrequency alternating current of predetermined amplitude (a) and frequency (f) is applied to the electrode and conducted through actuation wire 86 with a complimentary electrode disposed within the arterial catheter serving as the ground. The radiofrequency current traveling from the elevated electrode 114 in the tubular cutting tool 80 to the complir"e"lar~/ electrode in the arterial catheter thus is the active cutting force which creates a perforation through the v~scul~ walls on-demand. To provide sufficient and readily available radiofrequency current when and as required a conventional electrosurgical console (such as a BOVIE BARD or VALLYLAB console) is preferably used as a power source.
Concurrent with electrode activation the attending physician will also open the slopcocl; 87 and allow a flow of co~pressed carbon dioxide gas (C02) into the tubular cutting tool 80. P~ererably an electrically ~ctl~ted solinoid (not shown) is used to release a burst of co~pressed CO2 gas from 3~ the pressurized tank in sy"cl,ro,ly with the application of the radiofrequency current. The rcloascd burst of the con,pressed C~2 is delivered through the SU~S 11 l UTE SHEET (RULE 26) CA 02249237 l998-09-l~

W O 97/33522 PCTnUS97/02800 gas conduit 85 into the internal lumen 84, where it travels through the interiorof the cutting tool 80 to the aperture 97, and exits through the aperture 97 into the vein lumen. The volume of C02 gas exiting the aperture 97 transiently displaces the venous blood in the area of the fer,eslralio" 112 5 during the radiofrequency activation of the sliding electrode 1 14, a highly advantageous circumstance. Blood is an aqueous, electrolyte-rich fluid which conducts electrical current readily. As such, the tempora~
displacement of blood by C02 in the vein lumen (and after perforation in the arterial lumen as well) at the selected andlo",ic site is desirable to obtain 10 sufficient electrical current density at the point of electrode conlacl to cleanly incise and per ,etl ale through the v~scl ~l~r walls.
The complete venous catheter suitable for activation on-demand and for generating an AV fistula is shown by Fig. 10. Clearly, the insertion of the tubular cutting tool 80 into the internal lumen 22 of the external cylinder 20 in 15 a locked arrangement provides the venous catheter suitable for use in-vivo.
The cylinder-cutting tool composite of Fig. 10 is the complement and counterpart of the cylinder-obturator composite of Fig. 6. However, the functions of each composite construction are markedly dirre~e"l. Thus, whereas the cylinder-obturator composite of Fig. 6 provides a highly 20 desirable call ,eter for percutaneous introduction and extension intravenously through a peripheral vein to a specific location or chosen anatomic site, the cylinder-cutting tool composite of Fig. 10 provides the alignment and specific placement intravenously at a chosen anatomic site within the vein as well as providing the physical mechanism and means by which to pel rorale the 25 vascular walls of closely associaled veins and arteries concurrently. In addition, the r~licp~que non-axisy"lr"el,ic co",pone,)ls allowfluoroscopic identification and manual adjustment of polar (rotational) orien~aliG" of the cutting tool-introducer cylinder composite.

30 The construction and or~anization of the arterial catheter The arterial cdll ,eter is a long, flexible hollow tube having a fixed axial length, a discrete proximal end, a .~isc, t:te distal end, and at least one internal lumen of predeten~ined volume as is illustrated by Fig. 3 herein.
Typically, the axial length will vary in the range from about 40-150 35 cer,li,neters and the external diameter of the hollow tube will often be in the range from about 1.5-2.5 millimeters in size. While the proximal end of the Sl,~ )TE SHEET (RULE 26) . . .

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arterial catheter is conventional in most respects, the internal lumen of the catheter is preferably joined to and lies in ftuid communication with a source of com~.ressed carbon dioxide gas (C02) in a manner similar to that previously described herein for the proximal end of the venous catheter.
Thus, compressed CO2 gas is released on-demand from a pressurized tank;
is delivered via a gas conduit into the intemal lumen; and travels through the linear volume of the internal lumen to a distal aperture through which the C~2 gas exits into the arterial lumen in-vivo. The volume of CO2 gas exiting the catheter displaces at least some of the arterial blood in the anatomic area 10 of the electrode; and maintains the radiofrequency electrical current densityat the point of col llacl between the radio frequency electrode and the V:ISCI ll~r tissue. This will facilitate clean incision of the vascular walls.
The distal end of the arterial catheter is unique in structure, construction, and organization. A detailed showing of the distal end is provided by Fig. 11. As shown by Fig. 11, the arterial catheter 200 has a distal end 212 which is divided into four individual segments in series.
Farthermost is the tapered distal end tip 224 having portals 226 and 210 and non-axisymmetral lumen 227 for externalized pass~ge of a guidewire there through; and an aperture 234 for the egress of compressed CO2 gas into the arterial lumen. The tapered distal end tip 224, the portals 226 and 210, and the lumen 227 thus serve as and are adapted for intraarterial guid~"ce of the arterial cdlheter externally over a guidewire and through a blood vessel in-vivo to a chosen anato"lic site. In corllldsl, the aperture 234 is in direct communication with the axial internal lumen 214 and allows the passage of compressed CO2 gas through the catheter interior with egress via the aperture. This facilitates the creation of the AV fistula by ~iispl~cement of arterial blood on-demand at the chosen andlomic site.
Positioned adjacent to the tapered distal end tip 224 are a pair of rare earth magnets 228a and 228b which serve as the magnet means for this embodiment. The rare earth magnet pair 228 is set in axial alig"",enl with the distal end tip 224 and has sufficient magnetic power and strength to cause an adju~l~"ent in i~ aa~ lerial catheter position when placed in proxilllily with the Illaynet means of the venous cdlheter described previously herein.
The fourth structure is the fixed electlude 230 which serves as the electrical ground for the radiofrequency circuit; and which is positioned SUBSTITUTE SHEET (RULE 26) CA 02249237 1998-09-1~

adjacent to and flanked by the rare earth magnet pair 228 and which is set in axial alignment with the tapered distal end tip 224 of the arterial catheter 200.
The arterial electrode 230 provides intrav~su ~l~r support for a chose,1 portionof the arterial wall and completes the radiofrequency circuit during the perforation process in-vivo in order to generate an AV fistula. The remainder of the hollow tubular wall 202 and the axial internal lumen 214 are as previously desc, ibed.
Since magnetic interaction is deemed essential to the proper function of the arterial catheter the magnetic means prerer, ed in this embodiment is 10 the use of two rare earth ",ay"ets which will provide sufficient magnetic power to cause an intrav~scl ~ adjustment in position for the arterial catheter when in proximity to the magnetic means of the venous ~lheter in-vivo. Desirable ~ag"e~ic materials for use as magnet means thus include the neodymiun-iron-boron cG"~posilions and cobalt-samarium compositions.
15 Alternatively an electromagnet can be substituted in place of a rare earth magnet composition as a desirable ~agnelic means. In addition any other source of magnetism which can be delllonsl,aled to provide sufficient magnetic power (as conventionally measured and cleter",ined in Gauss) may be employed and positioned as an effective and useful substitute.
In comparison the arterial e~ectrode has two specific fun~lio"s in-vivo:
To provide a physical source of reinforce, nel ll and support during the processof pe, rorali"g both the venous and arterial v~sc~ walls concurrently; and to provide a grounding terminal for completion of the radiofrequency electrical circuit. The electrode may therefore be co",posed of any non-ferrous conductivemattersuch as carbon copper zinc aluminum silver gold or platinum.

Alle",ali~e catheter embodiments and fc"l"als In the preferred embodiment of the catheter a~ ardl~Js both the venous catheter and the arterial cdlheter cGm~ ise electrodes; and the active force for transv~cul~r pe~ ro~lion of the closely ~ssoci~ted vein and artery at a chosen analomic site is via the transr"ission of a radiofrequency electrical current at a predeter" ,i"ed a" ,~eraye and frequency from the electrode embedded in the aligned venous catheter through both v~sc~ walls to the grounding electrode within the aligned arterial catheter. The use of radiofrequency electric current however is only one means for ,l~e, rora~ing Sl,~ ITE SHEET (RULE 26) ... . ......

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W O 97133522 PCTrUS97102800 the vascular walls of a closely associated vein and artery in order to generate an AV fistula in-vivo.
In an alternative embodiment of the vascular wall performation means disclosed in detail hereinafter, a static discharge electrical spark is used to 5 perforate the vascular walls between the electrode in the venous catheter and the electrode in the arterial catheter. The electrodes in this alternative format would differ little in design and structure from those depicted in the preferredembodiment. Moreover, the displacement of venous (and arterial) blood by the introduction and subsequent release of compressed CO2 gas through the 10 catheter internal lumen in this alternative embodiment would also desirably occur as described for the preferred embodiment previously herein; but this usage and feature is optional and is not a necessary adjunct to the process of vascuiar wall perforation and AV fistula formation created by the use of a static electrical spark between the electrodes.
In still another embodiment of a useful catheter construction, the vascular wall perforation means can take form as a microscalpel of conventional design which may be elevated from and subsequently recessed back into the internal volume of the tubular cutting tool at the distal end using the fenestration and the tracked template of the venous catheter described 20 previously for the preferred embodiment. The microscatpel is used mechanically to incise and bore into the vascular walls without the aid of electrical current. The venous cutting tool is structurally similar to that disclosed as the preferred embodiment with the exception that the sliding electrode has been replaced by a sliding microscalpel, which is similarly 25 activated on-demand by the physician using the actuation wire. In this microscalpel embodiment, however, the presence of compressed CO2 gas at the anatomic site chosen for AV fistula formation has no advantage;
consequently, the gas conduit. the stopcock, and the source of pressurized C~2 gas as components of the venous catheter are unnecessary and 30 redundant. Furthermore, in this microscalpel constructionformat, the electrode disposed at the distal end of the arterial calheter in the preferred embodiment is now replaced and substituted by an abutment block (or anvil) segment which is positioned adjacent to and is flanked by at least one or a pair of rare earth magnets for catheter alignment as previously described.
35 The placement and orientation of the abutment block is similar to that shown for the grounding electrode in the preferred arterial catheter construction; but SUBSTITUTE SHEET (RULE 26) CA 02249237 1998-09-1~

W O 97/335z2 PCT~US97/02800 the abutment block is typically a cylinder or rod composed of hard and generally non-conductive, resilient matter which will provide firm support during the vascular wall perforation process; and also serve to confine the microscalpel cutting action to penetrating only a small and limited area of 5 arterial vascular wall at the chosen anatomic site - thereby preventing excessive vascular injury. The range of resilient materials suitable for the abutment block thus include hard rubbers, plastics such as LE)CAN or PLEXIG~ASS polymers, polycarbonate compounds, vinyl polymers, polyurethanes. or silicon-based compositions.
The functional relationship between the venous catheter and the arterial catheter Both the venous catheter and the arterial catheter comprise unique features at their respective distal ends which will provide proper alignment in-15 vivo in order that a AV fistula can be generated on demand. Clearly, it isenvisioned and intended that the venous catheter will be percutaneously introduced and extended through a peripheral vein until a desirable anatomic location is reached. Similarly, it is expected that the arterial catheter will be percutaneously introduced into and extended through a closely associated 20 peripheral artery until both the arterial catheter and the venous catheter lie in adjacent position, each within its own individual blood vessel. A
representation of this adjacent positioning between the preferred arterial catheter and the venous preferred catheter is illustrated by Fig. 12.
As shown within Fig. 12. each of the preferred catheters individually 25 will rest intrav~su ll~rly within its own blood vessel (which has been deleted from the figure for purposes of clarity) and lie in parallel alignment as a consequence of the magnetic attraction between the pair of rare earth magnets 228a and 228b of the arterial catheter 200 and the opposite pair of rare earth magnets 1 OOa and 1 OOb of the venous catheter 10. The magnetic 30 attraction between these four rare earth magnets is of sufficient magnetic power to cause intrav~su l~:3r adjustment in position for the venous catheter 10 and the arterial catheter 200 Iying within their individual, but immediately ~ij~cent, blood vessels. The magnetic attraction and force is thus a transv~scular effect and result whereby the magnetic field affects each of the 35 catheters Iying individually and separately in dirrerenL but closely associated blood vessels.

SU~ ~ JTE SHEET (RULE 26) .. . ... . .

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It is also important to note the orientation effect and overall alignment pattern created as a consequence of transvascular rnagnetic attraction. The venous catheter is shown as extending in a easternly direction such that the perforation means 98 (including the sliding electrode 114, the elevating template 110 and the fenestration 1 12) are in proper position and flanked by the pair of the rare earth magnets 1 OOa and 1 OOb. In comparison, the arterial catheter 200 lies in an westernly direction such that the arterial catheter bodyis brought into aligned position over the distal end tip 96 of the venous catheter 10; and consequently, that the grounding electrode 230 of the arterial catheter 200 is brought directly into generally parallel alignment withthe v~sc~ r wall perforation means 98 of the venous catheter 10. In this mannerl the grounding electrode 230 of the catheter then Iying within the peripheral artery becomes closeiy associated and in proper alignment with the sliding electrode 114 of the venous catheter 10 then Iying with the peripheral vein. The only intervening matter existing in-vivo is thus the thickness of the peripheral vein wall, the thickness of tissue between the closely associated vein and artery, and the thickness of the arterial wall itself.
In correctly chosen anatomic sites, the sum of these three thickness layers will typically be less than 3 mm in total distance. The sliding electrode (or other vasc~ r wall perforation means) can then be activated on-demand and at will with substantial certainty that the physical action of perforating both the venous and arterial v~scul~r walls can be achieved with minimal injury to the blood vessels and with a minimal loss of blood volume into the surrounding tissues.
It is essential to recognize and appreciate, therefore, that it is the magnetic attraction between the rare earth magnets positioned in advance and set in axial alignment within each of the venous and arterial catheters individually which creates the phenomena of transvascular magnetic attraction and interaction and which generates sufficient force such that the individual catheters Iying in adjacent blood vessels will move in axial positionas a consequence of the strength of the l"ay"elic interaction. Moreover, each catheter will move more readily with its respective vessel lumen to apply co,,,,uressive force; and in so doing, minimize the distance between the radio frequency electrode and the sliding electrode. The grounding electrode of the arterial catheter and the sliding electrode of the venous catheter are similarly aligned and set in advance within each of the respective catheters SUBSTITUTE SHEET(RULE26) . .

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such that when the transvascular magnetic attraction occurs and each of the catheters individually move into position as a consequence of magnetic attraction the vascular wall perforation means will then be in proper parallel alignment to generate an AV fistula on demand in a safe and reliable manner.

B. An ~Iternative Embodiment Of The Catheter Apparatus An alternative embodiment of the present invention provides a pair of catheters which are used in tandem for generating an AV fistula on-demand between a closely associated artery and vein at a chosen v~sc~ r site in-10 vivo. Each of the individual catheters constituting the pair are structurallysimilar except for a few detailed features.
For purposes of description and detail a single catheter of the pair will suffice. Accordingly all which pertains to the description of one catheter applies completely to the construction structure~ and features of the other 15 catheter constituting the pair. Each catheter comprises one hollow tubular wall having a fixed axial length a discrete proximal end of conventional manufacture and design a unique discrete distal end and provides two internal lumens (of unequal diameter and predetermined size) which extend coaxially and substantially in parallel over the axial length of the tubular wall.
20 Since the structural feat~res of distinction exist primarily at the distal end of each catheter this detailed disclosure will focus and emphasize these unique structures and features.
The distal end of the dual lumen catheter intended to be used in pairs for generating an AV fistula are illustrated by Figs. 13 14 and 15 25 respectively. Fig. 13 provides an overhead view of the catheter at the distalend; in comparison Fig. 14 provides an axial-section view of the cdLheter distal end while Fig. 15 provides a cross-sectional view of the catheter taken along the axis Y Y .
As shown by Figs. 13-15 each of the catheters 300 comprises a 30 tubular wall 302 which terminates at the distal end 304 as an end tip 306 adapted for p~ss~ge of a guide wire and for intravascular guidance via portals 305 and 309 and non-axisy,~ el~ic lumen 307 through a blood vessel in-vivo to a chosen v~c~ r site. Within the tubular wall 302 are two internal lumens 308 310. The first internal lumen 308 extends from the proximal end 35 of the catheter (not shown) and terminates at the distal end 304 as a portal 312. The diameter of this first internal lumen 308 is relatively large; and this SUt~g " ~ UTE SHEET (RULE 26) . .

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first internal lumen is intended to carry a variety of fluids such as liquid contrast medium for radiological purposes and pressurized gases as CO2 for displacing blood at the chosen anatomic site. The second internal lumen 310 extends from the proximal end of the catheter (not shown) as a relatively 5 small bore tube and terminates at the distal end tip 306 where a fixed electrode 320 is imbedded. The second internal lumen 310 thus serves as the conduit for an electrical lead 322 which is carried from the proximal end ofthe catheter through the catheter mass via the second internal lumen 310 and ends at the distal end tip 306 at the embedded electrode 320.
Note that the fixed electrode 320 is joined to the electrical lead 322 which is in electrical communication with a source of electrical energy (not shown) capable of producing a static electrical charge on command. The electrode 320 is typically formed of solid, electrically conductive metal. The electrode 320 comprises at least two component parts: an electrical supporting unit 324 which is embedded in the material of the catheter wall and firmly fixed in position within the catheter mass; and an extending discharge spike 326 which extends from the support unit 324 through the thickness of the catheter wall material and terminates in the ambient environment. As an electrical system, a static discharge from the electrical source is introduced through the catheter via the electrical lead 322 and conveyed to the electrode 320 on demand. The electrical current is conveyed to the supporting unit 324 and the charge is then discharged through the spike 326 from the interior of the catheter into the external ambient environment as a static electrical spark of predetermined magnitude.
Positioned adjacent to the electrode 320 and set in fixed aliyn",en~ at the distal end tip 306 is a rare earth magnet 330 (or, alternatively, other magnet means). This rare earth magnet is configured desirably as a rectangular block of magnetic metal formed of neodymium-iron-boron alloy and/or cobalt-samarium alloy. Note also that the orientation of the magnetic attraction in terms of the "north" and "south" polarity is known and identifiable. The rare earth magnet thus serves as magnet means positioned at the distal end and set in axial alignment at the distal tip of the catheter. In addition, an optional second rare earth magnet 332 may be set in fixed alignment to flank the electrode 320. The optional second rare earth magnet 332 is desirably identical in configuration and composition to the magnet 330;
and provide added ma~nelic force for alignment. These magnet means have SUBSTITUTE SHEET (RULE 26) CA 02249237 1998-09-1~

sufficient attractive force to cause an adjustment in position for the catheter in-vivo when placed in proximity with another source of magnetic attraction disposed within a closely associated (and preferably adjacently positioned) blood vessel.
In comparison it will be recognized that the electrical lead 322, the electrode 320, the supporting unit 324 and the discharge spike 326 collectively constitute the vascular wall perforation means for this embodiment. Note that the entire electrical current carrying and spike discharge apparatus cons~iluting the vascular wall perforation means are 10 positioned adjacent to at least one rare earth magnet (the magnet means) of the catheter and are set in axial aliyl ,,,,e, IL with the distal end tip of thecatheter. Thus, when there is a magnetic interaction involving the rare earth magnet 330 (and optionally the rare earth magnet 332), this static electrical system will become intravascularly adjusted in position in-vivo; and the static 15 discharge will serve as the means for peT Forating the vascular walls at willwhenever sufficient potential is applied to the two electrodes to generate an AV fistula.
The intended manner of usage under in-vivo conditions is illustrated by Fig. 16. For purposes of clarity the first catheter 300a is presumed to be in a peripheral vein whereas the second catheter of the pair 3û0b is envisioned as being within a peripheral artery. The vascular walls have been deleted from the figure to demonstrate the working relationship between the two catheters in tandem and the mechanism by which an AV fistula is generated using this catheter a~paral.Js.
As shown by Fig. 16, the only difference between the first catheter 300a and the second catheter 300b is the polarity and polar orientation of the rare earth magnets 330a, 330b (and optionally rare earth magnets 332a, 332b). Recalling also that each catheter has been placed within the confines of an individual blood vessel constituting a closely associated peripheral artery and vein, it is clear that the opposite polarity in each rare earth magnet will attract the catheters towards each other. Thus, a transvascular magnetic attraction occurs which not only moves each of the catheters 300a, 300b individually within its own blood vessel in a manner which brings the pair closely together, but also the strength of the magnetic attraction is sufficiently great in power (Gauss) that the rare earth magnets are drawn and aligned to each other in parallel positions as shown within Fig. 16. The consequence of Sl,~S 111 UTE SHEET (RULE Z6) .... . . . . ...

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W 097/33522 PCTrUS97tO2800 this transvascular magnetic attraction and alignment in parallel between individual catheters disposed in separate blood vessels independently causes the electrodes 320a, 320b and the discharge spikes 326a, 326b to become closely placed and aligned in parallel. It is also desirable in practice 5 to ascertain that adequate alignment by magnetic attraction has occurred and that a suitably small distance occurs between the individual discharge spikes by measuring the electrical resistance between the electrical contacts 320a, 320b. Fluoroscopy cor~rilll's appropriate catheter position, alignment, and polar (rotational) orientation.
After the determination of adequate alignment is made, the source of static electrical discharge is engaged, and the electrical charge is conveyed to the electrode discharge spikes. A static electrical charge is accumulated, discharged and passed from one of the spikes 326a to the other aligned spike 326b, thereby completing the electrical circuit. In so completing this 15 electrical circuit, the electrical spark vaporizes portions of the vascular wall for both the vein and the artery at the same moment. The arcing spark vaporizes v~scu~q~ tissue and creates a perforation in co~ on between the blood vessels. Blood in the artery rushes through the perforation in the arterial wall into the aligned hole of the perforation in the vascular wall of the 20 ~ cently positioned vein. In this manner, the AV fistula is generated safely, reliably, and on-demand.
It will be noted and appreciated that this alternative embodiment of the catheter apparatus can also employ other v~sc~ r wall perforation means than a static electrical discharge to perforate the v~scu lar wall. An immediate25 and easily available substitution and replacement for the entire electrical lead, elecll ude, and dischar~e spike - the pel roralion means - is the use of afiber optic cable and a source of laser (light) energy. The fiber optic cable (comprised of multiple fiber optic strands) is conveyed through the internal lumen and passes through the tubular wall material of the catheter at the 30 distal end tip to terminate as a fiber optic end surface exposed to the ambient environment. The fiber optic cable would then (~ ~nsr"il and convey laser ~light) energy from the energy source on-demand as the means for pe, rorali"g the vascular wall of the closely associated blood vessels. Also, the catheter Iying in the adjacent blood vessel would serve to diffuse the 35 applied laser energy and prevent injury to the opposite v~su II:lr wall.

SUBSTITUTE SHEET (RULE 26) , .. " . ........ . . ......... ..

CA 02249237 1998-09-1C, WO 97/33~;22 PCT/US97/02800 V. An Illustrative Method For Creating An AV Fistula In-Vivo ~Ising The Preferred Embodiment To demonstrate the methodology employing a catheter apparatus to generate an AV fistula between a peripheral artery and an adjacent vein, it is 5 desirable to focus upon and utilize a specific anatomical area in the extremities of a living patient as an illustrative example. For this illustrative purpose alone, the description presented hereinafter will emphasize and be limited to the creation of an AV fistula between the radial or ulnar arteries and a closely associated and adjacently positioned vein in the distal forearm. It 10 will be expressly understood and recognized, however, that this illustrative description is merely representative of such procedures generally; and is but one example of the many different and diverse instances of use which can be reproduced in many other anatomical areas of the body at will and on-demand. Under no circumstances, therefore, is the present invention and 15 methodology to be or restricted to the particular anatomic sites described orlimited to the particular embodiment of the catheter apparatus employed.
The illustrative example presented below employs the preferred embodiment of the catheter apparatus described in detail previously herein.
Clearly, although this preferred embodiment is deemed to be an 20 advanta~eo~ ~s construction and the best mode structure developed to date, all other alternative embodiments of the catheter apparatus - regardless if used singly or in pairs - are also deemed to be suitable and appropriate for use in a manner similar to that described below. In addition, given the wide range and diversity of structural components, design features and format 25 variations in catheter construction which have already been disclosed herein and are within the scope and breadth of the present invention, it will be understood that certain minor changes in the procedural details and modes of use may be necessary which differ from the preferred methodology.
Initially, and most importantly, it will be recognized and appreciated 30 that the methodology is intended to be performed in the angiography suite of a hospital by thoroughly trained and experienced invasive radiologists. The reader is presumed to be familiar with the common procedures performed by invasive radiologists today; and no allen~pt will be made herein to familiarize or ~c~u~int the reader with the conventional techniques of ultrasound 35 imaging, fluoroscopy and fluoroscopic imaging, and other radiological techniques for contrast imaging. The reader is also presumed to be familiar S~ JTE SHEET (RULE 26) CA 02249237 1998-09-1~

with general procedures of catheterization and especially with the modified Seldinger technique reviewed in detail previously herein Finally, to aid the reader in becoming acquainted with the essence of the methodology and in order to appreciate its importance an~ major advantages, Figs. 17-26 are 5 included; and direct reference and comparison of these figures will aid in ease of understanding and full comprehension of the methodological details.
The first step in the methodology involves obtaining percutaneous arterial access to a suitable peripheral artery (such as the radial or ulnar arteries) in the forearm through the brachial artery or, less desirably, the 10 common femoral artery. An introducer sheath is placed into the brachial artery using conventional techniques described extensively in the medical literature. The sheath is placed at mid-bicep and directed distally towards the hand. An intravascular ultrasound probe (hereinafter "IVU") is then introduced over a guidewire into the forearm arterial blood vessels. This is 15 shown by Fig. 17 which shows the intravascular ultrasound probe being passed antegrade into the radial artery.
The IVU provides circumferential ultrasonic visualization of structures in the immediate vicinity of the artery in which it is positioned as is illustrated by Fig. 1~. As shown, Fig. 18 clearly de",o"sl,~les two large veins ("V") 20 immediately ~Jj~ce"l to the radial artery ("A") at the position shown by Fig.17. Veins in the forearm that lie in close proximity to the radial artery are readily identified. The echolucent blood in the veins stands out in sharp contrast to the relatively echogenic fibrous and fatty tissues and muscle which surrounds the veins themselves. Desirably, the IVU is passed through 25 both the radial and ulnar arteries independently and in sl Iccession in order to note the location and position of those large diameter veins Iying immediately adjacent to the artery. Commonly, several anatomical zones are present in the forearm of most patients where large diameter veins pass within one or two millimeters of these major peripheral arteries. From among these 30 anatomical zones, one of these is selected for the generation of the AV
fistula. Ideally, the chosen anatomical area should be fairly distal or peripheral in the forearm, as this will result in a greater number of veins being exposed to high volume flow and thus a greater number of potential ~ccess sites for percutaneous venipuncture. Bec~use veins have uni-directional 35 valves in them, veins distal to the AV fistula will not generally dilate.

SUBSTITUTE SHEET(RULE26) .... ..

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W O 97/33522 PCTrUS97/02800 This result is illustrated by Fig. 19 where the anatomic area is selected in the distal radial artery in the location where a sizable diameter vein lies immediately adjacent to the arterial wall. The chosen anatomic site is shown by the intravascular ultrasound image of Fig. 20 which reveals an adjacently positioned vein on one side of the radial artery lumen.
The second step is to obtain venous access for the venous catheter which takes form initially as the cylinder-obturator composite described previously herein. Percutaneous venous aGcess is desirably obtained at the wrist. Fluoroscopic contrast venoyra,t hy is performed to define forearrrl 10 venous anatomy. Under fluoroscopic guidance, a radiological guide wire is advanced through the percutaneous venous ~ccess to the chosen vein at the anatomic zone selected for generating the AV fistula in the forearm. The techniques required for this maneuver are conventional and fundamental to the practice of invasive radiology. This procedure is illustrated by Figs. 21 15 and 22 respectively. Fluoroscopy shows the guidewire to be in close proximity to the IVU probe. In addition, as shown by Fig. 22, the extremely echogenic guidewire is easily visualized and imaged within the chosen vein lumen by IVU imaging. In this manner, the proper placement of the venous catheter in the chosen vein is inserted.
As shown by Fig. 21, the preferred venous cylinder-obturator composite 10 is introduced at the wrist and passed antegrade into the chosen vein over the previously placed guidewire. Fluorosco~Jy and intravenous contrast medium assist extension and guidance of the venous catheter through the vein; and a correct position is identified and placement confirmed for the venous catheter at the chosen site in the vein. Once again, IVU
readily demonstrates the venous catheter within the lumen of a chosen vein.
It will be recalled that the venous catheter (the introducer cylinder-obturator composite format) measures 6-9 French (approximately 2-3mm) in diameter; and typically will be about 40 centimeters in length. At the proximal end, the radiologist uses a handle to manipulate the venous catheter during placement. The venous catheter clesirably employs the removable solid obturator during this phase in order to facilitate advancement of the venous catheter complex, pr~ferably as described previously, the obturator has about a 0.2-0.5 mm internal lumen which extends coaxially down its central axis and allows the venous catheter complex to be passed coaxially over the guidewire SUBSTITUTE SHEET (RULE 26) . ~ . . .

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into the proper position after the guidewire placement has been verified as correct.
Once good positioning and placement is verified and confirmed for the venous catheter (the introducer cylinder-obturator composite format), the IVU
probe is removed and replaced with the arterial catheter 200 described previously herein. The construction of the arterial catheter provides substantial flexibility and offers a much longer axial length than its venous counterpart. Typically, the arterial catheter has an external diameter of about 5-7 French (approximately 1.5-2 mm in diameter) and has a typical length of 1 Q about 100 centimeters to facilitate placement in an accessible artery.
However, passing the positioned guidewire internally through the entire 1 û0 cm length of catheter can be cumbersome and difficult. For this reason, the arterial catheter (much like the IVU probe) typically has a short-length, non-axisymmetric passageway or lumen which extends from the center of the distal end tip tangentially for about 1 cm distance and ends at the sidewall of the catheter about 1 centimeter from the distal end. This short non-axisymmetric lumen provides an externalized "monorail" mode of p~ss~ge for the guidewire after insertion at the distal end tip; and allows the arterial catheter to be passed over the properly position guidewire without need for internally passing the guidewire through the entire axial length of the catheter. This "monorail" mode of externalized guidewire p~ss~ge through a catheter is conventionally known, facilitates proper placement~ and offers better control of the catheter for the radiologist when positioning the arterialcatheter in-vivo.
The manipulation and introduction of the arterial cdLI ,eter is illusll dled by Figs. 23 and 24 respectively. As shown by Fig. 23, after the intravascular ultrasound probe has been removed, the arterial cdll ,e~er is passed over the previously positioned guidewire, introduced into the artery, and advanced to the chosen anatomical site previously held by the IVU probe, Moreover, as illuslldled by Fig. 24, fluorusco,uy reveals when good and proper alig""~el1l exists between the positionings of the arterial cdll ,eter in relation to the venous call)eler in the closely associated vein. Thus, under the fluoroscopic guidance, the arterial catheter is advanced over the guidewire into the radial artery to the chosen position previously occupied by the IVU probe.
After ascertaining that close proximity of the arterial catheter to the venous catheter exists, the relative positions are carefully adjusted under Sl,~ 1 l l ~ITE SHEET (RULE 26) .. .. .. . .... .. ..

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W O 97/33522 PCT~US97/02800 fluoroscopy such that the radiopaque markers on each of the catheters are carefully in alignment. In addition, radial radiopaque markers on the introducer cylinder allow rotational position to be adjusted fluoroscopically toinsure correct orientation o~ the distal fenestration. Thus, when correctly 5 aligned, the two catheters ~each within its individual blood vessel) will overlap for an estimated distance of about 35mm. If the overlapping distance does not appear to be adequate or if the radiologist is unsure that the two catheter tips are properly aligned, each of the catheters may be adjusted in position as long as needed in order to verify and conrir~n a proper alignmenl.
When, and only when, a correct and proper alignment has been made between the arterial and venous catheters in-vivo, the obturator co~ponent is removed from the venous introducer cylinder and replaced with the tubular cutting tool previously described. The tubular cutting tool is a semi-rigid rod with the same dimensions as the obturator and comprises the pair of rare 15 earth magnets having the proper size and orientation to attract the rare earth magnets within the arterial catheter distal end. The magnetic attractive force will cause a transvascular attraction between the two opposing pairs of rare earth magnets; and the magnetic all, a~ e force is of sufficient magnitude such that the arterial catheter and the venous call ,eter will adjust in position 20 individually as a result and consequence of the magnetic interaction. This event and effect is illustrated by Fig. 25 in which the arterial catheter Iying within the radial artery moves into proper alignment and precise positioning as a result of the magnetic interaction with the ",agnet means of the venous catheter Iying within the ~ cent vein. After this transvascular magnetic 25 attraction and adjustment in position between the two catheters has occurred,the vascular wall perforation means at the distal end of the venous catheter may be activated at will and on-demand to generate the AV fistula at that precise location.
The preferred embodiment of the venous c~ll ,eter 10 employed utilizes 30 a radiofrequency elecLrode which slides in a controlled track upon a elevating template and which becomes exposed through a fenestration as a result of traveling over the template track. The sliding electrode is ~tu~ted by way of a sliding wire running the length of the tubular cutting tool; and the actuationwire is engaged preferably by a screw mechanism in the handle at the 35 proximal end held by the radiologist. Once Actll~ted, the electrode is moved along the curvilinear track on the elevating template resulting in the SUBSTITUTE SHEET (RULE 26) .. . . ............................... .
, .. . . ..

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protrusion of the electrode through the fenestration into the exterior of the venous catheter. Simultaneously, radiofrequency current is delivered to the sliding electrode by way of the conductive actuation wire; and the grounding electrode in the arterial catheter completes the electrical circuit for vascular5 perforation to proceed. The degree of electrode protrusion from the venous catheter is such that the sliding electrode impinges on the material of the grounding electrode of the arterial catheter which is in aligned parallel position directly adjace~ It to the venous catheter. This circumstance is illustrated by Fig. 26.
In this manner, the protruding sliding electrode of the venous catheter can be moved up to 8 mm axially depending on the desired length of the incision; and the grounding electrode of the arterial catheter completes the radiofrequency electrical circuit (as shown by Fig. 26). By completing the radiofrequency electrical circuit at the chosen anatomic site and delivering 15 the appropriate current to the completed circuit, a direct and effective perforation of the venous v~.scul~r wall and the arterial v~scul~r wall concurrently can be achieved on-demand.
Simultaneous with the delivery of radiofrequency electrical energy to the completed circuit, a bolus of col"pressed carbon dioxide gas is 20 introduced into the lumens of both the artery and the immediately adjacent vein. The CO2 gas transiently displaces the blood at the chosen anatomic site during the process of perforating both v~su ~l~r walls. Since blood is an electrically conductive medium, the CO2 gas displacement increases the current density at the point of contact between the radiofrequency electrode 25 and the vascular wall and facilitates the pe~ roralion of both v~scul~r wallsconcurrently, while minimizing the quantity of tissue destruction that results.
Carbon dioxide is extremely soluble and therefore does not result in gas embolism. It has been previously shown (experimentally and clinically) that large volumes of compressed CO2 gas can be introduced intravenously and 30 intraarterially without incurring harmful effects in-vivo.
After the vascular wall perforation process has been saLisrdcLorily completed and the AV fistula created at the chosen anatomic site, the radiofrequency current is disrupted; and the sliding electrode is disengaged and withdrawn into the protective interior of the venous calheter. The venous 35 cutting tool is then withdrawn 2-5 mm proximally relative to the venous cylinder component while holding the arterial catheter steady in its prior SUBSTITUTE SHEET (RULE 26) .,, CA 02249237 1998-09-1~

position within the artery. This act of withdrawing the venous cutting tool fromthe cylinder causes the transvascular magnetic attraction to be broken while the arterial catheter is maintained unchanged in its prior aligned position at the perforation site. Radiopaque contrast medium can then be injected into the artery via the internal lumen of the arterial catheter; and the AV fistula assessed fluoroscopically. Evidence of extravasation at the fistula site can therefore be ruled out as well.
The result of this methodology and procedure is the generation of an AV fistula on-demand between closely associated arteries and veins at a 10 carefully chosen and verified v~scular anatomical site in-vivo. The radiologist can halt the sequence of steps at any time prior to activating the v~sc~ r wall perforation means (the radiofrequency electrode circuitry in this preferred embodiment) without risk or hazard to the patient or the peripheral blood circulation in any substantial manner. Moreover, the methodology allows the 15 radiologist to repeatedly assess, verify, and confirm his choices of anatomical site location; note the alignment and positioning of the arterial catheter as well as the alignment orientation and positioning of the venous call ,eler, and achieve the proper result and consequence of transvascular magnetic attraction which results in changes in position for one or both of the cathetersin-vivo - all which occur prior to engaging the means for physically pel roraling the v~su ~ r walls and generating an aperture between the artery and the adjacently positioned vein.

Vl. Illustrative Applications And Usages A number of intended applications and exemplary I Is~ges are briefly described below. Each of these is merely one representative insla~ ~ce of use for the present invention; and many other applications exist presently where the catheter ap~,~aralus can be adva~ ~lageously employed for the benefit of thepatient.
A. Hemodialysis Access A major advantage of the PAVFC te-,hnique is the avoidance of a surgical procedure. As stated earlier, renal failure patients have impaired would healing, and an increased incidence of wound infections. In addition, renal failure is associated with modest degrees of immunosuppression. As such, wound infections can lead readily to sepsis and potentially fatal SUBSTITUTE SHEET (RULE 26) ...... . . . . .. .. . ..... .. .

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complications. A technique that permits creation of hemodialysis access without necessitating an incision is very attractive. In addition, the procedurewould not require an anesthetic and anesthesiologist, or operating room time and personnel, and could therefore be performed at lower cost.
For reasons discussed earlier, a fistula is preferred over a prosthetic arteriovenous shunt. Unfortunately, however, surgical ~ccess is often limited to the distal radial artery, and often, there is not a vein of sufficient size in this area. The PAVFC technique allows fistula formation in areas where surgical exposure would be problematic. As such, there are more potential sites available. This allows a more ideal fistula to be created, without the risk of venous kinking.
The PAVFC technique allows evaluation of the juxta arterial venous system of the entire extremity by intravascular ultrasound to identify the most favorable anatomic site and provides accurate ~ssessment of venous diameter. Veins on which surgical anastomosis would be difficult due to small size or thin walls are easily addressed and utilized by the PAVFC. More importantly, the vessels are not rlissected out or manipulated, preserving the tenuous vaso vasorum, which will improve patency.
Potential problems with this technique are few, and relate primarily to the risk of hemorrhage. If an anatomically favorable site is selected, this riskwill be quite small. In the event of helno"hage, an expanding hematolna in the arm is clinically obvious, and is readily controlled with the direct pressure using a blood pressure cuff or manual compression. It may prove necess~ry to surgically explore patients in whom compression proves inadequ~te. The risk of using intravenous conl~ asl to facilitate fluoroscopic visualization of arm venous anatomy is small, as is the risk of inl,aa~ lerial contrasts to assist adequacy of the AV fistula post-procedure.

B. Portal Venous Hypertension And Veno-Venous Fistulae Portal venous hy~uel lerlsion develops as a complication of end stage cirrhosis, and other forms of liver ~isease. The portal veins drain from the intestine to the liver. The blood is filtered through the liver before entering the systemic venous system, and returning to the heart. When the liver becomes badly diseased, resistance to portal venous flow increases. The filter mechanism becomes "clogged". As a result, the pressure in the portal SUBSTITUTE SHEET (RULE 26) CA 02249237 1998-09-1~

WO 97/33522 PCT/US97tO2800 venous systemic increases, which results in massive dilation of the naturally occurring portal-systemic venous connections.
One such area of portal-systemic venous connection is at the gastroesophageal junction (near the top of the stomach). These thin walled, 5 massively dilated veins often rupture spontaneously, resulting in exsanguinating upper gastrointestinal hemorrhage, which is frequently lethal.
Surgical therapy is directed at lowering the portal venous pressure by creating a shunt between the portal vein or it's major branches, and the systemic venous system, usually the inferior vena cava. The operation is 10 effective in lowering portal venous pressure in most patients, and usually prevents additional bleeding episodes. The procedure is, however, quite risky. Patients with advanced liver disease tolerate surgery poorly, with reported operative mortality of 10%, 50%, and 80% for portalcaval bypass in patients with early, intermediate, and late stage liver failure, respectively.
Percutaneous creation of portal-systemic connection has been performed at many institutions with some s~lccess. The current technique, however, does not permit identification of closely adjacent portal and systemic veins, does not utilize magnetic attraction to bring the adjacent veins into close proximity, and does not utilize radiur, eq~ ency current, laser20 energy, or static discha~ge to create the connection. Each of these modification of the current percutaneous technique represents a major technical advance, and will result in a larger portosystemic connection, and better portal venous deco""~ression. As such, the PAVFC catheter and technique is extremely useful in this field. One catheter is introduced via the 25 femoral or jugular vein and is advanced into the inferior vena cava to the level of the portal vein. The second calheter is introduced into the portal venous system by way of percutaneous transhepatic puncture or by transjugul~r-hepatic approach. Proximity of the two catheters is achieved with intravascular ultrasound and fluoroscopy, as described for dialysis access. A
30 variety of veno-venous fistulae can be generated in this manner.

C. Creation of Graft Material The PAVFC catheters and technique are useful in the creation of suitable conduit, or graft material, in anticipation of subsequent Minimally 35 Invasive Coronary Artery Bypass Grafting (MICABG). MICABG is a rapidly SUBSTITUTE SHEET (RULE 26) ... . . ..

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W O 97/33522 PCT~US97102800 evolving technique that allows blocked coronary arteries to be bypassed without necessitating cardiopulmonary bypass or cardiac arrest.
Traditionally, when a patient develops critical narrowing of the coronary arteries not amenable to medical management or angioplasty, a 5 conventional coronary artery bypass is performed. The patient's chest is opened, and the heart attached to the heart lung machine by way of large cannula inserted in the aorta and right atrium. The heart lung machine pumps and oxygenates the blood, enabling the surgeon to temporarily arrest the heart by mechanical and pharmacological means, without interrupting 10 blood flow to the brain, kidneys, and other vital organs. A clamp is placed on the ascending aorta, which deprives the heart of blood and results in cessation of cardiac activity. The clamp also allows the proximal ends of segments of saphenous vein, harvested from the patient's leg, to be attached to the aorta in a blood free environment. The distal ends of the vein grafts 15 are attached to the coro"aly arteries beyond the areas of critical narrowing.Some coronary arteries are bypassed with the left or right internal mammary arteries. Long term patency of mammary grafts is much better than that seen with vein grafts. In addition, no proximal anastomosis is necess~ry as the mammary arteries are already brancl-es of the arterial tree, and tl ,erefore 20 carry arterial flow despite leaving the proximal artery in situ. The crossclamp is then removed, and blood flow restored to the heart.
MICABG is a new method of surgical revascularization that has the potential of being less risky than conventional bypass. Most, if not all, of themorbidity associated with conventional coronary artery bypass is related to 25 cardiopulmonary bypass and temporary cardiac arrest. The MICABG
technique allows the surgeon to graft the coro"ary arteries without necessitating these maneuvers. MICABG is not without limitations, however.
With this technique, the heart continues to beat, and eject blood at high pressure and flow through the ascending aorta. As such, it is not currently 30 possible to attach vein grafts to the aorta. All gra~liny must therefore b performed with arteries as they do not require proximal anastomosis.
Thoracic arteries suitable for use as grafts are, unfortunately, in short supply.
Only the left and right internal mammaries are of adequate diameter and length to be of use. The gastroepiploic artery can be used for grafting, but 35 requires a laparoto",y for harvest, and is technically more demanding SU~ UTE SHEET (RULE 26) CA 02249237 1998-09-1~

The PAVFC catheters and techni~ue are of use in patients undergoing MICABG. Each of the 12 paired ribs has closely associated with it a neurovascular bundle. This bundle contains a sensory nerve, an artery, and a closely associated vein. The artery measures only 1 to 1.5 mm in diameter, 5 and as such, is of inadequate diameter to be used as a graR. If. however, a fistula is created between the distal intercostal artery and vein. both thin walled vessels will dilate with time. This dilation of intercostal arteries fromincreased flow is observed clinically in patients with coarctation of the aorta.Patients electively scheduled to undergo MICABG could have distal 10 intercostal fistulas created in one or more of the larger intercostal arteries with the PAVFC technique, approximately, 6 weeks prior to anticipated heart surgery. The enlarged artery could then be mobilized, brought medial to the lung, and used as an arterial graft, in a manner identical to that used for the left and right internal mammary arteries.
The present invention is not to be restricted in form nor limited in scope except by the claims appended hereto.

SU~ 1 l l UTE SHEET (RULE 26)

Claims (8)

What we claim is:

1. A catheter apparatus for generating a fistula on-demand between closely associated blood vessels at a chosen anatomic site in-vivo, said catheter apparatus being suitable for percutaneous introduction into and extension through a blood vessel and comprising:
(a) a tube having a fixed axial length, a discrete proximal end, a discrete distal end, and at least one internal lumen of predetermined volume, (b) a distal end tip adapted for intravascular guidance of said tube through a blood vessel in-vivo to a chosen anatomic site, (c) magnet means positioned at said discrete distal end and set in axial alignment with said distal end tip of said tube, said magnet means having sufficient magnetic force to cause an adjustment in position for said tube when in proximity with an a source of magnetic attraction disposed within another closely associated blood vessel, (d) vascular wall perforation means positioned at said discrete distal end adjacent to said magnet means and set in axial alignment with said distal end tip of said tube, said vascular wall perforation means becoming adjusted in position via the magnetic force of said magnet means when in proximity with the a source of magnetic attraction disposed within a closely associated blood vessel in-vivo, (e) means for activating said vascular wall perforation means of said tube on-demand wherein said vascular wall perforation means perforates the chosen anatomic site to generate a fistula in-vivo between the closely associated blood vessels.

2. A catheter apparatus for generating an arteriovenous fistula on- demand between a closely associated artery and vein at a chosen anatomic site in-vivo, said catheter apparatus comprising:
a pair of catheters suitable for individual percutaneous introduction into and extension through a blood vessel wherein at least one of said catheters is comprised of (a) a tube having a fixed axial length, a discrete proximal end, a discrete distal end, and at least one internal lumen of predetermined volume, (b) a distal end tip adapted for intravascular guidance of said tube through a blood vessel in-vivo to a chosen anatomic site.
(c) magnet means positioned at said discrete distal end and set in axial alignment with said distal end tip of said tube, said magnet means having sufficient magnetic force to cause an adjustment in position for said tube when in proximity with a source of magnetic attraction disposed within another closely associated blood vessel, (d) vascular wall perforation means positioned at said discrete distal end adjacent to said magnet means and set in axial alignment with said distal end tip of said tube, said vascular wall perforation means becoming adjusted in position via the magnetic force of said magnet means when in proximity with a source of magnetic attraction disposed within a closely associated blood vessel in-vivo, and (e) means for activating said vascular wall perforation means of said catheter on-demand wherein said vascular wall perforation means perforates the chosen anatomic site to generate an arteriovenous fistula in-vivo between the closely associated blood vessels.

3. A catheter apparatus for generating an arteriovenous fistula on-demand between a closely associated artery and vein at a chosen anatomic site in-vivo, said catheter apparatus comprising:
a first catheter suitable for percutaneous introduction into and extension through a vein in-vivo to a chosen anatomic site, said first catheter being comprised of (a) a first tube having a fixed axial length, a discrete proximal end, a discrete distal end, and at least one internal lumen of predetermined volume, (b) a distal end tip adapted for intravascular guidance of said first tube through a vein in-vivo to a chosen vascular site, (c) first magnet means positioned at said discrete distal end and set in axial alignment with said distal end tip of said first tube, said first magnet means having sufficient magnetic force to cause an intravascular adjustment in position for said first catheter when in proximity with a source of magnetic attraction in-vivo, and (d) a first component of vascular wall perforation means positioned at said discrete distal end adjacent to said first magnet means and set in axial alignment with said distal end tip of said first tube, said first component of vascular wall perforation means becoming intravascularly adjusted in position the magnetic force of said first magnet means of said firstcatheter when in proximity with a source of magnetic attraction in-vivo, (e) means for activating said first component of vascular wall perforation means of said first catheter on-demand wherein said vascular wall perforation means perforate the chosen anatomic site to generate an arteriovenous fistula in-vivo; and a second catheter suitable for percutaneous introduction into and extension through an artery in-vivo to a chosen anatomic site, said second catheter being comprised of (a) a second tube having a fixed axial length, a discrete proximal end, a discrete distal end, and at least one internal lumen of predetermined volume, (b) a distal end tip adapted for intravascular guidance of said second tube through an artery in-vivo to a chosen anatomic site, (c) second magnet means positioned at said discrete distal end and set in axial alignment with said distal end tip of said second tube, said second magnet means having source of sufficient magnetic force to cause an intravascular adjustment in position for said second catheter when in magnetic proximity with said first magnetic means of said first catheter in-vivo, (d) a second component of vascular wall abutment means positioned at said discrete distal end adjacent to said second magnet means and set in axial alignment with said distal end tip of said second tube, said second component of vascular wall perforation means becoming intravascularly adjusted in position via the magnetic force of said second magnet means of said second catheter in-vivo.

4. The catheter apparatus as recited in claim 1, 2, or 3 wherein said magnet means comprises at least one rare earth magnet.

5. The catheter apparatus as recited in claim 1, 2, or 3 wherein said magnet means comprises at least one electromagnet.

6. The catheter apparatus as recited in claim 1, 2, or 3 wherein said vascular well perforation means is selected from the group consisting of radiofrequency electric circuitry means, static electricity discharge means, mechanical cutting means, and laser light energy carrying means.

7. A catheterization method for generating a fistula on-demand between closely associated blood vessels at a chosen anatomic site in-vivo, said catheterization method comprising the steps of:
procuring at least one catheter suitable for percutaneous introduction into and extension through a blood vessel in-vivo to a chosen anatomic site, said catheter being comprised of (a) a tube having a fixed axial length, a discrete proximal end, a discrete distal end, and at least one internal lumen of predetermined volume, (b) a distal end tip adapted for intravascular guidance of said tube through a blood vessel in-vivo to a chosen anatomic site, (c) magnet means positioned at said discrete distal end and set in axial alignment with said distal end tip of said tube, said magnet means having sufficient magnetic force to cause an intravascular adjustment in position for said catheter when in proximity with a source of magnetic attraction disposed within a closely associated blood vessel in-vivo, (d) vascular wall perforation means positioned at said discrete distal end adjacent to said magnet means and set in axial alignment with said distal end tip of said tube, said vascular wall perforation means becoming intravascularly adjusted in position via the magnetic force of said magnet means when in proximity with a source of magnetic attraction disposed within a closely associated blood vessel in-vivo, (e) means for activating said vascular wall perforation means of said catheter on-demand wherein said vascular wall perforation means perforates a chosen anatomic site between closely associated blood vessels;
percutaneously introducing said catheter into a first blood vessel and extending said catheter intravascularly to a chosen site adjacent to a closely associated second blood vessel;
percutaneously introducing a source of magnetic attraction into a closely associated second blood vessel and extending said source of magnetic attraction intravascularly to a chosen anatomic site in proximity to said extended catheter;
permitting a transvascular magnetic attraction to occur between said magnet means of said extended catheter in the first blood vessel and said source of magnetic attraction in the closely associated second blood vessel whereby said vascular wall perforation means of said catheter in the first blood vessel comes into transvascular alignment with the closely associated second blood vessel at the chosen anatomic site, and then activating said vascular wall perforation means of said catheter on-demand wherein said vascular wall perforation means perforate of said catheter the vascular walls of said closely associated blood vessels concurrently at the chosen anatomic site to generate a fistula in-vivo.

8. A catheterization method for generating an arteriovenous fistula on-demand between a closely associated artery and vein at a chosen anatomic site in-vivo, said catheterization method comprising the steps of:
procuring a first catheter suitable for percutaneous introduction into and extension through a vein in-vivo to a chosen anatomic site, said first catheter being comprised of (a) a first tube having a fixed axial length, a discrete proximal end, a discrete distal end, and at least one internal lumen of predetermined volume, (b) a distal end tip adapted for intravascular guidance of said first tube through a vein in-vivo to a chosen anatomic site, (c) first magnet means positioned at said discrete distal end and set in axial alignment with said distal end tip of said first tube, said first magnet means having sufficient magnetic force to cause an intravascular adjustment in position for said first catheter when in proximity with a source of magnetic attraction in-vivo, and (d) a first component of vascular wall perforation means positioned at said discrete distal end adjacent to said first magnet means and set in axial alignment with said distal end tip of said first tube, said first component of vascular wall perforation means becoming intravascularly adjusted in position via the magnetic force of said first magnetic means of said first catheter in-vivo, (e) means for activating said first component of vascular wall perforation means of said first catheter on-demand wherein said vascular wall perforation means perforates a chosen anatomic site to generate a fistula in-vivo;
percutaneously introducing said first catheter into a vein and extending said first catheter intravascularly to a chosen anatomic site adjacent to a closely associated artery;
procuring a second catheter suitable for percutaneous introduction into and extension through an artery in-vivo to a chosen anatomic site, said second catheter being comprised of (a) a second tube having a fixed axial length, a discrete proximal end, a discrete distal end, and at least one internal lumen of predetermined volume, (b) a distal end tip adapted for intravascular guidance of said second tube through an artery in-vivo to a chosen anatomic site, (c) second magnet means positioned at said discrete distal end and set in axial alignment with said distal end tip of said second tube, said second magnet means having sufficient magnetic force to cause an intravascular adjustment in position for said second catheter when in proximity with said first magnetic means of said first catheter in-vivo, (d) a second component of vascular wall abutment means positioned at said discrete distal end adjacent to said second magnet means and set in axial alignment with said distal end tip of said second tube, said second component of vascular wall perforation means becoming intravascularly adjusted in position via the magnetic force of said second magnet means of said second catheter in-vivo;
percutaneously introducing said second catheter into an artery and extending said second catheter intravascularly to a chosen anatomic site in proximity to said first catheter in to a closely associated vein;
permitting a transvascular magnetic attraction to occur between said first magnetic means of said extended first catheter in the vein and said second magnetic means of said extended second catheter in the closely associated artery whereby said first component of vascular wall perforation means of said first catheter lying within the vein comes into transvascular alignment with said second component of vascular wall abutment means of said second catheter lying within the artery; and then activating said first component of vascular wall perforation means of said first catheter on-demand wherein said vascular wall perforation means perforate the vascular walls of said vein and closely associated artery concurrently at the chosen anatomic site to generate an arteriovenous fistula in-vivo.