CA1309468C

CA1309468C - Cardioverting method and apparatus utilizing catheter and patch electrodes

Info

Publication number: CA1309468C
Application number: CA000522448A
Authority: CA
Inventors: Marlin Steve Heilman; Stanley Monrad Bach Jr.
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-11-07
Filing date: 1986-11-07
Publication date: 1992-10-27
Anticipated expiration: 2009-10-27
Also published as: GB8626681D0; NL8602828A; GB2182852B; FR2589740A1; DE3637822A1; JPS62117569A; US4662377A; FR2589740B1; GB2182852A; NL191082C; JPH0370981B2

Abstract

Abstract of the Disclosure A novel electrode apparatus and method for use with an automatic implantable cardioverter/defibrillator. The electrode apparatus includes a catheter electrode intravenously postioned within the heart of a patient wherein one electrode, defined by the catheter, is within the right ventricle and a second elec-trode, defined by the catheter, spaced from the first electrode, is within the superior vena cava. A third electrode, in the form of a flexible, substantially planar patch, is subcutaneous-ly positioned outside the thoracic cavity proximate to the apex of the left ventricle. The third electrode is electrically con-nected with the second electrode of the catheter. The electrode arrangement can be implanted without opening of the thoracic cavity by intravenously placing the catheter electrode within the heart of a patient and subcutaneously implanting the patch electrode between the skin and the thoracic cavity. The auto-matic implantable cardioverter/defibrillator senses life-threatening arrhythmic conditions of the heart and issues at least one cardioverting or defibrillating pulse that is applied between the electrode positioned within the right ventricle and the electrode pair comprising the electrodes positioned within the superior vena cava and subcutaneously adjacent the apex of the left ventricle.

Description

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CARDIOVERTING t~l~THOD AND APPARATUS UTILIZING
CATHETk~ AND PATCH ELECTRODES

The present invention relates to a novel electrode arrangement and method for an automatic implantable cardiover-ter/defibrillator. The electrode arrangement includes a cathe-ter electrode intravenously positioned within the heart of a patient wherein one electrode on the catheter is within the right ventricle and a second electrode on the catheter is within the superior vena cava. A third electrode, in the form of a flexible, substantially planar patch, is subcutaneously posi-tioned outside the thoracic cavity proximate to the apex of the left ventricle~ The third electrode is electrically connected with the second electrode of the catheter.
Approximately 250,000 Americans under the age of 65 die i yearly from a condition termed "sudden cardiac death". In the vast majority of these cases, the cause of death is ventricular tachycardia and/or ventricular fibrillation. An automatic im-plantable cardioverting/defibrillating device has been developed and shown to be effective in preventing sudden cardiac death from these causes. See, for example, U.S. Patent No. 4,407,298.
As used herein, the term cardioversion may be generally defined as the correction of either ventricular tachycardia or . .

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ventricular fibrillation by the discharge of ~lec~rical energy into the heart (.1-40 joules when discharged through internal electrodes). Ventricular tachycardia is an abnormally rapid heart rate (120-180 beats per minute) o~riginating in the the heart's main pumping chambers (ventricles) which is regular in periodicity and oftentimes is life threatening to the patient.
Ventricular fibrillation is generally a more rapid heartbeat disorder, disorganized and irregular, or non-periodic, and is fatal unless corrected wi~hin minutes by the discharge of elec-trical energy through the heart. More specific medical termin-ology often uses the term cardioversion to mean the synchronized delivery of an electrical shock to the heart to correct ventric-ular tachycardia. Defibrillation, then, is often referred to as the nonsynchronized delivery of -electrical e~ergy to the heart to correct ventricular fibrillation. Internal cardiover-sion is usually effective with .1 to 3 joules of electricalenergy when delivered in synchronism with the electrical heart-beat. Internal defibrillation requires 5 to 30 or more joulesof electrical energy, depending largely on the electrode system used.
Over the years, a number of different types of electrode systems have been suggested for use with an automatic implant-able cardioverter/defibrillator. For example, U.S. reissue Patent No. Re. 27,757 describes an electrode arrangement whereby ( ~30946 one electrode is ~ormed on the distal end of an intravascular catheter that is positioned within the right ventricle, whereas the second electrode is positioned on the surface of the chest or sutured under the skin of the chest wall or directly to the ventricular myocardium. U.S. Patent No. 3,942,536 discloses a catheter electrode system wherein both electrodes are on a single intravascular catheter. The distal electrode is wedged in the apex of the right ventricle and the proximal electrode is immediately superior to the right atrium.
An improved intravascular catheter electrode system is described in u.s. Patent No . 4, 603, 705 issued August 5, 1986, and assigned to the same assignee as the present invention. There, the proximal electrode is lo-cated in the superior vena cava and the distal electrode is in the right ventricle. A sensing and pacing electrode is also provided at the distal tip of the catheter. The first two elec-trodes constitute the anode and cathode of the cardioverting/
defibrillating electrode pair. The tip electrode is used for sensing heart rate and pacing the heart. Using this single catheter system, energies required to defibrillate the humar heart have been found to vary between 5-40 joules, but in some 40-50% of patients, even the higher energies may be insufficient to defibrillate the heart. Thus, although this improved cathe-ter electrode system has many advantages, such as the capabili-:. ~

ty of being in~talled wit~out surqically invading the thoraciccavity, it has been found to have somewhat limited effective-ness in terminating ventricular fibrillation.
Various other electrode arrangements have also been em-ployed. In U~S. Patent No. 4,030,509, the implantable electrode system includes, among others, a flexible apex electrode design-ed to surround the apex of the heart, and various flexible base electrodes designed to surround the base of the heart.
The electrodes presently used by the automatic implant-able cardioverter/defibrillator consist of one defibrillating electrode placed in the superior vena cava/right atrial region, and a second flexible, conformal, defibrillating electrode placed on the outside of the heart, typically over the lateral wall of the left ventricle. See! U.S. Patents Nos. 4,161,952 and 4,270,549. Placement of the first electrode can be accom-plished by the insertion of a catheter-mounted electrode into one of the veins outside of the thorax and sliding the catheter electrode centrally into the venous system until the electrode portion is within the thorax and located at the junction of the superior vena cava and right atrium. Thus, for the placement of this electrode, it is not necessary to surgically enter the thorax. For the second electrode, however, it is necessary to make one of a variety of surgical incisions to open the thoracic cavity in order to place the electrode over the left ventricle ' ~0~68 ' of the heart. Each of these surgical approaches has serious disadvantages. Two such approaches involve extensive surgery and substantial patient recovery time with a cost currently between $8-12,000. These approaches consist of splitting the sternum (breastbone) or alternatively opening a space between the ribs in order to gain access to the surface of the heart.
A third approach involvès making a smaller incision under the xiphoid process of the sternum, which is simpler from a surgical point of view, but still involves entering the thoracic cavity.
Moreover, this approach sometimes does not allow convenient positioninq of the left ventricular electrode.
With providers of health care becoming increasingly cost conscious due to limited payment resources, it is more and more important to reduce surgical costs in order that life-saving therapies can be made broadly available. Thus, to both reduce the morbidity associated with the surgery of defibrillator elec-trode implantation and to reduce the cost, it is highly desir-able tb have a means of electrode implantation which does not involve the surgical opening of the thoracic cavity.

The present invention is an improved electrode placement method and apparatus for an automatic implantable cardioverter/
defibrillator that does not require the surgical opening of the thoracic cavity. The electrode system includes an intravascular ~r _ _ .. .. . . .. . . .. . . . . .. . .. .

1309~68 catheter insertable within the heart o a patient having a first electrode adjacent the distal end of the catheter and a second electrode positioned at the proximal end of the catheter. This catheter electrode is of the type described in u.s. Patent No.
4,603,705, issued August 5, 1986.
Associated with this catheter elec-trode is a third electrode, in the form of a flexible patch electrode, that is placed subcutaneously outside of the thoracic cavity (rib cage), but proximate to the apex of the left ventri-cle. This third patch electrode is electrically connected (i.e.
in common) with the second ele~trode of the catheter, the latter of which is positioned in the superior vena cava~right atrium region. The first, or distal, electrode of the catheter, com-pletes the cardioverting/defibrillating circuit. -A pulse, or shock, of electrical energy is discharged between the firs;
electrode and the combined second electrode/patch electrode to result in a more efficient depolarization of the heart tissue.
Indeed, in animals (dogs), the novel electrode arrangement has been found to significantly lower (by 25-33%) the electrical energy required to defibrillate the heart. The same improved result is expected in the human heart.

" ~3~9~8 It is therefore an ohjec:t oE the present invention to obviate or mitiya~e the above mentioned disa(lvantaqes hy providing a novel form of eLectrode arrangernent for an implantable cardioverter defibrillator system.

Other ohjects, features and advantaqes of the present invention will be apparent when reference is made to tne following detailed description qiven, by way of examples only, of a preferred embodiment as is illustrated in the appended drawinq.

The sole figure of the drawing includes the novel electrode arrangement in conjunction with an automatic i~plantable cardioverter/defibrillator system.

With reference to the sole figure of the drawing, an automatic implantable cardioverter/defibrillator 2, such as the i309468 type described in U.S. Pa~ent No. ~,407,298, is implantable within the abdominal region of the patient and is coupled with electrodes associated with the heart of the patient. The auto-matic implantable cardioverter/defibrillator 2 includes sensing and detecting` circuitry, as well as pulse generating circuitry, the output of the latter coupled to the implantable electrodes.
The cardioverter/defibrillator 2 senses an arrhythmic condition of the heart and, in response thereto, issues or emits cardio-verting or defibrillating pulses to the heart, through the im-plantable electrodes. The cardioverter/defibrillator includes output terminals comprised of an anode 4 and a cathode 6.
Coupled to the cardioverter/defibrillator 2 is a cathe-ter electrode arrangement. The catheter electrode may be identical to that described in u.s. Patent No. 4,603,705, issued August 5, 1986.

As described in u.s. Patent No. 4,603,705 the catheter electrode B is a flexible electrode that includes a distal portion 10 formed of a conductive spring electrode de-fined by the perimeter of the catheter and a proximal portion 12 similarly formed of a conductive spring electrode defined by the catheter. The spring electrodes at the distal and proximal portions 10,12 are close-wound electrically conductive-wires, preferably wound to approximately 20 turns per inch. This pro-vides a continuous electrically conductive surface which main-,~ - 8 -"
. _ .. .. ... . .. .. . .. .. ... . .. .. .. . . . .. . . .. .... ... _. ... .. . .
...
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( i3~6~8 tains its ~lexibility while still low~ring the impedance of the electr~des and thus permittting more current to be delivered.
Other electrode configurations may be employed, such as ring-type elctrodes~
The catheter electrode 8 is inserted ~ntravenously to aposition suçh that the distal electrode 10 ~s positioned in the right ventricular apex 14 of the heart and the proximal elec-trode 12 is positioned in the superior vena cava region 16 ofthe heart. It should be appreciated that, as the term is used herein, the superior vena cava 16 may also include portions of the right atrium 18. That is, the positioning of the proximal electrode 12 may be partially within the right atrium 13 rather than entirely within the superior vena cava 16, depending upon the dimensions of the patient's heart.
The distal electrode 10 is electrically connected, via a conductor 20 that extends along the length of the catheter 8 to the cathode terminal 6 of the cardioverter/defibrillator. The proximal electrode is simila~ly connected by a conductor 22 to the anode 4 of the cardioverter/defibrillator. The distal and proximal eiectrodes are electrically isolated from each other.
As described in u.s. Patent No. 4, 603, 705, the electrical surface area of the di~tal electrode 10 is approximately in the range of 300~to 500 sq. mm. Other surface areas might be chosen. Further, the spacing be~ween the rear-wardmost portion of the distal electrode 1~ and the forwardmost _ g _ , .. _ . ~ ... . . . ... . ., ... ... . .. , . . . .. .. _ . .. , . .. . . . .. . . . . .. _ . _ .. .
.. ......... .. . . . .. ... . . ... ..... . . .. . . . ... ... . .. . . .

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( 1309~68 portion of the proximal electrode 12 is approximately 8 to 14cm. Such a distance is chosen 60 that, for the majority of human heart sizes, the distal electrode 10 is within the right ventricular apex and the proximal electrode 12 is in the superi-or vena cava/right atrium region.
As also described in U.S. Patent No. 4,603,705, a distal sensing and pacing tip electrode 11 may be included on the catheter. The distal tip 11, in conjunction with the distal electrode 10, provides sensing of the heart rate as well as pac-ing functions. The tip 11 is electrically insulated from the distal electrode 10. Moreover, the distal electrode 10 and the proximal electrode 12 may be u_ed as an input to a probability density function (PDF) sensing circuit within the cardioverter~
defibrillator 2, whereby a PDF signal, indicative of an arrhyth-mia condition, may be detected. Thus, the implantable cardio-verter/defibrillator 2 senses heart rate via electrodes 10, 11, senses PDF si~nals via electrodes 10, 12 and issues cardiover-ting/defibrillating pulses, via electrodes 10, 12 and 24 (in a manner to be described) when the sensed heart rate/PDF signals satisfy certain predetermined criteria.
A flexible patch electrode 24 is electrically connected to proximal electrode 12, and is subcutaneously positioned out-side the thoracic cavity. That is, the patch electrode 24 is positioned between the skin 26 and the rib cage 28. This sub-A

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cutaneous implantation does not require any opening of the ribcage, or thoracic cavity 28.
The patch electrode is positioned proximate to the left ventricular apex 30 of the heart. Preferably, the patch elec-trode is positioned at the point of maximum impulse of the heart. This point is determined empirically by physically detecting where the maximum heart beat can be felt or heard.
The patch electrode 24 may be similar to that depicted : in U.S. Design Patent No. Des. 273,514. The patch electrode is a flexible, conformal, generally planar electrode having a me-tallic mesh on the surface facing the heart, and flexible insu-lating material on its rear side. The patch electrode may have a surface area of 13.5 sq.cm. although other surface areas may be effectively employed depending upon the energy levels required.
As depicted in the drawing, the patch electrode 24 is connected, via a conductor 32, to the conductor line 22 which connects the proximal electrode 12 to the anode 4 of the pulse generator 2. It is only necessary that the patch electrode be electrically connected , i.e. connected in common, with the proximal electrode 12; such connection could be made at the automatic implantable cardioverter/defibrillator directly or at any point along the line 22 between the automatic implantable cardioverter/defibrillator and the proximal electrode 12.

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In operation, the automatic implantable cardioverter/
defibrillator 2, after detecting a life-threatening abnormal heart rhythm, will issue a cardioverting or defibrillating pulse through its pulse generator section. At ~east one high energy pulse or shock is issued to the implantable electrodes by providing a voltage pulse across the distal electrode 10 and the combination of the proximal electrode 12 with the patch electrode 24. Preferably the high energy pulse is an exponen-tially decaying truncated voltage, as is depicted in the drawing at 34. As a result, an electrical field is created across the heart that more effectivel~ depolarizec the heart us~ng electri-cal energies 25-33% lower than would be effective solely UsiD3 the catheter electrode 8. If unsuccessful, additional pu1s2s may be issued, which may be at inc~eased energy levels_ Above, a specific embodiment of the present invention has been described. It should be appreciated, however, that this descript_on has been given for purposes of illustration only, and is in no way intended to limit the scope of the pre-sent invention. Rather, it is the intention that the present invention be limited only as defined in the appended claims.

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Claims

1. In an automatic implantable cardioverter/defibrilla-tor system for delivering electrical shocks to the heart of a patient to restore normal cardiac rhythm, the system including a pulse generator, having positive and negative electrical out-put terminals, for generating an electrical shock to implantable electrodes, the improvement comprising:
an intravascular catheter insertable within the heart of a patient having a first electrode defined by the catheter for positioning in the right ventricle, and a second electrode defined by the catheter, spaced from the first electrode, for positioning in the superior vena cava region;
a subcutaneous patch electrode electrically connected with said second electrode of the intravascular catheter, for positioning subcutaneously outside the thoracic cavity proximate to the apex of the left ventricle; and electrical conducting means for electrically connec-ting said first electrode with one pole of said pulse generator and for electrically connecting said second electrode and said subcutaneous patch electrode with the opposite pole of said pulse generator.

2. The implantable cardioverter/defibrillator system as claimed in claim 1 wherein said pulse generator emits at least one high energy shock to the implantable electrodes to create an electrical field across the heart between the first electrode and the combined second and subcutaneous patch electrodes.

3. The implantable cardioverter/defibrillator of claim 1 wherein said first and second electrodes are defined by closely-wound electrically conductive wire about the perimeter of the catheter.

4. The implantable cardioverter/defibrillator of claim 1 wherein said patch electrode comprise a substantially planar, flexible patch, one surface formed of metallic mesh, for positioning facing the left ventricle, the opposite surface formed of electrically insulative material.