WO1999008612A1

WO1999008612A1 - Multi-channel transmyocardial laser revascularization

Info

Publication number: WO1999008612A1
Application number: PCT/US1998/016450
Authority: WO
Inventors: Mark G. Fontenot
Original assignee: Fontenot Mark G
Priority date: 1997-08-14
Filing date: 1998-08-14
Publication date: 1999-02-25
Also published as: AU9102798A

Abstract

A bundle of fibers is employed to concurrently produce a plurality of channels (14a-14c) through the myocardium of a heart and into its left ventricle wherein each fiber (2) receives laser energy in its proximate end, has its distal end placed against the myocardium, and pressed through it upon the application of laser energy into the fibers; the individual fibers are constrained to follow different paths through the myocardium. The different paths may be parallel (19a-19e) or divergent (16a-16e).

Description

MULTI-CHANNEL TRANSMYOCARDIAL LASER REVASCULARIZATION

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

The present invention relates to transmyocardial laser revascularization of the heart and more particularly to the production of multiple channels through the myocardium by a single intrusion.

During a transmyocardial laser revascularization procedure, the surgeon vaporizes 10 to 50 transmyocardial channels using a laser coupled to a light guide. These channel are created through the free wall of the left ventricle, thus creating connections between the left ventricular cavity and the intramyocardial structures. This is expected to increase myocardial perfusion. The biologic theory underlying the transmyocardial laser revascularization technique is based on the biophysical principles of amphibian heart perfusion. In particular, the myocardial blood supply in amphibians does not primarily take place in the coronary arteries, instead blood is supplied via radial slits running directly from the ventricular cavity into the myocardium. Thus, in an amphibian heart, which is contrary to the human heat is univentricular and pumps mixed blood in that a certain volume is perfused through the radial arrangement of slits directly into the myocardium during every systole.

Histologically, channels created by a carbon dioxide laser, for example, coupled to a 1 mm O.D. light guide were surrounded by a zone of necrosis with an extent of about 500 μm a short time after vaporization. Within a week postoperatively, most of the channels are closed by fibrin clots, erythrocytes and macrophages. It has been noted that, at times, there are no obvious connections between the channels and the ventricular cavity. In specimens from patients who have died two or more weeks postoperatively, a granular tissue with high macrophage and monocyte activity was observed (Krabatsch T, et al: Histological findings after transmyocardial laser revascularization. J. Card. Surg. 1996, Vol. 11, pages 326- 331) . Within the healing tissue, a developing network of capillaries or angiogenesis was observed. Otherwise, tissue filling the channels did not substantially differ from scar tissue. Krabatsch and his coworkers (1996) did not observe connections between the ventricular cavity and the new capillaries. Whether these vessels within the closed channels have any impact on myocardial perfusion remains unclear. The biophysical notion, however, of modeling transmyocardial laser revascularization on the basis of amphibian heart perfusion, i.e., improving heart perfusion by creating channels and increasing the surface area and blood flow to the heart muscle, is lacking in evidence. A plausible explanation lies in wound healing and angiogenesis. Creating channels in the heart using light guides coupled to lasers initiates a cascade of biologic events causing these surgically created wounds to heal, i.e. wound healing. A common event during wound healing is angiogenesis.

Angiogenesis is a key step during the healing process of wounds. It is also a key step in tumor growth. Many angiogenic chemical factors have been described. In the case of attempts to control tumor size, inhibitors of angiogenesis (antiangiogenic agents) at a tumor site can be applied to limit growth. In the case of wound healing, more specifically, transmyocardial laser revascularization, angiogenic factors can be applied to vaporized channels to accelerate and intensify the wound healing process.

Therefore, improved perfusion of the heart is achieved secondary to increased blood supply to and within the wound resulting from the application of angiogenic factors. BRIEF SUMMARY OF THE INVENTION The present invention uses a bundle of multiple fibers to create concurrently multiple channels in the myocardium. Upon activation of a laser supplying energy to the fibers and subsequent insertion of the bundle into the myocardium, the fibers are constrained to spread in transverse forward directions creating multiple channels into the left ventricle. The result is multiple channels created by a single firing of the laser. The cladding of the fibers is preferably coated with a hydrogel or lubricious coating. The coating may be impregnated with an angiogenic factor or other medicaments.

The above and other features, objects and advantages of the present invention, together with the best means contemplated by the inventor thereof for carrying out the invention will become more apparent from reading the following description of a preferred embodiment and perusing the associated drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates a bundle of individual laser light guides;

Figure 2 illustrates the bundle of fibers in contact with the exterior surface of a myocardium wall;

Figure 3 illustrates penetration of the myocardium by the laser fibers; Figure 4 illustrates the fibers returned to their initial position and the channel pattern produced;

Figure 5 illustrates the pattern of the channels produced by the present invention;

Figures 6a and 6b illustrate the structure for ensuring that the fibers proceed along desired paths;

Figures 7a and 7b illustrate the result of and structure for causing the fibers to enter the myocardium in parallel; and Figure 8 illustrates the structure of a fiber that is preferably employed in the present invention. DETAILED DESCRIPTION OF THE INVENTION

Referring now to Figure 1 of the accompanying drawings a bundle 2 of individual laser conducting fibers 2a, 2b and 2c has the fibers at an angle relative to one another. The angle is a function of the size of the heart and the number of separate fibers entering the myocardium. The bundle 2 is connected to a laser, not illustrated, via a unitary transfer fiber 4. A handle 6 slidably carries the fiber bundle 2 and the transfer fiber 4. A stop 8 is secured to the handle 6 and cooperates with a trigger 10 secured to the junction of the multiple fibers 2 and the transfer fiber 4. The trigger 10 is used to limit the incursion. In use the fiber bundle 2 is placed against the myocardium, see Figure 2, with the fiber bundle 2 in the withdrawn position. The laser is activated and the surgeon, while holding the handle, pushes the trigger toward the myocardium resulting in penetration of the myocardium by the fibers and their entry into the left ventricle, see Figure 3. Note the forward movement of the fiber bundle 2 is limited by engagement of the trigger 10 with stop 8. The surgeon releases the trigger 10 and the spring 12 retracts the fiber bundle 2 to the position illustrated initially in Figure 2 and again illustrated in Figure 4.

The pattern of channels 14a, 14b and 14c produced by the fiber bundle 2 of Figure 1 is illustrated in Figures 4 and 5. The pattern produced is not limited to that illustrated in Figures 3-5 but may be two dimensional as illustrated in Figures 6a and 6b. In this array fibers 16a- 16e are located at α° relative to one another as in Figures 1-5.

Reference is now made to Figures 6a and 6b. The position of the fibers of the bundle 2 may be determined by a showerhead like cover 16 having open ended sleeves 16a, 16b, 16c, 16d and 16e for receiving fibers 17a to 17e. The fibers are thus guided along a desired path. The head 16 is appropriately secured to the end of the handle 6. Referring to Figures 7a and 7b the fibers 2 may .be caused to enter the myocardium parallel to one another. In this configuration the fibers are caused to initially diverge from one another and then be redirected after being spread apart so as to enter the myocardium in a parallel array.

Specifically, and reference is made to Figures 7a and 7b, an end plate 18 secured to the distal end of handle 6 has sleeves 19a to 19d that initially direct the fibers 2 away from a central fiber 19e and from each other. The sleeves thereafter turn through a shallow curve at 20 to direct the fibers parallel to one another. The fibers produce parallel channels in the myocardium permitting a greater concentration of channels in a given region.

Referring to Figure 8 an optical fiber 5 has a cladding 21 of a fluorinated polymer to prevent leakage of the light of the laser from being dispersed along its length and further to strengthen the fiber.

The cladding 21 may be covered by a hydrophilic coating 23 with or without a medicament. The coating may provide a lubricating effect and thus ease the movement of the fibers through the surrounding components as well as the myocardium. The medicament preferred in the usage of the equipment for the purposes of the present invention is an angiogenesis producing agent. There are many of these agents such as IGF-I, IGF-II, PDGF, bFGE, TGF-beta, to name a few.

In summary, the apparatus of the present invention permits a surgeon to produce several passages through the myocardium with a single energization of the laser thus greatly reducing the time necessary to conduct the procedure. The benefit is primarily to the patient but is also of benefit to the surgeon. The procedure is tedious and quite trying on the surgeon. As indicated the angle between the fibers is to an extent a function of heart size and the surface of the heart that is most easily accessible to the surgeon. The ability to inject a angiogenesis agent into the channels enhances the formation of capillaries around the scar tissue and thus is an important factor in achieving the desired result.

Once given the above disclosure, many other features, modifications and improvements will become apparent to the skilled artisan. Such features, modifications and improvements are, therefore, considered to be a part of this invention, the scope of which is to be determined by the following claims.

Claims

1. Apparatus for transmyocardial revascularization of a muscle of the heart comprising a bundle of light conducting fibers, having a proximate end and a distal laser energy projecting end, means for introducing laser energy into said proximate ends of the fibers, means constraining the distal end of each fiber to be initially directed in a different direction from each of the other said fibers, means for introducing the distal ends of the fibers into the myocardium subject to the procedure upon application of laser energy to the proximate ends of the fibers.

2. The apparatus according to claim 1 wherein said fibers enter the myocardium divergent relative to one another.

3. The apparatus according to claim 1 wherein said means constraining comprises further means for rendering said fibers parallel to one another at the point of introduction into the myocardium.

4. The apparatus according to claim 1 wherein the means for constraining the distal ends of said fibers comprises a handle for supporting the proximate ends of said fibers along an axis, and a plate located transverse to the axis of the proximate ends of said fibers, said plate having a plurality of apertures located at prescribed distances from said axis and from one another, each said fiber having its distal end located in a different one of said apertures.

5. The apparatus according to claim 1 wherein said means for introducing comprises said fibers slidably mounted on said handle along said axis, and a trigger for sliding the fibers along said axis and into the myocardium.

6. The apparatus according to claim 1 further comprising a sleeve extending from said plate at each aperture and having an inner diameter of approximately the outer diameter of said fiber, and each said fiber positioned in a different one of said sleeves.

7. An optical fiber structure for conducting laser energy comprising an optical fiber, a cladding on said fiber of a fluorinated polymer, and a coating over said cladding of a hydrophilic material providing a lubricant.

8. An optical fiber structure according to claim

5 wherein said coating includes a medicament having an angiogenesis producing agent.

9. The method of producing transmyocardial laser revascularization of a muscle of the heart comprising the steps of placing a bundle of divergent optical fibers having proximate and distal ends against a myocardium to produce a plurality of channels through the myocardium and into a chamber of the heart, introducing laser energy into the proximate ends of the optical fibers while concurrently pressing the distal ends of the fibers into the myocardium along distinct and separate paths.

10. The method according to claim 7 further comprising applying a medicament having angiogenesis properties to an exterior of the fibers.