Abstract:
A transmyocardial implant includes a hollow rigid conduit having a vessel portion and a myocardial portion. The vessel portion is sized to be inserted into a blood vessel segment taken from a non-coronary artery or vein. The myocardial portion is sized to extend from the vessel portion and through a myocardium into a heart chamber. The conduit has open vessel and myocardial ends on respective ends of the vessel and myocardial portions to define a blood flow pathway within an interior of the conduit between the vessel and myocardial ends. The myocardial portion is formed of a conduit material sufficiently rigid to resist deformation and closure of the pathway in response to contraction of the myocardium. The vessel portion has a radial compliance approximating a radial compliance of the vessel.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention pertains to an implant for passing blood flow directly between a chamber of the heart and a coronary vessel. More particularly, this invention pertains to a transmyocardial implant with a non-coronary blood vessel attached to the implant.  
         BACKGROUND OF THE INVENTION  
         [0002]    Coronary artery disease is the leading cause of premature death in industrialized societies. The mortality statistics tell only a portion of the story. Many who survive face prolonged suffering and disability.  
           [0003]    Arteriosclerosis is “a group of diseases characterized by thickening and loss of elasticity of arterial walls.” DORLAND&#39;S ILLUSTRATED MEDICAL DICTIONARY 137 (27th ed. 1988). Arteriosclerosis “comprises three distinct forms: atherosclerosis, Monckeberg&#39;s arteriosclerosis, and arteriolosclerosis.” Id.  
           [0004]    Coronary artery disease has been treated by a number of means. Early in this century, the treatment for arteriosclerotic heart disease was largely limited to medical measures of symptomatic control. Evolving methods of diagnosis, coupled with improving techniques of post-operative support, now allow the precise localization of the blocked site or sites and either their surgical re-opening or bypass.  
           [0005]    The traditional open-chest procedure for coronary artery bypass grafting requires an incision of the skin anteriorly from nearly the neck to the navel, the sawing of the sternum in half longitudinally, and the spreading of the ribcage with a mechanical device to afford prolonged exposure of the heart cavity. If the heart chamber or a vessel is opened, a heart-lung, or cardiopulmonary bypass, procedure is usually necessary.  
           [0006]    Depending upon the degree and number of coronary vessel occlusions, a single, double, triple, or even greater number of bypass procedures may be necessary. Often each bypass is accomplished by the surgical formation of a separate conduit from the aorta to the stenosed or obstructed coronary artery at a location distal to the diseased site.  
           [0007]    The major obstacles to coronary artery bypass grafting include both the limited number of vessels that are available to serve as conduits and the skill required to effect complicated multiple vessel repair. Potential conduits include the two saphenous veins of the lower extremities, the two internal thoracic (mammary) arteries under the sternum, and the single gastroepiploic artery in the upper abdomen.  
           [0008]    Newer procedures using a single vessel to bypass multiple sites have evolved. This technique has its own inherent hazards. When a single vessel is used to perform multiple bypasses, physical stress(e.g.,torsion) on the conduit vessel can result. Such torsion is particularly detrimental when this vessel is an artery. Unfortunately, attempts at using artificial vessels or vessels from other species (xenografts), or other non-related humans (homografts) have been largely unsuccessful. See LUDWIG K. VON SEGESSER, ARTERIAL GRAFTING FOR MYOCARDIAL REVASCULARIZATION: INDICATIONS, SURGICAL TECHNIQUES AND RESULTS 38-39 (1990)  
           [0009]    While experimental procedures transplanting alternative vessels continue to be performed, in general clinical practice, there are five vessels available to use in this procedure over the life of a particular patient. Once these vessels have been sacrificed or affected by disease, there is little or nothing that modern medicine can offer. It is unquestionable that new methods, not limited by the availability of such conduit vessels, are needed.  
           [0010]    Direct revascularization devices (DRDs) provide an alternative to traditional vein graft bypass operations incorporating harvested vessels. DRDs permit the revascularization of coronary vessels by placement of an artificial conduit between a heart chamber and the coronary vessel, allowing blood flow directly from the heart chamber into a lumen of the vessel. DRDs and methods for implanting such devices are described in U.S. Pat. No. 5,944,019.  
           [0011]    DRDs incorporating conduit portions with different degrees of radial compliance are described in currently pending and commonly assigned U.S. patent application Ser. No. 09/304,650. Utilization of varying degrees of radial compliance allows the conduit to have sufficient rigidity within the muscle of the heart wall to prevent collapse while having flexibility more closely matching that of the target vessel.  
           [0012]    Further, U.S. Pat. No. 6,250,305 describes the incorporation of natural vessel grafts with artificial conduit DRDs to perform revascularization. The techniques described in the &#39;305 patent allow the connection to the target vessel to be made using a natural vessel graft. While this is a distinct improvement to prior art of vein graft bypass procedures described above, the issue of only having a limited number of suitable vessel for natural graft bypass remains. An approach permitting direct revascularization of coronary vessels incorporating the advantages of artificial conduit DRDs with the advantages of natural vessel grafts is desirable.  
         SUMMARY OF THE INVENTION  
         [0013]    The present invention relates to an implant for establishing a blood flow path between a heart chamber and a coronary vessel through the myocardium. The implant includes a hollow conduit having a vessel portion and a myocardial portion. The myocardial portion is sized to extend from the vessel portion and through the myocardium to the heart chamber. The myocardial portion is preferably formed of a conduit material sufficiently rigid to resist deformation and closure of the pathway in response to contraction of the myocardium. The vessel portion extends outside the heart wall. In certain embodiments, the vessel portion can have an open structure such as a mesh. In one embodiment, the vessel portion is connected to the coronary vessel by using a relatively short natural graft section that is secured to the open mesh and is also secured to the coronary vessel. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is a side perspective view of a prior art transmyocardial conduit for use with the present invention.  
         [0015]    [0015]FIG. 2 is a side perspective view of a prior art stent for use with a transmyocardial conduit for use with the present invention, shown elongated to define a smaller diameter.  
         [0016]    [0016]FIG. 3 is a side perspective view of the prior art stent of FIG. 2, shown shortened to define a larger diameter.  
         [0017]    [0017]FIG. 4 is a side cross-sectional view of the prior art transmyocardial conduit of FIG. 1 with the stent of FIGS. 2 and 3 mounted about a vessel end.  
         [0018]    [0018]FIG. 5 is a cross-sectional view of an occluded coronary vessel on a heart wall.  
         [0019]    [0019]FIG. 6 is a cross-sectional view of the coronary vessel of FIG. 5 with the vessel incised and legated distal the occlusion.  
         [0020]    [0020]FIG. 7 is a cross-sectional view of the coronary vessel of FIG. 6 with the transmyocardial conduit of FIG. 4 extending through the myocardium.  
         [0021]    [0021]FIG. 8 is a cross-sectional view of the coronary vessel of FIG. 7 with the transmyocardial conduit connecting a heart chamber with a lumen of the coronary vessel.  
         [0022]    [0022]FIG. 9 is a perspective view of a second embodiment of a transmyocardial conduit connecting a heart chamber to a lumen of a coronary vessel without a stent about the conduit.  
         [0023]    [0023]FIG. 10 is a partial cross-sectional view of a third embodiment of a transmyocardial conduit according to the present invention connecting a heart chamber with a lumen of a coronary vessel including a tissue-growth promoting material about the myocardial portion of the conduit.  
         [0024]    [0024]FIG. 11 is a side perspective view of a portion of a heart wall with a fourth embodiment of a transmyocardial conduit connecting a heart chamber with a lumen of a coronary vessel via an end-to-side anastomosis.  
         [0025]    [0025]FIG. 12 is a side perspective view of a portion of a heart wall with a fifth embodiment of a transmyocardial conduit connecting a heart chamber with a lumen of a coronary vessel via an end-to-side anastomosis with the conduit at a non-perpendicular angle to the vessel. 
     
    
     DETAILED DESCRIPTION  
       [0026]    With initial reference to FIGS. 1 through 4, a prior art transmyocardial conduit  10  is shown in the form of an L-shaped rigid tube. In this embodiment, conduit  10  is made of titanium but may be made of any other rigid biocompatible material such as pyrolytic carbon or may be titanium coated with pyrolytic carbon. The material of the conduit  10  is preferably sufficiently rigid to withstand contraction forces of the myocardium. By way of example, conduit  10  will have an outside diameter in the range of about 1 to 4 millimeters and a wall thickness of about 0.25 millimeters.  
         [0027]    Conduit  10  has a vessel portion  12  including a first open end  16  into an interior  19 . Conduit  10  has a myocardial portion  14  extending at an angle to the axis of portion  12  and including a second open end  18 . Myocardial portion  14  is sized to extend through the myocardium  84  (as shown in FIG. 7) so that vessel portion  12  is at or near an outer wall of myocardium  84  and open end  18  of myocardial portion  14  protrudes into a heart chamber  86  of a patient&#39;s heart.  
         [0028]    Conduit  10  may include a stent  20  (shown in FIGS. 2, 3 and  4 ) which may be a tubular member of lattice formed of biocompatible material. When elongated, stent  20  has an initial diameter D 1  (shown in FIG. 2) which is larger than a conduit outer diameter D 0  (shown in FIG. 1) and further sized for stent  20  to be inserted into lumen  80  of the vessel to be used as a connector. When shortened, stent  20  is expandable to an enlarged diameter D 2  (shown in FIG. 3). It will be appreciated that coronary stents such as stent  20  are commercially available in a wide variety of sizes, shapes, materials and mode of expansion (e.g., self-expanding or balloon expandable). Stent  20  can be any member whose outside dimensions expand to fit within a lumen  80  of a coronary vessel  82  (see FIG. 5) and whose internal dimensions permit insertion of vessel portion  12  within stent  20 . Conduit  10  and stent  20  are described in further detail in U.S. Pat. No. 6,053,942, the disclosure of which is incorporated herein by reference.  
         [0029]    Referring now to FIGS. 5 through 8, use of a first embodiment of a transmyocardial conduit  10  to revascularize a coronary vessel  82  with an occlusion  87  is shown. Vessel  82  lies on an outer surface of myocardium  84 . Occlusion  87  prevents adequate flow of blood to vessel  82  distal to occlusion  87 , as shown in FIG. 5. To provide adequate blood flow distal to occlusion  87 , vessel  82  is legated distal to an obstruction  87  with sutures  85 . An incision is made through the vessel  82  distal to the legating suture  85 , as shown in FIG. 6, defining a first distal incised end  82   a.    
         [0030]    A portion of vessel  82  is dissecting at first incised end  82   a  to define a second distal incised end  82   b . The segment of vessel removed between first incised end  82   a  and second incised end  82   b  may be used to form a graft  30  having ends  31  and  32  (see FIG. 7). Alternatively, as discussed below, another source may be available to provide graft  30 . For example, in another embodiment, graft  30  is a natural vein segment harvested form within the body of the patient for whom the coronary vessel revascularization is being performed. In a gap defined between occlusion  87  and incised end  82   a , a blood flow pathway is formed through myocardium  84  to allow fluid communication with a heart chamber  86 . Conduit  10  is placed within the blood flow pathway with myocardial portion  14  extending the myocardium  84  into heart chamber  86 , as shown in FIG. 7. Vessel portion  12  of conduit  10  lies along an exterior surface of myocardium  84 . Fixed about an end of vessel portion  12  opposite myocardial portion  14  is stent  20 .  
         [0031]    In FIG. 8, end  31  of graft  30  is positioned about stent  20  and secured by sutures  83  to stent  20 . End  32  of graft  30  has been attached to vessel  82  and allows fluid communication between heart chamber  86  and lumen  80  via an interior  19  of conduit  10 . The connection between graft  30  and vessel  82  is an end-to-end anastomosis  91 .  
         [0032]    Referring now to FIG. 9, a second embodiment of the present invention is shown. This embodiment is similar to the first embodiment described above with reference to FIGS. 5 through 8. In the second embodiment, graft  30  is connected directly to vessel end  12  of conduit  10  without stent  20  interposed between and is secured to conduit  10  with sutures  83 . All other elements of the first embodiment are included in the second embodiment.  
         [0033]    Referring now to FIG. 10, a third embodiment of a transmyocardial conduit for revascularizing a coronary vessel is shown. This embodiment is similar to the first embodiment detailed above with the additional of a sleeve  15  made of a tissue-growth inducing material such as polyester about myocardial portion  14 . The use of such sleeves about myocardial implants to anchor the implants within the myocardium is discussed in further detail in U.S. Pat. No. 5,984,956, the disclosure of which is incorporated herein by reference.  
         [0034]    In place of stent  20 , conduit  10  in FIG. 10 includes a compliant sleeve  120  about which is mounted graft  30 . Complaint sleeve  120  has a degree of radial compliance which is adapted to match the radial compliance of graft  30 . Further description of the use of sleeve  120  with radial compliance matched to the compliance of the vessel into which the sleeve extends is found in commonly-assigned pending U.S. patent application Ser. No. 09/304,650, the disclosure of which is incorporated herein by reference.  
         [0035]    Referring now to FIG. 11, a further embodiment of a transmyocardial conduit for revascularizing a coronary vessel is shown. In this embodiment, conduit  10 , with or without stent  20 , provides fluid communication between heart chamber  86  and lumen  80  via graft  30  which is connected to vessel  82  with an end-to-side anastomosis  90 . This embodiment does not require vessel  82  to be incised or dissected. However, since vessel  82  is not being incised or dissected, an alternative source for graft  30  within the patient&#39;s body will need to be found. Following a standard method of coronary artery bypass surgery, a portion of a suitable blood vessel such as the internal mammary artery may be available from segments of the artery not required for the bypass procedure. Alternatively, other vessels may be used as a source for graft  30 , such as the radial artery, the lesser saphenous vein, an arm vein, the gastroepiploic artery, the inferior epigastric artery or other vessels of suitable size.  
         [0036]    Conduit  10  is placed by inserting second portion  14  through myocardium  84  with open end  18  in communication with left ventricle  86 . First portion  12  is inserted into enlarged stent  20  (See FIGS. 1, 5). An embodiment of a method of placing an implantable conduit between a chamber of the heart and a coronary vessel is described in detail in U.S. Pat. No. 5,755,682, the disclosure of which is hereby incorporated by reference.  
         [0037]    In one embodiment of the invention, following a standard method of coronary artery bypass surgery, the surgeon may have a portion  30  of a suitable blood vessel such as the internal mammary artery. Depending on the availability of vessels and the technique preferred by the surgeon other vessels may be used such as the radial artery, the lesser saphenous vein, an arm vein, the gastroepiploic artery or the inferior epigastric artery. Portion  30  has two ends  31 ,  32 . The surgeon then takes portion  30  of this residual vessel (for example, the internal mammary artery) and slides end  31  over the stent  20 . (See FIG. 5) Eend  32  of the portion  30  is connected to end  82   b  of the ligated coronary artery  82  by methods well known to those with skill in the art. The surgically connected structure consisting of the stent  20 , the piece of blood vessel  30  and the coronary artery  82  is then stabilized on the myocardium  84 .  
         [0038]    This may be the preferred embodiment of the present application in that it allows a more efficient and complete usage of harvested vessels during bypass procedures. Using the present invention in conjunction with standard vein graft bypass procedures will permit multiple bypasses to be created with a single harvested vessel by utilizing pieces of the native vessel that otherwise would have been discarded. In this way, patients requiring additional bypass procedures at a future date will still have usable vessels for traditional bypass procedures. Alternatively, for patients who have no remaining vessels suitable for traditional bypass procedures, the present method offers an approach which utilizes vessels not otherwise considered usable for bypass.  
         [0039]    In another embodiment of the invention shown in FIG. 11, conduit  10  is implanted by inserting second portion  14  through myocardium  84  with open end  18  in communication with left ventricle  86 . End  31  of portion  30  is attached to first portion  12  of conduit  10  either directly or utilizing a stent  20  depending on the preference of the surgeon. End  32  is then anastomosed to the selected coronary artery  82  via an end to side anastomosis  90 .  
         [0040]    [0040]FIG. 12 shows a similar embodiment to that shown in FIG. 11, with the difference being that conduit  10  forms an end-to-side anastomosis  90  with vessel  82  at an angle. The angle of anastomosis  90  is angled to bias flow out of conduit  10  in the direction of normal blood flow within vessel  80 .  
         [0041]    From the foregoing, the invention has been described in a preferred embodiment. Modifications and equivalents of the disclosed concepts are intended to be included within the scope of the claims.