Abstract:
Methods and devices for perfusing a blood vessel during the entire course of an end-to-side or end-to-end anastomosis procedure. One method can be used to form an end-to-side anastomosis of a saphenous vein graft to a coronary artery during an off-pump, beating heart, coronary artery bypass graft. In this example, the distal end of an elongate tube carrying a saphenous vein graft is advanced into an arteriotomy distal to an occlusion in the coronary artery. Perfusing blood flow is provided through the tube to the coronary artery, the vein graft is advanced over the tube to the arteriotomy and sutured completely to the coronary artery. The elongate tube can be retracted through the now secured vein graft, and the coronary artery supplied again from the proximal end of the vein graft. Some tubular devices include a reversibly expandable distal region, to form a seal between the inserted tube and the coronary artery being perfused, to prevent blood flow into the surgical field.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention is related to medical devices. More specifically, the present invention is related to medical devices that can be used to perform blood vessel anastomosis procedures. The present invention can find one non-limiting use in performing cardiac artery bypass grafts on beating hearts.  
       BACKGROUND OF THE INVENTION  
       [0002]     In coronary bypass surgery, a partially occluded coronary artery can be bypassed by grafting a conduit to the coronary artery to supply perfusing blood, to a location downstream or distal of the occlusion. The conduit is often a saphenous vein graft or an internal mammary artery (IMA). The conduit has a distal end, to be joined distal to the occlusion, and a proximal end, to be joined to a source of perfusing blood, typically the aorta.  
         [0003]     In a typical procedure, an incision, an arteriotomy, is made in the coronary artery distal to the occlusion. The incision often results in bleeding through the incision into the surgical field. The blood can be suctioned and/or blown away to preserve the surgeon&#39;s field of view. The distal end of the conduit can be brought to bear to the side of the coronary artery near the arteriotomy. An end-to-side anastomosis can then be performed.  
         [0004]     In the end-to-side anastomosis, the distal end of the conduit is sewn to the side of the coronary artery over the incision. During the anastomosis procedure, the blood flow from the incision may be quite profuse. The blood may come through the original blood vessel, which may be only partially occluded. The blood may also come from the “collateral flow” of blood coming from the coronary artery distal of the occlusion. The collateral flow can come from vessels that have grown to supply the coronary artery distal of the occlusion, often in response to the occlusion.  
         [0005]     The blood flowing from the incision is not flowing to the heart, which can result in ischemia, which can be severe. The ischemia can put additional time pressure on the surgeon. If severe, the ischemia may force the surgeon to put the patient on a blood pump where this was initially to be avoided. In some cases, a planned for minimally invasive beating heart procedure is changed into an open chest, arrested heart procedure, with the patient put onto a heart-lung machine. The blood can also flood the surgical field, interfere with the surgeon&#39;s vision, and thus interfere with, and lengthen, the anastomosis procedure.  
         [0006]     The ischemia problem has been addressed by off-pump perfusion-assisted direct coronary artery bypass (PADCAB™) (Quest Medical, Austin Tex.), using a distal perfusion device. Medtronic (Minneapolis, Minn.) sells the QuickFlow™ DPS™ Distal Perfusion System. The distal perfusion device includes a tubular member that can be supplied at the proximal end with perfusing blood from the aorta or the femoral artery. The distal end of this device can be inserted into the incision in the artery. The blood flow through the distal perfusion device can supply the coronary artery with some perfusing blood during the anastomosis procedure. The distal perfusion device distal end can be difficult to hold in position during some surgeries, especially minimally invasive surgeries. Blood flow through the incision typically continues, into the surgical field.  
         [0007]     When using the distal perfusion device, the sutures required to join the end of the conduit to the coronary artery are begun, but are often initially made very loose, allowing the conduit distal end to be located some distance away from the side of the coronary artery be sutured. The conduit is thus be only partially joined to the coronary artery, while working around the distal perfusion device inserted into the incision in the coronary artery. Working around a tube protruding from the anastomosis site may provide an added, unneeded challenge to the surgeon.  
         [0008]     The distal perfusion device can then be withdrawn, and the conduit completely joined to the coronary artery, by adding more sutures and by tightening the previously made sutures. When the distal perfusion device is withdrawn, ischemia may begin and the blood flow into the surgical field worsen. In some situations, the patency of the anastomosis is less than desirable, as the end of the conduit had become at least partially closed or even sewn shut at the anastomosis. This lack of patency is understandable, given the 1-2 millimeter inside diameter of a coronary artery, the blood flow about the anastomosis site, and the time pressure on the surgeon, which is only increased by ischemia.  
         [0009]     What would be desirable are devices and methods for perfusing coronary arteries during the entire anastomosis procedure, allowing the anastomosis to be completely formed between a conduit and a coronary artery. What would be advantageous are devices and methods for reducing blood flow through the anastomosis site into the surgical field. Methods for maintaining patency during the anastomosis procedure would also be beneficial.  
       SUMMARY OF THE INVENTION  
       [0010]     The present invention provides methods for joining a blood conduit to a blood vessel. The methods can include making an incision in the blood vessel wall and inserting a tubular member into the conduit. The tubular member carrying the conduit can be advanced into the blood vessel through the incision. The conduit distal region can then be fixedly joined to the vessel wall near the incision, while providing an oxygenated liquid flow through the tubular member disposed within the conduit and into the blood vessel. In some methods, inserting the tubular member within the conduit is performed before advancing the tubular member into the blood vessel, while in other methods, the inserting is performed after the advancing the tubular member into the blood vessel. The fixedly joining can include suturing the conduit to the blood vessel.  
         [0011]     In some methods, the blood vessel is a coronary artery, the conduit is a saphenous vein graft, and the method includes fixedly joining the saphenous vein graft to the coronary artery to perform a coronary artery bypass. In other methods, the conduit is a radial artery, or an internal mammary artery (IMA) having both proximal and distal ends available, a xenogenic blood vessel, or an artificial blood vessel. In some methods, the oxygenated liquid is blood, which can be supplied under pressure higher than the patient&#39;s own blood pressure. This added pressure can be provided by a spring-loaded, pressure limited syringe, by a manual bulb, or any other suitable device for providing pressurized blood.  
         [0012]     In a preferred method, the tubular member has a distal region, which can be reversibly radially expanded to increase the distal region outer diameter once the tubular member has been inserted into the blood vessel. The distal region can be increased in outer diameter to form a seal between the tubular member and the blood vessel being supplied with blood. One tubular member includes a flow restrictor in the distal region and a weakened wall region proximal of the flow restrictor. In this device, providing blood or other oxygenated fluid under pressure through the tubular member increases the pressure in the tube that causes the weakened distal region to expand outward, similar to a balloon. In some methods, blood is supplied from the patient&#39;s aorta, while in other methods, the blood is supplied from the patient&#39;s femoral artery. In some closed chest procedures, blood can be supplied to the tubular member from the femoral artery, with the tubular member deployed within the chest via a port or simple stab wound.  
         [0013]     The present invention finds one use in providing a method for performing an end-to-side anastomosis during a coronary artery bypass graft. In this application of the invention, an arteriotomy is made distal to an occluded or stenosed coronary artery. This may be done off pump, with the patient&#39;s heart still beating, even in a minimally invasive procedure. A suitable blood conduit, for example a saphenous vein graft, can be provided, already disposed over the elongate tube of the present invention, also referred to as the transconduit perfusion catheter or TPC. The TPC carrying the saphenous vein graft can be advanced to the arteriotomy, with the distal region of the TPC advanced through the arteriotomy and into the coronary artery away from the stenosis. The distal region of the TPC can then be expanded to form a seal between the distal region of the TPC and the coronary artery. This can reduce or eliminate blood flow through the arteriotomy that can obscure the surgical field. Blood can then be provided to the TPC proximal end, flowing through the TPC and into the coronary artery, thus perfusing the artery during the anastomosis procedure. With the coronary artery being perfused, the saphenous vein graft or other conduit can be advanced over the TPC to the arteriotomy site, and completely sutured to the coronary artery. The TPC can thus act to perfuse the coronary artery, to reduce collateral blood flow into the surgical field, and function as a suture guide, guiding the conduit directly to the arteriotomy site and holding the conduit in position during the suturing.  
         [0014]     With the sutures in place, the TPC distal region can be reduced in profile and the TPC proximally retracted through the now secured conduit to the proximal region of the conduit. The conduit can be resupplied with blood by reexpanding the distal region of the TPC and/or by tying a purse-string suture around the proximal end of the conduit, securing it tightly about the TPC within.  
         [0015]     The present invention finds another use in providing a method for performing an end-to-end anastomosis of a blood vessel. This application is similar in some respects to the end-to-side anastomosis just described. In this application of the invention, the proximal end of a blood vessel to be extended is made accessible, rather than the arteriotomy just described. The TPC can be inserted into the blood vessel lumen through the proximal end and expanded. The conduit to be joined to the blood vessel can be advanced over the TPC and sutured to the blood vessel.  
         [0016]     The present invention also includes a device for providing perfusing blood during an anastomosis. The device can include an elongate tube having a proximal end, a distal region, a distal end, an outside diameter, and a length. The outside diameter can be less than about two millimeters and the length less than about 25 centimeters. The distal region can have a flow restrictor and a weakened distal wall region proximal to the flow restrictor. Increasing the fluid flow through the tube can cause the weakened wall region to expand radially outward to increase the outer diameter of the distal wall region. The weakened wall region is weaker than the remainder of the tube wall in a preferred embodiment. This weaker wall region can be provided by making the weakened wall region of a weaker material, a thinner material, or a scored material. The elongate tube can have an anti-thrombogenic, thrombolytic, and/or heparin-containing coating on the outer and/or inner surfaces of the tube, depending on the embodiment. A lubricious coating may also be provided on the inner and/or outer surfaces, again depending on the embodiment. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1  is a fragmentary, side view of a transconduit perfusion catheter having a valve at the proximal end;  
         [0018]      FIG. 2  is a fragmentary, side view of the distal portion of the catheter of  FIG. 1 , shown in an expanded configuration;  
         [0019]      FIG. 3  is a fragmentary, cut-away view of the distal region of the catheter of  FIG. 1 , having a thin distal wall region and a distal flow restrictor;  
         [0020]      FIG. 4  is a fragmentary, cut-away view, similar to  FIG. 3 , but shown in a pressurized, radially expanded configuration;  
         [0021]      FIG. 5A  is a fragmentary, perspective view of a conduit having a stylet inserted therethrough;  
         [0022]      FIG. 5B  is a fragmentary, perspective view of the conduit and stylet of  FIG. 5A  after the transconduit perfusion catheter of  FIG. 1  has been inserted over the stylet and within the conduit;  
         [0023]      FIG. 5C  is a fragmentary, perspective view of the conduit and transconduit perfusion catheter of  FIG. 5B , after the stylet has been removed;  
         [0024]      FIG. 5D  is a fragmentary, cut-away view of a blood vessel having the transconduit perfusion catheter advanced through an opening in the side of the blood vessel;  
         [0025]      FIG. 5E  is a fragmentary, side view of the blood vessel of  FIG. 5D , having the transconduit perfusion catheter distal region expanded within and the anastomosis sutures fully completed;  
         [0026]      FIG. 5F  is a fragmentary, side view of the blood vessel and conduit of  FIG. 5E , after the transconduit perfusion catheter has been moved to proximally supply the conduit;  
         [0027]      FIG. 6  is a fragmentary, side view an end-to-end anastomosis method according to the present invention, similar is some respects to  FIG. 5E ;  
         [0028]      FIG. 7  is a fragmentary, side, highly diagrammatic view of a pressurized blood supply source including a pressure limiting syringe, for supplying the transconduit perfusion catheter with a high pressure source of blood; and  
         [0029]      FIG. 8  is a fragmentary, side, highly diagrammatic view of a pressurized blood supply source including a manual squeeze bulb, for supplying the transconduit perfusion catheter with a high pressure source of blood 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]      FIG. 1  illustrates a transconduit perfusion catheter (TPC)  54  having generally a distal region  56 , a distal tip  55 , and a proximal region  57 . In the embodiment illustrated, TPC  54  also has a valve  70  coupled to proximal region  57  and a handle  72  for opening and closing the valve. A piece of standard arterial tubing  74  is coupled to valve  70  as well. TPC  54  is adapted to be inserted into a vessel for which an end-to-side anastomosis is to be performed. In one application, TPC  54  is to be inserted into an arteriotomy in a coronary artery. In this example, TPC  54  can have an outer diameter, indicated at D 1 , of less than 2 millimeters in some embodiments, less than 1.5 millimeters in other embodiments, and between about 1 millimeter and 1.5 millimeters in various embodiments. TPC  54  has a lumen extending therethrough, for carrying a perfusing, oxygen carrying fluid.  
         [0031]      FIG. 2  illustrates TPC  54  in one embodiment, having a distally expandable or swellable distal region  56 . Distal region  56  is preferably reversibly swellable or reversibly expandable to have an increased outer diameter, indicated at D 2 , relative to D 1  of  FIG. 1 . TPC distal region  56  can be increased in outer diameter after being inserted into a blood vessel, to provide a better seal between the outer surface of the TPC and the inner surface of the blood vessel to be perfused. In one embodiment, distal region  56  is made reversibly expandable by disposing a flow restrictor downstream of the region to be reversibly expanded in diameter. In one example, this flow restrictor is disposed near distal tip  55  of TPC  54 . Distal region  56  can be made to expand upon the application of increased pressure making region  56  weaker or more elastic relative to the more proximal region in some embodiments, and optionally weaker or more elastic than some more distal wall regions in other embodiments.  
         [0032]     In some embodiments, distal region  56  is made reversibly swellable by making it of a different material, being more elastic than the more proximal, and possibly, more distal regions. Distal region  56  may simply be weaker, being made of a softer durameter material, and being joined to harder durameter materials proximal of the distal region material. In other embodiments, distal region  56  is made to be reversibly expandable upon the application of pressure by making the wall thickness less than in the more proximal region. Distal region  56  could also be scored to make this region weaker and more likely to expand under pressure than the surrounding, nonscored areas. In still another embodiment, the TPC can be configured to be expanded, for example as shown in  FIG. 2 , in an unconstrained state, and made or forced to assume a narrower profile after inserting a stylet through the transconduit perfusion catheter to stretch the catheter lengthwise.  
         [0033]     TPC  54 , in one example, which can be used in open chest coronary bypass procedures, has a length of less than  25  centimeters, and can be between  22  and  25  centimeters. TPC  54  can be formed of any suitable biocompatible tubing material, well known to those skilled in the art. In some examples, TPC  54  is formed of silicone rubber, or polyurethane. TPC  54  can be coated externally and/or internally with an anti-thrombogenic or thrombolytic material, for example, Carmeda (TM), or a heparin coating. TPC  54  may also be coated with a lubricious, for example, hydrophilic material on the interior, and/or exterior surfaces, depending on the embodiment.  
         [0034]      FIG. 3  illustrates TPC  54 , having distal region  56  with a thinner wall thickness than distal tip  55  or more proximal wall region  48 . TPC  54  may also be seen to have a distal tip flow restrictor  53 .  FIG. 3  illustrates TPC  54  in an unpressurized configuration, where the outer diameter of distal region  56  is substantially similar to that of the average outer diameter of the catheter over its length.  
         [0035]      FIG. 4  illustrates TPC  54  in a pressurized configuration, having distal region  56  with an outer diameter substantially larger than that of the outer diameter shown in  FIG. 3 . In various embodiments, the outer diameter in the expanded state is at least 20%, 40%, 60%, or even 80% larger than that of the unexpanded configuration.  FIG. 4  illustrates TPC  54  in a “cobra hood” appearing configuration.  
         [0036]      FIG. 5A  illustrates a conduit  50  to be used in an end-to-side anastomosis procedure. Conduit  50  includes generally a distal region  51  and a proximal region  53 . Conduit  50  is not necessarily drawn to scale. In various embodiments, conduit  50  can be a saphenous vein graft, a radial artery, an internal mammary artery (IMA) having both ends free, a prosthetic artificial conduit (e.g., EPTFE or Dacron), a bioprosthetic conduit (e.g., a xenogenic blood vessel) or any other conduit for which an end-to-side anastomosis is to be performed. In some embodiments, the transconduit perfusion catheter can be used to form an end-to-end anastomosis as well.  
         [0037]     The TPC may be too flexible and not sufficiently pushable for some procedures according to the present invention. Therefore, in some methods, a stylet  52  is advanced through conduit  50  to make the conduit stiffer and more pushable. Stylet  52  can be formed of any suitable material, for example, stainless steel or Nitinol. Stylets are well known to those skilled in the art. Stylet  52  can be proximally advanced beginning at conduit distal region  51  in some embodiments, or distally advanced, beginning at conduit proximal region  53  in other embodiments.  
         [0038]      FIG. 5B  illustrates conduit  50  and stylet  52 , after TPC  54  has been advanced over stylet  52  and through conduit  50 . In some methods, TPC  54  is advanced proximally, while in other methods, TPC  54  is advanced distally through conduit  50  and over stylet  52 . TPC  54  includes distal region  56  as previously described and a proximal region  57 . TPC  54  can be positioned such that a couple centimeters of length are exposed beyond the distal end of conduit  50 .  
         [0039]      FIG. 5C  illustrates conduit  50  after stylet  52  has been removed, leaving TPC  54  in place, extending beyond the distal end of conduit  50 . TPC may have the proximal end coupled to a controllable blood supply during this procedure.  
         [0040]     The TPC can be primed in some methods by filling the TPC with a liquid prior to use. The liquid may be heparinized blood, heparinized saline, or the like. The TPC may have a luer lock connection on the proximal end. In such devices, the liquid can be injected into the TPC to prime the TPC through the luer lock connection. Alternatively, the liquid could be drawn into the TPC through application of suction.  
         [0041]      FIG. 5D  illustrates conduit  50  carrying TPC  54  being advanced close to a blood vessel  60  having an arteriotomy  64  therein. In the example illustrated, blood vessel  60  has a distal inside diameter within a lumen  61  and a more proximal blockage or stenosis  62 . In this example, the normal blood flow direction is given by arrow  63 . However, collateral blood flow may be caused in the opposite direction distal of the blockage, indicated by arrow  65 . TPC  54  can be advanced through arteriotomy  64  and into blood vessel  60 . TPC distal region  56  can be in the unexpanded configuration as the distal region is advanced into blood vessel  60 .  
         [0042]      FIG. 5E  illustrates TPC  54  after distal region  56  has been expanded to have a larger outer diameter, as previously discussed with respect to  FIGS. 1 through 4 . TPC distal region  56  can expand to form a seal with the inside wall of blood vessel  60  in some devices according to the invention. TPC  54  can thus act to block, eliminate, or significantly reduce the collateral blood flow into the surgical field. Perfusing blood can be supplied via an antegrade cardioplegia needle and TPC  54 , indicated at  59 . In some methods, the proximal end of TPC  54  (not shown in  FIG. 5E ) can be coupled to an aortic root needle, which has been used to puncture the aorta, supplying a perfusing blood source. This may be a common source of perfusing blood in an open chest procedure.  
         [0043]     In other methods, the proximal end of TPC  54  may be supplied through arterial tubing coupled to the proximal end of TPC  54 . This arterial tubing may be supplied from any suitable source, for example, the femoral artery. This may be a source used in closed chest, minimally invasive procedures. The TPC or arterial tubing may be supplied from the femoral artery and inserted into a closed chest through a simple stab wound or port. Any suitable oxygenated fluid can be used to provide the needed oxygen to the blood vessel undergoing the anastomosis. In a preferred embodiment, distal region  56  is expanded within blood vessel  60 , and perfusing blood is flowing through distal region  56  to prevent or reduce ischemia while the anastomosis is being performed. The anastomosis is represented by sutures  66  in  FIG. 5E . Sutures  66  can be completed entirely around the anastomosis, and sewn completely and tightly to blood vessel  60 . In this example, TPC  54  also acts as a suture guide, allowing conduit  50  to be distally advanced over TPC  54  and to blood vessel  60 . With the anastomosis completed, TPC  54  can be withdrawn. Any problems in withdrawing TPC  54  may be indicative of an anastomosis that has not been correctly performed, and can indicate a problem in the patency of the just-completed anastomosis.  
         [0044]      FIG. 5F  illustrates conduit  50  successfully joined to blood vessel  60  with sutures  66 . In one method, TPC  54  has the distal region in an unexpanded configuration and reduced in profile to enable easier withdrawal of the catheter through the anastomosis and through conduit  50 . With the distal region preferably in the reduced diameter configuration, transconduit perfusion catheter  54  can be withdrawn to proximal region  53  of conduit  50 . Once in the proximal location, in some methods, TPC  54  can once again have the distal region expanded radially, to form a seal within proximal region  53  of conduit  50 . A purse-string suture  63  may be used to seal TPC  54  within conduit  50 . Perfusing blood can once again be supplied through conduit  50  allowing the surgeon to perform other anastomosis. At the appropriate time, proximal region  53  of conduit  50 , and any other similar proximal ends of other conduits, may be joined to a permanent, perfusing blood source, for example, the aorta.  
         [0045]      FIG. 6  illustrates TPC  54  being used in an end-to-end anastomosis, at a stage similar in some respects to that illustrated in  FIG. 5E . TPC  54  been inserted into a proximal end  164  of a blood vessel  160  and expanded to have a larger outer diameter, as previously discussed with respect to  FIGS. 1 through 4 . Perfusing blood has been delivered via an antegrade cardioplegia needle and TPC  54 , indicated at  159 . The anastomosis is represented by sutures  166  in  FIG. 6 . Sutures  166  can be completed entirely around the anastomosis, and sewn completely and tightly to blood vessel  160 . In this example, TPC  54  also acts as a suture guide, allowing conduit  50  to be distally advanced over TPC  54  and to blood vessel  160 . With the anastomosis completed, TPC  54  can be withdrawn.  FIG. 7  illustrates a highly diagrammatic assembly that can be used in some embodiments with TPC  54 . An assembly  80  is shown including generally a valve  86  and a pressurized blood source  88 . In this example, valve  86  is shown disposed between TPC  54  and a piece of arterial tubing  82 . The pressurized blood source can be a manual bulb syringe, a manually operated syringe, or a pressurized or a spring-loaded syringe, which may all optionally have a pressure limiter to limit the pressure of the delivered blood. In the highly diagrammatic example shown in  FIG. 7 , a syringe  90  is shown having a plunger  94  and a pressure limiter  92 . Spring-loaded, pressure limited syringes are known in the art, having been used previously in saphenous vein harvesting.  
         [0046]      FIG. 8  illustrates another highly diagrammatic assembly, similar in some respects to that of  FIG. 7 , and sharing some identically numbered elements that were described with respect to  FIG. 7 . An assembly  180  is shown including generally valve  86  and a pressurized blood source  188 . In this example, valve  86  is shown disposed between TPC  54  and arterial tubing  82 . In the highly diagrammatic example shown in  FIG. 8 , a manual squeeze bulb  190  is shown having pressure limiter  92 .  
         [0047]     The schematic devices in  FIGS. 7 and 8  are not limiting, and are merely intended to illustrate the possibility of a pressure increasing device to provide higher pressure blood than may be possible from the patient&#39;s own aorta or femoral artery. In particular, a higher pressure blood source than the patient&#39;s blood pressure may be necessary if the patient&#39;s blood pressure is too low, or if a higher blood pressure is needed to force blood through the small diameter transconduit perfusion catheter, and past any catheter flow or pressure limiting device, which may be required to expand the outer diameter of the TPC distal region in some devices. Some pressure assist devices have one-way valves distal to, and proximal to, the pressure source, allowing blood to be withdrawn from the patient&#39;s aorta and then injected into the blood vessel undergoing the anastomosis.  
         [0048]     In addition to blood, therapeutic, diagnostic, and gene therapy agents, can be delivered through the transconduit perfusion catheter. The gene therapy agents, for example, DNA, RNA and packaged DNA and RNA can be delivered through the transconduit perfusion catheter.  
         [0049]     All publications, patents and patent documents are incorporated by reference herein, as though individually incorporated by reference. The invention has been described with reference to various specific and preferred embodiments and techniques. However, it should be understood that many various and modifications may be made while remaining within the spirit and scope of the invention.