This invention relates to devices for deploying and securing the ends of bypass grafts designed to provide a fluid flow passage between at least two host vessel regions (or other tubular structure regions). More particularly, the invention relates to bypass grafts that are secured at target host vessel locations thereby producing a fluid flow passage from the first host vessel location through the bypass graft and to the second host vessel location. The bypass grafts and deployment systems of the invention do not require stopping or re-routing blood flow to perform an anastomosis between a bypass graft and a host vessel. Accordingly, this invention describes sutureless anastomosis systems that do not require cardiopulmonary bypass support when treating coronary artery disease.
Current techniques for producing anastomoses during coronary artery bypass grafting procedures involve placing the patient on cardiopulmonary bypass support, arresting the heart, and interrupting blood flow to suture, clip, or staple a bypass graft to the coronary artery and aorta; cardiopulmonary bypass support is associated with substantial morbidity and mortality. The embodiments of the invention position and secure bypass grafts at host vessel locations without having to stop or re-route blood flow. Accordingly, the embodiments of the invention do not require cardiopulmonary bypass support and arresting the heart while producing anastomoses to the coronary arteries. In addition, the embodiments of the invention mitigate risks associated with suturing, clipping, or stapling the bypass graft to the host vessel(s), namely bleeding at the attachment sites and collapsing of the vessel around the incision point.
The invention addresses vascular bypass graft treatment regimens requiring end-end anastomoses and end-side anastomoses to attach bypass grafts to host vessels. The scope of the invention includes systems to position and secure bypass grafts used to treat vascular diseases such as atherosclerosis, arteriosclerosis, fistulas, aneurysms, occlusions, and thromboses. In addition, the systems may be used to bypass stented vessel regions that have restenosed or thrombosed. The bypass grafts and delivery systems of the invention are also used to attach the ends of ligated vessels, replace vessels harvested for bypass grafting procedures (e.g. radial artery), and re-establish blood flow to branching vessels which would otherwise be occluded during surgical grafting procedures (e.g. the renal arteries during abdominal aortic aneurysm treatment). In addition, the invention addresses other applications such as, but not limited to, producing arterial to venous shunts for hemodialysis patients, bypassing lesions and scar tissue located in the fallopian tubes causing infertility, attaching the ureter to the kidneys during transplants, and bypassing gastrointestinal defects (occlusions, ulcers).
Stenosed blood vessels cause ischemia potentially leading to tissue infarction. Conventional techniques to treat partially or completely occluded vessels include balloon angioplasty, stent deployment, atherectomy, and bypass grafting.
Coronary artery bypass grafting (CABG) procedures to treat coronary artery disease have traditionally been performed through a thoracotomy with the patient placed on cardiopulmonary bypass support and using cardioplegia to induce cardiac arrest. Cardiac protection is required when performing bypass grafting procedures having prolonged ischemia times. Current bypass grafting procedures involve interrupting blood flow to suture or staple the bypass graft to the host vessel wall and create the anastomoses. When suturing, clipping, or stapling the bypass graft to the host vessel wall, a large incision is made through the host vessel and the bypass graft is sewn to the host vessel wall such that the endothelial layers of the bypass graft and vessel face each other. Bypass graft intima to host vessel intima apposition reduces the incidence of thrombosis associated with biological reactions that result from blood contacting the epithelial layer of a harvested bypass graft. This is especially relevant when using harvested vessels that have a small inner diameter (e.g. (2 mm).
Less invasive attempts for positioning bypass grafts at target vessel locations have used small ports to access the anatomy. These approaches use endoscopic visualization and modified surgical instruments (e.g. clamps, scissors, scalpels, etc.) to position and suture the ends of the bypass graft at the host vessel locations. Attempts to eliminate the need for cardiopulmonary bypass support while performing CABG procedures have benefited from devices that stabilize the motion of the heart, retractors that temporarily occlude blood flow through the host vessel, and shunts that re-route the blood flow around the anastomosis site. Stabilizers and retractors still require significant time and complexity to expose the host vessel and suture the bypass graft to the host vessel wall. Shunts not only add to the complexity and length of the procedure, but they require a secondary procedure to close the insertion sites proximal and distal to the anastomosis site.
Attempts to automate formation of sutureless anastomoses have led to mechanical stapling devices. Mechanical stapling devices have been proposed for creating end-end anastomoses between the open ends of transected vessels. Berggren, et al propose an automatic stapling device for use in microsurgery (U.S. Pat. Nos. 4,607,637; 4,624,257; 4,917,090; 4,917,091). This stapling device has mating sections containing pins that are locked together after the vessel ends are fed through lumens in the sections and everted over the pins. This stapling device maintains intima to intima apposition for the severed vessel ends but has a large profile and requires impaling the everted vessel wall with the pins. Sakura describes a mechanical end-end stapling device designed to reattach severed vessels (U.S. Pat. No. 4,214,587). This device has a wire wound into a zig-zag pattern to permit radial motion and contains pins bonded to the wire that are used to penetrate tissue. One vessel end is everted over and secured to the pins of the end-end stapling device, and the other vessel end is advanced over the end-end stapling device and attached with the pins. Sauer, et al proposes another mechanical end-end device that inserts mating pieces into each open end of a severed vessel (U.S. Pat. No. 5,503,635). Once positioned, the mating pieces snap together thereby bonding the vessel ends. These end-end devices are amenable to reattaching severed vessels but are not suitable to producing end-end anastomoses between a bypass graft and an intact vessel, especially when exposure to the vessel is limited.
Mechanical stapling devices have also been proposed for end-side anastomoses. These devices are designed to insert bypass grafts, attached to the mechanical devices, into the host vessel through a large incision and secure the bypass graft to the host vessel. Kaster describes vascular stapling apparatus for producing end-side anastomoses (U.S. Pat. Nos. 4,366,819; 4,368,736; and 5,234,447). Kaster""s end-side apparatus is inserted through a large incision in the host vessel wall. The apparatus has an inner flange that is placed against the interior of the vessel wall, and a locking ring that is affixed to the fitting and contains spikes that penetrate into the vessel thereby securing the apparatus to the vessel wall. The bypass graft is itself secured to the apparatus in the everted or non-everted position through the use of spikes incorporated in the apparatus design.
U.S. Surgical has developed automatic clip appliers that replace suture stitches with clips (U.S. Pat. Nos. 5,868,761; 5,868,759; 5,779,718). These clipping devices have been demonstrated to reduce the time required when producing the anastomosis but still involve making a large incision through the host vessel wall. As a result, blood flow through the host vessel must be interrupted while creating the anastomoses.
Gifford, et al provides end-side stapling devices (U.S. Pat. No. 5,695,504) that secure harvested vessels to host vessel walls maintaining intima to intima apposition. This stapling device is also inserted through a large incision in the host vessel wall and uses staples incorporated in the device to penetrate into tissue and secure the bypass graft to the host vessel.
Walsh, et al propose a similar end-side stapling device (U.S. Pat. Nos. 4,657,019; 4,787,386; 4,917,087). This end-side device has a ring with tissue piercing pins. The bypass graft is everted over the ring; then, the pins penetrate the bypass graft thereby securing the bypass graft to the ring. The ring is inserted through a large incision created in the host vessel wall and the tissue piercing pins are used to puncture the host vessel wall. A clip is then used to prevent dislodgment of the ring relative to the host vessel.
The end-side stapling devices previously described require insertion through a large incision, which dictates that blood flow through the host vessel must be interrupted during the process. Even though these and other clipping and stapling end-side anastomotic devices have been designed to decrease the time required to create the anastomosis, interruption of blood flow through the host vessel increases the morbidity and mortality of bypass grafting procedures, especially during beating heart CABG procedures. A recent experimental study of the U.S. Surgical One-Shot anastomotic clip applier observed abrupt ventricular fibrillation during four of fourteen internal thoracic artery to left anterior descending artery anastomoses in part due to coronary occlusion times exceeding 90 seconds (Heijmen, et al. A novel one-shot anastomotic stapler prototype for coronary bypass grafting on the beating heart: feasibility in the pig. J Thorac Cardiovasc Surg. 117:117-25; 1999).
A need thus exists for bypass grafts and delivery systems that are capable of quickly producing an anastomosis between a bypass graft and a host vessel wall without having to stop or re-route blood flow. These anastomoses must withstand the pressure exerted by the pumping heart and ensure blood does not leak from the anastomoses into the thoracic cavity, abdominal cavity, or other region exterior to the vessel wall.
The embodiments of the present invention provide sutureless anastomosis systems that enable a physician to quickly and accurately secure a bypass graft to a host vessel or other tubular body structure. In addition, the invention enables the physician to ensure bypass graft stability, and prevent leaking at the vessel attachment points. The delivery systems of the invention do not require stopping or re-routing blood flow while producing the anastomosis; current techniques require interrupting blood flow to suture, clip, or staple a bypass graft to the host vessel wall.
One aspect of the invention provides fittings designed to exert radial force at the vessel attachment points to maintain bypass graft patency. The fittings may be used to secure biological bypass grafts obtained by harvesting vessels from the patient or synthetic bypass graft materials. When using harvested vessels, fitting embodiments permit everting the harvested vessel to maintain intima to intima apposition between the bypass graft and the host vessel. When using synthetic bypass graft materials, the fittings may be incorporated in the bypass graft design to eliminate the step of attaching the bypass graft to the fitting prior to deploying the bypass graft. The fittings, with bypass grafts attached, are advanced through the delivery system and are secured to the host vessel wall at target locations.
The delivery systems enable inserting the fitting and bypass graft into the host vessel without having to interrupt blood flow through the host vessel. One delivery system embodiment is a combination of tear-away sheath, dilator, guidewire, and needle designed to be inserted into the host vessel at the desired anastomosis site. After attaching the bypass graft to the host vessel, the hub and valve of the tear-away sheath are configured to split so the entire sheath may be separated and removed from around the bypass graft. This facilitates attaching both ends of the bypass graft using the delivery system of the invention and removing the tear-away sheath from around the intact bypass graft. A plunger is used to insert the bypass graft and fitting combination through the sheath and into the host vessel. The plunger also protects the bypass graft during insertion into the host vessel, especially when advancing past the hemostatic valve. As described in co-pending U.S. application Ser. No. 08/966,003 filed Nov. 7, 1997, the dilator and needle may incorporate advanced features, such as steering, sensing, and imaging, used to facilitate placing and locating the bypass graft and fitting combination.
An alternative delivery system involves advancing a fitting embodiment through a puncture in the host vessel wall without the need to stop or re-route blood flow. The fitting may be partially inserted through an incision and rotated past the host vessel wall and into the interior of the host vessel. Additionally, a guidewire may serve as a passage to rotate and advance the fitting into the interior of the host vessel. Once inside the host vessel, the fitting may be secured thereby securing the bypass graft to the host vessel.
In accordance with the invention, fitting embodiments produce anastomoses between harvested vessels and host vessels such that only the endothelial layer of the bypass graft is exposed to blood flow. The invention also describes fittings designed to permit retrograde flow past the anastomosis site so as to maintain flow through the lesion and to branching vessels located proximal to the anastomosis site. A further aspect of the invention provides fittings having branches to accommodate multiple bypass grafts using a single proximal anastomosis.
Further features and advantages of the inventions will be elaborated in the detailed description and accompanying drawings.