Surgery – Instruments – Electrical application
Reexamination Certificate
2002-02-05
2004-03-02
Cohen, Lee (Department: 3739)
Surgery
Instruments
Electrical application
C606S045000, C606S041000
Reexamination Certificate
active
06699245
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to medical devices and methods for welding biological tissue. In particular, the invention relates to performing a vascular anastomosis and, more particularly, to preferred devices and methods for sealingly joining a graft vessel, such as a coronary bypass graft, to the side wall of a target vessel, such as the aorta or a coronary artery, in an anastomosis.
BACKGROUND OF THE INVENTION
A wide variety of medical procedures involve creating an anastomosis to establish fluid communication between two tubular conduits or organs in a patient. Coronary artery bypass graft (CABG) surgery, for example, often involves creating an anastomosis between blood vessels or between a blood vessel and a vascular graft to create or restore a blood flow path to the heart muscles. Such CABG surgery is necessary to overcome coronary artery disease, wherein plaque build-up on the inner walls of the coronary arteries causes narrowing or complete closure of these arteries. This results in insufficient blood flow and deprives the heart muscle of oxygen and nutrients, leading to ischemia, possible myocardial infarction, and even death. CABG surgery may be performed via a traditional open-chest procedure or a closed-chest or port-access thoracoscopic procedure.
CABG surgery may require the creation of one or more anastomosis depending upon whether a “free graft” or a “pedicle graft” is employed. A “free graft” is a length of conduit having open proximal and distal ends. A proximal anastomosis is required to connect the proximal end of the graft to a source of blood (e.g. the aorta) and a distal anastomosis is required to connect the distal end of the graft to the target vessel (e.g. a coronary artery). Free grafts may be autologous, such as by harvesting a saphenous vein or other venous or arterial conduit from elsewhere in the body, or an artificial conduit, such as Dacron or Goretex tubing. A “pedicle graft” is the result of rerouting a less essential artery, such as the internal mammary artery, from it native location so that it may be connected to the coronary artery downstream of the blockage. The proximal end of the graft vessel remains attached in its native position and only one anastomosis is required to connect the distal end of the graft vessel to the target vessel. In either case, the anastomosis may be between the end of the graft and an aperture in the side wall of the source or target vessel (a so-called “end-to-side” anastomosis) or the anastomosis may be between an aperture in the side wall of the graft and an aperture in the side wall of the source or target vessel (a so-called “side-to-side” anastomosis).
Current methods available for creating an anastomosis include hand suturing the vessels together. Connection of interrupted vessels with stitches has inherent drawbacks. For example, it is difficult to perform and requires great skill and experience on the part of the surgeon due in large part to the extremely small scale of the vessels. Coronary arteries typically have a diameter in the range of between about 1 to 5 mm, and the graft vessels have a diameter on the order of about 1 to 4 mm for an arterial graft such as a mammary artery, or about 4 to 8 mm for a vein graft such as a saphenous vein. In closed-chest or port access procedures, the task of suturing is even more challenging due to the use of elongated instruments positioned through the access ports for approximating the tissues and for holding and manipulating the needles and sutures used to make the anastomoses. Other drawbacks of connection with stitches are the long duration of the operation, during which period in conventional open-heart CABG surgery the heart is arrested and the patient is maintained under cardioplegic arrest and cardiopulmonary bypass. Cardiopulmonary bypass has been shown to be the cause of many of the complications that have been reported in conventional CABG, such as stroke. The period of cardiopulmonary bypass should be minimized, if not avoided altogether, to reduce patient morbidity.
One approach to coronary artery bypass grafting that avoids cardiopulmonary bypass is performing the suturing procedure on a beating heart. At present, however, safe, reproducible, and precise anastomosis between a stenotic coronary artery and a bypass graft vessel presents numerous obstacles including continuous cardiac translational motion which makes meticulous microsurgical placement of graft sutures extremely difficult. The constant translational motion of the heart and bleeding from the opening in the coronary artery hinder precise suture placement in the often tiny coronary vessel.
The above mentioned drawbacks of hand suturing have led to the development of various approaches to stichless vascular anastomosis. One approach involves the use of rigid rings, such a described in Geotz et al., INTERANL MAMMARY-CORONARY ARTERY ANASTOMOSIS-A Nonsuture Method Employing Tantalum Rings, J. Thoracic and Cardiovasc. Surg. Vol. 41 No. 3, 1961, pp. 378-386. This anastomosis method uses polished siliconized tantalum rings that are circumferentially grooved. The free end of the internal mammary is passed through a ring chosen according to the size of the stenotic coronary artery. The free end of the mammary artery is everted over one end of the ring as a cuff and fixed with a silk ligature that is tied around the most proximal of the circular grooves in the ring. The cuffed internal mammary artery is inserted into an incision in the target coronary artery. The ring is fixed in place and sealingly joined to the target coronary artery by tying one or more sutures circumferentially around the target vessel and into one or more circular grooves in the ring. An intimal-to-intimal anastomosis results and dissection of blood between the coronary artery and the cuffed internal mammary artery is largely prevented.
Other ring-related anastomotic approaches include that disclosed in Carter et al., Direct Nonsuture Coronary Artery Anastomosis in the Dog, Annals of Surgery, Volume 148, No. 2, 1958, pp. 212-218, and U.S. Pat. No. 4,624,257 to Berggren et al. However, no permanently satisfactory results have been reported with the use of rigid rings. A rigid ring presents a foreign body of relatively heavy weight which does not heal well and produces pressure necrosis. Moreover, the use of rigid rings that completely encircle the graft vessel and the arteriotomy creates a severe “compliance mismatch” relative to both the coronary artery and the graft vessel and the anastomosis site which could lead to thrombosis. That is, recent studies suggest that the anastomosis site should not be dramatically different in compliance relative to either the coronary artery or the vascular graft, which is the case when using rigid rings to sealingly join two vessels together.
Other attempts at stitchless anastomosis involve the use of stapling devices. For example, U.S. Pat. No. 4,350,160 discloses a vascular stapling device for creating an end-to-end anastomosis between the internal mammary artery (IMA) or a vein graft and one of the coronary arteries, primarily the left anterior descending coronary artery (LAD). However, this device can only perform end-to-end anastomoses such that the coronary artery must first be severed and dissected from the surrounding myocardium and the exposed end everted for attachment. This technique is limited to cases where the coronary artery is totally occluded and there is no loss of blood flow by completely severing the coronary artery downstream of the blockage to make the anastomosis. Consequently, this device is not applicable where the coronary artery is only partially occluded and is not at all applicable to making the proximal side-to-end anastomosis between a bypass graft and the aorta.
U.S. Pat. No. 5,234,447 discloses a vascular stapling device for end-to-side vascular anastomoses. A ring-shaped staple is provided having legs extending from the proximal and distal ends of the ring for joining two blood vessels together in an end-to-side anastomosis.
Charbonneau Paul
Dinger Fred
A-Med Systems, Inc.
Cohen Lee
Roane Aaron
Ryan Kromholz & Manion S.C.
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