This invention relates to cardiac stabilization devices of the type that are used to stabilize a portion of a beating heart by substantially eliminating movement of a portion of the surface tissue of the heart upon which surgical procedures are to be carried out.
Coronary bypass surgery is a frequently performed cardiac surgery. Approximately 320,000 patients undergo this procedure each year in the U.S. alone. Coronary artery bypass surgery is a technically delicate procedure, and surgeons routinely sew saphenous vein grafts or internal mammary arteries onto coronary arteries as small as one millimeter in diameter. Microsurgical instruments, optical magnification, very fine sutures and fine needles are all necessary to obtain the required precision. In a large majority of procedures the patient is placed on cardiopulmonary bypass as part of the operative procedure. Following commencement of cardiopulmonary bypass, the heart is arrested by the infusion of a cold cardioplegia solution into the coronary arteries and veins. By these means the surgeon is able to operate on a flaccid and motionless heart.
Cardiopulmonary bypass is an expensive and complicated procedure in terms of drug therapy, personnel, equipment and prolonged operation time. It produces metabolic, hematologic and other disturbances to the patient, as well as requiring that the patient receive anticoagulation therapy during the bypass procedure, and reversal of anticoagulant following the cessation of cardiopulmonary bypass. Because of the residual volume of the cardiopulmonary bypass circuit, and the because the patient is anticoagulated, many patients have to receive blood transfusions during or following open heart surgery. Thus, the use of cardiopulmonary bypass has many drawbacks.
Recently, however, methods and apparatus for performing surgery on the beating heart have greatly reduced the trauma of cardiac bypass and other cardiac surgeries. These methods and apparatus are becoming well-known and widely used.
For example, Borst et. al., U.S. Pat. No. 5,836,311, describe these procedures and some forms of apparatus suitable for use in carrying out these surgeries. Borst et. al., describe method and apparatus for temporarily immobilizing a local area of tissue, specifically method and apparatus for temporarily immobilizing a local area of heart tissue to thereby permit surgery on a coronary vessel in that area without significant deterioration of the pumping function of the beating heart. The local area of heart tissue is immobilized to a degree sufficient to permit minimally invasive or micro-surgery on that area of the heart. The Borst et. al. ""311 disclosure features a suction device to accomplish the immobilization. The suction device is coupled to a source of negative pressure. The suction device has a series of suction ports on one surface. Suction through the device causes suction to be maintained at the ports. The device is shaped to conform to the surface of the heart. Thus, when the device is placed on the surface of the heart and suction is created, the suction through the ports engages the surface of the heart. The Borst et. al. suction device is fixed or immobilized to a stationary object, such as an operating table or a sternal or rib retractor. Thus, the local area of the heart near the suction device is temporarily fixed or immobilized relative to the stationary object while suction is maintained. In such a fashion, the coronary artery may be immobilized even though the heart itself is still beating so that a bypass graft may be performed. In addition the suction device may be used in either a conventional, open-chest environment or in a minimally-invasive environment, e.g. endoscopic. Additional disclosures of these methods and devices are found in publications of Borst et. al. and in subsequent Borst et. al. patents, e.g. U.S. Pat. Nos. 5,927,284 and 6,015,378.
Another device of this general type is disclosed in U.S. Pat. Nos. 5,727,569 and 5,906,607 to Benetti et. al. Benetti et. al. disclose A method to minimize the motion of an area of tissue at the outer surface of the beating heart proximate to a coronary artery. The outer surface of the beating heart is contacted with an instrument in an area proximate to a coronary artery. The instrument is comprised of an annular housing having a plurality of suction ports disposed therein and housing is shaped to apply negative pressure at several points about the target area. Means are provided for introducing negative pressure to the suction ports. The position of the instrument is manipulated to rest the plurality of suction ports against the outer surface of the beating heart, and a negative pressure is applied to the beating heart by means for introducing the negative pressure to plurality of suction ports connected at several points over the outer surface of the beating heart. Relative motion of an area of tissue of the beating heart is thereby minimized.
Wright, U.S. Pat. No. 5,782,746, discloses a vacuum actuated device that defines, inter alia, a single vacuum chamber in various configurations, a preferable configuration being a generally U-shaped device. Wright ""746 discloses a vacuum chamber that encloses a resilient porous polymer pad therein, but does not disclose the use of a geometrically stable porous plug in the vacuum chamber. Exemplary of the devices of the prior art, the disclosures of U.S. Pat. No. 5,782,746 are incorporated herein to the same extent as if the patent was repeated here.
Later patents to Swindle et. al., U.S. Pat. No. 5,891,017, and to Sherts et. al., U.S. Pat. No. 5,947,896 disclose variations on the types of devices disclosed in the previously mentioned patents.
The present invention constitutes an improvement over the open cup or multiple cup vacuum devices, all of which tend to raise a welt of tissue on the heart and, thus, cause some trauma to the heart.
The present invention provides a vacuum chamber or plural vacuum chambers which have mounted in the chamber a rigid geometrically stable porous plug of predetermined configuration, which may be, for example, an open cell rigid polymer foam, other rigid foam-like structure, a sintered particle geometrically stable porous plug, or a rigid porous plug formed of fibers or fibrous material. The presently preferred embodiment of the invention utilizes sintered stainless steel, but structures which are geometrically stable and which have sufficient porosity to permit the flow of gas are considered equivalent to porous sintered metal or polymer plugs in the context of this invention. The devices rely on vacuum actuation to enhance the gripping of the geometrically stable porous plug, the geometrically stable porous plug eliminating or minimizing drawing heart tissue into the vacuum cups or chambers. The net result is greater stabilization of the heart and less trauma to the heart tissue.
The present invention is an improved cardiac stabilization device and a method using the same. The invention is an improvement on the type used to stabilize a portion of a beating heart by substantially eliminating movement of a portion of the surface tissue of the heart upon which surgical procedures are to be carried out comprising a housing having an opening that, in use, lies adjacent the heart to define with the heart a vacuum chamber. The improved device further comprises a geometrically stable porous plug structure substantially closing said opening, said geometrically stable porous plug structure having a thickness, said geometrically stable porous plug being porous to air through the thickness thereof. The improved device may also comprise a resilient lip structure surrounding the opening. The geometrically stable porous plug may extend outwardly from the opening in the housing, be recessed inwardly from the opening in the housing or be flush with the opening in the housing.
The invention is also embodied as an improvement in the method of performing cardiac surgery that comprises the steps of immobilizing a portion of the heart upon which surgery is to be conducted by attaching by suction force a vacuum chamber that defines a heart engaging opening to In a portion of the surface of the heart, the improvement being the carrying out of the immobilization step with a vacuum chamber that is substantially closed by a geometrically stable porous plug structure secured in the chamber, the geometrically stable porous plug structure having a thickness and being porous to air through the thickness thereof. The method may be carried out using a geometrically stable porous plug structure substantially closing the opening, the geometrically stable porous plug structure having a thickness, the geometrically stable porous plug being porous to air through the thickness thereof. The improved method may also utilize a vacuum chamber that has a resilient lip structure surrounding the opening. The geometrically stable porous plug may comprise open cell foamed polymer. The geometrically stable porous plug may extend outwardly from the opening in the housing, be recessed inwardly from the opening in the housing or be flush with the opening in the housing.
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