Diseases of the cardiovascular system affect millions of people each year and are a leading cause of death throughout the world. The costs to society from such diseases is enormous both in terms of the lives lost and in terms of the cost of treating patients through traditional surgical techniques. A particularly prevalent form of cardiovascular disease is a reduction in the blood supply leading to the heart caused by atherosclerosis or other condition that creates a restriction in blood flow at a critical point in the cardiovascular system that supplies blood to the heart. In many cases, such a blockage or restriction in the blood flow leading to the heart is treated by a surgical procedure known as a Coronary Artery Bypass Graft (CABG) procedure, which is more commonly known as a xe2x80x9cheart bypassxe2x80x9d operation. In the CABG procedure, the surgeon xe2x80x9cbypassesxe2x80x9d the obstruction to restore normal blood flow to the heart by attaching an available source vessel to an obstructed target coronary artery or by removing a portion of a vein or artery from another part of the body, to use as a graft, and by installing the graft at points between a source vessel and a target artery to restore normal blood flow.
Although the CABG procedure has become relatively common, the procedure itself is lengthy and traumatic and can damage the heart, the cardiovascular system, the central nervous system, and the blood supply itself. In a conventional CABG procedure, the surgeon must make a long incision down the center of the chest, cut through the entire length of the sternum, perform several other procedures necessary to attach the patient to a heart-lung bypass machine, cut off the blood flow to the heart, and then stop the heart from beating in order to complete the bypass. The most lengthy and traumatic surgical procedures are necessary, in part, to connect the patient to a cardiopulmonary bypass (CPB) machine to continue the circulation of oxygenated blood to the rest of the body while the bypass is completed.
Although several efforts have been made to make the CABG procedure less invasive and less traumatic, most techniques still require cardiopulmonary bypass (CPB) and cardioplegia (stopping the heart). The safety and efficacy of the CABG procedure could be improved if the surgeon could avoid the need to stop the heart from beating during the procedure, thereby eliminating cardiopulmonary bypass and the lengthy and traumatic surgical procedures necessary to connect the patient to a cardiopulmonary bypass machine to sustain the patient""s life during the procedure. In recent years, a small number of surgeons have begun performing CABG procedures using surgical techniques especially developed so that the CABG procedure could be performed while the heart is still beating. In such procedures, there is no need for any form of cardiopulmonary bypass, no need to perform the extensive surgical procedures necessary to connect the patient to a cardiopulmonary bypass machine, and no need to stop the heart. As a result, the surgery is much less invasive and the entire procedure can typically be achieved through a small number, typically one or two, comparatively small incisions in the chest.
Despite the advantages, the beating-heart CABG procedure is not widely practiced, in part, because of the difficulty in performing the necessary surgical procedures using conventional surgical instruments. If specially designed instruments were available so that the CABG procedure could be performed on the beating heart, the beating-heart CABG procedure would be more widely practiced and the treatment of cardiovascular disease in a significant patient population would be improved.
As noted above, the CABG procedure requires that a fluid connection for restoring the flow of blood be established between two points to xe2x80x9cbypassxe2x80x9d a diseased or obstructed area to restore blood flow to the heart. This procedure is known as an xe2x80x9canastomosis.xe2x80x9d Typically, a source vessel, such as a source artery with an unobstructed blood flow, i.e., the left internal mammary artery (LIMA), or a bypass-graft having one end sewn to an unobstructed blood source such as the aorta, is sewn to a target occluded coronary artery, such as the left anterior descending (LAD) artery or other vessel, that provides blood flow to the muscles of the heart. Because the beating-heart CABG procedure is performed while the heart muscle is continuing to contract and pump blood, the anastomosis procedure is difficult to perform because the heart continues to move while the surgeon is sewing the anastomosis.
The specific part of the surgical procedure that creates the anastomosis in the beating-heart CABG procedure requires placing a series of sutures through extremely small vessels on the surface of the heart and requires completing the anastomosis while the heart muscle continues to beat to pump blood during the procedure. Moreover, the sutures must be carefully placed so that the source vessel or graft is firmly attached when the anastomosis is complete and does not leak when blood flow through the vessel is established. It is also important that the anastomosis procedure be performed rapidly because the blood flow through the target coronary artery may be temporarily interrupted or reduced to avoid excessive blood loss. Also, the working space and visual access are limited because the surgeon may be working through a small incision in the chest or may be viewing the procedure on a video monitor if the site of the surgery is viewed via a surgical scope.
In one current practice, the surgeon places sutures through the heart tissue and, by exerting opposing tension on the sutures, stretches the tissue surrounding the site of the anastomosis to partially reduce the motion of the heart while the anastomosis is completed. This approach is far from ideal. Alternatively, a suction device may be attached to the surface of the heart to fix the motion of the outer layer of surface tissue. In such cases, a suction device typically has several ports incorporated into an instrument that may be attached to the heart to apply a negative pressure to the surface tissue. The negative pressure essentially attaches the surface tissue to the apparatus thereby fixing the position of a portion of the surface of the heart. Such devices are described in co-pending U.S. patent application No. 603,328.
While the negative pressure approach may be effective in fixing a portion of the surface tissue of the heart, the negative pressure applied to cardiac tissue can result in temporary hematomas at the site where the suction ports attach to the tissue. Also, the exterior cardiac tissue is fixed in a configuration defined by the shape of the instrument and the orientation of the suction ports. While the heart continues to beat, the heart muscles are contracting to pump blood, which results in the muscles exerting a force directed away from the exterior tissue fixed by suction.
The beating-heart CABG procedure could be greatly improved if the heart could be stabilized during the procedure such that the motion of the heart, particularly at the site of the anastomosis, is minimized even though the heart continues to beat to supply blood to the body. If effective means for stabilizing the beating heart were available, the beating-heart CABG procedure could be performed more easily, more rapidly, more safely, and with less trauma to the patient.
The advantages provided to a surgeon by the instruments and techniques of the invention allow the beating heart CABG procedure to be performed more rapidly, with less trauma to the patient, and enable a surgeon to perform a CABG procedure without CPB or cardioplegia. This invention provides an alternative approach to a suction apparatus by providing devices and methods for stabilizing the motion of the heart using mechanical instruments specially designed to apply a stabilizing force to the heart to minimize the motion of the beating heart during a surgical procedure. The invention enables a surgeon to readily and rapidly perform a beating-heart CABG procedure thus avoiding the need for cardioplegia or cardiopulmonary bypass. In particular, the methods and devices described herein enable the surgeon to stabilize the heart such that an anastomosis can be more readily accomplished by enabling the surgeon to attach a source vessel or bypass graft to a target coronary artery whose motion is minimized for the duration of the surgical procedure.
Pursuant to the invention, a stabilizing device is introduced through a suitable opening in the chest that provides access to the beating heart. By contacting the heart with the means for stabilizing the beating heart of this invention, and by exerting a stabilizing force on the heart, the motion of the heart caused by the contraction of the heart muscles is effectively eliminated such that movement of the target artery at the site of the anastomosis is minimized. The remainder of the heart may be allowed to contract normally or may have additional devices in place to support the heart or to restrain its motion. Additionally, several of the devices of the invention may be used to position the beating heart to provide an improved surgical field, to maintain the heart in a preferred configuration for surgery, or to rotate the heart to present distinct features of the heart to the surgeon""s visible and accessible surgical field.
An important advantage of this invention is derived from the discovery that a new and effective technique can be described herein and performed in surgery using the devices of the invention to provide an advantageous technique for stabilizing or positioning the beating heart during a surgical procedure. The procedure for stabilizing the beating heart generally requires exerting a stabilizing force on the beating heart using devices constructed as described herein. Typically, in separate steps, the surgeon contacts the heart with at least one component of the means for stabilizing the beating heart of this invention, assesses the degree of movement of the heart, particularly at the site of the surgery, and positions the component of the stabilizing means proximate to the site of the surgery such as a target coronary artery of an anastomosis. With the functional portion of a stabilizing means in place, the surgeon applies a stabilizing force to the beating heart such that the portion of the instrument in contact with the surface of the heart displaces the surface of the heart a sufficient distance that the contraction of the heart does not cause substantial motion, either vertical or horizontal, at the surgery site. The stabilizing force is applied directly or indirectly using at least one component of the stabilizing means of the invention and is comprised of exerting a mechanical force onto the beating heart, generally at a specific location such as a target coronary artery and generally exerting force that is at least partially applied in a direction perpendicular to the surface of the beating heart. Thus, an important aspect of this invention is the discovery that the beating heart may be effectively stabilized for the purpose of a surgical procedure by using a specially designed instrument as described herein to exert a mechanical stabilizing force on the exterior of the heart, particularly where the force is exerted proximate to the site of the surgery. The stabilizing force may consist of a force that resists the motion supplied by the beating heart, or additional forces applied to the heart, or the stabilizing force.
By fixing the position of the stabilizing means in a configuration where the motion of the beating heart is effectively eliminated, the surgeon maintains the stabilizing force on the beating heart for the duration of the procedure. To fix the position of the means for stabilizing the beating heart, the stabilizing means may be attached to a retractor used to separate the ribs or to another fixed support. The stabilizing means may also be attached to a comformable, flexible, or semi-rigid arm or shaft means which is rendered substantially rigid mechanically, chemically, or by human intervention. In certain preferred embodiments, the stabilizing means has an adjustable shaft means which may be oriented in several directions and has a fixture adapted to be attached to a retractor. In a preferred technique of the invention, the surgeon first performs a thoracotomy and retracts the ribs using a retractor, which may then be locked in an open position providing access to the beating heart. The surgeon then contacts the surface of the heart with a component of the stabilizing means, which has been provided with an adjustable shaft, at a point proximate to the target coronary artery, and exerts a stabilizing force on the means for stabilizing the beating heart. By manipulating the adjustable shaft, the site of the surgery will become substantially motionless.. This force may be advantageously applied, and the absolute amount of force minimized with the additional feature of an adhesive or high-friction surface on the component of the stabilizing means that contacts the beating heart. At this point, the adjustable shaft means is fixed in position, for example by being stably attached to the retractor, thereby rendering the target coronary artery substantially motionless for the duration of the procedure.