In congestive heart failure or CHF, the heart has become so enlarged as a result of viral infection, myocardial infarction or other disease that it is unable to pump at a sufficient rate to maintain adequate circulation of blood throughout the body. As a result, blood backs up into the lungs, causing shortness of breath and other symptoms, and, if left untreated, the disease can lead to death.
For some patients, the CHF may be treated effectively with medication. However, in many cases, the disease progresses to a point at which the patient requires a heart transplant. Unfortunately, due to a donor shortage, of the 40,000 patients who may require a transplant each year, only 2500 actually get one, with up to 15-20% of patients dying while on the waiting list for a donor heart.
In response to the need for alternatives to transplant for treating CHF, a surgical procedure has been tried in recent years known as the xe2x80x9cBatista Operationxe2x80x9d after its developer, Dr. Randas J. V. Batista. In this procedure, a large section of the left ventricular wall is excised from the heart and the wall then sewn back together, thereby reducing the transverse dimension and volume of the left ventricle, the primary pumping chamber of the heart. The reduced volume of the ventricle permits less blood to be present in the chamber during each of its contractions, thus reducing the forces acting against the heart muscle as it contracts and allowing the heart to pump more effectively.
Although the Batista Operation can extend the life of a patient who would otherwise die without a transplant, it is a highly invasive and traumatic procedure. In order to expose the heart, the chest must be opened widely by sawing the sternum in half and spreading apart the rib cage, known as a median sternotomy, producing a great deal of pain, risk of infection, and long recovery time. For elderly or extremely ill patients, the trauma produced by the operation could contribute significantly to the mortality and morbidity associated with the procedure.
Moreover, the Batista Operation has typically been performed while the heart is beating, causing a great deal of blood loss through the ventricular incision, and risking the introduction of air into the bloodstream, potentially causing stroke or other neurological problems. To reduce blood loss and the risk of air embolism, the heart could be stopped and isolated from the rest of the circulatory system during the procedure by placing an external aortic cross-clamp on the ascending aorta and using conventional cardioplegia and cardiopulmonary bypass. However, because such cross-clamps crush the walls of the aorta together in order to occlude the vessel, cross-clamps may produce the added risk of releasing calcific particles from the inner walls of the aorta, which may embolize in the bloodstream and produce neurological events such as stroke. Moreover, the risk remains that air will become trapped in the ventricle after it has been closed, allowing the air to migrate to the brain as soon as the cross-clamp is removed. Conventional cross-clamps also require a large opening in the chest in order to gain access to the aorta, hindering any effort to reduce the trauma associated with the procedure.
What are needed, therefore, are devices and techniques for the surgical treatment of CHF which are less invasive and less risky than the Batista Operation, but which produce the benefits associated with reducing the volume of the left ventricle. The devices and techniques should facilitate the identification of an appropriate section of the left ventricular wall, excision or other reshaping of the section, and, if the section is removed, closure of the left ventricle, without requiring a gross thoracotomy or median stemotomy. If the left ventricle is opened, the devices and techniques should allow the patient to be placed on cardiopulmonary bypass and the heart to be arrested and isolated from the circulatory system without the need for an external aortic cross-clamp. Further, the devices and techniques should minimize that risk that either air and other emboli will be produced by the procedure.
The invention provides devices and methods for treating CHF, as well as other diseases resulting in an enlarged heart, that not only significantly reduce the pain and trauma to the patient, but that may reduce the risk of infection and the risk of neurological events associated with the Batista Operation. The invention facilitates the reduction of left ventricular volume by removing a section of the heart wall or otherwise reshaping the ventricle without requiring a median stemotomy or gross thoracotomy. The invention further allows the procedure to be performed on cardiopulmonary bypass with the heart isolated and arrested, yet without the gross thoracic incision required by, or the risk of embolism produced by, conventional aortic cross-clamps. Moreover, the invention may significantly reduce the risk that air will be introduced into the bloodstream and embolized to the brain during or after the procedure.
In a first embodiment, the invention provides a method of reshaping a patient""s heart, comprising the steps of:
introducing an aortic occlusion catheter through a patient""s peripheral artery, the aortic occlusion catheter having an occluding member movable from a collapsed position to an expanded position;
positioning the occluding member in the patient""s ascending aorta;
moving the occluding member from the collapsed shape to the expanded shape after the positioning step;
introducing cardioplegic fluid into the patient""s coronary blood vessels to arrest the patient""s heart;
maintaining circulation of oxygenated blood through the patient""s arterial system; and
reshaping an outer wall of the patient""s heart while the heart is arrested so as to reduce the transverse dimension of the left ventricle.
The ascending aorta is preferably occluded by means of an occlusion balloon attached to the distal end of an elongated catheter positioned transluminally in the aorta from a femoral, subclavian, or other appropriate peripheral artery. Cardioplegic fluid may then be delivered upstream of the occlusion balloon through a lumen in that catheter, and/or delivered in a retrograde manner through a separate catheter placed transluminally into the coronary sinus from a peripheral vein. While the heart is arrested, circulation of oxygenated blood is maintained preferably by peripheral extraporeal cardiopulmonary bypass (CPB), wherein blood is removed from a peripheral vein via a venous drainage catheter, filtered, oxygenated, and returned to a peripheral artery through an arterial return catheter.
By obviating the need for an aortic cross-clamp, the need for the median sternotomy through which such a cross-clamp is placed is also eliminated. The left ventricle may then be reshaped and volumetrically reduced using thoracoscopic instruments positioned through small incisions, punctures or ports located in the intercostal spaces between the ribs.
The invention further provides a method of reshaping a patient""s heart comprising the steps of:
introducing a tissue attaching device into the patient""s chest;
engaging a first location on a wall of the left ventricle with the tissue attaching device; and
manipulating the tissue attaching device to attach the first location to a second location on a wall of the heart so as to reduce the transverse dimension of the left ventricle, the user""s hands remaining outside the patient""s chest when manipulating the tissue attaching device.
In some embodiments, a section of the left ventricular wall is excised with a cutting device, then the left ventricle is closed using sutures, staples or other means for wound approximation and closure, each applied using thoracoscopic instruments with the user""s hands maintained generally outside of the chest. In other embodiments, a section of the left ventricular wall is gathered together or pursed outwardly or inwardly to produce one or more folds or pleats in the wall. These folds or pleats are then thoracoscopically sutured, stapled or otherwise fastened permanently in place to reduce the transverse dimension of the left ventricle.
In the method of the invention, the left ventricular wall may be approached in several different ways. In one approach, one or more small incisions, punctures, trocar sleeves, tissue retractors or other type of ports are placed in intercostal spaces in the left anterior and/or lateral side of the chest, preferably between the third and seventh intercostal spaces. This permits direct access to the outer wall of the left ventricle on the lateral and posterior sides of the heart, usually with minor retraction of the apex of the heart anteriorly using thoracoscopic graspers or other retraction instruments. The heart may then be viewed directly through an intercostal port, or by means of a thoracoscope positioned through an intercostal port to permit either direct or video-based viewing of the heart.
In a second approach, ports are placed are in the right lateral side of the chest between the third and seventh intercostal spaces. Approaching the heart from the right, an incision is then made in the left atrium on the posterior side of the heart, and the incision retracted to expose the mitral valve. The mitral valve apparatus is excised from the heart, providing access into the interior of the left ventricle through the mitral valve annulus. A thoracoscopic scissors or knife is then used to excise a portion of the left ventricular wall from the inside of the chamber, either under direct vision from a port in the right side of the chest, or under video-based vision using a thoracoscope positioned through a port into the heart. The procedure may be viewed from outside of the heart as well by placing a thoracoscope through a port in the left lateral or anterior side of the chest. The left ventricular wall may then be closed using sutures, staples, or other means applied with an instrument introduced through the mitral annulus from the right chest, or through a port placed in the left lateral or anterior side of the chest as described above.
In still other embodiments, a restrictive girdle or band is placed around the outside of the heart to restrict the left ventricle to the desired diameter or volume. The band or girdle is preferably elastic so as to expand and contract with the heart as it pumps. Preferably, the girdle or band is applied to the heart using specialized thoracoscopic instruments placed through intercostal spaces in the rib cage while generally maintaining the user""s hands outside the chest, thereby eliminating the need for a gross thoracotomy.
Because the chest is not grossly opened, the heart is isolated from the rest of the circulatory system, and in some embodiments, even the ventricle itself is not opened, the methods of the invention may reduce the risk that air will pass through the ventricular incision and into the bloodstream. To reduce this risk even further, the invention also allows the chest to be flooded with carbon dioxide or other suitable gas during the procedure to maintain the chest cavity free of air. A tube may be placed through one of the intercostal ports and gas delivered through the tube into the chest at a pressure suitable to ensure that air cannot enter the chest cavity. Additionally, trocar sleeves or tubular ports may be used which have internal seals like those used for gaseous insufflation in laparoscopic procedures, thereby preventing the unwanted introduction of air into the chest. Further, where some risk of air embolism is present due to the opening of the left ventricle, following closure the left ventricle and aorta may be flushed with saline and then vented through a lumen in the aortic occlusion catheter while maintaining aortic occlusion, thereby removing any trapped air that may be present.