OPEN-HEART SURGERY

any surgical procedure that requires an incision into the heart, exposing one or more of the cardiac chambers. The most common open-heart operations are for repair of valvular disease and for correction of congenital heart defects, chiefly septal and valve defects. Open-heart surgery has also been used in the treatment of severe coronary-artery disease. Open-heart surgery is performed with the aid of a heart-lung machine, a device that allows circulation and oxygenation of the blood to be maintained outside the patient's body. By this means the surgeon has access to a dry and motionless heart. Until the first such cardiopulmonary bypass devices were developed, most cases of valve disease and congenital defects either were considered inoperable or were corrected by blind (closed-heart) procedures. The first successful open-heart operation using a heart-lung machine was performed by the American surgeon John H. Gibbon, Jr., in 1953. Gibbon used the procedure to close an atrial septal defect, a hole in the wall between the two upper chambers of the heart. Congenital or acquired disease of the mitral valve between the left atrium and left ventricle may also be repaired in an open-heart procedure, often by replacement of the defective valve with an artificial substitute. In such surgery, an incision is made into the wall of the left atrium, thus exposing the mitral valve to the surgeon's view. Defects of the aortic and pulmonary valves, which lead out of the heart, usually can be repaired without opening the heart; replacement of the tricuspid valve between the right atrium and ventricle, although less common than mitral valve surgery, may be performed with open-heart procedures.