Hemodynamic evaluation of left ventricular bypass with a homologous cardiac graft

Valid criticisms of orthotopic cardiac transplantation for irreversible left ventricular disease include the removal of a normal or slightly diseased right ventricle in the process and the fact that a number of patients in terminal cardiac failure will not tolerate the procedure because of excessively elevated pulmonary vascular resistance. To overcome these problems, we devised an operation whereby a donor heart is used to bypass the right and left ventricle of the recipient heart, which is left in situ. The functional capacity of both hearts was assessed in 50 baboons after inducing left ventricular failure in the recipient heart by ligating the left anterior descending coronary artery 1.5 cm. from its origin and creating severe supra-aortic stenosis (peak systolic gradient of 80 to 100 mm. Hg). Hemodynamic studies were performed during spontaneous rhythm, after selective fibrillation of the recipient heart, and during synchronous and sequential pacing. It was found that volume load and ventricular compliance and contractility were the major determinants of function of the recipient and donor hearts. Afterload changes played a lesser role. The recipient heart ejection fraction and maximal total cardiac output were significantly improved by sequential pacing with optimalized delays. The operation minimized recipient heart postinfarction arrhythmias, reduced the area of myocardial necrosis, and allowed tolerance of severe supra-aortic stenosis. Low mortality, good donor heart function, and prolonged survival were obtained despite lethal damage to the recipient heart (100 percent of control animals died). Right and left ventricular bypass transplantation, therefore, is a useful variant of orthotopic cardiac transplantation and has been used successfully in seven patients.