Left ventricular bypass pump for cardiac assistance. Clinical experience.

A gas-energized, synchronized, hemispherical pump, of Dacron®-reinforced Silastic®, has been used effectively to relieve the strain on the failing left ventricle during the early recuperative period after open heart surgery. Since 1963, when an early version was implanted in a patient, numerous improvements have been made, among the most important of which has been use of Dacron velour lining to minimize trauma to the blood. Two illustrative cases demonstrate the effectiveness of the pump during relatively sustained use: until the fourth postoperative day in a young girl with long-standing rheumatic heart disease, severe mitral insufficiency and cardiac failure; and until the tenth postoperative day in a woman with severe aortic insufficiency and mitral stenosis who required replacement of both valves. Both patients, critically ill before operation, recovered completely. Experimental and clinical experience indicates that the pump, by immediately reducing left atrial pressure and therefore left ventricular end-diastolic pressure, interrupts the vicious cycle of complex metabolic changes consequent to the hemodynamic disturbances associated with cardiac failure. The need for thoracotomy and the prohibitive cost, however, obviate broad clinical application of the pump. Development of a mechanical device for long-term support or for total cardiac replacement awaits the resolution of several critical problems, including a non-traumatic blood interface, improved control mechanism and portable power source.