[Design and haemodynamic evaluation of the ellipsoid heart for total heart replacement]

Thromboembolism is a complication which represents a major limiting factor in animals with long-term postoperative survival periods following total artificial heart replacement. Thrombi are formed on the artificial valves, the biomaterials and in stagnation areas within the artificial ventricles. In design planning the stagnation areas should be avoided as well as major turbulences. The filling volume should be maximally used for the stroke volume and the epicenter of the membrane should be underneath the valve areas. The ellipsoid heart eliminates stagnation areas and the stroke volume is 82% of the filling volume. The maximum cardiac output is 15.8 l/min. The ellipsoid heart was implanted in 20 female calves; the maximum length of survival was 213 hours. There was no compression of the inferior vena cava and the heart fitted well into the chest of the animals. The cardiac output, self-regulated in the sense of Starling's law, was adequate to perfuse the animals and to allow moderate exercise such as standing. The arterial pressure curves show normal physiological activity. The curves in both atria are unphysiological, owing to relative insufficiency of the valves. The limiting factors were pulmonary insufficiency and surgical complications. The ventricles showed no thrombus formation -- except in one case, in which faulty material was the predisposing cause. It was possible to develop an automatic driving system on the basis of these experiments. Regulation occurred by means of gas flow control in the driving tubes, whereby the form of the gas flow curve provides information on position of the membrane. As soon as the membrane has reached the end-diastolic position, systole is triggered off and lasts until the end-systolic position is reached. If the venous return is increased, the ventricles are filled more rapidly and the heart is driven at a higher rate. One part of the ellipsoid heart is used as ventricle for assisted circulation. The left ventricle is cannulated via the left appendage or the apex. The ventricle relieves the left heart to a large extent and the cardiac output is taken over by the pump placed in a paracorporeal position. The blood is directed back into the thoracic aorta.