[Towards a non-invasive left-ventricular assisted circulation. Experimental study].

Abstract

An original system of closed chest direct left ventricular circulatory assistance was assessed in the dog. The system comprises a compact centrifugal pump, a left ventricular cannula for aspiration and an arterial cannula for reinjection of the blood. The cannulae may be introduced by retrograde arterial catheterisation, the first by retrograde transaortic catheterisation and the second positioned in the descending thoracic aorta. This circuit was evaluated in a dog model of acute myocardial infarction involving 39+/-8 p. 100 of left ventricular mass. Mechanical circulatory assistance maintained an extracorporeal output (78+/-5 ml/min/kg) identical to the cardiac output measured immediately beforehand. Left ventricular emptying was complete (LVEDP = -2.3+/-2.5 torr), its external work becoming nil. The pulmonary artery pressure (13.1+/-0.8 torr) and pulmonary artery resistances (311+/-28 dynes/cm.s-5) were significantly lower, whilst no increase in systemic resistance was observed (3 134+/-300 dynes/cm.s-5). During the new haemodynamic equilibrium St segment elevation at the centre and at the edge of the cyanosed myocardium was significantly reduced to (p < 0.05). Irreduceable ventricular fibrillation at coronary artery ligature occurred in two animals. Spontaneous reversion to sinus rhythm was observed when circulatory assistance was started. Termination of left ventricular circulatory assistance after 2 hours was accompanied by a significant (p < 0.005) fall in cardiac index (59+/-7 ml/min/kg), increase in left ventricular filling pressure (LVEDP 7.8+/-1.8 torr), increase in systemic resistance (3 803+/-404 dynes/cm.s-5). The electrical changes of myocardial ischemia worsened (p < 0.005). No valvular or parietal complications of cannulization were observed. This protocol shows the practical value of the original left ventricular circulatory assistance circuit described. The results suggest that a significant reduction of myocardial ischemia due to coronary artery ligature may be achieved by this means. a clinical trial of the value of this extra corporeal circulatory assistance in the treatment of cardiogenic shock is suggested.