Assisted Circulation for the Relief of Right Heart Strain

Early in the development of mechanical pump-oxygenators several workers foresaw their applica- tion to the relief of acute heart failure (Helmsworth, 1952; Constantini, 1953; Newman, 1955; Stuckey, 1957).These attempts were only partially successful, probably because of the physiological upset after prolonged partial body perfusion with the apparatus then available.In the past few years, more experimental work has been done on the effects of prolonged partial heart and lung bypass (Galletti and Salisbury, 1958; Galletti and Brecher, 1960; Wyman et al., 1959) and recently further reports of the clinical application of this technique have appeared (Connolly et al., 1958; Dickson et al., 1960).The present communication describes the effect of partial heart/lung bypass on induced right ventricular and pulmonary arterial hypertension in the dog.EXPERIMENTAL PREPARATIONThis is shown diagrammatically in Fig. 1.Twenty-four adult mongrel dogs were used.Their weights ranged from 7 to 14 kilograms and the animals were anesthetized with intravenous pento- barbitone.An intravenous infusion of 5 per cent dextrose in water containing 50 mg.succinylcholine and 50 milli-equivalents sodium bicarbonate in 200 ml.at a rate of 20-30 drops per minute was given throughout the experiment.Intermittent positive pressure respiration was maintained with a Palmer pump, connected to a Benedict-Roth spirometer on which the oxygen uptake was measured.The heart was exposed through a right thoracotomy and pressures in the aorta, right atrium, right ventricle and pulmonary artery were monitored through catheters connected to Statham P23D strain gauges and recorded on an Ediswan direct writer.The animals were heparinized (3 mg./kilo with a supplementary half dose after 2 hours).Various degrees of pulmonary hypertension were induced by embolizing the pulmonary arterioles with fine glass beads (average diameter-O mm.) injected into the main pulmonary artery.The extra-corporeal circuit was of a capacity to yield up to 60 per cent of the animal's cardiac output.A venous catheter introduced into the inferior vena cava through a femoral vein drained