Increased cardiac output by downstream pumping with a reversed unidirectional intra-aortic balloon

Downstream and upstream pumping with unidirectional intra-aortic balloons was compared in 8 open-chest normal mongrel dogs anesthetized with pentobarbital. Downstream pumping effect a 32 per cent increase in cardiac index, a 24 per cent decrease in systemic resistance, and a 2 per cent decrease in heart rate. Upstream pumping did not significantly affect these parameters. Mean aorta pressure proximal and distal to the balloon was not altered significantly by pumping in either direction. This unique observation of increased cardiac output may have important implications for the treatment of low output cardiac failure. Preliminary studies including baroreceptor denervation suggest that a reflex mechanism may be involved.