A heart model in dogs was developed to evaluate quantitatively the extent to which left ventricular chamber size could be reduced and yet retain residual mechanical function to perform adequately as a pump. In 9 animals placed on right heart bypass perfusion to control systemic flows, left ventricular performance was estimated from high fidelity left ventricular pressure and aortic flowmeter recordings and from lateral plane left ventricular angiograms. Studies were made during unrestricted left ventricular filling at varying cardiac outputs and with inflation of a balloon in the left ventricular cavity at a physiological cardiac output. As compared with control data (cardiac output 1.4 L. per minute), balloon inflation to 18.7 ml. caused an increase in total left ventricular end diastolic volume (from 35.4 to 44.3 ml., p<0.001) and left atrial pressure (from 7.8 to 21.2 mm Hg, p<0.001); it also caused a reduction in left ventricular stroke work (from 12.5 to 8.1 Gm. M., p<0.005) and max. dp/dt (from 2,487 to 1,320 mm Hg per second, p<0.05). Importantly, left ventricular stroke volume was unchanged. When compared with preload augmentation (with the balloon deflated), the magnitude of depression of cardiac performance caused by balloon inflation was more fully appreciated (left ventricular stroke work, max. dp/dt, and ejection fraction reduced 69, 61, and 45 per cent, respectively). Even so, with appropriate compensations, principally by the Frank Starling mechanism, up to 42 per cent of the left ventricular cavity volume could be functionally eliminated with retention of adequate mechanical performance. Such data may have implications regarding the extent of resections possible in patients undergoing surgery for left ventricular aneurysm.
All Science Journal Classification (ASJC) codes
- Pulmonary and Respiratory Medicine
- Cardiology and Cardiovascular Medicine