Evaluation of mechanical left ventricular assistance with left atrium to aorta bypass in dogs.

Effects of the left heart bypass (LHB) by the left atrium (LA) to the aorta (AO) shunt on the heart were evaluated by measuring such parameters as tension time index (TTI), diastolic pressure time index (DPTI), DPTI/TTI ratio, coronary blood flow and myocardial oxygen consumption (MVO2) in open-chest dogs. A pneumatically driven bypass pump made of polyurethane was utilized in this study. No significant change of MVO2 was observed with surgical maneuver to connect the LA-AO LHB pump to experimental animals. During synchronous pumping of LHB, TTI decreased by 35%, MVO2 decreased by 56% of the control and DPTI/TTI ratio increased by 79%. However, coronary flow decreased by 35%, presumably due to autoregulation mechanism of the coronary circulatory system. Both synchronous and asynchronous LHB demonstrated the same level of effect in volume unloading. However, significant diastolic augmentation was noted only in the former. LA-AO LHB, which has a sufficient supporting effect and does not damage the ventricular wall, was considered to be very useful for temporary support for the failing heart, especially for postoperative low output state.