Autosynchronized systolic unloading during left ventricular assist with a centrifugal pump.

Objectives: The purpose of this study was to investigate how the inflow cannulation site of the left ventricular assist system with a centrifugal pump would influence cardiac function on failing heart models. Methods: In 10 sheep, a left ventricular assist system was instituted by an outflow cannula in the descending aorta, two inflow cannulas in the left atrium and the left ventricle, and connecting those cannulas to a magnetically suspended centrifugal pump. A conductance catheter and a tipped micromanometer for monitoring the pressure-volume loop were also inserted into the left ventricle. Myocardial oxygen consumption was directly measured. Heart failure was induced by injection of microspheres into the left main coronary artery. The assist rate was varied from 0% to 100% at each inflow cannulation site. Results: The pump flow with left ventricular cannulation increased during the systolic phase and decreased during the diastolic phase, whereas it was constant with left atrial cannulation. Ejection fraction with left atrial cannulation decreased as the assist rate increased, whereas that with left ventricular cannulation was maintained up to 75% assist. The external work with left atrial cannulation decreased gradually as the assist rate increased, whereas the external work with left ventricular cannulation did not decrease until the assist rate reached 75%. The myocardial oxygen consumption in both cannulations decreased proportionally as the assist rate increased; they were significantly less with left ventricular cannulation at the 100% assist rate than with left atrial cannulation. Conclusion: Left ventricular cannulation during left ventricular assistance maintains ejection fraction and effectively reduces oxygen consumption.