Chronic effect of left ventricular assist pumping on right ventricular function.

We evaluated right ventricular (RV) function during left ventricular assist device (LVAD) pumping during acute and chronic experiments in both normal hearts and hearts with left ventricular failure. An LVAD was implanted between the left atrium and the descending aorta of goats. The LVAD was pumped in a counterpulsation mode and at maximum bypass flow for 4-6 weeks in chronic experiments. The following results were obtained: 1) LVAD pumping itself did not affect RV function, even after 6 weeks of pumping, 2) the dimensions of the RV free-wall segments measured by sonomicrometers showed a gradual and small increase during the early postoperative days, which was due to an increase in volume returned to the RV and the deformity of the RV cavity derived from reduction in LV volume, and 3) the same tendencies were seen even with LV failure hearts. These results suggested that 1) LVADs can assist not only the LV but also the RV by reducing RV afterload, 2) excessive and prolonged assistance by an LVAD seems to dilate the RV free-wall, and 3) preexisting RV dysfunction is the main cause of signs of RV failure during LV pumping.