Effects of left ventricular pressure unloading during LVAD support on right ventricular contractility.

The effects of left ventricular pressure (LVP) unloading with a left ventricular assist device (LVAD) on right ventricular (RV) end-systolic pressure volume relationships were studied. A Thoratec (Berkeley, CA) LVAD was implanted in open chest anesthetized pigs via apical cannulation, and an electromagnetic flow probe and computer controlled pneumatic occluder were attached to the pulmonary artery. RV and left ventricular (LV) pressures were measured with Millar catheters, and changes in RV volume during ejection were determined by integrating the flow signal. As an index of contractility, RV maximal systolic elastance (Emax) was calculated as the slope of the end systolic, pressure volume relationship between an isovolumic beat and a series of transiently occluded beats at different times in the ejection phase. After an 83 +/- 15% decrease in LV pressure time integral during LVAD pumping, there were no significant changes in cardiac output, mean systemic arterial pressure, or in RV dP/dtmax. Most important, RV Emax during LVAD unloading (0.63 +/- 0.16 mmHg/ml) was unchanged from control (0.62 +/- 0.10 mmHg/ml). Therefore, in the normal intact porcine heart, the effective contractility of the right ventricle is not altered by significant LV pressure unloading produced with a LVAD.