Physiology of univentricular versus biventricular support.

Right ventricular failure unresponsive to pharmacologic treatment occurs in approximately 20% to 30% of patients supported with a left ventricular assist device (LVAD). The effect of the assistance on right ventricular function is highly controversial. Increased venous return produced by an LVAD can affect right ventricular function by increasing preload. On the other hand, an LVAD can improve the filling of the right ventricle by unloading the left ventricle, reducing its chamber size and shifting the septum back to the left. Right ventricular function is highly afterload dependent, the ventricular function depending on the pulmonary vascular resistance. With a normal pulmonary vascular bed, the LVAD can improve right ventricular function by reducing right ventricular afterload. If there is a fixed high pulmonary pressure, however, the LVAD can increase right ventricular afterload and volume. We conclude that the right ventricle is dispensable if the pulmonary vascular bed is normal.