DOES SEPTAL POSITION AFFECT RIGHT-VENTRICULAR FUNCTION DURING LEFT-VENTRICULAR ASSIST IN AN EXPERIMENTAL PORCINE MODEL

Right ventricular (RV) failure has been a major problem with patients supported by left ventricular (LV) assist devices (LVADs). To assess t he importance of interventricular septal (IVS) position as a mechanism of RV failure, 7 Yorkshire pigs underwent implantation of a Thoratec LVAD. RV function was assessed before and during LVAD operation under differing conditions: (1) with an LV intraventricular latex balloon in flated or deflated to alter NS position and (2) with and without pulmo nary artery (PA) constriction to assess the effect of changes in after load. RV stroke work, RV dP/dt, and RV end-diastolic length did not ch ange significantly with LVAD operation or with changing afterload cond itions. Septal shift was documented as a change in LV shape index (LVS I) calculated using echocardiography. LVSI decreased by 11% when the L VAD was turned on, indicating leftward shifting of the IVS (P=.01). Du ring LVAD support and increased RV afterload, the LVSI decreased by 14 .8% (P=.02). RV cardiac output decreased somewhat during LVAD support. However, RV output was worst when the septal position was normalized using the inflated intraventricular balloon during increased RV afterl oad (P=.05). Unloading by the LVAD of the left ventricle results in a leftward shift of the interventricular septum, which does not appear t o adversely affect RV function. However, during conditions of increase d RV afterload, septal shifting may be beneficial to RV function.