Abstract 3577: Right Ventricular Pump Function is Improved by Suboptimal Left Ventricular Resynchronization in Canine LBBB Hearts
Objectives Left ventricular (LV) and biventricular (BiV) pacing improve LV pump function in hearts with left bundle branch block (LBBB), but it is unkown how right ventricular (RV) function is affected. We investigated the hypothesis that during LV-based pacing RV function 1) can improve through mechanical interaction with the LV and 2) can deteriorate due to desynchronization of the RV.
Methods In 11 dogs with LBBB, LV and BiV pacing were performed at atrioventricular (AV) delays of 30–200 ms. RV and LV function were derived from maximum rate of rise (dP/dtmax) of their respective pressures. Interventricular asynchrony (interVA) was determined as time delay between the upslope of LV and RV pressures and RV and LV activation sequence from epicardial multiple electrode mapping.
Results Compared to baseline LBBB, stepwise shortening of AV-delay during LV and BiV pacing improved both RV and LV function until optimal RV function was reached at AV-delays of ~105ms (figure⇓). Further shortening of AV-delay by ~40ms improved LV function to some extent, but this occurred at the expense of RV function. InterVA was −25±3ms at baseline LBBB, decreased to −16±2ms at RV optimum and was −7±2ms (LV pacing) and −9±4ms (BiV pacing ) at LV optimum. Electrical maps showed that RV activation was still normal at RV optimum, but was asynchronous at LV optimum.
Conclusion Resynchronization in LBBB hearts can improve both RV and LV function. Optimal RV and LV function are achieved at different degrees of resynchronization. LV and BiV pacing improve RV function due to direct mechanical interaction with the resynchronized LV as long as RV activation remains synchronous.