PO-03-088 TWO-DIMENSIONAL SPECKLE TRACKING ECHOCARDIOGRAPHY SHOWS THAT LEFT BUNDLE BRANCH PACING MAINTAINS LEFT VENTRICULAR GLOBAL LONGITUDINAL STRAIN AND CONTRACTILITY COMPARED TO RIGHT VENTRICULAR APICAL PACING

Abstract

Pacemaker-dependent patients with right ventricular (RV) apical pacing are at increased risk for reduced left ventricular function, ventricular dyssynchrony, and the development of pacing-induced heart failure. Physiological pacing of the conduction system through the left bundle branch (LBB) has been shown to have improved synchrony of the ventricles and a more physiological activation sequence. Direct comparison of left ventricular (LV) strain using LBB and RVAP in paired experiments in the same animals or patients has not been published. Evaluate the changes to the left ventricular mechanics (global longitudinal strain (GLS), global circumferential strain (GCS), global radial strain (GRS), and left ventricular ejection fraction (LVEF) through LBB pacing compared to RV pacing using two-dimensional speckle tracking echocardiography. Under anesthesia, six mixed breed hounds had pacing leads from two ICDs (CobaltTM XT DR, Medtronic, Inc) implanted at the RV apex (6947 Sprint Quattro SecureTM, Medtronic, Inc) and the LBB (3830 SelectSecureTM, Medtronic, Inc). Echocardiographic measurements were taken for sinus rhythm, LBB pacing, and RV pacing to evaluate the LV strain, and contractility. Two-dimensional speckle tracking was performed following the pacing procedure to determine GLS, and LVEF from the four-chamber apical views, GCS, and GRS from the short-axis views. In our study, LV GLS was maintained better during LBB pacing when compared to LV GLS during RV pacing. The magnitude of GLS was not significantly different between sinus and LBB pacing, but was significantly lower for RV pacing than both sinus and LBB pacing (Fig. A). GCS only showed a significant difference between sinus and RV pacing (Fig. B), while GRS did not show differences between any of the groups (Fig. C). Results for the LV ejection fraction followed a similar pattern as the GLS. There was not a significant difference in LVEF for sinus and LBB pacing, but LVEF was significantly lower for RV pacing compared to both sinus and LBB pacing (Fig. D). LBB pacing preserves GLS, and the LVEF better than RV apical pacing and is similar to sinus beats. This further supports LBB pacing as a preferred method of pacing for preserving contractility for patients with pacemakers.