Speckle Tracking Imaging in Evaluation of Left Ventricular Mechanics in a Swine Model of Atrioventricular Block during Cardiac Pacing: A Comparison Study with Conventional Right Ventricular Apical Pacing Therapy

Abstract

The purpose of the study was to evaluate the LV mechanics during various cardiac pacing using 2D speckle tracking echocardiography (STE). In eight open‐chest pigs, cardiac pacing was performed at different sites namely right ventricular (RV) apex, RV outflow tract (RVOT) and left ventricular (LV) lateral as well as biventricular (Bi‐V: RV apex + LV lateral) and triangle (Tri‐V: RV apex + RVOT +LV lateral). Changes in LV synchrony and mechanics (longitudinal shortening and twist) were assessed by STE before and after atrioventricular (A‐V) block induced by chemical ablation. During RV apical and LV lateral pacing, a more dyssynchronous LV contraction was observed together with impairment in LV longitudinal shortening and in LV twist before and after A‐V block as compared to RVOT pacing. RVOT and Tri‐V pacing similarly improved the LV longitudinal shortening and twist and decreased the LV dissynchrony as compared to RV apical and bi‐V pacing after A‐V block. The activation pattern of the LV during RVOT and Tri‐V pacing was more similar to the activation pattern of normal heart than that during RV apical and Bi‐V pacing. LV mechanical dissynchrony, LV strain and LV torsion during different cardiac pacing can be assessed by speckle tracking imaging. Our data suggest that RVOT and Tri‐V pacing may serve as a better cardiac resynchronization therapy.