Preferred left ventricular lead position for upgrade from right ventricular pacing to cardiac resynchronization therapy

Background Cardiac resynchronization therapy (CRT) is a well-established treatment for symptomatic heart failure with electrical dyssynchrony. The left ventricle (LV) lead position is recommended at LV posterolateral to lateral sites in patients with left bundle branch block; however, its preferred region remains unclear in patients upgrading from conventional right ventricular (RV) apical pacing to CRT. We aimed to identify the preferred LV lead position for upgrading conventional RV apical pacing to CRT. Methods This study used electrode catheters positioned at the RV apex and LV anterolateral and posterolateral sites via the coronary sinus (CS) branches to measure the ratio of activation time to QRS duration from the RV apex to the LV anterolateral and LV posterolateral sites during RV apical pacing. We performed simultaneous biventricular pacing at the RV apex and each LV site and measured the differences in QRS duration and LV dP/dt max from those of RV apical pacing. Results This study included 37 patients with anterolateral and posterolateral LV CS branches. During RV apical pacing, the average ratio of activation time to QRS duration was higher at the LV anterolateral site than at the LV posterolateral site (0.90±0.06 vs. 0.71±0.11, p<0.001). The decreasing ratio of QRS duration and the increasing ratio of LV dP/dt max were higher at the LV anterolateral site than at the LV posterolateral site (45.7±18.0% vs. 32.0±17.6%, p<0.001 and 12.7±2.9% vs. 3.7±8.2%, p<0.001, respectively) during biventricular pacing compared with those during RV apical pacing. Conclusions The LV lead position is preferred at the LV anterolateral site in patients upgrading from conventional RV apical pacing to CRT. Condensed abstract Pacing at the latest electrical activation site is crucial to improve electrical dyssynchrony in cardiac resynchronization therapy (CRT). However, the preferred location of the left ventricle (LV) lead position in patients upgrading from conventional right ventricular apical pacing to CRT is unclear. This study aimed to investigate proper strategies for CRT and identify an approach for patients upgrading to CRT. We showed that the preferred location is the LV anterolateral site. Our findings will help cardiologists and clinicians develop better strategies for treating patients with heart failure complicated with atrioventricular block.