Simultaneous His Bundle and Left Ventricular Pacing for Optimal Cardiac Resynchronization Therapy Delivery: Acute Hemodynamic Assessment by Pressure-Volume Loops.

Background: Previous studies have investigated the role of intrinsic conduction in optimizing cardiac resynchronization therapy. We investigated the role of fusing pacing-induced activation and intrinsic conduction in cardiac resynchronization therapy by evaluating the acute hemodynamic effects of simultaneous His-bundle (HIS) and left ventricular (LV) pacing.

Methods And Results: We studied 11 patients with systolic heart failure and left bundle-branch block scheduled for cardiac resynchronization therapy implantation. On implantation, LV pressure-volume data were determined via conductance catheter. Standard leads were placed in the right atrium, at the right ventricular apex, and in a coronary vein. An additional electrode was temporarily positioned in the HIS. The following pacing configurations were systematically assessed: standard biventricular (right ventricular apex+LV), LV-only, HIS, simultaneous HIS and LV (HIS+LV). Each configuration was compared with the AAI mode at multiple atrioventricular delays (AVD). In comparison with the AAI, right ventricular apex+LV and LV-only pacing resulted in improved stroke volume (85±32 mL and 86±33 mL versus 58±23 mL; P<0.001), stroke work, maximum pressure derivative, and systolic dyssynchrony at individually optimized AVD. The optimal AVD was close to the P-H interval in the majority of patients. By contrast, HIS-LV pacing improved hemodynamic indexes at all AVD (stroke volume >76 mL at all fixed intervals and 88±31 mL at optimal interval; all P<0.001).

Conclusions: Standard right ventricular apex+LV and LV-only pacing enhanced systolic function and LV synchrony at individually optimized AVD close to the measured intrinsic P-H interval. By contrast, HIS+LV pacing yielded improvements, regardless of AVD setting. These findings support the hypothesis of the crucial role of intrinsic right ventricular conduction in optimal cardiac resynchronization therapy delivery.