Sex-Based Differences in Left Bundle Branch Capture During Left Bundle Branch Area Pacing.

Despite innate differences in QRS duration between males and females, no recommendations have been established to assess for left bundle branch (LBB) capture across different sexes in patients undergoing LBB area pacing (LBBAP). To this end, we performed a retrospective study analyzing postimplant ECGs from 222 patients (143 males/79 females). R-wave peak times (RWPTs), traditionally used to identify LBB capture, were noted to be ∼7 ms shorter in females vs. males, with the differences resolved when accounting for smaller size of female hearts despite no correlation between RWPT and body/heart size. These results argue towards establishing sex-based cutoffs for LBB capture.