Effect of leadless left ventricular endocardial and left bundle branch area pacing on biventricular repolarization metrics

BACKGROUND: Cardiac resynchronization therapy (CRT) delivered with left ventricular (LV) epicardial pacing may increase arrhythmic risk through detrimental effects on ventricular repolarization. Leadless LV endocardial CRT including leadless left bundle branch area pacing (LBBAP) may mitigate this by preserving a more physiological transmural activation pattern. OBJECTIVE: This study aimed to evaluate the effect of leadless LV endocardial and leadless LBBAP on repolarization metrics derived from electrocardiographic imaging (ECGi). METHODS: Ten patients with leadless endocardial CRT systems underwent a temporary pacing plus ECGi study, testing right ventricular, LV, and biventricular pacing (BiVP) settings, as well as atrioventricular-optimized LV pacing. Epicardial electrograms were used to derive metrics of repolarization and activation-recovery interval dispersion. The primary outcome measurements were acute improvement (ie, reduction) from baseline (right ventricular pacing or underlying rhythm) of these repolarization metrics. RESULTS: Ten patients were studied; 5 had received LV lateral wall endocardial pacing, and 5 had received LBBAP with leadless septal wall pacing. The optimal leadless pacing setting significantly improved biventricular dispersion of repolarization by 23.7% ± 14% (P < .01), and this effect was more pronounced with LBBAP (29.3% ± 15%, P = .01) vs lateral wall pacing (18% ± 12%, P = .03). Similar results were observed for activation-recovery interval dispersion and biventricular repolarization gradients. The most pronounced improvements were observed where LV-only pacing as opposed to BiVP was used, either through LBBAP or atrioventricular-optimized LV pacing from any endocardial location. CONCLUSION: Optimized leadless LV endocardial lateral wall pacing and LBBAP improve ECGi-derived ventricular repolarization metrics. LV-only pacing seemed superior to endocardial BiVP, potentially reflecting repolarization heterogeneity caused by a collision of 2 paced wavefronts.