Optimization of Nonresponders to Left Bundle Branch Area Pacing Using Electrical Dyssynchrony Mapping

BACKGROUND Left bundle branch area pacing (LBBAP) is a new approach to resynchronization in heart failure (HF) patients. Treatment of LBBAP nonresponders by optimizing programming has not been studied. OBJECTIVE Assess effects of optimization on LV size and systolic function in LBBAP nonresponders. METHODS We studied 41 systolic HF patients with attempted LBBAP 6.5 ± 4.3 months post-implantation. Nonresponders (pre-CRT EF <45% and increase in EF <5%) and incomplete responders (increase in EF >5% but final EF < 45%) to LBBAP were included. Electrical dyssynchrony was assessed by a novel measure called cardiac resynchronization index (CRI). Patients with R waves in V1 were classified as left bundle branch pacing (LBBP) and those without R waves in V1 as deep septal pacing (DSP). Patients were programmed to optimal AVD, VVD and pacing mode (LBBAP-only, BiV or LV-only). Echocardiograms before CRT, before optimization and 8.2±4.4 months after optimization were read in blinded fashion. RESULTS Most patients had LV leads (90.2%). LBBP was present in 41.5%, and DSP in 58.5% of patients. CRI increased from 59.8±25.9% to 84.5±16.7%. CRT optimization significantly improved left ventricular EF from 34.0±7.0% to 37.0±6.4% (p<0.0001), end-systolic volume (LVESV) from 83.1±38.9 to 72.7±35.5 mL (p<0.001), end-diastolic volume (LVEDV) from 124.9±46.3 to 112.9±46.8 mL (p<0.001), and global longitudinal strain (GLS) from -10.5±3.2 to -11.5±3.0 (p=0.01). CONCLUSION CRT programming to optimal CRI significantly improves LV systolic function, LVESV, LVEDV and LV GLS in nonresponders and incomplete responders to LBBAP, offering a non-invasive, practical clinical approach to improving response in LBBAP patients.