Association of QRS Notch Resolution During LV-Only Fusion Pacing With Early Left Ventricular Reverse Remodeling After Cardiac Resynchronization Therapy.

BACKGROUND: Cardiac resynchronization therapy (CRT) improves outcomes in patients with heart failure and left bundle branch block (LBBB); however, many patients remain non-responders. Identifying effective electrical resynchronization early remains an important clinical need. OBJECTIVE: To investigate the association between resolution of V5-V6 R-wave notching/slurring during left ventricular-only pacing (LV-only pacing), combined with an LV-only pacing percentage ≥ 50% at 1 month, and early left ventricular reverse remodeling in patients with complete LBBB (CLBBB) undergoing CRT. METHODS: We retrospectively studied 49 patients with CLBBB who underwent CRT. Patients with resolution of V5-V6 R-wave notching/slurring during LV-only pacing at implantation and an LV-only pacing percentage ≥ 50% at 1 month were classified as the R-Notch Resolution group; all others were classified as the Non-R-Notch Resolution group. The primary endpoint was left ventricular reverse remodeling at 1 month, defined as a ≥ 15% reduction in left ventricular end-systolic volume (LVESV) from baseline. Logistic regression analysis was performed to identify associated factors. RESULTS: Fifteen patients were classified into the R-Notch Resolution group and 34 into the Non-R-Notch Resolution group. One-month left ventricular reverse remodeling occurred more frequently in the R-Notch Resolution group (80.0% vs. 47.1%). In multivariable logistic regression analysis, R-Notch Resolution group status remained independently associated with 1-month left ventricular reverse remodeling. CONCLUSION: Resolution of V5-V6 R-wave notching/slurring during LV-only pacing, combined with an LV-only pacing percentage ≥ 50% at 1 month, was independently associated with early left ventricular reverse remodeling after CRT.