Predictors of super response to left bundle branch area pacing for cardiac resynchronization therapy

Introduction Left bundle branch area pacing (LBBAP), as an alternative strategy to achieve cardiac resynchronization (CRT), has been associated with significant improvements in left ventricular ejection fraction (LVEF) compared to standard biventricular pacing. However, there is little information on the frequency and predictors of super response to LBBAP. Purpose To determine the incidence and predictors of super response in patients undergoing LBBAP for CRT. Methods Patients with heart failure and a LVEF <40% undergoing LBBAP CRT between September 2020 and March 2025 were included. Super response was evaluated using several previously published definitions: 1. An increase in LVEF >10% (SR1); 2. An increase in LVEF >20% (SR2); 3. An increase in LVEF to an LVEF >50% (SR3). Results A total of 230 patients (female 30%, age 69±9.9 years) with a median follow-up of 583 [302-887] days, were included. Super response was observed in a significant proportion of patients, with 51.7% demonstrating SR1, 29.6% SR2, and 23.5% SR3. Patients with SR3 were more often female (51.9% vs. 48.1%, p <0.001), had shorter stimulus to left ventricular activation time (77.6 ± 14.9 vs. 90.4 ± 16.6 ms, p<0.001), higher preprocedural LVEF (31.5±7.6 vs. 25.2±8.3%, p<0.001), shorter left ventricular end diastolic diameter (55±11.1 vs. 60.6±9.8 mm, p 0.001), shorter preprocedural QRS durations (143.3±33 vs. 160.9±33.6 ms, p=0.002), and shorter paced QRS duration (114.4±18.5 vs. 123±18.9 ms, p =0.006). During follow-up, patients with a super response had significantly lower risk of the composite outcome of HF-related hospitalization or all-cause mortality compared to patients without super response (Figure 1), with patients demonstrating either a 20% increase in LVEF or an increase to a final LVEF >50% having the lowest incidence of the composite outcome (log rank p <0.001). Conclusions Super response is observed in a significant proportion of patients undergoing LBBAP CRT. Female sex; preprocedural LVEF, QRS duration and left ventricular end diastolic diameter; as well as shorter stimulus to left ventricular activation times and paced QRS duration, are predictors of super response. During follow-up, patients exhibiting super response have a lower incidence of the composite outcome of all-cause mortality heart failure related hospitalization.