Adaptive CRT in patients with normal AV conduction and left bundle branch block: Does QRS duration matter?

Background Adaptive cardiac resynchronization therapy (aCRT) is a dynamic optimization algorithm which paces only the left ventricle (LV) when atrio-ventricular (AV) conduction is normal, thus reducing right ventricular (RV) pacing. However, the impact of QRS duration on aCRT efficacy remains uncertain. We examined whether QRS duration impacts aCRT effectiveness in patients with left bundle branch block (LBBB) and preserved AV conduction. Methods Randomized patients in the Adaptive CRT trial, which enrolled NYHA III/IV patients, were used in this analysis. Patients were randomized to receive aCRT or echo-optimized bi-ventricular CRT (control arm). Endpoints for this analysis were clinical composite score (CCS) at 6 months post-implant and time to first heart failure (HF) hospitalization or death. Results Among the 199 patients with LBBB and normal AV intervals at baseline, 80 patients (40%) had a baseline moderately wide QRS of 120–150 ms. In this subgroup, a greater proportion of aCRT patients had an improved CCS (79% vs. 50%) at 6 months compared to the control group (p = 0.03). There was also a trend toward a lower risk of death or HF hospitalization (hazard ratio: 0.53; 95% CI: 0.24–1.15; p = 0.10) in the moderately wide QRS subgroup with aCRT compared to the control arm. In the wide QRS subgroup, the efficacy was comparable in both treatment arms. Conclusion Adaptive CRT was associated with improved patient outcomes over echo-optimized bi-ventricular CRT in patients with preserved AV conduction, LBBB, and moderately wide QRS. The adaptive cardiac resynchronization therapy trial (ClinicalTrials.gov Identifier: NCT00980057) was sponsored by Medtronic plc, Mounds View, MN.