The Effect of QRS Duration and Morphology on Cardiac Resynchronization Therapy Outcomes in Mild Heart Failure: Results from the REsynchronization reVErses Remodeling in Systolic left vEntricular dysfunction (REVERSE) Study
Background—Cardiac resynchronization therapy (CRT) decreases mortality, improves functional status and induces reverse left ventricular (LV) remodeling in selected populations with heart failure (HF). We aimed to assess the impact of baseline QRS duration and morphology, and change in QRS duration with pacing, on CRT outcomes in mild HF.
Methods and Results—REVERSE was a multi-center randomized trial of CRT among 610 patients with mild HF. Baseline and CRT-paced QRS durations and baseline QRS morphology were evaluated by blinded core laboratories. The mean baseline QRS duration was 151 ± 23 ms and 60.5% of subjects had left bundle branch block (LBBB). Patients with LBBB experienced a 25.3 ml/m2 mean reduction in left ventricular end-systolic volume index (LVSEVi, p<0.0001), whereas non-LBBB had smaller decreases (6.7 ml/m2 , p=0.18). Baseline QRS duration was also a strong predictor of LVESVi change with monotonic increases as QRS duration prolonged. Similarly, the clinical composite score (CCS) improved with CRT for LBBB subjects (Odds Ratio=0.530, p=0.0034) but not for non-LBBB subjects (Odds Ratio = 0.724, p=0.21). The association between CCS and QRS duration was highly significant (Odds Ratio = 0.831 for each 10 ms increase in QRS duration, p<0.0001), with improved response at longer QRS durations. The change in QRS duration with CRT pacing was not an independent predictor of any outcomes after correcting for baseline variables.
Conclusions—REVERSE demonstrated that LBBB and QRS prolongation are markers of reverse remodeling and clinical benefit with CRT in mild HF.
Clinical Trial Registration—clinicaltrials.gov; Identifier: NCT00271154.
- Received February 2, 2012.
- Accepted June 20, 2012.
- Copyright © 2012, American Heart Association, Inc. All rights reserved. Unauthorized use prohibited