Sustained clinical benefit of cardiac resynchronization therapy in non-LBBB patients with prolonged PR-interval: MADIT-CRT long-term follow-up.

Abstract

In MADIT-CRT, patients with non-LBBB (right bundle branch block or nonspecific ventricular conduction delay) and a prolonged PR-interval derived significant clinical benefit from cardiac resynchronization therapy with defibrillator (CRT-D) compared to an implantable cardioverter defibrillator (ICD)-only. We aimed to study the long-term outcome of non-LBBB patients by baseline PR-interval with CRT-D versus ICD-only. Non-LBBB patients (n=534) were dichotomized based on baseline PR-interval: normal PR (PR<230ms), and markedly prolonged PR (PR≥230ms). The primary end point was heart failure (HF) or death. Secondary end points were HF only and all-cause death. In patients with a prolonged PR-interval, CRT-D treatment related to a 67% significant reduction in the risk of HF/death (HR=0.33, 95% CI 0.16-0.69, p=0.003), 69% decrease in HF (HR=0.31, 95% CI 0.14-0.68, p=0.003), and 76% reduction in the risk of death (HR=0.24, 95% CI 0.07-0.80, p=0.020) compared to ICD-only (median follow-up 5.8years). In normal PR-interval patients, CRT-D therapy was associated with a trend towards increased risk of HF/death (HR=1.49, 95% CI 0.98-2.25, p=0.061), and significantly increased mortality (HR=2.27, 95% CI 1.16-4.44, p=0.014). Significant statistical interaction with the PR-interval was demonstrated for all end points. Results were consistent for QRS 130-150ms and QRS>150ms. In MADIT-CRT, non-LBBB patients with a prolonged PR-interval derive sustained long-term clinical benefit with reductions in heart failure or death from CRT-D implantation, compared to an ICD-only. Our findings support implantation of CRT-D in non-LBBB patients with prolonged PR-interval irrespective of baseline QRS duration.