The role of interventricular conduction delay to predict clinical response with cardiac resynchronization therapy.

BACKGROUND: Pacing at sites with late electrical activation or greater interventricular delay is associated with improvement in measures of cardiac resynchronization therapy (CRT) response, primarily reverse remodeling. However, little is known about whether such lead positions improve heart failure (HF) clinical outcomes. OBJECTIVE: The purpose of this study was to assess the association between interventricular electrical delay and HF clinical outcomes. METHODS: The Pacing Evaluation-Atrial SUpport Study was a multicenter randomized trial of patients undergoing CRT-defibrillator implantation. Interventricular delay was measured as the unpaced right ventricle-left ventricle (RV-LV) interval in sinus rhythm. The HF clinical composite score was the primary end point. In addition, the time to first HF hospitalization or death was measured and events were adjudicated by a blinded core laboratory. The cohort was divided at the median RV-LV interval into short (<67 ms) and long (≥67 ms) subgroups. In addition, receiver operating characteristic curves were constructed to identify the optimal cutoff of the RV-LV interval and spline analysis was performed to assess RV-LV interval as a continuous variable. RESULTS: A total of 1342 patients were included in this study. The clinical composite score at 1 year differed between groups, with more patients improving and fewer patients worsening in the long RV-LV group (P = .014). The time to first HF hospitalization or mortality also differed with a lower risk of an event in the long RV-LV group (hazard ratio 0.62; P = .002). Multivariate analysis showed that RV-LV time (hazard ratio 0.71; P = .038) and sex were independent predictors of this outcome. CONCLUSION: Baseline interventricular delay is a strong independent predictor of clinical response to CRT.