Prognostic implication of baseline PR interval in cardiac resynchronization therapy recipients

Abstract

Background: Prolongation of the baseline ECG PR interval is frequently encountered among cardiac resynchronization therapy (CRT) recipients. There are conflicting data regarding the association of a prolonged PR interval with long-term clinical outcome in this patient group.

Objective: The purpose of this study was to compare clinical outcomes and response to CRT in patients with normal (<200 ms) vs prolonged (≥200 ms) baseline PR interval.

Methods: In this study, 283 patients (normal PR interval: n = 158; prolonged PR interval: n = 125) with documented baseline intrinsic PR interval were followed for 3 years after CRT implantation. The study population consisted of 24.7% women (mean age 66 ± 13 years, left ventricular ejection fraction 24% ± 7%).

Results: A Cox proportional hazard model identified baseline PR interval as a predictor of the composite end-point (all-cause mortality, heart failure hospitalization, left ventricular assist device implantation, and heart transplantation) in univariate analysis (hazard ratio [HR] 1.49, 95% confidence interval [CI] 1.02-2.17, P = .04) but not in multivariate analysis. It also predicted heart failure hospitalization in univariate (HR 1.6, 95% CI 1.1-2.4, P = .02) and multivariate analysis (HR 1.6, 95% CI 1.0-2.3, P = .03). A prolonged PR interval was associated with lower probability of reverse remodeling defined as ≥10% improvement in ejection fraction (64% vs 77%, P = .057), especially in patients with non-left bundle branch block ECG morphology (41% vs 68%, P = .03).

Conclusion: Among patients with CRT, a prolonged baseline PR interval is an independent predictor of worse prognosis and lower probability of reverse remodeling, especially for patients with non-left bundle branch block morphology on ECG.

Keywords: Biventricular pacemaker; Cardiac resynchronization therapy; First-degree atrioventricular block; Heart failure; PR interval.