Abstract
Introduction: Prolonged PR intervals may impair atrioventricular mechanical coupling and adversely affect cardiac performance. We hypothesize that patients with advanced systolic heart failure, wide QRS complexes, and prolonged PR intervals will have improved survival from cardiac resynchronization therapy with defibrillator (CRT-D) regardless of whether left bundle branch block (LBBB) or non-LBBB is present. Methods: Patients enrolled in the optimal pharmacologic therapy (OPT) and CRT-D arms of the COMPANION trial were included in a multivariable Cox model of all-cause mortality as a function of presence of LBBB and value of PR interval at baseline. Hazard ratios representing the mortality reduction for CRT-D versus OPT were estimated together with pointwise 95% confidence intervals (CIs). Results: A total of 308 OPT and 595 CRT-D patients were included in the analysis. In both the LBBB (n=648) and non-LBBB (n=255) subgroups, the mortality reduction associated with CRT-D compared to OPT was greater with increasingly prolonged baseline PR interval (Figure 1, p=0.02 for each subgroup). Hazard ratios for CRT-D versus OPT (with 95% CIs) for PR intervals of 200ms and 250ms were 0.51 [0.35,0.74] and 0.30 [0.18,0.50] respectively for the LBBB subgroup, and 0.86 [0.50,1.5] and 0.39 [0.18,0.86] respectively for the non-LBBB subgroup. For non-LBBB patients with PR interval ≤200ms, there was no evidence of mortality benefit with CRT-D (p=0.60). Conclusions: In patients with advanced systolic heart failure, wide QRS complexes, and prolonged PR intervals, restoration of atrioventricular mechanical coupling with CRT-D may improve survival in both LBBB and non-LBBB recipients. In patients with non-LBBB, a benefit from CRT-D may occur in patients with prolonged PR intervals. Figure 1: Risk for all-cause mortality by hazard ratios stratified according to PR interval quartiles.
Published Version
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