Baseline prolonged PR interval and outcome of cardiac resynchronization therapy: A systematic review and meta-analysis

Background: Recent studies suggest that baseline prolonged PR interval is associated with worse outcome in cardiac resynchronization therapy (CRT). However, a systematic review and meta-analysis of the literature have not been made. Objective: To assess the association between baseline prolonged PR interval and adverse outcomes of CRT by a systematic review of the literature and a meta-analysis. Methods: We comprehensively searched the databases of MEDLINE and EMBASE from inception to March 2017. The included studies were published prospective or retrospective cohort studies that compared all-cause mortality, HF hospitalization, and composite outcome of CRT with baseline prolonged PR (> 200 msec) versus normal PR interval. Data from each study were combined using the random-effects, generic inverse variance method of DerSimonian and Laird to calculate the risk ratios and 95% confidence intervals. Results: Six studies from January 1991 to May 2017 were included in this meta-analysis. All-cause mortality rate is available in four studies involving 17,432 normal PR and 4,278 prolonged PR. Heart failure hospitalization is available in two studies involving 16,152 normal PR and 3,031 prolonged PR. Composite outcome is available in four studies involving 17,001 normal PR and 3,866 prolonged PR. Prolonged PR interval was associated with increased risk of all-cause mortality (pooled risk ratio = 1.34, 95 % confidence interval: 1.08-1.67, p < 0.01, I ² = 57.0%), heart failure hospitalization (pooled risk ratio = 1.30, 95 % confidence interval: 1.16-1.45, p < 0.01, I ² = 6.6%) and composite outcome (pooled risk ratio = 1.21, 95% confidence interval: 1.13-1.30, p < 0.01, I ² = 0%). Conclusions: Our systematic review and meta-analysis support the hypothesis that baseline prolonged PR interval is a predictor of all-cause mortality, heart failure hospitalization, and composite outcome in CRT patients.