ABC | Volume 113, Nº1, July 2019

Letter to the Editor Kewcharoen & Kanitsoraphan PR interval in cardiac resynchronization therapy Arq Bras Cardiol. 2019; 113(1):109-110 Reply We appreciate the author’s comments on our original article “Baseline Prolonged PR Interval and Outcome of Cardiac Resynchronization Therapy: A Systematic Review and Meta-analysis”. 1 We agree with the authors that the effect of PR interval in cardiac resynchronization therapy (CRT) population is unknown, and therefore we conducted a systematic review and meta-analysis on this topic. We agree that the study by Friedman et al. 2 has the most included participants and has the most percentage in all three forest plots. However, to evaluate the effect of Friedman et al., 2 we performed a sensitivity analysis by excluding one study at a time which is shown in Supplementary Document 2 in the original article. 1 After excluding Friedman et al., 2 there was no significant change of the risk ratio of composite outcome (risk ratio = 1.19, 95% confidence interval: 1.04-1.36), all-cause mortality (risk ratio=1.53, 95% confidence interval: 1.23-1.91), and heart failure hospitalization (risk ratio = 1.6, 95% confidence interval: 1.06-2.42). 1 The meta-analysis pooled result still has a statistically significant risk ratio even if we exclude the study by Friedman et al. 2 Therefore, a prolonged PR interval still predicts the outcomes of CRT regardless of the results of the study by Friedman et al. 2 We appreciate the author’s recommendation to include the study by Stockburger et al. 3 and Lin et al. 4 Both studies were included from our comprehensive search and both full-text articles were reviewed. However, both studies were excluded from our systematic review and meta-analysis for the following reasons. The study by Lin et al. 4 was excluded from our systematic review and meta-analysis due to an inappropriate comparison as demonstrated in Figure 1 of our original article. 1 Their objective is to compare the outcomes between CRT and optimal pharmacologic therapy stratified by PR interval. Our meta-analysis compared the outcome of prolonged PR interval versus normal PR interval only in CRT patients. Similarly, the study by Stockburger et al. 3 was also excluded from our systematic review and meta-analysis due to an inappropriate comparator. Stockburger et al. 3 reported that patients with prolonged PR interval derived clinical benefit with reduction in heart failure or death from CRT when compared to an implantable cardioverter defibrillator. 3 Therefore, their comparison was different from our study, which was prolonged PR interval versus normal PR interval in CRT patients. Our systematic review and meta-analysis used comprehensive search methodology and strict inclusion and exclusion criteria; therefore our results are robust. We showed that a prolonged PR interval in CRT patients is significantly associated with an increased risk for all-cause mortality, composite outcome, and HF hospitalization when compared to normal PR interval in CRT patients. 1 Rattanawong, Pattara Prasitlumkum, Narut Riangwiwat, Tanawan. Kanjanahattakij, Napatt Vutthikraivit, Wasawat 1. Rattanawong P, Prasitlumkum N, Riangwiwat T, Kanjanahattakij N, Vutthikraivit W, Chongsathidkiet P, et al. Baseline Prolonged PR Interval and Outcome of Cardiac Resynchronization Therapy: A Systematic Review and Meta-analysis. Arq Bras Cardiol. 2018;111(5):710-9. 2. Friedman DJ, Bao H, Spatz ES, Curtis JP, Daubert JP, Al-Khatib SM. Association Between a Prolonged PR Interval and Outcomes of Cardiac Resynchronization Therapy: A Report From the National Cardiovascular Data Registry. Circulation. 2016;134(21):1617-28. 3. Stockburger M, Moss AJ, Klein HU, Zareba W, Goldenberg I, Biton Y, et al. Sustained clinical benefit of cardiac resynchronization therapy in non-LBBB patients with prolonged PR-interval: MADIT-CRT long-term follow-up. Clin Res Cardiol. 2016;105(11):944-52. 4. Lin J, Buhr KA, Kipp R. Effect of PR Interval onOutcomes Following Cardiac Resynchronization Therapy: A Secondary Analysis of the COMPANION Trial. J Cardiovasc Electrophysiol. 2017;28(2):185-91. References This is an open-access article distributed under the terms of the Creative Commons Attribution License 110