ABC | Volume 111, Nº5, November 2018

Original Article Rattanawong et al PR interval and chronic resynchronization therapy Arq Bras Cardiol. 2018; 111(5):710-719 Table 1 – The clinical characteristics and summary of the included studies First author Freidman Januszkiewicz Kronborg Olshansky Lee Rickard Country of Origin USA USA Denmark USA USA USA Year 2016 2015 2010 2012 2014 2017 Study type Retrospective cohort study Retrospective cohort study Retrospective cohort study Retrospective cohort study Retrospective cohort study Retrospective cohort study Participants description Patients who underwent CRT (LVEF ≤ 35 and QRS ≥ 120) Patients who underwent CRT (LVEF ≤ 35%, QRS > 120, NYHA III, IV) Patients who underwent CRT Patients who underwent CRT (LVEF ≤ 35, QRS ≥ 120 and NYHA III, IV) Patients who underwent CRT (LVEF ≤ 35, QRS ≥ 120 and NYHA III, IV) Patients who underwent CRT (LVEF ≤ 35, QRS ≥ 120) Median duration of follow up (Months) 34 30.1 30 15.95 52.4 61.2 Definition of prolonged PR ≥ 230 ms ≥ 200 ms ≥ 200 ms ≥ 200 ms ≥ 200 ms ≥ 200 ms Number of patients with prolonged PR 2906 125 208 638 204 197 Number of patients with not prolonged PR 15994 158 232 574 199 275 Mean age of patients 75.37 66.00 66.00 65.56 66.72 65.10 confounder adjustment age, race, QRS, Intraventricular conduction, Non ischemic cardiomyopathy, NYHA, HF duration, eGFR, BUN, SBP sex, RBBB, Ischemic cardiomyopathy, AF, medications age, sex, HF aetiology, NYHA, DM, AF, ICD, LVEF age, sex, NYHA, LVEF, LBBB, QRS, HR, SBP, DBP, ischemic status, comorbidities, medication age, sex, ischemic cardiomyopathy, RV size, RV dysfunction, NYHA, MR grade, PASP, medication age, sex, ischemic cardiomyopathy, LVEF, QRS, LBBB, Cr, NYHA AF: atrial fibrillation; BUN: blood urea nitrogen; HF: heart failure; Cr: creatinine; CRT: cardiac resynchronization therapy; DM: diabetes mellitus; DBP: diastolic blood pressure; eGFR : estimated Glomerular infiltration; HR: heart rate; ICD: implanted cardiac defibrillator; LVEF: left ventricular ejection fraction; MR: mitral regurgitation; NYHA: New York Heart Association; PASP: pulmonary artery systolic pressure; RBBB: right bundle branch block; RV: right ventricular; SBP: systolic blood pressure. Table 2 – Newcastle–Ottawa scales of the included studies Study selection comparability outcome representativeness selection of the non‑exposed cohort ascertainment end point not present at start Comparability (confounding) assesment of outcome follow up duration adequacy follow-up total Freidman * * * * ** * * * 9 Januszkiewicz * * * * ** * * * 9 Kronborg * * * * ** * * * 9 Olshansky * * * * ** * * 8 Ying-Hsiang * * * * ** * * * 9 Rickard * * * * ** * * * 9 severe right ventricular dysfunction, and renal diseases. 7,8 The pathophysiology of PR prolongation causing adverse outcomes is explained by decreased ventricular filling time leading to decreased stroke volume. It can also induce ineffective mitral valve closure, causing diastolic mitral valve regurgitation, which is known to be associated with unfavorable outcomes in left ventricular dysfunction. 18 The study results of Gervais et al. 6 show that after CRT placement, there is a marked subsequent shortening of the mean PR interval, which suggests that CRT cures atrioventricular dyssynchrony. 6 However, our result still shows worse outcome among patients with prolonged PR interval compared to normal PR interval. The reasons for PR interval affecting CRT outcome are uncertain. In general, prolonged PR interval reflects either intrinsic intra-atrial or atrioventricular conduction defect. Thus, CRT may facilitate AV synchrony to mitigate diastolic 713