title: 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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts; Ist Department of Cardiology, Medical University of Warsaw, Warsaw, Poland.
authors.forename: Łukasz
authors.initials: Ł
authors.lastname: Januszkiewicz
authors.affiliation: Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Eszter
authors.initials: E
authors.lastname: Vegh
authors.affiliation: Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Rasmus
authors.initials: R
authors.lastname: Borgquist
authors.affiliation: Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Bose
authors.affiliation: Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Ajay
authors.initials: A
authors.lastname: Sharma
authors.affiliation: Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Mary
authors.initials: M
authors.lastname: Orencole
authors.affiliation: Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Theofanie
authors.initials: T
authors.lastname: Mela
authors.affiliation: Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Jagmeet P
authors.initials: JP
authors.lastname: Singh
authors.affiliation: Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts. Electronic address: KAParks@Partners.org.
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Parks
mesh_terms: D000367:Age Factors; D000368:Aged; D000704:Analysis of Variance; D002037:Bundle-Branch Block / Q000175:diagnosis / Q000401:mortality / Q000628:therapy*; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D016022:Case-Control Studies; D004562:Electrocardiography; D004567:Electrodes, Implanted; D005260:Female; D005500:Follow-Up Studies; D006333:Heart Failure / Q000175:diagnosis / Q000401:mortality* / Q000628:therapy*; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D018570:Risk Assessment; D012737:Sex Factors; D015996:Survival Rate; D016896:Treatment Outcome
keywords: Biventricular pacemaker; Cardiac resynchronization therapy; First-degree atrioventricular block; Heart failure; PR interval