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Cheng S, Keyes MJ, Larson MG, et al. Long-term Outcomes in Individuals With Prolonged PR Interval or First-Degree Atrioventricular Block. JAMA. 2009;301(24):2571–2577. doi:10.1001/jama.2009.888
Author Affiliations: Framingham Heart Study, Framingham, Massachusetts (Drs Cheng, Keyes, Larson, Newton-Cheh, Levy, Benjamin, Vasan, and Wang and Ms McCabe); Cardiology Division, Massachusetts General Hospital (Drs Cheng, Newton-Cheh, and Wang and Ms McCabe), Center for Human Genetic Research, Massachusetts General Hospital (Dr Newton-Cheh), Division of Cardiovascular Medicine, Department of Medicine, Brigham and Women's Hospital (Dr Cheng), and Clinical Investigator Training Program, Beth Israel Deaconess Medical Center (Dr Cheng), Harvard Medical School, Boston, Massachusetts; Department of Mathematics and Statistics, Boston University, Boston (Drs Keyes and Larson); Program in Medical and Population Genetics, Broad Institute of Harvard and MIT, Cambridge, Massachusetts (Dr Newton-Cheh); Center for Population Studies, National Heart, Lung, and Blood Institute, Bethesda, Maryland (Dr Levy); Sections of Preventive Medicine and Cardiology, Boston University School of Medicine, Boston (Drs Levy, Benjamin, and Vasan); and Department of Epidemiology, Boston University School of Public Health, Boston (Dr Benjamin).
Context Prolongation of the electrocardiographic PR interval, known as first-degree atrioventricular block when the PR interval exceeds 200 milliseconds, is frequently encountered in clinical practice.
Objective To determine the clinical significance of PR prolongation in ambulatory individuals.
Design, Setting, and Participants Prospective, community-based cohort including 7575 individuals from the Framingham Heart Study (mean age, 47 years; 54% women) who underwent routine 12-lead electrocardiography. The study cohort underwent prospective follow-up through 2007 from baseline examinations in 1968-1974. Multivariable-adjusted Cox proportional hazards models were used to examine the associations of PR interval with the incidence of arrhythmic events and death.
Main Outcome Measures Incident atrial fibrillation (AF), pacemaker implantation, and all-cause mortality.
Results During follow-up, 481 participants developed AF, 124 required pacemaker implantation, and 1739 died. At the baseline examination, 124 individuals had PR intervals longer than 200 milliseconds. For those with PR intervals longer than 200 milliseconds compared with those with PR intervals of 200 milliseconds or shorter, incidence rates per 10 000 person-years were 140 (95% confidence interval [CI], 95-208) vs 36 (95% CI, 32-39) for AF, 59 (95% CI, 40-87) vs 6 (95% CI, 5-7) for pacemaker implantation, and 334 (95% CI, 260-428) vs 129 (95% CI, 123-135) for all-cause mortality. Corresponding absolute risk increases were 1.04% (AF), 0.53% (pacemaker implantation), and 2.05% (all-cause mortality) per year. In multivariable analyses, each 20-millisecond increment in PR was associated with an adjusted hazard ratio (HR) of 1.11 (95% CI, 1.02-1.22; P = .02) for AF, 1.22 (95% CI, 1.14-1.30; P < .001) for pacemaker implantation, and 1.08 (95% CI, 1.02-1.13; P = .005) for all-cause mortality. Individuals with first-degree atrioventricular block had a 2-fold adjusted risk of AF (HR, 2.06; 95% CI, 1.36-3.12; P < .001), 3-fold adjusted risk of pacemaker implantation (HR, 2.89; 95% CI, 1.83-4.57; P < .001), and 1.4-fold adjusted risk of all-cause mortality (HR, 1.44, 95% CI, 1.09-1.91; P = .01).
Conclusion Prolongation of the PR interval is associated with increased risks of AF, pacemaker implantation, and all-cause mortality.
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