Clinical Characteristics and Outcomes Associated With the Natural History of Early Repolarization in a Young, Biracial Cohort Followed to Middle Age

BACKGROUND: Early repolarization (ER), a common electrocardiographic phenotype, has been associated with increased mortality risk in middle-aged adults. Data are sparse on long-term follow-up and outcomes associated with ER in younger adults. METHODS AND RESULTS: We prospectively examined 5039 participants (mean age, 25 years at baseline, 40% black) from the Coronary Artery Disease Risk in Adults (CARDIA) cohort for 23 years. Twelve-lead ECGs were recorded and analyzed at years 0, 7, and 20 and coded as definite or probable ER using a standardized algorithm. Cox regression was used, and models were adjusted for important baseline and clinical covariates. Kaplan-Meier curves were created for presence of ER and total mortality and cardiovascular mortality. Participants with ER were more likely to be black, male, smoke, have higher systolic blood pressure, lower heart rate and body mass index, higher exercise duration, and longer PR, QRS, and QT intervals. ER was associated with total mortality (hazard ratio, 1.77; confidence interval, 1.38-2.28; P<0.01) and cardiovascular mortality (hazard ratio, 1.59; confidence interval, 1.01-2.50; P=0.04) in unadjusted analyses, but adjustment for age, sex, and race attenuated associations almost completely. Sex-race stratified analyses showed no significant associations between ER and outcome for any of the subgroups except blacks. CONCLUSIONS: The presence of ER at any time point during 23 years of follow-up was not associated with adverse outcomes. Black race and male sex confound the unadjusted association of ER and outcomes, with no race-sex interactions noted. Additional studies are necessary to understand the factors associated with heightened risk of death in those who maintain ER into and beyond middle age.