Effects of Early Repolarization on Electrocardiography and Long-term Cardiovascular Outcomes: A 15-Year Population-Based Cohort Study

Background: We aimed to investigate the association between persistent early repolarization (ER) in healthy individuals and long-term cardiovascular events and mortality rates in a large cohort study. Methods: Demographic characteristics, medical records, 12-lead electrocardiograms (ECGs), and laboratory data were retrieved and analyzed from the Isfahan Cohort Study. The participants were followed up biannually via telephone interviews and 1 live structured interview in between until 2017. Individuals who had ER in all their ECGs were considered persistent ER cases. Study outcomes were cardiovascular events (unstable angina, myocardial infarction, stroke, and sudden cardiac death), cardiovascular-related mortality, and all-cause mortality. The independent t test, the χ2 test, the Mann-Whitney U test, and the Cox regression models were used for statistical analyses. Results: The study population consisted of 2696 subjects (50.5% female). Persistent ER was found in 203 subjects (7.5%), with a higher frequency in men (6.7% vs 0.8%; P<0.001). Cardiovascular events, cardiovascular-related mortality, and all-cause mortality occurred in 478 (17.7%), 101 (3.7%), and 241 (8.9%) individuals, respectively. After controlling for known cardiovascular risk factors, we found an association between ER and cardiovascular events (adjusted hazard ratio [95% confidence interval] =2.36 [1.19–4.68], P=0.014), cardiovascular-related mortality (4.97 [1.95–12.60], P=0.001), and all-cause mortality (2.50 [1.11–5.58], P=0.022) in women. No significant association was found between ER and any study outcomes in men. Conclusion: ER is common in young men with no apparent long-term cardiovascular risks. In women, ER is relatively rare, but it could be associated with long-term cardiovascular risks.