J-Shaped Association Between QTc Interval Duration and the Risk of Atrial Fibrillation Results From the Copenhagen ECG Study

Objectives The aim of this study was to investigate whether the heart rate-corrected QT (QTc) interval on the electrocardiogram (ECG) is associated with the onset of atrial fibrillation (AF). Background Patients with hereditary short-QT or long-QT syndromes, representing the very extremes of the QT interval, both seem to have a high prevalence of AF. Methods A total of 281,277 subjects were included, corresponding to one-third of the population of the greater region of Copenhagen. These subjects underwent digital ECG recordings in a general practitioner's core facility from 2001 to 2010. Data on drug use, comorbidities, and outcomes were collected from Danish registries. Results After a median follow-up period of 5.7 years, 10,766 subjects had developed AF, of whom 1,467 (14%) developed lone AF. Having a QTc interval lower than the first percentile (<= 372 ms) was associated with a multivariate-adjusted hazard ratio of 1.45 (95% confidence interval: 1.14 to 1.84; p = 0.002) of AF, compared with the reference group (411 to 419 ms). From the reference group and upward, the risk of AF increased with QTc interval duration in a dose-response manner, reaching a hazard ratio of 1.44 (95% confidence interval: 1.24 to 1.66, p < 0.001) for those with QTc intervals >= 99th percentile (>= 464 ms). The association with respect to longer QTc intervals was stronger for the outcome of lone AF, as evidenced by a hazard ratio of 2.32 (95% confidence interval: 1.52 to 3.54, p < 0.001) for having a QTc interval >= 99th percentile (>= 458 ms). Conclusions In this large ECG study, a J-shaped association was found between QTc interval duration and risk of AF. This association was strongest with respect to the development of lone AF. (C) 2013 by the American College of Cardiology Foundation