Abstract 16639: A Longer Qt Interval is Associated with Increased Risk of Atrial Fibrillation
Introduction: Abnormal activity of cardiac late sodium channels leads to increased intracellular calcium, a phenomenon believed to be important in atrial fibrillation (AF). Increased late sodium entry manifests on the 12-lead ECG by prolonging the QT interval. Recent evidence has shown that a longer QT interval is associated with an increased stroke risk, but the mechanism remains unknown. We tested the hypothesis that a longer QT interval predicts incident AF.
Methods: The Atherosclerosis Risk in Communities (ARIC) study is a prospective cohort established in 1986-88. We excluded participants with prevalent AF, left ventricular hypertrophy, prolonged QRS duration, and on QT-prolonging antiarrhythmics at baseline. The QT interval was measured from baseline 12-lead ECGs and was corrected using the Framingham formula (QTFrm). Cox proportional hazards models were used to test associations between baseline QTFrm and incident AF. Results: The 14,188 ARIC participants were 54 ± 6 years old, 56% female, and had a mean baseline QTFrm of 410 ± 16ms. Over 19.7 years of follow-up, 1,418 developed AF. Participants with QTFrm in the 3rd and 4th quartiles had an increased risk of AF compared to those in the 1st (Figure). After adjusting for age, race, sex, body mass index, and cardiac comorbidities, risks associated with the 3rd (hazard ratio [HR] 1.18, 95%CI 1.01-1.38) and 4th (HR 1.49, 95%CI 1.27-1.73) quartiles remained significant. Individuals with an abnormal QTFrm (>450ms for men; >460ms for women) had a 2-fold risk of AF compared to those in normal range, before (HR 2.19, 95%CI 1.53-3.13) and after adjustment (HR 2.12, 95%CI 1.48-3.05). Correcting by Bazett, Fridericia, and Hodge formulas did not meaningfully change the results.
Discussion: A longer QT interval is associated with an increased risk of incident AF. The QT interval may reflect a mechanism responsible for AF, may help explain why a longer QT interval is associated with incident stroke, and may enhance prediction of AF.
- © 2012 by American Heart Association, Inc.