Abstract 16639: A Longer Qt Interval is Associated with Increased Risk of Atrial Fibrillation

Abstract

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 (QT_Frm). Cox proportional hazards models were used to test associations between baseline QT_Frm and incident AF. Results: The 14,188 ARIC participants were 54 ± 6 years old, 56% female, and had a mean baseline QT_Frm of 410 ± 16ms. Over 19.7 years of follow-up, 1,418 developed AF. Participants with QT_Frm in the 3^rd and 4^th quartiles had an increased risk of AF compared to those in the 1^st (Figure). After adjusting for age, race, sex, body mass index, and cardiac comorbidities, risks associated with the 3^rd (hazard ratio [HR] 1.18, 95%CI 1.01-1.38) and 4^th (HR 1.49, 95%CI 1.27-1.73) quartiles remained significant. Individuals with an abnormal QT_Frm (>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.