Abstract 3455: Clinical correlates and heritability of QT interval duration in African Americans: the Jackson Heart Study
Electrocardiographic QT interval prolongation is a risk factor for sudden cardiac death (SCD) in patients with long-QT syndrome, myocardial infarction or drug-induced arrhythmias as well as in apparently healthy individuals. The clinical covariates and heritability of the QT interval duration (QT) in African Americans have not been well studied despite their higher risk for SCD compared to non-Hispanic whites. The objective of this research was to investigate potential determinants of QT in the Jackson Heart Study (JHS). After excluding JHS participants on QT-altering medications, with bundle branch block, paced rhythm, atrial fibrillation/flutter or other arrhythmias, 4660 individuals were eligible for analyses. The relation between QT and potential covariates was tested using multivariable stepwise linear regression (LR). Heritability was estimated using SOLAR in a subset of 1297 JHS participants in 292 families. When individually added to models already containing age, sex and RR interval (RR) as predictors of QT, the following factors were significant (p<0.05): QRS duration, PR interval, hypertension, systolic and diastolic blood pressure, diuretic and other antihypertensive medication use, Sokolow-Lyon voltage, body mass index (BMI), current smoking, physical activity index, prevalent coronary heart disease (CHD), and serum potassium level, but fasting serum lipid levels and type 2 diabetes were not. Factors independently associated with increased QT in multivariable LR analysis on backward stepwise selection included RR, female sex, QRS, age, lower potassium, hypertension, BMI, CHD, diuretic use, and Sokolow-Lyon voltage (p≤0.01 for all). The heritability estimated using residuals from a model including age, sex, and RR interval (model R2=0.54) was 0.41 (SE 0.07, p<10−11) and from the multivariable adjusted model (R2=0.58) was 0.40 (SE 0.07, p<10−11), similar to previous estimates in European Americans. In this large population-based cohort of African Americans we identified clinical covariates significantly related to QT. There is substantial heritability of adjusted QT interval in this high-risk group supporting the need for further investigation to identify its genetic determinants in African Americans.