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Original Articles

Clinical Correlates and Heritability of QT Interval Duration in Blacks

The Jackson Heart Study

Ermeg L. Akylbekova, MS, Mstat; Richard S. Crow, MD; William D. Johnson, PhD; Sarah G. Buxbaum, PhD; Stephanie Njemanze, BA; Ervin Fox, MD; Daniel F. Sarpong, PhD; Herman A. Taylor, MD and Christopher Newton-Cheh, MD, MPH

From Jackson State University (E.L.A., S.G.G., D.F.S.), Jackson Heart Study, Jackson, Miss; the Division of Epidemiology (R.S.C.), School of Public Health, University of Minnesota, Minneapolis, Minn; University of Mississippi Medical Center (W.D.J., E.F., H.A.T.), Jackson, Miss; Wellesley College (S.N.), Wellesley, Mass; Center for Human Genetic Research and Cardiovascular Research Center (C.N.-C.), Massachusetts General Hospital, Boston, Mass; and the Program in Medical and Population Genetics (C.N.-C.), Broad Institute of Harvard and MIT, Cambridge, Mass.

Correspondence to Christopher Newton-Cheh, MD, MPH, Massachusetts General Hospital, 185 Cambridge St, CPZN 5.242, Boston, MA 02114. E-mail cnewtoncheh{at}chgr.mgh.harvard.edu

Received February 17, 2009; accepted May 21, 2009.

Background— Electrocardiographic QT interval prolongation is a risk factor for sudden cardiac death and drug-induced arrhythmia. The clinical correlates and heritability of QT interval duration in blacks have not been well studied despite their higher risk for sudden cardiac death compared with non-Hispanic whites. We sought to investigate potential correlates of the QT interval and estimate its heritability in the Jackson Heart Study.

Methods and Results— The Jackson Heart Study comprises a sample of blacks residing in Jackson, Miss, of whom 5302 individuals with data at the baseline examination were available for study. Jackson Heart Study participants on QT-altering medications, with bundle-branch block, paced rhythm, atrial fibrillation/flutter, or other arrhythmias were excluded, resulting in a sample of 4660 individuals eligible for analyses. The relation between QT and potential covariates was tested using multivariable stepwise linear regression. Heritability was estimated using Sequential Oligogenic Linkage Analysis Routine in a subset of 1297 Jackson Heart Study participants in 292 families; the remaining sample included unrelated individuals. In stepwise multivariable linear regression analysis, covariates significantly associated with QT interval duration included R-R interval, sex, QRS duration, age, serum potassium, hypertension, body mass index, coronary heart disease, diuretic use, and Sokolow-Lyon voltage (P0.01 for all). The heritability of QT interval duration in the age-, sex-, and R-R interval–adjusted model and in the fully adjusted model was 0.41 (SE, 0.07) and 0.40 (SE, 0.07; P<10^–11 for both), respectively.

Conclusions— There is substantial heritability of adjusted QT interval in blacks, supporting the need for further investigation to identify its genetic determinants.

Key Words: QT interval • genetics • heritability • Jackson Heart Study

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CLINICAL PERSPECTIVE

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