Race- and sex-associated differences in rate-adjusted QT, QTpeak, ST elevation and other regional measures of repolarization: The Atherosclerosis Risk in Communities (ARIC) Study

Background Data are limited about race-and sex-associated differences in prognostically important ECG measures of regional repolarization. Methods and results The normal reference group from the Atherosclerosis Risk in Communities (ARIC) study included 8,676 white and African-American men and women aged 40-65 years. Exclusion criteria included cardiovascular disease, hypertension, diabetes and major ECG abnormalities. Notable sex differences (p < 0.001) were observed in the upper 98% limits for rate-adjusted QTend (QT_ea) which was 435 ms in white and African-American men and 445 ms in white and African-American women, and for left ventricular epicardial repolarization time (RT_epi) which was 345 ms in white and African-American men and 465 ms in white and African-American women. These sex differences reflect earlier onset and end of repolarization in men than in women. Upper normal limits for STJ amplitude in V2-V3 were 100 μV in white and African-American women, 150 μV in white men and 200 μV in African-American men (p < 0.001 for sex differences), and for other chest leads, aVL and aVF 50 μV in white women, 100 μV in African-American women, 100 μV in white men and 150 μV in African-American men (p < 0.001 for sex and race differences). Conclusions Shorter QT_ea and RT_epi in men than in women reflect earlier onset and end of repolarization in men. STJ amplitudes in African-American men were higher than in other subgroups by race and sex. These sex and race differences need to be considered in clinical and epidemiological applications of normal standards.