Ethnic differences in ST height in the multiethnic study of atherosclerosis.

Elevation of ST height in the absence of coronary artery disease was first described in 1936 by Shipley and Hallaran1. This phenomenon has been referred to as “unusual RT segment deviation”, “normal RST elevation variant”, “Benign Early Repolarization” and finally “Early Repolarization” 2,3. Although non-ischemic ST elevation had been thought to be “benign”, patients with Brugada Syndrome who have right bundle branch block and ST elevation in the right precordial leads are at increased risk for sudden death4. In addition, polymorphisms in genes coding for ion channels appear to differ across ethnic groups; some of these polymorphisms might lead to ST elevations associated with sudden death5. Finally, ethnic differences in the incidence of sudden death have been described and could be related to ethnic differences in repolarization properties 6,7. Thus, a better understanding of population and ethnic distribution of ST height could provide information as to whether ST elevation is a marker of arrhythmic risk. Although initially described in non-Hispanic whites, ST elevation appears to be present in all ethnic groups. In one study, early repolarization had 0.9% overall prevalence; the incidence is 1.8% and 0.2 % respectively in men and women8. We are aware of only two studies that examined racial/ethnic differences in ST height or repolarization. Using data from the Atherosclerosis Risk in Communities Study, Vitelli et al9 found that ST height in leads V2 to V5 was statistically significantly higher in African Americans compared to Caucasians. In a population-based study conducted by Klatsky et al 8, the incidence of early repolarization, as determined by blinded cardiologists’ reading, was assessed. In that study, which contained predominantly African Americans and Caucasians and a limited number of Asians (less than 10%), the incidence of early repolarization was 1.5% in African American’s, 0.6% in Caucasians and 1.6% in Asians. To date, there are no studies comparing ST height among African Americans, Asians, Hispanics and non-Hispanic white men and women. The Multi-ethnic Study of Atherosclerosis is a longitudinal study of the health of older men and women from each of the four ethnic groups with measurements of lifestyle, anthropometric and coronary heart disease risk factors, and ST height measured at baseline. A comparison of ST height across ethnic groups is of particular interest because of the ethnic differences in inherited arrhythmia syndromes and in sudden death unassociated with the known syndromes noted above.