The association between the length of the QT interval and mortality in the cardiovascular health study

Purpose A long QT interval is a risk factor for arrhythmic events and sudden death. Whether moderate QT prolongation is associated with clinical events in community-dwelling elderly patients is uncertain. Methods We measured the QT interval in a population-based sample of 5888 men and women at least 65 years of age who were participants in the Cardiovascular Health Study. The association between Bazettʹs rate-corrected QT (QTc, in ms) and mortality during the subsequent 10 years was evaluated. We stratified participants by the presence or absence of coronary heart disease status at baseline, and adjusted for coronary heart disease risk factors. Results The rates of all-cause and coronary heart disease mortality were greater in participants with longer QTc intervals. Among participants without known coronary heart disease, those whose QTc interval was>450 ms were at increased risk of all-cause mortality (relative risk [RR] = 1.34; 95% confidence interval [CI]: 1.07 to 1.67) and coronary heart disease mortality (RR = 1.6; 95% CI: 1.0 to 2.5) when compared with participants whose QTc interval was <410 ms. The associations were stronger among those with known coronary heart disease (RR for all-cause MORTALITY = 2.3; 95% CI: 1.6 to 3.3; and RR for coronary heart disease MORTALITY = 2.0; 95% CI: 1.1 to 3.7). Conclusion The QT interval from the standard electrocardiograms is of value for identification of elderly persons at increased risk of coronary heart disease and total mortality. A QTc interval>450 ms should prompt clinical evaluation and possible interventions to reduce the risk of coronary events.