Is QT Interval a Marker of Subclinical Atherosclerosis in Nondiabetic Subjects?

Abstract

Background and Purpose —We studied the relationship of heart rate–corrected QT interval with subclinical atherosclerosis, as determined by ultrasonographic measurement of carotid intima-media thickness (IMT) in nondiabetic subjects in the Insulin Resistance Atherosclerosis Study (IRAS). Prolonged heart rate–corrected QT interval is an unfavorable prognostic factor of cardiovascular morbidity and mortality, and QT interval prolongation may be the result of atherosclerosis. Methods —B-mode ultrasound imaging of the carotid artery IMT was performed in a large, triethnic, nondiabetic population free of clinical coronary artery disease (n=912). QT interval was measured on resting electrocardiograms with use of a computer program and corrected for heart rate with standard equations. Results —IMT of the common carotid artery correlated significantly with heart rate–corrected QT interval duration ( r =0.15 for QT 60 and r =0.14 for QTc), whereas no relationship between IMT of the internal carotid artery and QT interval was found ( r =−0.01). The association was somewhat stronger in women than in men. In a multiple regression analysis adjusting for demographic variables, the association of common carotid artery IMT to heart rate–corrected QT interval remained highly significant, but adjustment for cardiovascular risk factors weakened the relationship. Conclusions —We found a significant relation of heart rate–corrected QT interval to carotid atherosclerosis in nondiabetic subjects that was stronger in women and partly mediated by cardiovascular risk factors, including hypertension. QT interval may therefore serve as a marker for clinically undetected (“subclinical”) atherosclerotic disease.