Association of a Corrected QT Interval with the Carotid Intima-Media Thickness and the Severity of Coronary Artery Disease in Patients with Coronary Artery Disease

Background and Objectives: A prolonged heart rate-corrected QT interval (QTc) is known to be related to an increased risk of coronary artery disease (CAD) and sudden cardiac death, while the carotid intima-media thickness (IMT) is related to CAD. We sought to evaluate the relationship among the QTc, the carotid IMT and the severity of CAD. Subjects and Methods: The QTc and the carotid IMT were measured in 165 consecutive patients who underwent coronary angiography. The measurement of the QTc was done automatically by a digital QT Guard TM system (GE Marquette Medical System, Milwaukee, USA) and the carotid IMT was measured by M’ATH software (METRIS Co., Argenteuil, France). The severity of CAD was divided into minimal disease (90, 54.5%), one-vessel disease (32, 19.4%), and multi-vessel disease (43, 26.1%), according to the number of vessels that were narrowed by more than 50%. Results: The mean values of the QTc were 415.1±20.5 msec in the minimal disease group, 411.7±17.0 msec in the one-vessel disease group and 434.2±46.1 msec in the multi-vessel disease group. The QTc was correlated with age (r=0.236, p=0.002), HDL cholesterol (r=-0.160, p=.043), the right carotid IMT (r=0.17, p=0.026), the left carotid IMT (r=0.178, p=0.022) and the severity of CAD (r=0.243, p=0.002). On the multiple linear regression analysis after adjustment for age and HDL cholesterol, the QTc was an independent factor for the severity of CAD. Conclusion: These results suggest that repolarization abnormalities are associated with the severity of CAD and they may reflect the severity of the morphologic atherosclerotic surrogates. (Korean Circ J 2007;37:538-542)