The Effect of Coronary Risk Factors on QT Dispersion

It is known that in patients with ischemic heart disease, QT dispersion (QTd) predicts ventricular arrhythmia and sudden cardiac death and that major coronary risk factors such as smoking, diabetes mellitus, hypertension increase QTd. It is not clear whether, in coronary artery disease, QTd increases because of ischemia or co-existence of coronary risk factors. In this study, we aimed to investigate the independent effect of coronary risk factors on QTd by examining patients with just one major coronary risk factor. 133 (111 patient, 22 healthy people, average age (52±10; 49±11) patients were included in our study. The patients were divided into 5 groups according to existence of diabetes mellitus (19 patients), hypertension (24 patients), hyperlipidemia (17 patients), a positive family history (21 patients), smokers (30 patients). The control group consists of completely healthy subjects without any risk factors (22 patients). 12 derivations ECG of all patients were recorded at 50 mm secG . QT intervals were measured after the ECG recordings were transferred to a 1 computer and magnified by 400-600 times with Adobe photoshop program on a high resolution monitor. QTd and QTcd (QT corrected dispersion) of all groups with one risk factor were significantly higher than the control group (p< 0.01). In addition, each coronary risk factor had an independent and significant increasing effect on QT interval (p<0.01). QTd and QTcd intervals are affected by coronary risk factors as well as ischemia and this finding should be taken into account in studies concerning QT intervals.