Stress and rest QT dispersion in ischemic heart disease patients with different grades of ischemia

The correlation between QT dispersion (QTd) and myocardial ischemia is controversial. The main purpose of current study was to investigate the relationship between QTd and the severity and extent of myocardial ischemia. In this cross sectional study, 100 patients with suspected coronary artery diseases (CAD) were studied. Based on the results of the myocardial scan (SPECT), patients were categorized as normal, or with mild, moderate and severe ischemia; QTd was measured in rest and stress as maximum difference between QT intervals in 12 lead ECG. As a final point, the correlation between rest and stress QTd and the severity and extent of ischemia (number of ischemic segments and summed ischemic score) were investigated, and also rest and stress QTd was compared between groups and normal value of 65 milli seconds (ms). Normal myocardium and mild, moderate and severe ischemia was observed in 58, 16, 20 and 6 percent of patients, respectively. Mean rest QTd of normal subjects and ischemic patients were 48.6±12.3 ms and 43.2±18.7 ms (0-130), respectively (p=0.052). Mean stress QTd of normal subjects (45.6±14 ms) was significantly lower than ischemic patients (65±23.2 ms) (p<0.001). Stress QTd was correlated positively with number of ischemic segments and summed ischemic scores in total patients. In normal subjects, stress and rest QTd were the same, but there was significantly increased stress QTd in ischemic patients. It seems that stress QTd is correlated with severity and extent of myocardial ischemia and is useful in clinical practice to investigate the ischemic lesions of the myocardium.