The relationship between QT dispersion and ischemic injuries in myocardial isotope scan.

The relationship between QT dispersion and myocardial ischemia is still controversial. Therefore, we aimed to investigate the relationship between QTd and the severity and extent of myocardial ischemia. In this cross-sectional study, 141 patients having symptoms of CAD who referred to our medical center during 2009-2010, and were examined with myocardial isotope scan and ECG, were enrolled. Based on the Electrocardiography and Single-Photon Emission Computed Tomography results, the patients were categorized as having normal, mild, moderate, and severe ischemia. QTd was measured at rest and under stress as the maximum difference between QT intervals in 12-lead ECG. Ultimately, 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 the rest and stress QTd was compared between the groups. QTd under stress was positively correlated with the number of ischemic segments and summed ischemic scores in all patients. In normal patients, stress and rest QTd were the same. The QTd under stress significantly increased in patients with ischemia. There was no significant difference between the groups regarding QTd at rest. Stress QTd was significantly greater in patients with severe ischemia and greater in patients with mild and moderate ischemia compared with the normal patients. Stress QTd difference between mild and moderate ischemic groups was not significant. QTd under stress is related to the severity and extent of myocardial ischemia and is clinically useful for identifying ischemic myocardial injuries.