Background and Objectives: The QT interval (QTi) and QT dispersion (QTd), which represent the myocardial
electrical heterogeneity of repolarization, were studied to recognize the differences between normal controls (n=32)
and stable angina patients (n=78). Subjects and Methods: During the treadmill exercise test, standard 12 lead
Electrocardiogram (ECG) was obtained at every stage, with the QTi and QTd measured. The corrected QT interval
(cQTi) and QT dispersion (cQTd) were calculated using Bazett’s formula, with the Delta QT interval (ΔQTi)
measured on leads V5 and aVF. Results: During exercise, the QTi had a reverse relationship with the heart rate in
both groups, but was decreased by a lesser extent in the patient group. The QTd also had a tendency to decrease
according to increasing heart rate in both groups and was significantly greater in the patient group. The corrected
QTi increased during exercise in both groups, and reached maximum during the pre-peak stage, but was minimized
during a 1 minute recovery stage in the patient group. The corrected QTd reached a maximum during the
peak exercise stage in both groups, but the values between the two groups were significantly different. Both the QTi
and cQTi had tendencies to increase according to the number of vessels with stenosis. The ΔQTi tended to reflect
a regional ischemia in a single vessel disease. Conclusion: The QTi, QTd, cQTi and cQTd were increased in the
stable angina patients compared with the normal controls, and augmented during the exercise test.