Use of QT dispersion measured on treadmill exercise electrocardiograms for detecting restenosis after percutaneous transluminal coronary angioplasty

Background: Treadmill exercise electrocardiography (ECG) has been used to detect restenosis in patients following percutaneous transluminal coronary angioplasty (PTCA). However, the level of sensitivity achieved using conventional criteria of ST-segment depression is too low to be clinically useful in this population. Hypothesis: QT dispersion is a sensitive method for detecting myocardial ischemia and may improve the accuracy of treadmill exercise ECG testing for detecting restenosis after PTCA. Methods: We evaluated 104 patients who underwent PTCA for the treatment of single-vessel coronary artery disease and who had no history of myocardial infarction. Treadmill exercise ECG and coronary angiograms were performed 3 months after PTCA to determine the accuracy of diagnosing restenosis based on standard ST-segment depression and QT dispersion criteria. Results: Restenosis was observed in 37 of the 104 patients (36%) 3 months after PTCA. QT dispersion immediately after exercise was significantly greater in patients with than in those without restenosis, as was the difference in QT dispersion before and immediately after exercise. The sensitivity, specificity, and accuracy of ST-segment depression criteria were 59, 64, and 63%, respectively. Measurements of QT dispersion immediately after exercise (greater than or equal to 50 ms: positive, <50 ms: negative) improved the sensitivity, specificity, and accuracy of treadmill ECG for predicting restenosis to 81, 87, and 85%, respectively. Conclusions: This novel diagnostic method using QT dispersion-based criteria significantly improves the clinical usefulness of treadmill exercise ECG for detecting the presence of restenosis after PTCA.