Enhanced detection of ischemic but viable myocardium by QT interval dispersion on treadmill exercise electrocardiograms of patients with healed anterior wall myocardial infarcts.

BACKGROUND: The presence of ischemic but viable myocardium in infarcted areas is an important indication for coronary revascularization, but is often difficult to detect with the use of treadmill exercise electrocardiography (ECG). HYPOTHESIS: QT interval dispersion (QTd) is a sensitive method for detecting myocardial ischemia and may improve the accuracy of treadmill exercise ECG testing for detecting ischemic but viable myocardium in infarcted areas. METHODS: Forty-five patients with Q-wave anterior wall myocardial infarctions who underwent treadmill exercise ECG, exercise reinjection thallium-201 (201Tl) scintigraphy, radionuclide angiocardiography, and coronary angiography 1 month after infarction were enrolled in this study. The presence of viable myocardium in the infarct area was determined by exercise reinjection 201Tl scintigraphy. Patients who had no redistribution in the infarct area after reinjection were included in Group 1, and those with redistribution were included in Group 2. RESULTS: QTd immediately after exercise, and the difference between QTd before and immediately after exercise, were significantly greater in Group 2 than in Group 1. The sensitivity, specificity, and accuracy of conventional ST-segment depression criteria for detecting viable myocardium in the infarct area were 48, 64, and 56%, respectively. The measurement of QTd immediately after exercise (abnormal: > or = 70 ms; normal: < 70 ms) improved the sensitivity, specificity, and accuracy to 78, 82, and 80%, respectively. CONCLUSIONS: This novel diagnostic method using QTd-based criteria significantly improves the clinical usefulness of treadmill exercise ECG testing for detecting ischemic but viable myocardium in infarct areas in patients with healed Q-wave anterior wall myocardial infarctions.

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 diagnosis 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 (> or = 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.

Clinical significance of the disappearance of septal Q waves after the onset of myocardial infarction: correlation with location of responsible coronary lesions.

We investigated the relationship between the disappearance of septal Q waves after myocardial infarction (MI) and the location of the culprit lesion. We studied 82 patients following their first anteroseptal MI who had an electrocardiogram performed before the MI. Septal Q waves were detectable before MI in 56 patients and disappeared after MI in 17 of those patients. The culprit lesion was located proximal to the origin of the first septal branch (S1) in 13 patients (76%). Disappearance of septal Q waves following MI predicted that the culprit lesion was proximal to the origin of S1 (sensitivity, 42%; specificity, 84%; predictive value, 76%; and accuracy, 61%). If septal Q waves that were detected before MI disappeared after MI, the culprit lesion was located proximal to the origin of S1 in 76% of the patients. This finding may be clinically useful in caring for patients following MI.