SUMMARY ST-segment elevation was observed in 47 of 720 patients who underwent treadmill exercise testing using 14 ECG leads 1 day before coronary arteriography. This abnormality was detected in lead V. in only 13 of 47 patients (28%) and in lead CM5 in only nine of 47 patients (19%). In 36 patients previous myocardial infarction (27 anterior, nine inferior) was diagnosed on the resting ECG; in all cases the ST-segment elevation during exercise occurred in leads with Q waves. In 34 of 36 patients (94%) a corresponding left ventricular wall motion abnormality was present, usually (33 of 36, 92%) a dyskinetic or akinetic segment. All but two of the 36 patients had a coronary stenosis > 70% in the artery perfusing the involved region.Ten of the 11 patients with no ECG evidence of myocardial infarction had documented variant angina. In all 10 cases ST-segment elevation during exercise occurred in the same ECG leads as during spontaneous resting attacks. All 10 had normal left ventricular angiograms and only three had a coronary stenosis 2 70%. A large perfusion defect corresponding to the site of ST-segment elevation and not present at rest was detected in each of the six who had exercise thallium-201 scans. Four patients retested during treatment with nifedipine did not develop angina, ST changes or perfusion defects.These findings suggest that exercise-induced ST-segment elevation is probably caused directly by a segmental wall motion abnormality in patients with previous myocardial infarction, but by coronary artery spasm in patients with variant angina.THE CLINICAL SIGNIFICANCE of ST-segment depression during exercise testing is well understood.' In contrast, the mechanism for exercise-induced STsegment elevation, a more unusual finding, is controversial and the associated clinical and angiographic features vary widely from one study to another.2`9 Many authors2' 5-8 conclude that localized left ventricular dysfunction, which is present in nearly all of these patients,2 accounts for ST-segment elevation during exercise; however, others1 3, 4suggest that severe myocardial ischemia is the cause, because most patients also have critical coronary stenoses. On the other hand, exercise-induced ST-segment elevation has been reported in patients with variant angina. 10 At our institution 720 patients have undergone clinical evaluation and treadmill exercise testing with 14 ECG leads on the day before coronary and left ventricular angiography. The primary purpose of this study was to examine the clinical and angiographic features of the patients in this population who developed ST-segment elevation during exercise. In addition, we have compared the sensitivity of different ECG leads in detecting this abnormality.
Methods
Patient SelectionMaximal treadmill exercise tests using a 14-lead ECG system were performed on 720 consecutive patients 1 day before coronary and left ventricular angiography. Those with unstable angina, associated valvular, cardiomyopathic or congenital heart disease, overt heart failure or limiting ort...