Role of Myocardial Ischemia and Left Ventricular Wall Motion Abnormalities as Contributory Factors in the Genesis of Exercise-Induced ST-Segment Elevation in Q-Wave Myocardial Infarction

Abstract

In patients with a previous myocardial infarction, controversy exists regarding the significance of postexercise ST-segment elevation in the infarct-related leads. Although usually admitted to be a sign of left ventricular dysfunction or myocardial aneurysm, other studies however have related this finding to transient myocardial ischemia and to the presence of jeopardized but viable myocardium in the infarct area. The aim of the present study was to assess the significance of postexercise ST-segment elevation in Q-wave leads as a marker of transmural ischemia or left ventricular dysfunction in 36 consecutive patients, 16 with exercise-induced ST-segment elevation in infarct-related leads. Patients were evaluated by treadmill exercise testing, coronary angiography and ventriculography, thallium-201 tomographic scintigraphy and radionuclide ventriculography within 3 months of the first myocardial infarction. Sixteen patients (group I) had exercise-induced ST segment elevation and 20 (group II) postexercise inversion, no change or pseudonormalization of the T wave in infarct-related leads. The study showed no difference in infarct-related artery, vessel disease or luminal diameter stenosis in groups I and II. The overall agreement between ST shifts and myocardial perfusion in the infarct area was 30.56% with a κ coefficient of –0.33 (p = NS). The overall agreement between ST shifts and wall motion abnormalities was 69.44% with a κ coefficient of 0.39 (p < 0.01), stress-induced ST-segment elevation being associated with severe wall contractile disorders in 85% of the patients. In conclusion stress-induced ST-segment elevation in Q wave leads, although not a marker of wall motion abnormalities, is associated with akinesia or dyskinesia of the left ventricular wall.

ST elevation occurring during stress testing

“…ST-segment elevations on ECG are observed in acute myocardial infarction but also in severe ischemia, ventricular aneurysm, Prinzmetal's variant angina, and abnormal cardiac hemodynamics (4, 5). This patient's ECG demonstrated ST elevation in one lead only and was reversible after exercise was terminated, thus not fulfilling the criteria for myocardial infarction.…”

“…Macieira-Coehlo et al described the concomitant presence of ST segment elevation on stress testing along with left ventricular wall motion abnormalities in 85% of their patient population (5). Miyakoda et al concluded through their findings that ST segment elevation was not always related to myocardial ischemia but rather to wall motion abnormalities (8).…”