[Anterior ST segment depression during the exercise test in patients with previous inferior myocardial infarct. Scintigraphic and coronary arteriographic correlations].

Left ventriculography and coronary arteriography were performed in 49 patients: agreement on location of infarcted area was present between ventriculography and ECG in 22 cases and between ventriculography and myocardial scintigraphy in 34 cases (p less than 0.00125). Consequently on the basis of the scintigraphic redistribution image, all our patients were divided in 2 Groups: Group A, with inferior infraction (120 cases), and Group B, with infero-posterior or posterior infarction (68 cases). Exercise test showed anterior ST segment depression in 97 patients (59 from Group A and 38 from Group B). In these cases myocardial scintigraphy showed anterior ischemia in 48 (81%) patients of Group A and only in 17 (45%) of Group B (p less than 0.005). In patients with negative exercise test, myocardial scintigraphy detected anterior ischemia with similar incidence in both groups (about 40%). Out of the 49 patients studied by coronary arteriography, 33 had left anterior descending coronary artery disease: exercise test induced anterior ST depression in 25 of them (sensitivity 77%), while myocardial scintigraphy showed anterior ischemia in 29 (sensitivity 87%). Normal coronary arteries or isolated right or circumflex artery disease were found in 16 patients: 9 of them had anterior ST depression (specificity 56%) and none showed scintigraphic evidence of anterior ischemia (specificity 100%). In conclusion, in patients with previous infarction of inferior and/or posterior wall, ST-segment depression induced by exercise in anterior leads can be a false positive result, without a corresponding anterior myocardial ischemia. This finding is more often observed in patients with infarction of the posterior wall, in whom anterior ST depression on exercise might be due to ischemia or dyssynergy of the infarcted area. Myocardial scintigraphy allows a more precise identification of the scar location, and above all it is provided with good sensitivity and specificity in identifying residual ischemia due to left anterior descending coronary disease.