The purpose of the study was to determine the value of exercise electrocardiography in predicting the area of myocardial ischemia.

Seventy-six anginal patients with a perfusion defect in one vessel territory on exercise 99mTc-MIBI myocardial perfusion scan were studied. Each patient underwent exercise electrocardiograhy using modified Bruce protocol. Exercise electrocardiography was interpreted as abnormal when the horizontal or downsloping depression in ST segment was 0.1 mV or greater at 80 msec after the J point during exercise. Forty-eight patients had exercise induced ST-segment depression.

Twenty-five patients had exercise induced ST-segment depression in single lead-group and 23 patients had in multiple lead-groups. In 18 patients (18/23) with exercise induced ST-segment depression in multiple lead-groups, the perfusion defect involved the apical area on myocardial perfusion scanning and in 21 patients (21/25) with ST-segment depression in single lead-group, the perfusion defect did not involve the apical area. In patients without perfusion defect in the apical area, ST-segment depression in anterior lead-group (V1 to V4) was associated with myocadial perfusion defects in left anterior descending artery territories in five of five cases (100%), ST-segment depression in lateral lead-group (I, aVL, V5, V6) was associated with defects in left circumflex artery territories in six of six cases (100%), and ST-segment depression in inferior lead group (II, III, aVF) was associated with defects in right coronary artery territories in nine of ten (90%) (p<0.01). In patients with perfusion defect in the apical area, exercise induced ST-segment depressions were observed in multiple lead-groups (18/22).

ST-segment depression on 12 lead exercise electrocardiography was a good predictor of the site of myocadial ischemia in anginal patients with single vessel territory ischemia when ST-segment depression developed in single lead group. However, ST-segment depressions in mutiple lead-groups suggested that the perfusion defect involved the apical area and did not predict the site of myocardial ischemia.