The validity of an exercise test in microvascular angina has not yet been elucidated. Therefore, in order to evaluate the usefulness of the exercise treadmill test in determining the true micorvasculature induced ischemia, we compared patterns of ST depression with coronary flow reserve (CFR) using transthoracic Doppler echocardiography in patients with chest pain and normal coronary angiogram.

Fifty-nine subjects (M:F=21:38, mean age 55±9 yrs) with chest pain and normal coronary angiogram underwent maximal symptom-limited treadmill exercise according to the Bruce protocol. Coronary flow reserve (CFR) was estimated using transthoracic Doppler echocardiography and dipyridamole. Patients with a history of acute myocardial infarction, regional wall motion abnormalities, hypertrophic cardiomyopathy, an ejection fraction of less than 50% or primary valvular heart disease were excluded in this study. The patterns of ST segment depression were compared with CFR.

No ST change was observed in 20 of 59 (34%), upslope depression in 20 (34%), flat depression in 13 (22%) and downslope depression in 6 (10%). Eleven of 39 (28%) exercise positive patients demonstrated decreased CFR<2.1. CFR was 3.1±0.6 in the group with no ST change, 3.1±0.6 in the group with upslope depression, 2.1±0.6 in the group with flat depression (p<0.05 versus the group with no change and the upslope depression group, respectively) and 2.0±0.4 in the group with downslope depression (p<0.05 versus the group with no change and the upslope depression group , respectively). Flat to downslope depression of ST change during exercise treadmill test had a sensitivity of 58% and a specificity of 95% for predicting CFR<2.1.

Flat and downslope depression of the ST segment during an exercise stress test may increase the sensitivity and specificity to detect the true microvasculature-induced ischemia that is defined as CFR less than 2.1.