Treadmill exercise testing in the presence of digitals therapy or nonspecific ST-T changes: correlation with coronary angiography.

Treadmill exercise test results were studied in 93 patients with chest pain who had received digitalis therapy or had nonspecific ST-T changes in the resting electrocardiogram. Results of the treadmill test were correlated with the findings of coronary angiography. A positive treadmill result was defined as horizontal or down-sloping ST segment depression greater than or equal to 1.0 mm. Of the 40 patients with no or insignificant coronary artery disease, 15 had taken digitalis; 4 of the 15 demonstrated a positive response on the treadmill test. Of the 53 patients with coronary artery disease, 21 had taken digitalis; 15 of the 21 displayed a positive response. Among the remaining 32 not on digitalis, 20 had a positive response. The specificity of the treadmill exercise test was 96% in patients with coronary artery disease not on digitalis and whose resting electrocardiogram showed nonspecific ST changes. The specificity of the treadmill test in patients who had received digitalis was 73%. Sensitivity was 63% and 71%, respectively. By utilizing more stringent criteria in the interpretation of the treadmill exercise test (greater than or equal to 1.5 mm ST depression), among the patients on digitalis only 6.7% (1/15) with normal coronary arteries and 48% (10/21) with coronary artery disease had a positive response. With the use of the latter criterion the test was specific in 93% (14/15) of the patients and is usually indicative of coronary artery disease.