Treadmill Exercise Testing in the Presence of Digitalis Therapy or Nonspecific ST-T Changes: Correlation with Coronary Angiography

Abstract

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 digitalls; 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.