Comparison of the two-step and maximal exercise tests in patients with coronary artery disease

This study has investigated the claim that the electrocardiographic response to the maximal exercise test provides a more accurate method of assessing the presence and severity of coronary artery disease than the electrocardiographic response to the two-step test. One hundred and one men with a chest pain syndrome underwent the two-step test, maximal exercise test and coronary angiography during the same admission. There was a preponderance of men who performed the maximal exercise test as a result of a negative two-step test. A positive two-step test was defined as horizontal or downsloping S-T segment depression of 0.5 mm or more, whereas a positive maximal exercise test was defined as similar S-T segment depression of 1.0 mm or more. Of the 17 men with no or insignificant coronary artery disease, 5 had a positive two-step test and 6 a positive maximal exercise test. Of the 84 men with coronary artery disease, 33 had a positive two-step test and 38 a positive maximal exercise test. Thus, the specificity of the two-step test for coronary artery disease was 87 percent and that of the maximal exercise test was 86 percent; the respective sensitivity rates were 39 and 45 percent. The percentage of positive results of both exercise tests increased similarly with the severity of coronary artery disease. Nine patients, eight of whom had coronary artery disease, had a positive maximal exercise test but a negative two-step test; in these patients the maximal heart rate was significantly higher during the maximal exercise test than during the two-step test. Five patients, all with coronary artery disease, had a positive two-step test but a negative maximal exercise test. One patient manifested 0.5 mm S-T segment depression in both tests and was thus judged to have a positive two-step test and a negative maximal exercise test. In another patient results were positive in lead V₄ of the two-step test, a lead not recorded in the maximal exercise test. The other three patients had had positive results in a second maximal exercise test recorded in the supine position, thus demonstrating that in certain cases the effects of augmented venous return in the supine position may be as important a factor in eliciting ischemia as the achieved heart rate.