Repeat treadmill exercise testing: Variability of results in patients with angina pectoris

Abstract

To assess the reproducibility and individual variability of ECG treadmill exercise test results, we evaluated 23 patients with coronary artery disease and stable exertional angina by means of two control exercise tests performed on different days within a 1 week period. In addition, each control test was followed on the same day by a single dose of placebo or active agent determined in a randomized double-blind manner and the exercise test was repeated. When the mean exercise test results from the control tests on days 1 and 2 were compared, there was a significant increase in exercise duration to angina (7.4 ± 3.2 to 9.0 ± 3.3 minutes, p < 0.05), ST segment depression (7.8 ± 3.9 to 9.6 ± 3.6 minutes, p < 0.01), and maximal exercise (9.7 ± 3.7 to 11.0 ± 4.1 minutes, p < 0.01). In addition, when the mean exercise results on the control test were compared to those on the postplacebo test on the same day, similar increases in exercise duration were observed at each end point ( p < 0.01). Individual differences of more than 2 minutes in exercise duration between the two control tests and between the control and postplacebo tests in time to angina, ST segment depression, and maximal exercise were frequent (26% to 33% of patients). However, the mean rate-pressure products on the two control tests performed on days 1 and 2 and on the control and postplacebo tests performed on the same day did not differ at angina, ST segment depression, and maximal exercise. Therefore, we conclude that patients demonstrate considerable variability in the time to angina, ST segment depression, and maximal exercise but not in rate-pressure product at these end points.