To improve the performance of exercise stress testing in the diagnosis of effort angina while minimizing risks of serious complications, we evaluated an impulse response of ST changes, which is a transient ST response resulting from a hypothetical, strenuous-impulse like exercise, without actually imposing the strenuous load. To obtain the impulse response, subjects walked intermittently according to a computer-generated random binary sequence on a treadmill for 20 minutes. We used Fourier transform for beat-to-beat changes in ST level and binary sequence of exercise. We then determined the transfer function by taking the ratio of Fourier transformed ST level to exercise over the frequency range of 0.5 through 5.0 cycles/min. Converting the transfer function to the time domain yielded the impulse response of ST change. The subjects consists of 49 patients (60±9 years) with effort angina, 13 patients with atypical chest pain (56±9 years), and 30 healthy, males volunteers (23±7 years). In 82 subjects (89%), the ST impulse response showed an initial depression followed by a smooth, gradual restoration toward the pre-exercise ST level (type I response). The average duration of the initial depression was 8±3 seconds in the healthy volunteers, whreas it was significantly prolonged to 23±14 seconds in effort angina (p<0.05). The depression in patients with atypical chest pain was not significantly different from that in the healthy volunteers. Although the level of exercise was milder in the proposed exercise test than in the conventional treadmill exercise test, the sensitivity and specificity were significantly better in the proposed exercise test than in the conventional one in the same population. We conclude that this random exercise test is a sensitive, safe tool and is useful for the diagnosis of effort angina.

DESCENTE SPORTS SCIENCE Vol.10/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE