Lack of diurnal variation in maximal symptom-limited exercise test response in chronic stable angina.

Exercise testing is widely used to evaluate the effects of anti-ischemic drugs. Many studies have reported good reproducibility when it is performed in the morning, but little information is available regarding the diurnal variation of exercise test response in patients with chronic stable angina. With the advent of new long-acting anti-ischemic drugs, it has become necessary to perform the exercise testing at various times of the day to determine the duration of action of a given drug. To examine the diurnal variation, exercise tests were performed on 41 patients, aged 53 to 75 years, with established chronic stable angina on 2 occasions 5 days apart at 10 A.M. and 4 P.M. on each day. On day 1, the mean +/- standard error of the mean exercise time was 5.0 +/- 0.4 minutes at 10 A.M. and 5.1 +/- 0.4 minutes at 4 P.M., and on day 5, it was 5.6 +/- 0.4 minutes at 10 A.M. and 5.5 +/- 0.4 minutes at 4 P.M. These values did not differ in statistical significance. Similarly, the time to the development of 1 mm of ST-segment depression did not show any statistically significant change during either test period on either day nor did maximal ST-segment depression. Heart rate at rest was 79 +/- 3 beats/min at 10 A.M., 81 +/- 3 beats/min at 4 P.M. on day 1 and 78 +/- 2 beats/min at 10 A.M. and 80 +/- 3 beats/min at 4 P.M. on day 5 (difference not significant). Similarly, no significant changes were observed in maximal heart rate or rate-pressure product at peak exercise.(ABSTRACT TRUNCATED AT 250 WORDS)