Study of myocardial ischemia at both positive and negative acrophases of circadian rhythm of heart rate in patients with stable effort angina

In this study, the reproducibility of the myocardial ischemia (ST downsloping) in 10 normotensive patients with coronary artery disease and stable effort angina was applied to various haemodynamic parameters (heart rate, systolic blood pressure, double product, workload, time of exercise, and total workload) in five experimental times of each ergometric test (angina threshold, ischemic threshold, peak work, maximal common work, and maximal common double product) performed under both basal conditions and placebo in the daytime and nightime of the same day and of two next days. The daytime and nightime test corresponded to the positive acrophase - maximal diurnal heart rate - and the negative acrophase - minimal nocturnal acrophase - (established by Halberg's cosinor method), respectively, which were considered the two moments of the maximal and minimal sympathetic tone. In the comparison of the parameters of diurnal and nocturnal tests, performed under both basal conditions and placebo ...