Circadian Variation of the Total Ischemic Burden and Influence by β-Blocking AgentsFox K. M.; Mulcahy, D. A.Journal of Cardiovascular Pharmacology: 1990 Article: PDF Only Abstract Summary We investigated 150 unselected patients with proven coronary artery disease. All patients were off all routine antianginal treatments and there were 598 ischemic episodes, of which 75% were silent. It was found that episodes of ischemia, both silent and painful, occurred predominantly during the daytime hours from 0730 to 1930 h. This pattern is similar to that described by others. There was a significant excess of episodes of ischemia in the morning hours (0730–1330 h). with a secondary peak occurring in the evening hours. We further investigated a subgroup of 41 patients who were monitored for 1.581 h while being treated with atenolol. These patients were investigated in a double-blind fashion, and during the off treatment phase the circadian pattern of ischemic episodes was similar to that described for the group as a whole. However, on treatment with atenolol. there was a significant reduction in the frequency and total duration of ischemic episodes through out the day. Atenolol significantly altered the circadian distribution of ischemic episodes with elimination of the morning peak: there was some preservation of the evening peak although this was smaller than that described when the patients were off therapy. The circadian distribution of ischemic episodes and the observed changes with β-blocking treatment resemble the reported circadian variation of acute myocardial infarction and sudden death. Although these studies do not in any way prove that myocardial ischemic episodes and their alteration by treatment are related to the development of acute myocardial infarction and death, the relationship between ischemic episodes and the end points of coronary disease require further investigation. Copyright © 1990 Wolters Kluwer Health, Inc. All rights reserved.