Circadian Variation of the Myocardial Ischemic Threshold in Patients with Ischemic Heart Disease

Abstract

In comparing circadian variation between HR at the sympathetic tone threshold and HR at the ischemic threshold, there was a period during which there was no significant difference between the HRs. This might suggest a period in which a high incidence of cardiac ischemic attack is likely. This information could provide a feasible indicator for appropriate exercise training for patients with ischemic heart disease.

Circadian rhythms and cardiovascular health

“…More than 80% of the episodes of ambulatory MI are associated with substantial increases in HR. 199,200 The relative tachycardia that accompanies morning arousal from sleep at night results in increased myocardial oxygen demand 199 and contributes to the excess morning frequency of MI, AMI, and SCD. 200,201 However, ischemic events occur also during sleep, especially in persons with severe CAD and vasospastic (variant) angina.…”

“…199,200 The relative tachycardia that accompanies morning arousal from sleep at night results in increased myocardial oxygen demand 199 and contributes to the excess morning frequency of MI, AMI, and SCD. 200,201 However, ischemic events occur also during sleep, especially in persons with severe CAD and vasospastic (variant) angina. As previously discussed, the strong circadian relationships between sleep, BP, and HR help explain why MI may be triggered overnight during REM sleep.…”