Circadian Variation of Transient Myocardial Ischemia

ABSTRACT

BACKGROUND: Quyyumi et al described circadian variation of ischemic eletrocardio-graphic changes and heart rate in patients with and without significant coronary disease in 1985. Rocco et al also described circadian variation of transient myocaldial ischemia in patients with coronary artery disease. They also noted an increse in ischemic eletrocardiographic abnormalities in the morning hours.In recent years the important of circadian variation of cardiovascular phenomena has generated a great deal of interest. Such phonomena include the occurrence of ischemia in patients with both chronic stable angina and variant angina, myocaldial infarction, sudden cardiac death, ventricular arrhythmia and platelet aggregability. METHOD: To examine whether a significant circadain variation of transient myocardial ischemia exists and to better understand the character of such variation, 35 patients with againa pectoris(15 patients treated with nitrate and/or caclcum channel blocker and 20 patients without treatment) underwent 24 hours ambulatory monitoring of ischemic ST segment changes during daily life. RESULT: Only 21% of the episodes of ST depression were accompanied by chest pain. While 79% were asymptomatic. A significant circadian increase in ischemic activity was found with 44% of episodes and 40% of total ischemic time in not treated group, and 52% of episodes and 56% of total ischemic time in treated group, occuring between 6 A.M. to 12 P.M.(P<0.05 respectively) When the distribution of ischemic episodes was corrected for the variable time of waking, the peak ischemic activity was occuring in the 1st and 2nd hours after rising. There were no significant differences in heart rate at onset and heart rate at 1 min before onset. CONCLUSION: Is summary, transient myocardial ischemia in the absence of pain was more common and there were a significant circadian variation of transient myocardial ischemia with peak activity in the morning. In addition most of transient myocardial were not preceded by a rise in heart rate.