Relationship between Circardian Variation of Acute Myocardial Infarction and Morphologic Characteristics of Coronary Artery Lesions

ABSTRACT

BACKGROUND: It is known that there is a pronounced circardian periodicity for the time of onset of acute myocardial infarction(AMI), with prominent increase in incidence of onset in the morning hours. However, the characteristic circardian variability in AMI is blunted in patients receiving beta-blockers or aspirin therapy before their presentation with AMI. These findings are attributed to the increase in platelet aggregability, blood coagulability, and plasma catecholamine that change coronary tone and myocardial oxygen demand. We hypothesize that, in addition to above physiologic and biochemical parameters, morphologic patterns of the coronary artery lesions are related to the development of circardian variation in AMI. METHOD: Subjects were 160 patients with AMI(male 92, female 68, mean age 56.9 +/-10.5 years old). Patients were classified by the time of onset of typical chest pain(AMI) by 6-hour interval from mid-night. Circardian variability of onset of AMI was compared with clinical findings and coronary angiographic findings. RESULTS: Incidence of onset of AMI was most frequent in the morning hours(6AM-noon,42.5%). There was no difference in degree of stenosis, lesion length, incidence of intraluminal thrombus, among 3 subgroups of AMI according to time of attack. Morning hour group had more frequent ulceration of coronary lesion than that of other groups(22.4% vs. 5.4%, p<0.01), and less frequent calcified lesion than that of other groups(3.0% vs 5.4%, p<0.05). Normal or minimal coronary artery lesion, that is Iess than 25% stenosis, was more frequent in the morning hour group comparing to that of other groups(11.9% vs. 9.78%). Eccentric stenosis(15.7% vs, 11,1%) and diffuse irregular lesion(25.5% vs. 16.7%) tended to be more frequent in the morning hour group. There were no differences in sex, age, incidence of hypertension, cigarette smoking, diabetes, degree of alcohol ingestion, ejection fraction, maximal CK value, preinfarction angina duration, past history of MI, and in incidence of arrhythmia. CONCLUSIONS: There were more ulcerative coronary atherosclerotic lesions, but fewer calcified coronary lesions in the morning group than in afternoon and night group. These findings indicate that morphology of coronary artery lesions may play a role in causing circardian variation in AMI.