Circadian variation in acute myocardial infarction

ABSTRACT

BACKGROUND: TAn increased occurrence of morning time acute myocardial infarction(AMI) based on subjective self-reports and objective confirmation has been reported in the USA and Europe. We tried to see if the same circadian pattern is found among Korea patients in the regard. We have also studied how various modifying factors such as age, gender, history of congestive heart failure, previous angina pectoris, hypertension and smoking may affect the circadian pattern. METHODS: The onset of chest pain was studied in 471 patients with AMI admitted to four teaching hospitals in Taegu. Korea. We categorized the patients according to the modifying factors described above. RESULTS: The patients with AMI indeed showed bimodal variation at the onset of myocardial infarction with the primary peak between 6 A.M. and 12 noon. The frequency of the onset of pain occurred during this 6 hour period was 1.8 times higher than the average of the remaining period(p<0.001). The secondary peak occurring in the evening was barely noticeable. On the other hand. the sub-group(n=96) with a history of congestive heart failure demonstrated its peak(30%) in the evening(6 pm~12 midnight) and the sub-group with a history of hypertension(n=177) demonstrated its peak(37%) in the afternoon(12noon-6P.M.). However. the rest of the sub-groups smokers, patients with previous angina and patients over the age of 70 revealed typical circadian rhythm with a pronounced primary morning peak. CONCLUSIONS: This study clearly showed that Korean patients with AMI revealed a remarkably similar circadian pattern, primary morning peak of onset of myocardial infarction and that the marked differences in diurnal patterns of myocardial infarction onset occur in sub-groups of patients with modifying factors, particularly previous congestive heart failure and hypertension.