Circadian pattern in the onset of acute myocardial infarction

Objective: To evaluate whether there is a circadian pattern in the onset of acute myocardial infarction. Methods: This study included 60 patients. Diagnosis of myocardial infarction was by ECG and/or enzyme abnormalities. Patients were sub-grouped based on age, sex, prior history of ischaemic heart disease, hypertension, and diabetes mellitus. Time of onset of symptoms was noted. For calculation of frequency of onset of symptoms, the day was divided into 4 quarters. Results: Statistically significant peaks were observed in the second and third quarter of the day. Highest number of patients had onset of events in 2nd quarter of day. Similar pattern of distribution was observed in females, patients above and below 60 years, diabetics, hypertensives, and ischaemic heart disease patients. In males, highest frequency was seen in 3rd quarter. Conclusion: There were statistically significant peaks in the onset of acute myocardial infarction in the 2nd and 3rd quarter of the day.