Myocardial infarction, circadian rhythm and delay in hospital admission.

Circadian variations have been observed in the onset of acute coronary syndromes including acute myocardial infarction. We studied 422 acute myocardial infarction patients who presented to the coronary care unit of General Hospital Kuala Lumpur. Of the 318 (75.4%) patients whose data was complete, a circadian rhythm with bimodal peak was demonstrated. The second quarter of the day i.e. 6.00 a.m. to 12 noon was shown to have a significantly increased frequency of onset of acute myocardial infarction (p less than 0.05). Time delay in presenting to the hospital was also determined. This showed that 56.8% of acute myocardial infarction patients presented early, within four hours of the onset of symptoms. By six hours, more than 71% had sought hospital care. This early presentation to the hospital may offer a realistic opportunity for optimal thrombolytic therapy should this treatment modality be offered as routine to infarct patients.