Periodic variation and its effect on management and prognosis of Korean patients with acute myocardial infarction

Background: The characteristics of the periodic variation in acute myocardial infarction (AMI) and the sub-sequent effect on management and prognosis have not been fully investigated in a large number of Asian populations. Methods and Results: From a prospective, observational multicenter online registry, 4,573 patients diagnosed as AMI in Korea from January to December 2006 were included. The highest incidence of AMI was between 8 a.m. and noon. The number of cases was highest in the winter and lowest in the autumn (13.6 vs 11.4 patients per day, P<0.001). Patients with symptom onset during working hours had a shorter time to first medical contact (203±288 min) compared with out-of-hours onset (230±288 min, P=0.003). In patients who underwent primary angioplasty, out-of hours symptom onset was associated with a greater time delay in both the patient's and the medical facility's response (door-to-balloon time out-of hours vs working hours: 101±54 min vs 84±44 min, P<0.001). In patients with ST-segment elevation myocardial infarction, symptoms to first medical contact showed a significant relationship to in-hospital mortality (for every 10 min of symptoms to first medical contact, odds ratio 1.006, 95% confidence interval 1.001-1.012, P=0.018) Conclusions: Circadian and periodic variation in AMI exists in Korean patients, which resulted in different patient behavior, hospital management and outcomes.