ABSTRACT
ObjectiveTo explore the relationship of circadian distribution of acute myocardial infarction with AMI location and ST segment changes in elderly patients.MethodsThe time of infarction, its anatomic location, changes of ST segment, and coronary angiography were studied in 909 elderly patients with acute myocardial infarction (AMI) ( 412 with anterior AMI and 423 with inferior AMI) admitted to our coronary care units from January 1996 to January 2006.ResultsThe onset of inferior myocardial infarction were more frequent between midnight and 6AM than other periods of the day (n=138/423,32.6% of all inferior myocardial infarction patients, P<0.01). The onset of anterior myocardial infarction were more frequent between 6AM and noon than other periods of the day (n=156/412, 37.9% of all anterior myocardial infarction patients, P<0.01). Coronary angiography was performed in 789 patients (86.8%, 516/909).118 cases of them with inferior infarction occured between midnight and 6AM, including 85.6% of them were due to right coronary artery occlusion and 14.0%(17/118) of them were due to left coronary artery occlusion (P<0.01).275 cases of them with inferior infarction oecured between 6AM and midnight, including 52.2% (149/275) of them were due to right coronary artery occlusion and 45.8% of them were due to left coronary artery occlusion (P>0. 05). The onset of inferior myocardial infarction between 6AM and noon was the most frenquent in patients with ST segment elevation (44.0%, 263/644), while the onset of inferior myocardial infarction between midnight and 6 AM was the most frenquent in patients with non-ST segment elevation (36.6%,96/265). ConclusionsThe frequency of AMI at night is higher in elderly patients with ST segment elevation than in elderly patients with non-ST segment elevation.AMI at night is usually due to right coronary artery occlusion, which suggests that a protective role of sleep may be limited to left coronary artery -related events and AMI of non-ST segment.