title: Circadian distribution of acute myocardial infarction by anatomic location and coronary artery involvement.
abstract: OBJECTIVE
  Acute myocardial infarction follows a circadian pattern, with a morning peak ascribed to sympathetic activation. However, about 20% of myocardial infarctions occur between midnight and 6 AM; these events may have different characteristics.
  
  
  METHODS
  We studied 1571 patients with acute myocardial infarction (866 anterior and 705 inferior myocardial infarctions) who were admitted to our coronary care units from January 1997 to February 2001. We noted the time of the infarction, its anatomic location, and the involved coronary arteries.
  
  
  RESULTS
  Inferior myocardial infarctions were more frequent during the night (midnight to 6 AM) than during other periods of the day (n = 238, 34% of all inferior infarctions, P <0.01). When coronary angiography was performed (795 patients), 92% (127/138) of inferior infarctions were due to right coronary artery occlusion, whereas only 54% (130/242) of the remaining inferior infarctions involved that artery.
  
  
  CONCLUSIONS
  Inferior myocardial infarctions occur disproportionately at night, usually due to right coronary artery occlusion. This suggests that a protective role for sleep may be limited to left coronary artery-related events.
authors.affiliation: Centro Cardiologico Monzino, I.R.C.C.S., Institute of Cardiology, University of Milan, Milan, Italy. paolo.moruzzi@cardiologicomonzino.it
authors.forename: Paolo
authors.initials: P
authors.lastname: Moruzzi
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Marenzi
authors.forename: Sergio
authors.initials: S
authors.lastname: Callegari
authors.forename: Mauro
authors.initials: M
authors.lastname: Contini
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002940:Circadian Rhythm / Q000502:physiology*; D017023:Coronary Angiography; D003326:Coronary Circulation / Q000502:physiology; D023921:Coronary Stenosis / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology*; D003328:Coronary Thrombosis / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology; D005260:Female; D006801:Humans; D007558:Italy; D008297:Male; D008432:Mathematical Computing; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology*; D012044:Regression Analysis; D012189:Retrospective Studies; D012307:Risk Factors; D013564:Sympathetic Nervous System / Q000503:physiopathology