title: Initial risk stratification and presenting characteristics of patients with evolving myocardial infarctions.
abstract: OBJECTIVE
  To describe the presenting characteristics and risk stratification of patients presenting to the emergency department with chest pain who have a normal initial troponin level followed by a raised troponin level within 12 h (evolving myocardial infarction (EMI)).
  
  
  METHODS
  Data from the Internet Tracking Registry for Acute Coronary Syndromes (i*trACS), a registry of patients presenting with undifferentiated chest pain, were used. This analysis included patients without ST segment elevation with at least two troponin assay results < or = 12 h apart. Patients were stratified into three groups: EMI (initial troponin assay negative, second troponin assay positive), non-ST elevation myocardial infarction (NSTEMI) (initial troponin assay positive) and no MI (all troponin assays negative).
  
  
  RESULTS
  Of 4136 eligible patients, 5% had EMI, 8% had NSTEMI and 87% had no MI. Patients with EMI were more similar to those with NSTEMI than those with no MI with respect to demographic characteristics, presentation, admission patterns and revascularisation. The initial ECG in patients with EMI was most commonly non-diagnostic (51%), but physicians' initial impressions commonly reflected MI, unstable angina or high-risk chest pain (76%). This risk assessment was followed by a high rate of critical care admissions (32%) and revascularisation (percutaneous coronary intervention 17%) among patients with EMI.
  
  
  CONCLUSIONS
  Patients with EMI appear similar at presentation to those with NSTEMI. Patients with EMI are perceived as being at high risk, evidenced by similar diagnostic impressions, admission practices and revascularisation rates to patients with NSTEMI.
authors.affiliation: Department of Emergency Medicine, Wake Forest University Health Sciences, Medical Center Blvd, Winston Salem, NC 27157-1089, USA. cmiller@wfubmc.edu
authors.forename: C D
authors.initials: CD
authors.lastname: Miller
authors.forename: G J
authors.initials: GJ
authors.lastname: Fermann
authors.forename: C J
authors.initials: CJ
authors.lastname: Lindsell
authors.forename: K W
authors.initials: KW
authors.lastname: Mahaffey
authors.forename: W F
authors.initials: WF
authors.lastname: Peacock
authors.forename: C V
authors.initials: CV
authors.lastname: Pollack
authors.forename: J E
authors.initials: JE
authors.lastname: Hollander
authors.forename: D B
authors.initials: DB
authors.lastname: Diercks
authors.forename: W B
authors.initials: WB
authors.lastname: Gibler
authors.forename: J W
authors.initials: JW
authors.lastname: Hoekstra
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000787:Angina Pectoris / Q000209:etiology*; D004562:Electrocardiography; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data; D004638:Emergency Treatment; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis*; D011446:Prospective Studies; D018570:Risk Assessment; D012737:Sex Factors; D014336:Troponin / Q000378:metabolism
chemical_list: D014336:Troponin