title: Implication of different cardiac troponin I levels for clinical outcomes and prognosis of acute chest pain patients.
abstract: OBJECTIVE
  We compared outcomes in patients with non-ST-segment elevation acute coronary syndromes (ACS) according to the degree of cardiac troponin I (cTnI) elevation.
  
  
  BACKGROUND
  Controlled trials of high-risk patients have found that troponin elevations identify an even higher risk subset. It is unclear whether outcomes are similar among a lower risk, heterogeneous patient group. Also, few studies have reported outcomes other than myocardial infarction (MI) or death, based on the peak troponin value.
  
  
  METHODS
  Consecutively, admitted patients without ST-segment elevation on the initial electrocardiogram underwent serial marker sampling using creatine kinase (CK), CK-MB fraction, and cTnI. Patients were grouped according to peak cTnI: negative = no detectable cTnI; low = peak greater than the lower limit of detectability but less than the optimal diagnostic value; intermediate = peak greater than or equal to the optimal diagnostic value but less than the manufacturer's suggested upper reference limit (URL); and high = peak greater than or equal to the URL. Thirty-day outcomes included cardiac death, MI based on CK-MB, revascularization, significant disease, and a reversible defect on stress testing. Six-month mortality was also determined. Negative evaluations for ischemia included nonsignificant disease, no reversible stress defect, and negative rest perfusion imaging.
  
  
  RESULTS
  Of the 4,123 patients admitted, 893 (22%) had detectable cTnI values. Cardiac events and positive test results at 30 days and 6-month mortality increased significantly with increasing cTnI values. Negative evaluations for ischemia were significantly and inversely related to peak cTnI values. Although adverse events were significantly more common in patients with a low cTnI value than in those with negative cTnI, negative evaluations for ischemia were frequent.
  
  
  CONCLUSIONS
  Increased cTnI values are associated with worse outcomes. Although low cTnI values are associated with adverse events, they do not have the same implication as higher cTnI values, and nonischemic evaluations are frequent.
authors.affiliation: Department of Internal Medicine, Cardiology Division, Medical College of Virginia, Virginia Commonwealth University, 12th and Marshall Streets, Richmond, VA 23298-0051, USA. mkontos@hsc.vcu.edu
authors.forename: Michael C
authors.initials: MC
authors.lastname: Kontos
authors.forename: Rakesh
authors.initials: R
authors.lastname: Shah
authors.forename: Lucie M
authors.initials: LM
authors.lastname: Fritz
authors.forename: F Philip
authors.initials: FP
authors.lastname: Anderson
authors.forename: James L
authors.initials: JL
authors.lastname: Tatum
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Ornato
authors.forename: Robert L
authors.initials: RL
authors.lastname: Jesse
mesh_terms: D000787:Angina Pectoris / Q000453:epidemiology* / Q000209:etiology / Q000378:metabolism* / Q000401:mortality; D015415:Biomarkers; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data; D005260:Female; D006746:Hospital Bed Capacity, 500 and over; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000453:epidemiology / Q000209:etiology / Q000378:metabolism / Q000401:mortality; D011237:Predictive Value of Tests; D011379:Prognosis; D016019:Survival Analysis; D019210:Troponin I / Q000378:metabolism*; D014768:Virginia / Q000453:epidemiology
chemical_list: D015415:Biomarkers; D019210:Troponin I