title: Troponin I measured by a high-sensitivity assay in patients with suspected reversible myocardial ischemia: data from the Akershus Cardiac Examination (ACE) 1 study.
abstract: BACKGROUND
  Whether cardiac troponin concentrations are increased by reversible myocardial ischemia is controversial. Differences in the structure of cardiac troponin I (cTnI) and cTnT may have implications for diagnostic utility.
  
  
  METHODS
  cTnI was measured with a prototype high-sensitivity (hs) assay in 198 patients referred for myocardial perfusion imaging (MPI) before exercise stress testing, immediately after, and 1.5 and 4.5 h later. We categorized patients according to MPI results and compared hs-cTnI concentrations with hs-cTnT concentrations.
  
  
  RESULTS
  Baseline hs-cTnI was higher in patients with reversible myocardial ischemia (n = 19) vs the other patients (n = 179): median 4.4 (quartiles 1-3: 2.3-7.1) vs 2.5 (1.4-4.3) ng/L, P = 0.003. Baseline hs-cTnI and hs-cTnT concentrations were correlated (r = 0.46, P < 0.001) and the areas under the ROC curve for hs-cTnI and hs-cTnT in diagnosing reversible ischemia were similar: 0.71 vs 0.69, P = 0.77. Whereas hs-cTnI increased immediately after exercise (P < 0.001 vs baseline measurements) in patients without ischemia, it increased after 4.5 h in patients with reversible ischemia (P = 0.01). The increment in hs-cTnI concentrations was comparable between groups; thus, measuring hs-cTnI after exercise stress testing did not improve diagnostic accuracy over baseline measurements, and hs-cTnI concentrations were not found to be associated with reversible myocardial ischemia in multivariate analysis. By linear regression analysis, age, male sex, history of hypertension, angiotensin-converting enzyme inhibitor use, and lower left ventricular ejection fraction were associated with higher baseline hs-cTnI concentrations.
  
  
  CONCLUSIONS
  In patients referred to MPI, hs-cTnI concentrations were not closely associated with reversible myocardial ischemia, but rather were influenced by variables associated with structural alterations of the myocardium.
authors.affiliation: Department of Cardiology, Division of Medicine, Akershus University Hospital, Lørenskog, Norway.
authors.forename: Helge
authors.initials: H
authors.lastname: Røsjø
authors.forename: Gunnhild
authors.initials: G
authors.lastname: Kravdal
authors.forename: Arne Didrik
authors.initials: AD
authors.lastname: Høiseth
authors.forename: Marit
authors.initials: M
authors.lastname: Jørgensen
authors.forename: Pirouz
authors.initials: P
authors.lastname: Badr
authors.forename: Ragnhild
authors.initials: R
authors.lastname: Røysland
authors.forename: Torbjørn
authors.initials: T
authors.lastname: Omland
mesh_terms: D000368:Aged; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000175:diagnosis* / Q000503:physiopathology; D055414:Myocardial Perfusion Imaging; D011446:Prospective Studies; D012044:Regression Analysis; D012680:Sensitivity and Specificity; D019210:Troponin I / Q000097:blood*
chemical_list: D019210:Troponin I