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Troponin I Measured by a High-Sensitivity Assay in Patients with Suspected Reversible Myocardial Ischemia: Data from the Akershus Cardiac Examination (ACE) 1 Study

2012; American Association for Clinical Chemistry; Volume: 58; Issue: 11 Linguagem: Inglês

10.1373/clinchem.2012.190868

1530-8561

Helge Røsjø, Gunnhild Kravdal, Arne Høiseth, Marit E. Jørgensen, Pirouz Badr, Ragnhild Røysland, Torbjørn Omland,

Cardiovascular Effects of Exercise

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.