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: Helge Røsjø, Gunnhild Kravdal, Arne Didrik Høiseth, Marit Jørgensen, Pirouz Badr, Ragnhild Røysland, Torbjørn Omland
• Journal: Clinical chemistry (Clin Chem) Vol. 58 Issue 11 Pg. 1565-73 (Nov 2012) ISSN: 1530-8561 [Electronic] England
• PMID: 22997281 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2012 American Association for Clinical Chemistry

Chemical References

• Troponin I

Topics

• Aged
• Exercise Test
• Female
• Humans
• Male
• Middle Aged
• Myocardial Ischemia (diagnosis, physiopathology)
• Myocardial Perfusion Imaging
• Prospective Studies
• Regression Analysis
• Sensitivity and Specificity
• Troponin I (blood)