Troponin levels within the normal range and probability of inducible myocardial ischemia and coronary events in patients with acute chest pain

Abstract

Background/objectives: Patients with suspected acute coronary syndromes and negative cardiac troponin (cTn) levels are deemed at low risk. Our aim was to assess the effect of cTn levels on the frequency of inducible myocardial ischemia and subsequent coronary events in patients with acute chest pain and cTn levels within the normal range.

Methods: We evaluated 4474 patients with suspected acute coronary syndromes, nondiagnostic electrocardiograms and serial cTnI levels below the diagnostic threshold for myocardial necrosis using a conventional or a sensitive cTnI assay. The end points were the probability of inducible myocardial ischemia and coronary events (i.e., coronary death, myocardial infarction or coronary revascularization within 3 months).

Results: The probability of inducible myocardial ischemia was significantly higher in patients with detectable peak cTnI levels (25%) than in those with undetectable concentrations (14.6%, p<0.001). These results were consistent regardless of the type of cTnI assay, the type of stress testing modality, or the timing for cTnI measurement, and remained significant after multivariate adjustment (odds ratio [OR] 1.47, 95% confidence interval [CI] 1.21-1.79, p<0.001). The rate of coronary events at 3 months was also significantly higher in patients with detectable cTnI levels (adjusted OR 2.08, 95% CI 1.64-2.64, p<0.001).

Conclusions: Higher cTnI levels within the normal range were associated with a significantly increased probability of inducible myocardial ischemia and coronary events in patients with suspected acute coronary syndromes and seemingly negative cTnI.

Keywords: Acute coronary syndrome; Chest pain; Exercise testing; Troponin.