Hs-TnI in Stable Chest Pain Patients

Study Questions:

What is the prognosis of outpatients with stable chest pain and high-sensitivity troponin I (hs-TnI) levels within normal range (<6 ng/L)?

Methods:

Hs-TnI levels were measured in 4,021 outpatients with chest pain using a novel highly sensitive assay that counts individual molecules of troponin. Participants had been enrolled in the PROMISE (Prospective Multicenter Imaging Study for Evaluation of Chest Pain) trial, and randomized to the computed tomography angiography group. The authors report the association between hs-TnI levels stratified by quartiles and 1-year outcomes; specifically, death, acute myocardial infarction (MI), or hospitalization for unstable angina.

Results:

The median hs-TnI level for the entire cohort was 1.6 ng/L, with the cutoff for the highest quartile being >2.6 ng/L. Patients in the higher quartiles had a higher prevalence of coronary artery disease and risk factors, and were more likely to have typical angina. At 1 year, 74 participants (1.8%) met the primary composite endpoint of death, acute MI, or hospitalization for unstable angina, and 28 (0.7%) experienced cardiovascular death or MI. There was no statistically significant difference in the incidence of cardiovascular death or acute MI between hs-TnI quartiles. Only when unstable angina is added to the composite outcomes does the difference reach statistical significance. A log increase in hs-TnI was associated with a 54% increase in the risk of events, and addition of hs-TnI to a base clinical model slightly improved the C-statistic from 0.65 to 0.69. Hs-TnI was best predictive of outcomes up to 90 days after measurement.

Conclusions:

Differences in low levels of hs-TnI are prognostic in outpatients with stable chest pain.

Perspective:

The authors interpret their findings as suggestive of a potential role for hs-TnI in the evaluation of chest pain as an alternative to imaging, which may be costly and not available. In the discussion, they provide the example of “high” concentrations (remains undefined) being potentially a trigger to directly proceed to angiography rather than stress testing. The study design and findings do not provide the framework to make such implications. The tools available for risk stratification of patients with cardiovascular disease are numerous and extend beyond biomarkers. However, their usefulness is defined by the availability of strategies that would alter that risk. In the absence of those strategies, advocating for widespread use of an ultrasensitive hs-TnI measurement at ranges generally defined as low risk may lead to overutilization of resources, increase in iatrogenic complications, and unnecessary patient and provider anxiety.

Clinical Topics: Acute Coronary Syndromes, Cardiovascular Care Team, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Stable Ischemic Heart Disease, Atherosclerotic Disease (CAD/PAD), ACS and Cardiac Biomarkers, Interventions and ACS, Interventions and Coronary Artery Disease, Interventions and Imaging, Angiography, Computed Tomography, Nuclear Imaging, Chronic Angina

Keywords: Acute Coronary Syndrome, Angina Pectoris, Angina, Stable, Angiography, Biomarkers, Chest Pain, Coronary Angiography, Coronary Artery Disease, Myocardial Infarction, Risk Factors, Troponin I, Tomography, X-Ray Computed


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