A new study suggests that cardiac troponin predicts myocardial infarction or cardiovascular death in patients with chronic coronary artery disease (CAD) independent of cardiovascular risk factors and disease severity. Results from the Myocardial Injury in patients referred for Coronary Angiography (MICA) study reveal that patients with CAD, troponin concentrations were twofold higher in those with an event compared with those without (median 6.7 ng/L [interquartile range (IQR): 3.2-14.2 ng/L] vs 3.3 ng/L [IQR: 1.7-6.6 ng/L]; P < 0.001). Troponin concentrations were associated with the primary outcome (myocardial infarction or cardiovascular death during follow-up) after adjusting for cardiovascular risk factors and CAD severity (adjusted hazard ratio [HR]: 2.3; 95% confidence interval [CI]: 1.7-3.0, log10 troponin; P < 0.001). A troponin concentration >10 ng/L identified patients with a 50% increase in the risk of myocardial infarction or cardiovascular death. “Although we demonstrate cardiac troponin is a powerful predictor of cardiovascular events in patients with chronic coronary artery disease, the mechanisms of troponin release that underpin this observation remain unclear,” the study team, led by Ryan Wereski, MD, of the University of Edinburgh, Scotland, wrote. Cell necrosis role The paper, which was published Monday online and appears in the Aug. 8 issue of the Journal of the American College of Cardiology, cites studies demonstrating that irreversible cell necrosis is responsible for cardiac troponin release in acute myocardial infarction. Here, the research team commented, “Whether irreversible cell necrosis is also responsible for elevated cardiac troponin concentrations in patients with chronic coronary artery disease is not known, and other release mechanisms may be responsible.” The findings are the subject of an accompanying editorial comment, in which Yader Sandoval, MD, from the Abbott Northwestern Hospital in Minneapolis, and Allan S. Jaffe, MD, from the Mayo Clinic in Rochester, Minnesota, discussed the evolving role of cardiac troponin. The authors raised the question of whether high-sensitivity cardiac troponin (hs-cTn) measurements, like in acute coronary syndrome (ACS), identified high-risk chronic coronary syndrome (CCS) patients as likely to benefit from coronary revascularization. Citing a study demonstrating that increasing severity of angina is associated with worse outcomes because of more adverse anatomy, the authors commented that hs-cTn may be beneficial in higher-risk patients with more symptoms rather than in those with mild or no symptoms. Impact of ORBITA results The editorial also included emerging data that suggested many hs-cTn increases in this population reflected chronic cardiac comorbidities rather than reversible myocardial ischemia alone. In the Objective Randomized Blinded Investigation with optimal medical Therapy of Angioplasty in stable angina (ORBITA), no significant reduction was observed in resting or exercise-induced high sensitivity troponin I (hs-cTnI) concentrations compared with placebo. This was despite reductions in ischemia in patients with severe, single-vessel CAD randomized to percutaneous coronary intervention. “Integrating hs-cTn measurements before and after coronary revascularization represents an opportunity to clarify the role of hs-cTn as a risk-stratification tool for CCS as well as improve processes to assess periprocedural myocardial injury,” the editorialists commented. They went on to conclude, “The role of cTn continues to evolve beyond ACS, with emerging data such as in MICA supporting its application as a risk-stratification tool in patients with CCS. “Although more data are needed to understand how to use this prognostic information to improve outcomes, the measurement of hs-cTn in patients with chronic CAD may serve multiple functions.” Study methodology The prospective cohort nature of the MICA study identified 4,240 suitable patients (median age 66 years; IQR: 59-73 years; 33% female). These patients had symptoms suggestive of stable angina and underwent outpatient coronary angiography. In addition, high-sensitivity cardiac troponin I was measured before angiography, and clinicians were blinded to the results. Clinical care was not directly altered by cardiac troponin testing. These patients were then stratified according to troponin concentrations, which were classified as low (<5 ng/L), intermediate (5 ng/L to the sex-specific 99th percentile), or high (above the sex-specific 99th percentile) based on previous research. Out of these patients, 3,888 (92%) patients were identified as having CAD, of which primary outcome events were recorded in 255 (6%) during a median follow-up of 2.4 years (IQR: 1.3-3.6 years). Sources: Wereski R, Adamson P, Shek Daud NS, et al. High-Sensitivity Cardiac Troponin for Risk Assessment in Patients With Chronic Coronary Artery Disease. J Am Coll Cardiol. 2023;82:473–485. Sandoval Y, Jaffe AS. The Evolving Role of Cardiac Troponin: From Acute to Chronic Coronary Syndromes. J Am Coll Cardiol. 2023;82:486 – 488. Image Credit: Innovative Creation – stock.adobe.com