Prognostic Value of Cardiac Troponin I Measured With a Highly Sensitive Assay in Patients With Stable Coronary Artery Disease

Study Questions:

What is the prognostic value of cardiac troponin I (TnI) levels, measured with a new high-sensitivity assay, in low-risk patients with stable coronary artery disease (CAD), in contrast to that of high-sensitivity cardiac troponin T (hs-TnT)?

Methods:

hs-TnI levels at baseline were assessed in 3,623 patients with stable CAD and preserved systolic function enrolled in the PEACE (Prevention of Events With Angiotensin-Converting Enzyme Inhibitor Therapy) trial. Cox proportional hazards regression models were estimated to test the relationships between hs-TnI and the composite outcome of cardiovascular death or nonfatal heart failure, and between hs-TnI and nonfatal acute myocardial infarction (AMI).

Results:

In total, 98.5% of patients had hs-TnI concentrations higher than the detection level (1.2 pg/ml). hs-TnI correlated moderately with hs-TnT (r = 0.44) and N-terminal pro–B-type natriuretic peptide (NT-proBNP) (r = 0.39), but only weakly with age (r = 0.17) and estimated glomerular filtration rate (r = -0.11). During a median follow-up period of 5.2 years, 203 patients died of cardiovascular causes or were hospitalized for heart failure, and 209 patients had nonfatal myocardial infarctions. In analyses adjusting for conventional risk markers, NT-proBNP, and hs-TnT, hs-TnI levels in the fourth compared with the three lower quartiles were associated with the incidence of cardiovascular death or heart failure (hazard ratio [HR], 1.88; 95% confidence interval [CI], 1.33-2.66; p < 0.001). There was a significant, albeit weaker association with nonfatal myocardial infarction (HR, 1.44; 95% CI, 1.03-2.01; p = 0.031). In the same models, hs-TnT concentrations were associated with the incidence of cardiovascular death or heart failure, but not of MI.

Conclusions:

The authors concluded that in patients with stable CAD, hs-TnI concentrations are associated with cardiovascular risk independently of conventional risk markers and hs-TnT.

Perspective:

This study suggests that small elevations in hs-TnI are associated with the incidence of cardiovascular death or heart failure in patients with stable CAD and provide incremental prognostic information to conventional risk markers, including hs-TnT. Furthermore, the correlation between hs-TnI and hs-TnT concentrations was of only moderate strength, suggesting that mechanisms of release and/or degradation may differ between the troponins in the chronic setting. Also worth noting is that hs-TnI, but not hs-TnT, was significantly associated with the risk for AMI. It appears that chronic, low-grade elevation of hs-TnI and hs-TnT in patients with stable CAD may reflect different pathophysiological mechanisms, and may need different therapeutic responses.

Keywords: Prognosis, Coronary Artery Disease, Biological Markers, Troponin I


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