Background: Patients with unstable angina (UA) are regarded to be at low risk for future coronary events. Guidelines discourage routine coronary angiography and recommend early discharge after individualized risk stratification. The relative value of clinical risk indicators as compared to cardiac troponin (cTn) alone is unsettled in the era of high-sensitivity cardiac troponin (hsTn) assays. We aimed to investigate the clinical characteristics, therapies, and outcomes of UA patients with different hsTnT concentrations.
Methods: During 12 months, 2525 patients were enrolled. UA was defined as unstable symptoms and either undetectable (< 5 ng/L), normal (5-14 ng/L) or stable elevated hsTnT (15-51 ng/L). Follow-up for 1-year mortality was available in 98.7%.
Results: A total of 280 patients (11.1%) received a diagnosis of UA. Mortality rates at 12 months were 0%, 1.9% and 6.9% in presence of undetectable, normal and stable elevated hsTnT. Elevated hsTnT > 99th percentile but not unstable symptoms carried an independent 3.25-fold (1.78-5.93) higher risk for all-cause death after adjustment for other clinical risk indicators or the GRACE score. Utilization of guideline-recommended therapies was high albeit lower than for non-ST-elevation myocardial infarction (NSTEMI). Significantly fewer patients with UA received dual antiplatelet therapy (DAPT, odds ratio (OR) 0.51 [95% CI 0.44-0.59], P < 0.0001), coronary angiography (CA, OR 0.79, [95% CI 0.74-0.87], P < 0.0001), and percutaneous coronary intervention (PCI, OR 0.50, [95% CI 0.40-0.61], P < 0.0001), compared to NSTEMI. However, prevalence of significant obstructive coronary artery disease requiring PCI was 31.8%, even in patients with undetectable hsTnT, indicating the need for stress testing.
Conclusions: The current dichotomization of patients into UA and NSTEMI is no longer appropriate. Additional risk stratification seems warranted including the presence and magnitude of hsTn concentration and additional risk indicators. Clinical Trials Identifier: NCT03111862.
Keywords: Acute coronary syndrome; High-sensitivity troponin; Real-world evidence; Unstable angina.