Incidence and outcomes of unstable angina compared with non-ST-elevation myocardial infarction.

Objective: Assess the relative incidence and compare characteristics and outcome of unstable angina (UA) and non-ST-elevation myocardial infarction (NSTEMI).
Design: Two independent prospective multicentre diagnostic studies (Advantageous Predictors of Acute Coronary Syndromes Evaluation [APACE] and High-Sensitivity Troponin in the Evaluation of Patients With Acute Coronary Syndrome [High-STEACS]) enrolling patients with acute chest discomfort presenting to the emergency department. Central adjudication of the final diagnosis was done by two independent cardiologists using all clinical information including serial measurements of high-sensitivity cardiac troponin (hs-cTn). All-cause death and future non-fatal MI were assessed at 30 days and 1 year.
Results: 8992 patients were enrolled at 11 centres. UA was adjudicated in 8.9%(95% CI 8.0 to 9.7) and 2.8% (95% CI 2.3 to 3.3) patients in APACE and High-STEACS, respectively, and NSTEMI in 15.1% (95% CI 14.0 to 16.2) and 13.4% (95% CI 12.4 to 14.3). Coronary artery disease was pre-existing in 73% and 76% of patients with UA. At 30 days, all-cause mortality in UA was substantially lower as compared with NSTEMI (0.5% vs 3.7%, p=0.002 in APACE, 0.7% vs 7.4%, p=0.004 in High-STEACS). Similarly, at 1 year in UA all-cause mortality was 3.3% (95% CI 1.2 to 5.3) vs 10.4% (95% CI 7.9 to 12.9) in APACE, and 5.1% (95% CI 0.7 to 9.5) vs 22.9% (95% CI 19.3 to 26.4) in High-STEACS, and similar to non-cardiac chest pain (NCCP). In contrast, future non-fatal MI in APACE was comparable in UA and NSTEMI (11.2%, 95% CI 7.8 to 14.6 and 7.9%, 95% CI 5.7 to 10.2), and higher than in NCCP (0.6%, 95% CI 0.2 to 1.0).
Conclusions: The relative incidence and mortality of UA is substantially lower than that of NSTEMI, while the rate of future non-fatal MI is similar.
Competing Interests: Competing interests: Dr CP reports a personal grant from the PhD Educational Platform Health Sciences, outside this study. Dr MG report no conflicts of interest. Dr PDA reports grants from New Zealand Heart Foundation, during the conduct of the study, and grants from AstraZeneca, outside the submitted work. Dr AS reports other from Abbott Diagnostics, during the conduct of the study. Dr AA reports personal fees from Abbott Diagnostics, outside the submitted work. Dr MRG received speaker honoraria from Abbott, outside the submitted work. Dr RT reports grants from Swiss National Science Foundation (grant number P300PB-167803), personal fees from Roche Diagnostics, personal fees from Abbott, personal fees from Siemens, outside the submitted work. Dr TR has received research grants from the Goldschmidt-Jacobson Foundation, the Swiss National Science Foundation (PASMP3-136995), the Swiss Heart Foundation, the Professor Max Cloëtta Foundation, the University of Basel and the University Hospital Basel as well as speaker honoraria from Brahms and Roche, outside the submitted work. Dr NLM reports grants and personal fees from Abbott Diagnostics, Roche Diagnostics and Singulex outside the submitted work. Dr CM has received research support from the Swiss National Science Foundation, the Swiss Heart Foundation, the KTI, the Stiftung für kardiovaskuläre Forschung Basel; Abbott, Alere, AstraZeneca, Beckman Coulter, Biomerieux, Brahms, Roche, Siemens, Singulex, Sphingotec and the Department of Internal Medicine, University Hospital Basel, as well as speaker honoraria/consulting honoraria from Abbott, Alere, AstraZeneca, Biomerieux, Boehringer Ingelheim, BMS, Brahms, Cardiorentis, Novartis, Roche, Siemens and Singulex, during conduct of this study. All other authors report no conflicts of interest with this study.
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