Background and Objectives: Increased levels of high-sensitivity cardiac troponin (hs-cTn) are the main criteria that differentiate non-ST segment elevation myocardial infarction (NSTEMI) from unstable angina (UA). How are these implemented in clinical practices? This study aims to detect cases of misdiagnosed UA instead of NSTEMI. Materials and Methods: We analysed discharge summaries of 840 patients admitted to Vilnius University Hospital Santaros Klinikos with the diagnosis of UA in 2017-2018. We retrospectively checked symptoms, levels of hs-cTn, coronary angiography and electrocardiogram changes with an aim to differentiate UA and type 1 NSTEMI, according to the Fourth Universal Definition of Myocardial Infarction. We excluded patients with missing hs-cTn levels or coronary angiography. Results: We found that 46.71% (n = 334) of patients met the diagnostic criteria of UA according to the Fourth Universal Definition, whereas 19.16% of patients (n = 137) could have been diagnosed with type 1 NSTEMI instead of UA. In the group of patients who could be reclassified to type 1 NSTEMI, the median level of hs-cTn was 184.32 [226.15] ng/L on admission. The median of the lowest level during the hospitalization was 114.0 [207.4] ng/L. Median highest-304.0 [257.6] ng/L. Myocardial infarction with non-obstructive coronary arteries could have been diagnosed in 3.36% (n = 24) of patients. Conclusions: Only less than half of patients met the diagnostic UA criteria. Almost one-fifth of patients with a diagnosis of UA could be reclassified to type 1 NSTEMI.
Keywords: NSTEMI; guidelines; high sensitivity troponin; requalification; unstable angina.