Is there unstable angina in the era of high-sensitivity troponin?

Abstract

Since high-sensitive troponin detects minimal quantities of myocardial necrosis, the existence of unstable angina as an entity among acute coronary syndromes has been questioned. With the systematic use of high-sensitive troponin as a diagnostic and prognostic marker in acute coronary syndromes, the actual incidence and clinical profile of unstable angina remains unknown. Objectives:
To analyze the incidence and clinical profile of unstable angina with the use of high-sensitive troponin and to compare it with myocardial infarction. Methods: Clinical and epidemiological features has been surveyed in 344 patients admitted into the coronary care unit with acute coronary syndromes between June 2015 and February 2016, then classified as ST elevation AMI (STEMI), or non-ST elevation AMI (NSTEMI) in those with highsensitive troponin T above 14 ng/ml according to the third definition of myocardial infarction. The rest were considered unstable angina. Results: Among the 344 patients included, 182 (53%) were classified as Unstable Angina and 162 (47%) as AMI, from whom 96 patients (28%) were classified as ST elevation AMI (STEMI), and 66 patients (19%) as non-ST elevation AMI (NSTEMI). Patients with Unstable Angina were proportionally more diabetic (51 patients, 28% P=0.05), had more dyslipidemia (141 patients, 77% P=0.0001) there were more with previous myocardial infarction (53 patients, 30% P=0.01), and previous revascularization (95 patients, 13% P=0.0001), compared with Myocardial Infarction patients. Conclusions: Unstable Angina remains very frequent among the acute coronary syndromes even with the use of high-sensitive biomarkers. Patients with Unstable Angina seem to have a prior history of coronary burden with more incidence of previous myocardial infarction and previous revascularization, which could paradoxically protect from myocardial impairment.