Appropriateness of Antiplatelet Pretreatment in Non-ST-segment Elevation Acute Coronary Syndrome: Differences Between Unstable Angina and Acute Myocardial Infarction

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Objective: To evaluate the appropriateness of antiplatelet pretreatment in patients with non-ST-segment elevation acute coronary syndrome (NSTE-ACS). To determine whether the appropriateness differs between patients with unstable angina and those with acute myocardial infarction.

Materials and methods: This prospective observational single-centre study (June 2021–February 2022) included patients with NSTE-ACS scheduled to undergo coronary angiography. This research was approved by an ethical committee.

We designed an algorithm to classify pretreatment as appropriate or inappropriate according to the angiographic findings of coronary arteries. We used multivariate analyses to identify variables associated with appropriate pretreatment.

Results: We included 172 consecutive patients with NSTE-ACS (mean age 68.7 years; initial diagnosis: unstable angina in 29.7%, non-ST-segment elevation MI (NSTEMI) in 65.1%, others in 5.2%).

Antiplatelet pretreatment was administered in 76.6% of the patients and the time from pretreatment and coronary angiography was >24 hours in 50.9% of patients.

Drug pretreatment was classified as appropriate in 70.2% of all patients, in 78.2% of those with NSTEMI and in 47.2% of those with unstable angina (p<0.05).

Conclusion: Antiplatelet pretreatment was appropriate in most patients with NSTEMI, but in less than half of those with unstable angina, suggesting a high rate of diagnostic error in unstable angina. Selecting appropriately the patients who really need pretreatment might avoid unnecessary drug side-effects, invasive angiography as well as reduce hospital admissions and costs.