Prior exposure to aspirin in acute coronary syndrome patients: a cardiovascular risk marker or a predictor of adverse outcome? A contemporary data of a national registry

Despite the known protective cardiovascular effect of aspirin, former studies identified its prior exposure to an acute coronary syndrome (ACS) as an independent risk factor for adverse events. However, those studies did not reflect contemporary approaches. In the current study, we determine whether patients exposed to aspirin before an ACS have a worse cardiovascular risk profile and if it predicts higher risk of recurrent cardiovascular events or mortality. A cohort of patients enrolled in a national registry of ACS was analyzed according to prior exposure to aspirin. A propensity score standardized patients according to baseline comorbidities. Multivariable COX regression analysis was performed in unmatched and matched populations for a primary endpoint (composite of all-cause mortality and/or cardiovascular rehospitalization) and two secondary endpoints (all-cause mortality and cardiovascular rehospitalization, separately) at 1-year follow-up. Among 5533 ACS patients, 1763 were previously exposed to aspirin. They were older and had more comorbidities; contemporary approaches, both coronary angiography and percutaneous coronary angioplasty were less likely to be performed. Before matching the population, prior exposure to aspirin was an independent predictor of primary composite endpoint (p = 0.002) and cardiovascular rehospitalization as the secondary endpoint (p = 0.001). There were no statistically significant differences between both groups in the multivariable model for the primary or secondary endpoints after matching. Previous exposure to aspirin identified ACS patients with worse baseline characteristics, establishing its role as a cardiovascular risk marker. However, our data do not support including aspirin pretreatment in risk stratification scores as an adverse prognostic variable.