The clinical significance of aspirin resistance in patients with chest pain.

BACKGROUND

There are conflicting data in the literature about the clinical significance of aspirin resistance.

HYPOTHESIS

We aimed to prospectively evaluate the prevalence of biochemical aspirin resistance in patients on aspirin therapy who were admitted to the emergency clinic with chest pain. We also aimed to evaluate the relation between acute coronary syndromes (ACS) and aspirin resistance.

METHODS

A total of 338 patients were included in the study. Platelet reactivity was measured with the PFA-100 system (Dade Behring Inc, Deerfield, IL). Aspirin resistance determined by the PFA-100 was defined as a normal collagen and/or epinephrine closure time despite aspirin treatment (<165 s).

RESULTS

Patients were divided into 4 groups: stable angina pectoris (SAP), unstable angina/non-ST-elevation myocardial infarction (UA/NSTEMI), ST-elevation myocardial infarction (STEMI), and rule out ACS. Aspirin resistance was found in 81 (24%) patients in all groups. Patients with ACS had significantly more aspirin resistance than patients with rule out ACS or patients with SAP (P < .001). In the SAP group, 31 (19.6%) patients; in the UA/NSTEMI group, 19 (35.8%) patients; in the STEMI group, 14 (50%) patients; and in the rule out ACS group, 17 (17.2%) patients had aspirin resistance (P < .001). In the multivariate analysis, cardiac biomarker elevation on admission to emergency department and platelet count appeared as independent factors predictive of aspirin resistance.

CONCLUSIONS

We demonstrated that incidence of aspirin resistance was significantly higher in patients who were finally diagnosed as ACS, especially in aspirin-taking patients admitted to the emergency clinic with STEMI.