The effect of acetylsalicylic acid resistance on prognosis of patients who have developed acute coronary syndrome during acetylsalicylic acid therapy

Aim The relationships between clinical events and acetylsalicylic acid resistance (AR), as well as its frequency, have been established in stable patients with coronary artery disease (CAD). Although acute coronary syndrome (ACS) patients taking acetylsalicylic acid have been accepted as a high-risk population, the role of AR has not been investigated in these patient groups. Thus, in the present study, the impact of AR was investigated in patients with ACS who were taking acetylsalicylic acid. Methods Between January 2001 and February 2003, 140 ACS patients were included in the present prospective study. All patients had ACS while taking acetylsalicylic acid. Coronary angiographic scores for severity and extent of CAD were determined for all patients. The effect of acetylsalicylic acid on platelet function was assessed by the platelet function analyzer PFA-100 (Dade Behring, USA). The primary end point was the composite of death, myocardial infarction, cerebrovascular accident and revascularization. The mean follow-up period was 20 months. Results Patients with AR were older than patients without AR (63.8 ± 10.8 years versus 58.3 ± 11.2 years; P=0.005). Moreover, myocardial damage was higher in patients with AR according to cardiac troponin T values (1.11 ± 1.3 μg/L versus 0.41 ± 0.5 μg/L; P = 0.01). The composite end point of death, myocardial infarction, cerebrovascular accident or revascularization was present in 16 of 45 patients (35%) with AR and in 13 of 79 patients (16%) without AR (hazard ratio 2.46, 95% CI 1.18 to 5.13; P = 0.016). After adjustment for age, platelet count, cardiac troponin T value and CAD severity score, AR remained an independent predictor for long-term adverse events (hazard ratio 3.03, 95% CI 1.06 to 8.62; P = 0.038). Conclusions The clinical event rate was found to be higher in ACS patients with AR than in those without AR. Thus, it may be concluded that there is a strong correlation between a worse prognosis and AR in these patients.