Turk Kardiyol Dern Ars. 2005; 33(4): 212-216

Evaluation of aspirin resistance in patients with coronary artery disease

Gültekin Faik Hobikoğlu¹, Tuğrul Norgaz¹, Hüseyin Aksu¹, Orhan Özer¹, Zekeriya Nurkalem¹, Mehmet Ertürk¹, Şennur Ünal Dayi¹, Ümit Akyüz², Ahmet Akyol¹, Ahmet Narin^1
1
2

OBJECTIVES
Although aspirin is widely used for secondary prevention of cardiovascular disease, its effect is not standard in all patients. We aimed to evaluate the frequency of aspirin resistance (AR) in patients taking aspirin for stable coronary artery disease (CAD) and the effect of AR on platelet sensitivity to adenosine diphosphate (ADP).
STUDY DESIGN
The study consisted of 100 patients (28 females, 72 males; mean age 56 years; range 30 to 75 years) who had been on aspirin treatment at least for the past seven days for stable CAD. Thirty healthy volunteers (10 females, 20 males; mean age 54 years) without a history of aspirin ingestion within the past seven days comprised the control group. Platelet function was measured by the PFA-100 system and the 95th percentile (170 sec) of the control group was defined as the cut-off value of the closure time at the collagen/epinephrine cartridge to determine AR.
RESULTS
Twenty-seven patients (27%) were found to have AR. Seventeen patients (17%) showed a prolonged closure time (range 171 sec to 212 sec) with a maximum increase by 25%, while 34 patients (34%) had no closure at the end of 300 sec. Patients with AR also showed an increased platelet sensitivity to ADP as shown by a significantly shorter closure time (70.0 sec) at the collagen/ADP cartridge compared to that of patients without AR (100.4 sec; p=0.007) or controls (79.0 sec; p=0.03). Patients with and without AR did not differ significantly with regard to age, sex, history of hypertension, diabetes mellitus, hyperlipidemia, smoking, family history of CAD, platelet count and mean platelet volume, and blood levels of urea and creatinine (p>0.05). The duration of aspirin usage and its formulation (enteric-coated or not) were not related with AR.
CONCLUSION
The effect of aspirin is not always desirable and the sensitivity of platelets to ADP is increased in patients with AR, requiring to individualize the antiplatelet treatment.

Keywords: Aspirin/adverse effects; cardiovascular diseases/drug therapy/complications; drug resistance; platelet aggregation/drug effects; platelet function tests

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