The frequency of aspirin resistance by a modified thrombelastography method and its relationship with clinical and laboratory parameters in patients with stable coronary artery disease

OBJECTIVES: Aspirin is the cornerstone of antiplatelet therapy in cardiovascular medicine. However, aspirin resistance has been demonstrated in 0.4% to 83.3% of aspirin-receiving patients. The aim of this study was to investigate the frequency of aspirin resistance using a modified thrombelastography (mTEG) method and related clinical and biochemical parameters in patients with stable coronary artery disease (CAD), who received 100 mg/day aspirin. STUDY DESIGN: The study included 168 patients (115 males, 53 females; mean age 60±8 years) with stable CAD, receiving aspirin at a dose of 100 mg/day. Aspirin responsiveness was determined using mTEG, where aspirin resistance was defined as arachidonic acid-induced whole blood platelet aggregation inhibition (PAI) of less than 50%. RESULTS: Aspirin resistance was detected in 27 patients (16.1%). Platelet aggregation inhibition showed negative correlations with hyperlipidemia, smoking, spironolactone use, systolic blood pressure, pulse pressure, and total cholesterol and fibrinogen levels. In multivariate regression analysis, only fibrinogen level (OR=1.063, p=0.010) and pulse pressure (OR=1.197, p=0.023) were found to be independent indicators of aspirin resistance and PAI. In ROC analysis, cut-off values of 50 mmHg for pulse pressure and 400 mg/dl for fibrinogen level predicted aspirin resistance with 88.9% and 74% sensitivity and 64.4% and 68% specificity, respectively. CONCLUSION: Our findings suggest that measurements of fibrinogen level and pulse pressure may be used as easy and reliable methods in predicting aspirin resistance.