Aspirin resistance in ischaemic heart disease.

Background: In spite of the usage of acetylsalicylic acid (aspirin) in the secondary prevention of ischaemic heart disease (IHD), new thrombo-embolic events occur in more than half of patients. Aspirin resistance may be partially responsible for this phenomenon.

Aim: To assess the prevalence of aspirin resistance in patients with IHD and to correlate this phenomenon with the progression of atherosclerosis, concomitant diseases and other medication.

Methods: The study group consisted of 205 patients (mean age 65.8 years, 95 females) with stable angina, recent coronary angiography and positive result of non-invasive stress tests, treated with 75 mg of aspirin for at least one week. Platelet aggregation was measured using the optical aggregation method. Aspirin resistance was defined as a mean collagen and ATP-induced platelet aggregation >70%.

Results: Aspirin resistance was found in 41 (20%) patients and was significantly associated with previous coronary artery bypass grafting (CABG) (p<0.01) and three-vessel disease (p<0.05). Previous CABG was the only independent risk factor for the presence of aspirin resistance (OR 5.6; 95% CI 2.0-15.4; p<0.01).

Conclusions: Aspirin resistance is present in 20% of patients with stable angina. Previous CABG is an independent risk factor of this phenomenon.