Aspirin resistance in ischaemic heart disease

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.

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.

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%.

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).

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