Biochemical aspirin resistance in acute stroke patients and its association with clinical factors: a prospective pilot study

Introduction
Aspirin is still widely used in treatment and prevention of cardiovascular diseases. To predict which patients cannot benefit from aspirin due to aspirin resistance remains a great clinical challenge.

Material and methods
Fifty one acute stroke/transient ischemic attack (TIA) patients (ASG) with a history of regular aspirin intake for the previous 7 days or more were included to the study within 24 hours of symptoms onset. Twenty nine patients admitted to our department for other reasons were the controls (CG). Each patient underwent routine blood tests (white blood cells, platelets, total cholesterol, C-reactive protein) and additional blood test: glycated haemoglobin (HbA1c), insulin, and N-terminal prohormone of brain natriuretic peptide (NT-proBNP). Biochemical aspirin resistance was measured using the VerifyNow Aspirin platelet function analyzer.

Results
There were 9 aspirin resistance patients in ASG (17.5%) and 3 in CG (10.3%) (p = 0.38). There were no differences in either age or gender between those groups. Twelve aspirin-resistant patients differed from aspirin nonresistant patients in age, NT-proBNP and total cholesterol levels (univariate model, p = 0.004, 0.04, 0.02, respectively). In a multivariate model patients aged 76 years and more would likely to be aspirin resistant with odds ratio = 9 (95% confidence interval: 1-78).

Conclusions
Patients aged 76 and more can be more likely aspirin resistant than younger patients. We believe that especially in the elderly with congestive heart failure there is a strong need for further investigations in this field, including searching for alternative antiplatelet therapies.