Aspirin failure in patients presenting with acute cerebrovascular ischaemia
Thrombosis and Haemostasis, 08/03/2011
Halawani SHM et al. – Incomplete platelet inhibition is common around the time of acute cerebrovascular ischaemic events in patients prescribed aspirin. Up to 50% of these observations appear due to incomplete adherence to aspirin therapy.Methods
- The authors studied 51 adults admitted with suspected ischaemic stroke and already prescribed daily aspirin.
- Within 48 hours (h) of onset, blood and urine samples were collected to assess platelet aggregation, activation and aspirin response by a range of methods.
- All tests were then repeated on a second sample taken 24 h after witnessed administration of 75 mg or 150 mg aspirin.
- At entry to the study, incomplete response to aspirin, measured by arachidonic acid (AA)–stimulated platelet aggregation, was found in 43% of patients.
- Following in–hospital aspirin administration, there was a significant decrease in AA–aggregation (p=0.001) suggesting poor adherence to therapy prior to admission.
- However, residual aggregation (10–15%) persisted in 11 subjects – suggesting alternative causes.
- In incomplete responders on admission, platelet aggregation with adenosine diphosphate (ADP) was significantly higher compared with responders (p<0.05) but there were no significant differences in collagen aggregation, platelet fibrinogen binding or P–selectin expression, plasma von Willebrand factor, fibrinogen, high–sensitivity C–reactive protein, or the urinary metabolite, 11–dehydro–TxB2.