Abstract | BACKGROUND: Numerous studies have indicated that some patient subpopulations do not respond to the antithrombotic effects of aspirin. The objective of this study was to evaluate aspirin-induced inhibition of platelet cyclooxygenase (COX) using a flow cytometric technique in long-term aspirin users after carotid endarterectomy (CEA) and controls with newly diagnosed carotid stenosis not taking aspirin and to compare these results with platelet function analyzer measurements. METHODS: The study included 86 patients with a history of CEA on long-term aspirin therapy (100 mg daily) and 29 age-matched patients with newly diagnosed carotid artery stenosis not taking aspirin. Platelet-rich plasma diluted with phosphate-buffered saline was incubated with arachidonic acid (ARA) at a final concentration of 80 micromol/L. After staining with phycoerythrin-labeled anti- P-selectin (CD62p) antibody, platelet CD62p-antigen expression was measured on a flow cytometer. RESULTS: Flow cytometric measurement of ARA-induced platelet activation showed an inhibition of ARA-induced platelet stimulation in all patients on aspirin therapy, whereas all but two controls (95%) showed expected platelet reactivity. In contrast, results of the platelet function analyzer measurements were normal in 16% of aspirin-treated patients. CONCLUSIONS: Flow cytometric measurement of CD62p expression on platelets after incubation with ARA proved to be a practicable tool to monitor aspirin-induced inhibition of platelet COX. Results in patients on long-term low-dose aspirin therapy show that the inability of aspirin to inhibit platelet COX for both symptomatic and asymptomatic patients with high-grade internal carotid artery stenosis is a very rare event. So-called aspirin resistance detected quite frequently by platelet function analyzer measurement is most likely from COX-independent mechanisms.
|
Authors | Afshin Assadian, Jaqueline Lax, Ursula Meixner-Loicht, Georg W Hagmüller, Peter Michael Bayer, Wolfgang Hübl |
Journal | Journal of vascular surgery
(J Vasc Surg)
Vol. 45
Issue 6
Pg. 1142-7; discussion 1147
(Jun 2007)
ISSN: 0741-5214 [Print] United States |
PMID | 17543677
(Publication Type: Comparative Study, Journal Article)
|
Chemical References |
- Cyclooxygenase Inhibitors
- Fibrinolytic Agents
- P-Selectin
- Arachidonic Acid
- Prostaglandin-Endoperoxide Synthases
- Aspirin
|
Topics |
- Aged
- Arachidonic Acid
(pharmacology)
- Aspirin
(pharmacology, therapeutic use)
- Blood Platelets
(drug effects, enzymology, immunology)
- Carotid Stenosis
(blood, drug therapy, surgery)
- Case-Control Studies
- Cyclooxygenase Inhibitors
(pharmacology, therapeutic use)
- Drug Resistance
- Endarterectomy, Carotid
- Female
- Fibrinolytic Agents
(pharmacology, therapeutic use)
- Flow Cytometry
- Humans
- Male
- P-Selectin
(metabolism)
- Platelet Function Tests
(methods)
- Prostaglandin-Endoperoxide Synthases
(metabolism)
- Severity of Illness Index
|