Patients' thromboembolic potential after carotid endarterectomy is related to the platelets' sensitivity to adenosine diphosphate

Postoperative microemboli in patients undergoing carotid endarterectomy are a significant risk factor for stroke. These emboli can be detected by intraoperative transcranial Doppler monitoring. They are not linked to technical error and are variable between patients. As it is known that platelets play a key role in arterial thrombosis, it was hypothesized that a patient's risk of postoperative carotid thrombosis was linked to the individual's platelet response to physiologic agonists. Blood samples from 120 patients undergoing carotid endarterectomy were analyzed before surgery. Platelet aggregation was measured in response to adenosine diphosphate (ADP) (0.5 to 4 μmol/L), collagen (10 to 50 mg/mL), and arachidonic acid (3 or 6 μmol/L), and fibrinogen binding to GPIIb-IIIa was measured by whole blood flow cytometry in response to ADP (0.1 to 10 μmol/L) and thrombin (0.02 to 0.16 μ/mL). Patients underwent intraoperative transcranial Doppler monitoring for 3 hours after surgery, and platelet functional data of those who had >25 emboli in this period (n = 22) were compared with the data of those with 25 emboli, as measured both by aggregometry ( P = .0012) and by flow cytometry ( P < .0001). Platelet aggregation with collagen was also significantly higher in this group ( P = .0018), but the response to thrombin was not statistically different in the two groups. In addition, there was no difference in the response to arachidonic acid between the groups. The platelet response to ADP may be linked to clinical outcome, and thus, specific ADP receptor inhibitors may be appropriate for this group of patients.