Patients' thromboembolic potential after carotid endarterectomy is related to the platelets' sensitivity to adenosine diphosphate.
Background and purpose 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.


METHODS
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 micromol/L), collagen (10 to 50 mg/mL), and arachidonic acid (3 or 6 micromol/L), and fibrinogen binding to GPIIb-IIIa was measured by whole blood flow cytometry in response to ADP (0.1 to 10 micromol/L) and thrombin (0.02 to 0.16 micro/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 (n = 88).


RESULTS
The platelet response to ADP was significantly higher in the patients 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.


CONCLUSIONS
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.
Hayes
Paul D
PD
Departmernt of Surgery, University of Leicester, Leicester Royal Infirmary, Clinical Sciences Building, Leicester, LE3 1LJ, UK. paul.hayes@easynet.net.uk
Box
Helen
H
Tull
Samantha
S
Bell
Peter R F
PR
Goodall
Alison
A
Naylor
A Ross
AR
D000244:Adenosine Diphosphate / Q000008:administration & dosage*; D016893:Carotid Stenosis / Q000601:surgery; D003094:Collagen / Q000008:administration & dosage; D004305:Dose-Response Relationship, Drug; D016894:Endarterectomy, Carotid / Q000009:adverse effects*; D006490:Hemostatics / Q000008:administration & dosage; D006801:Humans; D066298:In Vitro Techniques; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects*; D012307:Risk Factors; D013917:Thrombin / Q000008:administration & dosage; D013923:Thromboembolism / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology*; D014463:Ultrasonography
D006490:Hemostatics; D000244:Adenosine Diphosphate; D003094:Collagen; D013917:Thrombin