Platelet deposition at carotid endarterectomy sites in humans.

Following carotid endarterectomy, early postoperative thrombosis or late restenosis occurs in up to 20% of vessels. Both complications may be related to platelet mechanisms. To assess platelet deposition at endarterectomy sites, we injected indium-111 labelled platelets in 24 men less than 30 minutes after carotid endarterectomy, with subsequent imaging 24-96 hours later. To determine if deposition decreased over time, 12 patients had follow-up studies 0.5-24 months later. For comparison, 2 control groups were studied: 1) patients with noncarotid surgery (n = 6) and 2) normal young subjects without endarterectomy and without evidence of carotid disease (n = 12). Quantitative analysis was performed performed using a deposition index that compared activity in operated with unoperated sites in surgical patients or activity in the right with left carotid arteries in normal subjects. Patients with recent endarterectomy had a mean deposition index of 1.7 +/- 0.5 (range 1.2-3.5) compared with a similarly determined ratio of 1.1 +/- 0.1 in normal subjects and 1.2 +/- 0.1 in the surgical controls (both p less than or equal to 0.05 vs. acute endarterectomy). At follow-up after endarterectomy, the mean deposition index decreased to 1.0 +/- 0.1, documenting reduced platelet deposition over time. We conclude that the arterial injury of carotid endarterectomy results in early platelet deposition, which is no longer present in most patients who are studied late. These findings suggest a reduction in platelet thrombus formation with time and are compatible with reendothelialization of the endarterectomized surface. This model may be useful for the in vivo assessment of therapies designed to reduce platelet accumulation following endothelial injury in humans.