Indium-111-labeled platelet scintigraphy in carotid atherosclerosis.

We evaluated platelet accumulation in carotid arteries by means of a dual-radiotracer method, using indium-Ill-labeled platelets and technetium-99m-4abeled human serum albumin, in 123 patients (92 men, 31 women; median age 60 years). Sixty patients had symptoms of transient ischemic carotid artery disease, and 63 patients with peripheral arterial occlusive disease served as controls. Antiplatelet treatment with acetylsalicylic acid was taken by 53 of the 123 patients. In 36 of the 60 symptomatic patients, platelet scintigraphy was repeated 3- 4 days after carotid endarterectomy. Comparison of different scintigraphic parameters (platelet accumulation index and percent of the injected dose of labeled platelets at the carotid bifurcation) showed no significant differences between symptomatic and asymptomatic patients, and the severity of stenosis and the presence of plaque ulceration also had no influence on the parameters. There was no difference between patients with a short (<4 weeks) or long (>4 weeks) interval from the last transient ischemic attack to scintigraphy and no difference between patients with or without antiplatelet treatment. Classifying the patients according to plaque morphology judged by high-resolution real-time ultrasonography also demonstrated no differences. No significant correlation was found between any scintigraphic parameter and other platelet function parameters such as platelet survival time, platelet turnover rate, and concentration of platelet-specific proteins. Quantification of platelet deposition after carotid endarterectomy in 36 patients demonstrated a significant increase of the median platelet accumulation index and the percent injected dose index. There were no significant differences between patients receiving high-dose (1.0 g/day) or low-dose (0.1 g/day) acetylsalicylic acid in scintigraphic results. The presence and amount of scintigraphically detectable platelet deposition after carotid endarter- ectomy was of no prognostic value concerning the risk of a postoperative neurologic deficit or of developing severe restenosis within the first few months. We conclude that platelet scintigraphy with the dual-radiotracer method has no value in the clinical investigation of carotid artery disease. (Stroke 1989;20:27-33) A therosclerotic stenosis of the internal carotid ZA artery is a common cause of stroke or A. \. transient ischemic attacks (TIAs), either by hemodynamic causes or by platelet emboli released from thrombi deposited on atheromatous lesions. 1 - 2 Intravascular platelet deposition and the in vivo effectiveness of drugs may be monitored scintigraph- ically by the use of indium-Ill-labeled autologous platelets. However, the results of studies using platelet scintigraphy in carotid atherosclerosis have