Immunohistochemistry of carotid plaque neovascularization and vasa vasorum.

Carotid artery surgical specimens from 15 consecutive patients undergoing carotid endarterectomy were studied in an attempt to identify morphologic differences between carotid artery plaque neovascularization (NV) and normal vasa vasorum (VV). The patients included 12 men and 3 women with an age range of 55-81 years (mean, 67). Nine of them had ischemic symptoms directly related to the plaque being removed. The specimens were stained with hematoxylin-eosin, Verhoef-Van Gieson, and factor VIII-related antigen techniques. In addition, normal carotid arteries were obtained for comparison from two autopsies of young individuals, victims of traumatic death. The severity of NV within the plaque was graded based on the appearance and location of new vessels, as they compared to W. Mild NV (Grade I) was found in 3/15, whereas moderate and severe (Grades II and III) were each found in 6/15 cases. Increasing severity of NV was associated with more tortuosity, thicker walls, and location closer to the carotid lumen. The presence and severity of NV did not correlate with plaque thickness (p = 0.2), the presence of symptoms (p = 0.5), or any other risk factors for stroke. Carotid plaque NV seems independent of the degree of atheroma and morphologically different than VV. Its origin, true incidence, and role in the production of carotid intraplaque hemorrhage and increased stroke risk are still uncertain. This is the first immunohistochemical study of carotid plaque neovascularization.