Embolic infarcts of carotid origin differ in size and site with contralateral carotid patency.

Carotid emboli cause small infarcts in the ipsilateral hemisphere in rats when the contralateral carotid artery is fully patent. With contralateral carotid occlusion, embolic infarcts, both large and small, occur with equal proportions in both hemispheres. To determine if emboli also cross to the territory of a stenotic carotid artery, we combined high grade (78-96%) stenosis of the left common carotid artery with photochemically-induced (laser irradiation 632 nm, 200 mW/cm2, 15 min; intravenous Photofrin II, 12.5 mg/kg) embolism from the right common carotid artery in 12 rats. Ninety-eight cerebral infarcts occurred in 9 experimental animals, with eight infarcts being large (> 2.5 mm). The mean proportions of infarcts and emboli on the left were 25% and 19%, respectively. These results suggest that contralateral carotid artery stenosis, like occlusion, will influence the site and size of embolic infarcts and that the "symptomatic" carotid artery cannot always be determined by the side of the cerebral infarct.