Angiographic changes associated with recurrent reduction of carotid and cerebral blood flow in dogs, with special reference to transient focal cerebral ischemic attacks.

Morphological changes associated with recurrent reduction of blood flow in the partially constricted common carotid artery and that in the ipsilateral cerebrum were examined angiographically in anesthetized beagle dogs. During the recurrent reductions of carotid flow, spasm and small and multiple defects indicating platelet aggregates or thrombi in the constricted carotid segment were observed in 8 and 5 of 20 preparations, respectively. Also, large defects indicating thrombi were observed at the outlet of the constricted segment in the other 2 preparations. During the reduction of cerebral flow, spasm was observed in the internal carotid artery and cerebral arteries in 9 and 8 preparations, respectively. Also, obstruction of the cerebral arteries with "cut-off" sign indicating emboli was observed in the other 2 preparations. The changes appeared singly or in combination. It is suggested that spasm, platelet aggregates, thrombi and/or emboli were responsible for the recurrent reduction of carotid and cerebral blood flow.