Critical Stenosis of the Carotid Artery in the Dog

Critical stenosis was determined for the canine carotid artery. With all four cephalic vessels patent, the critical stenosis was demonstrated to be 81%, at which level a 15% reduction in flow occurred. The superimposition of bilateral vertebral artery and contralateral carotid artery occlusion lowered the level of critical stenosis to 72% luminal constriction. When both exter nal carotid arteries were ligated and common carotid artery flow represented internal carotid flow, critical stenosis was determined to be 90%, and this did not change with superimposed bilateral vertebral arterial and con tralateral carotid arterial occlusion.