Blood flow and flow resistance in the vertebral arteries of patients with and without carotid atherosclerosis.

Abstract

In the present prospective study colour duplex ultrasound was used to investigate the vertebral arteries in 117 patients referred for carotid duplex examination. The study aimed to identify flow abnormalities and factors influencing blood flow haemodynamics by calculating the resistance index (RI) in the vertebral and common carotid arteries. Vertebral artery RI was decreased in patients with severe carotid artery disease (> or =80% stenosis or occlusion) caused mainly by an increased diastolic flow velocity. By contrast, patients without severe carotid artery disease showed an age-related increase in vertebral artery RI. The RI in the common carotid artery was increased in patients with local atherosclerosis in the carotid bulb, and was increased with age. There was significantly better visualization of the right vertebral artery origin than of the left (75% versus 62%, P<0.05). Stenotic lesions were found in 15% of the carotid bifurcations and in 7% of the vertebral arteries. It is concluded that vertebral artery haemodynamics can be evaluated using colour duplex ultrasound; however, there are difficulties in visualizing the vertebral artery origin, especially on the left side. Even at advanced age, the vertebral arteries can reduce flow resistance to maintain cerebral blood flow in patients with occluded or severely stenosed carotid arteries. RI in vertebral arteries in patients without severe carotid occlusive disease, and in common carotid arteries, is mainly affected by local atherosclerosis and age, which increase the flow resistance.