Ultrasonic duplex scanning in atherosclerotic disease of the innominate, subclavian and vertebral arteries. A comparative study with angiography.

Ultrasonic duplex scanning of the vertebral artery has a sensitivity of 0.80 and a specificity of 0.83 for the detection of an obstructive lesion of 50% or more at the site of the ostium. For the subclavian arteries these values are respectively 0.73 and 0.91. For both vessels the test has a very high negative predictive value of respectively 0.96 and 0.97. Therefore duplex ultrasound scanning is a reliable test in screening patients suspected of multi-level atherosclerotic disease of the extracranial cerebral vessels. The problem remains in classifying the degree of stenosis. In the case of the vertebral artery the sample volume of the pulsed Doppler is usually too large in relation to the vessel diameter. In the case of the subclavian and innominate artery one of the main problems is the range of the pulsed Doppler system. A subclavian steal syndrome is easily diagnosed without any special test.