Doppler Ultrasound Studies of Subclavian Steal Hemodynamics in Subclavian Stenosis

By means of ultrasound Doppler sonography it is shown that a proximal subclavian stenosis does not necessarily influence the blood flow of the vertebral artery in a subclavian steal syndrome (permanent retrograde flow in the vertebral artery) as is characteristic for subclavian occlusion. Depending on the peripheral resistance in the cranial and brachial circulation, the vertebral artery competes with the brachial artery for the poststenotic flow. Thus, a reduction of the vertebral flow during hyperemia within the brachial artery ststem, alternating vertebral flow, or a temporary steal syndrome may result in stenosis. Obviously the relation of the flow resistance may also change within one pulse beat, so that in the vertebral artery a characteristic flow pulse, i.e., an alternating flow, is detected with opposite direction in systole and diastole.