- Subclavian steal syndrome occurs when hemodynamically significant stenosis or occlusion in the subclavian artery proximal to the vertebral artery origin causes flow reversal in the ipsilateral vertebral artery effectively shunting blood away from the brain to feed the hungry ipsilateral arm.
Right innominate artery injection reveals right subclavian artery occlusion proximal to right vertebral artery origin.
Left subclavian artery injection illustrates classic subclavian steal phenomenon with flow reversal in the right vertebral artery to perfuse the right arm.