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Biphasic vertebral artery flow

With biphasic vertebral artery flow, flow is antegrade during early systole and diastole but retrograde during late systole. This is a more severe steal than that of early systolic deceleration and correlates with more severe steno-occlusive disease of the corresponding subclavian or innominate (brachiocephalic) artery. (Contributed by Dr. Douglas Lanska.)