You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is In subclan steal syndrome there is reversal of blood flow in: and explain in detail?
In subclan steal syndrome there is retrograde flow in the veebral aery due to an ipsilateral subclan aery block proximal to veebral aery origin. The block results in lower pressure in the distal subclan aery and upper limb ischemia. Consequently, blood flows from the contralateral veebral aery to the basilar aery and then in a retrograde direction down the ipsilateral veebral aery away from the brainstem.