Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) supravalvular aortic stenosis ?
    ### Response:
    Supravalvular aortic stenosis (SVAS) is a heart defect that develops before birth. This defect is a narrowing (stenosis) of the large blood vessel that carries blood from the heart to the rest of the body (the aorta). The condition is described as supravalvular because the section of the aorta that is narrowed is located just above the valve that connects the aorta with the heart (the aortic valve).
    