Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Prinzmetal's variant angina ?
    ### Response:
    What causes Prinzmetal's variant angina? Prinzmetal's variant angina is caused by coronary artery spasms. A coronary artery spasm is a temporary, abrupt, and focal (restricted to one location) contraction of the muscles in the wall of an artery in the heart.
    