Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Heart Attack ?
    ### Response:
    Blood Flow to the Heart Is Blocked The heart works 24 hours a day, pumping oxygen and nutrient-rich blood to the body. Blood is supplied to the heart through its coronary arteries. If a blood clot suddenly blocks a coronary artery, it cuts off most or all blood supply to the heart, and a heart attack results.
    