What Is A Heart Attack A heart attack can catch you completely off guard irrespective of age. Heart disease is a universal health threat that can hit at any time. When the blood supply to a portion of the heart is cut off, the heart muscle cannot receive oxygen, which results in a heart attack. That area of the heart starts to die if the blood flow is not soon restored. The degree of the damage can range from minor to severe or even life-altering, depending on how long the blood supply is cut off. If you don’t recognize the heart attack symptoms, it can prove fatal.