Cardiac arrest is what happens when your heart stops beating due to some kind of malfunction. A heart attack is what happens when something is blocking blood flow to your heart.
What is a heart attack?
Like all the other muscles in your body, your heart requires a steady supply of oxygen-rich blood to keep going. Your coronary arteries are the highway that delivers that blood. When those get blocked—with plaque or a blood clot—parts of your heart muscle start to atrophy and die.