There is no difference. A cardiac arrest is the medical term for what we commlonly call a heart attack. It is the result of a blockage in an artery that nourishes the hearts cutting off blood flow to the heart and damaging part of the heart muscle. The blockage can be created by a build up of hardened arteries (placque) or by a blood clot in the heart, or a combination of both.
Cardiac arrest, or heart attack, is the most common form of heart disease, but not the only one.