A heart attack is in some ways a complex situation in terms of the entire body. But the cause is very simple. The cause of a heart attack is a clot forming in a narrowing in one of the arteries to the heart and the clot obstructs the vessel and prevents blood supply to the heart muscle. As a result of that a part of the heart begins to die. There has been tremendous progress in preventing damage to the heart and preventing that part of the heart muscle from dying.