Heart Attack: any thing that causes your heart to fail of its job meaning it isn't pumping blood or oxygen. Say a mans heart just instantly stops the medical side of it is to assume that the man had a heart attack.
Heart Exhaustion: I think its simply in the name. Your heart gets tired and overworked. For example...a boy has an asthma attack. What happens? the boys lungs begin to get smaller and smaller which causes the heart to work even harder so much so that eventually the heart will give up because of heart exhaustion.
