Heart attacks happen when blood stops flowing to the heart causing damage to the muscle of the heart. Heart attacks occur when blood flowing to the heart, which brings oxygen, is either completely or partially blocked as a result of narrowing of the arteries that are the avenues by which blood flows to the heart. The buildup of fat cholesterol in addition to other substances aptly referred to as plaque block arterial pathways with a mixture of cholesterol, fatty substances, calcium, cellular waste products, and fibrin, which clots the blood.