Heart after a heart attack. Gross specimen of a sectioned heart where infarction (tissue death, dark areas in the walls of the heart) has taken place. This causes the pain of a heart attack. The blood has also clotted on the interior surfaces of the heart (a mural thrombus). Tissue death in the heart is usually caused by a blockage of the blood flow through the coronary arteries that supply oxygenated blood to the heart muscle. A heart attack can be rapidly fatal. It is a common cause of death, linked to a sedentary lifestyle, stress, obesity and cigarette smoking.