In younger people, sudden death is a rare event, but since it often involves people involved in athletics, cases are often reported in the press. The most common cause is hypertrophic cardiomyopathy (hypertrophy=to grow abnormally large + cardio=heart + myopathy = diseased muscle). This disease is often hereditary, and the walls of the ventricle are larger than they should be. This makes the pumping chamber of the heart smaller, and the heart has to work harder to pump blood out of the heart. As well, the thickened muscle narrows the space for the blood to flow through the aortic valve and to the rest of the body. During exercise, this decreased blood flow can irritate the heart muscle itself and cause ventricular fibrillation, collapse, and sudden death. Anomalous coronary arteries can also cause sudden death in the young. The heart is a muscle itself, and like any muscle, it needs blood supply to provide oxygen for it to work. Normally, the coronary arteries lie on the surface of the heart. Anomalous arteries dive into the heart muscle itself and may be occluded when the heart muscle that surrounds the abnormally placed artery squeezes aggressively, as with exercise, shutting off blood supply to part of the heart. This irritates the electrical system and can cause ventricular fibrillation and sudden death. The pre-participation athletic physical examination is a useful tool to screen children andadolescents for their risk of sudden cardiac arrest. Commotio cordis is a situation in which the heart stops when the chest is hit by an object. News stories occasionally report of baseball players who are hit in the chest by a ball and collapse because their heart stops beating. The heart sits behind the breastbone, and the electrical system can be short circuited when a direct blow is sustained.