Sudden death in young athletes is not frequent but there are still many high-profile tragedies occurring every year. The most common cause of sudden death (death within one hour of the onset of symptoms) in the normal population is coronary artery disease. A sudden rupture of an atherosclerotic plaque in a coronary artery can lead to an accumulation of platelets and blood clot, which may completely occlude the diseased artery and cause a heart attack. This may be complicated by dangerous heart rhythm disturbances, including ventricular fibrillation (uncoordinated heart contractions with no cardiac output) and sudden death.

In athletes, the most common cardiac congenital anomaly is hypertrophic cardiomyopathy - abnormal thickening of the heart muscle walls - which is responsible for about 50% of sudden deaths in people under 35. Other possible causes of sudden death in young people are congenital abnormalities of coronary arteries (blood vessels that feed the heart muscle), myocarditis (inflammation of the heart muscle), arrhythmogenic right ventricular cardiomyopathy (ARVC, disease of the muscle of the right ventricle leading to heart failure and arrhythmias), dilated cardiomyopathy (enlarged and weakened heart), aortic stenosis (stiff and rigid aortic valve), and channelopathies (disturbance in the function of ion channels in membranes of heart muscle cells, such as LQTS - long QT syndrome, Brugada syndrome and catecholaminergic polymorphic ventricular tachycardia - CPVT).

Studies have shown that most of the athletes, who experienced sudden death, have never had any cardiac symptoms. Only in 25% of those athletes, cardiovascular disease is suspected or diagnosed before death. A degree of controversy exists over what level of screening is appropriate before engaging in competitive sports. Routine clinical tests include physical examination, ECG, echocardiogram and ergometry (treadmill test). Early indicators that can suggest a hidden cardiovascular disorder are episodes of unexplained chest pain, prolonged palpitations, blackouts, presence of murmurs on an investigation, abnormal ECG and family history of sudden death. Athletes with these signs and symptoms require thorough cardiovascular examination and testing.