In athletes under the age of 35 years the incidence of sudden death is low, most 
causes to be due to ventricular arrhythmias, usually provoked by exertion, and 
nearly always occur in the presence of structural heart disease or abnormalities 
in the conduction system. The most common structural disease is hypertrophic 
cardiomyopathy followed by coronary artery anomalies, idiopathic dilated 
cardiomyopathy, arrhythmogenic right ventricular dysplasia, aortic stenosis, 
myocarditis, the Wolff-Parkinson-White syndrome, and long QT syndrome. The 
evaluation of athletes with symptoms of cardiac arrhythmias, syncope, family 
history of sudden death require a complete cardiac workup. If they have 
documented hypertrophic cardiomyopathy, arrhythmogenic right ventricular 
dysplasia, idiopathic dilated cardiomyopathy, long QT syndrome, family history 
presentation with sudden death, and septal thickness greater than 20 mm 
competitive athletics are generally prohibited. In athletes with asymptomatic 
bradyarrhythmia, supraventricular tachycardias and atrial premature contractions 
without structural heart disease all competitive sports are allowed if heart 
rate in bradyarrhythmia appropriately increases with exercise. Athletes with 
premature ventricular contraction, nonsustained ventricular tachycardia and non 
structural heart disease are without athletic restriction as long as the 
arrhythmia does not worsen on exertion and cause dyspnea, presyncope or syncope.