Arrhythmias are not infrequently documented in athletes and can be a source of morbidity and mortality, particularly ventricular tachyarrhythmias leading to sudden cardiac death (SCD). It is therefore important to establish guidelines for screening of athletes with two goals in mind:
- To document the presence of arrhythmia and underlying structural heart disease that place the athlete at risk for sudden death.
- To evaluate the importance of an arrhythmia in assessing the athlete's eligibility for competition.
This topic will discuss specific arrhythmias or arrhythmia-related syndromes and their importance in athletes. The risk is related to the intensity and type of exercise (figure 1) . The risk of sudden death in athletes, particularly those with underlying heart disease, the approach to screening to prevent sudden death in athletes, and the management of conduction disturbances in athletes are discussed elsewhere. (See "Risk of sudden cardiac death in athletes" and "Electrocardiographic abnormalities and conduction disturbances in athletes" and "Screening to prevent sudden cardiac death in athletes".)
Syncope in an athlete is an important symptom that requires a thorough evaluation. A common cause of syncope in young athletes is neurally mediated (vasovagal) syncope, which is generally unassociated with cardiac disease [2-5]. This type of syncope is due to neurally mediated mechanisms, but hypovolemia from unreplaced fluid losses may contribute in athletes. Athletes (especially those engaged in endurance disciplines) may also be more susceptible to neurally mediated syncope by nature of their increased vagal tone . (See "Pathogenesis and etiology of syncope".)
However, underlying structural heart disease and other causes should be eliminated before considering neurally mediated syncope as the etiology. Among the pathologic cardiac causes of exertional syncope are ventricular tachycardia and obstruction resulting from hypertrophic cardiomyopathy or aortic stenosis, and hypotension due to vagally-mediated vasodepression in patients with hypertrophic cardiomyopathy. Exercise associated syncope may also be related to hyponatremia or hyperthermia as a result of intense or prolonged exercise. (See "Evaluation of syncope in adults" and "Clinical manifestations, diagnosis, and evaluation of hypertrophic cardiomyopathy", section on 'Syncope'.)