Sudden cardiac death (SCD) associated with athletic activity is a rare but devastating event. Victims are usually young and apparently healthy, but many have underlying cardiovascular disease that is not diagnosed until after the event. As a result, there is great interest in detecting such abnormalities early, and then defining appropriate activity restrictions for affected individuals to minimize the risk of SCD.
The majority of SCD events in athletes are due to malignant arrhythmias, usually ventricular tachycardia (VT) or ventricular fibrillation (VF). In the small number of individuals with certain cardiac disorders, athletics may increase the likelihood of these events in two ways: prolonged physical training induces changes in cardiac structure (eg, chamber dilation and physiologic hypertrophy) that may create arrhythmic substrate, and the immediate physiologic demands of intense athletics may trigger malignant arrhythmias and SCD in susceptible individuals with underlying cardiac abnormalities.
The potential for SCD associated with athletic activity generates two questions:
- How should individuals be evaluated prior to initiating athletic activity?
- What restrictions should be placed upon individuals with known cardiovascular disease?
Answers to these questions are complicated and controversial, and vary based upon three factors: