Syncope secondary to ventricular asystole in an endurance athlete.

Vasovagal syncope occurred in an endurance athlete prior to exercise as the result of a 22-second episode of complete heart block with ventricular asystole and subsequent sinoatrial arrest. The subject suffered a head injury but recovered without sequelae. Noninvasive cardiac testing was unrevealing. Although lesser disturbances of cardiac rhythm and conduction in athletes are not uncommon, extreme changes as illustrated by this case are rare. Close supervision of athletes undergoing exercise testing is advised.