Exercise-induced asystole with syncope in a healthy young man.

Exercise-related syncope is frequently an ominous symptom associated with advanced cardiovascular disease. Asystole during or after exercise is a rare occurrence in persons with structural heart disease and is an even rarer cause of syncope in healthy persons. Herein we report on a healthy 40-year-old man who was hospitalized after a syncopal episode that followed playing basketball. He recalled several near-syncopal episodes after strenuous exercise over the past 6 months, during which time he used marijuana. A loss of sinoatrial activity and appearance of ventricular asystole occurred immediately after monitored exercise to suggest parasympathetic dominance, which could be related to long-term cannabinoid use.