Dr Stitt practises emergency medicine at the University of British Columbia Hospital in Vancouver. QUESTIONS A previously healthy 20-year-old man presents with a complaint of syncope while riding up a hill on his bicycle. He was able to stop and sit down in the seconds before he passed out. There was no trauma. He recalls waking with a severe headache and being taken to hospital where he was assessed. After feeling much improved, he was discharged with a diagnosis of vasovagal syncope. His family physician assessed him the next day and, concerned with his story, referred him to another emergency department. He looks well, results of his physical examination are entirely normal, and he is now asymptomatic. What is worr ying about this stor y? What tests, if any, are indicated?