Clinical introduction A 22-year-old man was referred to us for syncope during a game of Captain's ball. There was no prodrome. His friends did not notice any ictal movements. He was otherwise well prior to passing out. He was not taking any medications or supplements. He was not usually physically active, but was otherwise well with no significant medical history. This is his first episode of syncope. There was no history of cardiac arrest or seizures. There is no family history of premature sudden cardiac death.

Physical examination was normal. ECG at rest demonstrated sinus rhythm with corrected QT interval of 400 ms. Echocardiography revealed a structurally normal heart. Holter monitoring was normal. Treadmill exercise stress test demonstrated the following rhythm on figure 1 during stage 4 Bruce protocol. Stress test was terminated in view of sustained arrhythmia as illustrated. He felt light-headed during the period, but otherwise felt that he could carry on with the exercise. ECG during recovery was unremarkable.

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Figure 1

ECG recording of the patient during exercise stress test.