After a brief revision about the long QT syndrome, we report the case of a 52 year old man admitted to hospital for a syncopal attack. His electrocardiogram was considered normal: sinus bradycardia and U waves were recorded. The echocardiogram revealed anterior mitral leaflet redundancy and possible tricuspid prolapse. During the atropine test, after a normal increment of sinus frequency, 2 runs of self-limited torsade de pointes appeared. The electrocardiogram showed lesion wave at first, and then prolonged QT. During the intracavitary study, premature ventricular stimulation caused torsade de pointes. After propranolol iv it was no more possible to induce major ventricular arrhythmias anymore. Coronarography was normal. Nadolol therapy was begun. On 6 months follow-up the patient is asymptomatic.