Twelve-lead electrocardiograms revealed fine atrial fibrillation and a short QT interval (SQTI) (<300 milliseconds) with an average ventricular rate of 54/min in a 20-year-old male presented with exertional dyspnea. His echocardiographic evaluation revealed interatrial septal aneurysm and slightly dilated pulmonary artery. An electrophysiologic study revealed atrial fibrillation with a very high frequency, short ventricular effective refractory period (130 milliseconds) and ventricular fibrillation inducible with 3 short coupled extrastimuli. Signs were consistent with the rare SQTI syndrome. Although SQTI syndrome is associated with increased risk for sudden cardiac death, the patient was free of arrhythmia symptoms and denied any syncope or presyncope. Family history was also negative for sudden cardiac death and for any symptom suggestive of arrhythmia. The patient refused implantable defibrillator and was treated with anticoagulation and quinidine therapy.