The ECG and rhythm strips are from a 56 year old female who was receiving quinidine sulfate, 325mg three times daily, for the prevention of paroxysmal atrial fibrillation. The ECG was recorded following an episode of syncope and shows sinus bradycardia, biphasic (positive-negative) T waves in leads V3 and V4 and a rather unimpressive U wave (arrow) in leads V2, V3 and V4. The rhythm strips below the tracing show prominent U waves following the long pauses (arrow), ventricular premature beats alone and in pairs, and an episode of torsade de pointes