Abstract You are asked to see a 58-year-old lady on the cardiac surgical ICU who has recurrent ventricular fibrillation. You are told that she has had an aortic valve replacement that day which was uneventful, although she has marked left ventricular hypertrophy. She was otherwise well preoperatively except for controlled hypertension. Postoperatively she was noted to have become bradycardic, rate 40/min, shortly before going into ventricular tachycardia which rapidly regenerated to ventricular fibrillation. She responded to a 220 J DC shock, emerging into a broad complex bradycardia of 40/min with a BP of 95/40 mmHg (MAP 55 mmHg) for some minutes before again degenerating to ventricular tachycardia/fibrillation (VTNF). This sequence of events was repeated twice more despite the administration of 100 mg of lignocaine intravenously. Prior to her first arrest she was ventilated with good blood gases, normal acid-base status, and blood biochemistry.