Presentation of Case A 65-year-old woman was admitted to the hospital for electrophysiologic studies because of ventricular tachycardia. There was a long history of a bipolar affective disorder that was managed with haloperidol and benztropine. The patient was well in other respects until 10 days earlier, when vomiting and diarrhea developed in her and several of her relatives. Four days later the patient entered another hospital because of increasing fatigue, dyspnea, and epigastric pain. On physical examination the blood pressure was 87/54 mm Hg and the heart rate was 220. An electrocardiogram showed a wide-complex tachyarrhythmia with a morphologic pattern.