Symptomatic Bradyarrhythmia Secondary to Risperidone

Mr. A, a 40-year-old man with a history of schizoaffective disorder and alcoholism, came to the emergency room with nausea, vomiting, and abdominal pain. He had been taking paroxetine, 10 mg/day, and risperidone, 2 mg/day. He denied any history of heart illness. Mr. A appeared diaphoretic and tremulous, was tachycardic with a heart rate of 102 bpm, and had a low-grade fever with a temperature of 99.8°F. Laboratory evaluation revealed a creatinine phosphokinase level of 2949 IU/liter with a normal MB fraction and a troponin-I concentration of 0.4 μg/liter. A 12-lead ECG showed sinus tachycardia, nonspecific ST-T abnormalities, and a QTc interval of 400 msec. Mr. A was admitted to a telemetry unit for alcohol withdrawal, mild rhabdomyolysis, and alcohol gastritis. Intravenous fluids, multivitamins, and lorazepam were administered. Subsequent creatinine phosphokinase and troponin levels showed substantial decreases. Because of worsening psychosis, the risperidone dose was increased to 6 mg/day on the second day of hospitalization. On the third day, Mr. A developed sinus bradycardia with 38 bpm and had several episodes of sinus pauses lasting 2.0 to 3.0 seconds associated with lightheadedness without hypotension. At this time the QTc interval was 410 msec. The results of a two-dimensional ECG were normal. Because of the temporal relationship of the bradyarrhythmias with the increase in the risperidone dose, risperidone treatment was discontinued. Over the next 48 hours of telemetry monitoring, there were no further sinus pauses and the sinus bradycardia resolved completely. Mr. A’s heart rate at the time of discharge was 78 bpm.