Transient, high-grade atrioventricular block from high-dose cyclophosphamide.

Cyclophosphamide, an alkylation agent, is widely used in stem cell transplantation for its antineoplastic and myeloablative properties. Congestive heart failure, pericarditis, and arrhythmias are well-known cardiac sequelae of high-dose cyclophosphamide therapy; however, high-grade atrioventricular block has rarely been reported. We present the case of a 71-year-old man who developed a high degree of atrioventricular block several hours after therapy with high-dose cyclophosphamide. After treatment with a temporary pacemaker and cessation of cyclophosphamide, the patient experienced no more events. Before administering cyclophosphamide, evaluating patients for underlying conduction abnormalities is advisable. Agents other than cyclophosphamide are available.