Torsades de pointes in 3 patients with leukemia treated with arsenic trioxide

Arsenic trioxide is used in clinical trials in the treatment of relapsed and resistant cases of acute promyelocytic leukemia. Adverse effects from arsenic in these studies have been multisystemic. Arsenic is known to cause corrected QT-interval prolongation and T-wave changes, but the potential for serious ventricular arrhythmias is less well understood. Torsades de pointes, a form of ventricular tachycardia, has been reported with arsenic poisoning but not at therapeutic doses used in protocols for hematologic malignancies. We describe 3 patients in whom this arrhythmia developed while they were treated with arsenic trioxide. Early recognition of the arrhythmia or correction of contributory factors is important because arsenic induced ventricular arrhythmias are known to be resistant to most chemical methods and electrical cardioversion.