Arrhythmogenic effects of arsenic trioxide in patients with acute promyelocytic leukemia and an electrophysiological study in isolated guinea pig papillary muscles.

Background: Arsenic trioxide (As(2)O (3)) is a new promising regimen for patients with a relapse of acute promyelocytic leukemia (APL), but causes life-threatening arrhythmias. This study aimed to investigate the incidence and mechanism of arrythmogenesis caused by As(2)O(3).

Methods And Results: Standard 12-lead ECGs were monitored throughout As(2)O(3) therapy in 20 APL patients. As(2)O (3) (0.15 mg/kg) significantly prolonged the corrected QT interval (QTc: 445+/-7 to 517+/-17 ms, means+/-SE, p<0.01), and also increased the QTc dispersion and transmural dispersion of repolarization. Non-sustained ventricular tachycardias and torsades de pointes occurred in 4 and 1 patients, respectively. The action potentials and isometric contraction were measured in guinea pig papillary muscles during As(2)O (3) perfusion (350 micromol/L). The action potential duration was prolonged (APD(90): 150+/-11 to 195+/-12 ms at 60 min, p<0.01, n=5) and perfusion of As(2)O(3) in a low K(+) solution with a low stimulation rate augmented the prolongation of APD, and provoked early after-depolarizations and triggered activities. The prolonged exposure to As(2)O(3) induced muscle contracture, aftercontractions, triggered activities and electromechanical alternans. Tetrodotoxin or butylated hydroxytoluene partially prevented the As(2)O(3)-induced prolongation of APD.

Conclusions: The prolonged QTc and spatial heterogeneity are responsible for the As(2)O(3)-induced ventricular tachyarrhythmias. In addition to prolongation of the APD, cellular Ca(2+) overload and lipid peroxidation might contribute to the electrophysiological abnormalities caused by As(2)O(3).