[Sinus bradyarrhythmia during administration of all-trans retinoic acid in a patient with acute promyelocytic leukemia].

A case of acute promyelocytic leukemia (APL) complicated by sinus bradyarrhythmia during the course of all-trans retinoic acid (ATRA) administration is reported. A 3-year-old boy was admitted for evaluation of petechiae and APL was diagnosed. He was initially treated with 45 mg/m2 of ATRA without success, and a complete remission was achieved when the dose was increased to 135 mg/m2. Sinus bradyarrhythmia was first recognized 3 days after the induction therapy with ATRA. It did not disappear even when the patient stopped taking the medication. However, the arrhythmia tended to be augmented whenever he received ATRA again. Close observation of his cardiac condition was mandatory to continue ATRA as an integral part of the therapy for APL, combined with multidrug chemotherapy including anthracyclines, which themselves are potentially toxic to myocardium. In conclusion, the present case revealed the possibility that ATRA therapy induces sinus node arrhythmia, or that it can potentiate preexisting node dysfunctions.