A 9-year-old boy showed orofacial dyskinesia and psychic symptoms shortly after open heart surgery with deep hypothemia and cardiopulmonary bypass for congenital cyanotic heart disease. The choreothetosis progressed to be generalized and accompanied by mental deterioration. This involuntary movement partially responded only to repetitive administration of sedatives. After 3 month the patient expired with sudden development of ventricular tachycardia and cardiogenic shock.