ABSTRACT
A 48-year-old man was readmitted to the hospital because of severe intraventricular conduction defects (QRS duration was 0.30 sec). The patient had been given pilsicainide hydrochloride (150 mg/day) prior to the hospitalization. The blood tests revealed that the concentration of pilsicainide was 3.30 μg/ml, which was several times higher than the average value in patients given in a dosage of 150 mg per day. Five months before the second admission, impaired left ventricular (LV) myocardial function and paroxymal atrial fibrillation were observed in the patient. His illness was diagnosed as myotonic dystrophy as the patient presented with skeletal muscle atrophy, premature frontal baldness, hatchet face, cataract, and testicular atrophy. The trial of remedication with pilsicainide in the same dosage for seven days did not produce the toxic effects as seen previously. Both load-dependent LV dysfunction in myotonic muscular dystrophy and moderately impaired renal function in the patient probably underlay the state of intoxication.