Fetal Atrial Tachycardia Diagnosed by Magnetocardiography and Direct Fetal Electrocardiography

At 26 weeks of gestation, fetal tachyarrhythmias (about 250 bpm) and ascites were detected by ultrasonography, and oral treatment with propranolol (30 mg/day) was commenced. Within 10 h, the fetal heart rate changed to approximately 85 bpm. The averaged fetal magnetocardiogram triggered by R peaks showed P wave and QRS complexes and an extra P wave. In addition, many extra nonconducted P-waves were detected in a fetal direct electrocardiogram. At 27 weeks of gestation, fetal tachycardia occurred again, and arrhythmia was diagnosed as the result of a blocked premature atrial contraction (PAC) with intermittent atrial tachycardia by fetal electrocardiogram. Administration of transplacental propranolol (90 mg/day) resolved the fetal tachyarrhythmias and ascites. Further studies are required to evaluate the efficacy and adverse effects of propranolol for fetal atrial tachycardia.