Fetal arrhythmias; intrauterine diagnosis and treatment

Fetal echocardiographic examination was performed on 945 pregnant women (normal pregnancy: 291, high risk pregnancy: 654) since 1980. Of these, 39 fetuses (4.1%) were diagnosed as having cardiac arrhythmia. Fifteen fetuses had bradycardia, 7 tachycardia and 17 had an ectopic beat. These had been followed from 1 day to 8 years (mean 1 year and 6 months) soon after birth. Of the 15 cases with bradycardia (complete AV block; 8, 2:1 AV block; 3 and sinus bradycardia; 4), four resulted in an intrauterine fetal death, one was terminated and 5 died soon after birth. The remaining 5 cases are alive and 3 of these 5 have received an implanted pacemaker. Of these 15 cases with bradycardia 7 were associated with congenital heart disease, 6 of which died. Seven cases had tachycardia (supraventricular tachycardia: 3 and atrial flutter with 2:1 AV block: 3). Transplacental antiarrhythmic drug (digoxin and/or verapamil) administration was instituted in 5 cases and a conversion of the arrhythmia was achieved in 4. Paroxysmal tachycardia still remained after delivery in the other 3 cases. Two cases with supraventricular tachycardia (one of them with WPW syndrome type B) were resolved. One case has had persistent chaotic atrial rhythm for 7 years after birth. Of the 17 with an ectopic beat, 11 cases were diagnosed to have a supraventricular ectopic beat and 6 cases with a ventricular ectopic beat. A remaining arrhythmia was observed in 10 cases after delivery but all of these were resolved within 3 months after birth. Fetal tachycardia had relatively favorable prognosis because usually the intrauterine treatment was effective. However, fetal bradycardia had poor prognosis and further investigations to establish more effective treatments are essential.