Postnatal outcome of fetal bradycardia without significant cardiac abnormalities.
BACKGROUND
A heart rate <100 beats/min may be present in 5% of fetuses with arrhythmia. In this study, we sought to define the feasibility of in utero diagnosis of the underlying mechanisms and the postnatal outcome.


METHODS
The types of fetal bradycardia were defined by fetal echocardiogram. Fetuses with transient sinus bradycardia were excluded.


RESULTS
From 1995-2000, a total of 18 fetuses were found to have bradycardia. Postnatal 12-lead electrocardiograms made at least 3 times during follow-up confirmed the cardiac rhythm in all except those terminated during pregnancy. Sick sinus bradycardia was noted in 4 patients (22 %), of whom 1 had a positive family history and 2 received permanent pacemakers at age 4 and 5 years. Frequent nonconducted atrial premature beats or nonconducted atrial bigeminy or trigeminy were noted in 5 (28%). All of them revealed normal sinus rhythm after birth. Atrioventricular (AV) block was noted in 6 (33%), of whom 3 were terminated due to severe heart failure, and another 2 fetuses received permanent pacemaker implantation soon after birth. Only 1 fetus whose mother showed normal levels of C3 and C4 recovered at late gestation. Most importantly, 3 patients (17%) developed intermittent bradycardia (AV block) and ventricular tachycardia during the fetal stage. They were found to have long QT syndrome. Two of them died during early infancy. One received in utero propranolol and postnatal propranolol and nicorandil with satisfactory control.


CONCLUSIONS
The mechanisms responsible for fetal bradycardia were diverse and could be characterized by fetal echocardiography. The prognosis was poor in those with long QT syndrome manifested as intermittent fetal bradycardia and tachycardia with AV dissociation.
Department of Pediatrics, National Taiwan University Hospital, Taipei, Taiwan.
Ming-Tai
MT
Lin
Fon-Jou
FJ
Hsieh
Ming-Kwang
MK
Shyu
Chien-Nan
CN
Lee
Jou-Kou
JK
Wang
Mei-Hwan
MH
Wu
D000328:Adult; D018880:Atrial Premature Complexes / Q000150:complications / Q000000981:diagnostic imaging; D001919:Bradycardia / Q000000981:diagnostic imaging* / Q000209:etiology; D015331:Cohort Studies; D004452:Echocardiography; D005260:Female; D005315:Fetal Diseases / Q000000981:diagnostic imaging*; D006327:Heart Block / Q000150:complications / Q000000981:diagnostic imaging; D006801:Humans; D008133:Long QT Syndrome / Q000150:complications / Q000000981:diagnostic imaging / Q000401:mortality; D011247:Pregnancy; D011296:Prenatal Diagnosis; D011379:Prognosis; D012189:Retrospective Studies; D012804:Sick Sinus Syndrome / Q000150:complications / Q000000981:diagnostic imaging / Q000628:therapy; D013610:Tachycardia / Q000000981:diagnostic imaging / Q000209:etiology