PrenatDiagn 2007; 27 : 879–881.
DOI: 10.1002/pd.1784
Sustained fetal bradycardia with 1:1 atrioventricular conduction
and long QT syndrome
Authors
Juan C Collazos, MD, Ruben J Acherman, MD, Ian H Law, MD, Paul
Wilkes, MD, Humberto Restrepo, MD, William N Evans, MD
Source
ChildrenŐs Heart Center Nevada, 3006 S Maryland Pkwy, Ste 690,
Las Vegas, NV 89109, USA.
E-mail: IAcherman@aol.com.
Abstract
Fetal echocardiography is a useful tool in the prenatal diagnosis
of congenital heart disease and fetal arrhythmias. The fetal cardiac rhythm is
normally regular with 1:1 atrioventricular (AV) conduction at a rate of
100–180 bpm. Fetal bradycardia is defined as a heart rate of < 100
bpm. The causes of fetal bradycardia are diverse and the prognosis varies
depending on the heart rate, type of bradycardia, etiology, and the presence of
the structural cardiac abnormalities (Lin et al., 2004). Sustained fetal
bradycardia is rare, occurring in < 3% of term infants and in 5% of postterm
pregnancies. Fetal bradycardia and other fetal arrhythmias may be associated
with congenital long QT syndrome (LQTS)(Maeno et al.,
2003; Milanesi et al., 2006). LQTS is a rare
disorder; it may be congenital oracquired. The congenital form is caused by the
mutations that encode the cardiac sodium and potassium channels (Chiang, 2004).
More than 300 mutations have been documented in seven different genes located
on six chromosomal loci (Chiang, 2004). The acquired form is
caused by certain drugs, electrolyte disturbances, and other medical conditions
(Chiang, 2004). Patients with LQTS are at risk for life-threatening
ventriculararrhythmias, which may lead to syncope and sudden death. The
incidence of sudden cardiac death has been estimated to be 0.5–1.5% per
year for high-risk, young patients (corrected QTc>
500 ms, syncope on beta-blocker therapy) and 0.01–0.1% per year for
low-risk, (QTc< 500ms) young patients with LQTS
(Hobbset al., 2006). Early diagnosis is important in order to start treatment
in infants and to identify other family members at risk. We report the prenatal
presentation, clinical course, and management of a patient with LQTS,
persistent fetal bradycardia, and 1:1 AV conduction with no other associated
arrhythmias.