PrenatDiagn 2007; 27 : 879–881. DOI: 10.1002/pd.1784
Sustained fetal bradycardia with 1:1 atrioventricular conduction and long QT syndrome
Juan C Collazos, MD, Ruben J Acherman, MD, Ian H Law, MD, Paul Wilkes, MD, Humberto Restrepo, MD, William N Evans, MD
ChildrenŐs Heart Center Nevada, 3006 S Maryland Pkwy, Ste 690, Las Vegas, NV 89109, USA.
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.