Transient Fetal Atrioventricular Block: A Series of Four Cases
and Approach to Management
Sandra D. Kikano, MD and Stacy A. S. Killen, MD, MSCI
Thomas P. Graham Division of Pediatric Cardiology Monroe Carell Jr
Children’s Hospital at Vanderbilt University, Nashville, TN, USA.
Funding: none
Disclosures: none
Correspondence:
Stacy A. S. Killen, MD, MSCI
2220 Children’s Way, Suite 5230
Nashville, TN 37232-9119
Phone (615) 322-7447
Fax (615) 322-2210
E-mail: stacy.statemann@vumc.org
Abstract :
Fetal atrioventricular block (AVB) is a failure of conduction from atria
to ventricles. Immune- and non-immune-mediated forms occur, especially
in association with congenital heart disease. Second-degree (2°) AVB may
be reversible with dexamethasone and IVIG in immune-mediated disease.
However, once third-degree AVB develops, it is deemed irreversible with
need for a pacemaker and risk for cardiomyopathy. Rarely, 2° AVB is a
transient, benign phenomenon in the immature conduction system. Few case
series of transient AVB have been reported, but a management approach
has not been defined. We report four patients with self-resolving,
non-immune fetal AVB and outline a management strategy.
Key Words: Fetal atrioventricular block, Fetal heart block, Fetal
second-degree atrioventricular block, Long QT syndrome
Introduction :
Fetal atrioventricular block (AVB) is estimated to occur in
~ 1: 20,000 live
births[1]. It occurs
in immune- and non-immune-mediated
forms[1-6].
Immune-mediated block develops from transplacental passage of maternal
anti-Ro/SSA autoantibodies that, beginning in the second trimester,
damage the fetal AV
node[1]. Complete
(third-degree) immune-mediated AVB is considered irreversible and has
significant associated mortality (15-30%) and morbidity, with about
two-thirds of infants requiring permanent pacing
postnatally[2-4].
Non-immune AVB most often occurs in the setting of complex structural
heart disease, such as left atrial isomerism (LAI) and
congenitally-corrected transposition of the great arteries (ccTGA), in
which discontinuity of the AV node and ventricular tissue causes
complete heart block[5,
6].
There are a few case reports of non-immune-mediated fetal AVB without
structural heart disease, with variable outcomes. Some reports describe
hydrops or permanent pacing in most
patients[7]. Other
reports describe transient AVB without significant long-term
complications[8-11].
We describe four patients, evaluated in the Vanderbilt University
Medical Center fetal cardiology clinic from 2016-2020, with benign,
self-resolving, non-immune-mediated, second-degree (2°) fetal AVB and
outline a management approach.