Authors: Gokul Thimmarayan, MD - Marshfield Clinic, Marshfield, WI and
Destiny F Chau, MD - Arkansas Children’s Hospital/University of Arkansas for Medical Sciences, Little Rock, AR.
A 1-day-old neonate with congenital complete heart block is scheduled for a pacemaker placement. Echocardiographic findings reveal a structurally normal heart. What is the MOST COMMON cause of isolated congenital complete heart block?
Correct!
Wrong!
Question of the Week 348
Congenital complete heart block (CCHB) is a rare disorder that is associated with high morbidity and mortality occurring in approximately 1:15-20,000 patients. CCHB describes atrioventricular block diagnosed in utero or during the first 27 days of life. Of the patients with CCHB, fourteen to forty-two percent of cases are associated with congenital heart disease (CHD). This may include congenitally corrected transposition of the great arteries, complete atrioventricular canal defect, and heterotaxy with left atrial isomerism. Maternal autoimmune antibody transfer is the most common cause (ninety-one percent) of CCHB in the remaining percentage of cases. Maternal factors like diabetes, medication exposure (anticonvulsants and retinoic acid), viral infections, and channelopathies are also associated with increased risk of CCHB in the offspring.
Autoimmune CCHB is a manifestation arising from neonatal lupus. Passively transferred maternal autoantibodies to the ribonuclear protein RO (SS-A) and LA (SS-B) cause neonatal lupus. Women with positive antibody titers carry approximately a two percent risk of having a baby with neonatal cardiac lupus after a prior unaffected pregnancy and have a thirteen to eighteen percent risk in subsequent pregnancies. The autoantibodies bind to the cardiac conduction tissue causing inflammation and fibrosis leading to conduction defects. The antibodies are also postulated to affect myocardial cells resulting in cardiomyopathy and endocardial fibroelastosis. Slow heart rate in the fetus with no structural anomaly of the heart and positive maternal antibody is diagnostic of autoimmune CCHB. The vast majority of infants present with third-degree or complete heart block although the presentation may vary from first- to third- degree atrioventricular block. Autoimmune CCHB has an approximate mortality rate of nineteen percent in which a majority occur in utero. Risk of fetal mortality is increased with hydrops, diagnosis of CCHB at earlier than twenty weeks of gestation, ventricular escape rate less than fifty-five beats per minute , impaired left ventricular function, myocardial inflammation, and dilated cardiomyopathy. The presence of dilated cardiomyopathy is a poor prognostic factor. Noncardiac manifestations of neonatal lupus typically self-resolve with clearance of the maternal autoantibodies over the first months of life.
Fetal echocardiography with doppler is the standard diagnostic tool in evaluating CCHB. The assessment of cardiac anatomy, heart rate and mechanical function can deduce abnormalities of electrophysiologic conduction and cardiac structure. With early diagnosis, subsequent intervention is based on the severity of the heart block along with close follow-up and monitoring with serial fetal echocardiograms. Maternal corticosteroids, intravenous immunoglobulin therapy, beta-agonist therapy, and hydroxychloroquine have been used with varying degrees of success. Once CCHB occurs, it is mostly likely irreversible, necessitating pace-maker implantation. In fact, more than two-thirds of these patients require a permanent pacemaker, the majority of which are implanted in the neonatal period.
References:
Steinberg L. Congenital heart block. Card Electrophysiol Clin. 2021; 13(4): 691-702.
Pruetz JD, Miller JC, Loeb GE, Silka MJ, Bar-Cohen Y, Chmait RH. Prenatal diagnosis and management of congenital complete heart block. Birth Defects Res. 2019; 111(8): 380-388.
Friedman DM, Duncanson LJ, Glickstein J, Buyon JP. A review of congenital heart block. Images Paediatr Cardiol 2003; 5(3): 36-48.
Izmirly PM, Chalumeau CN, Pisoni C, et al. Maternal use of hydroxychloroquine is associated with a reduced risk of recurrent Anti-SSA/RO associated cardiac manifestation of neonatal lupus. Circulation. 2012; 126(1): 76-82.
Autoimmune CCHB is a manifestation arising from neonatal lupus. Passively transferred maternal autoantibodies to the ribonuclear protein RO (SS-A) and LA (SS-B) cause neonatal lupus. Women with positive antibody titers carry approximately a two percent risk of having a baby with neonatal cardiac lupus after a prior unaffected pregnancy and have a thirteen to eighteen percent risk in subsequent pregnancies. The autoantibodies bind to the cardiac conduction tissue causing inflammation and fibrosis leading to conduction defects. The antibodies are also postulated to affect myocardial cells resulting in cardiomyopathy and endocardial fibroelastosis. Slow heart rate in the fetus with no structural anomaly of the heart and positive maternal antibody is diagnostic of autoimmune CCHB. The vast majority of infants present with third-degree or complete heart block although the presentation may vary from first- to third- degree atrioventricular block. Autoimmune CCHB has an approximate mortality rate of nineteen percent in which a majority occur in utero. Risk of fetal mortality is increased with hydrops, diagnosis of CCHB at earlier than twenty weeks of gestation, ventricular escape rate less than fifty-five beats per minute , impaired left ventricular function, myocardial inflammation, and dilated cardiomyopathy. The presence of dilated cardiomyopathy is a poor prognostic factor. Noncardiac manifestations of neonatal lupus typically self-resolve with clearance of the maternal autoantibodies over the first months of life.
Fetal echocardiography with doppler is the standard diagnostic tool in evaluating CCHB. The assessment of cardiac anatomy, heart rate and mechanical function can deduce abnormalities of electrophysiologic conduction and cardiac structure. With early diagnosis, subsequent intervention is based on the severity of the heart block along with close follow-up and monitoring with serial fetal echocardiograms. Maternal corticosteroids, intravenous immunoglobulin therapy, beta-agonist therapy, and hydroxychloroquine have been used with varying degrees of success. Once CCHB occurs, it is mostly likely irreversible, necessitating pace-maker implantation. In fact, more than two-thirds of these patients require a permanent pacemaker, the majority of which are implanted in the neonatal period.
References:
Steinberg L. Congenital heart block. Card Electrophysiol Clin. 2021; 13(4): 691-702.
Pruetz JD, Miller JC, Loeb GE, Silka MJ, Bar-Cohen Y, Chmait RH. Prenatal diagnosis and management of congenital complete heart block. Birth Defects Res. 2019; 111(8): 380-388.
Friedman DM, Duncanson LJ, Glickstein J, Buyon JP. A review of congenital heart block. Images Paediatr Cardiol 2003; 5(3): 36-48.
Izmirly PM, Chalumeau CN, Pisoni C, et al. Maternal use of hydroxychloroquine is associated with a reduced risk of recurrent Anti-SSA/RO associated cardiac manifestation of neonatal lupus. Circulation. 2012; 126(1): 76-82.
