What is Congenital Heart Block?
According to the National Organization for Rare Disease, Congenital Heart Block, or CHB for short, is the interference of the transfer of electric nerve impulses that regulate the pumping of the heart muscle.
As long as electrical impulses are transmitted normally between the heart’s chambers – the atria and the ventricles – the heart contracts normally, allowing for blood to be pumped throughout the body. If the transmission of the signal is impeded, the blocked electrical transmission is known as heart block, or atrioventricular (AV) block.
Though heart block can happen to anyone of any age, it is called congenital heart block if it occurs in a fetus or newborn up to 28 days old.
Why Does CHB Occur in Children Born to Women with Autoimmune Disease?
Autoimmune-associated CHB has been found in a variety of maternal autoimmune disorders, including Sjogren’s syndrome, systemic lupus erythematosus, rheumatoid arthritis, antiphospholipid syndrome (APS), mixed connective tissue disorders, and undifferentiated connective tissue disease.
It is believed that CHB may result when maternal antibodies cross the placenta, enter the fetus, and attack the fetal cardiac conduction system. The antibodies that were originally produced by the mother’s body to fight infections mistakenly recognize parts of the fetal heart’s conduction system as foreign; for this reason, the immune system attacks and damages the tissues, resulting in inflammation and scarring, which in turn leads to faulty conduction.
What Is the Risk of Congenital Heart Block if I Have an Autoimmune Disease?
A 2017 study conducted by Chinese medical professionals Kai-Yu Zhou and Yi-Min Hua of the West China Second University Hospital, Department of Pediatric Cardiology, revealed that more than half of CHB cases (between 60 and 90%) are associated with maternal autoimmune disease.
Among the general population, CHB occurs in 1 out of every 20,000 live births – an incidence of only 0.00005%. The study found that autoimmune-associated CHB, however, occurs at much more frequent rates, affecting between 2–5% pregnancies with positive anti-Ro/SSA and La/SSB antibodies. The study also found that when a woman had a child with CHB, the recurrence rate of CHB was 12–25% for a subsequent pregnancy.
Mortality Rate & Treatment for Congenital Heart Block
The perinatal mortality rate of a newborn with CHB is up to 30%, and even higher in the presence of endocardial fibroelastosis (EFE) or dilated cardiomyopathy (DCM), which are other potential complications associated with CHB.
If CHB is detected in utero by a fetal electrocardiography (ECG) and echocardiography, your OB/GYN may prescribe an adrenocorticosteroid such as dexamethasone, which works to decrease inflammation and the number of circulating maternal antibodies in the fetus.
Once born, other studies have shown that between that 64 and 70% of CHB survivors require surgery to permanently implant a pacemaker, a medical device which stimulates the heart to contract so that it can pump blood.
How to Prevent Congenital Heart Block
A 2016 report by the American College of Rheumatology states that there are no official guidelines about the prevention, screening, and treatment of CHB due to maternal Ro antibodies.
However, in the same report, it was stated that in a survey of 330 women with autoimmune conditions, 67% were told by their rheumatologists to use hydroxychloroquine (also known as Plaquenil) to prevent CHB. In addition, 62% were told to start the drug prior to pregnancy, in order to prevent the condition from developing.
Another study published in The Journal of the American College of Cardiology stated that hydroxychloroquine reduces the recurrence of CHB below the historical rate by more than 50%, further demonstrating the promise of this drug in the prevention of CHB.