Autoimmune congenital heart block: complex and unusual situations

Autoimmune congenital heart block (ACHB) is an immune-mediated cardiac disease included among the manifestations collectively referred to as neonatal lupus. The placental transference of maternal Ro/La autoantibodies may damage the conduction tissues during fetal development leading to blocking of signal conduction at the atrioventricular (AV) node in an otherwise structurally normal heart. Irreversible complete AV block is the main cardiac manifestation of ACHB, but some babies may develop endocardial fibroelastosis, valvular insufficiency, and/or frank cardiomyopathies with significantly reduced cardiac function requiring transplant. The severity of ACHB is illustrated by a global mortality rate of 20% and pacemaker rates of at least 64%, often within the first year of life. This review analyses the main complex and/or unusual clinical situations associated with ACHB, including unusual maternal immunological profiles, infrequent maternal autoimmune diseases, cardiac damage unrelated to AV block, fetal invasive management, late complications after birth, risk of congenital heart block (CHB) in ovodonation and in vitro fertilization techniques, the role of maternal features other than autoimmunity, the influence of the birth order or the risk of CHB in twins and triplets.

The clinical spectrum of autoimmune congenital heart block

Autoimmune congenital heart block (CHB) is an immune-mediated acquired disease that is associated with the placental transference of maternal antibodies specific for Ro and La autoantigens. The disease develops in a fetal heart without anatomical abnormalities that could otherwise explain the block, and which is usually diagnosed in utero, but also at birth or within the neonatal period. Autoantibody-mediated damage of fetal conduction tissues causes inflammation and fibrosis and leads to blockage of signal conduction at the atrioventricular (AV) node. Irreversible complete AV block is the principal cardiac manifestation of CHB, although some babies might develop other severe cardiac complications, such as endocardial fibroelastosis or valvular insufficiency, even in the absence of cardiac block. In this Review, we discuss the epidemiology, classification and management of women whose pregnancies are affected by autoimmune CHB, with a particular focus on the autoantibodies associated with autoimmune CHB and how we should test for these antibodies and diagnose this disease. Without confirmed effective preventive or therapeutic strategies and further research on the aetiopathogenic mechanisms, autoimmune CHB will remain a severe life-threatening disorder.

The challenge of pregnancy for patients with SLE

Pregnancy poses an important challenge for doctors looking after women with systemic lupus erythematosus. Knowledge about safety of medications, the effect of pregnancy on such disease, and vice versa, together with multidisciplinary team care, are basic cornerstones needed to provide the best obstetric and medical care to these women. Pre-conceptional counselling constitutes the ideal scenario where a patient's previous obstetric history, organ damage, disease activity, serological profile and additional medical history can be summarized. Important issues regarding medication adjustment, planned scans and visits, and main risks discussion should also be raised at this stage. Planned pregnancies lead to better outcomes for both mothers and babies. Close surveillance throughout pregnancy and the puerperium, and tailored management approach guarantee the highest rates of successful pregnancies in these women.

Neonatal lupus: bedside to bench and back

Isolated congenital heart block (CHB) detected in utero is strongly associated with autoantibodies reactive with the intracellular soluble ribonucleoproteins 48 kD SSB/La, 52 kD SSA/Ro, and 60 kD SSA/Ro. An erythematous skin rash with a predilection for the scalp and periorbital area, most often apparent in the first few postnatal months, is also highly associated with these maternal antibodies. The permanent cardiac disease and transient cutaneous disease are the most common manifestations of the neonatal lupus syndromes. Fetal and neonatal disease are presumed to be due to the transplacental passage of these IgG autoantibodies from the mother, who may have systemic lupus erythematosus (SLE), Sjögren's syndrome, or be entirely asymptomatic, into the fetal circulation. The fetal heart appears to be uniquely vulnerable, since complete block has never been described in the mothers despite exposure to identical circulating levels of the autoantibodies. Extensive work from several laboratories has resulted in the molecular characterization of the maternal autoantibody responses and the cloning of genes expressing the cognate antigens whose structural features suggest a role in transcriptional regulation. While the precise pathogenetic mechanism of autoantibody mediated tissue injury is not defined it has been demonstrated in adult rabbit and human fetal hearts that sera containing anti-SSA/Ro antibodies induce atrioventricular block and inhibit L-type calcium currents (ICa) in isolated ventricular myocytes. From a clinical perspective the current data suggest that there is not a unique profile of maternal antibody response that predicts the development of neonatal lupus. However, a low risk profile is one in which the titer of anti-SSA/Ro antibodies is low and neither the 60 kD or 52 kD component is recognized on SDS-immunoblot and there are no detectable anti-SSB/La antibodies. Although the fetal disease is called neonatal lupus, this is clearly a misnomer since only about 25% of mothers actually fulfill criteria for the diagnosis of SLE. Furthermore, asymptomatic mothers do not invariably become ill and if an asymptomatic mother does develop SLE it is generally not life-threatening. The recurrence rare of CHB is low, about 15%, but this is nearly three times higher than the risk for CHB in a primigravida with the putative antibodies. CHB carries a significant mortality, 15-30%, and morbidity; two thirds of children require permanent pacing. While prospective clinical trials of fluorinated steroids in women with anti-SSA/Ro and/or anti-SSB/La antibodies is not likely to be initiated given the very low rate of CHB in these mothers, such trials in fetuses with heart block identified in utero are required before definitive recommendations can be made. Numerous anecdotal cases support the use of dexamethasone for treatment of effusions and hydrops and possibly incomplete block. To further efforts both at the bench and bedside, national registries have been established in the U.S. and Canada.