New Rhythm on the “Block”: The 1st Reported Case of Third-Degree Heart Block Reversal in the Setting of Neonatal Lupus

Summary: Introduction: Conduction defects are among the most classic and common signs of neonatal lupus erythematosus (NLE). These may range from first to third degree heart block, and remain one of the major causes of mortality in NLE. It has been postulated that once third-degree heart block is present, it is considered to be an irreversible condition (1). Here we present a case of third-degree heart block in a fetus that episodically returned to normal sinus rhythm after treatment with IVIG and systemic steroids. Case presentation: A 29-year-old primigravid female with a positive Ro-52 antibody, a positive rheumatoid factor, and a positive antinuclear antibody with 1:160 titer in a speckled pattern presented for her routine 20 week fetal scan. Fetal heart rate was found to be in the 90s with the lowest values dropping into the 50s. Patient was urgently admitted to the hospital for IVIG as well as dexamethasone per Surveillance and Treatment To Prevent AV Block Likely To Occur Quickly (STOP-BLOQ) protocol. The 3rd degree heart block unfortunately did not resolve. Patient was discharged on 8 mg PO dexamethasone with home heart rate monitoring and close pediatric cardiology follow up. At about 23 weeks’ gestation, patient was notified that her fetus’ heart rate had increased to a normal rate, and was urgently evaluated in clinic. Further evaluation revealed that the fetus had returned to normal sinus rhythm, which had not been reported in literature prior to this. Patient was again admitted for another round of IVIG and dexamethasone. In the subsequent weeks, the fetus was closely monitored and found to have episodic bouts of normal sinus rhythm in the setting of varying degrees of heart block. A cesarean section was scheduled for 39 weeks gestation. However, at 35 weeks and four days of gestation, patient went into labor spontaneously. She presented to the hospital and was given oxytocin to help further the labor process. However, due to the difficulty in monitoring the fetus’ heart rate, a cesarean section was scheduled. Patient underwent a successful cesarean section and baby was born in normal sinus rhythm. Baby was taken urgently to the neonatal intensive care unit for heart rate monitoring. Within a few hours, baby went back into second-degree heart block and remained there. There was no immediate need for transcutaneous pacing or pacemaker implantation, and further discussions remain ongoing. Baby had no other manifestations of neonatal lupus, such as neurological abnormalities, cutaneous lesions, or blood dyscrasias. At 2 weeks of age, she is feeding and growing appropriately, and does not appear to be limited by her relatively low heart rate. Discussion: The incidence of NLE is about 2% in offspring of mothers with autoantibodies of Sjogren syndrome autoantigen type A (Ro/SSA) or B (La/SSB) with an 18% to 20% recurrence rate in the following pregnancies. Fetal complete (3°) atrioventricular block (AVB), identified in the 2nd trimester in an otherwise normally developing heart, is almost universally associated with maternal anti-Ro autoantibodies, which transcytose the placenta via the trophoblastic IgG receptor, FcγRn. Conduction defects remain the most common cause of death in NLE, with a mortality of over 20% despite pacemaker implantation (PMI) and much higher without PMI. Needless to say, it remains a significant problem with a high degree of morbidity and mortality. Thus far, the entire focus of treatment of NLE-induced third-degree heart block has been on prevention, as it was thought to be an irreversible condition that categorically required pacing. This case represents a paradigm shift in our understanding of this condition. Unfortunately, there are no official guidelines for treatment, and therapy is largely guided by case reports and expert opinion. One such treatment regimen is IVIG and dexamethasone, which was administered during the STOP-BLOQ study (study remains ongoing). While the role of dexamethasone in preventing progression of congenital heart block has been mixed (2), IVIG appears to have had some positive benefit (3). Further clinical trials are needed in order to establish the efficacy of these treatments, particularly in light of this recent development. Conclusion: Third-degree congenital heart block, once thought to be an irreversible condition that would categorically require pacing, can be reversed. This represents a paradigm shift in our understanding of third-degree congenital heart block induced by NLE.