Acute Complete Atrioventricular Block in the Fetus Can be Reverted by High Dose Dexamethasone.

A 34 y mother with anti-Ro, anti-La antibodies was referred to our program for fetal atrioventricular (AV) conduction assessment. At her 3^rd pregnancy, one of her bi-chorionic twins was incidentally found to be in complete AV block (CAVB) at 21^st gestational week and underwent permanent pacemaker implantation immediately after birth. At her present (4^th) pregnancy, the mother was referred at 15 weeks of gestation. She was followed-up weekly according to our laboratory protocol. On the 22^nd week, 6 days after the previous study had showed normal AV conduction (NAVC), the fetus was in CAVB, with a ventricular HR of 60 BPM. The left ventricle was dilated with reduced function and hydrops fetalis. Assuming the fetus was at the acute phase of lupus carditis, we initiated high dose oral dexamethasone therapy giving the mother 6 mg twice within 24 hours, followed by 6 mg daily for the following days. We continued with dexamethasone 5mg QD and after 2 more days 4mg QD until delivery. After 24 hours, the fetus was still in CAVB. However, at 48 hours, we recorded episodes of second-degree AVB with 2:1 conduction (ventricular rate 70 bpm). AV conduction gradually improved with Mobitz 2 AVB and after 8 days 1^st degree AVB (160 bpm). A 2.5 kg male was delivered (C-section) with HR of 130-160 BPM with a prolonged PR interval of 180ms on ECG. He continued to be treated with steroids for 4 more weeks. One year after birth, the child showed normal growth and development. His ECG exhibited NSR of 120 bpm with NAVC.

This is the first ever report of CAVB reversal. It suggests that in such a high-risk group of siblings to CAVB fetuses, the delay in which a normal conduction system is completely disrupted to CAVB might be even shorter than the 6 days quoted in the literature and that early high dose dexamethasone prevents deterioration. In this small subgroup, a twice-weekly follow-up might be advisable.