Impact of early detection and steroid treatment on fetal ventricular heart rate and pacemaker implantation in anti-Ro/SSA positive congenital heart block

Introduction We investigated the effects of timing of detection and transplacental fluorinated steroid treatment on ventricular heart rate (HR) and age at pacemaker implantation in fetal third-degree atrioventricular block (AVB). Material and Methods Twenty-five of 31 fetuses diagnosed with Ro/SSA autoantibody-positive AVB II-III at our tertiary fetal cardiology center (2000-2020) and AVB III as final feto-neonatal outcome were reviewed. Results AVB was detected approximately 5 weeks earlier in pregnancy if followed in a surveillance program compared to cases referred from primary care for bradycardia (20.6 [2.3] [mean (SD)] vs. 25.4 [3.2] weeks, p = 0.001). AVB detected before 24 weeks had higher HR than those detected later in gestation (63.3 [6.9] vs. 57.2 [6.9] bpm, p = 0.042), with a larger proportion having HR >60 bpm (80% vs. 33%, p = 0.041). The 17/25 cases that received treatment with fluorinated steroid were diagnosed earlier in gestation, with higher HR at diagnosis (61.7 [7.1] vs. 54.7 [6.3] bpm, p = 0.026), 1-2 weeks after diagnosis/treatment start, and before birth (65.4 [12.4] vs. 54.9 [5.7] bpm, p = 0.030) than untreated cases. Overall, 11 cases were commenced on betamimetics: three at diagnosis and eight at or after the examination made 1-2 weeks after diagnosis/treatment start, without any HR improvement. Two of 24 surviving babies were born preterm, and 4/24 received a neonatal pacemaker. Age at pacemaker implantation correlated significantly with HR before birth (Spearman R 0.57, p = 0.004), and fetuses with HR >60 bpm had a higher rate of pacemaker-free survival at three (90% vs. 40%, p = 0.018) and 12 months of age (80% vs. 13%, p = 0.002). The same trend was observed in pacemaker-free survival at 3 months of age in fluorinated steroid-treated compared to untreated cases (71% vs. 38%, ns). Conclusions Our data confirm that AVB III detected earlier in gestation have a higher HR, and suggest that this higher HR can be successfully maintained to the end of gestation in cases treated with fluorinated steroids. Fetuses with HR >60 bpm before birth had a lower rate of pacemaker implantation at 3 and 12 months of age.