Fetal autoimmune-mediated complete heart block: favorable mortality outcome in 20 cases from a single center

Background:
Fetuses exposed to maternal autoimmune diseases, such as Lupus or Sjogren's syndrome, are at risk of developing autoimmune-mediated heart block. Maternal anti-Ro/SSA or anti-La/SSB antibodies produced cross the human placenta and cause inflammation, cell death, and scaring of the fetal cardiac conduction system. The risk of mortality to the exposed fetus has been reported to be at least 18%. We were interested in detailing the outcomes and associated prenatal echocardiographic features in fetuses with autoimmune-mediated heart block at our institution compared to those in published studies.

Methods:
We performed a retrospective review of fetal echocardiograms with diagnosis of fetal autoimmune-mediated complete heart block from March 2004 to January 2020 combined with review of associated prenatal and postnatal records. Study population was limited to fetuses exposed to maternal anti-Ro/SSA or anti-La/SSB antibodies and diagnosed with third-degree heart block.

Results:
Twenty fetuses were diagnosed with autoimmune-mediated complete heart block from 19 mothers. Compared to a recent study with 12% in utero demise, our cohort only appreciated 5% in utero demise and 5% postnatal death, for a 10% cumulative mortality. We evaluated for associations among the echocardiographic features presented in the Table and death, survival to 1 year of age, in utero survival, and need for pacemaker implantation in the first week of life. Only the presence of hydrops had a statistically significant correlation with death and survival to 1 year of age in our cohort (p=0.009). The patient who died in utero had the highest middle cerebral artery (MCA) and umbilical artery (UA) pulsatility indices and the lowest CPR on the last echocardiogram prior to death. Demographic factors, including maternal autoimmune diagnosis, maternal antibody profile, fetal gender, and premature birth did not correlate with outcomes in our cohort. Maternal treatment with terbutaline had a statistically significant correlation with need for pacemaker implantation in the first week of life (p=0.015).

Conclusion:
Mortality for fetuses with autoimmune-mediated complete heart block appears to be improving in the current era. Echocardiographic predictors of in utero and postnatal survival remain lacking.