Fetal bradyarrhythmias: classification, monitoring and outcomes of 40 cases at a single center.

Objectives: To assess congenital fetal bradyarrhythmias with regard to etiological causes, features, risk factors, and prognosis.

Methods: This retrospective study involved fetuses with fetal bradyarrhythmias. All fetuses were evaluated by ultrasonography. Parental ECGs and family histories were obtained, and maternal autoantibodies were measured. Gestational age at diagnosis, fetal atrial and ventricular rates at presentation, type of bradyarrhythmias, the presence or absence of a congenital heart defect (CHD), fetal hydrops, fetal myocardial dysfunction, extra-cardiac abnormalities, maternal autoimmune diseases, maternal autoantibodies as well as prenatal treatment, and neonatal outcome were collected.

Results: Of the 40 fetuses included in the study, 11 had maternal rheumatologic disease, 16 had complex cardiac anomalies such as left and right isomerism. Fetuses with CHD significantly differed from those without CHD with increased rates of extra-cardiac anomalies, hydrops, fetal deaths and shorter survival after 28 days (p<0.05). Survival was significantly better in fetuses with maternal rheumatic disease as compared with those with no maternal rheumatic disease (p<0.05). Maternal anti-arrhythmic therapy was administered in 11 fetuses. maternal treatment resulted in no significant difference in the course of arrhythmia or hydrops in fetuses with or without maternal rheumatic disease (p<0.05). In regression analysis, the absence of fetal hydrops was the only independent factor associated with survival (p=0.04).

Conclusions: The course of bradyarrhythmias, along with survival, seems to be more favorable in fetuses with maternal rheumatic disease than in those with CHD, especially left and right isomerism. Hydrops was the sole independent factor associated with poor survival.