Atrioventricular block detected in fetal life: associated anomalies and potential prognostic markers.

Objectives: To assess the spectrum of anomalies associated with fetal heart block and to identify possible prognostic markers.

Methods: Retrospective review of all cases of second- or third-degree heart block identified in two tertiary referral centers in Germany (Bonn and Lübeck) and one in the USA (Baltimore).

Results: Sixty fetuses with heart block were identified in the study period. Thirty-two had complex cardiac malformations, 31 of them associated with left isomerism. The outcomes of these fetuses were 22 terminations of pregnancy (TOP), three intrauterine fetal deaths (IUFD), three neonatal deaths (NND), two childhood deaths (CD) and there were two survivors. In 20 cases without complex cardiac malformations maternal antinuclear-antibodies were detected. Their outcomes were 2 TOP, 1 IUFD, 1 NND and 16 survived. The remaining eight cases had neither complex cardiac malformations nor associated maternal antibodies. Their outcomes were 1 TOP, 2 IUFD, 2 NND and 3 survived. After exclusion of terminated cases, hydrops as well as the presence of cardiac defects was significantly associated with non-survival (P < 0.01). The cardiothoracic circumference ratio was significantly higher in hydropic fetuses and significantly negatively correlated with survival in immune-mediated cases (P < 0.01). Atrial and ventricular frequencies and their evolution did not accurately predict fetal or neonatal outcome. Sympathomimetic treatment in seven cases was not associated with favorable fetal outcome in cases of hydrops or cardiac malformations.

Conclusions: The most important marker predicting adverse outcome in cases of heart block is fetal hydrops, followed by the association with complex cardiac malformations. Cases without cardiac malformations have a significantly better prognosis, especially in the absence of severe cardiomegaly.