Umbilical and Middle Cerebral Artery Doppler Measurements in Fetuses With Congenital Heart Block

Objectives: In fetal congenital complete heart block, the slow fetal heart rate prolongs the diastolic phase of the cardiac cycle, which may affect Doppler measurements that are typically used to quantify placental function. We here describe the umbilical artery (UA) and middle cerebral artery (MCA) Dopplers in a cohort of fetuses with heart block, hypothesizing that values will be increased but nevertheless remain associated with placental function and fetal outcome. Methods: We retrospectively reviewed Doppler measurements of the UA and MCA pulsatility index (PI) and resis-tance index in fetuses with complete heart block. The cerebroplacental ratio (CPR) was calculated as a marker of central redistribution. Measurements were transformed to Z scores and compared between fetuses born with a normal weight (appropriate for gestational age [AGA]) to those with fetal growth restriction (FGR) and correlated with a composite adverse outcome consisting of FGR, fetal death, or preterm birth prior to 34 weeks' gestation. Results: Fifty-four fetuses were included. There were 36 (67%) live births, 8 (22%) stillbirths, and 10 (19%) pregnancy terminations. Of those born alive, 14 (39%) had FGR. The UA PI decreased with gestational age and was higher in FGR compared with AGA fetuses (P < .001). Twenty-three percent of AGA fetuses developed absent end-diastolic flow in the UA. The MCA PI did not change with gestation and did not differ between AGA and FGR fetuses. The CPR was lower in FGR than in AGA fetuses (-2.43 +/- 0.85 vs-1.44 +/- 1.04, P = .006). The UA PI and resistance index were strongly correlated with the composite adverse outcome (P < .001). Conclusions: The UA and MCA PI are significantly elevated in fetuses with complete heart block. The UA Doppler indices and CPR nevertheless still reflect placental function. Longitudinal measurements may be use-ful in monitoring well-being in fetuses with heart block. (J Am Soc Echocardiogr 2021;34:83-8.)