Cerebral blood flow autoregulation and congenital heart disease: possible causes of abnormal prenatal neurologic development

Objective. To determine whether the major congenital heart diseases (CHDs) can modify the cerebrovascular flow dynamics and the biometrical parameters in fetuses at third trimester of pregnancy. Methods. We studied 60 fetuses with CHD. Data included prenatal versus postnatal cardiac diagnosis, cerebral and umbilical artery doppler, fetal biometrical parameters, fetal weight, and gestational age. The pulsatility index (PI) was used to determine blood flow velocities in the umbilical artery (UA) and middle cerebral artery (MCA), while the cerebro/placental ratio (CPR) was assessed as a measure of cerebral autoregulation. Fetuses with CHD were compared to normal controls and then analyzed after being divided into groups based on specific defects. Results. Compared with control fetuses, those with CHD showed a decrease of resistance blood flow in the middle cerebral artery (1.76 vs 1.92 PI) especially considering the CPR (1.66 vs 2.03 PI) (p < 0.01). Furthermore, fetuses with CHD also had smaller head circumferences (30.6 cm vs 31.5 cm p < 0.01) and head/abdominal (HC/AC) ratio (1 vs 1.05 p < 0.01). When stratified for single cardiac diseases, fetuses with hypoplasic left heart syndrome showed a lower CPR and HC/AC ratio. Conclusions. Cerebrovascular resistance is significantly lower in fetuses with CHD, especially in cases of left side obstruction. The cerebro/placental hemodynamic changes are similar to that described in fetuses with placental insufficiency and may contribute to their abnormal neurologic development.