Cerebral blood flow characteristics and biometry in fetuses undergoing prenatal intervention for aortic stenosis with evolving hypoplastic left heart syndrome

Abstract

Children with hypoplastic left heart syndrome (HLHS) are at risk for neurodevelopmental dysfunction; prenatal factors may play a role in this predilection. Cerebral blood flow profiles are abnormal in fetuses with HLHS, raising the possibility that cerebral hemodynamics in utero may be related to neurodevelopmental abnormalities. Prenatal aortic valvuloplasty for fetal aortic stenosis with evolving HLHS is technically feasible and improves left heart hemodynamics. This study aimed to assess the effects of prenatal intervention on cerebral blood flow profiles and head circumference in fetuses with evolving HLHS. Seventy fetuses underwent prenatal aortic valvuloplasty for evolving HLHS (median 23 weeks gestation). Among 46 fetuses that had successful valvuloplasty and available data, middle cerebral artery (MCA) pulsatility (PI) and resistive (RI) indices were abnormal (Z-scores -1.7+/-1.1 and -2.2+/-1.4, p<0.001). Early post-valvuloplasty (n=33) and at late gestation follow-up (n=28), MCA PI and RI Z-scores remained low with no difference from pre- or early postintervention. Fetal head circumference was normal, as were umbilical artery PI and RI Z-scores. Cerebral blood flow characteristics are abnormal in mid-gestation fetuses with evolving HLHS, suggesting low cerebral vascular impedance. The mechanisms and significance of these abnormalities are unknown. Prenatal aortic valvuloplasty did not have a major impact on these indices. (E-mail: doff.mcelhinney@cardio.chboston.org).

Figure 1

Ultrasound images in three different patients demonstrating (a) the identification of the orbits (O), circle of Willis and middle cerebral artery (MCA) (arrow) using color Doppler, (b) alignment of the pulsed wave Doppler sample volume in the proximal MCA at a low angle of insonation as it runs laterally along the petrous bone and (c) the pulsed wave Doppler spectrum and measured velocities.

Figure 2

Scatter plots depicting (a) middle cerebral artery (MCA) pulsatility index (PI), (b) MCA resistive index (RI), (c) umbilical artery (UA) PI and (d) UA RI for the 46 fetuses with preintervention MCA and UA Doppler data available. Mean and 95% confidence intervals for normal fetuses, as reported previously (Arduini and Rizzo, 1990 and Kurmanavicius et al., 1997), are represented by the broad and solid lines, respectively. A 95% confidence interval was not calculated for MCA RI in the normative data set (Kurmanavicius et al. 1997).

Figure 3

Changes in (a) middle cerebral artery (MCA) pulsatility index (PI), (b) MCA resistive index (RI), (c) umbilical artery (UA) PI and (d) UA RI Z-scores from pre- to early postintervention among fetuses that underwent technically successful aortic valvuloplasty. Fetuses with significant aortic regurgitation (AR) after intervention are depicted with the dashed lines and fetuses without AR are represented by solid lines.

Figure 4

Change in middle cerebral artery (MCA) resistive index (RI) between pre- and early postintervention studies among fetuses that underwent successful aortic valvuloplasty and did or did not develop significant AR (p = 0.05).

Figure 5

This scatter plot depicts the relationship between middle cerebral artery (MCA) pulsatility index (PI) Z-score and head circumference Z-score prior to intervention, and also reflects the lack of association between head circumference and other MCA flow indices. The relationship is defined by the following regression equation: Head circumference Z-score = (−0.189 × MCA PI Z-score) − 0.189 (r = −0.17, p = 0.27). The solid line at Z = 0 indicates the mean for the normal population, and the dashed lines at +2 and −2 indicate the limits of the normal range.