It is well established that congenital heart disease (CHD) in general, and lesions resulting in a univentricular circulation in particular, are associated with increased risk for neurodevelopmental impairments.
Although still an emerging field in prenatal diagnosis, accumulating data shows that the CHD itself is responsible for brain abnormalities such as periventricular leukomalacia (PVL), migration abnormalities or biometric problems.
The pathogenetic mechanism for these abnormalities may involve, at least in part, hemodynamic changes, and fetal genetic conditions.
Neurosonography is indicated in fetuses with CHD, in order to rule out associated CNS malformations (such as sulcation and gyration abnormalities), and/or acquired lesions.
An association between congenital heart disease (CHD) and neurodevelopmental delay (NDD) has long been recognized, but it is only now beginning to be studied in detail. Insight into the anatomic features of brain disturbance in neonates and children affected with CHD has been provided by conventional neuropathological postmortem studies and by magnetic resonance imaging (MRI) analyses in vivo. Neuropathological studies indicate that the brain disturbance in CHD before surgery is dominated by cerebral white matter injury, generally comparable with periventricular leukomalacia (PVL) as described in preterm infants.1–3 However, there is significant evidence to support the concept that the presence of the CHD itself—and of some specific CHDs in particular—is responsible for these lesions, which affect primarily but not only the white matter. In fact, significant neuronal migration impairment has been repeatedly demonstrated in neonates with complex CHDs.4–7 In addition, though to a minor extent, the incidence of central nervous system malformations and acquired clastic lesions is higher in neonates with complex CHDs than in normal controls.1,8
We decided to include a new chapter on this controversial topic in the current edition of this book because evidence has recently been published showing that the onset of these lesions is prenatal, and that both the acquired clastic lesions and the cortical gyration delay can be recognized with MRI and transvaginal neurosonography as early as the second trimester of pregnancy.9–14
PATHOPHYSIOLOGY OF BRAIN DAMAGE AND CONGENITAL HEART DISEASE HEMODYNAMICS
Once the association between CHD and brain lesions responsible for NDD was established, the next step has been to discover the pathophysiology of the lesions themselves. In this regard, it is easy to think that the lower oxygen supply to the brain, mediated by the hemodynamic changes brought about by the CHDs themselves, was indeed the pathogenetic mechanism. However, this may be true for some types of CHDs, such as hypoplastic left heart syndrome (HLHS), but not for others. Hereafter, the hemodynamics of the normal fetal circulation is compared with that of some typical CHDs associated with NDD and brain lesions, such as HLHS or transposition of the great arteries (TGA).
In the normal fetus (Figure 23–1), the highly oxygenated blood ...