Many other cardiac malformations that do not involve the connections of the heart can be recognized prenatally. They include:
1. Valve stenosis.
2. Ventricular septal defect.
3. Valvar dysplasia or displacement.
4. Cardiac tumour.
In aortic or pulmonary valve stenosis, the respective ventricular chamber and the valve itself may appear thickened. The affected artery is often disproportionately small in relation to the other artery. The Doppler sample volume placed in the stenosed artery sometimes shows a velocity of blood flow above the normal range, but this is not such a consistent feature as that produced by a valve stenosis postnatally. In critical aortic stenosis, the left ventricle is characteristically globular and echogenic (Figure 4.12) In the moving image, the poor contraction can be readily appreciated. Ventricular septal defects, when recognized prenatally, are frequently large and associated with chromosomal anomalies. A large mid-muscular defect is seen in Figure 4.13. Tricuspid valve dysplasia, with or without Ebstein's anomaly, is a common abnormality recognized prenatally. Both tricuspid valve dysplasia and Ebstein's anomaly result in incompetence and right atrial dilatation. This dilatation may be extreme and lead to secondary lung compression and hypoplasia. An example of relatively mild Ebstein's malformation is seen in Figure 4.14. There is mild right atrial dilatation and the displacement of the septal leaflet of the tricuspid valve into the right ventricle is more exaggerated than normal. Although both tricuspid dysplasia and Ebstein's malformation are relatively uncommon in paediatric practice, they are more commonly seen in prenatal series. This is probably because secondary lung hypoplasia results in early postnatal death in the most severe cases. There are few survivors in cases where the right atrium is significantly dilated during early gestation.
Cardiac tumours are not infrequently seen in prenatal life. They carry a high risk of blood flow obstruction, foetal hydrops and intrauterine death. Cardiac teratomas have been identified, but the majority of tumours are rhabdomyomas histologically and are associated with tuberous sclerosis. Coarctation of the aorta is a common form of heart disease, but the cases recognized prenatally constitute the more severe end of the spectrum of this disease. The association of cystic hygroma, foetal hydrops, coarctation and Turner's syndrome is
commonly recognized in early foetal life. Clues to the diagnosis of arch anomalies include the recognition of enlargement of the right ventricle and pulmonary artery in relation to the left ventricle and aorta respectively, in early pregnancy. Echocardiography examination of the arch of the aorta reveals varying degrees of narrowing in coarctation, or the arch is incomplete in interruption of the aorta. Progressive arch hypoplasia has been observed during pregnancy, resulting in more severe aortic arch narrowing at term than was expected earlier in foetal life.
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