Aorta – coarctation
Tricuspid dysplasia can be difficult to distinguish from Ebstein’s malformation, in fact the two overlap each other in terms of anatomical findings. The differentiation is not important. The displaced tricuspid valve cusps can be difficult to find in a severe case of Ebstein’s malformation and may therefore be mistaken for an unguarded orifice. However, in this condition, there is gross tricuspid regurgitation with hepatic congestion. If the left ventricle is very small and compressed by the right atrium it may be mistaken for a hypoplastic left heart, although this diagnosis should be reserved for cases of mitral atresia. The dilated right atrium has been mistaken for an intrathoracic cyst but blood flow within the atrial chamber should distinguish the two.
In fetal life, the first clue to the diagnosis is asymmetry of the four chamber view, with the right ventricle dilated relative to the left. The left atrium, left ventricle and ascending aorta are slightly small for the gestational age. The pulmonary artery/aortic ratio is increased above normal and this and the hypoplasia of the transverse arch are more reliable predictors of this malformation than the relative ventricular sizes. The interatrial shunt is often reversed to become left to right. The transverse arch is narrowed in the horizontal views, especially in comparison with the arterial duct which will appear ‘fat’. It is unusual to see a discrete shelf in the posterior arch, which typifies this lesion in postnatal life. Associated cardiac lesions which are common include VSD and aortic stenosis. As the pregnancy advances, the left heart can become progressively hypoplastic, such that this can develop into a form of hypoplastic left heart syndrome.
Other causes of right heart dominance should be excluded. An increase in the RV/LV ratio can be normal in late gestation, after about 30 weeks, but the other findings will not be present. Disproportion is always abnormal in early pregnancy. Cardiac causes of an increase in RV size include total anomalous pulmonary venous drainage and tricuspid incompetence.
RV larger than LV.
Left to right inter-atrial shunt.
PA much larger than Ao.
Narrow transverse arch, ‘fat’ duct Discrete narrowing of the arch before the ductal connection (rarely identifiable).
- X (Turner)
- Familial coarctation of aorta
- Fetal Hydantoin
- Fetal valproate
- Trisomy 9 (mosaic)
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