First trimester fetal echocardiography was introduced two decades ago. This service is usually available in specialist fetal medicine units but it is not included in routine prenatal screening programs. Early fetal heart assessment is important as it can provide early reassurance or diagnosis of a cardiac abnormality which may potentially instigate further investigation. First trimester fetal echocardiography also provides an insight into the early features and progression of certain forms of congenital heart disease (CHD). In this chapter, the technique of early fetal echocardiography, and first trimester sonographic markers for possible CHD are presented.
KeywordsCongenital heart disease Fetal heart First trimester Evolution First trimester markers of congenital heart disease
The heart is seen in an apical four-chamber view. It occupies about one-third of the thorax. If the angle between the interventricular septum and the midline of the thorax is measured, the normal value at first trimester is about 50°. The two atriums and ventricles are seen in transverse cut. The atria and ventricles are of equal size. The foramen ovale in the centre of atrial septum and the septum primum are seen. There is a subtle ‘off-setting’ of the atrioventricular valves as the septal leaflet of the tricuspid valve is inserted lower in the ventricular septum than the mitral valve. The ventricular septum appears intact from apex to crux. Colour flow Doppler demonstrates equal ventricular filing of the left and right ventricles on the right-side panel image. This is a normal four-chamber appearance at first trimester (MP4 9065 kb).
This is an apical four-chamber view demonstrating a complete atrioventricular septal defect as there is loss of offsetting of the atrioventricular valves. The primum atrial septum is not extending to the atrio-ventricular junction. A common atrioventricular valve can be appreciated in this 13 week fetus (MP4 4056 kb).
This is a correct apical four-chamber plane demonstrating enlargement of the right atrium on 2D on the left side panel. On the right sided panel the simultaneous image of the colour Doppler shows significant tricuspid valve regurgitation as the cause of the right atrial dilatation. The TR jet arises towards the apex of the RV consistent with displacement of the tricuspid valve (MP4 2432 kb).
First trimester sweep of great arteries. In this transverse cut the left ventricular outflow tract is first seen in colour and then the transverse aortic arch and the pulmonary artery meet in a “V” shape anterior to the trachea. Both arteries have antegrade flow and appear equal in size (MP4 3424 kb).
First trimester sweep of great arteries. In this transverse cut normal four-chambers are seen and then the parallel arrangement of the great arteries on both 2D and colour Doppler flow is shown in this early example of the transposition of the great arteries at 13 weeks gestational age (MP4 9000 kb)
This video shows a normal four-chamber view but a further sweep cranially reveals one large great artery arising from the centre of the heart without obvious early branching. This vessel (aorta) is sitting astride a large outlet ventricular septal defect. Colour flow Doppler demonstrates antegrade flow within the large artery (aorta) and in the much smaller one (pulmonary artery), which arises from the anterior right ventricle and crosses over the first one. This constellation of findings in this 13 week fetus is consistent with tetralogy of Fallot (MP4 11711 kb).
This first trimester image demonstrates left aortic arch and an aberrant right subclavian artery arising from the descending aorta behind the trachea and below the transverse aortic arch and heading towards the right shoulder (MP4 6327 kb).