# Echocardiography in the Diagnosis and Management of Tricuspid Atresia
## 4 Echo-Doppler Features of TA on the Basis of Current Technology  
On 2D echocardiography, the atreticuspid valve is visualized directly as a dense band of echoes at the site where the tricuspid valve should be, as shown in Figures 4-6; this echo appearance is that of the most frequent muscular type of TA. This anatomy is better demonstrated in apical and subcostal four chamber views than in other views. The other anatomic types (Figure 1), namely, membranous, valvular, Ebstein's, atrioventricular septal defect, and unguarded tricuspid valve with muscular shelf, are rare and may also be recognized on 2D echocardiography. An example of an atrioventricular septal defect type of TA [30] is demonstrated in Figure 7; in this example, a 2D echocardiography demonstrated an ostium primary ASD with a common atrioventricular valve and a small RV (Figure 7a,b); the entry into the RV appeared to be occluded by a leaflet of the common atrioventricular valve. Left ventricular and right atrial cineangiograms confirmed these findings [30]. Evaluation of the crux cords (Figure 8) on a 2D echocardiography (subcostal four chamber view) may help to distinguish the various anatomic types (Figure 1) from each other. In the muscular type of tricuspid atresia, a dense band of echoes is seen where the normal tricuspid valve should be (Figure 8A). In membranous types of tricuspid atresia, a thin membrane is seen instead (Figure 8B). In both these types, the anterior leaflet of the detectable atrioventricular valve is attached to the left side of the interatrial septum (Figure 8A,B). In the atrioventricular septal defect type of tricuspid atresia, the crux cords is abnormal and cannot be identified; the anterior leaflet of the detectable atrioventricular defect is attached to the anterior wall of the heart, and a large atrioventricular valve leaflet occludes the entry of the RA into the RV (Figure 8C). Based on these observations, it was concluded that 2D echocardiographic (and angiographic) features help to differentiate the atrioventricular canal type of tricuspid atresia from the classic muscular tricuspid atresia cases [30]. Following the demonstration of the atreticuspid valve, the sizes of the cardiac chambers are evaluated both by M-mode (Z scores) and 2D echocardiography; an enlarged RA, LA and LV and a small RV are seen (Figures 4-6). Pulsed (not shown) and color Doppler (Figure 9) studies are helpful in illustrating right to left shunt across a PFO or an ASD. Figure 6: Selected video frames from apical four chamber, two dimensional echocardiographic views of a patient with tricuspid atresia showing an enlarged left ventricle (LV), a small right ventricle (RV) and a dense band of echoes at the site where the tricuspid valve echo should be (ATV) (thick arrow) with a closed (**A**) and open (**B**) mitral valve. A moderate sized ventricular septal defect (VSD) (thin arrow) is shown. LA, left atrium; RA, right atrium. Reproduced from Reference [29]. The relationship of the great arteries is examined next in order to classify them into various types, as mentioned above. The relationship of the great arteries (Figure 2, top) is established by following the vessels arising from the ventricles until the pulmonary artery (PA) bifurcation or aortic arch. In Type I patients with normally related great arteries, the aorta arises from the LV (Figure 10) and in Type II patients with transposition of the great arteries, the PA arises from the LV (Figure 11; Figure 12). In Type II patients, the blood vessel arising from the LV should be traced to demonstrate its branching into the right and left PAs (Figure 11; Figure 12). In Type III patients, it may be a little more difficult to assign the great artery relationship and, sometimes, other imaging studies, including angiography, may be needed to define the great artery relationship. In Type IV with truncus arteriosus, the limited data suggest that this can be performed by echocardiography (Figure 13; Figure 15).