# Echocardiography in the Diagnosis and Management of Tricuspid Atresia
## 4 Echo-Doppler Features of TA on the Basis of Current Technology
Figure 12: A selected video frame from a parasternal long axis view with color flow mapping of another patient with tricuspid atresia and transposition of the great arteries demonstrating the left atrium (LA), left ventricle (LV), a small right ventricle (RV) and a moderate sized ventricular septal defect (VSD). The vessel coming off the LV bifurcates into right (RPA) and left (LPA) pulmonary arteries. Reproduced from Reference [29]. PA, pulmonary artery. Figure 13: Two dimensional echocardiographic video frames demonstrating (**a**) an atretic tricuspid valve (ATV) between the right atrium (RA) and right ventricle (RV), (**b**) a large subtrutcal ventricular septal defect (VSD), (**c**) thickened and somewhat domed truncal valve (TV) leaflets, and (**d**) the origin of the pulmonary artery (PA) from the posterior aspect of the truncus arterious (TA). LA, left atrium; LV, left ventricle. Reproduced from [PERSON], et al. _Am Heart_ ] 1991;122:829–835 [31]. Further subdivision (Figure 2, bottom) into subtypes a (pulmonary atresia), b (pulmonary stenosis or hypoplasia), and c (normal valve and pulmonary arteries) is undertaken by echo-Doppler examination of the pulmonary valve and PAs, irrespective of the types, I, II, III or IV. Then, the ventricular septum is evaluated; the ventricular septum is intact in most Type Ia cases. In children with Type I (normally related great arteries), the VSD supplies the pulmonary blood flow (Figure 10) while in patients with Type II (transposition of the great arteries) the VSD allows the blood to flow into the systemic circuit (Figure 11; Figure 12). In Type I patients, the VSD is demonstrated by 2D (Figure 10A), and the left to right shunt across it by color (Figure 10B), pulsed and CW (Figure 10C) Doppler signals. The interrogation of the RV outflow tract and PA region should be performed; recording the peak Doppler flow velocity across the RV outflow tract and the pulmonary valve is helpful in identifying obstruction across these sites. The Doppler data from the VSD and RV outflow tract are also helpful in the estimating of PA pressures. In Type I babies, the 2D size of the VSD and the peak Doppler flow velocity across it are useful in quantifying the size of the VSD (Figure 10). The higher the VSD Doppler flow velocity, the smaller the defect. However, in patients with pulmonary hypertension or severe infundibular or valvar pulmonary stenosis, the VSD Doppler velocities are not reflective of the size of the VSD. Barring these exceptions, RV and PA systolic pressure may be estimated using a modified Bernoulli equation (RV/PA systolic pressure = systolic blood pressure - 4V\({}^{2}\)). Figure 14: Video frames from a two dimensional echocardiographic and color Doppler study demonstrating (**a**) an atetic tricuspid valve (ATV) between the right atrium (RA) and right ventricle (RV), and blood flow from the left atrium (LA) into the left ventricle (LV) across the mitral valve. The RV (arrow) is very small and hypoplastic. (**b**) LV and RV with a large ventricular septal defect (VSD) below the truncus arteriosus (TA). Turbulent flow across the truncal valve suggests truncal valve stenosis. (**c**) The origin of the pulmonary artery (PA) from the TA by color flow (arrow), and (**d**) the division into right (RPA) and left (LPA) pulmonary arteries from the PA in a short-axis view. TV, truncal valve leaflets. Reproduced from [PERSON], et al. _Am Heart J_ 1991;122:829–835 [31]. In Type II patients, the VSD may be small, causing obstruction to blood flow to the systemic circuit, and, therefore, the size of the VSD should be ascertained by 2D (Figures 11 and 12), color Doppler (Figure 12), pulsed (Figure 15) and CW Doppler, as necessary. In these Type II patients, a high VSD velocity is indicative of subaortic obstruction. Interrogation of the LV outflow and PA region may reveal pulmonary or subpulmonary stenosis; the higher the velocity, the more severe is the obstruction.