# Echocardiography in the Diagnosis and Management of Tricuspid Atresia
## 5 Echo-Doppler Studies Following Palliative/Corrective Interventions
### Echocardiographic Evaluation Following Completion of Fontan
If the VSD is small and obstructive, the patient is likely to have had a DKS procedure earlier, bypassing the obstruction. Initially unobstructed VSD may become smaller with time [15; 16] and, therefore, the echo studies should attempt to demonstrate obstruction across the VSD or the lack of it. Cross-sectional views of the Fontan conduit were shown in Figures 38-40. Imaging of the conduit longitudinally is also possible (Figure 46) and laminar flow in the conduit (Figure 46B) is indicative of a nonobstructive conduit. The connection between the IVC and the conduit (Figures 47 and 48) can also be demonstrated by echo studies. Doppler interrogation demonstrating low flow velocities across this region (Figure 49) is indicative of nonobstructive IVC-conduit junction. Turbulent flow and high Doppler velocity across this region suggest obstruction; however, this is rarely seen. Figure 44: Selected video frame from an apical four-chamber view demonstrating the left ventricle (LV) and hypoplastic right ventricle (RV) in a patient who had a Fontan procedure. Note that the RV protrudes into the left ventricular (LV) outflow tract. Cross-sectional view of the conduit (C) is also shown. LA, left atrium. Figure 45: Selected video frame from an apical four-chamber view demonstrating that there is no evidence for left ventricular outflow tract (LVOT) obstruction in the patient shown in Figure 43. Note laminar flow across the LVOT in (**A**) and low Doppler flow velocities across the LVOT (**B**) and aorta (Ao) (**C**). LV, left ventricle. Figure 46: Selected video frame demonstrating wide open conduit (COND) by 2D (**A**) and color flow imaging (**B**). Note laminar flow in (**B**) indicating no obstruction. Figure 47: Selected video frames demonstrating connection between the inferior vena cava (IVC) and the conduit (C) by 2D (**A**) and color flow imaging (**B**); note that the IVC-C junction is wide open. Surgically created fenestrations (Figures 50-53) can also be demonstrated by color Doppler studies and the mean gradient across the fenestration (Figures 52 and 53) is helpful in determining the physiologic state; a mean gradient of 4 to 8 mmHg is considered adequate. Figure 40:0 Selected video frame demonstrating low velocity flow between the inferior vena cava (IVC) and the conduit (C) shown in Figure 47, suggesting no evidence for obstruction. Figure 40:1 Selected video frames (**A,B**) from an apical four chamber view, similar to Figures 39 and 40, focusing on the conduit (C) (**A**) (left) and with color flow imaging (**B**) demonstrating fenestration (FEN). ATV, atretic tricuspid valve; LV, left ventricle. Angiographic counter part of the Fontan conduit with fenestration is shown, in Figure 54, to have better comprehension of the anatomy of the Fontan. Figure 40:2 A magnified view of the fenestration (Fen), similar to Figure 40:3 C, conduit. Figure 40:4 Selected video frame with Doppler sampling across the fenestration (Fen) demonstrating a mean gradient of 4 mmHg. Figure 40:5 Selected video frame with Doppler sampling across the fenestration (Fen) demonstrating a mean gradient of 8 mmHg. The demonstration of the patency of a bidirectional Glenn component (Figures 25-27 and 30) of the Fontan is similar to that described in the section on \"Echocardiographic Evaluation Following Bidirectional Glenn\". Color and CW Doppler interrogation across the SVC/PA/Conduit (Figure 55) is performed to ensure that there is no obstruction across this region. Following the device closure of the fenestration, the position of the device and lack of residual shunting (Figure 56) can usually be demonstrated on echo-Doppler studies. This is the counterpart of the appearance of device closure, seen during angiography (Figure 57). Figure 40:6 Selected cine frames in postero–anterior (**a**) and lateral (**b**) views, demonstrating Stage IIIA Fontan procedure diverting the inferior vena caval (IVC) flow into the pulmonary arteries via a nonvalve conduit (Cond). Flow across the fenestration (Fen) is shown by arrows in **(a,b)**.