d-Transposition of Great Arteries

In d-Transposition of Great Arteries, there is an inversion of the ventriculo-arterial segments. As such, the aorta is coming out of the right ventricle and the pulmonary artery is coming out of the left ventricle. The coronary arteries are connected to the aorta, and their configuration may be diverse. The left ventricle will face pulmonary vascular resistances (PVR). In the context of an open ductus arteriosus and high PVR, one may observe a reverse differential of saturation with the right arm saturating < the lower limbs, since saturated blood enters the post-ductal aorta. In the parasternal short axis view, when PVR have dropped, the inter-ventricular septum will be flat or bowing towards the LV cavity. Surgical correction is usually with the arterial switch "Jatene procedure", with the LeCompte manoeuvre (when configuration of great arteries allows for it). The aorta is disconnected and attached to the left ventricle. The native pulmonary valve becomes the neo-aortic valve. The coronary arteries are disconnected and re-attached to the aorta. Waiting too long for surgery may lead to de-conditioning of the left ventricle (since it faces the PVR). However, in the context of a large PDA, the LV may be facing relative iso-systemic pressure. A large PDA may lead, after prolonged period of time, to over-circulation and these patients may present with significant pulmonary edema and respiratory symptoms. As such, the surgery is usually done at 7-14 days. The LeCompte manoeuvre consists on arranging the great vessels in a way where the pulmonary artery becomes anterior to the ascending aorta.

It is typical to observe the great vessels to be parallel in the parasternal long axis view. The valves are observed on the same plane. In this view, the pulmonary valve is posterior and to the left of the aortic valve. The aorta is anterior and to the right of the pulmonary artery (d-transposed).

By: Erica K. Schallert, MD • Gary H. Danton, MD, PhD • Richard Kardon, DO Daniel A. Young, MD

If the aorta is anterior to and rightward of the MPA, the anomaly is described as dextrotransposition, or d-transposition, of the great vessels, which is denoted as “{_, _, d-TGV}”; if the aorta is anterior to and leftward of the MPA, the anomaly is described as levotransposition (l-transposition) or congenitally corrected transposition, which is denoted as “{_, _, l-TGV}.” If the aorta is neither anterior nor posterior to the MPA, the great vessels are usually described as malpositioned: If the aorta is rightward of the MPA, the anomaly is described as d-malposition, which is denoted as “{_, _, d-MGV}”; if the aorta is leftward of the MPA, the anomaly is described as l-malposition, which is denoted as “{ _, _, lMGV}.”

The pulmonary valve is seen in the parasternal short axis view, as posterior and to the right of the aortic valve (the aortic valve is anterior and to the left of the pulmonary valve).

Pulmonary arteries.

The inter-ventricular septum flattens in systole since the LV is exposed to PVR and RV is exposed to SVR.

Apical 5 chamber view with PA coming out of the LV

Great vessels are seen parallel to each other, with a mostly left to right PDA.

Sweep in Apical view demonstrating that the Aorta is coming out anteriorly of the RV.

Atrial septostomy (Rashkind balloon procedure)

Some patients may require atrial septostomy, which allows for increased mixing. In our centre, the procedure is done at the bedside in the neonatal intensive care unit. A catheter is introduced in the right atrium by an umbilical approach (or femoral approach if the umbilical one is unsuccessful). The balloon goes through the foramen ovale and is inflated and then pulled in order to open the inter-atrial septum. One may need to pay attention to the mitral valve, and avoid avulsion of the valve when pulling the balloon.

Post-septostomy, one will re-evaluate the inter-atrial septum with 2D and colour and ensure that there is adequate mixing. Often, the saturation will progressively rise. Also, one will have to keep in mind that as the PVR are dropping, the pulmonary blood flow will increase, as well as the pulmonary venous return. The velocity of flow through an atrial septum may increase with increasing pulmonary blood flow. Furthermore, With iso-systemic PA pressures, the PDA (or a VSD) may not allow for sufficient mixing in the context of a d-TGA.

Another case of d-TGA:

Created by Gabriel Altit - Neonatologist / Créé par Gabriel Altit (néonatalogiste) - © NeoCardioLab - 2020