Congenitally corrected transposition of great arteries

Abstract

Congenitally corrected transposition of great arteries (ccTGA) may essentially present as two clinical phenotypes viz. with left ventricular outflow tract obstruction (LVOTO), presenting as Tetralogy of Fallot (TOF) physiology, or sans LVOTO, presenting with systemic ventricular dysfunction. The natural history and treatment, especially the role of pulmonary artery (PA) band, have been discussed.

Electronic supplementary material

The online version of this article (10.1007/s12055-018-0775-3) contains supplementary material, which is available to authorized users.

The natural history of CCTGA is very variable and there should be a low threshold for intervention in symptomatic patients or those with signs of a failing systemic circulation (Video). These patients should be followed up very closely and considered for intervention at the first sign of right ventricular (RV) dysfunction. Essentially, ccTGA can be divided into two groups:

1. Presenting with LVOTO, which behaves like Tetralogy of Fallot (TOF) physiology or pulmonary atresia. These babies are variably cyanosed, present early, and are relatively easier to manage.

2. No obstruction to the LVOT, who may be symptomless, and can present much later with RV (systemic ventricular) dysfunction [1].

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In the latter group of patients, a PA band can have multiple roles which can be either palliative or preparatory for subsequent anatomical repair (double switch). Many patients (70–80%) have an associated ventricular septal defect (VSD), in which case the PA band has a standard role in balancing the circulation and protecting the lungs from high flow. However, even in the absence of (or a small) VSD, the PA banding splints the inter-ventricular septum and forces it to the right side which provides support to the tricuspid valve, controlling tricuspid regurgitation and may maintain RV function. Some of these patients may never come to need a double switch and PA band in itself would be the definitive procedure [2]. Even if this ideal scenario does not unfold, the PA band helps in preparing (“re-training”) the morphological left ventricle (LV) for the subsequent double switch if required. The great challenge in ccTGA with no LVOTO is the unpredictable nature of the RV (and tricuspid valve) in the systemic position—some patients remain well indefinitely but most develop congestive heart failure, so the decision for intervention (if needed at all) can be very difficult to plan. Ideally, this banding should be done before 2 years of age to give the best long-term results [3], but it is difficult to make this argument in a patient who has preserved RV function and no tricuspid regurgitation (TR) in early childhood. The problem is that attempting to re-train the LV becomes progressively difficult with advancing age and is extremely unpredictable beyond 8–10 years of age. Patients who are banded too late run the risk of the re-trained LV failing late after the double switch.

Nevertheless, with modern care, the abysmal natural history of ccTGA with failing RV of 40% survival at 20 years has improved to around 80–85% survival with anatomical repair (double switch) [4, 5]. Dr. Barron strongly bats for early PA banding, at the first sign of RV dysfunction, as this minimizes the risk of LV failure later in life. This is because the LV plasticity and remodeling is maximized if PA banding is performed early.

For those who develop failure later in life, more conventional treatments have to be considered. Tricuspid valve replacement does have a role if RV function is well preserved and re-synchronization therapy can be very effective in patients with conduction abnormalities. There are also good transplant options in older patients because other co-morbidities are unusual, although abnormalities of cardiac position and situs may force some technical issues at transplantation.