Congenitally corrected transposition of great arteries

Congenitally corrected transposition of great arteries

Congenitally corrected transposition of the great arteries (CCTGA or cTGA) is a condition in which there is atrioventricular and ventricular arterial discordance so that the circulation is physiological. Congenitally corrected transposition of great arteries is also known as l-transposition of great arteries (l-TGA) because of the levo transposition of aorta. Levo posed aorta forms a hump along the left upper heart border on chest X-ray.

The right atrium connects to the morphological left ventricle, which in turn connects to the pulmonary artery so that systemic venous blood reaches the pulmonary circulation. The left atrium is connected to the morphological right ventricle which ejects to aorta, thereby ensuring that pulmonary venous drainage reaches the systemic circulation. Thus there is a double discordance with atrioventricular and ventriculo arterial discordance.

Even though it might appear that physiology of independent series pulmonary and systemic circulations is conceptually proper, the prognosis of patients with c-TGA is not that good, even in the absence of other associated cardiac defects [1]. Hence the need for surgical correction. Definitive surgical correction of c-TGA is known as double switch [2]. Atrial switch is by a modified Senning procedure for rerouting the pulmonary and systemic venous return. Arterial switch is done for correction of ventriculoarterial discordance.

The morphological right ventricle fails in one third of cases in those without associated lesions by the fifth decade of life while it occurs in two thirds who had prior surgery for associated lesions, by 45 years of age. This is despite the fact that a nonagenarian has presented with c-TGA [3]. The systemic right ventricle supplied by a single right coronary artery has myocardial oxygen supply/demand mismatch which can lead to subendocardial ischemia, progressive fibrosis and overt heart failure later.

c-TGA accounts for about 1% of patients born with congenital heart disease. Of these, only 1% have uncomplicated c-TGA. Commonly associated abnormalities are pulmonary stenosis, ventricular septal defect and Ebstein like tricuspid valve [3]. As the atrioventricular node is in an unusual position and abnormal course of the atrioventricular conduction system, cardiac conduction disorders are frequent in c-TGA [4]. Atrial situs can be normal or inverted in c-TGA. Normal atrial situs is more common. Congenital complete heart block was found in 15 of the 30 cases with normal atrial arrangement in a series [5]. But it was not seen in any of the 8 cases with situs inversus in that series.

Since the atrioventricular (AV) valves are a property of the ventricles, the systemic right ventricle in this case has a tricuspid valve. Hence it is prone for deformities affecting the tricuspid valve. In up to 70% cases of CCTGA, systemic AV valve (SAVV) may be displaced inferiorly, the Ebstein’s anomaly. This abnormal SAVV is an important cause for regurgitation rather than ventricular dilatation and dysfunction. SAVV was the only independent predictor of death in congenitally corrected transposition of the great arteries in certain series [6]. The prognosis becomes poor when SAVV replacement is delayed and the systemic ventricular ejection fraction falls significantly. Ten year survival after SAVV replacement was only about twenty percent when the preoperative systemic ventricular ejection fraction (SVEF) was below 44% in earlier studies [7].

In a series from Mayo Clinic [8], it was found that late SVEF beyond one year was preserved in 63% of those who underwent surgery with SVEF of 40% or more while it was seen in only 10.5% of those who underwent surgery with SVEF less than 40%. An SVEF of 40% or less, subpulmonary ventricular systolic pressure of 50 mm Hg or more, atrial fibrillation and a poor NYHA class III or IV were the preoperative factors associated with late mortality. The authors recommended that SAVV replacement in those with cTGA and SAVV regurgitation should be advised before the SVEF falls below 40% and the subpulmonary ventricular systolic pressure rises above 50 mm Hg.

References

1. Catherine Deshaies, Paul Khairy. The Paradox of Choice in the Surgical Management of Congenitally Corrected Transposition: What Should We Do With All of These Options Supported by Little Evidence? Transl Pediatr. 2018 Jan;7(1):5-8.
2. Sharma R, Bhan A, Juneja R, Kothari SS, Saxena A, Venugopal P. Double switch for congenitally corrected transposition of the great arteries. Eur J Cardiothorac Surg. 1999 Mar;15(3):276-81; discussion 281-2.
3. Elizabeth A Orchard, Oliver Ormerod, Saul Myerson, Stephen Westaby. Congenitally Corrected Transposition of the Great Arteries Presenting in a Nonagenarian. Circulation. 2010 Aug 31;122(9):e441-4.
4. Baruteau AE, Abrams DJ, Ho SY, Thambo JB, McLeod CJ, Shah MJ. Cardiac Conduction System in Congenitally Corrected Transposition of the Great Arteries and Its Clinical Relevance. J Am Heart Assoc. 2017 Dec 21;6(12):e007759.
5. Oliver JM, Gallego P, Gonzalez AE, Sanchez-Recalde A, Brett M, Polo L, Gutierrez-Larraya F. Comparison of outcomes in adults with congenitally corrected transposition with situs inversus versus situs solitus. Am J Cardiol. 2012 Dec 1;110(11):1687-91.
6. Prieto LR, Hordof AJ, Secic M, Rosenbaum MS, Gersony WM. Progressive tricuspid valve disease in patients with congenitally corrected transposition of the great arteries. Circulation 1998;98:997-1005.
7. van Son JA, Danielson GK, Huhta JC, Warnes CA, Edwards WD, Schaff HV, Puga FJ, Ilstrup DM. Late results of systemic atrioventricular valve replacement in corrected transposition. J Thorac Cardiovasc Surg. 1995;109:642-652.
8. Mongeon FP, Connolly HM, Dearani JA, Li Z, Warnes CA. Congenitally corrected transposition of the great arteries ventricular function at the time of systemic atrioventricular valve replacement predicts long-term ventricular function. Am Coll Cardiol. 2011; 57:2008-2017.