Congenitally corrected transposition of the great arteries: is it really a transposition? An anatomical study of the right ventricular septal surface

Abstract

Congenitally corrected transposition of the great arteries (ccTGA) is a rare congenital malformation which associates discordant atrioventricular and ventriculo‐arterial connections. Although frequently associated with a ventricular septal defect (VSD), its anatomy remains controversial. This could be due in hearts with usual atrial arrangement to the apparently different anatomy of the left‐sided right ventricle compared with a right‐sided right ventricle. We wanted to compare the RV septal anatomy between ccTGA, transposition of the great arteries and normal heart and to determine the anatomy of the VSD in ccTGA. We analysed 102 human heart specimens: 31 ccTGA, 36 transpositions of the great arteries, 35 normal hearts. According to the last classification of VSD (ICD‐11), VSD were classified as outlet if located above the superoseptal commissure of the tricuspid valve and inlet if underneath. We measured the lengths of the superior and inferior limbs of the septal band and the angle between the two limbs. To assess the orientation of the septal band, we also measured the angle between superior limb and the arterial valve above. A VSD was present in 26 ccTGA (84%) and was an outlet VSD in 16 cases (61%). The mean angle between the two limbs of the septal band was 76.4° for ccTGA compared with 90.6° for transposition of the great arteries (P = 0.011) and 76.1° for normal hearts (P= NS). The mean angle between the superior limb of the septal band and the arterial valve above was 70.6° for ccTGA compared with 90.6° for transposition of the great arteries (P = 0.0004) and 69.1° for normal hearts (P= NS). The inferior limb of the septal band was significantly shorter in ccTGA (P < 0.0003): SL/IL length ratio was 21.4 for ccTGA, 2.2 for transposition of the great arteries and 1.5 for normal hearts. The typical VSD in ccTGA is an outlet VSD. Its frequent misdiagnosis as an inlet VSD might be explained by the shortness of the inferior limb, which creates the illusion of a posterior VSD, and by the fact that the VSD is usually assessed from the left ventricular aspect. Surprisingly, the orientation of the septal band is similar in ccTGA and normal heart, despite the discordant atrioventricular connections, and different in ccTGA and transposition of the great arteries, despite the discordant ventriculo‐arterial connections. These findings suggest that the mechanism leading to transposition in ccTGA and in TGA probably is different. The term ‘double discordance’ might therefore be more appropriate as a description of this complex anomaly.

Congenitally Malformed Hearts: Aspects of Teaching and Research Involving Medical Students

“…One innovative inclusion in our examination protocol was the assessment of ventricular septal defect (VSD) topography from the mRV. This is in continuation from a recent publication by Arribard et al [ 25 ], in which they identify the mRV septum of ccTGA to be an identical mirror image of that in normal hearts. Accordingly, VSD assessment should be standardised to the mRV because this allows for the use of the criteria widely agreed in isolated VSD.…”

“…Three of these hearts had their VSD photographed from the mRV using a mirror, to represent the VSD appearing right-sided, similar to concordant atrioventricular connections ( Figure 5 ). We found the VSD in the archive has more diverse topographies when comparing to Arribard et al [ 25 ]. While the majority of their ccTGA hearts had an outlet perimembranous VSD upon assessment from the mRV, our archive had a mix of 2 central, 6 inlet, 1 inlet to outlet, and 4 outlet perimembranous VSD [ 25 ].…”

Percutaneous closure of an atrial septal defect in adult patients with congenitally corrected transposition of the great arteries

“…Furthermore, morphologically left ventricle drainage to the pulmonary artery. A study conducted by Arribard et al 1 mentioned the discordant nature of the atrioventricular connections and not the nature of the ventriculoarterial connections as the major element of this condition; they also suggest the term "double discordance" as a better term for describing this situation.…”

“…Congenitally corrected transposition of the great arteries is a rare congenital anomaly which are responsible for 0.5% of all CHDs (1 out of 33,000 live births). 1 In this anomaly, both ventricles and their associated atrioventricular valves are reversed and there is atrioventricular and ventriculo-atrial discordance. Consequently, on the left side, the tricuspid valve connects the left atrium with the morphologically right ventricle, and aorta originate from morphologically right ventricle; on the right side, the mitral valve connects the right atrium with the morphologically left ventricle, then the morphologically left ventricle communicates with the pulmonary trunk.…”

“…The systemic and pulmonary venous return flows towards the pulmonary trunk and the aorta, respectively. 1 In these patients, the morphological right ventricle (left-sided ventricle) acts as a systemic ventricle and morphological left ventricle is the subpulmonic ventricle that receives blood from the right atrium.…”