Transposition of the great arteries: A laterality defect in the group of heterotaxy syndromes or an outflow tract malformation?

Abstract

Background/aim: Transposition of the great arteries (TGA) is traditionally classified as a "conotruncal heart defect", implying that TGA evolves from abnormal development of the outflow tract (OFT) of the embryonic heart. However, recently published genetic data suggest that TGA may be linked to laterality gene defects rather than OFT gene defects. The aim of our study was to clarify whether there is any statistically significant link between TGA and clinically diagnosed laterality defects (heterotaxy).

Methods: Retrospective cross-sectional analysis of 533 patients diagnosed with TGA at our cardiac center over a period of 13 years (2002-2015). Hospital informatics and digital data recording systems were used for collecting patients' data and all patients were reviewed to check the echocardiograms for verification of the diagnosis, type (TGA, congenitally corrected TGA (ccTGA), and levo-position of the great arteries (LGA)), complexity of TGA, and all other variables (e.g., abdominal organ arrangement, cardiac position, presence or absence of other cardiac defects).

Results: Of 533 TGA patients, 495 (92.9%) had the usual arrangement of the internal organs, 21 (3.9%) had mirror-imagery, 7 (1.3%) had left and 10 (1.8%) had right isomerism. 444 (83.3%) patients had TGA. The number of patients who had usual visceral arrangement in each TGA type was: 418 (94.1%) in TGA, 49 (92.4%) in ccTGA, and 28 (77.7%) in LGA. 6 (1.4%) TGA patients, 4 (11.1%) patients with LGA were found to have right isomerism, while no ccTGA patient presented with this asymmetry. 4 (0.9%) TGA patients, 1 (1.9%) ccTGA patient and 2 (5.6%) patients with LGA had left isomerism. Heterotaxy (mirror-imagery, left and right isomerism) was more associated with LGA than TGA or ccTGA with a statistically significant difference (P value of 0.001).

Conclusion: In contrast to recently published genetic data, our morphological data do not disclose a significant link between TGA and heterotaxy.

Keywords: Heterotaxy; laterality defects; outflow tract malformation; transposition of the great arteries.

Figure 1

An illustration showing the 4 different variations of bodily organs in the lateralized (left-hand two columns) and isomeric (right-hand two columns) arrangements, including atrial appendages. The upper panels show the atrial appendages morphology, the second upper panel the bronchial morphology, and the relations of the bronchuses to the pulmonary artery feeding the lower lobes of the lungs, the third upper panel shows the pulmonary morphology, and the last lower panel shows the arrangement of the liver, stomach, and spleen. Adopted from: Anderson et al. (J Cardiovasc Dev Dis. 2018;5:11)

Figure 2

A flowchart showing our research methodology

Figure 3

An inadequate chest X-ray of a transposition of the great arteries patient. The quality is not sufficient enough to identify properly the bronchial tree anatomy

Figure 4

An illustration showing the 4 different abdominal organ arrangement variations that can be determined from echocardiograms in the abdominal transverse plane of the so-called subxiphoid (subcostal) views. IVC: Inferior vena cava. Adopted from: Echocardiography in Pediatric and Congenital Heart Disease: From Fetus to Adult. Wyman W. Lai, Luc L. Mertens, Meryl S. Cohen and Tal Geva© 2009. Page: 491

Figure 5

A bar chart showing the distribution of abdominal organ arrangements in transposition of the great arteries patients who had atrioventricular septal defect

Figure 6

A bar chart showing the distribution of abdominal organ arrangements in the transposition of the great arteries sub-groups according to complexity