CASE 15134 Published on 23.11.2017

Prenatal Diagnosis of a Congenitally Corrected Transposition of The Great Arteries.

Section

Cardiovascular

Case Type

Clinical Cases

Authors

Jad Al Haddad, MD 1, Linda Daou, MD 2, Charles Nohra, MD 3, Nabil Helou, MD 4

(1) Lebanese University, School of Medicine, Radiology Department, Beirut, Lebanon
(2) Paediatric Cardiology Department, Abou Jaoude Hospital, Jal El Dib, Lebanon
(3) Gynaecology and Obstetrics Department, Haroun Hospital, Zalka, Lebanon
(4) Radiology Department, Abou Jaoude Hospital, Jal El Dib, Lebanon

Lebanese University, School of Medicine, Radiology Department
Beirut, Lebanon
Patient

30 years, female

Categories
Area of Interest Cardiac, Foetal imaging ; Imaging Technique Ultrasound
Clinical History
We describe the case of a 30-year-old female G1P0A0 who presented to our department for a routine second trimester ultrasound at 22 weeks of gestation.
No history of consanguinity. No medical or surgical history.
Uneventful pregnancy so far, with normal previous blood tests and foetal ultrasounds.
Imaging Findings
Ultrasound was performed following the guidelines presented by the International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) for screening of the foetal heart.
Analysis of the four-chamber view was of primordial importance.
Foetal situs and cardiac axis were normal.
There were four identified cavities, however, the moderator band and a heavily trabeculated wall, the hallmarks of a right ventricle, were not seen anteriorly close to the chest. Instead, the ventricle closer to the chest wall had a smoother contour and proved to be the left ventricle (Fig.1).
Further analysis of the heart chambers demonstrated that the left atrium, receiving the pulmonary veins, was connected to the morphological right ventricle through the tricuspid valve (Fig. 2).
Outflow tract analysis demonstrated corrected transposition of great arteries with the aorta rising from the morphological right ventricle and the pulmonary trunk rising from the morphological left ventricle. Both vessels were lying parallel to each other.
Discussion
Congenitally corrected transposition of the great vessels, also known, as “double discordance” is a rare congenital anomaly with incidence reported as 1 in 33000 live births, representing about 0.05% of cardiac congenital anomalies [1, 2]. It is characterised by atrioventricular and ventriculoarterial discordance.

During embryological development of the heart, the primary heart tube undergoes a left turn instead of the normal right turn, resulting in discordant atrioventricular and ventriculo-arterial connections. In this setting, a morphological right atrium (mRA) will be seen connecting through the mitral valve to a morphological left ventricle (mLV) leading into the pulmonary trunk. A morphological left atrium (mLA) will be seen connecting through the tricuspid valve with a morphological right ventricle (mRV) into the aorta (Fig. 3).

It is unknown why such an abnormal twisting of the primary heart tube occurs, however studies have shown some increased incidence due to environmental factors (hair dye and air pollutants) [3] as well as among families with previous cases of congenitally corrected transposition of the great arteries, with recurrence risks of 2% to 5%.

This “double discordance” of the heart cavities, when isolated, will be completely asymptomatic because of a restored normal physiology and a correct oxygen rich blood flow, hence the term “corrected”. However many associated anomalies (most commonly ventricular septal defects and obstruction of the pulmonary artery outflow tracts) have been described and their seemingly “normal” physiology resulted in many cases in heart failure and cardiac rhythm anomalies. Other associations include Ebstein’s anomaly and coarctation of the aorta [4].

Multiple long-term complications have been described. First, there is an abnormal position of the atrioventricular node and abnormal course of the conduction axis, resulting in an increased risk of developing heart block over time (2%/year) reaching 30% in adulthood. Progressive prolongation of the PR interval is seen until complete heart block develops [5, 6].
Second, there is gradual dysfunction of the systemic right ventricle after the second decade of life because, histologically and morphologically, the right ventricle cannot sustain the demands of a systemic ventricle [6]. This is explained by different myocytic arrangements in the right and left ventricles as well as ischaemia of the myocardium from abnormals myocardial perfusion [7]. Finally, the left tricuspid valve will progressively become incompetent after the second decade of life [6].

Prenatal diagnosis of this entity is particularly difficult when isolated. It is vital to stress the importance of the four-chamber view and the adequate analysis of the ventricular morphology in order diagnose the anomaly if suspected [8].
Differential Diagnosis List
Congenitally corrected transposition of the great arteries or double discordance.
Transposition of the great arteries.
Double discordance as part of a spectrum of congenital cardiac anomalies.
Final Diagnosis
Congenitally corrected transposition of the great arteries or double discordance.
Case information
URL: https://www.eurorad.org/case/15134
DOI: 10.1594/EURORAD/CASE.15134
ISSN: 1563-4086
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