Magnetic Resonance Imaging of Congenitally Corrected Transposition of the Great Arteries

Clinical History

Asymptomatic 26-year old male with a PA chest X-ray showing straightening of the left upper heart border and no evidence of the pulmonary artery shadow.

Imaging Findings

An asymptomatic 26 year old male was admitted to our hospital because of a pathologic routine chest radiograph obtained for enrollment in army service. PA chest X-ray (fig.1)showed straightened left upper heart border with no evidence of the pulmonary artery shadow. Echocardiography showed dextrocardia and set indications of probable corrected transposition of the great vessels.Patient referred for Cardiac MRI for further evaluation. MRI showed that the morphologic RV was on the left,the morphologic LV was on the right,the aorta originated from RV and was anteriorly and to the left of the pulmonary artery (L-transposition),LA was connected to morphological RV and the RA was connected to morphological LV (fig. 2a,2b,3,4). Thus,the combination of ventriculoarterial discordance and atrioventricular discordance was diagnostic of corrected transposition of the great vessels. Further MRI evaluation revealed a moderate valvular pulmonary stenosis with an estimated peak velocity 250 cm/sec,RV function analysis showed ejection fraction 60%, Qp:Qs=1.There was mild hypertrophy of RV wall . There was no evidence of ventricular septal defect or other anomalies.

Discussion

Congenitally corrected transposition of the great arteries (ccTGA) or ventricular inversion is a rare form of congenital heart disease, first described by Von Rokitansky in 1875, comprised of both atrioventricular and ventriculoarterial discordance. The atrioventricular discordance implies that the right atrium (RA) enters the morphological left ventricle (LV) and the left atrium (LA) drains into the morphological right ventricle (RV). The ventriculoarterial discordance suggests that the RV gives rise to the aorta and the LV supplies the pulmonary circulation. It results during the development of the embryonic heart tube at 4-6 weeks of intrauterine life from failure of the dividing common truncus arteriosus, which gives rise to the aorta and the main pulmonary artery, to rotate and from bending of the heart tube to the left, so-called l-looping. At the completion of this process, though the cardiac apex is normally directed to the left, the morphological LV lies anterior and to the right of the posterior ventricle which is of right morphology (RV) and they give rise posteriorly to the pulmonary trunk and anteriorly to the aorta respectively. CCTGA has a reported prevalence of approximately 0.5% of all cases of congenital heart disease, is of unknown cause and usually associated with a variety of other abnormalities and intra-cardiac defects, i.e. ventricular septal defect (VSD) in 80%, pulmonic stenosis (PS) (usually subvulvar) in 50%, functional systemic abnormalities (usually tricuspid regurgitation) in 1/3 and with some type of AV conduction abnormalities in 1/3 of cases. These additional malformations will finally reflect to the patient's clinical presentation. A plain PA chest radiograph may suggest corrected transposition of the great arteries in the absence of associated defects. Cardiac MRI is a supplementary or alternative imaging technique to echocardiography and cardiac catheterization in diagnosis of complex cardiac congenital anomalies. MRI can identify the morphologic features of ventricles and atria, can identify the atrioventricular and ventriculoarterial connections, can evaluate associated cardiac anomalies, can diagnose and quantify valvular stenoses and regurgitations, can assess the volume, mass and function of right ventricle. MRI is particularly valuable in serial assessment of RV function as it can failure over years, because echo is inaccurate in evaluation of the RV.

Differential Diagnosis List

Final Diagnosis

Congenitally corrected transposition of the great arteries- levocardia

URL:	https://www.eurorad.org/case/3485
DOI:	10.1594/EURORAD/CASE.3485
ISSN:	1563-4086