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Abstract
We report a case with prenatal diagnosis of transposition of great arteries (TGA) with L-posed aorta (SDL-TGA) which was confirmed by postnatal echocardiography. The anatomic findings were confirmed during the successful arterial switch operation (ASO). The technical challenges of ASO in the L-posed aorta are also described.
Keywords: Arterial switch operation, L posed aorta, Prenatal, TGA, transposition of great arteries
How to cite this article: Case Report 
A 25-year-old pregnant woman was referred to us at 33 weeks of gestation in view of the fetus with suspected congenital heart defect (CHD) in the antenatal scan. There were no associated extra-cardiac anomalies. The early pregnancy genetic markers were normal, including a normal nuchal translucency (1.2 mm at 12 weeks).
Fetal echocardiography [Figure 1]a, [Figure 1]b, [Figure 1]c, [Figure 1]d, [Figure 1]e, [Figure 1]f, [Figure 1]g showed situs solitus with atrioventricular concordance and D-looped ventricles. The systemic and pulmonary venous drainage was normal. The atrial septum was unrestrictive. The left ventricular outflow tract view showed a large defect in the conoventricular region of the interventricular septum. The first outflow tract emerging from the heart was bifurcating, suggestive of pulmonary artery (PA), and this outflow was overriding the ventricular septal defect (VSD). On further sweeping anteriorly, the aorta (Ao) was seen arising from the right ventricle (RV). Aorta was noted to be anterior and to the left of PA. The three-vessel view showed only two vessels – aorta (Ao) and superior vena cava (SVC), with the Ao occupying a leftward position relative to the SVC with a wide gap between the two vessels. The aortic arch was normal. 3D/4D spatiotemporal image correlation (STIC) with inversion mode rendering demonstrated all the anatomic features confirming the diagnosis of SDL-TGA [Movie 1].
Figure 1: Fetal echocardiography images: (a and b) Situs solitus with a normal 4-chamber view with atrioventricular concordance, (c): The first outflow tract was over-riding a conoventricular VSD and was noted to be bifurcating, suggestive of PA, (d) On further sweeping anteriorly towards the outflow tract view, the Ao was seen arising from the right ventricle suggestive of transposition of great arteries, (e) The three-vessel view showed only two vessels i.e., Ao and SVC and the location of Ao was far left of SVC suggesting L-posed Ao, (f) A rendered display of the three-vessel tracheal view showing the great artery relationship. The bifurcating PA was right and posterior to the Ao, confirming aortic position as L-posed Ao, (g) Normal Ao arch. LA: Left Atrium, RA: Right atrium, LV: Left ventricle, RV: Right ventricle, RPA: Right pulmonary artery, LPA: Left pulmonary artery, Des Ao: Descending Aorta, PA: Pulmonary artery, Ao: Aorta, SVC: Superior vena cavaAfter a detailed prenatal counseling, the family opted for a planned delivery in our center. A male baby weighing 3.1 kg was delivered at term gestation by elective cesarean section for maternal indication. Postnatal echocardiography [Figure 2]a, [Figure 2]b, [Figure 2]c confirmed the diagnosis of TGA, large conoventricular VSD with L-posed Ao, and unobstructed outflows. The atrial septal defect was restrictive. In view of low oxygen saturation, the baby was taken up for balloon atrial septostomy on day 2 of life. Postprocedure, the baby's condition stabilized and subsequently underwent ASO with VSD closure on day 12 of life.
Figure 2: Postnatal echocardiography images. (a) Apical 4 chamber view with a cranial tilt showing conoventricular septal defect (VSD) with first outflow tract, (b) Parasternal long axis showing a bifurcating great artery arising from LV suggestive of PA. The VSD is also seen below the pulmonary artery. PA-mitral continuity is seen, (c) The great artery relationship. Ao is anterior and to the left of pulmonary artery (PA). PA: Pulmonary artery, RV: Right ventricle, VSD: Ventricular septal defect, LV: Left ventricle, PA: Pulmonary arteryIntraoperatively, the anatomic findings of TGA with L-posed Ao were confirmed [Figure 3]a. The coronary anatomy showed a dual coronary system from facing sinuses. The arterial switch was performed by the closed technique using hypothermic cardioplegic arrest. In view of the L-posed Ao, the left-sided coronary button was placed at a higher level compared to the right-sided one. The distal pulmonary opening for anastomosis had to be lateralized toward the left PA (LPA) to maintain a “kink-free” neopulmonary anastomosis and to avoid compressing the anteriorly placed right coronary button [Figure 3]b and [Figure 3]c. The postoperative period was uneventful; the baby was extubated on postoperative day 1 and was discharged home after 8 days. On first follow-up after a month, the baby was doing well with good weight gain. Echocardiography showed mild turbulence across the reconstructed RV outflow (peak gradient of 30 mmHg).
Figure 3: (a) Intraoperative picture showing aorta arising from RV and Ao is anterior and left of PA. RCA is seen in right AV groove. RA-right atrium; LA-left atrium, LAD-Left anterior descending artery, (b) Cartoons showing arrangement of great arteries and coronaries in TGA-SDD, before and after surgical correction. Ao is anterior and to the right of PA. After ASO, neopulmonary artery lies anterior and to right of aorta. (c) Cartoons showing arrangement of great arteries and coronaries in TGA-SDL, before and after surgical correction. In TGA-SDL, Ao is anterior and left of PA. During ASO, the neo pulmonary anastomosis is directed to the left of the PA confluence, almost onto the left PA in order to maintain a straighter alignment of the neopulmonary anastomosis and to avoid compression of the anteriorly placed RCA by the PA. RV: Right ventricle, LV: Left ventricle, LAD: Left anterior descending artery, RA: Right atrium, LA: Left atrium, PA: Pulmonary artery, RCA: Right coronary artery, AV: Atrio-ventricular, Ao: Aorta, ASO: Arterial switch operation Discussion TGA is relatively common defect with a prevalence of 0.2 per 1000 live births, accounting for 5% of all CHDs.[1],[2] SDL-TGA is a rare entity accounting for 0.3% of CHDs and 4% of anatomically proven TGA.[3]
Houyel et al. described the anatomic and surgical aspects of SDL-TGA in a study based on 26 cases of SDL-TGA.[4] SDL-TGA is often associated with additional anomalies that influence surgical management. These include conoventricular VSD (96%), posterior and leftward malalignment of the conal septum (80%), RV hypoplasia (50%), pulmonary outflow tract stenosis (27%), ventricular malposition (23%), and single right coronary artery (23%). These anatomic variations were much more common in SDL-TGA compared to the regular TGA. Our case had a large conoventricular VSD with normal dual coronary system.
Surgical techniques used in the correction of SDL-TGA differ from TGA with usual d-posed aorta (SDD-TGA) [Figure 3b]. First, the coronary transfer poses some unique technical challenges in view of L-posed Ao. The closed bove technique of coronary transfer is our choice in such situations.[5] In SDL-TGA, another technical modification one might require is that the left coronary button tends to be placed more laterally and at a higher level on the neoaorta. Furthermore, the neopulmonary anastomosis is directed to the left of the PA confluence, almost onto the LPA. This is done to maintain a straighter alignment of the neopulmonary anastomosis and to avoid compression of the anteriorly placed right coronary artery by the PA, which now lies anterior to Ao after the Lecompte maneuver.
In conclusion, prenatal diagnosis and use of advanced imaging modalities such as 3D/4D STIC rendering enables precise segmental diagnosis of complex lesions such as SDL-TGA.[6] This enables parental counseling, planning peripartum care, expedited postnatal cardiac management, and improved outcomes as exemplified by this case.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
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Conflicts of interest
There are no conflicts of interest.
References 
Correspondence Address:
Dr. Balu Vaidyanathan
Department of Pediatric Cardiology, Amrita Institute of Medical Sciences, Kochi - 682 041, Kerala
India
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/apc.apc_202_21
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