Background

An anatomical description of transposition of the great arteries (TGA), specifically dextro-TGA or D-TGA with total anomalous pulmonary venous connection (TAPVC), was first published in 1933 [1]. The coexistence of D-TGA and TAPVC is uncommonly described in the scientific literature. With the unknown incidence, only a few publications describing patients who underwent anatomically anomalous diagnostic workups or surgery. The case of coexisting D-TGA and TAPVC in a toddler with cyanotic cardiac disease was described.

Case presentation

A 13-month-old female toddler was referred to the radiology department for a computed tomography (CT) angiography of the chest to evaluate the cardiac vasculature. The infant was diagnosed with cyanosis within her first week of life. Initially, two-dimensional echocardiography had been performed of which revealed atrioventricular ambiguity with pulmonary artery atresia, all pulmonary veins (PVs) drain into the innominate vein (IV) via vertical vein (VV), ostium secundum atrial septal defect (ASD) and ventricular septal defect (VSD) were observed. Left ventricle (LV) present with EF 83%. Right ventricle (RV) had good contractility with tricuspid annular plane systolic excursion of 1.3 cm.

A non-ECG-gated, free-breathing chest CT angiography was performed using a 128-multislice CT scanner (Revolution™ HD, GE HealthCare Technologies Inc., US), with 100 kVP and 150 mAs after 10.5 mL of nonionic, water-soluble, iodine contrast material (Iohexol™ 350 mg/mL) was administered. Advantage Workstation™ VolumeShare 7 (GE HealthCare Technologies Inc, US) was used for image processing.

The CT scan detected levocardia with situs solitus. All four PVs are in confluence behind the small left atrium (LA), and their confluence converges into an ascending lateral large VV, coursing to IV without any PV access into LA. TAPVC was confirmed, with no observable PV access into LA. Large atrial septal defect (ASD) and ventricular septal defect (VSD) were identified (Fig. 1). The superior vena cava (SVC), right atrium (RA) and RV were dilated. D-TGA was suggested after it was discovered that the major arteries of both ventricles were reversed. The RV is the origin of the aortic root. The aorta continues on the right side, with an apparent connection to the aberrant right pulmonary artery at the level of the aortic arch via the arterial communication favors to major aortopulmonary collateral arteries (MAPCAs). Main pulmonary artery originates from LV and appears atretic with only connection to the left pulmonary artery. The liver is located in the midline, and no intraabdominal spleen was identified (Fig. 2). Other identified intraabdominal organs were unremarkable. Schematic cardiac findings are featured in Fig. 3.

Fig. 1
figure 1

Axial and coronal section of CT angiography of the cardiac vasculature. All four pulmonary veins (PVs) are in confluence behind the small left atrium (LA), and their confluence converges to an ascending lateral large vertical vein (VV) which drains into innominate vein (IV) (A–C). The entrance of PV into LA is absent. All the finding favors to supracardiac TAPVC. Large ostium secundum atrial septal defect (ASD) and ventricular septal defect (VSD) were identified (D)

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Fig. 2
figure 2

Sagittal, coronal and axial section of cardiac CT angiography of the cardiac vasculature. Aortic root is originated from the right ventricle (RV). The aorta continues on the right side, with an apparent connection to the right pulmonary aberrant artery at the level of the aortic arch via the major aortopulmonary collateral arteries (MAPCAs) (A). Main pulmonary artery originates from left ventricle and appears atretic with only connection to the left pulmonary artery (PA) (B, C). Aortic valve is located on the anterior right to the pulmonary valve confirming the spatial relationship of semilunar cusps in D-TGA (C). The liver is transversal in position and located in the midline, and no spleen was identified, suggesting a possible heterotaxy syndrome, along with the cardiac anomaly (D)

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Fig. 3
figure 3

Schematic of complex cardiac abnormalities of the reported case with the main feature of co-occurrence of D-TGA and supracardiac TAPVC. The right accessory pulmonary artery (Rt-PA) is supplied by arterial communication from the aorta, favoring major aortopulmonary collateral arteries (MAPCAs). Both ASD and VSD are present. ASD Atrial septal defect, IVC Inferior vena cava, LA Left atrium, Lt-PA Left pulmonary artery, LV Left ventricle, PV Pulmonary vein, RA Right atrium, RV Right ventricle, SVC Superior vena cava, VSD Ventricular septal defect

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Until this report was made, the patient underwent routine follow-up for a surgical plan at a national cardiac surgery center elsewhere. She was scheduled for an initial Blalock–Thomas–Taussig shunt surgery to increase blood flow to the pulmonary circulation before undergoing other definitive surgery.

Discussion

Epidemiology

Very few cases of D-TGA and TAPVC co-occurrence have ever been documented (Table 1). Adults with coexisting D-TGA and TAPVC are quite uncommon. The majority of these occurrences occurred in newborns, and younger children. The oldest patient documented in medical literature was 22 years old [2]. The incidence of TAPVC is increased in individuals with heterotaxy syndromes, especially asplenia [3], as is the case with our patient.

Table 1 Cases of coexisting D-TGA and TAPVC reported in the literature
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Presentation

Total anomalous pulmonary venous return (TAPVR), total anomalous pulmonary venous drainage (TAPVD), and total anomalous pulmonary venous connection (TAPVC) are terms that are arbitrarily used and generally regarded synonymous. Hines [22] defines TAPVC as the absence of confluence between the PV and the LA. In contrast, the junction of the pulmonary vein as an entrance to the LA is still maintained and the aberrant drainage is secondary to the presence of some level of left-sided structural atresia in TAPVR.

Consequently, in the isolated TAPVC, all PVs drain abnormally into the systemic venous circulation, rather than the LA. Thus, oxygenated pulmonary blood is rerouted to the right heart and pumped back to the lungs [23]. To gain survival, a portion of the RA's mixed blood is diverted to the left heart via a right-to-left shunt to supply the systemic circulation. This occurs commonly at the atrial level via an ASD, a patent foramen ovale, or less frequently a PDA [23, 24].

In isolated D-TGA, the aorta originates from the RV and is located right and anterior to the PA, which, in the contrary, originates from the LV. Thus, the deoxygenated systemic venous blood goes to the right heart and then to the systemic circulation via the aorta. Similar to TAPVC, a connectivity between the left and right sides, such as an ASD, patent foramen ovale, VSD, or PDA, is necessary for survival [25].

Cyanosis is usually present at birth in cases of isolated D-TGA or obstructed TAPVC. Both abnormalities have a high risk of inducing pulmonary arterial hypertension (PAH) at an early age, although through different mechanisms. In d-TGA, the process begins in utero with the preferential channeling of oxygen-rich inferior vena cava blood into the left heart through the VSD, causing dilatation of the pulmonary arteries and strain damage to the vascular intima, followed by secondary vasoconstriction. In obstructed TAPVC, however, the increase in pulmonary pressures is due to pulmonary venous hypertension, the severity of which is proportionate to the degree of obstruction. The coexistence of TGA and TAPVC reduces the hemodynamic impact of each individual anomaly by limiting severe desaturation and pulmonary overflow. Instead of the pulmonary circulation, the oxygen-rich blood that drains into the RA is delivered to the systemic circulation [21]. Possibly as a result of this reciprocal compensation, cyanosis is less noticeable and may go unrecognized at birth, culminating in an undeveloped and depleted LV as the individual ages [17, 18].

As oxygenated blood from the pulmonary veins is directed to the systemic circulation, the coexistence of TAPVC and D-TGA improves systemic saturations. However, it can cause a milder apparent cyanosis in a relatively asymptomatic infant, obscuring the discovery of a significant congenital heart disease [18]. Clinically, we should suspect this coexisting condition in children with a diagnosis of TGA and severe right ventricular enlargement, but who are significantly less cyanotic than the average child with uncomplicated TGA [9].

Diagnostic workup

Prompt diagnosis and surgical strategy are essential to reducing morbidity and mortality in severe cases. Some of the most intricate aspects of TAPVC may not be depicted by echocardiography, the first and safest imaging technique for cardiovascular anomalies [11, 16]. For mapping the pulmonary veins and other vascular and structural anomalous anatomy without the necessity for invasive cardiac catheterization, CT angiography provides a noninvasive and sensitive alternative. Contrast-enhanced magnetic resonance (MR) angiography is a radiation-free alternative to CT angiography, although younger children may require general anesthesia. For morphological identification in TAPVC, electrocardiography-gated CT and phase-contrast cine MR imaging (PC-MRI) are preferred above non-gated CT [26].

Treatment

The treatment strategy for a patient with coexisting D-TGA and TAPVC must be supported by clinical and radiological data indicating preservation of LV mass and the absence of irreversible pulmonary vascular disease despite the presence of PAH. [18]. A few authors reported surgery as the mainstay of treatment for coexisting TGA and TAPVC. Successful results were obtained using modified atrial switching techniques based on the principles of either Senning [2, 6, 10, 18] or Mustard [5, 7,8,9, 17]. However, in recent years, arterial switch operation (ASO) has become the preferred approach for the TGA.

Few cases have been reported of successful anatomic repair through ASO. The first successful ASO was performed by Lopes et al. on a 22-h-old infant with D-TGA and subdiaphragmatic TAPVC [11], followed by Seliem et al. on a 4-year-old toddler who had d-TGA with supracardiac TAPVC [13], and by Mykychak et al. on TGA and subdiaphragmatic TAPVC [14]. A few number procedures have been performed elsewhere [15, 16, 20]. The similar observations of the late presentation and early regression of the LV serve as limiting factors for ASO.

In D-TGA, the regression of LV mass often begins during the first 2–3 weeks. Beyond this period, the steady decline in PVR deconditions the performance of the LV with a progressive decrease in its muscle mass [18]. In the coexisting D-TGA and TAPVC, only a few have documented variability in the development of LV mass regression, which can occur early [18] or late [20, 21]. Nevertheless, ASO is encouraged within the first 2 to 3 weeks of life. Beyond that period, it may pose the risk of incapability of LV to cope with the acutely increased work of systemic circulation following surgery [9].

LV mass is preserved in TGA patients with a large VSD or PDA, obstruction of LV outflow, unregressed pulmonary vascular resistance (PVR), or a significant aortopulmonary collateral due to the presence of a greater afterload. In cases of extensive interatrial communication alone, the LV mass is often not adequately preserved following a decrease in PVR since there is no afterload and a substantial decrease in LV inflow [18].

A case report by Abah et al. [20] described a satisfactory outcome of a late-treated coexisting TAPVC and TGA, with the advantage of PAH in preserving the LV mass being highlighted. PAH and volume load from the significant right-to-left shunt at the atrial level due to the large ostium secundum ASD provide a pressure stress on the LV without resulting permanent pulmonary vascular disease. The existence of obstructed TAPVC will result in increased PA pressures, which may be beneficial for LV readiness.

Conclusions

Even in the presence of normal cardiac and abdominal situs, TGA can be associated with anomalous pulmonary venous connection. In order to aid clinical decisions and the planning of surgical and catheter-based procedures, it is essential to map the relevant anatomy. For these reasons, understanding of anomalous pulmonary venous drainage and variant anatomy is essential for optimizing the prognosis, particularly in the diagnostically challenging patient.