In the Senning repair, two longitudinal incisions are made through lateral walls for the right and left atria. A flap made from the atrial septum is sewn to the free wall of the left atrium (LA) between the left atrial appendage and pulmonary veins, isolating the pulmonary veins behind it. If the flap is not large enough, it may obstruct left pulmonary veins at their orifices. The posterior and anterior edges of the incision through the lateral wall of the right atrium are then sutured to the free margin of the atrial septum and the left atrial incision, respectively, to reroute the deoxygenated caval blood to the mitral valve and the oxygenated pulmonary venous blood to the tricuspid valve. In Mustard technique which is less complicated, the baffle is created by intra-atrial sewing of a trouser-shaped patch of pericardium or synthetic material to the atrial walls (Fig. 10.7). In Mustard, the atrial septum must be excised as much as possible. At the end, the right atrium may be enlarged by a pericardial or a synthetic patch (Fig. 10.8). In both techniques the anatomic LV continues to act as the pulmonary pump and the anatomic RV acts as the systemic pump (Figs. 10.9 and 10.10). The Senning and Mustard repairs still have a small role in the treatment of TGA in patients with fixed subpulmonary obstruction and as part of the “double-switch” type of repair used in the treatment of congenitally corrected transposition of great arteries (ccTGA).

With improvements in critical care and technical skill, the Jatene arterial switch has become the optimal surgery of TGA and can be performed in early weeks of life [17, 18]. To restore the ventriculoarterial relationships, the coronary arteries are excised from the aorta, followed by transection and switch of the ascending aorta and the pulmonary artery. To reduce the risk of coronary artery kinking before their reimplantation, the pulmonary artery is relocated anterior to the aorta (the Lecompte maneuver) (Fig. 10.11). The pulmonary artery may be augmented by using pericardial patch to prevent the possibility of stenosis. Patients with anomalous coronary arteries are not good candidates for the Jatene procedure. In cases in which TGA is associated with a VSD and subpulmonary stenosis, the Rastelli procedure is the preferred method of repair. This procedure consists of a patch closure of the VSD to the aortic valve and placement of a conduit between the RV and the pulmonary arteries [20]. After the Rastelli operation, assessment of possible stenosis or incompetence of the RV-to-PA conduit, LV outflow tract flow, biventricular function, and possible residual shunt is needed. This is probably best achieved by cardiac MRI. After the Mustard or Senning procedure, adults with TGA may develop right ventricular failure and require consideration of new therapies. A 2-stage pulmonary artery banding and ASO may be performed as an alternative to heart transplantation (Fig. 10.12).

Baffle-related complications are a frequent cause of reoperation and account for 30 % of reoperations in patients with history of Mustard operation and 5 % of Senning operation [21–24]. The reason for a higher incidence of baffle-related complications in the Mustard group may be seen in the use of synthetic material or folding of excessive baffle material. Early complications include baffle obstruction or leak and vena cava obstruction [21, 24]. Late surgical complications include leak and pulmonary and/or systemic venous pathway stenosis [24].

Baffle Stenosis. The systemic venous pathway obstruction occurs more often after Mustard repair (15 %) than after the Senning procedure (1.4 %) [22], but there is a trend towards greater obstruction of the pulmonary venous pathway in those who have undergone the Senning procedure (7.6 % versus 3.8 %) [25]. Obstruction of the pulmonary venous pathway can manifest as pulmonary venous hypertension and pulmonary edema. The site of obstruction is typically between the inferior vena cava (IVC) baffle limb and the lateral atrial wall. Less commonly, the left pulmonary veins can become obstructed, causing left-sided edema. Both the superior and inferior caval baffle limbs can develop stenosis, but the SVC limb is more frequently affected (Fig. 10.13). With MR and CT the site of stenosis can be easily identified. The degree of stenosis can also be quantified using MR velocity encoding. Severe stenosis is defined as narrowing on cine images with a peak velocity of over 1.5 m/s and a damped and continuous flow curve. Mild stenosis is defined when the flow is pulsatile and peak velocity in early diastole not exceeding 1 m/s [26]. In chronic SVC stenosis, patients are often asymptomatic, as they may develop collateral flow into the chest wall and paravertebral veins with retrograde drainage into the IVC [27]. Patients may also develop persistent pleural effusions or chylothorax. Chronic stenosis of the IVC is not well tolerated owing to subsequent hepatic congestion and ascites. Venous stenosis can often be treated with transcatheter-delivered stents [28] (see Fig. 25.​11). Pulmonary venous pathway obstruction after Mustard is often identified using phase-contrast imaging that demonstrates increased venous flow velocity or loss of normal phasic flow patterns. However, in the setting of severe obstructions, pulmonary arterial blood flow is redistributed towards the unaffected side resulting in very low venous flow on the affected side masking flow acceleration. In this situation, measuring pulmonary artery flow can be helpful. In case of left pulmonary vein obstruction, arterial flow will be redistributed with more flow shifting to the right side. Reversed diastolic flow in the ipsilateral artery (in the absence of pulmonary regurgitation) and continuous flow in the contralateral pulmonary artery may be seen in severe pulmonary vein obstruction [29].

Baffle Leaks. Leaks in the intra-atrial baffle are more common with Mustard than with Senning repairs. Small defects in the wall of baffle are common and usually hemodynamically insignificant (Fig. 10.14). However, small defects can increase the risk of paradoxical embolus and cerebrovascular event, especially in patients with history of tachyarrhythmias or in the presence of an endocardial pacemaker (see Fig. 30.​13, extracardiac complications). In order to decrease this risk, all TGA patients who require pacemaker implantation typically undergo a thorough pre-procedural imaging evaluation to assess for the presence of a baffle leak. Complex anatomy of the interatrial septum after atrial switch can make detailed analysis of the baffle difficult (Fig. 10.10). Although transesophageal echocardiography can provide most information required to evaluate these cases, in many cases it is not conclusive and additional diagnostic tests are necessary for final decision making. CT is known for its ability to show detailed anatomic structures. It is fast and easy to interpret (Figs. 10.9 and 10.10). However, special injection technique is required to show both sides of the baffle without much streak artifacts (Fig. 10.10). CT has also the advantage of showing additional anatomic problems including a patent ductus arteriosus or anomalous venous return (Fig. 10.6). When the LV is enlarged, it is important to rule out a significant pathway leak with predominant systemic-to-nonsystemic shunt (equivalent of RV enlargement in concordant heart chambers with an ASD). Baffle leaks can sometimes be treated with placement of occluder devices [30] (see Fig. 30.​13, extracardiac complications). The combination of a baffle leak proximal to a baffle stenosis will exacerbate nonsystemic-to-systemic shunting and leads to desaturation, especially with exercise.

Other Complications. Direct operative trauma to the sinus node or damage to its blood supply and scar lines across the atrium have been suggested as the principal causes of sinus node dysfunction in both types of atrial switch operations [7, 31]. Atrial flutter is not uncommon after Mustard repair [22, 31]. Long-term neurologic complications include stroke and seizures, often related to thromboembolic events (see Fig. 30.​14, extracardiac complications). Right (systemic) ventricular failure with secondary tricuspid valve insufficiency is common [23, 25]. These patients can develop progressive cardiomegaly and may ultimately require end-stage heart failure management, including cardiac transplant [25]. Less common complications include pulmonary arterial hypertension (6 %), residual VSD, and dynamic subpulmonary stenosis [32–34] (Fig. 10.6). A mild degree of subpulmonary stenosis is common in patients with TGA following atrial-level repair [32]. More-severe subpulmonary stenosis after baffle reconstruction is rare and can be treated with a left ventricle-to-pulmonary artery valved conduit [33].

Compared to atrial switch, the rate of dysrhythmias is less [35]. Complications that may be seen at imaging after an arterial switch procedure include main pulmonary artery and branch pulmonary artery obstruction, aortic root dilatation with aortic regurgitation, right ventricle outflow tract (RVOT) obstruction, and coronary artery stenosis [36, 37]. The most frequent types of stenosis are discrete pulmonary narrowing at the anastomosis and the right pulmonary artery segmental stenosis because they are draped across the aorta behind the sternum. Dilatation of the neoaortic root is also common, but hemodynamically significant neoaortic valve regurgitation is uncommon [38]. Increased dimensions of the aortic annulus lead to loss of coaptation of the aortic valve leaflets and varying degrees of central aortic regurgitation (Fig. 10.11a). Reduced elasticity of the proximal aorta, reduced LV systolic function, and increased LV dimensions as measured with MRI are frequently observed these patients [39]. It has been reported that there is a substantial risk of early and late coronary artery occlusion or stenosis in patients undergoing an arterial switch procedure. Most of these patients are asymptomatic, at least initially [40]. Because the RVOT and the pulmonary arteries are positioned immediately behind the sternum after the arterial switch procedure, transthoracic echocardiography is a poor method for evaluating obstructive lesions in these vessels. The anatomic and functional significance of such obstructions can be more accurately assessed with MR imaging by using a combination of techniques including cine imaging, gadolinium-enhanced MR angiography, and velocity-encoded MRI [41]. In patients in whom the presence of coronary ischemia is suspected, coronary CT angiography is the imaging modality of choice. However, coronary MR angiography is also useful for the noninvasive investigation of proximal segments of the coronary arteries [42].

If the systemic RV is failing after an intra-atrial repair, morphologically left ventricular reconditioning and an arterial switch operation is an alternative to cardiac transplantation in selected patients [43]. The first step in such an approach is a surgically placed pulmonary artery band (average 1 year). This is necessary because the LV rapidly becomes deconditioned when exposed to the low-resistance pulmonary circuit, losing its ability to generate systemic pressure. Pulmonary artery banding provides adequate LV training if done at an early age, but results in older patients may not be satisfactory [44]. After banding, MRI is used to evaluate ejection fraction, ventricular mass, and tricuspid valve function. With increasing morphological LV pressure after banding, a shift in the interventricular septum and reduction of the tricuspid regurgitation and right ventricle dysfunction are expected. Later the atrial baffle can be taken down, the pulmonary artery band removed, and the arterial switch procedure performed [44] (Fig. 10.12).

Anomalous origin of the coronary artery is not uncommon in TGA patients and may cause problem during arterial switch operation [7]. In adult patients with the history of atrial switch, these anomalies can be seen in diagnostic tests including MRI and CT and could be of surgical significance at the time of anatomic conversion surgeries (Fig. 10.15). In Massoudy et al.’s study [7], the frequency of the potentially relevant surgical features in a large series of autopsied hearts was reported. In 60 % of cases, the right coronary artery (RCA) arose from the right sinus and the left anterior descending (LAD) and left circumflex arteries from the left sinus. In 10 % the LAD originated from the right sinus, taking a retropulmonary course in 50 %, interarterial in 10 %, and preaortic in 40 %. High takeoff above or at the level of sinotubular junction was seen in 16 %. Juxtacommissural origin of coronary arteries, intramural or tangential takeoff, and commissural mismatch of arterial trunks are relatively rare but can lead to accidental injury when the aorta is transected during arterial switch [45] (Fig. 10.5). Furthermore, other features, such as retropulmonary course of the left coronary artery or origin of both the RCA and the LAD from the right sinus, have been shown to be important [46]. These abnormal features can now be diagnosed with accuracy using cardiac CT angiography. With MRI diagnostic-quality images of the coronary ostium and proximal coronary artery, course can be obtained [42]. Anomalies of the coronary veins are rare. However, in patients with intra-atrial baffle after Senning of Mustard operations, part of the coronary sinus tributaries may be divided between the right and left atria (Fig. 10.15). In patients with systemic right ventricle, the coronary veins draining into the right atrium are enlarged.