Fig. 8.1
Anatomy of the systemic, pulmonary venous atrium following the atrial switch procedure in patients with transposition of the great arteries (Reproduced with permission from Roubertie et al. [1])
As in all conditions with a systemic RV, these patients may experience progressive right ventricular failure and tricuspid valve regurgitation in the long term [3, 4]. Significant tricuspid regurgitation with right ventricular failure is associated with decreased survival [3, 5].
An intrinsic malformation of the TV or an injury to the valve could potentially be responsible for the development of regurgitation of the systemic TV. However, based on the anatomical and physiological interactions between the tricuspid valve and the morphological right ventricle in the systemic circulation, the dysfunction of the systemic TV is in general closely related to the failure of the systemic right ventricle, and vice versa [5, 6]. Nearly all patients presenting with right ventricular dysfunction have severe associated tricuspid regurgitation [7].
Treatment options for tricuspid valve and RV failure in these patients include tricuspid valve reconstruction or replacement, staged conversion to the arterial switch operation, or heart transplantation.
8.2 Historical Background and Results of the Atrial Switch Operation
8.2.1 Atrial Switch Operation for Transposition of the Great Arteries
In 1958, Senning first described the atrial switch operation for patients with TGA, using autologous tissue for “rerouting” the atrial flow [8]. In 1963, Mustard presented a similar approach by using synthetic material for the construction of the atrioventricular connection [9]. In both procedures, an atrial baffle is created that redirects the systemic venous blood to the mitral valve and left ventricle, which remains connected to the pulmonary artery. The pulmonary venous blood is redirected to the tricuspid valve and the right ventricle, which remains connected to the aorta. An intra-atrial baffle is created in situ by using the right atrial wall and interatrial septum (Senning procedure) [8] or by means of synthetic material (Mustard procedure) [9].
From the early 1960s to the late 1980s, i.e., for almost three decades, atrial switch operations provided successful treatment of patients with TGA [10, 11]. The first successful arterial switch operation (ASO) was described in 1975 [12]. After that, the ASO gradually replaced the atrial switch operations. The ASO allows anatomical and physiological repair, whereas the Senning and the Mustard operation leave the right ventricle in the systemic position with potential late right ventricular dysfunction.
At the current time, there are few indications for the atrial switch operation [13]; therefore, most of the patients with TGA who were treated with Mustard or Senning operation are in the adult age.
8.2.2 Long-Term Outcome After the Atrial Switch Operation for Transposition of the Great Arteries
The survival of patients with TGA after 25 years is reported to range between 75 % after the Mustard [10, 14] and 90 % after the Senning operation [11]. More than 80 % of the early survivors survive for up to 40 years after the atrial switch operation [15, 16]. Complications of the atrial switch procedures include a dysfunction of the systemic RV, regurgitation of the systemic TV, systemic and pulmonary venous baffle stenosis or leaks, atrial arrhythmias, and late sudden death [3, 10].
Atrial switch procedures are associated with reoperations mainly for baffle complications, systemic ventricular dysfunction, and left ventricular outflow tract obstruction [17].
Most of the survivors of the atrial switch operation for TGA are reported to live in satisfactory social integration [15], present in excellent New York Heart Association (NYHA) functional status (75 % in NYHA I, more than 90 % in NYHA I and II) [16, 18], and exhibit a high ability index. More than 85 % of the patients can be assigned to an ability index 1, and less than 5 % of the patients are unable to work [11, 15]. This all contributes to a good quality of life [10, 15, 16]. However, with increasing age of the adult TGA patients corrected on the atrial level, the very-long-term function of the RV supporting the systemic circulation remains a concern. It may be expected that systemic ventricular failure and tricuspid valve regurgitation will become a relevant problem in most of these patients [3, 16].
8.2.3 Disadvantages of the Right Ventricle and the Tricuspid Valve in the Systemic Circulation
During long-term follow-up, some degree of systemic right ventricular dysfunction develops in the majority of patients after the atrial switch operation for TGA [3]. This suggests that the morphological right ventricle may lack some specific features of the left ventricle when it is connected in the systemic circulation. The anatomical and physiological differences between the left and the right ventricle have been addressed in detail by Van Praagh (Table 8.1) [19].
Table 8.1
Anatomical and physiological differences between the left and the right ventricle according to Van Praagh and Jung [19]
Left ventricle | Right ventricle | |
|---|---|---|
Intended function | High-pressure pump | Low-pressure/low-volume pump |
Cavity shape | Cylindric | Crescentic |
Contraction pattern | Concentric | “Bellows”-like |
Coronary perfusion | Two coronary arteries | One coronary artery |
Conduction system | Two conduction system radiations | One conduction system radiation |
Inlet and outlet valves | Close proximity | Distant |
Van Praagh also described the anatomical and physiological differences between the tricuspid and the mitral valve which might be responsible for the development of the regurgitation of the tricuspid valve in the systemic position [19]. Van Praagh postulates that the deep anterior leaflet and the shallow posterior leaflet of the mitral valve efficiently occlude a circular orifice of the systemic ventricle. Opposed to this, the leaflets of the tricuspid valve have approximately the same depth and are designed to occlude a crescentic orifice, which may predispose to tricuspid regurgitation in the systemic circulation [19]. Furthermore, he postulates that the morphological differences in the papillary muscles of the two ventricles may contribute to tricuspid valve failure during prolonged exposure to systemic pressure. Multiple small papillary muscles that arise from the interventricular septum and the free ventricular wall support the tricuspid valve. Dilatation of the RV may pull the papillary muscles apart, favoring the development or aggravation of tricuspid regurgitation [19]. In contrast, the two large papillary muscles of the mitral valve are attached to the free wall of the left ventricle. In the setting of ventricular dilatation, these muscles are therefore not strongly separated, making the valve somewhat resistant to development of regurgitation.
8.2.4 Tricuspid Valve Regurgitation After Atrial Switch Operation in TGA Patients
The incidence of various degrees of tricuspid valve regurgitation after the atrial switch operation [20] reaches 52 % in some series [21]. The degree of tricuspid regurgitation is usually mild, and symptoms or hemodynamic relevance are rare when tricuspid regurgitation occurs in the absence of RV failure [22, 23]. Possible causes of tricuspid valve regurgitation in the systemic circulation include:
1.
Intrinsic malformation of the atrioventricular valve
2.
Mechanical injury to the tricuspid valve during previous operations and interventions
3.
Dysfunction of the right ventricle in the systemic circulation
8.2.4.1 Intrinsic Malformation of the Tricuspid Valve
Intrinsic abnormalities of the tricuspid valve associated with TGA, such as valvular dysplasia, double orifice, chordal straddling, and abnormal chordal insertion [24], are found very rarely [1]. The atrial switch procedure, which leaves the TV in the systemic, high-pressure system, might worsen the function of such an altered tricuspid valve and lead to chronic tricuspid regurgitation [25].
8.2.4.2 Mechanical Injury to the Tricuspid Valve During Previous Operations and Interventions
Many TGA patients are treated by balloon atrial septostomy prior to the corrective surgery [26]. Iatrogenic lesions to the tricuspid valve during the Rashkind procedure, including rupture of the papillary muscle, rupture of the chordae, and tear of the anterior valve leaflet, may occur in rare incidences [25, 27].
TGA is associated with a ventricular septal defect (VSD) in approximately 45 % of the cases [4]. Some groups report that tricuspid regurgitation may occur more frequently in TGA patients with a VSD [6, 21]. This may be related to intrinsic abnormalities of the tricuspid valve [24, 28], intraoperative injury [21], or distortion of the valve during VSD closure [29]. The origin of tricuspid regurgitation may play an important role for the function of the tricuspid valve in the systemic right ventricle. In patients with TGA and VSD, the degree of tricuspid regurgitation immediately after Senning operation may predict the outcome and eventual failure of the systemic right ventricle [30]. Some studies show that in TGA patients with VSD, systemic RV failure after atrial switch operation occurs earlier than in those with an intact interventricular septum [6]. There is also evidence that the presence of a VSD prior to atrial-level correction has an influence on late mortality [10, 31]. However, other groups report that the freedom from reoperation for tricuspid valve regurgitation is similar in patients who had undergone transtricuspid VSD closure at the time of the Senning operation, compared to patients who did not [17]. Although complex TGA is found to be a risk factor for the development of late right ventricular failure, the direct connection between intraoperative damage to the tricuspid valve during VSD closure and RV failure has been questioned by some of the more recent publications [1]. Patients presenting with a VSD were usually subjected to chronic cyanosis for a longer time, since they were corrected at an older age than the patients with an intact interventricular septum [1, 11]. The longer time of chronic cyanosis may affect the myocardial function and may predispose the patients to right ventricular dysfunction and tricuspid regurgitation.
8.2.4.3 Dysfunction of the Right Ventricle in the Systemic Circulation
Right ventricular dysfunction is a well-known late complication following atrial switch operation and is described in all studies. Since the intrinsic malformations and mechanical injuries to the tricuspid valve seem to be rare, it can be postulated that right ventricular dysfunction may be the main reason for the development of tricuspid valve regurgitation [17]. In the recent studies, the incidence of moderate and severe systemic RV dysfunction is reported in a wide range of 11 % [15] to 30 % [1, 16, 18]. Progressive congestive heart failure is also one of the most common causes of late mortality [15, 16]. Freedom from reoperation for systemic ventricular failure, which includes the procedures on the tricuspid valve, is reported to be around 96 % at 25 years of follow-up [17]. Recently, Szymański proposed a functional classification of tricuspid valve lesions in patients following an atrial switch for TGA [32]:
Type I: Predominant annular dilatation without significant tethering or prolapse
Type II: Excessive leaflet motion (prolapse)
Type III: Systolic leaflet tethering (restriction)
These three types were associated with diverse severity of right ventricular dysfunction and brain natriuretic peptide activation (Table 8.2).
Table 8.2
Comparison of different functional types of tricuspid regurgitation in patients after atrial switch operation for complete transposition of the great arteries, according to Szymański et al. [32]
Annular dilatation | Leaflet prolapse | Leaflet tethering | |
|---|---|---|---|
Occurrence | 15 % | 41 % | 44 % |
End-systolic right ventricular cavity area | ↑↑ | ↑ | ↑↑↑ |
Right ventricular fractional area change | ↓↓ | ↓ | ↓↓↓ |
BNP levels | ↑↑ | ↑ | ↑↑↑ |
Effective regurgitant orifice area | ↑↑↑ | ↑ | ↑↑ |
8.3 Surgical Treatment of Tricuspid Valve Regurgitation Following an Atrial Switch Operation in TGA Patients
8.3.1 Indication and Surgical Options for the Failing Right Ventricle and Tricuspid Regurgitation
The degree of tricuspid regurgitation in TGA patients following the atrial switch operation correlates with the severity of systemic right ventricular dysfunction [15, 16, 20]. Selection of the optimal surgical strategy, especially in patients in their third or fourth decade of life is a complicated issue.
In the absence of RV impairment, the degree of TV regurgitation is usually mild and insignificant [22, 23]. Accordingly, reoperations are rarely needed for isolated tricuspid regurgitation [1, 6]. Significant systemic tricuspid valve regurgitation may prompt surgical referral when the problem relates to intrinsic tricuspid valve disease or to a mechanical injury to the valve. Moderate to severe systemic tricuspid valve regurgitation without significant ventricular dysfunction is currently the only accepted indication for surgery with a high evidence level (Class I, Level B) [4].
Evaluation for a possible surgical treatment of these patients has to take into account the function of both ventricles; the function of all heart valves; the presence of associated lesions, such as left ventricular outflow tract obstruction; the cardiac rhythm; and finally the age of the patient [17]. The reoperations in these situations are usually complex and may involve concomitant procedures such as baffle revisions, mitral valve procedures, or pulmonary artery banding [17, 20]. These operations should primarily be executed by surgeons with extensive training and expertise in congenital heart disease [4].
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