Atrial Switch Operation: Indications, Senning Technique, and Complications

The atrial switch operation redirects systemic and pulmonary venous return at the atrial level without changing the native ventricular–arterial connections. Historically, the Senning and Mustard procedures were definitive repairs for dextro-transposition of the great arteries (d-TGA). In contemporary congenital heart surgery, however, the principal role of the atrial switch is as the atrial component of anatomical repair for congenitally corrected transposition of the great arteries (ccTGA).

The Senning procedure achieves this redirection predominantly with native atrial tissue. A surgically constructed systemic venous pathway directs superior and inferior caval return toward the morphologic left ventricle (LV), while pulmonary venous blood is routed around this pathway toward the morphologic right ventricle (RV). The operation therefore requires construction of two separate, low-resistance venous pathways within a limited and often geometrically abnormal atrial space.

Atrial Switch Operation #1: Indications and Contemporary Role

1. Historical Role in d-TGA

In d-TGA, atrioventricular concordance is combined with ventriculoarterial discordance. Systemic venous blood therefore passes through the morphologic RV to the aorta, while pulmonary venous blood passes through the morphologic LV to the pulmonary artery, creating parallel circulations.

An atrial switch restores circulation in series by redirecting:

• SVC and IVC return → morphologic LV → pulmonary artery
• Pulmonary venous return → morphologic RV → aorta

The repair is therefore physiologic rather than anatomical: the morphologic RV remains the systemic ventricle.

The arterial switch operation subsequently became the standard anatomical repair for d-TGA because it restores the morphologic LV to the systemic circulation. Consequently, primary Senning or Mustard repair is now limited to exceptional situations, such as selected late presenters with a substantially regressed LV or unusual anatomical circumstances in which an arterial switch cannot reasonably be performed.

The major long-term limitation of historical atrial-switch repair is the persistence of the morphologic RV and tricuspid valve in the systemic circulation, with progressive systemic RV dysfunction and tricuspid regurgitation becoming major determinants of late morbidity.

2. Principal Contemporary Indication: ccTGA

In ccTGA, atrioventricular discordance and ventriculoarterial discordance result in physiologically corrected circulation. Systemic venous blood passes through the morphologic LV to the pulmonary artery, whereas pulmonary venous blood passes through the morphologic RV to the aorta.

This arrangement may initially be well tolerated, but long-term outcome is limited by the morphologic RV functioning against systemic afterload and by the morphologic tricuspid valve functioning as the systemic atrioventricular valve. Significant tricuspid regurgitation and impaired systemic RV function are associated with adverse outcome and provided an important rationale for development of anatomical repair [1].

The objective of anatomical repair is therefore to establish:

• Morphologic LV → systemic circulation
• Morphologic RV → pulmonary circulation

The atrial switch is essential because atrioventricular discordance must be corrected physiologically before the ventricular outflows are rerouted.

Patients considered for anatomical repair generally require two adequately developed ventricles and anatomy that permits reconstruction of the pulmonary and systemic outflow pathways. Systemic RV dysfunction, significant tricuspid regurgitation, or associated intracardiac defects may favor anatomical repair before irreversible ventricular deterioration occurs [2].

3. Senning + Arterial Switch

When the pulmonary valve and ventricular outflow tracts are suitable, an anatomical double-switch repair combines:

1. Senning atrial switch
2. Arterial switch operation

After reconstruction, systemic venous blood is directed through the Senning pathway to the mitral valve and morphologic LV, which ejects through the reconstructed aorta. Pulmonary venous blood reaches the tricuspid valve and morphologic RV, which becomes the pulmonary ventricle.

A normal or usable pulmonary valve and absence of major pulmonary outflow obstruction generally favor this approach [2,3].

The LV must also be capable of assuming the systemic workload. In patients whose LV has functioned chronically at low pulmonary pressure, particularly older children, pulmonary artery banding for LV retraining may be considered. Retraining is not uniformly successful, however, particularly when undertaken at an older age or in the presence of ventricular dysfunction.

4. Senning + Rastelli

When ccTGA is associated with a suitable VSD and significant pulmonary stenosis, pulmonary atresia, or another form of LV outflow obstruction, an arterial switch may not provide an appropriate reconstruction.

The alternative is an atrial switch combined with a Rastelli-type intracardiac repair:

• Systemic venous return → morphologic LV
• LV → VSD → aorta through an intracardiac tunnel
• Morphologic RV → pulmonary artery through an extracardiac conduit

Selection therefore depends fundamentally on VSD location and size, pulmonary outflow anatomy, ventricular relationships, and the feasibility of constructing an unobstructed LV-to-aortic tunnel [3].

In a 65-patient series of anatomical ccTGA repairs, intermediate survival was better after Senning–arterial switch than after Senning–Rastelli, approximately 91% versus 60% at the reported intermediate follow-up [4]. This should not be interpreted as proof of intrinsic superiority of the arterial-switch strategy because the Rastelli group generally has more complex anatomy and significant pulmonary outflow obstruction.

Atrial Switch Operation #2: Procedure Concepts of the Senning Operation

1. Fundamental Physiologic Objective

The Senning operation creates two separate atrial pathways.

Systemic venous pathway

SVC + IVC → intra-atrial systemic venous pathway → mitral valve → morphologic LV

Pulmonary venous pathway

Pulmonary veins → pulmonary venous chamber surrounding the systemic venous pathway → tricuspid valve → morphologic RV

The essential objective is not simply anatomical separation. Each pathway must provide adequate cross-sectional area, smooth curvature, and low-resistance flow throughout the cardiac cycle.

The operation can therefore be understood as a three-dimensional geometric reconstruction rather than simply an atrial septal procedure.

2. Surgical Anatomy in ccTGA

The atrial septum, caval orifices, pulmonary venous orifices, atrioventricular valves, right atrial free wall, and atrial roof must be considered simultaneously.

This is particularly important in ccTGA because cardiac position and orientation may be abnormal. Dextrocardia, mesocardia, abnormal atrial geometry, and unusual ventricular relationships may substantially alter the orientation of an otherwise familiar Senning reconstruction.

The abnormal conduction anatomy of ccTGA is also clinically important. The atrioventricular conduction axis may follow an unusual course, and associated VSD enlargement or intracardiac tunneling can increase the risk of complete heart block. In the 65-patient series reported by Gaies and colleagues, VSD enlargement was associated with surgically acquired heart block [4].

3. Why the Senning Procedure Is Favored

The Mustard operation creates venous pathways primarily using prosthetic or pericardial baffle material. The Senning procedure instead uses mobilized atrial septal and right atrial tissue, supplemented with patch material when necessary.

For contemporary ccTGA anatomical repair, the Senning approach has generally been favored because reported experience suggests relatively low rates of pathway obstruction, baffle leakage, and significant late atrial arrhythmias compared with historical Mustard experience [5].

This advantage does not mean that an entirely native-tissue reconstruction should be pursued at the expense of pathway dimensions. Patch augmentation is appropriate when required to avoid tension or narrowing.

Atrial Switch Operation #3: Stepwise Senning Reconstruction

1. Exposure and Atrial Septal Preparation

The operation is performed through a right atrial incision with careful attention to the sinus node region and superior cavoatrial junction.

The surgeon evaluates:

• SVC and IVC orifices
• Pulmonary venous drainage
• Atrial septal dimensions
• Mitral and tricuspid valve relationships
• Right atrial tissue available for reconstruction
• Overall cardiac orientation

The atrial septum is then mobilized to create a large flap. This tissue forms a major component of the systemic venous pathway and must have sufficient mobility to reach the appropriate atrial wall without tension.

2. Construction of the Systemic Venous Pathway

The atrial septal flap is used to redirect caval blood toward the mitral valve.

The completed channel must accommodate both SVC and IVC return without:

• SVC narrowing
• IVC narrowing
• Acute angulation
• Tension on the septal flap
• Redundant tissue
• Compression by the surrounding pulmonary venous chamber

The superior limb is especially important because the available space is limited and the reconstruction lies close to the sinus node region.

Published experience with contemporary Senning reconstruction in ccTGA has reported SVC pathway obstruction in fewer than 3% of patients, with many such lesions amenable to catheter intervention [5].

3. Construction of the Pulmonary Venous Pathway

After completion of the systemic venous tunnel, the right atrial free wall is mobilized and reconstructed around it, creating an outer chamber through which pulmonary venous blood reaches the tricuspid valve.

The pulmonary venous pathway must remain broad enough to accommodate the combined return from all pulmonary veins. An excessively tight right atrial closure may compress the posterior chamber even when the systemic venous baffle itself appears satisfactory.

Patch augmentation may therefore be used when necessary to increase atrial volume and prevent pulmonary venous pathway narrowing.

The central principle is that enlarging one pathway must not compromise the other.

4. Intraoperative Assessment

Before separation from cardiopulmonary bypass and before leaving the operating room, both pathways should be evaluated.

Assessment includes:

• SVC and IVC pathway patency
• Pulmonary venous pathway patency
• Baffle integrity
• Atrioventricular valve function
• Ventricular filling
• Ventricular systolic function
• Cardiac rhythm

Unexplained elevation of SVC, IVC, or pulmonary venous pressure should prompt immediate reassessment of pathway geometry.

Contemporary experience demonstrates that technically successful Senning reconstruction can provide durable venous routing. In a 19-patient contemporary series, no new systemic or pulmonary venous baffle obstruction was identified during follow-up [6].

Atrial Switch Operation #4: Complications and Long-Term Outcomes

1. Systemic Venous Pathway Obstruction

Systemic venous obstruction can involve either the SVC or IVC limb.

Clinical manifestations include:

• Elevated central venous pressure
• Facial or upper-extremity edema
• SVC syndrome
• Hepatic or systemic venous congestion
• Development of systemic venous collaterals

Discrete baffle stenosis can frequently be treated with balloon angioplasty or stent implantation, although complex or diffuse obstruction may require surgical revision.

2. Pulmonary Venous Pathway Obstruction

Pulmonary venous obstruction may result from an undersized pulmonary venous chamber, excessive atrial-wall tension, distortion of the systemic venous pathway, or progressive scar formation.

Consequences include:

• Pulmonary venous hypertension
• Pulmonary congestion
• Pulmonary edema
• Secondary pulmonary hypertension
• Respiratory symptoms

Because the obstruction may affect the common reconstructed pulmonary venous pathway rather than individual pulmonary veins, careful Doppler echocardiography and cross-sectional imaging may be required.

3. Baffle Leaks

Residual communication between systemic and pulmonary venous pathways may produce either right-to-left or left-to-right shunting depending on local pressure relationships.

Potential consequences include systemic desaturation, volume loading, paradoxical embolic risk, and reduced hemodynamic efficiency.

The available contemporary ccTGA literature is heterogeneous, and reliable overall rates or predictors of Senning baffle leakage have not been established.

4. Rhythm and Conduction Disturbances

Atrial switch procedures involve extensive atrial incisions and suture lines, and the superior reconstruction lies close to the sinus node. Potential late rhythm disturbances include sinus node dysfunction, junctional rhythm, intra-atrial reentrant tachycardia, and other supraventricular arrhythmias.

Complete atrioventricular block represents a separate concern in ccTGA because of the intrinsically abnormal conduction system and the additional ventricular procedures frequently required during anatomical repair.

In one contemporary Senning series, 26% of patients required pacemaker implantation, predominantly reflecting heart block in this complex anatomical population [6]. More recent multicenter experience across anatomical ccTGA repairs similarly demonstrates that pacemaker-requiring complete AV block remains clinically important, although this risk cannot be attributed solely to the Senning component [9].

5. Long-Term Survival and Reintervention

Long-term outcomes after anatomical repair are generally favorable but should not be interpreted as freedom from subsequent morbidity.

A high-volume-center series reported approximately 77% 10-year survival after double-switch repair, with reintervention required in 20% of the overall anatomical-repair cohort [7].

In a larger 113-patient, 19-year experience, 10-year survival was approximately 84% after double-switch repair and 77% after Rastelli–Senning repair. Importantly, this study did not demonstrate a consistent long-term survival advantage for the arterial-switch strategy despite earlier series showing better intermediate outcomes. Morphologic LV dysfunction developed in 14.2% of patients during follow-up and occurred exclusively in the double-switch group [8].

More recent multicenter data reinforce the same overall message: anatomical repair can provide good long-term survival and preservation of the systemic LV, but reoperation and catheter reintervention remain substantial, related to problems including conduits, baffles, pulmonary arteries, and neoaortic valve or root pathology [9].

6. Lifelong Surveillance

Follow-up after a Senning procedure must extend beyond confirmation of early baffle patency.

Surveillance should specifically assess:

• Systemic venous pathway obstruction
• Pulmonary venous pathway obstruction
• Baffle leaks
• Sinus node and atrioventricular conduction
• Atrial tachyarrhythmias
• Mitral and tricuspid valve function
• Systemic LV function after anatomical repair
• Neo-aortic valve and root after arterial switch
• LV-to-aortic tunnel and RV–PA conduit after Rastelli reconstruction

Echocardiography remains central, supplemented when appropriate by cardiac magnetic resonance imaging, computed tomography, ambulatory rhythm monitoring, exercise testing, and cardiac catheterization.

The long-term success of the Senning procedure therefore depends on more than technically correct venous redirection. It requires durable construction of two unobstructed atrial pathways while preserving rhythm and ventricular function, together with appropriate selection of the arterial-switch or Rastelli component according to ventricular and outflow anatomy. Contemporary anatomical repair achieves good survival in appropriately selected patients, but its complexity and substantial reintervention burden mandate lifelong congenital cardiac surveillance.

References

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[2] Devaney EJ, Charpie JR, Ohye RG, Bove EL. Combined arterial switch and Senning operation for congenitally corrected transposition of the great arteries: patient selection and intermediate results. J Thorac Cardiovasc Surg. 2003;125(3):500-507.

[3] Reddy VM, McElhinney DB, Silverman NH, Hanley FL. The double switch procedure for anatomical repair of congenitally corrected transposition of the great arteries in infants and children. Eur Heart J. 1997;18(9):1470-1477.

[4] Gaies MG, Goldberg CS, Ohye RG, Devaney EJ, Hirsch JC, Bove EL. Early and intermediate outcome after anatomic repair of congenitally corrected transposition of the great arteries. Ann Thorac Surg. 2009;88(6):1952-1960.

[5] Barron DJ, Jones TJ, Brawn WJ. The Senning procedure as part of the double-switch operations for congenitally corrected transposition of the great arteries. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 2011;14(1):109-115.

[6] Ferro G, Murthy R, Sebastian VA, Guleserian KJ, Forbess JM. Single-center experience with the Senning procedure in the current era. Semin Thorac Cardiovasc Surg. 2016;28(2):514-520.

[7] Lenoir M, Bouhout I, Gaudin R, Raisky O, Vouhé PR. Outcomes of the anatomical repair in patients with congenitally corrected transposition of the great arteries: lessons learned in a high-volume centre. Eur J Cardiothorac Surg. 2018;54(3):532-538.

[8] Murtuza B, Barron DJ, Stumper O, Stickley J, Eaton D, Jones TJ, Brawn WJ. Anatomic repair for congenitally corrected transposition of the great arteries: a single-institution 19-year experience. J Thorac Cardiovasc Surg. 2011;142(6):1348-1357.e1.

[9] van der Palen RLF, Jacob KA, Kuipers IM, Sarlemijn E, Arrigoni SC, Haas F, Schoof PH, Hazekamp MG. Surgical outcomes of anatomic repair in congenitally corrected transposition of the great arteries: a 28-year, multicentre Dutch experience. Eur J Cardiothorac Surg. 2026;68(2):ezag044.