Atrial Switch Operation (Senning) — #3
The Senning operation is an atrial-level redirection: it re-routes venous returns within the atria so that systemic venous blood (SVC/IVC) is guided to the mitral valve → LV → PA, while pulmonary venous blood (PVs) is guided to the tricuspid valve → RV → aorta—with ventriculo–arterial connections unchanged. Technical success in this step is not “closing the atrium,” but engineering two spacious, growth-tolerant channels that avoid (1) pulmonary venous confluence narrowing and (2) kinking/compression where pathways compete for limited atrial space. (PubMed)
1) Core concept for this step
“Build two tunnels that never fight for space.”
- Pulmonary venous pathway (PVs → pulmonary venous baffle → mitral valve)
- Highest-stakes requirement: wide, smooth PV entry with a “roof” that does not sag or ridge.
- Endpoint: laminar streaming toward the mitral inflow axis (not simply a sealed partition).
- Systemic venous pathway (SVC/IVC → systemic venous baffle → tricuspid valve)
- Must remain non-restrictive at the SVC roof and IVC limb, with no torsion along the floor.
- The “space budget” problem (why geometry dominates)
- The atria have limited tissue/volume; every suture line and fold “spends” cross-sectional area.
- The durable Senning is an allocation strategy: preserve one channel without stealing caliber from the other.
2) Stepwise construction (aligned with your figures)
Step A — Initiate the pulmonary venous baffle with an atrial septal flap
Action
- Fashion an atrial septal flap directed toward the LA side to begin the pulmonary venous pathway.
Goal
- A flap generous enough to cover the pulmonary venous confluence and prevent PV orifice “pinching.”
Pearl (geometry language)
- Think endoscopically: no sharp turns and no roof collapse over the PV ostia.
Step B — Use patch augmentation as a geometry tool (not a bailout)
Action
- When native septal tissue is insufficient to create a stable “roof,” augment with a patch to complete the pulmonary venous baffle.
Goal
- A smooth, wide PV channel with no ridge at the PV entry zone.
Practical point
- Classic Senning construction emphasizes autogenous atrial tissue for the baffles, with patch material used strategically where needed for septal reconstruction/coverage. (PubMed)
Step C — Construct the systemic venous baffle using the right atrial free wall (RA flap)
Action
- Use the RA free wall/flap to form the systemic venous channel, directing SVC + IVC flow toward the tricuspid valve (patch augmentation as needed to avoid narrowing/torsion).
Critical spatial rule
- Do not “buy” systemic width by stealing PV space. Pulmonary venous obstruction is less forgiving clinically and technically.
Mental image
- Create a straight, low-resistance “caval-to-TV chute,” not a squeezed corridor with folds.
Step D — Complete the pulmonary venous pathway (continuity + inflow alignment)
Action
- Complete the pulmonary venous channel so PV return is directed toward the mitral valve with continuous, non-kinking walls (often requiring a patch segment to maintain caliber).
Goal
- Preserve the mitral inflow axis and avoid a narrow turn as flow transitions from PV confluence to mitral valve.
Pearl
- The endpoint is laminar streaming, not cosmetic closure.
3) “No-regret” checks before leaving the atrium
A) Pulmonary venous side (highest-stakes early failure mode)
- PV entry must be wide and smooth (no tight ridge at PV ostia).
- Ensure the “roof” does not compress posteriorly over the confluence.
- Confirm no narrowing where the channel turns toward the mitral valve.
B) Systemic venous side (common site for late gradients)
- SVC limb: avoid roof narrowing and kinking from tissue folding.
- IVC limb: avoid a slit-like floor channel; ensure a generous, untwisted path.
C) The crossing/competition zone
- Visually and mechanically confirm that the two baffles coexist without mutual compression (especially in a small atrium).
4) Evidence-informed perspective (why this baffle step predicts late durability)
4.1 Long-term survival is excellent—but rhythm and baffle issues define follow-up
In a large 20-year series (132 Senning patients), actuarial survival remained high (≈88% at 20 years), but sinus rhythm probability declined over time (≈80% → 44%)—highlighting why atrial geometry and suture-line strategy matter beyond the OR. (PubMed)
4.2 Senning vs Mustard: fewer systemic venous pathway obstructions, similar “late physiology” challenges
A nationwide Belgian multicenter cohort (up to 30 years) reported more baffle obstruction after Mustard than Senning (15.3% vs 1.4%), with Senning survivors showing better functional status overall. (PubMed)
Comparative and pooled analyses similarly suggest that systemic venous pathway obstruction is more frequent after Mustard, while Senning may show a trend toward pulmonary venous pathway obstruction and residual shunts depending on technique and anatomy—reinforcing your operative priority: protect the PV confluence and preserve cross-sectional area on both sides. (PubMed)
4.3 Rhythm complications are not “noise”—they are a dominant late morbidity signal
Late follow-up studies consistently show a substantial burden of rhythm disease:
- Sinus node dysfunction is common (≈47.6% in one cohort) even when overall late mortality and functional class remain favorable. (PubMed)
- Over time, complex transposition carries higher risk for arrhythmias and systemic RV dysfunction, with some series showing markedly reduced long-term sinus rhythm maintenance and increasing RV dysfunction after ~10 years. (PubMed)
- Comparative long-term data also suggest better rhythm-disturbance–free survival after Senning than Mustard in some cohorts, even when other late endpoints are similar. (PubMed)
5) Modern surveillance: a “baffle-first” mindset with advanced imaging
Because a meaningful portion of atrial switch patients develop silent baffle lesions, contemporary follow-up increasingly favors proactive anatomic interrogation, not echo alone. In a modern imaging series, ~33% had baffle leaks/stenoses detected, and TTE missed many that were later found by TEE/CT/CMR/angiography. (PubMed)
Practical, durability-oriented follow-up targets
- Rhythm surveillance: ECG + periodic Holter/event monitoring (symptoms are an unreliable filter). (PubMed)
- Baffle patency: echo as screening, but low threshold for CMR/CT/TEE when gradients, desaturation, device leads, or exercise limitation appear—or even as planned interval imaging in adult congenital practice. (PubMed)
- Systemic RV + TR trajectory: serial assessment and early heart-failure prevention strategies, especially in complex TGA anatomy. (PubMed)
One-line take-home
In Senning, this step succeeds when two wide, growth-tolerant baffles are completed with “space-budget discipline”—never sacrificing pulmonary venous confluence caliber, and never allowing the channels to kink or compress each other.
References
[1] Reddy V, Sharma S, Cobanoglu A. Atrial switch (Senning procedure) in the era of the arterial switch operation: current indications and results. Eur J Cardiothorac Surg. 1996;10(7):546-550. (PubMed)
[2] Roubertie F, Thambo JB, Bretonneau A, Iriart X, Laborde N, Baudet N, Roques X. Late outcome of 132 Senning procedures after 20 years of follow-up. Ann Thorac Surg. 2011;92(6):2206-2213. (PubMed)
[3] Moons P, Gewillig M, Sluysmans T, Verhaaren H, Viart P, Massin M, et al. Long term outcome up to 30 years after the Mustard or Senning operation: a nationwide multicentre study in Belgium. Heart. 2004;90(3):307-313. (PubMed)
[4] Sarkar D, Bull C, Yates R, et al. Comparison of long-term outcomes of atrial repair of simple transposition with implications for a late arterial switch strategy. Circulation. 1999;100(Suppl 2):II-176–II-181. (PubMed)
[5] Khairy P, Landzberg MJ, Lambert J, O’Donnell CP. Long-term outcomes after the atrial switch for surgical correction of transposition: a meta-analysis comparing the Mustard and Senning procedures. Cardiol Young. 2004;14(3):284-292. (PubMed)
[6] Dos L, Teruel L, Ferreira IJ, Rodriguez-Larrea J, Miro L, Girona J, et al. Late outcome of Senning and Mustard procedures for correction of transposition of the great arteries. Heart. 2005;91(5):652-656. (PubMed)
[7] Kirjavainen M, Happonen JM, Louhimo I. Late results of Senning operation. J Thorac Cardiovasc Surg. 1999;117(3):488-495. (PubMed)
[8] Helbing WA, Hansen B, Ottenkamp J, Rohmer J, Chin JG, Brom AG, Quaegebeur JM. Long-term results of atrial correction for transposition of the great arteries. Comparison of Mustard and Senning operations. J Thorac Cardiovasc Surg. 1994;108(2):363-372. (PubMed)
[9] Arthur L, Schoeneberg L, Angtuaco M, Greenberg SB, Renno MS, Das S. Advanced imaging improves detection of baffle leaks and stenoses after atrial switch compared with transthoracic echocardiography. Int J Cardiovasc Imaging. 2021;37(9):2767-2772. (PubMed)