Tetralogy of Fallot (TOF) — #4 VSD Patch Closure
The operative objective (what the patch is really doing)
In classic TOF, the VSD is typically large and nonrestrictive. The patch is not simply “closing a hole”; it is reconstructing LV outflow continuity and separating streaming—LV → aorta from RV → PA—while deliberately protecting two structures that sit uncomfortably close to the work:
- Aortic valve (often adjacent to the superior VSD rim)
- Conduction system (especially near the postero-inferior margin and along the RV septal surface course of the RBB)
A durable repair is achieved when the patch sits on true muscular purchase, respects the aortic annulus/cusps, and avoids the RBB danger zone near the medial papillary muscle and septomarginal trabeculation (SMT). Technique refinements can meaningfully reduce postoperative RBBB and conduction injury when the closure is planned as an anatomic reconstruction rather than a defect “seal.” [1]
1) Landmark-first mental map (before placing any stitch)
A. Identify the “aortic cliff” (superior rim)
Aortic override makes the superior VSD margin feel like a steep “drop” toward the aortic annulus. Practically, the “top edge” can be deceptively close to an aortic cusp—especially when exposure is limited or the valve is moving.
Pearl
If the border is ambiguous, re-dose cardioplegia (when appropriate) to quiet the valve and improve definition of the rim—because “suturing blind” near a cusp is a preventable complication. This philosophy aligns with modern “teach-the-map-first” approaches to septal defect closure. [3]
B. Find the RV septal surface danger zone (RBB)
In TOF, the right bundle branch is encountered on the RV septal surface, closely related to the SMT / moderator band complex. A highly practical anatomic datapoint is that the RBB course is approximately ~2 mm anterior to the medial papillary muscle in many hearts—making the base of the medial papillary muscle a legitimate “think twice / no-suture” region unless anatomy and purchase are unequivocally safe. [2]
Actionable translation
- Treat the base of the medial papillary muscle as an “RBB-adjacent zone” rather than a convenient anchor point. [2]
- If the posterior limb of the SMT is hypertrophied and extends inferiorly, assume conduction is closer than it looks and prioritize disciplined bite placement over “tightening” the inferior edge.
2) Exposure strategy — “see the rim, then close the rim”
A. Tricuspid valve detachment (when exposure limits precision)
When the anterior/septal tricuspid leaflet obscures the VSD, temporary leaflet detachment can convert a high-risk closure into a precise, anatomic one—specifically by allowing direct visualization of:
- The superior rim (aortic valve proximity)
- The postero-inferior rim (AV conduction axis territory)
Evidence from clinical series supports that TV detachment can improve visualization and may reduce residual VSD/AV block in anatomically “tight” repairs, while careful reattachment preserves valve function on follow-up. [4,5]
Technical essentials (repair-minded)
- Detach along a clean, reconstructable line (planned for a tension-free reattachment).
- Reattach with fine, evenly spaced sutures to avoid leaflet distortion and late TR.
- Confirm coaptation by direct inspection and intraoperative echo.
3) Patch closure principles (what you are truly building)
A. Patch purpose: LVOT continuity
The patch should create a smooth LV-to-aorta pathway. Because TOF is a conotruncal malalignment geometry problem, patch shape and orientation matter—avoid “tenting” into the LVOT or pulling the superior rim toward the aortic valve. [3]
B. Suture strategy: secure purchase without distortion
Aim for muscular purchase with a closure that is stable yet non-distorting:
- Avoid traction that tethers an aortic cusp superiorly.
- Avoid bites that distort the tricuspid apparatus on the RV side.
- Do not “earn security” by going deep in the wrong place—depth is not safety if it violates conduction anatomy.
Classic surgical anatomy work emphasizes that iatrogenic complete heart block still occurs when the conduction axis location is underappreciated in specific anatomic circumstances—reinforcing that “anatomic humility” must be built into the stitch plan. [6]
C. Respect rim quality: muscular vs fibrous
- A muscular postero-inferior rim is often more forgiving for suture purchase.
- A thin/fibrous margin (or membranous components) demands a more conservative bite strategy, because “secure” can quickly become “injurious” if the closure drifts into conduction territory. [6]
4) Conduction protection: two practical danger zones
Zone 1 — Postero-inferior rim (AV conduction axis territory)
Even with anatomic variability, the postero-inferior region remains a universal “think twice” border.
Practical strategy
- Prefer controlled, conservative bites where tissue is thin.
- Avoid aggressive deep anchoring when the rim is uncertain.
Zone 2 — Medial papillary muscle / SMT complex (RBB territory)
Your slide’s message is surgically decisive: the RBB is functionally “in the neighborhood” of the medial papillary muscle/SMT complex; closure choices here should be made as if conduction were closer than expected. [2]
Technique-level evidence (TOF-specific)
In outlet-type VSD closure in TOF, a continuous suturing strategy has been associated with reduced postoperative RBBB and more favorable conduction parameters compared with interrupted closure in one surgical series—supporting the concept that how the patch is seated can influence conduction outcomes, not just where. [8]
5) Reality check: incidence of AV block (and why vigilance still matters)
Even in routine congenital repairs, clinically significant AV block is uncommon but real. In a large series of VSD/AV canal/TOF repairs, early AV block requiring pacemaker occurred in 0.9%, and delayed AV block occurred in 0.3–0.7%—with transient early block acting as a potential risk marker for later events. [7] For VSD closure specifically, institutional experience still places the risk of iatrogenic complete heart block at <1% in modern eras, but not at zero. [6]
Why RBBB deserves respect (long view)
Long-term follow-up data show that postoperative conduction disturbances—particularly RBBB with ventricular ectopy—can correlate with late risk, reinforcing the importance of (1) avoiding injury when possible and (2) committing to lifelong rhythm surveillance when conduction abnormalities occur. [9]
6) Intraoperative “prevent late regret” checklist (high-yield)
After patch closure (and TV reattachment if performed), confirm:
- Aortic valve
- Leaflet motion, no cusp tethering, competence on echo
- Tricuspid valve
- Coaptation line, no distortion, TR grade acceptable
- Residual VSD
- Direct inspection + TEE interrogation
- Rhythm / conduction
- New bundle branch patterns, AV block signals, pacing threshold readiness if needed
7) Where VSD closure fits in modern TOF outcomes
Contemporary TOF repair achieves low mortality, but the long-term course is defined by lifelong follow-up and meaningful reintervention burden—with meta-analytic data suggesting reintervention rates on the order of ~2.26% per year across cohorts. [10] Postoperative management frameworks emphasize systematic surveillance for arrhythmias, RV dysfunction, and residual lesions—making a clean VSD reconstruction the foundation that keeps the physiology coherent for decades. [11]
References
[1] Hazan E, Bical O, Bex JP, Dubuis C, Lecompte Y, De Riberolles C, Neveux JY. Is right bundle branch block aviodable in surgical correction of tetralogy of Fallot? Circulation. 1980;62(4):852-854. doi:10.1161/01.cir.62.4.852. (PubMed)
[2] Yoneyama F, Kato H, Abe M, Hiramatsu Y, et al. The right bundle branch in ventricular septal defects. Eur J Cardiothorac Surg. 2025;67(5):ezaf105. doi:10.1093/ejcts/ezaf105. (PubMed)
[3] Manning PB. Ventricular Septal Defect Closure: How I Teach It. Ann Thorac Surg. 2018;106(2):324-326. doi:10.1016/j.athoracsur.2018.05.042. (PubMed)
[4] Sasson L, Katz MG, Ezri T, Tamir A, Herman A, Bove EL, Schachner A. Indications for tricuspid valve detachment in closure of ventricular septal defect in children. Ann Thorac Surg. 2006;82(3):958-963. doi:10.1016/j.athoracsur.2006.03.094. (PubMed)
[5] Fraser CD 3rd, Zhou X, Palepu S, Lui C, Suarez-Pierre A, Crawford TC, Magruder JT, Jacobs ML, Cameron DE, Hibino N, Vricella LA. Tricuspid Valve Detachment in Ventricular Septal Defect Closure Does Not Impact Valve Function. Ann Thorac Surg. 2018;106(1):145-150. doi:10.1016/j.athoracsur.2018.02.075. (PubMed)
[6] Andersen HØ, de Leval MR, Tsang VT, Elliott MJ, Anderson RH, Cook AC. Is complete heart block after surgical closure of ventricular septum defects still an issue? Ann Thorac Surg. 2006;82(3):948-956. doi:10.1016/j.athoracsur.2006.04.030. (PubMed)
[7] Lin A, Mahle WT, Frias PA, Fischbach PS, Kogon BE, Kanter KR, Kirshbom PM. Early and delayed atrioventricular conduction block after routine surgery for congenital heart disease. J Thorac Cardiovasc Surg. 2010;140(1):158-160. doi:10.1016/j.jtcvs.2009.12.050. (PubMed)
[8] Yoneyama F, Kato H, Matsubara M, Mathis BJ, Yoshimura Y, Abe M, Suetsugu F, Maruo K, Suzuki Y, Hiramatsu Y. Conduction disorders after perimembranous ventricular septal defect closure: continuous versus interrupted suturing techniques. Eur J Cardiothorac Surg. 2022;62(1):ezab407. doi:10.1093/ejcts/ezab407. (PubMed)
[9] Quattlebaum TG, Varghese J, Neill CA, Donahoo JS. Sudden death among postoperative patients with tetralogy of Fallot: a follow-up study of 243 patients for an average of twelve years. Circulation. 1976;54(2):289-293. doi:10.1161/01.cir.54.2.289. (PubMed)
[10] Romeo JLR, Etnel JRG, Takkenberg JJM, Roos-Hesselink JW, Helbing WA, van de Woestijne P, Bogers AJJC, Mokhles MM. Outcome after surgical repair of tetralogy of Fallot: A systematic review and meta-analysis. J Thorac Cardiovasc Surg. 2020;159(1):220-236.e8. doi:10.1016/j.jtcvs.2019.08.127. (PubMed)
[11] Forman J, Beech R, Slugantz L, Donnellan A. A Review of Tetralogy of Fallot and Postoperative Management. Crit Care Nurs Clin North Am. 2019;31(3):315-328. doi:10.1016/j.cnc.2019.05.003. (PubMed)