Complete AVSD Repair with Two-Patch Technique #4: VSD Patch Closure

1. Purpose of the Ventricular Patch

In the two-patch repair of complete atrioventricular septal defect (AVSD), the ventricular septal defect (VSD) patch does more than eliminate an interventricular shunt. It reconstructs the ventricular component of the deficient atrioventricular septum, creates the foundation for separation of the common atrioventricular valve into right and left components, and influences both ventricular inflow tracts and the left ventricular outflow tract.

This step must balance four objectives: complete closure of the ventricular communication, preservation of the displaced atrioventricular conduction axis, maintenance of chordal and leaflet mobility, and creation of a stable platform for valve reconstruction. Published descriptions of the two-patch method emphasize the variable three-dimensional anatomy, avoidance of conduction-system injury, and complete closure of the left atrioventricular valve zone of apposition [1,2]. However, the available clinical literature does not validate a universal formula for patch size or prescribe one suture path for every bridging-leaflet and chordal configuration. Patch design remains anatomy driven.

2. Surgical Anatomy Relevant to Patch Closure

2.1 Ventricular Component and Chordal Relationships

The ventricular communication is an inlet defect beneath the common atrioventricular valve. The inlet ventricular septum is characteristically scooped, and the visible crest does not form a uniform muscular rim. Its depth and composition vary from anterior to posterior, as do its relationships to the superior and inferior bridging leaflets, chordae, and conduction axis.

The bridging leaflets may span the septum to different degrees. Chordae may insert into the crest, papillary muscles, ventricular free wall, or cross the intended patch plane. These structures must be identified before suturing because an apparently satisfactory patch position can still tether a leaflet, trap a chord, narrow an inflow, or distort coaptation after tying.

The defect should therefore be assessed as a three-dimensional space. The surgeon must determine where the patch can lie without impinging on the left ventricular outflow tract, how it will pass relative to the chordae, and where its superior edge should meet the common atrioventricular valve.

2.2 Displaced Conduction Axis

In complete AVSD, the atrioventricular node is displaced inferiorly and posteriorly. The penetrating conduction axis then courses close to the inferior and posteroinferior margin of the ventricular component. This region is vulnerable to direct needle injury, incorporation within a suture, compression, hematoma, or traction after tying.

Conduction protection depends on location, depth, and tissue selection. The inferior suture line is placed slightly toward the right ventricular side, bites are kept controlled rather than unnecessarily deep, and the highest-risk segment near the atrioventricular node can be bridged through right atrioventricular valve tissue instead of the inferior septal crest. Avoidance of conduction-system damage is a central principle of the two-patch technique [1,2].

3. Pre-Suture Assessment

Before fashioning the patch, the surgeon should define the full circumference of the defect and inspect the valve and subvalvar apparatus. The assessment should include the anterior and posterior limits of the VSD, the depth and quality of the septal crest, the anticipated conduction-axis course, chordae entering or crossing the defect, and the amount of right atrioventricular valve tissue available near the conduction-risk zone.

The proposed relationship between the patch and the bridging leaflets should also be established. The surgeon should anticipate the effect of the patch on left ventricular inflow and outflow and define the level at which the bridging leaflets will be attached to its superior edge.

Saline testing before patch placement helps establish the native coaptation pattern and the likely division between the future right and left atrioventricular valves. It should be repeated after ventricular closure because patch size and orientation can change leaflet tension and annular geometry.

A chord crossing the intended patch plane should not be displaced automatically. Its origin, insertion, and functional contribution should be defined. The patch may need to pass to one side of the chord or be contoured around it. Functional chordae should not be incorporated into the suture line or stretched by an oversized patch.

4. Patch Design and Sizing

The ventricular patch is usually curved or crescentic so that it follows the scooped septum and reaches the undersurface of the common atrioventricular valve without redundant material. It should be pliable enough to conform to the septal contour but stable enough to maintain geometry and hold sutures securely.

A practical operative principle is to fashion the patch slightly smaller rather than excessively large in both dimensions. In the illustrated technique, the anterior–posterior dimension is approximately 80% of the measured span. This is an operative heuristic, not a universally validated evidence-based ratio. Final dimensions must be individualized according to VSD depth, leaflet position, chordal arrangement, ventricular size, and available tissue.

An oversized patch may stretch or displace chordae, tent the bridging leaflets, distort the reconstructed annulus, impair coaptation, narrow a ventricular inlet, or protrude into the left ventricular outflow tract. Redundant material may also fold beneath the valve. Conversely, excessive undersizing may create tension, pull the septal crest toward the valve, or distort the leaflets. “Slightly smaller” therefore means eliminating redundancy while preserving a tension-free reach.

Before implantation, the patch should be placed temporarily over the defect. It should cover the communication, lie smoothly, preserve chordal mobility, allow the bridging leaflets to return to the intended position, and avoid excessive projection into either ventricle.

5. Placement of the Ventricular Suture Line

5.1 General Principles

The patch must be secured with bites adequate for hemostasis and resistance to tearing but no deeper than necessary. Deep bites do not necessarily strengthen the repair and may increase the risk of conduction injury or chordal entrapment.

Interrupted pledgeted sutures, a running suture, or a combined approach may be used according to tissue quality and surgeon preference. Each bite should be placed under direct visualization, with progressive advancement of the patch so that the septal margin and nearby chordae remain visible.

5.2 Anterior and Superior Margins

Along the anterior and superior margins, the patch should follow the natural ventricular septal plane. Excessive leftward projection may narrow the intrinsically elongated left ventricular outflow tract associated with AVSD. The relationship between the patch, superior bridging leaflet, and subaortic region should be reassessed before final tying.

Chordal attachments near the superior margin should be identified individually. Sutures should pass around rather than through functional chordae. When a chord crosses the patch plane, placement on the right or left side should be determined by its leaflet insertion and effect on valve motion.

5.3 Inferior Margin

The inferior suture line is placed slightly toward the right ventricular side of the visible VSD margin. This increases separation from the conduction axis while allowing the patch to cover the communication. The line must not be shifted so far rightward that a residual channel remains beneath the patch.

Bites should remain relatively superficial, and the needle trajectory should be directed away from the anticipated conduction tissue. Near the atrioventricular node, the closure can transition from the septal surface to right atrioventricular valve tissue. This bridges the vulnerable area and avoids deep suturing into the inferior septal crest.

The valve-tissue bite must be strong enough to support the patch but should avoid the coaptation surface and should not restrict leaflet motion. Incorporation of left-sided valve tissue may produce tethering, regurgitation, or stenosis.

6. Leaflet-to-Patch Reconstruction

After the patch has been secured to the ventricular margins, its superior edge becomes the foundation for separation of the common atrioventricular valve. The bridging leaflets are attached at the predetermined level, creating distinct right and left valve components.

The superior patch position should reproduce the intended annular and coaptation geometry without pulling either valve excessively toward the septum. Before tying, the surgeon should confirm that no chord has been trapped, the patch is not folded, the inferior closure is complete, and the rightward conduction-sparing course has been maintained.

Complete closure of the left atrioventricular valve zone of apposition is commonly incorporated into contemporary two-patch repair. Long-term series associate two-patch reconstruction with complete closure and favorable durability [3], and a large historical cohort identified cleft closure as an independent predictor of survival [4]. Closure must nevertheless be balanced against stenosis when leaflet tissue is limited or the mural leaflet is hypoplastic.

7. Intraoperative Assessment

After ventricular closure and valve reconstruction, saline testing should evaluate leaflet mobility, coaptation, residual leakage, chordal restriction, and narrowing of either ventricular inlet. Particular attention should be paid to the left atrioventricular valve because postoperative regurgitation is a major driver of reoperation.

After separation from cardiopulmonary bypass, transesophageal or epicardial echocardiography should assess residual VSD flow, left and right atrioventricular valve regurgitation or stenosis, left ventricular outflow tract obstruction, biventricular function, and rhythm. Moderate or greater left atrioventricular valve regurgitation at discharge has been associated with a markedly increased risk of later reoperation [5].

A residual jet should be localized precisely. Potential sites include the inferior patch margin, a chordal passage point, the leaflet-to-patch junction, or a muscular recess not incorporated in the original suture line.

8. Principal Failure Modes

8.1 Conduction Disturbance

Heart block may result from deep inferior sutures, failure to shift the line rightward, direct suturing near the displaced node, compression during tying, or postoperative edema. Injury may be immediate or delayed. In a cohort of 363 repairs, 10-year freedom from permanent pacemaker insertion was 98% [4].

8.2 Residual VSD

Residual shunting may follow incomplete incorporation of the inferior margin, tissue tearing, patch folding, widely spaced sutures, or excessive rightward displacement. Ten-year freedom from reoperation for residual VSD was 97% in the same cohort [4].

8.3 Atrioventricular Valve Dysfunction

Regurgitation can result from patch oversizing, chordal entrapment, leaflet tethering, annular distortion, or an incorrectly positioned leaflet-to-patch junction. Stenosis may result from excessive reduction of the effective annular area or overly aggressive closure of the zone of apposition.

In a 100-patient two-patch series with complete cleft closure, freedom from reoperation for left atrioventricular valve dysfunction was 94% at 10 years [3]. A 222-patient series reported reoperation in 10%, including procedures for valve dysfunction, residual VSD, subaortic stenosis, and pacemaker implantation [6].

8.4 Left Ventricular Outflow Tract Obstruction

An excessively bulky or leftward-projecting patch may worsen the elongated outflow geometry of AVSD. In the 100-patient long-term series, freedom from reoperation for left ventricular outflow tract obstruction was 99% at 10 years [3].

9. Evidence and Clinical Interpretation

Clinical outcome data support the two-patch technique as a durable and reproducible repair. Bakhtiary and colleagues reported no perioperative, in-hospital, or late deaths among 100 consecutive patients, with 94% freedom from left atrioventricular valve reoperation and 99% freedom from left ventricular outflow tract reoperation at 10 years [3]. Litwin and colleagues reported 2.7% early mortality and a 10% reoperation rate in 222 patients [6]. Najm and colleagues reported 83% 10-year survival and high freedom from reoperation for residual VSD, subaortic stenosis, and permanent pacemaker insertion in 363 patients [4].

These results support the overall strategy but do not prove that one exact patch dimension or suture offset is appropriate for all patients. Comparative evidence is affected by anatomical selection. A meta-analysis of 15 publications involving 1,034 patients found broadly comparable postoperative outcomes between modified single-patch and two-patch repair, but the modified single-patch technique was used in patients with significantly smaller VSDs [7]. Apparent equivalence between techniques should therefore not be interpreted independently of VSD depth, bridging-leaflet morphology, and chordal anatomy.

Successful VSD patch closure depends on precise anatomical interpretation. The patch should be large enough to close the defect without tension, small enough to avoid redundancy and distortion, positioned to preserve inflow and outflow geometry, and sutured along a rightward, controlled inferior course that protects the displaced conduction axis.

10. Key Operative Principles

• Define the entire ventricular defect before placing sutures.
• Identify all functionally important chordal attachments.
• Fashion the patch slightly smaller rather than excessively large.
• Treat the approximately 80% anterior–posterior dimension as an operative guide, not a universal rule.
• Avoid redundant material beneath the common atrioventricular valve.
• Keep inferior bites controlled and no deeper than necessary.
• Shift the inferior suture line slightly toward the right ventricular side.
• Near the atrioventricular node, use right atrioventricular valve tissue rather than deep septal bites.
• Preserve chordal mobility and bridging-leaflet geometry.
• Reassess residual shunting, valve competence, ventricular inflow, left ventricular outflow, and atrioventricular conduction before completing the operation.

References

[1] Daebritz S. Correction of complete atrioventricular septal defects with two patch technique. Oper Tech Thorac Cardiovasc Surg. 2004. doi:10.1053/j.optechstcvs.2004.07.002.

[2] Mavroudis C, Backer CL. The two-patch technique for complete atrioventricular canal. Semin Thorac Cardiovasc Surg. 1997.

[3] Bakhtiary F, Takács J, Cho MY, Rázek V, Dähnert I, Doenst T, Walther T, Borger MA, Mohr FW, Kostelka M. Long-term results after repair of complete atrioventricular septal defect with two-patch technique. Ann Thorac Surg. 2010. doi:10.1016/j.athoracsur.2009.11.017.

[4] Najm HK, Coles JG, Endo M, Stephens D, Rebeyka IM, Williams WG, Freedom RM. Complete atrioventricular septal defects: results of repair, risk factors, and freedom from reoperation. Circulation. 1997.

[5] Xie O, Brizard CP, d’Udekem Y, Galati JC, Kelly A, Yong MS, Weintraub RG, Konstantinov IE. Outcomes of repair of complete atrioventricular septal defect in the current era. Eur J Cardiothorac Surg. 2014. doi:10.1093/ejcts/ezt444.

[6] Litwin SB, Tweddell JS, Mitchell ME, Mussatto KA. The double patch repair for complete atrioventricularis communis. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 2007. doi:10.1053/j.pcsu.2007.01.003.

[7] Li D, Fan Q, Iwase T, Hirata Y, An Q. Modified single-patch technique versus two-patch technique for the repair of complete atrioventricular septal defect: a meta-analysis. Pediatr Cardiol. 2017. doi:10.1007/s00246-017-1684-8.