Complete AVSD Repair with Two-Patch Technique #5–7: Valve Reconstruction and Atrial Septation

1. Introduction

Complete atrioventricular septal defect (AVSD) repair is a reconstruction of the common atrioventricular junction, not merely closure of an atrial septal defect (ASD) and a ventricular septal defect (VSD). The surgeon must establish separate ventricular and atrial chambers while creating two competent, adequately sized atrioventricular valves. These objectives are interdependent: the position of the VSD patch determines the valve partition, the leaflet reconstruction determines left atrioventricular valve (LAVV) competence, and the atrial patch must complete septation without injuring the displaced conduction system [1].

This chapter addresses the final three illustrated steps of a two-patch repair: attachment of the VSD patch to the common valve and ASD patch (#5), closure of the LAVV zone of apposition (#6), and completion of primum ASD closure (#7). The drawings illustrate one reproducible sequence; leaflet division, patch materials, and precise suture placement vary with anatomy and surgical preference [2].

2. Surgical Relationships That Determine the Repair

2.1. Common valve and functional partition

The common atrioventricular valve has five principal leaflets, including superior and inferior bridging leaflets spanning the ventricular septum. During biventricular repair, their left-sided portions become important components of the reconstructed LAVV. The intended partition must therefore follow the morphology of the leaflets and their chordal support, rather than an arbitrary midpoint across the common annulus [1].

Before final fixation, the surgeon should determine whether the proposed LAVV has sufficient opening area, leaflet mobility, and coaptation length. A partition positioned excessively toward the left ventricle may produce stenosis; one positioned too far to the right may leave insufficient coaptation or compromise the right atrioventricular valve. Abnormal chordal insertion, a small left mural leaflet, or a double-orifice LAVV may further constrain reconstruction.

2.2. Three levels of the two-patch repair

The VSD patch establishes the ventricular septal plane beneath the bridging leaflets. The common valve tissue forms the intervening functional valve partition. The ASD patch completes atrial septation above the valve. In the illustrated technique, these three elements are joined by interrupted sutures passed sequentially through the VSD patch, common leaflet tissue, and ASD patch.

This patch–leaflet–patch relationship is the central geometric concept. The two patches should meet the leaflet at an appropriate height without folding, shortening, or tethering the tissue. The final construction must preserve valve opening, avoid residual shunting at the patch junction, and maintain an unobstructed left ventricular outflow tract (LVOT). Published two-patch variations may divide or preserve bridging-leaflet continuity; the illustrated sandwich should not be interpreted as mandatory for every complete AVSD [2,3].

3. Step #5: VSD Patch–Leaflet–ASD Patch Suture Sequence

3.1. Preparing the ventricular patch and leaflet interface

Following cardioplegic arrest, right atriotomy, inspection of the common valve, and placement of the VSD patch along the ventricular septal crest, attention turns to securing the bridging leaflets at the intended partition. The surgeon should verify that the patch reaches the leaflet tissue without excessive tension or redundant material. Its upper margin should support the reconstructed valve while avoiding protrusion into the LVOT or distortion of subvalvar attachments.

The illustration shows multiple interrupted sutures distributed across the proposed line of valve partition. Each suture passes from the superior aspect of the VSD patch through the appropriately selected bridging-leaflet tissue. The valve should be held in its physiologic configuration while these bites are placed. Broad, symmetric tissue purchase reduces the risk of a focal tear, whereas excessively deep or malpositioned bites may restrict leaflet excursion.

3.2. Adding the ASD patch: the sandwich construction

After traversing the bridging leaflet, the same sutures are passed through the inferior margin of the primum ASD patch. The resulting sequence is:

1. VSD patch: anchor the stitch to the ventricular septal reconstruction.
2. Bridging leaflet: incorporate sufficient leaflet tissue at the planned division between right and left valve components.
3. ASD patch: pass the stitch through the atrial patch margin and secure the three layers together.

Sutures may be placed sequentially and organized before final tying. They should be tightened under direct vision, with repeated assessment of the intended LAVV orifice. Excessive traction can plicate the bridging leaflets, reduce coaptation height, alter chordal geometry, or generate LAVV stenosis. Conversely, inadequate fixation may leave a residual communication adjacent to the valve or permit separation of the patch–leaflet junction.

The objective is stable septation without sacrificing leaflet mobility. The repair should be inspected from the atrial side to ensure that neither the left nor the right valve has acquired an unfavorable contour. A saline test is useful, but static competence alone does not establish that a valve will be nonstenotic under physiologic loading.

3.3. Protecting the conduction axis

In AVSD, the atrioventricular node is displaced posteroinferiorly relative to its usual position in the triangle of Koch. The penetrating bundle courses near the inferior bridging leaflet and the posteroinferior aspect of the ventricular septal defect. Deep sutures in this region may injure the conduction system; its course cannot be reliably inferred from an ordinary-heart diagram [1,4].

The ventricular patch and leaflet junction must therefore be approached with particular restraint near the inferior septal margin. Suture depth and direction are modified according to the exposed anatomy, with superficial endocardial or leaflet-related bites where necessary. This principle becomes especially important during subsequent atrial patch closure near the crux.

4. Step #6: Closure of the Left Atrioventricular Valve Zone of Apposition

4.1. Morphology and rationale

The apparent LAVV “cleft” in AVSD represents a zone of apposition between the left-sided portions of the superior and inferior bridging leaflets, rather than a conventional cleft through an otherwise normal mitral leaflet. After partitioning the common valve, this interface may remain a major source of regurgitation.

The supplied illustration depicts a series of interrupted sutures placed along the zone of apposition, advancing toward the primary chordal attachments. The intent is to create a broad and stable coaptation surface while preserving the mobility and effective opening area of both bridging-leaflet components.

4.2. Suture placement and functional assessment

Closure is usually performed with fine interrupted sutures, beginning at the base of the zone and proceeding toward its distal extent as anatomy permits. Each stitch should approximate corresponding leaflet edges without rolling, everting, or shortening them. Sutures should not transfix nearby primary chordae or capture leaflet tissue in a manner that restricts opening.

The surgeon should repeatedly inspect the relationship of the repaired leaflet edges to the anterior and posterior papillary muscles and their chordal insertions. The last few stitches can produce disproportionate narrowing when the mural leaflet is small or the valve orifice is intrinsically restrictive.

Complete closure is not an absolute goal at the expense of valve area. A residual distal opening or partial closure may be reasonable when complete approximation would create stenosis, significant leaflet tension, or chordal restriction. Observational studies support individualized management: a propensity-matched cohort found similar freedom from reoperation after complete AVSD repair with or without cleft closure, although confounding and anatomic selection remain important limitations [5].

4.3. Testing the reconstructed valve

Saline injection into the left ventricle, performed through the left-sided valve under direct vision, helps identify a central gap, residual regurgitation through the zone of apposition, restricted leaflet movement, or an eccentric coaptation line. Additional sutures should address a demonstrable mechanism rather than simply eliminate every visible opening.

Orifice sizing with an appropriately selected Hegar dilator may help identify gross restriction, but there is no universally applicable dilator threshold independent of age, body size, and valve morphology. Final interpretation requires both anatomic assessment and post-bypass Doppler evaluation. A satisfactory saline test cannot exclude a residual gradient or regurgitation arising under physiologic pressure.

5. Step #7: Primum ASD Patch Closure

5.1. Atrial patch orientation

After valve reconstruction, the primum ASD patch is positioned to restore the atrial septal plane. The inferior portion has already been incorporated into the patch–leaflet–patch junction. The remaining patch must cover the atrial communication without distorting the reconstructed LAVV or obstructing adjacent atrial inflow.

The most technically sensitive region lies along the posteroinferior margin adjacent to the displaced atrioventricular node. The schematic shows the suture line following the left atrioventricular valve attachment region, then transitioning onto the left atrial wall before joining the native ASD margin. This route is a conduction-sparing option, not a fixed trajectory applicable to every specimen.

5.2. Conduction-sparing suture trajectory

At the junction of the bridging leaflets and the posteroinferior atrial septum, a deep annular or septal bite can place the conduction axis at risk. A described alternative positions the patch suture line above the left inferior leaflet attachment and on atrial tissue, keeping it away from the vulnerable nodal region. Aeba and colleagues reported their experience with such a modified interatrial suture line, while Koshiyama and colleagues described a superficial endocardial technique near the node [6,7].

In practice, the surgeon should identify the inferior bridging leaflet, atrial wall, coronary sinus region, and anticipated course of the conduction axis before committing to each bite. Preservation of conduction requires a deliberate change in tissue plane, not simply a smaller stitch in an otherwise hazardous location. The patch must still be securely anchored, without leaving a residual inferior atrial communication.

The suture line is then continued around the remaining native ASD rim. Patch geometry should avoid unnecessary tension, redundancy across the valve, or narrowing of pulmonary venous inflow. Before the final closure, careful deairing and inspection of the right and left atrial sides are appropriate. Any fenestration, if deliberately created, should be explicitly distinguished from an unintended residual ASD.

6. Intraoperative Completion Assessment

The repair should be evaluated as a single integrated reconstruction rather than as three independently closed structures. After removal of the cross-clamp and separation from cardiopulmonary bypass, transesophageal or epicardial echocardiography should assess:

• LAVV: degree, location, and mechanism of regurgitation; leaflet coaptation and mobility; mean inflow gradient interpreted in relation to heart rate and cardiac output.
• Right atrioventricular valve: residual regurgitation, stenosis, and leaflet distortion.
• Septation: residual VSD or ASD, particularly along the leaflet–patch junction and posteroinferior patch margins.
• LVOT: subaortic flow acceleration, patch protrusion, or chordal obstruction; associated ventricular function.
• Conduction and global physiology: atrioventricular synchrony, ventricular performance, pulmonary pressures, and adequacy of systemic output.

A significant residual LAVV regurgitant jet originating from an identifiable repairable defect, important valve restriction, hemodynamically relevant residual shunt, or newly created LVOT obstruction should prompt consideration of revision before leaving the operating room. The decision must integrate the magnitude and mechanism of the lesion with the risks of additional bypass and the individual patient's physiology.

7. Technical Alternatives and Evidence

A two-patch repair provides independent ventricular and atrial septal reconstruction, but it is not the only established approach. Conventional single-patch and modified single-patch techniques use different methods for dealing with the ventricular component and common valve. Technique selection depends on VSD depth, bridging-leaflet morphology, chordal attachments, ventricular balance, and the surgeon's experience.

Comparative studies, including a small retrospective two-patch versus modified single-patch series, have not consistently demonstrated superior valve outcomes for one approach. Shorter ischemic and bypass times have been reported with modified single-patch repair in selected patients, but selection bias and variation in anatomy limit broad claims of equivalence [8]. The clinically meaningful endpoint is not the number of patches; it is an unobstructed, competent and durable reconstruction.

8. Postoperative Physiology and Long-Term Surveillance

Early management should emphasize adequate cardiac output, atrioventricular synchrony, pulmonary vascular resistance, ventricular loading, and identification of residual lesions. Pulmonary hypertensive physiology, atrioventricular valve regurgitation, ventricular dysfunction, and complete heart block may each markedly impair recovery.

In a Society of Thoracic Surgeons cohort of 2,399 complete AVSD repairs performed from 2008 through 2011, hospital mortality was 3.0%, and permanent pacemaker implantation occurred in 2.7%. These historical registry results describe population-level risk, not an expected outcome for every present-day center [9].

Long-term durability is principally limited by LAVV dysfunction, with additional concerns including LVOT obstruction, residual or recurrent shunts, and conduction abnormalities. An Australian four-center cohort of 829 patients reported freedom from reoperation of 82.7% at 10 years. Moderate postoperative LAVV regurgitation was an independent predictor of later reoperation [10].

The mechanism and trajectory of regurgitation matter. A recent single-center analysis found that moderate postoperative LAVV regurgitation can improve or remain stable, whereas regurgitation centered on the repaired zone of apposition was associated with greater risk of deterioration and reoperation [11]. Surveillance should therefore include serial echocardiographic assessment of regurgitation location, valve gradients, ventricular dimensions, LVOT flow, and clinical status. When recurrent regurgitation requires surgery, reparative strategies are generally preferred when feasible, because valve replacement in children introduces prosthesis-related and growth-related burdens [12].

9. Key Surgical Principles

• Treat the two patches and common valve as one reconstruction. The patch–leaflet–patch interface must be secure without tethering valve tissue.
• Preserve a generous left-sided valve orifice. Partition and zone-of-apposition closure must not create stenosis.
• Use selective cleft closure. Optimize coaptation while respecting chordae, papillary muscles, and leaflet mobility.
• Protect the posteroinferior conduction axis. Change the suture plane near the displaced node rather than relying on arbitrary distances.
• Follow the atrial anatomy. The ASD patch should achieve complete septation without distorting the valve or obstructing atrial inflow.
• Interrogate the entire repair before completion. Residual valve dysfunction, shunting, LVOT obstruction, or heart block may require immediate correction or a tailored management strategy.

References

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