Complete AVSD Repair with Two-Patch Technique #5: Suture Sequence—VSD Patch → Leaflet → ASD Patch

1. Overview

In two-patch repair of complete atrioventricular septal defect (AVSD), the ventricular and atrial components are closed with separate patches, and the common atrioventricular (AV) valve leaflet tissue is incorporated between them. The operative sequence is VSD patch → common AV valve leaflet → ASD patch. When the sutures are tied, the leaflet tissue is secured within a patch–leaflet–patch sandwich that completes septation and establishes the reconstructed AV junction.

This is not simply a connection between three layers. It determines the height and orientation of the reconstructed septal leaflet attachment, the distribution of bridging leaflet tissue between the right and left AV valve orifices, and the relationship of the valve to the left ventricular outflow tract (LVOT). The objectives are simultaneous: complete septation, preserved leaflet mobility, a competent and nonstenotic left AV valve, an adequate right AV valve orifice, and avoidance of LVOT distortion.

The available evidence does not define a universally optimal numerical patch height or suture depth. One study found no statistically significant association between the native ventricular septal defect height measured by two-dimensional echocardiography and reoperation after complete AVSD repair [1]. This finding concerns the anatomic height of the ventricular septal deficiency, not the surgically selected height of the VSD patch. It therefore should not be interpreted as evidence that patch sizing and leaflet attachment are unimportant. Outcome data instead emphasize intrinsic valvar and subvalvar anatomy and the postoperative valve result.

2. Anatomic Basis of the Reconstruction

Complete AVSD is characterized by a common AV junction, a primum atrial septal defect, an inlet ventricular septal defect, and a common AV valve with superior and inferior bridging components. Because there is no normal central fibrous plane separating the right and left AV valve annuli, the surgeon must create that plane during repair.

The VSD patch restores the ventricular septal component. The common AV valve leaflet is attached to its superior edge, and the inferior edge of the ASD patch is secured on the atrial side. The captured leaflet tissue becomes the reconstructed septal attachment of the divided right and left AV valves.

The optimal attachment line is determined by functional anatomy rather than a fixed geometric rule. Important variables include VSD depth, Rastelli morphology, ventricular balance, left mural leaflet size, papillary muscle position, chordal anatomy, double-orifice morphology, zone-of-apposition symmetry, LVOT relationships, and the displaced conduction axis.

Four morphologic patterns have been associated with a markedly increased incidence of postoperative moderate-or-greater left AV valve regurgitation or stenosis after two-patch repair: abnormal papillary muscles, dense superior bridging-leaflet chordal insertions, double-orifice left AV valve, and major disparity in the lengths of the zone-of-apposition margins [2]. These abnormalities may interfere with VSD patch positioning, leaflet approximation, or preservation of an adequate valve orifice. More recent long-term data identify subvalvar malformations—particularly short chordae and hypoplastic inferior bridging-leaflet tissue—as major risk factors for reoperation, especially when stenosis is the dominant mechanism [3].

3. Step 1: VSD Patch Sizing and Positioning

The VSD patch is first secured to the ventricular septal crest using a conduction-sparing suture line. Its superior edge remains available for attachment to the common AV valve leaflets.

The patch should close the ventricular component without traction but should not be redundant. An undersized patch can pull the bridging leaflets toward the septum, reduce effective leaflet height, restrict excursion, and narrow the left AV valve orifice. An oversized patch can bulge into the ventricle, disturb chordal relationships, or alter LVOT geometry.

Patch height should be assessed dynamically by bringing the bridging leaflet tissue toward the proposed superior patch margin before placing the leaflet sutures. The leaflet should reach the patch without forceful inferior displacement or excessive atrial redundancy. The goal is to restore the missing septal plane while preserving leaflet mobility.

The study evaluating native VSD height found a hazard ratio of 0.95 for reoperation, without a statistically significant correlation [1]. This suggests that the depth of the ventricular scoop alone does not determine outcome. It does not negate individualized patch geometry. The same nominal patch height may be well tolerated in one patient and restrictive in another with short chordae, an abnormal papillary muscle, or a small mural leaflet.

The inferior patch attachment must also respect the displaced conduction axis. The VSD patch should be secure and hemostatic before the leaflet is incorporated; the patch–leaflet suture line should not compensate for inadequate ventricular septal closure.

4. Step 2: Passing Interrupted Sutures Through the Common AV Valve Leaflet

Interrupted sutures are passed from the superior edge of the VSD patch through the common AV valve leaflet tissue. These sutures establish the definitive relationship between the ventricular septum and the reconstructed valve.

The bites should engage durable leaflet tissue while preserving the mobile coaptation surface. Sutures placed too close to the free margin may reduce effective leaflet height or cause focal restriction. Sutures placed too close to the hinge may leave excessive unsupported tissue below the reconstructed septal attachment. The correct level follows the intended boundary between the right and left AV valve components and varies with leaflet and chordal morphology.

Interrupted sutures permit local control of leaflet position and tension, reduce purse-string distortion, and allow focal revision before tying. Suture spacing should eliminate residual communications without making the leaflet stiff or gathered. Patch-side and leaflet-side spacing should correspond; mismatch can plicate the leaflet, rotate the patch, or shift the reconstructed orifice.

Before proceeding to the ASD patch, the surgeon should confirm that the left AV valve orifice remains adequate, the right-sided orifice is not compromised, no important chordae are trapped, and the bridging leaflets retain unrestricted excursion. Particular caution is required when dense superior bridging-leaflet chordae obscure the septal crest or when papillary muscle abnormalities limit leaflet mobilization [2].

5. Preserving Left AV Valve Competence Without Creating Stenosis

The reconstructed left AV valve is highly sensitive to the position of the patch–leaflet attachment. The line influences annular shape, leaflet height, zone-of-apposition alignment, and inflow area.

Stenosis may result from excessive inferior traction, incorporation of too much mobile leaflet tissue, asymmetric division of the common valve, or an intrinsically abnormal subvalvar apparatus. Short chordae, hypoplastic bridging-leaflet tissue, and other subvalvar malformations can create a restrictive funnel even when the visible attachment appears satisfactory [3].

Regurgitation may result from inadequate support, asymmetric tension, malalignment of the zone of apposition, leaflet prolapse, or chordal tethering. The patch–leaflet sutures should position the leaflet to permit coaptation; competence should not be created through excessive traction.

The attachment line and closure of the left AV valve zone of apposition are related but distinct maneuvers. The patch sandwich establishes septation and septal leaflet attachment, but it does not correct every mechanism of regurgitation. Valve morphology must be assessed independently, and the zone of apposition should be managed according to the individual anatomy and the risk of stenosis.

6. Step 3: Passing the Same Sutures Through the ASD Patch

After all sutures have traversed the common AV valve leaflet, the same sutures are passed through the inferior margin of the ASD patch on the atrial side. Each suture now connects:

1. The superior margin of the VSD patch
2. The common AV valve leaflet tissue
3. The inferior margin of the ASD patch

The ASD patch should be oriented before the sutures are passed. Rotation or asymmetric trimming can pull the leaflet toward one atrium, distort the reconstructed AV junction, or create folds adjacent to the valve. Its inferior edge should align naturally with the leaflet attachment, while the remainder closes the primum defect without tension or excessive redundancy.

Patch design must also account for the coronary sinus and systemic and pulmonary venous pathways. Regardless of the coronary sinus strategy, the inferior ASD patch attachment should not alter the valve geometry already established.

7. Step 4: Tying the Patch–Leaflet–Patch Sutures

The sutures are tied only after the VSD patch, leaflet tissue, and ASD patch have been aligned. Tying converts the provisional arrangement into the definitive geometry of the reconstructed AV junction.

The knots must approximate the three layers without strangulating the leaflet. Excessive tension may produce puckering, loss of mobility, narrowing of the left AV valve orifice, distortion of the zone of apposition, or tissue tearing. Insufficient tension can leave gaps and produce residual ventricular- or atrial-level shunting.

A balanced tying sequence is preferable to tying continuously from one end without reassessment. The surgeon should repeatedly inspect the leaflet attachment, patch curvature, valve orifice, and chordal relationships. Any gathered or restrictive segment should be corrected before all sutures are secured.

The final line does not need to be perfectly straight. It should conform to the three-dimensional anatomy of the common AV junction. Functional symmetry and preserved leaflet motion are more important than visual linearity.

8. Intraoperative Assessment and Outcome-Relevant Findings

After septation, saline testing should define the mechanism and severity of residual regurgitation. Assessment should include leaflet coaptation, the zone of apposition, commissural leakage, tethering, prolapse, orifice size, and the integrity of the patch–leaflet junction.

Transesophageal echocardiography after cardiopulmonary bypass should confirm:

• No significant residual VSD or primum ASD
• No clinically important left or right AV valve stenosis
• Acceptable AV valve competence
• Preserved biventricular function
• An unobstructed LVOT
• No major patch-related distortion

Long-term results support the durability of a carefully executed two-patch repair. In 100 consecutive patients undergoing two-patch repair with complete closure of the left AV valve zone of apposition, freedom from reoperation for left AV valve dysfunction was 94% at 10 years; 80% had absent or trace regurgitation at latest follow-up [4]. However, the postoperative valve result remains a major determinant of later events. Moderate-or-greater left AV valve regurgitation at discharge independently predicted reoperation, with a hazard ratio of 10.85 [5]. Complete septation should therefore not be accepted if a clinically important and correctable valve lesion remains.

LVOT obstruction is less common than left AV valve dysfunction but remains an important late mechanism of reoperation. In a series focused on LVOT obstruction after AV canal repair, it was described as the second most frequent reason for reoperation, and recurrence accumulated during follow-up [6]. The mechanism is multifactorial and may involve the elongated outflow tract, bridging-leaflet or chordal tissue, septal geometry, and patch-related distortion. The superior VSD patch and leaflet attachment should therefore be inspected specifically for LVOT encroachment.

Evidence regarding heart block and residual shunting is less detailed for this specific maneuver. A large historical series reported 10-year freedom from reoperation of 97% for residual VSD and 98% for permanent pacemaker insertion [7]. These data suggest that major residual septal defects and conduction injury requiring reintervention can be uncommon, but they do not define the incidence of transient postoperative AV block or small residual shunts. Conduction-sparing patch placement and complete closure of the patch–leaflet junction remain essential.

9. Operative Principles

The patch–leaflet–patch sequence is a three-dimensional valve reconstruction, not simply a method of closing two septal defects. The essential principles are:

• Size and position the VSD patch according to the individual ventricular, valvar, and subvalvar anatomy.
• Distinguish native VSD height from surgically selected patch height; current evidence does not validate a universal geometric threshold.
• Attach the common AV valve leaflet at a level that preserves balanced right and left AV valve orifices.
• Use interrupted sutures to control local leaflet position and avoid purse-string distortion.
• Incorporate durable leaflet tissue while preserving the mobile coaptation surface.
• Identify abnormal papillary muscles, short or dense chordae, hypoplastic bridging-leaflet tissue, double-orifice morphology, and zone-of-apposition asymmetry before fixing the attachment line.
• Align the ASD patch without rotating or displacing the leaflet.
• Tie the sutures tightly enough to eliminate gaps but without restricting the valve.
• Reassess competence, stenosis, residual shunting, conduction safety, and LVOT geometry before completing the repair.

A successful reconstruction creates continuous atrial and ventricular septation while preserving a mobile, competent, and nonstenotic AV valve. The strongest available evidence indicates that intrinsic valve and subvalvar abnormalities and the residual postoperative valve lesion are more predictive of adverse outcomes than the measured depth of the ventricular septal deficiency alone.

References

[1] Fong LS, Youssef D, Ayer J, Nicholson I, Winlaw D, Orr Y. Correlation of ventricular septal defect height and outcomes after complete atrioventricular septal defect repair. Interact Cardiovasc Thorac Surg. 2021. doi:10.1093/icvts/ivab263.

[2] Ando M, Takahashi Y. Variations of atrioventricular septal defects predisposing to regurgitation and stenosis. Ann Thorac Surg. 2010. doi:10.1016/j.athoracsur.2010.03.098.

[3] Villar S, Wu TT, Doan TT, Cho J, Wadhwa L, Clunie S, Heinle JS, Orr Y. 30 years of left atrioventricular valve reoperations following atrioventricular septal defect repair: impact of valvar stenosis. J Thorac Cardiovasc Surg. 2025. doi:10.1016/j.jtcvs.2025.06.025.

[4] Bakhtiary F, Takács J, Cho M, Rázek V, Dähnert I, Doenst T, Walther T, Borger M, Mohr F, 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.

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

[6] Myers P, del Nido PJ, Marx GR, Emani SM, Mayer JE Jr, Pigula FA, Baird CW. Improving left ventricular outflow tract obstruction repair in common atrioventricular canal defects. Ann Thorac Surg. 2012. doi:10.1016/j.athoracsur.2012.04.009.

[7] 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.