Complete AVSD Repair with Two-Patch Technique #6: Left Atrioventricular Valve Cleft Closure

1. Surgical Objective

Left atrioventricular valve (LAVV) cleft closure is a central step in complete atrioventricular septal defect (AVSD) repair. After the common atrioventricular valve has been functionally divided into right and left components by the ventricular and atrial septal patches, the surgeon must reconstruct a competent left-sided valve while preserving an adequate inflow orifice.

The objective is not simply to eliminate the visible gap between the left superior and left inferior bridging leaflets. The repair must create a broad, stable zone of coaptation, preserve leaflet mobility, maintain alignment with the chordal and papillary muscle apparatus, and avoid iatrogenic stenosis. Long-term series using two-patch repair with complete cleft closure have demonstrated favorable valve competence and freedom from reoperation, supporting complete closure when the anatomy permits it without obstruction [1]. Complete cleft closure has also been associated with improved survival in a large historical series [2].

2. Anatomical Basis of the “Cleft”

The structure commonly called the LAVV cleft is more precisely the zone of apposition between the left superior and left inferior bridging leaflets. It is not equivalent to a congenital cleft in an otherwise normal mitral valve. The reconstructed LAVV consists principally of the two left bridging-leaflet components and the left mural leaflet, supported by a variable chordal and papillary muscle arrangement.

Valve competence depends on the interaction of the entire apparatus:

• Left superior bridging leaflet
• Left inferior bridging leaflet
• Left mural leaflet
• Primary and secondary chordae
• Anterior and posterior papillary muscles
• Reconstructed atrioventricular septal junction
• VSD and ASD patches

The closure line should follow the natural orientation of the bridging leaflets toward their primary chordal support. A geometrically neat edge-to-edge closure may still fail if it twists the leaflets, shortens the effective free margin, or pulls the reconstructed septal leaflet away from the mural leaflet.

Preservation of bridging-leaflet integrity is important. Division of the bridging leaflets has been associated with a higher incidence of moderate-or-greater atrioventricular valve regurgitation during the first postoperative year. Reoperations frequently reveal cleft dehiscence, leaflet tears, or failure at the leaflet-patch interface [3]. Leaflet division may occasionally be required for exposure or reconstruction, but it should not be regarded as an anatomically neutral maneuver.

3. Assessment Before Cleft Closure

Cleft closure should be performed after the VSD patch has been secured and the bridging leaflets have assumed their intended reconstructed position. Patch height, leaflet fixation, and the relationship between the bridging leaflets and the ventricular septum may alter the apparent length and orientation of the zone of apposition.

Before suturing, the surgeon should assess:

• Leaflet thickness, pliability, and tissue quality
• Symmetry and length of the two cleft margins
• Size and mobility of the mural leaflet
• Location of the primary chordae
• Restrictive secondary or septal chordal attachments
• Papillary muscle position and separation
• Existing prolapse, tethering, or leaflet deficiency
• Estimated residual valve area after closure

The leaflet margins should approximate without excessive traction. If substantial force is required, definitive closure may create leaflet restriction, focal prolapse, or stenosis.

Short chordae, a hypoplastic inferior bridging leaflet, a double-orifice LAVV, abnormal papillary muscles, and dense chordal attachments may impair both coaptation and valve opening [4,5]. These abnormalities cannot always be corrected by extending the cleft closure. In some patients, an anatomically complete closure may worsen the functional result.

4. Marking Stitch and Preliminary Alignment

A temporary marking stitch may be placed first to confirm the intended line of closure. This stitch approximates the two bridging-leaflet edges at a central reference point and allows the surgeon to evaluate the proposed geometry before committing to multiple sutures.

The marking stitch should demonstrate that:

• The leaflet edges meet without excessive tension.
• The superior and inferior leaflet components remain in the same plane.
• The free margins do not evert toward the atrium.
• The closure line is directed toward the primary chordae.
• The reconstructed septal component continues to approach the mural leaflet appropriately.
• No focal bunching or step-off is created.

When the two cleft margins are unequal in length, direct closure without preliminary alignment may concentrate redundant tissue on one side, producing localized prolapse or puckering. Repositioning the marking stitch by only a few millimeters may substantially improve the final coaptation geometry.

The marking stitch should not be tied tightly enough to crush or invert the leaflet tissue. It functions primarily as a geometric guide.

5. Definitive Interrupted Suture Closure

Once alignment is satisfactory, the cleft is closed with multiple interrupted sutures. Interrupted sutures permit precise adjustment of individual leaflet segments and reduce the purse-string effect that may occur with a continuous suture.

The closure is generally advanced toward the primary chordae. The visible leaflet margins alone should not determine its direction. The surgeon should repeatedly confirm that the suture line remains aligned with the subvalvar support and does not rotate one bridging leaflet relative to the other.

Each bite should be sufficiently deep to provide durable tissue purchase but sufficiently limited to avoid incorporating secondary chordae or creating a rigid leaflet ridge. Shallow bites may tear through fragile tissue, whereas excessively deep bites may restrict leaflet motion.

The sutures should be spaced closely enough to prevent residual gaps but not so densely that they stiffen the coaptation line. The knots should approximate rather than strangulate the leaflet edges. Excessive overlap or atrial eversion creates a bulky seam and may produce persistent regurgitation.

6. Determining the Extent of Closure

Complete closure is preferred when it produces competence without obstruction. However, the optimal distal endpoint is anatomy-dependent. The closure should usually extend toward the primary chordae and stop before leaflet excursion or valve area becomes compromised.

Factors influencing the endpoint include:

• Preoperative LAVV size
• Mural leaflet width
• Length and mobility of the bridging leaflets
• Chordal length and distribution
• Papillary muscle geometry
• Presence of a double-orifice valve
• Ventricular balance
• Expected inflow requirement after repair

Incomplete closure leaves a potential residual regurgitant pathway and reduces the effective coaptation length. Conversely, excessive closure may produce a restrictive funnel, particularly in a small LAVV or in the presence of short chordae and hypoplastic leaflet tissue.

Subvalvar malformations are particularly important because stenosis-related reoperation has a substantially worse valve-preservation prognosis than regurgitation-related reoperation. In a large contemporary cohort, subvalvar abnormalities were the strongest predictors of reoperation for stenosis, and replacement-free survival after stenosis-related reoperation was markedly limited [5]. These findings support restraint when complete closure would place abnormal chordal or papillary muscle anatomy under excessive tension.

7. Broad Coaptation and Annular Geometry

The desired result is a broad surface of coaptation rather than a narrow point of edge contact. Broad coaptation distributes systolic load across a larger leaflet area and reduces stress on individual sutures.

The reconstructed valve should demonstrate:

• Smooth alignment of the superior and inferior bridging leaflets
• No residual gap along the closure line
• No leaflet eversion
• Preserved excursion during simulated diastolic opening
• Adequate contact between the reconstructed septal component and mural leaflet
• An adequate residual inflow orifice

Cleft closure alone may not fully correct regurgitation when annular dilation or deficient mural-leaflet coaptation is present. Experimental valve modeling demonstrated a progressive reduction in regurgitant volume from 12.5 mL per beat with an open cleft to 1.4 mL per beat after complete closure. Annular undersizing produced an additional reduction in regurgitation when annular dilation persisted [6].

These findings provide mechanistic support for selective annuloplasty but do not establish that annular reduction should be performed routinely. Annuloplasty is most relevant when residual regurgitation is caused by annular enlargement or inadequate leaflet apposition rather than primary leaflet restriction. Overcorrection may narrow the LAVV or distort the mural leaflet.

8. Saline Testing and Valve Sizing

After closure, the left ventricle is filled with saline while the surgeon observes the valve from the atrial side. The assessment should include the cleft line, central coaptation, mural-leaflet contact, commissural regions, and leaflet mobility.

A residual saline leak should be analyzed mechanistically. Potential causes include:

• Incomplete cleft closure
• Malalignment or focal leaflet eversion
• Mural-leaflet deficiency
• Leaflet prolapse
• Chordal restriction
• Commissural leakage
• Patch-related distortion

Additional sutures should not be placed automatically. A stitch added to treat an unexplained leak may convert regurgitation into stenosis or transfer the regurgitant orifice to another location.

A Hegar dilator is then used to confirm an adequate residual LAVV orifice. The dilator should pass without force, and its diameter should be interpreted according to the patient’s body size and expected valve dimensions.

Orifice sizing must be integrated with visual inspection and leaflet excursion. A valve may accept an apparently adequate dilator yet remain functionally restrictive because of abnormal chordal or papillary muscle geometry.

9. Anatomy Requiring Modification of the Standard Technique

Small LAVV or Unbalanced AVSD

In a small left-sided valve, complete closure may produce clinically important stenosis. The distal extent of closure may need to be limited, particularly when the mural leaflet is small or the left ventricular inflow is marginal.

Restrictive Chordae or Bridging-Leaflet Retraction

Secondary attachments to the septal crest may retract and flatten the medial LAVV component. Cleft closure under these conditions can increase tension, worsen regurgitation, or contribute to left ventricular outflow tract obstruction [7].

Selected cases may require release of restrictive attachments, leaflet detachment, or patch augmentation rather than forceful primary approximation. Any chordal intervention must preserve essential primary support.

Single or Abnormal Papillary Muscle

A single papillary muscle or closely spaced papillary muscles may create a parachute-like inflow and increase the risk of stenosis. Favorable biventricular repair is possible, but the cleft closure may require modification to preserve valve area [8].

Double-Orifice LAVV

Both orifices must be assessed after closure. A repair that improves central competence may unintentionally restrict one of the two inflow channels.

Dysplastic or Deficient Leaflet Tissue

Thin, retracted, or deficient tissue may not tolerate direct closure without tension. Primary closure may create leaflet restriction or predispose to dehiscence.

In redo surgery, cleft patch augmentation has demonstrated better freedom from subsequent reoperation than repeat primary closure in selected patients with normal papillary muscle anatomy [9]. Other reoperation series have similarly identified patch augmentation and earlier reintervention as factors associated with more durable repair [10].

10. Common Failure Modes

Residual LAVV regurgitation may result from incomplete closure, cleft dehiscence, leaflet malalignment, prolapse, mural-leaflet deficiency, annular dilation, or patch-induced distortion.

LAVV stenosis may result from excessive closure, restrictive chordae, abnormal papillary muscles, a small mural leaflet, or annular overcorrection.

Additional technical failure modes include:

• Leaflet eversion along the suture line
• Unequal suture tension causing asymmetric restriction
• Incorporation of chordae into the closure sutures
• Leaflet tearing from shallow or high-tension bites
• Dehiscence at a divided leaflet or patch interface
• Creation or worsening of left ventricular outflow tract obstruction

The mechanism, rather than the visual severity alone, should determine whether immediate revision is appropriate.

11. Intraoperative and Postoperative Evaluation

After separation from cardiopulmonary bypass, transesophageal or epicardial echocardiography should evaluate:

• Degree and mechanism of residual LAVV regurgitation
• Mean and peak diastolic gradients
• Leaflet excursion and coaptation length
• Direction and origin of residual jets
• Residual atrial or ventricular shunting
• Ventricular function
• Left ventricular outflow tract geometry

Measured gradients must be interpreted in the context of heart rate, loading conditions, ventricular function, and vasoactive support. Tachycardia or increased transmitral flow may elevate the measured gradient without fixed anatomic stenosis.

A satisfactory repair preserves unrestricted leaflet opening and avoids more than mild residual regurgitation or a clinically important diastolic gradient. Revision should be considered when a correctable geometric lesion is present and the anticipated improvement in competence outweighs the risk of stenosis.

12. Key Surgical Principles

1. Treat the “cleft” as the zone of apposition between the left bridging leaflets.
2. Assess the valve after the VSD patch and leaflet reconstruction have established the final geometry.
3. Use a marking stitch to confirm alignment before definitive closure.
4. Direct interrupted sutures toward the primary chordal support.
5. Preserve bridging-leaflet integrity whenever possible.
6. Create a broad coaptation surface without leaflet eversion or twisting.
7. Pursue complete closure when anatomically safe, but do not force closure through restrictive subvalvar anatomy.
8. Evaluate the mural leaflet, annulus, chordae, papillary muscles, and left ventricular outflow tract as components of a single functional apparatus.
9. Use saline testing and objective orifice sizing together.
10. Base additional repair on the mechanism of residual regurgitation or stenosis.

The ideal repair is not defined by the longest possible closure line. It is defined by durable coaptation, preserved leaflet mobility, an adequate inflow orifice, and stable integration of the reconstructed valve with the ventricular and atrial septal patches.

References

[1] 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.

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

[3] Fortuna R, Ashburn DA, Carias De Oliveira N, Burkhart HM, Konstantinov IE, Coles JG, Smallhorn JF, Williams WG, Van Arsdell GS. Atrioventricular septal defects: effect of bridging leaflet division on early valve function. Ann Thorac Surg. 2004. doi:10.1016/S0003-4975(03)01066-X.

[4] 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.

[5] Villar S, Wu TT, Doan TT, Cho J, Wadhwa L, Clunie S, Heinle JS, Orr Y. Thirty 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.

[6] Padala M, Vasilyev N, Owen JW, Jimenez JH, Dasi LP, del Nido PJ, Yoganathan AP. Cleft closure and undersizing annuloplasty improve mitral repair in atrioventricular canal defects. J Thorac Cardiovasc Surg. 2008. doi:10.1016/j.jtcvs.2008.05.043.

[7] Baird CW, Kreutzer C, Sanders SP, Borisuk MJ, del Nido PJ. Augmentation of bridging leaflets in repair of atrioventricular canal defects. Ann Thorac Surg. 2017. doi:10.1016/j.athoracsur.2017.02.036.

[8] Woodrick S, Kleeman KC, Yu S, Lowery R, Romano JC, Fifer C. Outcomes following biventricular repair of atrioventricular septal defect with a single left ventricular papillary muscle. Circulation. 2022. doi:10.1161/circ.146.suppl_1.9841.

[9] Sughimoto K, d’Udekem Y, Konstantinov IE, Brizard CP. Mid-term outcome with pericardial patch augmentation for redo left atrioventricular valve repair in atrioventricular septal defect. Eur J Cardiothorac Surg. 2016. doi:10.1093/ejcts/ezv013.

[10] Malhotra SP, Lacour-Gayet F, Mitchell MB, Clarke DR, Dines ML, Campbell DN. Reoperation for left atrioventricular valve regurgitation after atrioventricular septal defect repair. Ann Thorac Surg. 2008. doi:10.1016/j.athoracsur.2008.03.040.