Complete AVSD Repair with Two-Patch Technique #7: ASD Patch Closure

1. Surgical Objective

Closure of the primum atrial septal defect is the final major reconstructive step of a standard two-patch repair of complete atrioventricular septal defect (AVSD). At this stage, the ventricular component has been patched, the common atrioventricular valve has been partitioned into right and left components, and the left atrioventricular valve zone of apposition has been repaired according to valve morphology.

The atrial patch must complete atrial septation without compromising the reconstructed valves, venous pathways, coronary sinus, or atrioventricular conduction axis. The inferior and posteroinferior suture line should not simply follow the apparent margin of the primum defect. It must be redirected through secure tissue while avoiding the expected location of the displaced atrioventricular node.

A practical sequence is to advance the suture line along the reconstructed left atrioventricular valve annular or leaflet attachment, continue onto the left atrial wall, and then return to the remaining atrial septal margin. The goal is a stable, unobstructive, conduction-sparing atrial septum that remains mechanically compatible with the reconstructed atrioventricular valve complex.

2. Relevant Surgical Anatomy

2.1 Reconstructed Inferior Border

The primum defect occupies the inferior atrial septum immediately above the common atrioventricular junction. Unlike a secundum defect, it lacks a normal muscular inferior rim. After ventricular patch closure and valve partitioning, the lower boundary of the atrial defect is surgically reconstructed.

This border may include the superior edge of the ventricular patch, bridging-leaflet tissue, the newly created valve attachment line, or a combination of these structures. The atrial patch must be seated on this composite border without leaving a gap at the junction of the ventricular patch, valve tissue, and atrial patch.

Excessive tension may pull the reconstructed left atrioventricular valve toward the septum, shorten effective leaflet height, or alter coaptation. Inadequate tissue purchase may cause patch dehiscence or a residual shunt.

2.2 Displaced Atrioventricular Conduction Axis

In complete AVSD, the atrioventricular node is displaced posteroinferiorly, and the penetrating conduction axis arises near the inferior aspect of the defect. The node is not usually visible; protection depends on recognizing the high-risk territory and planning the patch pathway around it.

The hazardous region is the posteroinferior transition near the crux, where the reconstructed valve attachment, atrial wall, residual septal tissue, and conduction axis are closely related. A deep or tightly secured suture may cause direct injury, compression, ischemia, or postoperative edema.

Aeba and colleagues described a suture line that originated on the artificial or native ventricular septal crest and continued leftward above the annulus of the left inferior leaflet at the posteroinferior corner. No atrioventricular block occurred among 64 patients [1]. Koshiyama and colleagues later described a shallow suture placed only within the endocardium above the atrioventricular node [2]. Together, these techniques emphasize both deliberate redirection and strict control of bite depth.

2.3 Coronary Sinus and Left Atrial Wall

The coronary sinus ostium lies near the posteroinferior atrial septum and should be identified before patch completion. It may remain on the right atrial side or be incorporated into the left atrium, but it must not be narrowed or inadvertently closed.

The left atrial wall provides an alternative anchoring surface after the suture has passed the reconstructed left atrioventricular valve attachment. Bites should be secure but not excessively deep. The completed patch should lie flush without creating a ridge near the left atrioventricular inflow or pulmonary venous pathway.

3. Patch Selection and Sizing

The primum defect is commonly closed with autologous pericardium or another supple patch material. The patch should be flexible enough to conform to the reconstructed atrial septal plane and strong enough to tolerate the chosen suture technique.

Sizing is performed after ventricular closure and valve reconstruction because these steps alter the final geometry. The patch should close the defect without tension but should not be so redundant that it folds, bulges into either atrium, or interferes with atrioventricular inflow. The inferior edge should match the reconstructed valve contour, while the superior portion should follow the residual septal margin without distorting caval or pulmonary venous pathways.

Mild redundancy is preferable to an undersized patch under tension, but excessive redundancy complicates de-airing and may create folds. Patch orientation should therefore be defined before suturing.

4. Operative Suture Sequence

4.1 Inferior Attachment

The lower patch edge is secured to the reconstructed atrioventricular junction. Depending on the technique, this may include the upper edge of the ventricular patch, partitioned bridging leaflets, or the reconstructed annular line.

Bites should be placed in durable tissue and spaced closely enough to prevent residual shunting. Excessive leaflet incorporation should be avoided. Deep bites may restrict leaflet excursion, whereas bites too close to a thin leaflet edge may tear through.

The patch must remain in the intended atrial septal plane without pulling the left atrioventricular valve superiorly, posteriorly, or toward the septum.

4.2 Segment 1: Along the Left Atrioventricular Valve Attachment

As the suture approaches the posteroinferior corner, it is redirected along or immediately above the annular or leaflet attachment of the reconstructed left atrioventricular valve. This is the defining conduction-sparing maneuver.

Bites should be shallow, evenly spaced, and placed under direct vision. The attachment line is used as a controlled pathway to bypass the expected nodal territory. The Aeba technique demonstrated that suturing above the annulus of the left inferior leaflet can be associated with a very low observed risk of heart block [1].

At the junction of the ventricular patch, leaflet tissue, and atrial patch, the surgeon must balance two competing risks. An incompletely seated corner may produce a residual shunt. Excessive tightening may cause puckering, leaflet tethering, or focal narrowing of the reconstructed valve orifice.

4.3 Segment 2: Onto the Left Atrial Wall

After passing the nodal region, the suture line is redirected onto the left atrial wall. The transition should be smooth because an abrupt change in direction concentrates tension and increases the risk of tissue tearing or patch distortion.

A shallow endocardial bite is particularly important near the expected node. The simplified technique described by Koshiyama and colleagues emphasizes endocardial purchase above the node rather than deep myocardial penetration [2].

The patch should remain flat against the atrial wall. An inward fold may narrow the left atrioventricular inflow, particularly in a small infant.

4.4 Segment 3: Return to the Atrial Septal Margin

After bypassing the conduction territory, the suture returns to the firm posterior, superior, and anterior margins of the primum defect. These areas usually provide more conventional atrial septal tissue.

Before tying, the surgeon should inspect the circumference for gaps, folds, asymmetric traction, and excessive tension. The inferior patch edge should remain seated without restricting either atrioventricular valve, and the superior patch should not encroach on systemic or pulmonary venous pathways.

5. Preservation of Atrioventricular Valve Geometry

The atrial patch and reconstructed atrioventricular valves are mechanically interdependent. A complete atrial closure may still produce an unsatisfactory result if the patch changes annular geometry or leaflet motion.

Inferior sutures should capture only the tissue required for secure fixation. The transition from the valve attachment to the left atrial wall should distribute tension gradually rather than concentrate it at a single posteroinferior point.

After the patch is seated, the left atrioventricular valve should be reassessed by direct inspection and saline testing when exposure permits. New leaflet restriction, loss of coaptation, or asymmetry of the reconstructed orifice should prompt revision. The right atrioventricular valve should also be examined because the inferior attachment may influence both components of the divided common valve.

In a two-patch series of 115 patients, Backer and colleagues reported reoperation for left atrioventricular valve insufficiency in 7%; permanent pacemaker implantation for heart block was required in 3.5% [3]. In a series of 100 patients repaired with a two-patch technique and complete cleft closure, freedom from reoperation for left atrioventricular valve dysfunction was 94% at 10 years, with no perioperative or late mortality [4].

6. Conduction-System Protection

Conduction protection depends on three coordinated measures:

1. Recognition that the posteroinferior septal margin is not a routine safe suture line.
2. Redirection of the suture along the left atrioventricular valve attachment and left atrial wall.
3. Strict control of bite depth and suture tension.

The pathway and depth are equally important. A correctly selected route may still injure the conduction system if the needle passes deeply. Conversely, a shallow bite cannot compensate for a suture placed directly through the nodal territory.

Rhythm should be observed during repair, rewarming, and separation from cardiopulmonary bypass. New PR prolongation, junctional rhythm, second-degree block, or complete atrioventricular block should raise concern for injury, compression, or edema near the suture line. Persistent disturbance may justify immediate inspection and selective revision of the posteroinferior attachment.

7. Completion and Intraoperative Assessment

Before final closure, the left atrium should be irrigated and inspected for retained blood, debris, and air. Standard de-airing should include controlled filling, appropriate venting, and gentle lung inflation when indicated.

The completed patch should be inspected from the right atrial side. The surgeon should confirm that there is no visible gap, the coronary sinus pathway is preserved, the caval pathways are unobstructed, and the patch is not under excessive tension.

Intraoperative transesophageal or epicardial echocardiography should assess:

• Residual primum atrial or ventricular shunting.
• Left and right atrioventricular valve regurgitation.
• Atrioventricular valve stenosis or inflow acceleration.
• Left ventricular outflow tract obstruction.
• Systemic and pulmonary venous return.
• Biventricular filling and systolic function.

Moderate or greater left atrioventricular valve regurgitation at discharge is a major warning sign. In a cohort of 138 patients, it was associated with a hazard ratio of 10.85 for reoperation; freedom from reoperation was 84.3% at 8 years [5].

8. Common Technical Failure Modes

8.1 Atrioventricular Block

Atrioventricular block may result from a deep suture near the displaced node, direct passage through the nodal territory, excessive local tension, ischemic injury, or edema. Prevention requires both an appropriate pathway and shallow tissue purchase. Permanent heart block remains possible even with established two-patch techniques [3].

8.2 Left Atrioventricular Valve Dysfunction

Regurgitation may worsen if the patch tethers a leaflet, distorts the annulus, or shifts the coaptation line. Stenosis may result from excessive leaflet incorporation or traction that narrows the reconstructed orifice.

Intrinsic morphology also influences outcome. Absence of a double-orifice left atrioventricular valve and complete cleft closure were independent predictors of improved survival in a large complete AVSD series [6]. Patch technique cannot fully overcome unfavorable valve anatomy.

8.3 Residual Shunt or Patch Dehiscence

Residual shunting commonly occurs at the junction of the ventricular patch, bridging-leaflet tissue, and atrial patch. Closely spaced bites, secure tissue purchase, and even tension are essential. Suture failure may also reopen the left atrioventricular valve zone of apposition and produce recurrent regurgitation.

8.4 Venous or Coronary Sinus Obstruction

An improperly positioned patch may narrow the coronary sinus ostium, distort caval inflow, or create a ridge near pulmonary venous return. These complications are uncommon but should be excluded before leaving cardiopulmonary bypass.

9. Postoperative Implications

Postoperative surveillance should focus on rhythm, atrioventricular valve function, residual shunting, pulmonary artery pressure, and ventricular filling. Continuous telemetry is essential because conduction abnormalities may appear immediately or evolve during the early postoperative period.

Echocardiography should define both the severity and mechanism of valve dysfunction. Restricted motion adjacent to the atrial patch suggests suture-related tethering or geometric distortion. A residual shunt near the inferior patch margin suggests incomplete seating at the valve-patch junction.

Hemodynamic management should avoid unnecessary increases in systemic vascular resistance and left ventricular afterload when left atrioventricular valve regurgitation is present. Adequate preload is required, but excessive volume loading may increase left atrial pressure and regurgitant volume.

Patient-specific risk remains important. Greater age at repair, shorter ischemic time, absence of double-orifice valve anatomy, and complete cleft closure were associated with better survival in one large series [6]. Conversely, dysplastic atrioventricular valve tissue, severe preoperative cardiopulmonary instability, and persistent postoperative pulmonary hypertension were associated with increased mortality in another two-patch cohort [7].

10. Key Surgical Principles

ASD patch closure in complete AVSD is governed by four priorities:

1. Complete atrial septation without residual shunting.
2. Deliberate avoidance of the displaced atrioventricular node and conduction axis.
3. Preservation of right and left atrioventricular valve geometry.
4. Maintenance of unobstructed systemic venous, pulmonary venous, and coronary sinus pathways.

The defining maneuver is the posteroinferior redirection of the suture line: first along or above the left atrioventricular valve attachment, then onto the left atrial wall, and finally back to the secure atrial septal margin. Shallow bites and controlled tension are essential.

The repair should be judged by the integrated result: preserved atrioventricular conduction, competent and unobstructed atrioventricular valves, no residual septal shunt, unobstructed venous pathways, and stable postoperative hemodynamics.

References

[1] Aeba R, Katogi T, Kashima I, Mitsumaru A, Takeuchi S, Kawada S. Placement of interatrial patch suture lines in atrioventricular canal defect repair. J Cardiovasc Surg (Torino). 2000;41(2):223-226.

[2] Koshiyama H, Ishidou M, Ito H, Hirose K, Sakamoto K, Ikai A. Simplified primum ASD closure technique in complete VSD repair: shallow suture crossing on the AV node. Gen Thorac Cardiovasc Surg. 2022. doi:10.1007/s11748-022-01901-8.

[3] Backer CL, Mavroudis C, Alboliras ET, Zales VR. Repair of complete atrioventricular canal defects: results with the two-patch technique. Ann Thorac Surg. 1995;60(3):530-537.

[4] 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;89(4):1239-1243.

[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;45(4):610-617.

[6] 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;96(9 Suppl):II-311-II-315.

[7] Alexi-Meskishvili V, Ishino K, Dähnert I, Uhlemann F, Weng Y, Lange PE, Hetzer R. Correction of complete atrioventricular septal defects with the double-patch technique and cleft closure. Ann Thorac Surg. 1996;62(2):519-525.