Partial AVSD Repair — Cleft Closure and Primum ASD Patch Closure

Operative goals

Restore durable left atrioventricular (AV) valve competence, maintain an adequate orifice without stenosis, and close the primum atrial septal defect while safeguarding the posterior–inferior AV node and His bundle. Success is geometry-driven: coaptation height, chordal alignment, and the suture trajectory must respect the AV-canal conduction axis and leaflet mechanics [1–3].

1) Left AV valve “cleft” (anterior leaflet) closure

Assessment. After thorough saline testing, define the true zone of apposition between the superior and inferior bridging leaflets, identify the primary chordae to each margin, and survey papillary muscle orientation. Exclude coexisting drivers of regurgitation—annular dilation, leaflet deficiency, commissural prolapse, or papillary displacement [1,2].

Technique. Approximate the cleft edges toward the primary chordae with fine, closely spaced interrupted sutures (e.g., 6-0 polypropylene) beginning at the cleft nadir and advancing atrially. Take shallow leaflet bites to avoid chordal capture; preserve a short neo-commissural gutter to prevent functional commissural fusion. Re-test with saline every two to three stitches and titrate bite depth/spacing to balance competence with mobility. Routine cleft closure has been associated with improved freedom from significant left AV valve regurgitation and reoperation in long-term series [1,4].

Avoiding stenosis. Size the orifice directly (or with a ring sizer) to determine how far to close; stop when coaptation is broad and central and opening remains free. When the cleft is deep or tissue is scant, limit closure or supplement with focused commissuroplasty rather than over-tightening to a gradient [1,4].

2) Ventricular-side anchoring for the primum ASD patch

Place ventricular-margin sutures along the crest of the muscular septum where tissue is robust. This line lies anterior to the posteriorly displaced node–His complex and avoids the non-branching His segment [2,3]. In small annuli or when exposure is restricted, judicious use of the septal tricuspid leaflet (brief detachment/reattachment or leaflet-edge anchoring) can flatten the seal and improve hemostasis without compromising leaflet motion. Keep bites superficial near the membranous septum to spare the right bundle branch. Pledgeted 5-0 non-absorbable sutures provide secure purchase with minimal bulk.

Patch selection. Fresh or lightly treated autologous pericardium remains a preferred material for primum ASD closure owing to pliability, hemostasis, and favorable remodeling, with thin PTFE as an alternative when pericardium is unsuitable [5]. Tailor an elliptical patch with a low posterior profile to avoid crowding the AV junction or billowing into the LVOT.

3) Primum ASD patch closure: a conduction-safe course

To protect the AV node and nodal triangle, complete the atrial suture line in three deliberate segments:

1. Annular segment (left AV valve hinge). Begin at the hinge of the inferior bridging leaflet on the left AV annulus. Short, tangential bites anchor the patch while preserving leaflet excursion.
2. Left atrial wall segment. Swing posteriorly onto the left atrial wall, skirting the coronary sinus and remaining clear of the posterior–inferior nodal region [2,3].
3. ASD edge segment. Transition smoothly to the free edge of the primum defect and complete the anterosuperior limb along the anterior rim.

This atrial-wall “detour” posteriorly, before turning to the defect edge, is the safest path around the displaced conduction tissues and reduces the risk of permanent heart block [2,6].

Intraoperative assessment and troubleshooting

• Hydrostatic testing after cleft closure and again after patching should yield broad, central coaptation without billowing or restriction.
• Transesophageal echocardiography—preferably with real-time 3D imaging—confirms trivial or no regurgitation, a low transmitral gradient, absence of residual shunt, and an unobstructed LVOT; 3D TEE improves leaflet/commissural visualization and patch seating in AVSD repairs [7].
• If regurgitation persists, reassess for under-addressed cleft depth, chordal entrapment, or papillary malalignment.
• If the transmitral gradient rises, remove the last stitch or widen the neo-commissural gutter; competence gained at the cost of stenosis is not durable.

Pearls and pitfalls

• Close toward chordae, not toward the annulus—this restores physiologic support and avoids tethering [1].
• Short, shallow bites near the membranous septum to protect the conduction axis [2,3,6].
• Avoid over-narrowing the left AV orifice; titrate to coaptation, not tightness [1,4].
• Keep the posterior patch line on atrial wall before turning to the ASD rim—the canonical conduction-safe route [2,6].
• Hemostasis and geometry beat bulk: thin patches, small pledgets, and even tension create a smooth atrial surface and stable leaflet mechanics.

Expected outcomes. Contemporary series report excellent survival after partial AVSD repair, with late attrition driven chiefly by recurrent left AV valve regurgitation and, less commonly, stenosis or conduction disturbance; lifelong surveillance is warranted given meaningful reintervention risk over time [4].

References

[1] Backer CL, Stewart RD, Kelle AM, Mavroudis C. Repair of partial atrioventricular canal defect with routine cleft closure: results and techniques. Ann Thorac Surg. 2007;84(2):594-600.

[2] Anderson RH, Cook AC, Ho SY. The anatomy of atrioventricular septal defects with reference to the conduction tissues. Cardiol Young. 2004;14(6):623-637.

[3] Becker AE, Anderson RH. The conduction tissues in congenitally malformed hearts. Eur J Cardiol. 1976;4(2):147-160.

[4] Buratto E, Ye XT, King G, et al. Long-term outcomes after repair of partial atrioventricular septal defect. J Thorac Cardiovasc Surg. 2016;152(3):666-674.

[5] Konstantinov IE, Brizard CP, d’Udekem Y. Patch materials in congenital heart surgery: choosing the right one for the right job. Ann Thorac Surg. 2018;105(2):681-689.

[6] Fasting H, Bjørnstad PG, Smevik B. Atrioventricular block after surgery for partial atrioventricular septal defect: mechanisms and prevention. Scand J Thorac Cardiovasc Surg. 1980;14(2):171-175.

[7] Cheng HC, Tsai SK, Chen SJ, et al. Utility of real-time three-dimensional transesophageal echocardiography in atrioventricular septal defect surgery. Echocardiography. 2012;29(1):E14-E18.