VSD Patch Closure — Posteroinferior Margin (3D Model)

Date
September 30, 2025
URL
https://x.com/withascalpel/status/1972994043060666726?s=46
Categories
Cardiac SurgeryVSDSurgical Training

VSD Patch Closure — Part 2: posteroinferior Margin

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Orientation and risk landscape

Along the inferoposterior rim of a perimembranous VSD, the atrioventricular conduction axis lies closest to the operative field: the penetrating His traverses the central fibrous body, becomes the non-penetrating His at the septal crest, and then bifurcates; the right bundle branch (RBB) typically emerges near the base of the medial papillary muscle (MPM) on the RV septal surface. Because this segment is the “danger arc,” needle placement should deliberately stand off the anatomic edge to mitigate iatrogenic heart block [1,3].

Exposure and anatomic landmarks

  • Tricuspid valve (TV) septal leaflet. Drapes the posteroinferior margin and offers a safe, vascularized plane for short, superficial bites. Guard against leaflet capture or chordal tethering.
  • Medial papillary muscle (MPM). A reproducible surface landmark for the RBB’s emergence; use it to mentally map the no-fly zone [3].
  • Membranous septum ↔ leaflet hinge. Plan the transition stitch(es) where the septal leaflet meets the VSD rim; this is where the line “turns the corner” toward the AV junction.

Suture strategy and needle discipline

Evidence-based target line. Contemporary series support shallow suturing at (or within ~2 mm of) the VSD rim along the inferoposterior arc rather than the historical practice of deep stitches 2–5 mm away. This approach reduced complete RBBB from 43.8% to 6.3% in one comparative cohort [1] and lowered late RBBB and TR progression in a larger, modern series (39.6% → 14.9% RBBB) without added complications [2].

  1. Offset and depth. Track the patch 1–2 mm off the rim with tangential, atrial-biased bites (<1–2 mm depth) to avoid the conduction plane [1,2,3].
  2. Running vs interrupted. A fine running monofilament (5-0/6-0 polypropylene) minimizes needle passes in the danger zone and equalizes tension; if tissue quality varies, use selective interrupted/pledgeted stitches to distribute load without depth penalties [4].
  3. Transition under the TV. At the leaflet hinge, place a low-profile transition stitch that keeps the patch flush while preserving leaflet mobility; skirt the hinge, avoid leaflet body/primary chordae.
  4. Knot management. Seat knots on the RA side away from leaflet excursion to limit abrasion and postoperative TR.

Tricuspid valve preservation

  • Leaflet handling. Gentle retraction typically suffices; temporary annular detachment is reserved for exposure-limited cases and is not associated with worse valve function when performed carefully [6,7].
  • Avoid tether/“patch lift.” Keep the patch low-profile beneath the leaflet to maintain septal-leaflet coaptation and prevent TR.
  • Chordal pathways. Identify secondary/tertiary chords crossing the field; if snagged, remove and re-place the stitch before proceeding.

Residual shunt prevention and assessment

  • Patch sizing. Slight oversizing by ~1–2 mm permits an offset line and a circumferential seal without tension.
  • Eliminate dead space. Keep 1–2 mm stitch spacing across the inferior arc; small gaps here explain many residual jets.
  • Intraoperative check. Prior to atriotomy closure, perform a saline test or gentle LV vent “flush” with the TV in view; address any jet immediately.

Materials and technical refinements

  • Patch. Thin treated autologous pericardium or ePTFE that drapes without spring-back; in neonates, select ultra-thin material to minimize bulk under the leaflet.
  • Suture. Fine polypropylene is standard; a softer monofilament may reduce cheese-wiring in delicate tissue [4].
  • Adjunct hemostasis. Micro-ooze along the offset line usually resolves after a low-pressure test and a single reinforcing bite; avoid bulky sealants near the hinge.

Variants and special scenarios

  • Inlet extension. The axis courses even closer to the rim—increase stand-off and shorten bite depth accordingly [3].
  • Aneurysmal membranous tissue. Resect only if it obscures the rim or threatens leaflet motion; otherwise incorporate with shallow edge-controlled stitches.
  • Large defects. A mattress-style shallow stitch can add security while preserving conduction tissue in infants with large pmVSDs [5].

Pitfalls and how to avoid them

  • Conduction injury. Most often from deep bites on the true edge—maintain offset, keep bites shallow, and avoid LV-directed needle trajectories [1–3].
  • Leaflet distortion/TR. Prevent leaflet capture and patch elevation; keep stitches beneath the hinge and the patch flat.
  • Residual VSD. Prevent by tight spacing along the inferior arc and correct sizing; fix any detected jet immediately.

Post-repair assessment and postoperative care

  • Intraoperative echo. Confirm no residual shunt, preserved TV coaptation, and absent aortic cusp interaction. A trivial central TR jet is common; a new eccentric or ≥moderate TR merits inspection of the hinge segment.
  • Rhythm surveillance. RBBB is relatively common; a new AV block demands readiness for pacing. Place temporary A/V wires in neonates/infants or higher-risk cases [8].
  • Hemodynamics. Avoid hypertension/excess afterload early after bypass—both exaggerate trivial leaks and leaflet tether.

References

[1] Fukuda T, Suzuki T, Kashima I, Sato M, Morikawa Y. Shallow stitching close to the rim of the ventricular septal defect eliminates injury to the right bundle branch. Ann Thorac Surg. 2002;74(2):550–555.

[2] Kim DH, et al. Shallow suture at ventricular septal defect may safely reduce right bundle branch block. Cardiol Young. 2023;33(10):1792–1801.

[3] Anderson RH, Becker AE, Brechenmacher C, Davies MJ, Rossi L. The surgical anatomy of the conduction tissues. Thorax. 1983;38(6):408–420.

[4] Manning PB. Ventricular Septal Defect Closure: How I Teach It. Ann Thorac Surg. 2018;106(2):324–326.

[5] Shi G, Chen H, Sun Q, Zhang H, Zheng J. Mattress Stitch—A Modified Shallow Stitching in the Surgical Closure of Large Perimembranous Ventricular Septal Defect in Infants. Ann Thorac Cardiovasc Surg. 2015;21(3):282–288.

[6] Fraser CD III, Zhou X, Palepu S, et al. Tricuspid Valve Detachment in Ventricular Septal Defect Closure Does Not Impact Valve Function. Ann Thorac Surg. 2018;106(1):145–150.

[7] Gaynor JW, O’Brien JE Jr, Rychik J, et al. Outcome following tricuspid valve detachment for ventricular septal defect closure. Eur J Cardiothorac Surg. 2001;19(3):279–284.

[8] Scully BB, Morales DL, Zafar F, et al. Current Expectations for Surgical Repair of Isolated Ventricular Septal Defects. Ann Thorac Surg. 2010;89(2):544–551.

(Heart model used with permission from CrossMedical, Inc.)