ASD, VSD & PDA Device Closure — Devices, Deployment, and Sizing

Overview

1. Atrial Septal Defect (ASD)

What is it?

Devices Available

Deployment Steps (ASO — most widely used)

1. Venous access — Right femoral vein; diagnostic catheterization to confirm left-to-right shunt and measure Qp:Qs
2. Transseptal positioning — A guidewire is advanced across the defect into the left atrium (LA); the proprietary TorqVue delivery sheath is positioned in the LA
3. Sizing (see detailed sizing section below)
4. Left atrial disc deployment — The left disc is unsheathed in the LA
5. Pull back to septum — Sheath + device are pulled back so the left disc seats against the left side of the septum
6. Right atrial disc deployment — The right disc is deployed on the RA side, "sandwiching" the septal wall
7. Device testing — Gentle tug ("Minnesota wiggle") confirms secure position; color Doppler confirms no residual shunt
8. Release — Device is unscrewed from delivery cable
9. Imaging — Fluoroscopy + TEE/ICE confirm position and absence of obstruction to pulmonary veins, AV valves, coronary sinus

Indications for ASD Device Closure

• RV/RA dilatation with or without symptoms (Class I)
• Qp:Qs ≥ 1.5:1 or RV enlargement on echo
• Paradoxical embolism / platypnea-orthodeoxia (Class IIa)
• Minimum defect diameter >5 mm, maximum <40 mm
• All rims ≥5 mm to coronary sinus, IVC, AV valves, and right upper pulmonary vein

Contraindications

• Sinus venosus or primum ASDs (require surgery)
• Eisenmenger syndrome (irreversible pulmonary hypertension)
• Active infection/sepsis within 1 month
• Intracardiac thrombus on echo
• Rims <5 mm to adjacent critical structures (relative, especially for ASO)

2. Ventricular Septal Defect (VSD)

What is it?

Devices Available

Deployment Steps

1. Arteriovenous loop creation — Femoral artery and vein access; a guidewire is passed antegrade from RV → VSD → LV → aorta → captured in femoral artery, creating an arteriovenous loop
2. Sheath positioning — A long delivery sheath is advanced from the venous side through the RV across the VSD into the LV
3. Left ventricular disc deployment — Device LV disc opened in LV
4. Pullback to septum — Device pulled against the LV face of the septum
5. Right ventricular disc deployment — RV disc opens on RV side
6. Confirmation + release — Fluoroscopy and TEE/ICE verify position; no significant residual shunt; device released

Special Consideration — Post-MI VSD

Complications — VSD-specific

• Complete heart block — Higher risk with perimembranous VSD devices (proximity to AV node/bundle of His); reported in ~1–5% of perimembranous closures
• Device embolization
• Hemolysis from residual shunt

3. Patent Ductus Arteriosus (PDA)

What is it?

Devices Available

Deployment Steps (ADO-I — standard approach)

1. Femoral vein access — Catheter advanced RV → pulmonary artery → ductus → descending aorta
2. Aortogram — Defines PDA morphology (Type A = conical, commonest; Types B–F = tubular, window, complex)
3. Sheath positioning — Delivery sheath positioned in the descending aorta via the PDA
4. Retention disc deployment — The aortic retention disc is opened in the descending aorta
5. Pull back into ductus — The device is pulled into the PDA; the pulmonary end (plug portion) sits in the PDA ampulla
6. Confirmation — Aortogram confirms no protrusion into pulmonary artery or aorta; no significant residual shunt
7. Release

4. How to Measure Septal/Defect Size to Select the Appropriate Device

A. Echocardiographic Measurement (First Step — Always)

• Transthoracic echocardiography (TTE) — Initial assessment, especially in children
• Transesophageal echocardiography (TEE) — Standard of care for intraprocedural guidance; multiplane views at 0°, 45°, 90°, 135°
• Intracardiac echocardiography (ICE) — Increasingly used in adults; allows procedure without general anesthesia
• 3D echocardiography — Most accurate for true defect geometry; allows en face "surgical" view of septum

• Maximum ASD diameter in multiple planes (defects are often oval)
• Rim assessment — Distance from defect edge to: coronary sinus, IVC, SVC, right upper pulmonary vein, AV valves, aorta (retroaortic rim)
• Total septal length — Device disc must not exceed it
• Rims <5 mm to critical structures = relative contraindication for ASO (but GCA can still be used for deficient retroaortic rim)

B. Balloon Sizing — Stretched Diameter (Gold Standard for ASD)

1. A sizing balloon (e.g., NuMED Sizing Balloon) is advanced across the ASD
2. The balloon is gradually inflated with dilute contrast under fluoroscopy and echo guidance
3. Inflation continues until left-to-right flow ceases (color Doppler shows no flow through defect) — the "stop-flow" endpoint
4. The balloon diameter at this point = stretched diameter
5. Avoid over-inflation — do not inflate >1.5× the static echocardiographic dimension (to minimize erosion risk)

• ASO: Choose device = same size OR at most 1 mm larger than the stop-flow stretched diameter
• For defects with deficient retroaortic rim (<5 mm): use stop-flow sizing carefully; GCA is preferred as it carries no erosion risk
• ASD criteria for device closure: minimum diameter >5 mm, maximum stretched diameter <40–41 mm

C. Angiographic Sizing (PDA)

• Lateral aortogram (90° projection) with catheter in the ampulla of the ductus
• Measure: narrowest PDA diameter (pulmonary end), length of the ductus, and ampulla diameter (aortic end)
• ADO-I device selection: device diameter should be 1–2 mm larger than the narrowest PDA diameter; device length should match PDA length
• ADO-II: device diameter = 2× the narrowest PDA diameter

D. VSD Sizing

• Echo measurement: 2D TTE/TEE measures defect in multiple views
• Balloon sizing may be performed for large muscular VSDs
• Amplatzer muscular VSD occluder size = stretched diameter + 1–2 mm (to ensure adequate coverage of both LV and RV faces)

Summary Table — Device Selection Rules

Key Complications Across All Three