At what size should an atrial septal defect (ASD) be closed?

ASD Closure Based on Size

ASDs less than 5 mm without right ventricular volume overload do not require closure unless paradoxical embolism is present, while defects with evidence of RV enlargement should be closed regardless of absolute size measurement. 1, 2, 3

Size-Based Decision Framework

Small Defects (<5 mm)

• Do not close defects <5 mm diameter when there is no evidence of RV volume overload, as these do not impact natural history 1, 2, 3
• Exception: Consider closure even in small defects if paradoxical embolism has occurred (after excluding other causes) 1, 2, 3
• Spontaneous closure occurs in 81% of infants with small defects (<6 mm) 4

The Critical Distinction: Size vs. Hemodynamic Impact

The presence of right atrial and RV enlargement is the primary indication for closure, not the absolute defect size. 1, 2, 3 This represents a fundamental shift from size-based to hemodynamic-based decision making.

Class I Indication (Must Close):

• Any ASD with signs of RV volume overload on echocardiography, regardless of symptoms 1, 3
• Significant shunt defined as Qp:Qs ≥1.5:1 with RV enlargement and pulmonary vascular resistance <5 Wood units 1, 2

Larger Defects (>5 mm)

Defects demonstrating RV volume overload should undergo closure to prevent long-term complications including atrial arrhythmias, reduced exercise tolerance, hemodynamically significant tricuspid regurgitation, and pulmonary vascular disease that develops in 5-10% of affected individuals 1, 3

Device Closure Feasibility:

• Most secundum ASDs can be closed percutaneously when stretched diameter is <38 mm and adequate rim (≥5 mm except toward aorta) is present 1, 5
• This applies to approximately 80% of secundum defects 1
• Defects 6-9 mm may regress in infants and children but rarely close spontaneously 4
• Defects >10 mm have little chance of spontaneous closure and typically require intervention 4

Critical Hemodynamic Contraindications

Absolute contraindication: Severe irreversible pulmonary arterial hypertension with no evidence of left-to-right shunt (Eisenmenger physiology) 1

Pulmonary Pressure Thresholds:

• Safe to close: PA systolic pressure <50% of systemic pressure and PVR <1/3 systemic vascular resistance 2
• Gray zone (requires expert evaluation): PA pressure 50-67% of systemic or PVR 1/3 to 2/3 systemic resistance with net left-to-right shunt 1, 2
• Do not close: PA pressure >2/3 systemic, PVR >2/3 systemic resistance, or net right-to-left shunt 2

Common Pitfalls to Avoid

Do not assume small shunts remain benign in older adults. Acquired conditions (hypertension, diastolic dysfunction, coronary disease) can increase left-to-right shunting over time, making previously insignificant ASDs hemodynamically relevant 2

The most critical assessment is excluding severe pulmonary vascular disease before closure, as closure with established severe PAH causes acute RV failure and death 2

Sinus venosus, coronary sinus, and primum defects are not amenable to device closure and require surgical repair regardless of size 1, 3, 5

Special Anatomic Considerations

For secundum ASDs considered for device closure, transesophageal echocardiography should assess rim size and quality, exclude additional defects, and confirm normal pulmonary venous connection 1

Large septal aneurysms or multifenestrated atrial septa require careful evaluation by interventional cardiologists before selecting device closure as the repair method 1