What are the indications for atrial septal defect (ASD) closure?

Indications for Atrial Septal Defect (ASD) Closure

Closure of secundum ASD is indicated in adults with right atrial and/or right ventricular enlargement, with or without symptoms, when Qp:Qs ≥1.5:1, pulmonary artery systolic pressure is <50% of systemic pressure, and pulmonary vascular resistance is <1/3 of systemic resistance (<5 Wood units). 1, 2

Primary Hemodynamic Indications (Class I)

Right heart enlargement with significant shunt:

• Right atrial and/or right ventricular enlargement documented by echocardiography is the primary indication for closure, regardless of symptom status. 3, 1, 2 This is critical because symptoms lag behind objective cardiopulmonary dysfunction and cannot reliably guide therapy. 1
• Qp:Qs ratio ≥1.5:1 with evidence of RV volume overload warrants closure. 1, 2
• PA systolic pressure must be <50% of systemic pressure. 1, 2
• PVR must be <1/3 of systemic vascular resistance (<5 Wood units). 1, 2

The rationale for closure even in asymptomatic patients is compelling: Nearly 25% of patients with unoperated ASDs die before age 27, and 90% by age 60. 1 Surgery performed after age 25 results in reduced survival compared to age-matched controls, emphasizing the importance of earlier intervention. 1

Clinical Symptom-Based Indications (Class I)

Symptomatic patients with any of the following:

• Impaired functional capacity (dyspnea, fatigue, exercise intolerance). 4, 5
• Congestive heart failure symptoms. 4
• Palpitations related to atrial arrhythmias. 4

These symptoms develop from progressive RV volume overload leading to right heart failure and age-related atrial arrhythmias with increased thromboembolic risk. 1

Special Clinical Scenarios (Class IIa)

Paradoxical embolism:

• Closure is reasonable when paradoxical embolism has occurred (transient ischemic attack or stroke), after excluding other embolic sources. 3, 2
• This applies even to smaller defects if embolic events are documented. 3

Orthodeoxia-platypnea syndrome:

• Closure is reasonable in patients with transient right-to-left shunting causing symptomatic cyanosis who do not require the communication to maintain adequate cardiac output. 3

Concomitant cardiac surgery:

• Surgical ASD closure is reasonable during another cardiac procedure if Qp:Qs ≥1.5:1 and RV enlargement are present, even if the ASD was not the primary surgical indication. 2

Borderline Pulmonary Hypertension (Class IIb)

Closure may be considered with extreme caution when:

• PA systolic pressure is 50-67% of systemic pressure AND/OR
• PVR is 1/3 to 2/3 of systemic resistance AND
• Net left-to-right shunt (Qp:Qs ≥1.5:1) is still present AND
• Evidence of pulmonary vascular reactivity exists. 2

This requires mandatory evaluation by pulmonary hypertension specialists before proceeding. 1, 2 Test occlusion or vasodilator responsiveness testing may guide decision-making. 2

Absolute Contraindications (Class III)

Do not close ASD when:

• Severe irreversible pulmonary arterial hypertension with no evidence of left-to-right shunt (Eisenmenger physiology) is present. 3, 2, 6
• PA systolic pressure >2/3 of systemic pressure. 2, 6
• Net right-to-left shunt exists. 2, 6

Closure with established severe pulmonary vascular disease causes acute RV failure and death. 2 This is the most critical assessment to avoid catastrophic outcomes.

Defects That Do NOT Require Closure

Small ASDs (<5-10 mm) without RV volume overload generally do not require closure unless associated with paradoxical embolism. 3, 2 These defects do not impact natural history and remain stable throughout the patient's life. 2

Closure Method Selection

Percutaneous device closure:

• Preferred method for secundum ASDs when anatomically suitable. 3, 1
• Suitable anatomy includes stretched diameter <38 mm with adequate rim ≥5 mm in most locations (except toward the aorta where smaller rim is acceptable). 1, 6
• Success rate is 97% for defects 20-39 mm, but only 17% for extreme defects ≥40 mm. 7
• Serious complications occur in ≤1% of patients. 1

Surgical closure is required for:

• Sinus venosus defects. 3, 2
• Coronary sinus defects. 3, 2
• Primum ASDs. 3, 2
• ASDs with anomalous pulmonary venous drainage. 2
• Large secundum ASDs not amenable to device closure (stretched diameter ≥38-40 mm). 6, 7

Surgeons with training and expertise in congenital heart disease should perform these operations. 3, 2

Critical Pitfalls to Avoid

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

Do not delay closure based on absence of symptoms: Symptoms lag behind objective cardiopulmonary dysfunction. 1 Right heart remodeling can occur even in patients >60 years of age after closure. 4

Do not proceed without excluding severe pulmonary hypertension: This is the most critical assessment, as closure in Eisenmenger physiology is fatal. 2

Expected Outcomes After Closure

Mortality and morbidity:

• Early mortality is approximately 1% in the absence of PAH or major comorbidities. 1, 6
• Closure prevents the progressive mortality seen in natural history studies (25% by age 27,90% by age 60). 1

Functional improvement:

• 89% of patients show improvement in symptoms. 4
• Improvement in NYHA functional class. 1
• RV end-diastolic dimension decreases significantly (from 35-39 mm to 23-27 mm). 4, 5
• Reduction in RV systolic pressure, volumes, and dimensions. 1
• Improved exercise tolerance. 1, 5