What is the recommended evaluation, treatment, and follow‑up for an atrial septal defect?

Management of Atrial Septal Defect in Adults

Evaluation

All adults with suspected or confirmed ASD require comprehensive echocardiographic assessment to determine right ventricular volume overload, which is the key indicator of hemodynamic significance. 1

Initial Diagnostic Workup

Transthoracic Echocardiography (TTE):

• Right ventricular and right atrial enlargement are the hallmark findings indicating hemodynamically significant shunting 1, 2
• Visualize the entire atrial septum from superior vena cava to inferior vena cava orifice to avoid missing sinus venosus defects 2
• Subcostal views with deep inspiration and high right parasternal views optimize ASD visualization in adults 2
• Fixed splitting of the second heart sound and systolic pulmonary flow murmur are key clinical findings 1
• ECG typically shows incomplete right bundle branch block and right axis deviation (superior left axis deviation in primum ASD) 1

Advanced Imaging:

• Transesophageal echocardiography (TEE) is required for sinus venosus defects, which are commonly missed on TTE, and for precise evaluation before device closure 1, 2
• TEE must assess: defect sizing, residual septum morphology, rim size and quality (≥5 mm except toward aorta), exclusion of additional defects, and confirmation of normal pulmonary venous connections 1, 2
• Cardiac MRI or CT serve as alternatives when echocardiography is insufficient, particularly for RV volume assessment and pulmonary venous connection evaluation 1, 3

Hemodynamic Assessment:

• Pulse oximetry at rest and during exercise is mandatory to determine shunt direction and magnitude 1
• Cardiac catheterization is required when pulmonary artery pressure (PAP) is elevated on echocardiography to determine pulmonary vascular resistance (PVR) 1

Treatment Indications

Secundum ASD

Transcatheter or surgical closure is recommended (Class I) for adults with:

• Impaired functional capacity OR right atrial/RV enlargement 1
• Net left-to-right shunt with Qp:Qs ≥1.5:1 1
• No cyanosis at rest or during exercise 1
• Systolic PA pressure <50% of systemic pressure 1
• PVR <1/3 of systemic vascular resistance 1

Device closure is the preferred method for secundum ASD when anatomically suitable (stretched diameter <38 mm and sufficient rim of 5 mm except toward aorta), which applies to approximately 80% of patients 1

Transcatheter or surgical closure is reasonable (Class IIa) for asymptomatic adults with:

• Isolated secundum ASD with right atrial and RV enlargement 1
• Qp:Qs ≥1.5:1 without cyanosis 1
• Same hemodynamic criteria as above (PA pressure and PVR thresholds) 1

Non-Secundum ASDs

Surgical repair is recommended (Class I) for primum ASD, sinus venosus defect, or coronary sinus defect with:

• Same clinical and hemodynamic criteria as secundum ASD 1
• These defects require surgical rather than transcatheter approach 1

Contraindications

ASD closure must be avoided in patients with Eisenmenger physiology (PVR ≥2/3 systemic vascular resistance or PAP ≥2/3 systemic pressure without evidence of net left-to-right shunt) 1

Patients with PVR ≥5 Wood units but <2/3 systemic vascular resistance may be considered for intervention only if challenged with vasodilators (preferably nitric oxide) or after targeted pulmonary arterial hypertension therapy, and only with evidence of net left-to-right shunt (Qp:Qs >1.5) 1

Procedural Considerations

For transcatheter closure:

• Echocardiographic imaging guidance is required during percutaneous ASD closure 1
• Antiplatelet therapy (aspirin 100 mg daily minimum) is required for at least 6 months post-procedure 1
• Serious complications occur in ≤1% of patients, with essentially zero mortality in recent studies 1

For surgical closure:

• Mortality may be higher in elderly patients and those with comorbidities 1
• Surgical closure is reasonable when a concomitant surgical procedure is being performed and hemodynamic criteria are met 1

Follow-Up

Lifelong follow-up is recommended, particularly for larger defects 4

Post-closure monitoring:

• Follow-up echocardiography is essential to detect residual shunting, which occurs more commonly with complex-shaped defects 5
• Monitor for pericardial effusion post-procedure, as tamponade can occur and requires immediate echocardiographic assessment if hemodynamic deterioration develops 6
• Atrial tachyarrhythmias occurring early after intervention are mostly transient 1

Unrepaired ASDs:

• Frequency of follow-up depends on defect size: small defects at 6-12 month intervals, large defects at 3-6 month intervals 4
• With increasing age and PAP, tachyarrhythmias (atrial flutter, atrial fibrillation) become more common 1
• Life expectancy is reduced in adults with untreated defects, with increased rates of exercise intolerance, atrial tachyarrhythmias, RV dysfunction, and pulmonary hypertension 7

Critical Pitfalls to Avoid

Diagnostic errors:

• Sinus venosus ASDs are commonly missed on TTE due to superior location; patients with unexplained RV volume overload should undergo TEE or alternative imaging 2
• Apparent septal dropout on 2D images may mimic ASD; use contrast echocardiography or TEE to confirm 2
• Two-dimensional TEE can underestimate the area of complex-shaped ASDs by up to 27%, potentially resulting in residual shunting after device closure 5

Procedural risks:

• Meticulous air bubble elimination from all intravenous lines is mandatory, as paradoxical embolism can occur even with predominantly left-to-right shunts 6
• Avoid excessive positive pressure ventilation during anesthesia, as high intrathoracic pressures increase PVR and can precipitate shunt reversal 6