What is the recommended treatment for an atrial septal defect (ASD) with a significant shunt fraction?

Management of Atrial Septal Defect with Shunt Fraction of 1.8

Surgical or transcatheter closure is strongly recommended for an atrial septal defect with a shunt fraction (Qp:Qs) of 1.8:1, as this represents a significant left-to-right shunt that will lead to right heart enlargement and potential complications if left untreated.

Rationale for Intervention

The shunt fraction of 1.8:1 indicates a significant left-to-right shunt that exceeds the threshold of 1.5:1 specified in guidelines for intervention. This level of shunting causes:

• Right ventricular volume overload
• Right atrial enlargement
• Increased risk of developing pulmonary hypertension over time
• Potential for arrhythmias and reduced exercise capacity

Pre-Intervention Assessment

Before proceeding with closure, the following evaluations are essential:

• Pulmonary artery pressure assessment: Ensure systolic PA pressure is <50% of systemic pressure 1
• Pulmonary vascular resistance: Confirm PVR is less than one-third of systemic resistance 1
• Absence of cyanosis: Check oxygen saturation at rest and with exercise 1
• Imaging studies:
  • TEE to evaluate defect size, rim adequacy, and pulmonary venous connections 1
  • CMR or CT if additional anatomical details are needed 1

Intervention Options

1. Transcatheter Device Closure

• First-line option for secundum ASD if anatomically suitable 1
• Requires:
  • Adequate rim of tissue (≥5mm except towards aorta) 1
  • Defect size amenable to device closure (typically <38mm stretched diameter) 1
• Benefits:
  • Shorter hospital stay
  • Avoidance of sternotomy
  • Faster recovery 2

2. Surgical Closure

• Indicated when:
  • Device closure is not feasible (inadequate rims, large defect)
  • Non-secundum ASD (primum, sinus venosus, or coronary sinus defects)
  • Concomitant cardiac surgery is needed 1

Contraindications to Closure

ASD closure should not be performed in patients with:

• PA systolic pressure >2/3 systemic
• Pulmonary vascular resistance >2/3 systemic
• Net right-to-left shunt (Eisenmenger physiology) 1, 3

Special Considerations

Patients with Borderline Elevated Pulmonary Pressures

For patients with PA systolic pressure 50-66% of systemic or PVR 1/3-2/3 of systemic:

• Closure may be considered (Class IIb recommendation) 1, 3
• Evaluation at an expert ACHD center is essential 1
• Consider "treat-and-repair" strategy with PAH-specific therapy before closure 3

Post-Closure Management

• Follow-up at 3 months, 6 months, and 1 year post-closure 3
• Monitor for:
  • Resolution of right heart enlargement
  • Improvement in functional capacity
  • Development of arrhythmias
  • Device-related complications (if applicable) 3

Pitfalls to Avoid

1. Delaying closure: Early intervention prevents development of irreversible pulmonary hypertension and right heart dysfunction 1, 4

2. Inadequate hemodynamic assessment: Failure to properly evaluate pulmonary pressures and resistance can lead to poor outcomes after closure 3

3. Overlooking associated defects: Careful evaluation for anomalous pulmonary venous connections, especially with sinus venosus defects 1

4. Closing defects with severe PAH: This can worsen right heart failure and increase mortality 3

A shunt fraction of 1.8:1 clearly exceeds the guideline threshold of 1.5:1 for intervention, and closure should be pursued to prevent long-term complications related to right heart volume overload.