Size Cutoff for ASD Treatment
The decision to treat an ASD is not based on a specific size cutoff alone, but rather on the presence of right ventricular volume overload, regardless of symptoms, with closure indicated for all hemodynamically significant defects when pulmonary vascular resistance remains <5 Wood units. 1
Primary Indication: Hemodynamic Significance Over Absolute Size
The fundamental criterion for ASD closure is evidence of right ventricular volume overload, not a specific diameter measurement. 1 This represents a paradigm shift from size-based decision-making to physiologic assessment. The European Society of Cardiology guidelines establish that patients with significant shunt (signs of RV volume overload) and PVR <5 Wood units should undergo ASD closure regardless of symptoms (Class I, Level B). 1
Size Categories and Clinical Context
While size alone doesn't dictate treatment, it provides important context:
Small defects: ASDs ≤2.0 cm are classified as small, with only 4-6% developing Eisenmenger syndrome. 1 However, even small defects (<5 mm) may require closure if associated with paradoxical embolism. 2
Large defects: ASDs >2.0 cm are classified as large, with approximately 10% of patients developing pulmonary arterial hypertension. 1
Device closure feasibility: Secundum ASDs with stretched diameter <38 mm and sufficient rim (≥5 mm except toward the aorta) are suitable for transcatheter closure in approximately 80% of patients. 1 The AMPLATZER device can successfully close defects up to 38 mm, while the HELEX device is limited to ≤18 mm defects. 1, 3
Critical Hemodynamic Thresholds
Absolute contraindications exist based on pulmonary vascular resistance:
**PVR ≥5 Wood units but <2/3 systemic vascular resistance** with evidence of net left-to-right shunt (Qp:Qs >1.5) may be considered for intervention (Class IIb). 1
Eisenmenger physiology (PVR ≥2/3 systemic) is an absolute contraindication to closure (Class III). 1
Age-Related Considerations for Timing
Optimal outcomes occur with repair before age 25 years, as surgery after this age results in reduced survival compared to age-matched controls. 4 However, patients benefit from closure at any age regarding morbidity (exercise capacity, dyspnea, right heart failure), particularly when performed before age 40. 1 Closure after age 40 does not affect arrhythmia frequency but still improves functional status. 1, 4
Special Circumstances Warranting Closure
Paradoxical embolism: All ASDs regardless of size should be considered for intervention in patients with suspected paradoxical embolism after excluding other causes (Class IIa). 1
Common Pitfalls to Avoid
Never delay closure based solely on absence of symptoms, as symptoms lag behind objective cardiopulmonary dysfunction. 4 Nearly 25% of patients with unoperated ASDs die before age 27, and 90% by age 60, making timely closure essential even in asymptomatic patients. 4
Do not rely on size measurements alone without assessing RV volume overload through echocardiography, which should demonstrate RV dilation and volume overload as the key hemodynamic finding. 1
Avoid attempting closure in patients with advanced pulmonary vascular disease, as this represents a Class III contraindication. 3