What are the types, echo findings, and management of Ventricular Septal Defects (VSDs)?

Ventricular Septal Defects: Types, Echo Findings, and Management

Ventricular septal defects (VSDs) are classified into four main anatomical types based on location, with specific echocardiographic findings guiding management decisions that primarily depend on defect size, hemodynamic significance, and associated complications. 1, 2

Types of VSDs

Anatomical Classification

• Membranous (Perimembranous): Most common type (approximately 80% of defects), located at the center of the base of the ventricular mass, occupying the space usually closed by the interventricular part of the membranous septum, adjacent to the area of fibrous continuity between atrioventricular and arterial valve leaflets 1, 2
• Muscular (Trabecular): Located within the trabeculated component of the ventricular septum, may be single or multiple, and have a high rate of spontaneous closure 1, 2
• Outlet (Supracristal): Opens to the outlet of the right ventricle between or above the limbs of the septal band, represents approximately 6% of defects in non-Asian populations and up to 33% in Asian patients 1, 2
• Inlet: Opens predominantly into the inlet component of the right ventricle in the absence of a common atrioventricular junction, typically found in patients with Down syndrome 1, 2

Quantitative Classification

• Single vs Multiple: VSDs can be classified as single (one defect) or multiple (several defects of potentially different types) 1
• Size Classification:
  • Small: Hemodynamically insignificant 1
  • Moderate to large: Hemodynamically significant 1

Echocardiographic Findings

Essential Echo Parameters

• Number, size, and location of defects: Primary assessment to classify the VSD type and determine hemodynamic significance 1
• Left and right ventricular function: Assess for ventricular dilation and dysfunction 1
• Aortic regurgitation: Particularly important in perimembranous and outlet defects due to risk of aortic valve prolapse 1
• Quantitative measurements:
  • VSD area >50 mm²/m² at initial diagnosis is independently associated with need for surgical intervention 3
  • Left atrial volume, LV end-diastolic diameter, and pulmonary-to-systemic flow ratio (Qp:Qs) are significantly different between surgical and non-surgical cases 3

Additional Echo Findings

• Perimembranous VSDs: May show "aneurysm" formation when tricuspid valve adheres to the defect 2
• Muscular VSDs: May be centrally located, apical, or at the margin of the septum and free wall of the right ventricle 2
• Transesophageal echocardiography (TOE): Indicated when transthoracic images are inadequate 1

Management

Indications for Intervention

• Left-to-right shunt with left heart volume overload: Indicated by enlarged left atrium and ventricle 1, 4
• Reversible pulmonary hypertension: Intervention needed before development of pulmonary vascular obstructive disease 1
• Aortic regurgitation: Requires intervention to prevent progression 1
• Associated abnormalities: Such as right ventricular outflow tract obstruction or subaortic stenosis 1
• Previous endocarditis: History of endocarditis is an indication for closure 1
• Qp:Qs ratio >2:1: Indicates significant shunting requiring intervention 5

Intervention Options

Surgical Closure

• Recommended for:
  • Perimembranous VSDs (surgical approach preferred due to risk of heart block with device closure) 4, 5
  • Supracristal (outlet) VSDs 4, 5
  • Inlet VSDs 4, 5
  • VSDs with aortic valve prolapse 4, 5
  • Large defects (>10 mm) unless irreversible pulmonary vascular disease is present 1

Catheter Closure

• Recommended for:
  • Muscular VSDs: Can be closed using Amplatzer Muscular VSD Occluder (the only FDA-approved device for this purpose) 4, 5
  • Caution: Percutaneous closure of perimembranous VSDs carries a significant risk of complete heart block 4

Hybrid Approach

• Combination of surgical and catheter techniques may be used for large muscular VSDs in small infants 5

Management Based on VSD Size

Small VSDs

• Approach: Generally require no intervention 1, 4, 6
• Follow-up: Infrequent follow-up unless hemodynamic abnormalities develop 1
• Sports/Activity: No restrictions 1
• Endocarditis prophylaxis: Recommended 1

Moderate to Large VSDs

• Approach: Surgical or catheter-based intervention based on VSD type 1, 4, 5
• Timing: Early intervention recommended to prevent pulmonary vascular disease 5, 6
• Follow-up: Regular monitoring for residual shunts, ventricular function, aortic regurgitation, and new hemodynamic abnormalities 1

Special Considerations

• Eisenmenger syndrome: Patients with large unrepaired VSDs may develop irreversible pulmonary vascular disease 1
• Pregnancy: No contraindications in uncomplicated VSDs; contraindicated in pulmonary vascular disease 1
• Spontaneous closure: Common in muscular VSDs, less frequent in other types 2, 6

Common Pitfalls and Caveats

• Unnecessary intervention for small VSDs: Small defects generally have good outcomes without intervention 4, 6
• Delayed intervention for large VSDs: Can lead to irreversible pulmonary vascular disease 4, 5
• Incomplete assessment: Always evaluate for associated lesions, particularly aortic valve prolapse 1
• Post-intervention monitoring: Even after successful closure, patients may develop RV or LV outflow tract obstruction or aortic regurgitation 1