What is the management plan for a closed subaortic aneurysmal perimembranous Ventricular Septal Defect (VSD)?

Management of Closed Subaortic Aneurysmal Perimembranous VSD

Surgical closure is recommended for a closed (aneurysmal) perimembranous VSD to prevent life-threatening complications including aortic valve prolapse with progressive aortic regurgitation, infective endocarditis, aneurysm rupture, and right ventricular outflow tract obstruction, even in asymptomatic patients. 1, 2

Understanding the Pathophysiology

The aneurysm of the membranous septum (AMS) in perimembranous VSD represents a unique clinical entity where tissue from the tricuspid valve or membranous septum forms an aneurysmal sac that may partially or completely occlude the VSD. 2 While this functionally reduces shunt size (typically Qp:Qs <2.3), the aneurysm itself creates significant complications that mandate intervention. 2

Key Complications Requiring Intervention

The presence of an aneurysmal perimembranous VSD carries substantial morbidity risk:

• Aortic valve prolapse occurs in 47% of cases, with the right coronary cusp most commonly affected, leading to progressive aortic regurgitation in 29.4% of patients 2
• Infective endocarditis risk increases 6-fold compared to the general population (2 per 1000 patient-years), with 13.7% of patients experiencing bacterial endocarditis 1, 2
• Tricuspid insufficiency develops in 17.6% due to aneurysmal tissue distortion 2
• Right ventricular outflow tract obstruction can occur from the aneurysmal mass 2, 3
• Aneurysm rupture, though rare (2%), represents a catastrophic complication 2

Surgical Indications

Class I Recommendations (Must Perform)

Surgery is indicated for:

• Patients with VSD-associated prolapse of an aortic valve cusp causing progressive aortic regurgitation 1
• Asymptomatic patients with evidence of LV volume overload attributable to the VSD 1
• Symptomatic patients with left-to-right shunting and no severe pulmonary vascular disease 1

Class IIa Recommendations (Should Perform)

Surgery should be considered for:

• Patients with a history of infective endocarditis 1
• All patients with aneurysmal perimembranous VSD to prevent progressive complications, even if currently asymptomatic 2

Surgical Technique

The aneurysm must be completely resected and the defect closed with a patch rather than direct suture closure. 2 Direct suture closure results in:

• Residual communication in some cases 2
• Recurrence of aneurysm formation (documented at 3 and 7 years postoperatively) 2

Concomitant procedures to address:

• Aortic valve repair for mild-to-moderate aortic regurgitation (performed in 13 of 15 patients with AR in one series) 2
• Aortic valve replacement for severe aortic regurgitation per GDMT criteria 1, 2
• Tricuspid valve repair if significant insufficiency present 2

Diagnostic Evaluation

Echocardiography is the key diagnostic modality and must assess: 1

• Location, number, and size of VSD
• Presence and extent of aneurysmal tissue
• Aortic valve morphology and degree of prolapse
• Severity of aortic regurgitation (particularly right coronary cusp)
• LV volume overload and systolic/diastolic function
• Pulmonary artery pressure estimation
• Presence of double-chambered right ventricle
• Right ventricular outflow tract obstruction

Transesophageal echocardiography provides superior anatomic detail for surgical planning, particularly for visualizing the aneurysmal tissue and aortic valve involvement. 4

Critical Pitfalls to Avoid

1. Do not adopt a "watch and wait" approach simply because the VSD is functionally closed by the aneurysm—the aneurysm itself is the problem 2
2. Do not use direct suture closure—this leads to recurrence and residual defects 2
3. Do not miss aortic valve prolapse—carefully examine the right coronary cusp in all cases of perimembranous VSD 1, 2
4. Do not delay surgery until severe aortic regurgitation develops—intervene when AR is progressive to avoid valve replacement 1, 2

Postoperative Follow-up

Annual follow-up is required to monitor for: 1

• Residual or recurrent VSD
• Progressive aortic regurgitation
• Development of complete AV block (rare but requires lifelong pacing)
• LV function
• Pulmonary artery pressures

Contraindications to Surgery

Surgery must be avoided in: 1

• Eisenmenger syndrome with exercise-induced desaturation
• Severe pulmonary vascular disease with PA systolic pressure >2/3 systemic and pulmonary vascular resistance >2/3 systemic 1

Prognosis

Surgical outcomes are excellent with no early or late mortality reported in contemporary series when performed before development of severe complications. 2 However, delaying surgery until severe aortic regurgitation or other complications develop significantly worsens outcomes and may necessitate valve replacement rather than repair. 2