What is the location of a supracristal (above the crista supraventricularis) Ventricular Septal Defect (VSD)?

Location of a Supracristal Ventricular Septal Defect

A supracristal ventricular septal defect (VSD) is located in the outflow portion of the right ventricle, specifically opening to the outlet of the right ventricle between or above the limbs of the septal band. 1

Anatomical Classification of VSDs

VSDs are classified into four main anatomical types based on their location in the ventricular septum:

1. Outlet/Supracristal VSD (Type 1)

   • Located in the outflow portion of the right ventricle
   • Opens to the outlet of the right ventricle between or above the limbs of the septal band 1
   • Also known as conal or subpulmonary VSD
   • Accounts for approximately 6% of VSDs in non-Asian populations but up to 33% in Asian patients 1
   • Spontaneous closure is uncommon 1

2. Perimembranous VSD (Type 2)

   • Most common type (approximately 80% of VSDs)
   • Located in the membranous septum
   • Adjacent to the septal leaflet of the tricuspid valve 1

3. Inlet VSD (Type 3)

   • Located in the lower part of the right ventricle
   • Adjacent to the tricuspid valve
   • Commonly associated with Down syndrome 1

4. Muscular VSD (Type 4)

   • Located within the trabeculated component of the ventricular septum
   • Can be central (mid-muscular), apical, or at the margin of the septum 1

Clinical Significance of Supracristal VSDs

Supracristal VSDs have unique clinical implications:

• High risk of aortic valve complications: The absence of a portion of the conal septum can lead to prolapse of the right cusp of the aortic valve, predisposing patients to aortic insufficiency 2
• Progression of aortic regurgitation: In the case of an outlet (supracristal) VSD, there is a substantial risk for prolapse of the right coronary (or non-coronary) cusp of the aortic valve, resulting in progressive aortic regurgitation 1
• Surgical approach: The preferred surgical approach for supracristal VSDs is through the pulmonary artery, which allows the best exposure of the remaining conal septum and the pulmonary and aortic valve leaflets 2
• Early intervention: Due to the risk of progressive aortic insufficiency, early closure of supracristal VSDs is recommended regardless of shunt volume 2

Diagnostic Evaluation

Echocardiography-Doppler is the mainstay of diagnosis for VSDs, providing information about:

• Location and size of the defect
• Presence of aortic valve prolapse or regurgitation
• Chamber sizes and ventricular function
• Presence of right or left ventricular outflow obstruction 1

Management Considerations

• Patients with VSD-associated prolapse of an aortic valve cusp causing progressive aortic regurgitation should be considered for surgery (Class IIa recommendation) 1
• Early closure is particularly important for supracristal VSDs to prevent progressive aortic insufficiency, even if the shunt is not hemodynamically significant 2

Understanding the precise location of a supracristal VSD is crucial for appropriate management decisions, particularly given its association with aortic valve complications and the need for specific surgical approaches.