Small, Moderate or Large VSD: How to Understand Your Echo Report and Know When Closure May Be Needed

If your child or a family member has been diagnosed with a Ventricular Septal Defect (VSD) and you are trying to make sense of the echo report, you are not alone. One of the first questions most families ask is, “What size of Ventricular Septal Defect (VSD) requires surgery?” 

The honest answer is that the size of the defect matters, but it is only a part of the picture. 

This guide walks you through what the echo findings actually mean and when VSD closure surgery becomes necessary.

What Is Vascular Septal Defect (VSD)?

A ventricular septal defect is a hole in the wall (septum) that separates the two lower chambers of the heart. The oxygenated blood from the left ventricle leaks back into the right ventricle, making the heart work harder than it should. VSD is the most common congenital heart defect found in children and also appears in adults.

Not all ventricular septal defects are the same. They vary in size, location, and how much they affect heart function. All three factors together determine whether the defect needs to be closed or can simply be monitored.

What Does VSD Size Mean in an Echo Report?

When a cardiologist orders an echocardiogram, one of the key measurements reported is the size of the VSD in millimetres. 

Here is how sizes are generally interpreted:

Small VSD (typically less than 3 to 5 mm)

• Causes minimal left-to-right shunting
• Rarely causes symptoms
• Does not significantly overload the heart
• Often discovered incidentally during a routine check-up
• Many small VSDs close on their own during childhood

Moderate VSD (typically 5 to 10 mm)

• Causes noticeable left-to-right shunting
• May lead to some degree of left ventricular volume overload
• A child may show mild symptoms such as faster breathing or slightly slower weight gain
• Requires close monitoring and may or may not need closure

Large VSD (typically greater than 10 mm)

• Causes significant left-to-right shunting
• Can lead to heart failure, poor weight gain, and recurrent respiratory infections
• Often requires surgical or catheter-based closure

These are general ranges. The exact thresholds can vary depending on the patient’s body size, age, and overall cardiac anatomy.

Small vs Moderate vs Large VSD: What Changes With Each?

VSD Size	Shunting	Symptoms	Action Typically Needed
Small (less than 3 to 5 mm)	Minimal	Usually none	Monitor; may close on its own
Moderate (5 to 10 mm)	Moderate	Mild to moderate	Monitor closely; closure if needed
Large (greater than 10 mm)	Significant	Heart failure, poor growth	Closure usually recommended

What Size of VSD Requires Surgery or Closure?

Here is the clinical reality:

1. Large VSDs almost always require closure. If a large defect does not reduce in size within the first few months of life, VSD closure surgery is typically recommended before six months of age to prevent pulmonary hypertension and irreversible damage to the lung blood vessels.
   
2. Moderate VSDs may require VSD closure surgery if:

• The child is not growing adequately despite medical management
• There is evidence of left-sided heart enlargement on the echo.
• The child has recurrent respiratory infections or persistent heart failure symptoms.
• Medical treatment is not controlling the symptoms.
  

3. Small VSDs generally do not require surgery. However, there are exceptions:

• A perimembranous (near the aortic valve) VSD, even if small, may require closure if it causes aortic valve leaflet prolapse or leakage.
• Any VSD, regardless of size, that is causing progressive valve damage should be evaluated for closure.

The key takeaway: size alone does not determine the need for VSD surgery. The echo findings need to be interpreted alongside symptoms, heart chamber sizes, pulmonary artery pressure, and the ratio of pulmonary to systemic blood flow.

Ventricular Septal Defect in Children vs. Adults

In children, the approach is primarily driven by growth, symptoms, and the risk of developing pulmonary hypertension. Infants with large VSDs who are not growing are prioritised for early VSD closure surgery. Older children with moderate defects and left ventricular dilation are also strong candidates.

In adults, VSDs are less commonly encountered, but when they are, the evaluation is different. Adults with small, restrictive VSDs and normal pulmonary pressure and no symptoms may be monitored without intervention. However, adults with a history of untreated moderate to large VSDs may present with pulmonary hypertension, arrhythmias, or reduced exercise capacity, all of which change the management approach significantly.

In both age groups, an echocardiogram remains the primary tool for decision-making.

What Are The Red Flags That Need Specialist Review?

Seek a cardiology opinion promptly if the child or adult with a known VSD shows any of the following:

• Poor weight gain or feeding difficulties in infants
• Frequent chest infections or breathlessness
• Bluish discolouration of lips or fingertips
• Reduced exercise tolerance compared to peers
• A new or changing heart murmur
• Swelling of the legs or abdomen in adults

What Happens After a Doctor Recommends VSD Closure?

If your cardiologist recommends closure, the next step is determining which approach is best suited for the specific defect:

• Surgical VSD closure:
  Done under general anaesthesia with cardiopulmonary bypass. A patch or suture is used to close the defect.
  
• Catheter-based device closure:
  A minimally invasive option where a small occluder device is delivered through a catheter via the femoral vein and deployed across the defect. Suitable for select perimembranous and muscular VSDs meeting specific anatomical criteria.

The choice between the two depends on the defect’s size, location, proximity to valves, and the patient’s overall health.

Post-closure, most patients recover well. Infants typically stay in the hospital for five to seven days after open surgery, while catheter-based closure allows discharge in two to three days. Long-term outcomes are excellent when closure is done at the right time.

Connect With Our Team at Heart Valve Experts

Understanding a Ventricular Septal Defect (VSD) diagnosis and deciding the right course of action requires more than just reading an echo report. Heart Valve Experts connects patients and families with experienced congenital and structural heart specialists who can evaluate your specific case, explain what the findings mean, and guide you on whether monitoring or VSD closure surgery is the right step. If you have questions or need a second opinion, reach out to the Heart Valve Experts team for a consultation.

Frequently Asked Questions

1. Can a VSD close on its own without surgery?
   Yes, many small VSDs and some moderate ones close spontaneously, especially during the first two years of life. Regular echo follow-up helps track this.
   
2. At what age is VSD surgery usually done?
   For large VSDs causing symptoms, surgery is typically done within the first six months. For moderate VSDs, the timing depends on symptoms and echo findings. There is no strict age limit for surgery.
   
3. Is VSD closure surgery risky?
   Surgical VSD closure is a well-established procedure with high success rates. Risks are low at experienced cardiac centres and outcomes are generally very good.
   
4. Can adults live with an unrepaired VSD?
   Adults with small, restrictive VSDs and no complications can live without closure under regular monitoring. Those with moderate or large unrepaired VSDs may develop complications over time and need specialist evaluation.