Ventricular Septal Defect (VSD)

Why is this topic important?

Ventricular Septal Defect (VSD) is the commonest congenital heart defect and one of the highest-yield cardiology topics in MRCPCH examinations.

Candidates are expected to:

Understand the pathophysiology of left-to-right shunts
Recognise the characteristic murmur
Understand why symptoms develop several weeks after birth
Identify complications
Know indications for treatment and follow-up

VSD frequently appears in MRCPCH clinical scenarios involving infants with poor feeding, failure to thrive, recurrent chest infections and heart murmurs.

Definition

A Ventricular Septal Defect (VSD) is an abnormal communication between the left and right ventricles caused by a defect in the interventricular septum.

The defect allows blood to flow from the:

Left Ventricle → Right Ventricle

This is known as a left-to-right shunt.

Key MRCPCH Facts

VSD is the commonest congenital heart defect.
Most small VSDs close spontaneously.
Symptoms usually appear after the first few weeks of life.
Large VSDs may cause heart failure.
The classic murmur is a pansystolic murmur.
Pulmonary hypertension is a major long-term complication.
Untreated severe VSD may eventually lead to Eisenmenger syndrome.

Anatomy

The ventricular septum consists of:

Membranous Septum

Most common site of VSD.

Muscular Septum

May contain multiple defects.

Inlet Septum

Located near the atrioventricular valves.

Outlet Septum

Located near the ventricular outflow tracts.

For MRCPCH purposes, candidates should know:

Membranous VSDs are most common.
Muscular VSDs have a higher likelihood of spontaneous closure.

Pathophysiology

Normal Physiology

The left ventricle normally operates at a much higher pressure than the right ventricle.

What Happens in VSD?

Blood passes from:

Left ventricle → Right ventricle

because left ventricular pressure is higher.

This causes:

Increased pulmonary blood flow
Increased left atrial volume
Increased left ventricular volume
Pulmonary congestion

Why Symptoms Develop Later

At birth:

Pulmonary vascular resistance is naturally high.

Therefore shunting may initially be limited.

Over the first few weeks:

Pulmonary vascular resistance falls.

This increases left-to-right shunting and symptoms begin to appear.

This is a favourite MRCPCH examination concept.

Classification

Small VSD

Minimal shunting
Usually asymptomatic
Often closes spontaneously

Moderate VSD

Moderate shunting
May cause mild symptoms

Large VSD

Significant left-to-right shunt
Heart failure
Poor growth
Pulmonary hypertension

Clinical Features

Small VSD

Often discovered incidentally.

Features:

Asymptomatic
Normal growth
Loud murmur

Moderate to Large VSD

Symptoms often develop between:

4–8 weeks of age

Features include:

Feeding Difficulties

Tires during feeds
Sweating during feeds

Respiratory Symptoms

Tachypnoea
Recurrent chest infections

Growth Problems

Poor weight gain
Failure to thrive

Heart Failure

Hepatomegaly
Respiratory distress
Poor feeding

Examination Findings

Murmur

Classic finding:

Pansystolic Murmur

Characteristics:

Harsh quality
Left lower sternal edge
Often loud

Additional Findings

Large VSD:

Tachycardia
Hyperdynamic precordium
Cardiomegaly
Hepatomegaly

Important MRCPCH Concept

Small Defect = Loud Murmur

Large Defect = Softer Murmur

This appears counterintuitive.

A small defect creates greater turbulence and therefore a louder murmur.

A very large defect may produce less turbulence and a quieter murmur.

This is a common MRCPCH exam trap.

Differential Diagnosis

Other Left-to-Right Shunts

Patent Ductus Arteriosus
Atrial Septal Defect
Atrioventricular Septal Defect

Other Murmurs

Innocent murmurs
Pulmonary stenosis
Aortic stenosis

Investigations

Pulse Oximetry

Usually normal in uncomplicated VSD.

ECG

May demonstrate:

Left ventricular hypertrophy
Biventricular hypertrophy in larger defects

Chest X-Ray

Large VSD may show:

Cardiomegaly
Increased pulmonary vascular markings

Echocardiography

Gold Standard Investigation

Provides:

Size of defect
Location
Degree of shunting
Pulmonary pressures
Associated abnormalities

Management

Small VSD

Most require:

Observation
Regular follow-up

Many close spontaneously.

Medical Management

If heart failure develops:

Diuretics
Nutritional support

Examples:

Furosemide
Spironolactone

Surgical Closure

Consider if:

Significant symptoms
Failure to thrive
Pulmonary hypertension
Persistent large defect

Catheter Closure

Possible for selected defects.

Complications

Short-Term

Heart failure
Recurrent respiratory infections
Poor growth

Long-Term

Pulmonary hypertension
Aortic valve prolapse
Aortic regurgitation
Arrhythmias

Eisenmenger Syndrome

Occurs when long-standing pulmonary hypertension causes reversal of shunt:

Right-to-left shunt develops.

Results in:

Cyanosis
Clubbing
Reduced exercise tolerance

This is a major MRCPCH concept.

Common Exam Traps

Trap 1

VSD is the commonest congenital heart defect.

Trap 2

Symptoms usually appear several weeks after birth.

Trap 3

Small VSDs often produce louder murmurs.

Trap 4

Large VSDs cause heart failure.

Trap 5

Most small VSDs close spontaneously.

Trap 6

Eisenmenger syndrome is a late complication.

Trap 7

Echocardiography is the diagnostic gold standard.

One Minute Revision

Commonest congenital heart defect.
Left-to-right shunt.
Pansystolic murmur at left lower sternal edge.
Symptoms develop after pulmonary vascular resistance falls.
Small VSD = loud murmur.
Large VSD = heart failure.
Echocardiography confirms diagnosis.
Watch for pulmonary hypertension and Eisenmenger syndrome.

Suggested References

NICE Guidance
RCPCH Guidance
BNF for Children
Nelson Textbook of Pediatrics
Illustrated Textbook of Paediatrics
Park's Pediatric Cardiology for Practitioners
Moss & Adams' Heart Disease in Infants, Children and Adolescents

Disclaimer

These notes are intended for MRCPCH revision and educational purposes only. They do not replace local, national or institutional guidelines. Clinical decisions should always be based on current guidance, senior advice and individual patient circumstances.

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