Define Ventricular Septal Defect. Describe its types, clinical features, investigations and management.

Definition

• A Ventricular Septal Defect (VSD) is an abnormal opening in the interventricular septum that allows communication between the two ventricles.
• It is the commonest congenital heart disease (~30% of all CHD) and is an acyanotic, left-to-right shunt lesion.

Types (BY Location)

• Perimembranous — the commonest type (~70%), in the membranous septum.
• Muscular — in the muscular septum; often multiple; many close spontaneously.
• Inlet (AV-canal type) and outlet (supracristal) defects.

Haemodynamics

Higher LV pressure → blood shunts L → R across the VSD → ↑ Pulmonary blood flow & volume overload of LA/LV → If large & long-standing → pulmonary arterial hypertension → Reversal to R → L shunt = Eisenmenger syndrome (cyanosis)

• The size of the shunt depends on the size of the defect and the pulmonary vascular resistance (PVR).
• A small (restrictive) VSD has a big pressure drop and a small shunt; a large VSD equalises ventricular pressures and produces a large shunt once the neonatal PVR falls.

Clinical Features

• Small VSD: usually asymptomatic; a loud, harsh pansystolic murmur at the left lower sternal border with a thrill (the 'maladie de Roger').
• Large VSD: presents at 6–8 weeks (as PVR falls) with heart failure — poor feeding, sweating, tachypnoea, recurrent chest infections and failure to thrive.
• Signs — pansystolic murmur, precordial thrill/heave, a loud P2 (pulmonary hypertension) and a mid-diastolic mitral flow murmur (large shunt).
• The softer the murmur becomes with a loud single S2, the more one should worry about developing pulmonary vascular disease.

Investigations

• Chest X-ray — cardiomegaly with increased pulmonary vascular markings (plethora) in large shunts; normal in small VSD.
• ECG — normal (small); left or biventricular hypertrophy (large); right ventricular hypertrophy suggests pulmonary hypertension.
• Echocardiography — the investigation of choice; confirms the site, size, shunt direction and haemodynamic effects.
• Cardiac catheterisation — to assess PVR and reversibility in advanced pulmonary hypertension.

Management

• Small VSD: conservative — most close spontaneously; reassurance, follow-up and maintaining good dental/oral hygiene.
• Large VSD with heart failure: anti-failure treatment — diuretics (furosemide), ACE inhibitors, and sometimes digoxin — plus nutritional support (high-calorie feeds) for catch-up growth.
• Definitive: surgical (or device) closure for a large shunt, failure to thrive despite medical therapy, or rising pulmonary pressures — done before irreversible pulmonary vascular disease develops.
• Treat and prevent chest infections; ensure immunisation.

Complications

• Congestive heart failure and recurrent respiratory infections in infancy.
• Pulmonary arterial hypertension → Eisenmenger syndrome (shunt reversal, cyanosis — then inoperable).
• Infective endocarditis; aortic regurgitation (with outlet defects); growth failure.

Prognosis

• Small VSDs have an excellent prognosis and often close on their own.
• Large defects, if corrected early, do well; if left untreated they lead to heart failure and, eventually, irreversible Eisenmenger physiology — hence the importance of timely diagnosis and surgery.

Spectrum BY Size

Differential Diagnosis of a Pansystolic Murmur

• Mitral regurgitation (apical, radiating to axilla), tricuspid regurgitation.
• The VSD murmur is loudest at the left lower sternal border and is harsh.

Associated Conditions

VSD may be isolated or part of syndromes (e.g. Down syndrome — AV-canal type) and complex lesions (Tetralogy of Fallot, truncus arteriosus).

Infective Endocarditis Prophylaxis

Good oral/dental hygiene is essential; antibiotic prophylaxis before certain procedures is reserved for high-risk situations as per current guidelines.

Eisenmenger Syndrome (the Feared End-stage)

• A large, uncorrected VSD keeps the pulmonary arteries exposed to high pressure & flow, causing irreversible pulmonary vascular disease.
• Pulmonary pressure eventually exceeds systemic pressure and the shunt reverses to right-to-left — the child becomes cyanosed and inoperable.
• This is why large shunts must be closed early.

Clinical Monitoring

• Track growth, feeding, respiratory infections and signs of heart failure.
• Serial echocardiography for shunt size and pulmonary pressures; refer for closure before pulmonary vascular disease sets in.