Ventricular Septal Defect (VSD)

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Ventricular Septal Defect (VSD)


Description

Ventricular septal defect (VSD) is a congenital cardiac anomaly characterized by an abnormal opening in the interventricular septum, permitting abnormal communication between the left and right ventricles. This results in left-to-right shunting of blood due to higher systemic (LV) pressures compared to pulmonary (RV) pressures.

Epidemiology

  • Most common congenital heart defect, occurring in approximately 4 per 1000 live births.

  • May present as an isolated lesion or in association with other congenital heart diseases, such as:

    • Atrioventricular septal defect (AVSD)

    • Tetralogy of Fallot

    • Transposition of the great arteries (TGA)

  • Frequently diagnosed in infancy or early childhood during routine evaluation for murmurs or symptoms of heart failure.

Etiology

  • Genetic associations:

    • Trisomy 21 (Down syndrome)

    • Trisomy 18 (Edward syndrome)

    • Trisomy 13 (Patau syndrome)

    • Cri-du-chat syndrome

    • Apert syndrome

  • Environmental & maternal risk factors:

    • Intrauterine infections (TORCH: toxoplasmosis, rubella, cytomegalovirus, herpes, syphilis)

    • Maternal diabetes mellitus

    • Maternal obesity

    • Cigarette smoking

  • May also occur sporadically without identifiable genetic or environmental triggers.

Pathophysiology

  • Most commonly located in the membranous portion of the interventricular septum (pars membranacea).

  • Hemodynamic consequences:

    1. Left-to-right shunting across the defect.

    2. Right ventricular volume overload → RV eccentric hypertrophy.

    3. Excessive pulmonary blood flow → ↑ pulmonary artery pressure → pulmonary hypertension.

    4. Left-sided changes: LV volume overload → LV eccentric hypertrophy.

    5. Reduced systemic cardiac output (blood recirculates to the pulmonary circuit).

  • Oxygen saturation findings: step-up in O₂ saturation from right atrium → right ventricle → pulmonary artery.

Clinical Features

General manifestations

  • Small VSDs: usually asymptomatic, often detected incidentally.

  • Medium or large VSDs:

    • Become symptomatic after pulmonary vascular resistance (PVR) falls in the first weeks to months of life.

    • Decrease in PVR → greater left-to-right shunting → onset of symptoms.

    • Clinical features of heart failure in infants: tachypnea, feeding difficulties, failure to thrive, diaphoresis, recurrent respiratory infections.

  • Hyperdynamic precordium may be palpable in significant defects.

Auscultation findings

  • Classic murmur: harsh, holosystolic murmur best heard at the left lower sternal border.

    • Murmur intensity increases with maneuvers that raise afterload (e.g., handgrip).

    • Smaller defects → louder murmurs; large defects → softer murmurs (due to reduced turbulence).

  • Systolic thrill in the 3rd or 4th left intercostal space.

  • Mid-diastolic rumble at the apex (due to increased flow across mitral valve).

  • Loud pulmonic component of S2 (P2) if pulmonary hypertension develops.

Diagnostics

Echocardiography (TTE > TEE)

  • Confirmatory test.

  • Evaluates: size of the defect, shunt direction and volume, Qp:Qs ratio, and presence of complications such as pulmonary hypertension or outflow obstruction.

  • Doppler echocardiography: sensitive for detecting small defects.

Electrocardiogram (ECG)

  • Small VSD: often normal.

  • Medium/Large VSD:

    • Left atrial enlargement (P mitrale).

    • LV hypertrophy: high QRS voltage, left axis deviation.

    • Biventricular hypertrophy if pulmonary hypertension develops.

    • RV hypertrophy: right axis deviation, tall R waves in V1, right bundle branch block (complete or incomplete).

Chest X-ray

  • Small defects: typically normal.

  • Moderate/Large defects:

    • Cardiomegaly due to LA and LV enlargement.

    • Prominent pulmonary vascular markings (due to increased pulmonary blood flow).

    • Later stages: RV hypertrophy and enlarged pulmonary artery contour.

Management

Small/Asymptomatic defects

  • High likelihood of spontaneous closure (particularly muscular VSDs).

  • Conservative approach: clinical monitoring + serial echocardiography.

Large/Symptomatic defects

  • Medical therapy:

    • General heart failure management (diuretics, digoxin, afterload reduction if needed).

    • Nutritional support in infants with failure to thrive.

  • Surgical closure (e.g., patch repair) indicated in:

    • Infants with large left-to-right shunts and symptomatic heart failure refractory to medical therapy.

    • Asymptomatic older children with evidence of LV dilation or elevated pulmonary artery pressures.

  • Pulmonary hypertension: timely VSD closure prevents progression to irreversible pulmonary vascular disease.

  • Post-closure physiology: RV and LA pressures decrease, LV pressure increases compared to pre-closure state.

Complications

  • Arrhythmias (especially atrial arrhythmias and conduction abnormalities post-surgery).

  • Congestive heart failure in large unrepaired defects.

  • Eisenmenger syndrome: reversal of shunt to right-to-left due to longstanding pulmonary hypertension.

  • Infective endocarditis: particularly in unrepaired defects.

  • Aortic regurgitation: due to aortic cusp prolapse into the septal defect (membranous VSDs).

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