Epidemiology

Etiology

Types by location:
- Membranous (perimembranous): ~80%, most common
- Muscular (trabecular): may close spontaneously
- Inlet (AV canal type): assoc. w/ Down syndrome
- Outlet (subarterial/supracristal)

Small VSD (Restrictive): Usually asymptomatic.
- Loud, harsh holosystolic murmur at left lower sternal border (LLSB).
- Palpable thrill may be present.
Large VSD (Unrestrictive): Presents at 4-6 weeks of life as pulmonary vascular resistance (PVR) drops. So it may not be heard at birth
- Heart failure (HF) symptoms: Failure to thrive (FTT), tachypnea, diaphoresis w/ feeding, hepatomegaly.
- Softer holosystolic murmur (less turbulence).
- Apical diastolic rumble (due to relative mitral stenosis from ↑ pulmonary venous return to LA/LV).
- Prominent P2 (if pulmonary HTN develops).

Initial: ECG and CXR.
- ECG: Small VSD = normal. Large VSD = LA & LV hypertrophy (volume overload); RVH if pulmonary HTN develops.
- CXR: Small VSD = normal. Large VSD = Cardiomegaly, ↑ pulmonary vascular markings.
Confirmatory/Gold Standard: Echocardiography (visualizes defect size, location, and shunt gradient/direction).
Cardiac Catheterization: Rarely needed for diagnosis; used to assess pulmonary artery pressures if Eisenmenger syndrome is suspected.

Small/Asymptomatic: Observation. ~75% close spontaneously by age 1-2 years. Routine IE prophylaxis not indicated. c
- Mechanism: As the infant grows, the existing cardiomyocytes undergo hypertrophy (increase in size, not number).
Large/Symptomatic (Medical Management): Used as a bridge to surgery.
- HF control: Diuretics (furosemide), ACEi (reduces afterload, promoting systemic flow over shunt), digoxin.
- Nutrition: High-calorie fortified feeds/NG tube for FTT.
Definitive (Surgical Closure):
- Indications: Refractory HF, FTT, or development of pulmonary HTN.
- Timing: Usually repaired at 3-6 months of age to prevent irreversible pulmonary vascular disease.