What is the most common congenital cardiac defect?

Ventricular Septal Defect is the Most Common Congenital Cardiac Defect

Ventricular septal defect (VSD) is the most common congenital heart defect at birth, occurring in approximately 3.0 to 3.5 infants per 1000 live births. 1

Epidemiology and Prevalence

• VSDs represent 25-30% of all congenital heart defects, making them the most frequent congenital cardiac anomaly 2
• Recent data from the Copenhagen Baby Heart Study found VSDs in 3.3% of newborns, with the prevalence decreasing to 0.5% by one year of age due to spontaneous closure 3
• The high rate of spontaneous closure (83.5% within the first year) explains why the incidence is much lower in older children and adults 3

Types of VSDs

VSDs are classified into four anatomic types:

• Type 1 (Subarterial/Outlet): Located in the outflow portion of the right ventricle

  • Accounts for approximately 6% of defects in non-Asian populations and up to 33% in Asian patients
  • Spontaneous closure is uncommon 1

• Type 2 (Perimembranous): Most common type

  • Accounts for approximately 80% of all VSDs
  • Located in the membranous septum adjacent to the tricuspid valve
  • May form a septal aneurysm that can lead to partial or complete closure 1

• Type 3 (Inlet): Located in the lower part of the right ventricle adjacent to the tricuspid valve

  • Commonly associated with Down syndrome 1

• Type 4 (Muscular): Can be located centrally, apically, or at the margin of the septum

  • Often multiple in number
  • High rate of spontaneous closure 1, 3

Clinical Presentation and Natural History

• Small VSDs may be asymptomatic with only a systolic murmur
• Moderate to large VSDs can lead to left ventricular volume overload and pulmonary hypertension
• Adults with unrepaired VSDs may present with:
  • Asymptomatic murmur
  • Infective endocarditis
  • Aortic regurgitation due to valve prolapse
  • Cyanosis and exercise intolerance from pulmonary vascular disease 1

Comparison with Other Common Congenital Heart Defects

• While atrial septal defects (ASDs) are common, they are less frequent than VSDs
• Transposition of the great arteries is the second most common cyanotic defect but overall less common than VSD 4
• Tetralogy of Fallot, though the most common complex cyanotic defect, is less prevalent than isolated VSD 1
• Aortic coarctation is also less common than VSD 1

Diagnostic Considerations

• Echocardiography with color Doppler is the primary diagnostic tool
• MRI may be valuable in detecting VSDs that are difficult to visualize by other methods, particularly trabecular or apical defects 2
• Chest radiography is often the initial imaging study but has limited sensitivity for small defects 1

In summary, ventricular septal defect is definitively the most common congenital cardiac defect, with strong evidence supporting answer choice (b) as correct. The high rate of spontaneous closure, particularly of muscular VSDs, explains why the prevalence decreases significantly after infancy.