Most Common Congenital Heart Diseases

Frequency Ranking

Class 1: Left-to-Right Shunts (Acyanotic - most common group)

Common congenital left-to-right shunts - Robbins & Kumar Basic Pathology, Fig. 9.2

1. Ventricular Septal Defect (VSD) - #1 Most Common

• Accounts for 25-35% of all CHD - the single most common congenital cardiac anomaly
• Most frequently located in the membranous (perimembranous/outlet) portion of the interventricular septum
• Other locations: muscular, inlet (AV canal type), subpulmonary (conal septal)
• Small VSDs spontaneously close in many children during early life; muscular defects are often pressure-restricted with no hemodynamic consequence
• Large VSDs cause symptoms of heart failure and poor somatic growth, requiring surgical closure before adulthood
• Classic murmur: harsh holosystolic murmur at the left sternal border
• Harrison's Principles of Internal Medicine 22E, p. 2115; Morgan and Mikhail's Clinical Anesthesiology, p. 3039

2. Atrial Septal Defect (ASD)

• Third most common CHD overall; 1-2 per 1,000 live births, representing ~1% of CHDs (second most common in adults, as many VSDs close)
• Types:
  • Ostium secundum (90% of ASDs) - smooth-walled defect near the foramen ovale; most common type
  • Ostium primum (~10%) - located in the lower atrial septum; often associated with mitral valve cleft
  • Sinus venosus - near the SVC-RA junction; associated with partial anomalous pulmonary venous return
• ASD causes right atrial and ventricular volume overload; right ventricular hypertrophy and pulmonary artery dilation
• Women with unoperated ASD generally tolerate pregnancy well
• Mulholland and Greenfield's Surgery, p. 1206; Robbins & Kumar Basic Pathology

3. Patent Ductus Arteriosus (PDA)

• Connection between the aortic isthmus and the origin of the pulmonary artery, normally closing after birth
• Small PDAs are silent and hemodynamically insignificant
• Large PDAs cause left heart dilation and can lead to chronically elevated pulmonary vascular resistance and Eisenmenger syndrome
• Classic murmur: continuous "machinery" murmur heard best below the left clavicle, extending from systole past S2 into diastole (reflects flow gradient from aorta to pulmonary artery)
• Harrison's Principles of Internal Medicine 22E, p. 2116

Class 2: Right-to-Left Shunts (Cyanotic)

4. Tetralogy of Fallot (TOF) - Most Common Cyanotic CHD

• Occurs in 0.5 per 1,000 live births; most common cyanotic defect in the postinfancy period, accounting for up to 10% of all CHD
• Four features (all result from anterosuperior displacement of the infundibular septum):
  1. Large VSD
  2. Right ventricular outflow tract obstruction (subpulmonic stenosis)
  3. Overriding aorta
  4. Right ventricular hypertrophy
• "Boot-shaped heart" on CXR (coeur en sabot)
• Severity depends on the degree of pulmonic outflow obstruction
• The pulmonic stenosis paradoxically protects the pulmonary vasculature from hypertension - right heart failure is rare
• Treatment: primary surgical repair in infancy
• Harrison's Principles of Internal Medicine 22E, p. 2116; Robbins & Kumar Basic Pathology

5. Transposition of the Great Arteries (TGA)

• Aorta arises from the RV and the pulmonary artery from the LV - creating two parallel, non-communicating circulations
• Most common cyanotic CHD presenting at birth (neonatal emergency)
• Survival depends on a mixing lesion (PFO, VSD, or PDA)
• Requires urgent surgical correction (arterial switch operation)

Class 3: Obstructive Lesions

• Pulmonary stenosis - most commonly valvular; can be isolated or part of TOF
• Coarctation of the aorta - narrowing of the aorta, typically near the ligamentum arteriosum; associated with bicuspid aortic valve (50%); presents with upper extremity hypertension and weak femoral pulses
• Aortic stenosis - congenital bicuspid aortic valve is the most common congenital cardiac anomaly if PFO is excluded

Key Concept: Eisenmenger Syndrome

• Robbins & Kumar Basic Pathology, p. 348