1.7 Congenital Heart Disease (ASD, VSD, PDA, Coarctation, Tetralogy of Fallot)

Congenital Heart Disease

PANCE High-Yield Focus: Congenital heart disease (CHD) is an explicit cardiovascular blueprint sub-category. Focus on the five classic lesions — ASD, VSD, PDA, Coarctation of the Aorta, and Tetralogy of Fallot — their classic murmurs, syndromic associations, the cyanotic vs. acyanotic distinction, and the Eisenmenger progression.

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Cyanotic vs. Acyanotic Classification

Congenital heart lesions are classified by whether they produce right-to-left shunting (cyanotic) or left-to-right shunting / no shunt (acyanotic).

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Atrial Septal Defect (ASD)

ASD is a communication between the atria. The most common type in adults is the ostium secundum ASD (~80% of cases), located at the fossa ovalis. Ostium primum ASD is associated with endocardial cushion defects and Down syndrome.

• Pathophysiology: Left-to-right shunting at the atrial level increases pulmonary blood flow. Over years, this causes right ventricular volume overload and, eventually, pulmonary hypertension. paradoxical emboli (DVT → through ASD → systemic stroke) can occur.
• Clinical Presentation: Often asymptomatic in childhood, presenting in adulthood with exercise intolerance, dyspnea, or paradoxical embolism stroke.
• Physical Exam: Fixed, wide splitting of S2 (delayed pulmonary valve closure from increased RV volume) — the hallmark. A systolic ejection murmur is heard at the left upper sternal border.
• Management: Percutaneous transcatheter device closure (secundum ASD) or surgical patch closure.

Ventricular Septal Defect (VSD)

VSD is the most common congenital heart defect at birth. The most common type is the perimembranous VSD (~80%).

• Pathophysiology: Left-to-right shunting at the ventricular level. Small VSDs often close spontaneously. Large VSDs cause pulmonary overcirculation and can progress to Eisenmenger syndrome if unrepaired.
• Clinical Presentation: Small VSDs are asymptomatic with a loud holosystolic murmur. Large VSDs present with failure to thrive, frequent respiratory infections, and heart failure symptoms.
• Physical Exam: Harsh holosystolic murmur at the left lower sternal border. A thrill may be palpable.
• Management: Many small VSDs close spontaneously. Large, symptomatic VSDs require surgical or percutaneous closure.

Patent Ductus Arteriosus (PDA)

The ductus arteriosus connects the pulmonary artery to the descending aorta in fetal life, allowing blood to bypass the lungs. Failure to close after birth results in PDA.

• Risk Factors: Prematurity, maternal rubella infection, high altitude.
• Pathophysiology: Left-to-right shunting from the aorta to the pulmonary artery. Large PDAs cause pulmonary overcirculation and can progress to Eisenmenger syndrome.
• Physical Exam: Continuous "machinery" murmur heard best at the left upper sternal border/infraclavicular area. Bounding pulses and a wide pulse pressure due to diastolic runoff.
• Medical Closure: Indomethacin (a prostaglandin inhibitor) closes a PDA in premature infants. Acetaminophen is an alternative when indomethacin is contraindicated.
• Surgical Closure: Surgical ligation or percutaneous device closure when pharmacological closure fails or in term infants.
• PANCE Trap — Prostaglandin E1 vs. Indomethacin: To KEEP the ductus open (e.g., in ductal-dependent lesions such as severe coarctation, transposition of the great arteries, or hypoplastic left heart), administer Prostaglandin E1 (alprostadil). To CLOSE the ductus in a premature infant with symptomatic PDA, use Indomethacin.

Coarctation of the Aorta

Congenital narrowing of the descending thoracic aorta, typically just distal to the left subclavian artery.

• Associations: Strongly associated with Turner syndrome. Also associated with bicuspid aortic valve (up to 75% of cases).
• Clinical Presentation: Upper-extremity hypertension with diminished or delayed femoral pulses (radio-femoral delay). An extremity blood pressure differential (>20 mmHg systolic between arms and legs) is classic.
• Physical Exam: Systolic murmur over the left interscapular region. A continuous murmur from collateral vessels may be heard.
• Imaging: Chest X-ray shows rib notching (from collateral intercostal arterial flow) and the "figure 3 sign" (pre- and post-stenotic dilation). Echocardiography, MRI, or CTA confirm.
• Management: Surgical resection with end-to-end anastomosis, or balloon angioplasty/stenting in older children and adults.

Tetralogy of Fallot (TOF)

TOF is the most common cyanotic congenital heart defect in children who survive infancy.

• The Four Components (PROVe):

  1. Pulmonary stenosis (right ventricular outflow obstruction)
  2. Right Ventricular Hypertrophy (RVH)
  3. Overriding Aorta (aorta overrides the VSD)
  4. Ventricular Septal Defect (VSD)

• Pathophysiology: The degree of right ventricular outflow obstruction determines the severity of cyanosis. Greater obstruction → more right-to-left shunting → more cyanosis.

• Clinical Presentation: Cyanotic "tet spells" (hypercyanotic spells) triggered by crying, feeding, or activity. Squatting increases systemic vascular resistance, reducing right-to-left shunting and improving cyanosis — a classic bedside clue in older children.

• Physical Exam: Systolic ejection murmur at the left sternal border (from pulmonary stenosis). Single S2 (pulmonary component is soft or absent).

• Imaging: Boot-shaped heart on chest X-ray (concave pulmonary trunk + RVH). Echocardiography confirms the diagnosis.

• Surgical Correction: Complete repair (VSD patch closure + relief of right ventricular outflow obstruction) typically performed in infancy.

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PANCE Clinical Traps

• Eisenmenger Syndrome: Long-standing left-to-right shunts (ASD, VSD, PDA) cause pulmonary vascular remodeling and pulmonary hypertension. When pulmonary pressure exceeds systemic pressure, the shunt reverses (right-to-left), causing late-onset cyanosis. Once Eisenmenger develops, closure is contraindicated.
• PGE1 vs. Indomethacin: Prostaglandin E1 (alprostadil) KEEPS the PDA open (ductal-dependent lesions). Indomethacin CLOSES the PDA (premature infants with symptomatic PDA).
• TOF Squatting: Squatting increases SVR and decreases right-to-left shunting, classically seen in older children with TOF during exercise to relieve cyanotic spells.