Congenital Heart Disease (CHD)

Definition & Epidemiology

• Robbins & Kumar Basic Pathology, p. 347

Pathogenesis

• Prematurity
• Family history
• Maternal conditions: diabetes, hypertension, obesity, phenylketonuria, thyroid disorders, connective tissue disorders
• Maternal drug exposure: phenytoin, retinoic acid, alcohol, smoking
• Assisted reproductive technology (e.g., in vitro fertilization)
• Chromosomal/genetic disorders: Trisomy 21 (Down syndrome), Trisomy 18 (Edwards), Trisomy 13 (Patau), Turner syndrome (45,X)
• In utero infections: rubella, cytomegalovirus
• Robbins & Kumar Basic Pathology, p. 347

Classification by Hemodynamic Consequence

• Robbins & Kumar Basic Pathology, p. 348

Frequency of Common Malformations

Left-to-Right Shunt Lesions

Atrial Septal Defect (ASD)

• Fixed opening in the atrial septum, allowing unrestricted interatrial blood flow
• Types:
  • Ostium secundum (90%): near the foramen ovale; most common
  • Ostium primum (5%): lowest atrial septum; associated with mitral/tricuspid valve abnormalities
  • Sinus venosus (5%): high in the atrial septum; often associated with anomalous pulmonary venous drainage
• PFO (Patent Foramen Ovale): present in ~20% of adults; flaps are sealed but not fused - allows paradoxical embolism during raised intrathoracic pressure
• Clinical features: Usually asymptomatic until adulthood (most common CHD first diagnosed in adults); right ventricular hypertrophy and dilation; risk of paradoxical embolism
• Management: Surgical or catheter-based (intravascular) closure; low mortality

Ventricular Septal Defect (VSD)

• Most common CHD diagnosed at birth (42%)
• Defects in ventricular septum, most commonly at the membranous (perimembranous) region (~90%)
• Many small VSDs close spontaneously; large defects require surgical repair
• Clinical: systolic murmur; if large, left ventricular overload, pulmonary hypertension, and eventual Eisenmenger syndrome

Patent Ductus Arteriosus (PDA)

• Persistence of the ductus arteriosus (connecting the pulmonary artery to the aorta) after birth
• Normally closes within hours to days postnatally in response to rising arterial O2 tension and falling prostaglandin levels
• Medical closure: Indomethacin (prostaglandin inhibitor) in premature infants
• Surgical/catheter closure for symptomatic or large PDAs
• Continuous ("machinery") murmur is characteristic

Right-to-Left Shunt Lesions (Cyanotic CHD)

• Polycythemia (compensatory)
• Hypertrophic osteoarthropathy
• Paradoxical embolization (venous thrombi reach systemic circulation)
• Risk of cerebral abscess

Tetralogy of Fallot (TOF)

1. VSD (large)
2. Pulmonary stenosis (right ventricular outflow obstruction)
3. Overriding aorta (aorta straddles the VSD)
4. Right ventricular hypertrophy (secondary to obstruction)

• Direction of shunt: right-to-left (through VSD) due to pulmonary stenosis
• "Tet spells": paroxysmal hypercyanotic episodes relieved by squatting (increases systemic vascular resistance)
• CXR: "boot-shaped" heart (coeur en sabot)
• Management: complete surgical repair; palliative Blalock-Taussig (BT) shunt in neonates

Transposition of the Great Arteries (TGA)

• Aorta arises from the right ventricle; pulmonary artery arises from the left ventricle
• Creates two parallel, non-mixing circuits - incompatible with life unless there is a mixing lesion (ASD, VSD, or PDA)
• D-TGA is the most common type presenting as a cyanotic emergency in neonates
• Management: arterial switch operation (Jatene procedure) in the neonatal period

Truncus Arteriosus

• Single great vessel arising from the heart, supplying both systemic and pulmonary circulations
• Associated with large VSD; always requires surgery

Total Anomalous Pulmonary Venous Connection (TAPVC)

• All four pulmonary veins drain anomalously into the right atrium (or systemic veins) rather than into the left atrium
• Must have an ASD for survival
• Management: surgical reconnection of pulmonary veins to left atrium

Tricuspid Atresia

• Complete absence of the tricuspid valve; no direct communication from RA to RV
• Survival depends on ASD (RA to LA) and VSD or PDA (for pulmonary flow)
• Management: staged palliative surgeries (Glenn → Fontan procedure)

Obstructive Lesions

Coarctation of the Aorta

• Narrowing of the aorta, most commonly just distal to the left subclavian artery (juxtaductal/postductal)
• Two patterns:
  • Preductal (infantile): proximal to ductus - duct-dependent; presents in infancy with heart failure
  • Postductal (adult): distal - collateral vessels develop; presents with hypertension in upper extremities, weak/absent femoral pulses
• Associated with bicuspid aortic valve (most common associated defect), Turner syndrome
• Classic sign: rib notching on CXR (from collateral intercostal arteries)
• Management: surgical resection or balloon angioplasty/stenting

Pulmonary Stenosis

• Obstruction of right ventricular outflow; most cases are valvular (domed, fused cusps)
• Mild to moderate: well tolerated, often asymptomatic; severe: exertional dyspnea, RV failure
• Management: balloon valvuloplasty (preferred for valvular PS)

Aortic Stenosis

• Congenital (usually bicuspid aortic valve), supravalvular, or subvalvular
• Bicuspid aortic valve: most common congenital cardiac abnormality overall (1-2% of population), though often not counted among "CHD" in classic tables
• Progressive stenosis leads to LV hypertrophy, angina, syncope, and heart failure

Eisenmenger Syndrome

Key Associations

Clinical Approach

• Present in first days to weeks when ductus closes
• Includes: TGA, pulmonary atresia, hypoplastic left heart syndrome, severe coarctation
• Emergency management: prostaglandin E1 infusion to keep ductus open while awaiting surgery

• Echocardiography: gold standard for structural diagnosis
• ECG, chest X-ray, pulse oximetry (critical CHD screening)
• Cardiac catheterization: for hemodynamic assessment, interventional procedures
• MRI/CT angiography: complex anatomy delineation

• Most defects are repaired in infancy or childhood
• Palliative procedures (e.g., BT shunt, Glenn, Fontan) used for single-ventricle physiology
• Adults with CHD (ACHD) are a growing population requiring specialized care; complex issues include arrhythmias, heart failure, pregnancy planning, and endocarditis prophylaxis

Recent literature note: A 2024 systematic review (PMID 39609780) confirmed significantly elevated stroke risk in patients with CHD, reinforcing the importance of anticoagulation and paradoxical embolism surveillance in this population.

Hypertrophic Pyloric Stenosis (HPS)

Definition

Epidemiology

• Schwartz's Principles of Surgery, p. 1749; Robbins Pathologic Basis of Disease, p. 703

Pathology & Pathogenesis

• Family history (strong genetic component; GWAS studies have identified loci on chromosome 11q23.3 and genes related to GI development)
• Prematurity and young maternal age
• Macrolide antibiotic exposure (erythromycin or azithromycin) - either orally or via breast milk - in the first 2 weeks of life is strongly associated
• Turner syndrome and trisomy 18 (increased risk)
• First-born male
• Robbins, Cotran & Kumar Pathologic Basis of Disease, p. 703

Clinical Presentation

1. Forceful, projectile, non-bilious vomiting - immediately after or during feeding. Non-bilious because obstruction is proximal to the ampulla of Vater.
2. Persistent hunger - infant feeds eagerly despite repeated vomiting ("hungry vomiter")
3. Progressive dehydration - decreased wet diapers, sunken fontanelle, dry mucous membranes
4. Visible gastric peristaltic waves - left-to-right across the upper abdomen, just before emesis (now less commonly seen as infants present earlier)
5. Palpable "olive" - firm, mobile, ovoid mass in the right upper quadrant (epigastrium). Previously found in up to 90% on examination; now found in <30% as infants present earlier before severe symptoms develop
6. Jaundice - unconjugated hyperbilirubinemia occurs in ~2-3% (mechanism unclear; possibly related to decreased glucuronyl transferase activity from starvation)

• Schwartz's Principles of Surgery; Grainger & Allison's Diagnostic Radiology

Metabolic Consequences

Hypochloremic, Hypokalemic Metabolic Alkalosis

• Loss of H⁺ and Cl⁻ in gastric juice → metabolic alkalosis and hypochloremia
• Kidneys initially compensate by excreting HCO₃⁻ with Na⁺ and K⁺ → hypokalemia
• As hypochloremia worsens, the kidney preferentially exchanges H⁺ for Na⁺ in the distal tubule to conserve sodium → paradoxical aciduria (urine becomes acidic despite systemic alkalosis)

Diagnosis

Ultrasound (Gold Standard)

• Shoulder sign - hypertrophic muscle bulges into the fluid-filled gastric antrum
• Nipple sign - double-layered hyperechoic mucosa protrudes into the stomach
• Cervix sign - hypertrophied pylorus resembles the uterine cervix on US
• Exaggerated, failed peristaltic waves visible in real-time

Upper GI Contrast Study (if US equivocal)

• "String sign" or "railroad track sign" - elongated, narrow pyloric channel
• Delayed gastric emptying
• Used when US is technically inadequate or results are equivocal
• Grainger & Allison's Diagnostic Radiology; Harriet Lane Handbook, 23rd ed.

Treatment

Step 1: Medical Stabilization (MANDATORY before surgery)

• IV fluid resuscitation: typically 5% dextrose + 0.45% NaCl + 2-4 mEq/kg/day KCl at ~150-175 mL/kg/day
• Goal: urine output > 2 mL/kg/hour, correction of alkalosis and electrolytes
• Surgery is safe to proceed when serum chloride > 100 mEq/L and HCO₃⁻ < 30 mEq/L

Step 2: Fredet-Ramstedt Pyloromyotomy (Definitive)

• Incision extends from just proximal to the pyloric vein of Mayo to the gastric antrum (1-2 cm)
• Can be performed via open (umbilical or right upper quadrant transverse incision) or laparoscopic approach
• Two RCTs have shown both approaches are equally safe; laparoscopic approach offers superior cosmetic results

Postoperative Care

• IV fluids continued for several hours post-op
• Oral feeds reintroduced gradually (Pedialyte → formula/breast milk, advancing to 60 cc every 3 hours)
• Discharge within 24-48 hours; ad lib feeding protocols may shorten hospital stay

Complications of Pyloromyotomy

• If mucosal perforation occurs, it is repaired primarily with a stitch; NG tube left 24 hours
• A 2026 systematic review (PMID 41196118) addressed recurrent HPS after pyloromyotomy, noting early recognition and re-operation are key

Acquired Pyloric Stenosis (Adults)

• Antral gastritis or peptic ulcers close to the pylorus (fibrosis/scarring)
• Carcinoma of the distal stomach or pancreas (malignant infiltration/narrowing)
• Unlike infantile HPS, treatment targets the underlying cause (endoscopic dilation, surgical bypass, or resection)
• Robbins, Cotran & Kumar Pathologic Basis of Disease, p. 703

Key Summary Points