Tetralogy of Fallot

Background

• Most common cyanotic CHD manifesting in post-infancy period. Tet spells are acute episodes of hypoxia and cyanosis caused by right-to-left shunting across the VSD. Patients will present with irritability, agitation, grunting, crying, and central cyanosis.
• During cyanotic spells, there is either:

1. Increased pulmonary outflow obstruction and/or
2. Decreased systemic vascular resistance leading to right-to-left shunting

• During the spell there is hypercarbia and hypoxemia (which further increases pulmonary vascular resistance). The process compounds itself creating worsening right-to-left shunting, hyperpnea, right outflow tract obstruction and increased systemic venous return.

Tetralogy

1. VSD
2. RV outflow obstruction (pulmonic stenosis)
3. Overriding aorta
4. RV hypertrophy

Clinical Presentation

• Systolic ejection murmur along the left sternal border
• Cyanosis worse during feeding and crying
• May squat to relieve symptoms: increases afterload and decreases shunt
• Acute respiratory distress (Tet Spells) due to increased right outflow tract obstruction

Work-Up

• Echo
• CXR: shows the classic “boot-shaped” heart

Differential Diagnosis

Congenital Heart Disease Types

• Cyanotic
  • Tetralogy of fallot
  • Total anomalous pulmonary venous return
  • Transposition of the great arteries
  • Tricuspid atresia
  • Truncus arteriosus
  • Ebstein anomaly
  • Hypoplastic left heart syndrome
• Acyanotic
  • AV canal defect
  • Atrial septal defect (ASD)
  • Ventricular septal defect (VSD)
  • Cor triatriatum
  • Patent ductus arteriosus (PDA)
  • Pulmonary/aortic stenosis
  • Coarctation of the aorta
• Differentiation by pulmonary vascularity on CXR
  • Increased pulmonary vascularity
    • Large ASD
    • Large VSD
    • Total anomalous pulmonary venous return
    • Transposition of the great arteries
    • Truncus arteriosus
  • Decreased pulmonary vascularity
    • Tetralogy of fallot
    • Rare heart diseases with pulmonic stenosis

Treatment

• Acute Presentation (Tet spell):

Knee-to-Chest Position

• The knee-to-chest position increases SVR. Dr. This can be done in the parent's arms or while lifting the patient onto the parents shoulders and tucking the knees underneath the chest.
• Increasing the SVR causes more blood to flow to the pulmonary circulation

Analgesia

1. Morphine 0.1-0.2Mg/kg IV or IM
   • Goal is to ideally avoid IV placement if possible
2. Intranasal Fentanyl 1.5-2mcg/kg range
   • Only one case report but IN administration may avoid the pain from a needle stick

Phenylephrine

• Dose: 0.2 mg/kg IV
• Increases SVR similar to knee to chest positioning

Fluids IV

1. Improves RV filling

Beta blockers

• Propranolol IV
  • Will relax the spasm causing right-sided ventricular outflow obstruction.
  • Should be administered in consulation with cardiology and pediatric surgery.

Prostaglandin E1

• 0.1 mg/kg bolus followed by infusion 0.05 to 0.1 mg/kg/min
• Maintains the ductus
• Side Effects: Hypotension, Bradycardia, Seizures and Apnea

Definitive Treatment

• Cardiothoracic surgery to repair the defects early before significant pulmonary hypertension develops.

See Also

• Congenital Heart Disease