Tetralogy of Fallot

Aka: Tetralogy of Fallot

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II. Epidemiology

  1. Incidence: 10-15% of Congenital Heart Disease
  2. Most common cause of CHD outside infancy

III. Pathophysiology

  1. See Tet Spell
  2. Cyanotic Congenital Heart Disease
    1. Secondary to Right-To-Left Shunt (related to VSD and pumonary stenosis)
    2. May present in first days to month of life with Cyanosis and severe pulmonic stenosis
      1. Stabilized with PGE-1 infusion followed by endovascular ductus stent
      2. Similar initial management as with other cyanotic ductus dependent lesions
  3. Four components
    1. Primary features responsible for symptoms (resulting in a right to left shunt)
      1. Large Ventricular Septal Defect (VSD)
      2. Right outflow tract obstruction
    2. Other features
      1. Right Ventricular Hypertrophy
      2. Aorta overides both ventricles (mixing oxygenated and deoxygenated blood)
  4. Right to left shunt is the key mechanism of Tetralogy of Fallot
    1. Right outflow obstruction leads to pulmonary vascular resistance greater than Systemic Vascular Resistance
      1. Blood easily shunts across the Ventricular Septal Defect which re-circulates de-oxygenated blood
      2. Tet Spells occur from increased right sided pressures, or decreased left sided pressures
    2. Increased right sided pressures
      1. Hypoxia
      2. Tachycardia
    3. Decreased left sided pressures
      1. Fever or Sepsis
      2. Dehydration

IV. Associated Conditions

  1. Right aortic arch (25%)
  2. Atrial Septal Defect (15%)
  3. Absent pulmonary valve
  4. Pulmonary atresia
  5. Pulmonary stenosis
  6. Atrioventricular septal defect
  7. Left superior vena cava to coronary sinus

V. Signs: General

  1. Oxygen Saturation is always low (e.g. 80%)
  2. Systolic ejection murmur at left sternal border
    1. Grade III+ intensity, harsh Systolic Murmur
    2. Murmur diminishes in intensity during "Tet Spell"
  3. Single S2 Heart Sound

VI. Signs: Tet Spell

  1. Ill appearing child
  2. Refractory Hypoxia
  3. Right ventricular outflow related murmur decreases with a lowering of right sided-flow
  4. VSD-related murmur persists

VII. Diagnostics: Electrocardiogram

  1. Right Axis Deviation
  2. Right Ventricular Hypertrophy

VIII. Labs

  1. Arterial Blood Gas
    1. Normal arterial pH
    2. Normal arterial pCO2
    3. Low arterial pO2

IX. Imaging

  1. Chest XRay
    1. Heart size normal or small
    2. Narrow mediastinum
    3. Heart may appear "boot shaped" in classic presentation
  2. Echocardiogram
    1. Large Ventricular Septal Defect (VSD)
    2. Right outflow tract obstruction
    3. Right Ventricular Hypertrophy
    4. Overriding aorta

X. Management: Tet Spell

  1. Decrease stress (to reduce Heart Rate and allow for pulmonary vascular filling)
    1. Calming measures
    2. Treat pain and avoid painful procedures
      1. Use EMLA cream prior to IV insertion
      2. Intranasal anxiolysis and Analgesics
        1. Intranasal Fentanyl
        2. Intranasal Midazolam
        3. Intranasal Ketamine
  2. Knee chest position
    1. Increases Systemic Vascular Resistance
  3. Manage Hypoxia (to reduce pulmonary vascular resistance)
    1. Supplemental Oxygen
    2. Critically ill children may require Endotracheal Intubation (high risk)
      1. Ensure adequate preoxygenation and hydration prior to intubation
      2. Have Phenylephrine or neorepinephine available bedside to immediately treat Peri-Intubation Hypotension
  4. Treat Hypovolemia and Hypotension
    1. Rehydration with IV fluid boluses
    2. Vasopressors that do not increase Heart Rate
      1. Phenylephrine
      2. Norepinephrine

XI. Management: Surgery

  1. Stabilized with PGE-1 infusion followed by endovascular ductus stent in first days of life before ductus closure
    1. Similar initial management as with other cyanotic ductus dependent lesions
  2. Subclavian to pulmonary artery shunt (Blalock-Taussig)
    1. Palliative or temporizing method
  3. Definitive, total repair
    1. Repair as newborn or at age 3 years
    2. Ventricular Septal Defect patch
    3. Right ventricular outflow tract widening

XII. Causes: Cyanotic Episodes ("Tet Spells")

  1. Hypoxia responsive to Supplemental Oxygen
    1. Impaired alveolar gas exchange (e.g. Pneumonia, Pulmonary Edema)
  2. Hypoxia UNresponsive to Supplemental Oxygen
    1. Decreased pulmonary Blood Flow via ductus arteriosus (ductus stent Occlusion, closure of unstented ductus)

XIII. Complications: Without repair (inoperable cases)

  1. Affects related to:
    1. Hypoxia
    2. Polycythemia
  2. Symptoms
    1. Headache
    2. Altered Level of Consciousness
    3. Cerebrovascular Accident
    4. Epistaxis
    5. Hemoptysis
    6. Hyperuricemia and Gout

XIV. Complications: Post-surgical correction

  1. Arrhythmia
  2. Right ventricular insufficiency
    1. Right Ventricular Failure
    2. Pulmonary insufficiency
  3. Left ventricular insufficiency
    1. Left Ventricular Failure
    2. Aortic Insufficiency

XV. Prognosis

  1. Survival post-surgical repair: >95%
  2. Cognitive development may be impaired

XVI. References

  1. Drapkin and Claudius (2024) Tetralogy of Fallot, EM:Rap, published 4/22/2024
  2. Broder (2023) Crit Dec Emerg Med 37(9): 22-3
  3. Civitarese and Crane (2016) Crit Dec Emerg Med 30(1): 14-23
  4. Cyran (1998) PREP review lecture, October, Phoenix
  5. Merenstein (1994) Pediatrics, Lange
  6. Tsze and Spangler in Herbert (2015) EM:Rap 15(4): 2-3
  7. Saenz (1999) Am Fam Physician 59(7):1857-66 [PubMed]

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