Tetralogy of Fallot

Aka: Tetralogy of Fallot, Pulmonary Stenosis, VSD, RVH, and Overriding Aorta

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II. Epidemiology

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

III. Risk Factors

  1. Genetic Syndromes
    1. DiGeorge Syndrome
    2. Down Syndrome
  2. Family History
    1. Increased risk in first-degree relatives with certain genetic defects (up to 3%)
    2. Digilio (1997) J Med Genet 34(3):188-90 +PMID: 9132487 [PubMed]
  3. Maternal conditions
    1. Gestational Diabetes
    2. Rubella infection
    3. Tobacco Abuse
    4. Teratogens

IV. 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 (pulmonary stenosis or atresia)
    2. Other features
      1. Right Ventricular Hypertrophy
      2. Aorta overrides 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

V. 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

VI. Symptoms: Presentations

  1. Typically identified on Newborn Pulse Oximetry Screening for Congenital Heart Disease
  2. Severity of presentation depends on subtype
    1. Pink Tetralogy of Fallot initially presents with non-ill appearing infant and mild Hypoxia
    2. Fallot-type pulmonary atresia (most severe type) presents with severe Cyanosis
  3. General
    1. Tachypnea
    2. Fussiness

VII. Signs

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

VIII. Diagnostics: Electrocardiogram

  1. Right Axis Deviation
  2. Right Ventricular Hypertrophy

IX. Labs

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

X. 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

XI. Management: Tet Spell

  1. See Tet Spell

XII. 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

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. Roth (2024) Crit Dec Emerg Med 38(10): 15-6
  7. Tsze and Spangler in Herbert (2015) EM:Rap 15(4): 2-3
  8. Saenz (1999) Am Fam Physician 59(7):1857-66 [PubMed]

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