Tetralogy of Fallot

Aka: Tetralogy of Fallot, Tet Spell

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II. Epidemiology

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

III. Pathophysiology: General

  1. Cyanotic Congenital Heart Disease
    1. Secondary to Right-To-Left Shunt (related to VSD and often pumonary stenosis)
    2. May present in first month of life with Cyanosis and severe pulmonic stenosis
      1. Treated with PGE-1 infusion (as other cyanotic ductus dependent lesions)
  2. Four components
    1. Primary features responsible for symptoms
      1. Large Ventricular Septal Defect (VSD)
      2. Right outflow tract obstruction
    2. Other features
      1. Right Ventricular Hypertrophy
      2. Overriding aorta

IV. Pathophysiology: Tet Spell (hypercyanotic episode)

  1. Inciting event (e.g. crying or feeding)
    1. Increased pulmonary outflow obstruction
    2. Decreased Systemic Vascular Resistance
  2. Results in Right-to-left Shunting
    1. Hypercarbia
    2. Hypoxemia
  3. Results in Increased pulmonary vascular resistance
    1. Worsens right-to-left shunting in cycles of worsening hypercarbia and Hypoxemia
  4. Management (see below) goals
    1. Increase Systemic Vascular Resistance (e.g. knees to chest, Supplemental Oxygen)
    2. Decrease hyperpnea (deep, rapid breathing)

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. Signs: Presentation "Tet Spell"

  1. Hypercyanotic, intermittent episode
  2. Occurs in early morning with awakening
  3. Symptoms
    1. Hyperpnea
    2. Irritibility
    3. Central Cyanosis
    4. Grunting

VII. Signs

  1. Systolic ejection murmur at left sternal border
    1. Grade III+ intensity, harsh Systolic Murmur
    2. Murmur diminishes in intensity during "Tet Spell"
  2. 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: Conservative of "Tet Spells"

  1. Knee-to-chest position
    1. Similar to older children who squat during episodes
    2. Place infant in mothers arms with their knee flexed against their chest
    3. Decreases venous return and excessive Preload
  2. Avoid upsetting child
    1. Delay IV starts during initial stabilization
    2. Keep child with parent or guardian
  3. Supplemental Oxygen
    1. Decreases pulmonary vascular resistance (PVR)
  4. Opioid Analgesics
    1. Quiets child, reduces Tachypnea and reduces systemic venous return
    2. Morphine Sulfate 0.1 to 0.2 mg/kg SQ or IM (or 0.05 to 0.1 mg/kg IV)
    3. Fentanyl 1.5 to 2 mcg/kg intranasal via mucosal atomization device (MAD Device)
    4. Ketamine 1 to 2 mg/kg IV
  5. Volume expansion
    1. Consider Normal Saline bolus (10-20 ml/kg)
    2. Increases Preload and improves right end-diastolic volume
  6. Advanced medications
    1. Consult pediatric cardiology
    2. Phenylephrine
      1. Increases Systemic Vascular Resistance
      2. Dose: 0.2 mg/kg IV
    3. Beta Blocker
      1. Reduces right ventricular outflow obstruction
      2. Acute: Propranolol 0.05 to 0.01 mg/kg IV
      3. Chronic: Propranolol 1 to 4 mg/kg/day PO

XII. Management: Surgery

  1. Subclavian to pulmonary artery shunt (Blalock-Taussig)
    1. Palliative or temporizing method
  2. 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. Civitarese and Crane (2016) Crit Dec Emerg Med 30(1): 14-23
  2. Cyran (1998) PREP review lecture, October, Phoenix
  3. Merenstein (1994) Pediatrics, Lange
  4. Tsze and Spangler in Herbert (2015) EM:Rap 15(4): 2-3
  5. Saenz (1999) Am Fam Physician 59(7):1857-66 [PubMed]

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