Tetralogy of Fallot

• • A congenital heart lesion that decreases pulmonary arterial blood flow resulting in a right-to-left shunt

  • Cyanosis and decreased oxygen delivery causes compensatory polycythemia (Hct > 70%) and spontaneous thrombosis

  • Exercise, acidosis, pain worsens cyanosis, can cause hypoxic spells

  • Squatting increases systemic resistance, causing increased pulmonary flow and oxygen saturation

  • β-Blockers (decreases spasm), fluid intake, HCO3 administration, norepinephrine (increases systemic resistance) may help decrease hypoxia

  • Clubbing due to proliferation of capillaries and AV fistulas in extremities

  • Bronchial and mediastinal arteries enlarge

  • Ductus arteriosus maintains flow to lungs during fetal development

  • Alprostadil early can allow time for optimization before definitive treatment

  • 4 anomalies:

  • 1. Ventricular septal defect (VSD)

    2. Pulmonary stenosis or atresia

    3. Overriding aorta

    4. RV hypertrophy

  • Pulmonary stenosis may involve infundibulum, valve, or main pulmonary artery (PA)

  • Extent of pulmonary atresia/stenosis has wide spectrum of severity

  • Pulmonary flow depends on aortopulmonary collaterals, can be extensive enough to cause congestive heart failure

  • Spasm of infundibular muscle may cause unconciousness and death

Symptoms and Signs

• • Symptoms related to amount of pulmonary blood flow

  • With close of ductus, cyanosis and acidosis may be severe

  • Hypoxic spells and cyanosis may lead to cerebral hypoxia and death

  • Squatting and clubbing

  • Prominent RV impulse, single S2

  • Ejection murmur, left third intercostal space

  • Murmur softens during cyanotic spell

Laboratory Findings

• • ECG: RV hypertrophy

Imaging Findings

• • Chest film: Small heart size + cyanosis + decreased pulmonary flow

  • Echocardiography: Confirms diagnosis

  • Catheterization: Necessary to define size of pulmonary arteries and identify aortopulmonary arteries

• • Consider other congenital anomalies

  • Diminutive PA can lead to right heart failure with operative repair

  • McGoon ratio: Diameter of PAs normalized to diameter of aorta > 2.0

• • Chest x-ray

  • ECG

  • Echocardiography, cardiac catheterization

• • Most symptomatic at diagnosis

  • Alprostadil, HCO3, oxygen

  • One stage correction: Patch repair of VSD, patch to infundibulum to widen outflow tract, pulmonary insufficiency tolerated in child, may not be long-term

  • Two stage: Initial systemic-PA shunt, later stage definitive correction

  • Tetralogy of Fallot with pulmonary atresia: Connect large aortopulmonary shunts to RV outflow or to shunt; induces growth of vasculature

Surgery

• • Operative options to increase pulmonary flow:

  • -Blalock-Taussig shunt: Subclavian artery to ipsilateral PA end to side fashion

    -Modified Blalock-Taussig shunt:

    Subclavian to PA using PTFE

    -Glenn: Superior vena cava (SVC) to PA shunt

    -Fontan: SVC and inferior vena cava (IVC) rerouted to PA

    -Excision of obstructive muscle, patch enlargement of infundibulum, and valve replacement

Indications

• • Once diagnosed, repair

Prognosis

• • RV dysfunction common

  • Mortality < 5% in stenosis; 30-45% in atresia

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