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 Features

• 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

Differential Diagnosis

Congenital Heart Disease Types

• Cyanotic
  • Tetralogy of Fallot
  • Tricuspid anomalies
  • Truncus arteriosus
  • Total anomalous pulmonary venous return
  • Transposition
• Acyanotic
  • VSD
  • Atrial septal defect (ASD)
  • PDA
  • Cor triatriatum
  • AV canal
  • Pulmonary/aortic stenosis
• Differentiation by pulmonary vascularity on CXR
  • Increased pulmonary vascularity
    • Truncus arteriosus
    • Total anomalous pulmonary venous return
    • Transposition
    • Large ASD
    • Large VSD
  • Decreased pulmonary vascularity
    • Tetralogy of Fallot
    • Rare heart diseases with pulmonic stenosis

Evaluation

• Echo
• CXR: shows the classic “boot-shaped” heart
  • Decreased pulmonary vascularity (due to pulmonic stenosis)

Management

• Acute Presentation (Tet spell):

Knee-to-Chest Position

• Two-fold mechanism to reduce right to left shunt
  • Reduces systemic venous return
  • Increases systemic vascular resistance
• Done in the parent's arms or while lifting the patient onto the parents shoulders and tucking the knees underneath the chest

Conservative Measures

• If it can be helped, do not provoke infant with IV line (worsens crying, increasing pulmonary vascular resistance and right-to-left shunt)
• Permit child to remain with parents
• Consider IO line as resuscitation tool

Analgesia

1. Morphine 0.1-0.2mg/kg IV or IM
   • Goal is to ideally avoid IV placement if possible
   • Decreases ventilatory drive, thus decreasing systemic venous return
   • Caveat is decrease in vascular resistance
2. Intranasal Fentanyl 1.5-2 mcg/kg range
   • Only one case report but IN administration may avoid the pain from a needle stick

Ketamine

• 0.25 - 1.0mg/kg IV or IM
• Benefit of sedation without decrease in vascular resistance

Phenylephrine

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

Bicarbonate

• 1-2 mEq/kg IV slowly
• Corrects metabolic acidosis
• Reduces hyperpnea

Fluids IV

• 10-20 cc/kg bolus NS initially
• Improves RV filling in the context of restrictive RV physiology

Beta blockers

• Should be administered in consulation with cardiology and pediatric surgery
• Relax spasm causing RV outflow obstruction
• Slows HR, decrease right to left shunting
• Propranolol IV 0.1-0.2mg/kg over 5min (preferred)
• Alternatives when IV propanolol not available (switch to PO propanolol after)
  • Metoprolol IV 0.1mg/kg over 5 min, q5 min to max dose of 3x
    • Then may start infusion 1-5 mcg/kg/min
  • Esmolol 0.5mg/kg over 1 min, then 50 mcg/kg/min over 4 min

Transfusion

• pRBCs 5-10 cc/kg IV over 5hrs

Prostaglandin E1

• Start infusion at 0.05 mcg/kg/min IV and titrate up to 0.1 mcg/kg/min, monitoring for hypotension (and apnea)
• Maintains the ductus (which completely seals by ~3 wks)
• Side Effects: Hypotension, Bradycardia, Seizures and Apnea

Definitive Treatment

• Cardiothoracic surgery to repair the defects early before significant pulmonary hypertension develops
• Optimal age for correction controversial, but if elective repair, 3-11 months of age may be best

See Also

• Congenital Heart Disease

References

Authors

Ross Donaldson, Neil Young