Tetralogy of Fallot

Background

• Most common cyanotic CHD manifesting in post-infancy period
• Acute episodes of hypoxia and cyanosis caused by right-to-left shunting across the VSD ('Tet Spells')
• Patients may present with irritability, agitation, grunting, crying, and central cyanosis
• May have history of squatting during spells (increases systemic vascular resistance)
• During cyanotic spells, there is either:

1. Increased pulmonary outflow obstruction 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

• VSD
• RV outflow obstruction (pulmonic stenosis)
• Overriding aorta
• RV hypertrophy

Clinical Features

Digital clubbing with cyanotic nail beds in an otherwise healthy-appearing, asymptomatic young adult with Tetralogy of Fallot.

• 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
• Chronic hypoxemia causes a compensatory polycythemia and clubbing of the fingers and toes

Differential Diagnosis

Syncope (peds)

• Seizure
• Breath-holding spell
• Hyperventilation syndrome
• Pregnancy (especially ectopic)
• Hypoglycemia
• Cardiac disease
  • Tet spell
  • Hypertrophic cardiomyopathy
  • Brugada Syndrome
  • Dysrhythmias
  • Long QT syndrome
  • Anomalous coronary arteries
• Toxicologic exposure (stimulants or depressant)
  • CO poisoning
  • Ethanol toxicity
  • Drugs of abuse

Congenital Heart Disease Types

• Cyanotic
  • Tetralogy of fallot
  • Total anomalous pulmonary venous return
  • Transposition of the great arteries
  • Tricuspid atresia
  • Truncus arteriosus
  • Ebstein anomaly
  • Hypoplastic left heart syndrome
• Acyanotic
  • AV canal defect
  • Atrial septal defect (ASD)
  • Ventricular septal defect (VSD)
  • Cor triatriatum
  • Patent ductus arteriosus (PDA)
  • Pulmonary/aortic stenosis
  • Coarctation of the aorta
• Differentiation by pulmonary vascularity on CXR
  • Increased pulmonary vascularity
    • Large ASD
    • Large VSD
    • Total anomalous pulmonary venous return
    • Transposition of the great arteries
    • Truncus arteriosus
  • Decreased pulmonary vascularity
    • Tetralogy of fallot
    • Rare heart diseases with pulmonic stenosis

Evaluation

CXR of child with tetralogy of Fallot

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

Management

• Acute Presentation (Tet spell):

Knee-to-Chest Position

Knee to chest positioning of patient

• 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

• Avoid needle sticks if possible as crying worsens pulmonary vascular resistance and right-to-left shunt
  • Consider intranasal or intramuscular medications if needed
• Permit child to remain with parents
• Maintain calm, quiet, dim room to reduce agitation
• Consider IO line as resuscitation tool

Analgesia

• 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
• 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 3-5 mg/kg IM
• Benefit of sedation without decrease in vascular resistance

Phenylephrine

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

Sodium bicarbonate

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

IV fluids

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

Beta blockers

• Should be administered in consultation 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 propranolol not available (switch to PO propranolol 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

• Appropriate in neonatal period only (prior to closure of ductus arteriosus)
• 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
  • Often staged repair, completed over several surgeries
• Optimal age for correction controversial, but if elective repair, 3-11 months of age may be best

Disposition

• Admit

See Also

• Congenital Heart Disease