Tetralogy of Fallot

• Which 4 anatomical abnormalities are characteristics of tetralogy of fallot?

  Venticular septal defect

  Right ventriclar hypertrophy

  Pulmonary stenosis

  Overriding aorta
• What is the primary pathophysiological consequence of tetralogy of fallot?

  Right to left shunting
• Why is there right to left shunting in ToF?

  Pressure gradient favouring flow through the ventricular septal defect
• Why does ToF lead to cyanosis?

  Deoxygenated blood bypasses the lungs as it flows through the VSD and enters the systemic circulation
• What are the causes of ToF?

  Chromosomal abnormalities

  Single gene disorders

  Environmental influences
• What are some chromosomal abnormalities that cause ToF?

  Trisomy 21 (Down syndrome)

  DiGeorge syndrome
• What are some single gene disorders that cause ToF?

  JAG1 mutations

  NKX2-5 mutations

  ZFPM2/FOG2 mutations
• What are some environmenal causes of ToF?


  Maternal diabetes mellits

  Gestational alcohol exposure

  Maternal use of retinoic acid

  Maternal phenylketonuria
• WHat is the initial abnormality in ToF?

  Formation of VSD
• What causes an abnormality in the formation of the VSD in ToF?


  Faulty alighment and fusion of the interventricular septum during embryonic development
• Why does pulmonary stasis occur?

  Narrowing at or below the pulmonary valve level = obstacle for blood flow from right ventricle to pulmonary artery = inc resistance to right vent ejection
• Why does right ventricular hypertropy occur?


  Inc resistance -> pulmonary stenosis = higher pressure load on right vent = inc workload = thickening of right vent wall = hypertrophy
• What is an overriding aorta?

  aorta straddles both ventricles above the VSD -> receives blood from both ventricles = oxygenated and deoxygenated blood mixes
• How many different types of ToF are there?

  4
• What is classic/complete ToF?

  Has all 4 key features
• What is pink/ atypical ToF and what does it present with?

  Less severe obstruction to pulmonary blood flow

  Presents with: Mild cyanosis
• What is ToF with pulmonary atresia?


  No formation of pulmonary valve = no blood flow from heart to lungs
• What is ToF with absent pulmonary valve syndrome?

  Absent ot dysplastic pulmonary valve -> dilation and distortion in pulmonary arteries and branches
• What are some other anomalies ToF may present with?

  Double outlet right ventricle

  Atrial septal defects

  Patent ductus arteriosus
• What are some signs and symptoms of ToF?

  Cyanosis

  Dyspnoea

  Failure to thrive

  Murmur

  Clubbing

  Right ventricular heave (palpable)
• Where is the murmur heard best?

  Left sternal border
• What investigations are done in ToF?

  Echo

  Chest x-ray

  ECG

  Cardiac MRI

  Cardiac catheterisation

  Genetic testing
• What are the first line investigations for ToF?


  Echo

  CXR

  ECG
• WHat is the primary investigation for ToF?


  Echo
• What would an echo show for ToF?


  The 4 characteristic defects:

  • Ventral septal defect
  • Right ventricular hypertrophy
  • Overriding aorta
  • Pulmonary stenosis
• What would a CXR show in ToF?


  'Boot shaped' heart
• What would an ECG show in ToF?


  Right axis deviation
• What are some DDx of ToF?

  Transposition of the great arteries

  Truncus arteriosus

  Pulmonary atresia with VSD
• How do you rule out the ddx?

  Transposition of the great arteries: No heart murmur and single second heart sound

  Truncus arteriosus: No clubbing and murmur due to truncal valve regurg

  Pulmonary atresia with VSD: More severe cyanosis and dyspnoea. Murmur heard over left upper sternal border
• How does transposition of great arteries present differently to ToF?


  Single second heart sound and no murmur

  Earlier presentation
• How does truncus arteriosus present differently to ToF?


  No clubbing

  Systolic ejection click followed by a high-pitched early diastolic murmur
• How does pulmonary atresia with VSD present differently to ToF?


  More severe cyanosis and dyspnoea

  Continuous murmur heard over the left upper sternal border
• What is the surgical management of ToF?

  Primary complete repair: Closure of VSD

  Palliative surgery: (modified or not modified) Blalock-taussig shunt - alternative pathway for blood to flow to lungs
• What is the non-surgical management of ToF?

  Prostaglandin E1 infusion

  Beta blockers
• What is the long term management for ToF?

  Follow ups

  Regular echos

  Exercise restriction

  Endocarditis prophylaxis
• What are some complications of ToF?

  Pulmonary regurg

  Right vent outflow tract obstruction

  Atrial and ventricular arrhythmias

  Endocarditis

  Growth retardation

  Cyanosis

  Cerebrovascular accidents

  Pulmonary issues