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Tetralogy of Fallot – Evidence Reviewed
Tetralogy of Fallot 2018-01-30T16:37:47+08:00

Definition

  • Ventricular septal defect (right-to-left shunt)
  • Right ventricular outflow tract obstruction
  • Overriding aorta
  • Right ventricular hypertrophy

Relevant physical signs

  • Peripheries
    • Clubbing
    • Cyanosis
    • Stigmata of infective endocarditis
    • Pulse
      • Left radial pulse diminished compared to the right (Blalock-Taussig shunt)
      • May be in atrial fibrillation
    • Differential blood pressure if BT shunt in place (lower on side of shunt)
    • Raised jugular venous pressure, absent a waves
  • Precordium
    • Inspection
      • Lateral thoracotomy scar – BT shunt
    • Palpation
      • Apex beat usually not displaced
        • May be displaced, thrusting quality if there is concomitant aortic regurgitation
      • Right ventricular heave (pulmonary hypertension)
      • Palpable thrill over pulmonary area (pulmonary stenosis)
      • Palpable aortic component of the second heart sound
      • Palpable thrill inferior to left clavicle (BT shunt)
    • Auscultation
      • Normal first heart sound
      • Loud aortic component of second heart sound
        • P2 is diminished due to the right ventricular tract outflow obstruction
      • Ejection systolic murmur over the pulmonary area (turbulent flow across RVOT)
        • Increasing RVOT leads to softer murmurs as blood is diverted through VSD
        • VSD is non-restrictive, therefore not associated with a murmur
      • Continuous murmur, heard best over left sub-clavicular region (BT shunt)
        • May be heart posteriorly
        • May be heard on the right if the right subclavian was used as a conduit (lateral thoracotomy scar will be on the right side)
      • Other murmurs
        • Early diastolic murmur of aortic regurgitation (prolapse of right coronary cusp of the aortic valve, known association with TOF)
  • Complications
    • Pulmonary oedema – left ventricular failure
    • Raised jugular venous pulsation, right ventricular heave, peripheral oedema – right heart failure
    • Plethora – polycythaemia
    • Janeway lesions, Osler nodes, splinter haemorrhages – infective endocarditis
    • Pronator drift, facial droop – thromboembolic disease / paradoxical embolism

Causes

  • Maternal phenylketonuria
  • CATCH 22 malformations in DiGeorge syndrome (cardiac abnormality, abnormal facies, thymic aplasia, cleft palate, hypocalcaemia / hypoparathyroidism)
  • Fetal alcohol syndrome
  • Fetal carbamazepine syndrome

Differentiating TOF from Eisenmenger’s syndrome

  • Eisenmenger’s syndrome
    • Prominent a waves in jugular venous pulsation
    • Displaced apex beat
    • No thrill over pulmonary area
    • No ESM of RVOT
    • Loud P2 due to pulmonary hypertension
  • TOF
    • Absent a waves
    • Apex beat not displaced
    • Thrill over pulmonary area
    • ESM of RVOT
    • Diminished P2, single A2

Investigation

  • Electrocardiogram
    • Dominant R wave in V1 (right ventricular hypertrophy)
    • Right axis deviation
    • Right atrial enlargement
  • Chest radiograph
    • Boot shaped heart (absent main pulmonary artery segment, apex lifted because of RVH)
    • Decreased pulmonary vascular markings
    • In some cases: right-sided aortic arch
  • Trans-thoracic echocardiogram
    • Confirm diagnosis
    • Assess severity

Management

  • Total correction in infancy under cardiopulmonary bypass
  • Blalock-Taussig shunt (palliative measure)
  • Infective endocarditis prophylaxis in patients with BT shunt and unrepaired TOF

Presentation

Sir, this patient has a tetralogy of Fallot with a Blalock-Taussig shunt. On examination of the peripheries, the patient is clubbed and cyanosed. The pulse is regular, but diminished on the left side. There is no conjunctival pallor. The jugular venous pulsation is not elevated but is monophasic, with an absent a wave. On examination of the precordium, there is a right ventricular heave. This is associated with a thrill over the pulmonary area and a palpable second heart sound over the aortic area. The apex beat is not displaced. On auscultation, the first heart sound is normal, and the second heart sound has a prominent aortic component. There is a harsh, grade 5/6 ejection systolic murmur heard loudest over the pulmonary area. In addition, there is a continuous murmur heard best under the left clavicle, which radiates to the back. There is no early diastolic murmur of aortic regurgitation, which may be associated with Fallot’s tetralogies.

In summary, this patient has a Fallot’s tetralogy, which is currently being palliated with a Blalock-Taussig shunt.

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