Tetralogy of Fallot

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Definition: TOF is the most common cyanotic congenital heart disease. It accounts for 5% to 10% of all congenital heart disease, and has an incidence of approximately 1:2000 live births. Classically described with the cardiac constellation of:

1. Ventricular septal defect (usually large)

2. Overriding aorta

3. Right ventricular outflow tract obstruction (subvalvular, valvular, supravalvular)

4. Right ventricular hypertrophy.

A wide spectrum of TOF exists, including the variants of pulmonary stenosis (TOF-PS), pulmonary atresia (TOF-PA/MAPCA) and absent pulmonary valve (TOF-APV).

Right sided arch in 25% of cases.


Physiology:

Decreased pulmonary blood flow (TET-spells) due to RVOT obstruction and increased PVR or/and congestive cardiac failure (diuretics, digoxin, nutrition).


Diagnosis:

Echo


Management of cyanotic spells:

  • Oxygenation
  • Volume expansion: 10 ml/kg IV colloid/crystalloid
  • Sedation: IV morphine 10-50 mcg/kg; or fentanyl 1 mcg/kg
  • Posture: head down position/knees-to-chest (increase VR; mild pressure over femoral arteries to increase SVR)
  • Vasopressor: metaraminol 5-10 mcg/kg IV or phenylephrine 5-10 mcg/kg, then 1-5 mcg/kg/min IV/(SC)
  • Esmolol 100-500 mcg/kg (titratable) +/- infusion

Preoperative preparation:

ECG, CXR, CUS, FBE, clotting, UECs, PRBC (4), FFP (2), platelets (2), cryoprecipitate (2).

Methylprednisolone 10mg/kg 12 hrs and 6 hrs pre surgery in neonates.


Surgery:

Timing: dependant on anatomical associations, degree of pulmonary stenosis and development of pulmonary arteries:

1. Complete correction at 3-6 mths

  • Patch repair VSD
  • Resection of infundibular muscle
  • Pulmonary valvotomy +/- transannular patch.

2. Staged procedure with BTS (BT-Shunt) in severe cyanosis or hypercyanotic spells in neonatal period.

10-15% require re-operation to relieve RVOTO +/- residual VSD.

Majority require pulmonary valve replacement for incompetence in the medium-to-long term.


Postoperative management:

  • Keep intubated, ventilated, sedated and paralysed for 24 hrs
  • Inotropes: milrinone plus dopamine or noradrenaline
  • Haemodynamics: age adjusted, in neonates: SBP >60 mmHg, MAP >40 mmHg (increasing over time), LAP 8-12 mmHg, CVP 8-12 mmHg
  • Respiratory: normoxaemia, normocapnea
  • Fluid restriction: 1ml/kg/hr, trophic feeds
  • Haemostasis
  • Keep normothermia (except in JET → cool to 35°C)

Specific problems:

  • Low cardiac output state: expect 6-12 hrs post bypass, mainly diastolic dysfunction
  • Arrthymias: JET; decrease inotropes, overdrive pacing, add noradrenaline, cooling, amiodarone
  • Diastolic RV dysfunction: restrictive physiology, usually transient phenomena lasting 48-72 hrs. may require inotropes for improving of diastolic dysfunction
  • Residual RVOTO: ECHO confirmation +/- reoperation
  • Pulmonary regurgitation: as above
  • Residual VSD: as above

Outcome:

Perioperative mortality: 3 – 8%

Long term survival 85 – 90%


References:

[1] Critical Heart Disease in Infants and Children; 2nd ed, Nichols et al: Tetralogy of Fallot with and without pulmonary atresia

[2] Lancet, 2009; 374: 1462-71: Apitz et al: Tetralogy of Fallot

[3] World J Surg, 34: 658-668; 2010: Starr J: Starr et al: Tetralogy of Fallot: Yesterday and Today.

[4] DVD 2004: Something the Lord made (Alan Rickman, Mos Def)

[5] Pediatr Cardiol. 2013 Mar 5. Dodgen et al: Characteristics and Hemodynamic Effects of Extubation Failure in Children Undergoing Complete Repair for Tetralogy of Fallot.


All Marc’s PICU cardiology FOAM can be found on PICU Doctor and can be downloaded as a handy app for free on iPhone or AndroidA list of contributors can be seen here.

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