It is a cyanotic congenital heart disease consisting of the following:
1. Pulmonary stenosis (right ventricular outflow tract obstruction).
2. Overriding and dextroposition of aorta (aortic origin—two-thirds from left ventricle and one-third from right ventricle).
3. Right ventricular hypertrophy.
4. Ventricular septal defect (VSD).
• Bluish discolouration of lips and fingers during exertion.
• Weakness, cough, chest pain, palpitation.
• Young child usually presents with cyanotic spell (Fallot’s spell) during exertion, feeding or
crying. The child becomes apnoeic and unconscious. Squatting relieves cyanosis.
• Growth retardation.
• Syncope, seizure, cerebrovascular events or even sudden death.
• Short stature.
• Cyanosis (both central and peripheral).
• Generalized clubbing involve fingers and toes.
• Pulse—low volume.
• JVP—prominent ‘a’ wave (due to RVH).
• Visible cardiac impulse in the apical and epigastric region.
• Left parasternal lift and epigastric pulsation (due to RVH).
• Systolic thrill—present in the pulmonary area.
• 1st heart sound—normal in all the areas.
• 2nd heart sound—P2 is soft (or absent) in pulmonary area, A2 is normal.
• Ejection systolic murmur in pulmonary area, which radiates to the neck, more on inspiration.
Cardinal Features of TOF
• Child with growth retardation.
• Generalised clubbing and cyanosis.
• Pulmonary ejection systolic murmur.
• History of cyanotic spells during exercise (relieved by squatting).
• CBC, ESR—polycythemia, ESR may be low.
• Chest X-ray—boot-shaped heart.
• Echocardiogram—2D and colour Doppler.
• Cardiac catheterisation.
• Infective endocarditis (common).
• Paradoxical emboli.
• Cerebral abscess (10% cases).
• Polycythaemia (due to hypoxaemia, and may lead to cerebrovascular accident and myocardial
• Coagulation abnormality.
Pentalogy of Fallot—When TOF is associated with ASD.
Triology of Fallot—ASD with PS with RVH.
Acyanotic Fallot—When the TOF is associated with infundibular pulmonary stenosis. Outflow
obstruction is mild and there is no cyanosis.
• Total surgical correction is the definitive treatment, ideally should be done prior to the age of 5.
• If pulmonary artery is hypoplastic or anatomy is unfavourable, then temporarily palliative
surgery called Blalock-Taussig shunt is performed. Corrective surgery is done later on.
• Prophylactic antibiotic to prevent infective endocarditis.
• Treatment of cyanotic spell (see below)
Blalock Taussig Shunt
It is the anastomosis between left subclavian artery with left pulmonary artery. This improves
pulmonary blood flow and pulmonary artery development and may facilitate definitive surgery
Treatment during cyanotic spell
• Knee-chest position of child.
• High concentration of O2.
• Morphine or diamorphine injection (it relaxes right ventricular outflow obstruction).
• Beta-blocker may be used.
• If medical therapy fails, emergency surgical shunt may be considered.
Prognosis of TOF
Prognosis is good after surgery, especially if operation is done in childhood. Restenosis, recurrence
of septal defect and rhythm disorder may occur after surgery. So, regular follow-up is
required in every case.