Tetralogy of Fallot is a congenital heart defect characterized by four anatomical abnormalities: pulmonary stenosis, ventricular septal defect, overriding aorta, and right ventricular hypertrophy. It is one of the most common cyanotic congenital heart diseases. Presentation varies from cyanosis and failure to thrive in infants, to exertional dyspnea in older children and adults with milder cases. Diagnosis involves echocardiography, chest x-ray, and cardiac catheterization. Management includes oxygen supplementation, medications to relieve cyanotic spells, and ultimately complete repair surgery.

1. TOF

2. TOF
• Tetralogy of Fallot is one of the conotruncal family of heart lesions in
which the primary defect is an anterior deviation of the infundibular
septum (the muscular septum that separates the aortic and
pulmonary outflows).
• Prevelence - 0.262 per 1000 live birth and accounts for 6-10% of all
CHD
• More common in males

3. Anatomical Components
The consequences of conotruncal septal deviation are the 4 components of
ToF
(1) Obstruction to right ventricular outflow (pulmonary stenosis)
(2) Malalignment type of ventricular septal defect (VSD)
(3) Dextroposition of the aorta so that it overrides the ventricular septum
(4) Right ventricular hypertrophy
Pentalogy of Fallot ToF+ ASD
Trilogy of Fallot ASD + PS + RVH
Pink ToF ToF without visible cyanosis

4. Embryogenesis
• Malalignment of conal septum ends up in an obstructive pulmonary
outflow tract.
• Failure of normal growth of subpulmonary infundibulum leading to
persistent patency of interventricular foramen results in typical VSD
of ToF.
• More the anterior and superior displacement of conal septum, more
pronounced is the aortic override and PS.
• Aortic override if more than 50%, it can be classified under double
outlet right ventricle

5. Embryogenesis
• Obstruction to pulmonary arterial blood flow may be at :
1. Right ventricular infundibulum (subpulmonic area)
2. Pulmonary valve, or
3. Small main pulmonary artery, or
4. Branch pulmonary artery stenosis.
• Complete obstruction of right ventricular outflow (tetralogy with
pulmonary atresia) is classified as an extreme form of tetralogy of
Fallot.
• The degree of pulmonary outflow obstruction determines the degree
of the patient’s cyanosis and the age of first presentation.

6. Emeee EMBRYOGENESIS

7. Syndromic Association
• In 12% of cases chromosomal anamolies are seen
1. Down syndrome
2. Patau syndrome
3. Edwards syndrome
• Microdeletion of chromosome 22q 11.2
1. DiGeorge syndrome/CATCH 22
• Single gene defect
1. Alagille syndrome (JAGGED1 gene mutation)
• Low mutations in NKX2.5 – 4% and FOG2- 4%
• Association
1. CHARGE syndrome
2. VACTREL association
Recurrence risk for CHD among siblings of ToF patient -3%

8. Associated Cardiovascular Anamolies
• ASD - 9%
• PDA -5.4%
• Right sided aortic arch-20%
• Persistent LSVC* *- 8%
• Congenital absence of pulmonary valve
• Absence of branch pulmonary artery
• Anomalous origin of LAD from RCA -4%
**LSVC-Left superior vena cava

9. Associated Cardiovascular Anamolies
•Aberrant origin of right subclavian artery- 0.3%
• Congenital heart block- 0.2%
• Vascular ring -0.2%
• Absent RSVC* -0.2%
• Juxtaposition of atrial appendages
• Dextrocardia -1.4%
*RSVC-Right superior vena cava

10. Clinical Presentation
• The timing and features of presentation depends on degree of right
ventricular outflow obstruction.
• Patients with severe obstruction will present earlier with cyanosis. This
may be as early as the immediate newborn period. With closure of ductus
arteriosus severe cyanosis and circulatory collapse may occur.
• Usual presentation starts by the age of 4-6 months with cyanosis and
clubbing, before that child may present as case of VSD with respiratory
infection and heart failure.

11. Clinical Presentation
• Those with mild to moderate degree obstruction present late in adulthood,
the so called Pink ToF
• Infants may present directly in hyper cyanotic spells
• Older children’s may present with exertional dyspnoea
• Characteristic posture assumed is squatting
To increase systemic resistance
To decrease venous return
Which in turn decreases R -> L shunt and hypoxia.
• Squatting is of diagnostic importance in ToF
• Rarely haemoptysis may occur due to rupture of bronchial collaterals.

12. Clinical Examination
• Most infants are smaller than expected for age- FTT
• Infundibular stenosis worsens as infant grows so that previously pink
baby turns blue
• Central cyanosis and clubbing
• In case of pulmonary atresia, cyanosis may be absent due to multiple
major aortopulmonary collateral arteries (MAPCAs)
• Signs of various associated syndrome may be present

13. Clinical Examination
Cyanosis and Clubbing

14. Clinical Examination
• Pulse and blood pressure is usually normal
• Quiet precordium.
• Precordial bulge because of long standing RVH.
• A prominent right ventricular impulse, parasternal heave and
epigastric pulsation are present.
• Systolic thrill at left parasternal border in 2nd intercostal space may be
felt.

15. Clinical Examination
• S1 is normal.
• The 2nd heart sound (S2) is usually single because the pulmonary
component (P2) is markedly faint.
• Harsh ejection systolic murmur at the pulmonary area.
• Murmur may be widely transmitted, especially to lungs.
• The murmur in tetralogy is due to the pulmonary stenosis, intensity
of murmur is inversely proportional to severity of PS.

16. Clinical Examination
• Murmur disappears during cyanotic spell.
• VSD is usually silent because it is large and has no pressure gradient.
• Continuous murmur can be heard over the back due to systemic-
pulmonary collaterals if present.

17. HYPERCYANOTIC SPELL TET SPELL
CYANOTIC SPELL
BLUE SPELL
PARADOXICAL HYPER
APNOEA
ANOXIC SPELL
SYNCOPAL ATTACK

18. Cyanotic spells
• It is a paediatric emergency which can be fatal
• Peak incidence between 2-6 months
• Episodes beyond 2 yrs of age are rare
• About 40% of children with cyanotic CHD develop this spell
• Initiated by feeding, crying, bowel movements, or shortly after infant
wakes up
• Paroxysm of hyperpnoea
• Increase in cyanosis and decreased intensity of murmur

19. Mechanism responsible for rare occurrence
in children > 2yrs
• The child begins to squat by habit as soon as he feels breathless
• Maturity of respiratory centers
• Development of collaterals
• Fibrosis of infundibulum prevents it developing a spasm

20. Cyanotic Spells
Cyanotic spell is an important manifestation of ToF during first 2 yrs of life.
Theories for mechanism of cyanotic spell
1. Wood’s theory: Dynamic pulmonary obstruction.
2. Catecholamine release leading to tachycardia, increased myocardial
contractility and infundibular spasm.
3. Guntheroth’s theory: Hyperpnoea.
4. Morgan’s theory: Immature vulnerable respiratory centre overreacting
to hypoxia.
5. Young’s theory: Atrial tachycardia.
6. Kothari’s theory- stimulation of mechanoreceptors in right ventricle.

21. Mechanism of Cyanotic Spell

22. Squatting

23. increased SVR( kinking of major arteries) in presence of fixed
pulmonary outflow resistance
Decreased R to L flow and more RV blood is pushed into PA
Increased oxygenated blood to LV
DECREASED HYPERVENTILATION

24. SQUATTING EQUIVALENT

25. MANAGEMENT
• OXYGEN – has little effect or arterial saturation as these patients have
a central R to L shunt.
• administer oxygen in highest possible concentration
• MORPHINE
• Dose – 0.2mg/kg sc or 0.05to 0.1mg/kg IV slowly over 10 mins
• Suppresses respiratory center and abolishes hyperpnoea
• Has relaxing effect on sub-pulmonary infundibulum – via CNS or peripheral
vagotonic effect
• Sedates the patient thus reducing release of NE

26. MANAGEMENT
• SODIUM BICARBONATE – dose – 1meq/kg IV
• dose can be repeated after 15 to 20 minutes
• Reduces the respiratory center stimulation effect of acidosis
• PHENYLEPHRINE – Dose – 0.02mg/kg IV
• Increases systemic vascular resistance
• KETAMINE – dose – 1 -3 mg/kg IV over 30 minutes
• Increases the SVR and sedates the child
• NORADRENALINE infusion @ 0.01-0.05 mcg/kg

27. MANAGEMENT
• Fluids – bolus NS of 20ml/kg can be repeated three times to correct
shock and acidosis and as well decrease hyper viscosity which
improves pulmonary blood flow
• PROPANOLOL – dose – 0.01-0.05mg/kg (max of 0.1mg/kg)
• It reduces the heart rate and thus may reverse the spell

28. MANAGEMENT
• IV Esmolol ( t ½- 9minutes)
• Negative inotropic effect relaxes infundibular spasm
• Dose – 0.5mg/kg over 1 minute followed by 50mcg/kg/min X 4 minutes
• Infusion – 50 -200mc/kg/min

29. Management
• Packed red cell transfusion
• Maintain PCV of > 45 to 50 such that oxygen delivery to tissues is adequate
• Correct hypoglycemia
• Intubation and controlled ventilation – for severe and refractory spells
in order to enable sedation and paralysis which eventually decreases
oxygen demand
• Alert cardiac surgeon for emergency surgical intervention ( B T shunt)

30. Investigations
• CBC- Polycythemia and anemia
• X ray chest
• ECG
• Echocardiography with Doppler
• Cardiac CT angiogram
• Cardiac catheterization
• Chomosomal microarray : if genetic syndromes suspected

31. X - Ray Chest
• It shows ‘boot’ shaped heart with upturned cardiac apex
due to RVH and concave pulmonary arterial segment.
• Oligaemic lung fields due to reduced pulmonary vascular
markings.
• Right sided aortic arch is present in 20% cases

32. ECG
Electrocardiogram of an infant with right ventricular
hypertrophy (tetralogy of Fallot). Note the tall R waves in the
right precordium and deep S waves in V6. The positive T waves
in V4R and V1 are also characteristic of right ventricular
hypertrophy.

33. Subcostal view of a child with TOF
demonstrating RVOT obstruction Continuous wave Doppler
demonstrating raised velocity
across the RVOTO

34. This parasternal long-axis 2-dimensional view demonstrates
anterior displacement of the outflow ventricular septum that
resulted in stenosis of the subpulmonic right ventricular
outflow tract, overriding of the aorta with ventricular septal
defect

35. Echocardiography
Complete Echo study must address
• The location and number of VSDs
• The anatomy and severity of RVOTO
• Anatomy of main pulmonary and branch pulmonary arteries
• Coronary arteries, LAD arises from RCA and crosses RVOT in 5%
• Aortic arch
• Associated anomalies like ASD, PDA

36. Cardiac CT angiogram
• Cardiac CT angiogram: to delineate anatomy especially if coronary or
vascular abnormalities are suspected (e.g. MAPCAs)

37. Interventional Radiology
• Cardiac catheterization: done
as part of the pre-op assessment
to measure haemo dynamics
and delineate anatomy
• Selective right ventriculography
• Aortogragh or coronary
arteriography
The figure shows lateral view of a selective right ventriculogram
in patient with the tetralogy of Fallot. The arrow points to an
infundibular stenosis that is below the infundibular chamber
(C). The narrowed pulmonary valve orifice is seen at the distal
end of the infundibular chamber

38. Complications
Left untreated, TOF may cause significant morbidity and mortality
which includes:
• Polycythaemia
• Cerebral thrombosis
• Cerebral abscess
• Infective endocarditis
• Congestive cardiac failure in pink ToF

39. Treatment
• Treatment of tetralogy of Fallot depends on the severity of the right
ventricular outflow tract obstruction.
• Infants with severe tetralogy require urgent medical treatment and
surgical intervention in the neonatal period.
• Therapy is aimed at providing an immediate increase in pulmonary
blood flow to prevent the sequelae of severe hypoxia.

40. • Neonates with marked right ventricular outflow tract obstruction may
deteriorate rapidly because, as the ductus arteriosus begins to close,
pulmonary blood flow is further compromised.
• IV prostaglandin E1 (0.01-0.20 μg/kg/min), a potent and specific
relaxant of ductal smooth muscle, causes dilation of the ductus
arteriosus and usually provides adequate pulmonary blood flow until
a surgical procedure can be performed.

41. • This agent should be administered intravenously as soon as cyanotic
congenital heart disease is clinically suspected and continued through
the preoperative period and during cardiac catheterization.
• As prostaglandin can cause apnea, an individual skilled in neonatal
intubation should be readily available.

42. Treatment
Medical management in TOF mainly directed towards
• Preventing cyanotic spells
• Avoiding problems with anaemia, polycythemia and complications
like brain abscess or infective endocarditis.
• Anaemia correction by iron supplementation and nutritional
supervision.
• Polycythemia needs correction.
• Oral propranolol in dosage of 1-4mg/kg/day in three or four divided
doses to prevent cyanotic spells until surgical correction is done

43. Management of TET Spell
• Cyanotic spell Is usually self limiting and lasts less than 15-30 mins
but sometimes prolonged .
• Depending on the frequency and severity of hypercyanotic attacks,
one or more of the following procedures should be instituted in
sequence.
1) Placement of the infant on the abdomen in the knee-chest position
or in mothers lap with flexion of knee and hip joint.
This increases systemic vascular resistance
Decreases the desaturated systemic venous return

44. Knee Chest Position

45. Management of TET Spell
2) Calm the child.
• The ideal sedative is morphine.
• It causes respiratory centre suppression
• and sedation there by reducing hyperpnoea.
• It reduces the ventilatory drive and
• decreases systemic venous return (venodilator).
• This will diminish the release of catecholamines, increase the period of
right ventricular filling by decreasing the heart rate and relaxing the
infundibulum.

46. Management of TET Spell
The dose of morphine is 0.1mg/kg and it can be given intravenous (IV),
intramuscular (IM) or subcutaneous.
Alternative sedatives are
• Midazolam 0.05-0.1mg/kg (IV, intranasal or intrarectal)
• Fentanyl 1-2 mcg/kg IV.
• Ketamine has dual benefit of causing sedation and increasing SVR.
The dose is 0.25-1mg/kg IV or IM.

47. Management of TET Spell
3) 100% Oxygen supplementation causes pulmonary vasodilation and
hence decreases the pulmonary vascular resistance (PVR).
4) Prompt administration of IV fluid to be done increase systemic
resistance. Initially, fluid is given as a bolus of 10-20ml/kg up to
60ml/kg. Bolus fluid should be isotonic saline.
5) Sodium bicarbonate in a dose of 1-2 meq/kg IV is given slowly to
correct metabolic acidosis.
This may reduce hyperpneoa and pulmonary vascular resistance
caused by hypoxia and acidosis.
It can be repeated in 10-15 minutes.

48. Management of TET Spell
6) Beta blockers inj propranolol is given in a dose of 0.1-0.2 mg/kg IV
over 5 minute. It can be repeated once after 15 minutes. It decreases
the heart rate, infundibular spasm and increases SVR.
Alternatively metoprolol in a dose of 0.1mg/kg over 5 minutes or
esmolol in a dose is 0.5mg/kg over 1 minute and then as an infusion
of 50-200mcg/kg/min upto 48 hrs

49. Management of TET Spell
• In refractory cases vasopressors can be given to increase the SVR
and promote the redirection of blood flow through pulmonary
circulation.
• Phenylephrine an alpha adrenergic agonist can be given in a dose
of 5-20mcg/kg IV bolus, followed by an infusion of 0.1-
0.5mcg/kg/min

50. 8) Avoiding actions that agitate child like vigorous examination, repeated
venipuncture.
9) Avoid inotropes (dopamine, dobutamine, digoxin) and diuretics.
10) If spell is persistent or refractory then intubation and mechanical
ventilation may be required.
11) Emergency BT shunt may be required in persistent cases.

51. Catheter Intervention in ToF
• Catheter based interventions identify and apply most effective, but
least invasive procedure to most difficult pathologies of ToF
Example –
• balloon dialatation of pulmonary valve stenosis
• balloon dialatation of pulmonary artery stenosis
• stenting of RVOTO

52. Palliative Procedures
• B T shunt
• Modified B T shunt
• Waterston shunt
• Potts shunt
• Infundibular resection(Brock’s procedure)
• Central interposition tube graft
• Relief of RVOTO without closure of VSD or with fenestrated VSD closure.

53. Primary Repair
• Ideal age for primary repair is controversial.
• Most centre prefer by the age of 1yr.
• Various intracardiac approaches have been proposed.
• Patient with repaired ToF have the potential to lead normal life and
excellent cardiac function

54. Contraindications to Primary Repair
• Weight less than 3kg.
• Severe hypoplasia of pulmonary annulus.
• Associated anamolies.
• Multiple VSDs.
• Anomalous coronary arteries.

55. Total Surgical Repair
• Usual age for correction by 1 yr, to be decided on individual basis .
• Consists of relief of RVOTO by infundibular resection.
• Patch closure of VSD.
• Pulmonary valvotomy if valve is stenotic.
• The surgical risk of total correction -5%.

56. Total Surgical Repair
Long term complications after surgery
• Progressive pulmonary regurgitation leading right ventricular
dilatation
• Residual RVOTO
• Conduction defects
• Atrial arrythmias
• Risk of sudden cardiac death 1-5%
Life long surveillance is needed

57. Course of Disease
Survival without treatment