Tetralogy of Fallot

It is a cyanotic congenital heart disease. The components of Fallot’s tetralogy includes:

1. Ventricular septal defect (with a right-to-left shunt)
2. Right ventricular outflow tract obstruction (pulmonary infundibular stenosis)
3. Right ventricular hypertrophy
4. Overriding of aorta.

* Short and Long Cases in Clinical Medicine, HN Sarker Page: 64; Step on to Paediatrics, Md Abid Hossain Mollah, 3rd Edition Page: 125

When TOF is associated with ASD.

* Short and Long Cases in Clinical Medicine, HN Sarker Page: 64

Trilogy of Fallot is composed of

• Atrial septal defect
• Pulmonary stenosis
• Right ventricular hypertrophy

* Short and Long Cases in Clinical Medicine, HN Sarker Page: 64

In TOF, when right ventricular outflow tract obstruction is infundibular in type and mild, there is no cyanosis. It is called acyanotic Fallot.

* Short and Long Cases in Clinical Medicine, HN Sarker Page: 64

Cyanosis in TOF is aggravated during exercise, feeding or crying when it is called cyanotic spell or Fallot’s spell.

• This is the hallmark of severe TOF and usually occurs during first 2 years of life, most commonly 4-6 months of age.
• Spells occur most frequently in the morning on awakening or after episodes of vigorous cry.
• The attacks are associated with further reduction of an already compromized pulmonary blood flow & more severe systemic hypoxia and metabolic acidosis.

* Short and Long Cases in Clinical Medicine, HN Sarker Page: 64; Step on to Paediatrics, Md Abid Hossain Mollah, 3rd Edition Page: 125

This is a palliative procedure that involves an anastomosis between the subclavian artery (usually the left) to the pulmonary artery, thus bypassing right ventricular outflow obstruction to increase circulation to the lungs.

Note:

Anastomosis between subclavian artery (systemic circulation) to the pulmonary artery (pulmonary circulation).

* Short and Long Cases in Clinical Medicine, HN Sarker Page: 65; Step on to Paediatrics, Md Abid Hossain Mollah, 3rd Edition Page: 128

During exercise, there is increased pulmonary resistance and reduced systemic vascular resistance. So, there is increased right to left shunt and admixture of blood of right and left ventricles. As a result, there is reduced cerebral oxygenation, causing syncope.

* Long Cases in Clinical Medicine, ABM Abdullah Page: 237

Because of the overriding of aorta, there is admixture of blood of right and left ventricles.

• Cyanosis is absent in newborn or acyanotic Fallot’s.

* Long Cases in Clinical Medicine, ABM Abdullah Page: 238

Cyanotic spell is due to increase obstruction, as a result of increased sympathetic stimulation that occurs in exercise, feeding and crying.

* Short and Long Cases in Clinical Medicine, HN Sarker Page: 64;

• Exertion
• Upsetting due to any cause
• Sleeplessness
• Irritation to the baby
• Vigorous crying

Note:

Following can precipitate cyanotic spells¹

• Exercise
• Fever
• Stress
• Hypoxia
• Dehydration
• Acidosis

* Step on to Paediatrics, Md Abid Hossain Mollah, 3rd Edition Page: 126; ¹Short and Long Cases in Clinical Medicine, HN Sarker Page: 64 

Cyanotic spells are relieved by

• Squatting position
• High concentration of 0₂
• Injecaon morphin
• Beta blocker.

* Short and Long Cases in Clinical Medicine, HN Sarker Page: 64

• In squatting position, abdominal aorta and femoral artery are compressed.
• So, there is increased arterial resistance, which increases the pressure in the left ventricle, leading to decreased right to left shunt through VSD and increased flow through pulmonary artery.
• This reduces admixture of blood from right and left ventricles, improves pulmonary circulation, better oxygenation and relieves the child from dyspnoea and cyanotic spells.

* Long Cases in Clinical Medicine, ABM Abdullah Page: 238; Step on to Paediatrics, Md Abid Hossain Mollah, 3rd Edition Page: 126

Why there is no murmur of VSD in TOF, because VSD is large and there is equal pressure in right and left ventricles.

* Long Cases in Clinical Medicine, ABM Abdullah Page: 238

Clinical Manifestations

Clinical findings are variable and mainly depends on the degree of right venlricular outflow obstruction.

Cyanosis (due to persistently low O2 saturation in systemic circulation)

• Patients with mild obstruction are minimally cyanotic or even acyanotic (pink TOF)
• Those with maximal obstruction are deeply cyanosed since birth
• Most have progressive cyanosis by 4 months of age

Paroxysmal hypercyanotic attacks (Hypoxic spells, blue spells, Tet spells)

• This is the hallmark of severe TOF and usually occurs during first 2 years of life, most commonly 4-6 months of age.
• Spells occur most frequently in the morning on awakening or after episodes of vigorous cry.

Easy fatigability and dyspnoea on exertion

• The affected child tires easily (easy fatigability) and begins panting with any form of exertion (dyspnoea on exertion).

Failure to thrive (due to chronic hypoxaemia)

• Slow or not gaining weight

* Step on to Paediatrics, Md Abid Hossain Mollah, 3rd Edition Page: 125, 126

As follows:

• Child with growth retardation
• Clubbing
• Cyanosis
• Pulmonary ejection systolic murmur
• History of cyanotic spells during exercise (relieved by squatting).

* Long Cases in Clinical Medicine, ABM Abdullah Page: 237

The common presentations of TOF include

• Cyanotic spell during exercise, crying, feeding
• Shortness of breath
• Syncope
• Retardation of growth.

* Short and Long Cases in Clinical Medicine, HN Sarker Page: 64

As follows:

• Young children usually present with cyanotic spell (Fallot’s spell) during exertion, feeding or crying. They may become apneic and unconscious.
• In older children, Fallot’s spells are uncommon but cyanosis becomes increasingly apparent with clubbing and polycythemia. There may be Fallot’s sign.
• Shortness of breath on exertion, easy fatiguability.
• Growth retardation.
• Syncope, seizure, cerebrovascular events or even sudden death.

* Long Cases in Clinical Medicine, ABM Abdullah Page: 237

General Physical Examination

• Appearance : Cyanosis (skin, lips, and mucous membranes inside the mouth and nose looks blue)
• Conjunctiva : Congested
• Fingers and toes : Clubbing
• Pulse and blood pressure : Normal
• Oedema: Absent
• Anthropometry: Stunting

Precordium

• Inspection
  • May bc bulged due to right ventricular hypertrophy
• Palpation
  • Apex beat is tapping in character, not shifted
  • P2 is not palpable
  • Left parasternal heave may be present.
  • A systolic thrill may be felt at left upper intercostals spaces
• Auscultation
  • S1 is normal
  • S2 is loud & single
  • Added sound : A loud ejection systolic murmur is heard at pulmonary area radiating to neck originating from the turbulence at right ventricular outflow tract obstruction.

* Step on to Paediatrics, Md Abid Hossain Mollah, 3rd Edition Page: 126, 127; Short and Long Cases in Clinical Medicine, HN Sarker Page: 64

The findings of examinations are:

• Short stature
• Clubbing
• Cyanosis
• An ejection systolic murmur in pulmonary area.

* Pre-exam preparation for medicine, HN Sarker

As follows:

• Mild case—loud and prolonged murmur
• Severe case—murmur reduced or absent.

* Long Cases in Clinical Medicine, ABM Abdullah Page: 238

1. Complete blood count
2. X-ray chest
3. ECG
4. Echocardiography (confirmatory)

* Step on to Paediatrics, Md Abid Hossain Mollah, 3rd Edition Page: 127

Complete blood counts

• Haemoglobin and hematocrit values are usually elevated which is proportionate to the degree of cyanosis.
• TC & DC of WBC, Platelet counts: Normal
• PBF shows microcytic hypochromic anaemia

* Step on to Paediatrics, Md Abid Hossain Mollah, 3rd Edition Page: 127

the findings include:

1. Heart
   • Size : Not enlarged
   • Shape : Boot shaped (coeur-en-sabot) due to concavity at pulmonary conus (because of low pressure of pulmonary artery) and upturning of cardiac apex (by the hypertrophied right ventricle)
2. Lung fields
   • Looking black due to decreased pulmonary vascularity (oligaemia due to persistently less blood in pulmonary circulation)
3. Right-sided aortic arch (present in 20-25% of cases).

* Step on to Paediatrics, Md Abid Hossain Mollah, 3rd Edition Page: 125, 127; Short and Long Cases in Clinical Medicine, HN Sarker Page: 65

• Oligemic lung field means reduced pulmonary vascularities; hence it is more translucent than expected.
• Plethoric lung field means increased pulmonary blood flow.

* Pre-exam preparation for medicine, HN Sarker

The findings include:

• Right ventricular hypertrophy
• Right axis deviation
• Also there may be right atrial enlargement.

* Short and Long Cases in Clinical Medicine, HN Sarker Page: 65

Treatment

Counsel the parents about the disease, treatment options and prognosis

Medical

1. Neonates with severe cyanosis
   • IV infusion of Prostaglandin E1 (0.05 to 0.1 μg/kg/min IV) to keep the ductus arteriosus open/patent and thereby to improve pulmonary circulation and is life saving.
2. Treatment of cyanotic spell
   • Place the infant in a knee-chest position (older children usually squat spontaneously and do not develop cyanotic spells)
   • Give O2: 3-5 L/min through face mask/head box
   • Establish a calm environment by isolating the patient
   • If the spell persists, give the following
     • Intravenous fluids 10 ml/kg bolus normal saline followed by maintenance fluids
     • Morphine 0.1-0.2 mg/kg SC for keeping the child calm and for muscle relaxation
     • NaHCO3: 1 mEq/kg IV to correct acidosis
     • Propranolol 0.1 mg/kg IV which relaxes the infundibular muscle and thereby reduces spasm
     • If these measures do not control the spell, then take measure to raise systemic BP as well as systemic vascular resistance. This will promotes pulmonary blood flow.
     • Phenylephrine 10-20 μg/kg bolus IM or SC then 0. 1 ー 0. 5 μg/kg/min infusion IV titrated according to heart rate and blood pressure
     • lf the preceding steps do not relieve the spell or if the infant is rapidly deteriorating, intubation and ventilator support should be given.
3. Treatment at home
   • Propranolol : 0. 25-1 mg/kg/day orally to be continued to prevent cyanotic spells ‘
   • Fluid & nutrition
     • High calorie diets should be given to ensure growth
     • Iron supplementation: 3-6 mg/kg/day elemental iron orally
     • Vitamins and minerals supplementation
     • Counsel parents to pay special attention to fluid intake so as to prevent dehydration, haemoconcentration and thereby to reduce thromboembolism. Dehydration of child with TOF should be reffered to rehydrate promptly

Surgical

1. Total correction is the treatment of choice, can be done as early as 1 month of age (electively in between 4-6 months of age)
2. Palliative surgery (Blalock Taussig Shunt) This is done between Subclavian artery (systemic) and pulmonaiy artery (pulmonary circulation) to increase circulation to the lungs. This will improve tissue oxygenation, relieves cyanosis and allow the child to grow good enough to do complete surgical repair. This procedure is reserved for TOF with associated comorbidities e. g. other congenital anomalies or prematurity

Prophylaxis against infective endocarditis is recommended.

* Step on to Paediatrics, Md Abid Hossain Mollah, 3rd Edition Page: 127, 128

• Long term outcome of treatment of TOF depends on the size and anatomy of the pulmonary arteries.
• Prognosis is good after surgery, especially if operation is done in childhood.
• Re-stenosis, recurrence of septal defect and rhythm disorder may occur after surgery. So, regular follow-up is required in every case.

* Step on to Paediatrics, Md Abid Hossain Mollah, 3rd Edition Page: 128; Long Cases in Clinical Medicine, ABM Abdullah Page: 239

As follows:

• Infective endocarditis (common)
• Systemic thrombosis and paradoxical embolism and stroke
• Cerebral abscess (10% cases, as deoxygented blood enters the systemic circulation and brain, bypassing lungs without clearing the germs by pulmonary scavenger cells)
• Polycythemia (due to hypoxemia, and may lead to cerebrovascular accident and myocardial infarction)
• Coagulation abnormality
• Hypercyanotic spell
• Delayed growth, development and puberty (due to chronic hypoxaemia)
• Other: Hyperuricaemia and gout, relative IDA.

* Long Cases in Clinical Medicine, ABM Abdullah Page: 238; Short and Long Cases in Clinical Medicine, HN Sarker Page: 65; Step on to Paediatrics, Md Abid Hossain Mollah, 3rd Edition Page: 127,129