Tetralogy of Fallot (TOF)

Dr. Syed Kamrul Hasan
Medical Officer, NICU
Sylhet Women’s Medical College Hospital

INTRODUCTION
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 consequences of this deviation are the 4
components:

EPIDEMIOLOGY
Tetralogy of Fallot occurs approximately 400
times per million live births. It accounts for 7 to
10% of all congenital heart abnormalities, making
it the most common cyanotic heart defect. Males
and females are affected equally. Genetically it is
most commonly associated with Down's
syndrome and DiGeorge syndrome.

HISTORY
 Tetralogy of Fallot was initially described in 1671
by Niels Stensen.
 A further description was published in 1888 by the
French physician Louis Arthur Fallot, after whom it
is named.
 In 1924, Maude Abbott coined the term "tetralogy
of Fallot".

French physician
Étienne- Louis-
Arthur Fallot, who
first described TOF
in the late 19th
century.

 The first surgical repair was carried out in 1944
at Johns Hopkins.The procedure was conducted
by surgeon Alfred Blalock and cardiologist Helen
B. Taussig.
 15-months old Eileen Saxon was the first person
to receive a Blalock-Thomas-Taussig shunt.
 The first total repair of tetralogy of Fallot was
done by a team led by C. Walton in 1954 on an
11 years old boy.

RISK FACTORS
 Poor maternal nutrition
 Viral illness during pregnancy
 Parent having tetralogy of fallot
 Children born to mother with Polyketonuria
 Presence of down syndrome

CAUSE
It’s cause is thought to be due to environmental or
genetic factors or a combination.
It is associated with chromosome 22 deletions
and DiGeorge syndrome. Specific genetic
associations include :
JAG1,NKX25, ZFPM2,VEGF,NOTCH1, TBX1,
and FLT4.

DEVELOPMENT OF TOF
A. During the fifth week,
pairs of opposing ridges
appear in the truncus (right
superior truncus swelling &
left inferior truncus
swelling).
B. Hence, while growing
toward the aortic sac, the
swellings twist around each
other, foreshadowing the
spiral course of the future
septum.

C. After complete
fusion, the ridges
form the
aorticopulmonary
septum, dividing the
truncus into an aortic
and a pulmonary
channel.

 TOF, is due to an
unequal division of the
conus resulting from
anterior displacement of
the conotruncal septum.
 Defect in bulbus cordis
and truncus arteriosus.

PATHOPHYSIOLOGY
Physiologically the pulmonary stenosis causes
concentric right ventricular hypertrophy without
cardiac enlargement and an increase in right
ventricular pressure.
When the right ventricular pressure is as high as
the left ventricular or the aortic pressure, a right
to left shunt appears to decompress the right
ventricle.

Once the right and left ventricular become
identical, increasing severity of pulmonary
stenosis reduces the flow of blood into the
pulmonary artery and increases the right to left
shunt.
As the systolic pressures between two ventricle
are identical there is little or no left to right shunt
and the VSD is silent.

The flow from the right ventricle into the
pulmonary artery occurs across the pulmonary
stenosis producing an ejection systolic
murmur
More severe the pulmonary stenosis, the less
the flow into the pulmonary artery and the bigger
the right to left shunt, more the cyanosis

Thus the severity of cyanosis is directly
proportional to the severity of pulmonary stenosis
The VSD of TOF is always large enough to
allow free exit to the right to left shunt
Thus Congestive failure not occurs in TOF.

CLINICAL MANIFESTATIONS
Clinical findings are variable & mainly depends
on the degree of right ventricular outflow
obstruction.
 Cyanosis :
 Patient with mild obstruction are minimally
cyanotic or even acyanotic
 Those with maximal obstruction are deeply
cyanosed since birth
 Most have progressive cyanosis by 4 months of
age

 Paroxysmal Hypercyanotic Attacks :
This is the hallmark of sever TOF & usually
occurs during first 2 years of life, most commonly
by 4-6 months of age. Spells occur most
frequently in the morning on awakening or after
episodes of vigorous cry. The attacks are due to
further reduction of an already compromized
pulmonary blood flow & more severe systemic
hypoxia.

Cyanotic Spells are characterized by
 Sudden onset of dyspnoea. Sometimes gasping
respiration & syncope
 Sudden deepening of cyanosis
 Alteration in consciousness, from irritability to
syncope.
 Sometimes convulsion & hemiparesis
 Temporary disappearance or decrease in the
intensity of the systolic murmur at pulmonary area
 Metabolic acidosis

 Easy fatigability & dysponea on exertion
 Squatting is of diagnostic significance & is
highly typical of infants with TOF
 Failure to thrive
Squatting
position

PHYSICAL EXAMINATION
 Varying degrees of cyanosis
 Conjunctiva are congested
 Clubbing of the fingers and toes occurs after 3
months of age and is proportional to the level of
cyanosis.
 Stunted growth
 Precordium may be bulged due to right
ventricular hypertrophy.

Clubbing of the fingers and toes

 Apex beat is tapping in character, but not shifted
 A systolic thrill may be palpable at the left sternal
border, with a harsh midsystolic murmur in that
location.
 The shorter the murmur, the more severe the
infundibular pulmonary stenosis.
 Left parasternal heave may be present
 The first heart sound (S1) is usually normal

 Second heart sound is characteristically single &
loud, because the pulmonary component is too
soft to be heard.
 An ejection systolic murmur is heard at
pulmonary area
 A continuous murmur is heard if a PDA or large
collateral vessels are present.

 Cardiac findings in cyanotic tetralogy of Fallot:
A long ejection systolic murmur at the upper and mid
left sternal border and a loud, single S2 are
characteristic auscultatory findings of TOF.

DIAGNOSIS
Based on the clinical features and
relevant investigation

INVESTIGATIONS
 Complete blood counts :
 Haemoglobin & haematocrit values are usually
elevated which is proportional to the degree of
cyanosis
 PBF shows microcytic hypochromic anaemia

 Chest X-ray
 Boot shaped heart (due to ventricular
hypertrophy). It means apex is lifted up.
 Concavity in the region of pulmonary artery
 Right sided aortic arch.
 Oligaemic lung fields.
 Hilar vessels are few,
 Lung vessels also few.

 Electrocardiogram
 Right axis deviation and evidence of right
ventricular hypertrophy.

 Echocardiography
Confirms the diagnosis and provides
information about the extent of aortic override of
the septum, the location and degree of the right
ventricular outflow tract obstruction, the size of
the pulmonary valve annulus and main and
proximal branch pulmonary arteries and the side
of the aortic arch.

 PLAX view showing the overriding aorta and a
large subaortic VSD (star).
 RVH is also present

Color flow imaging showing VSD jet

 Cardiac catheterization
 To assess the anatomy of RVOT and main PA
branches, RV and LV function, site and size of
VSD and competence of aortic valve.
 Identical systolic pressure in RV and LV and
low systolic pressure in PA (diagnostic of TOF)

 Aortography or coronary arteriography
outlines the course of the coronary arteries. In 5-
10% of patients with the tetralogy of Fallot,
coronary artery abnormalities may be present

COMPLICATIONS
 Hypercyanotic Spells
 Sever polycythaemia
 Cerebral thrombo-embolism & stroke: usually
occurring in the cerebral veins or dural sinuses
and occasionally in the cerebral arteries.
Thromboses occur most often in patients
younger than 2 years.

 Brain abscess : As deoxygenated blood enters
the systemic circulation & brain , bypassing
lungs without clearing the germs by pulmonary
scavenger cells. Patients with a brain abscess
are usually older than 2 years. The onset of the
illness is often insidious and consists of low-
grade fever or a gradual change in behavior, or
both.

Some patients have an acute onset of symptoms
that may develop after a recent history of
headache, nausea, and vomiting. Seizures may
occur; localized neurologic signs depend on the
site and size of the abscess and the presence of
increased intracranial pressure. CT or MRI
confirms the diagnosis. Antibiotic therapy may
help keep the infection localized, but surgical
drainage of the abscess is usually necessary.

 Bacterial endocarditis may occur in the right
ventricular infundibulum or on the pulmonic,
aortic, or, rarely, tricuspid valves. Endocarditis
may complicate palliative shunts or, in patients
with corrective surgery, any residual pulmonic
stenosis or VSD.
 Delayed growth, development & puberty
 Others : Hyperuricemia & gout
Relative IDA
Bleeding disorders

ASSOCIATED ANOMALIES
Tetralogy of Fallot may present with other
anatomical anomalies, including:
 Stenosis of the left pulmonary artery, in 40%
 A bicuspid pulmonary valve, in 60%
 Right-sided aortic arch, in 25%
 Coronary artery anomalies, in 10%
 PDA may be present
 Congenital absence of the pulmonary valve

 Absence of a branch pulmonary artery
 A patent foramen ovale or atrial septal defect, in
which case the syndrome is sometimes called a
pentalogy of Fallot
 An atrioventricular septal defect partially or
totally anomalous pulmonary venous return.

TREATMENT
Counsel the parents about disease, treatment
option & prognosis
Treatment options :
 Medical
 Surgical

MEDICAL
 Neonate with severe cyanosis is treated with IV
infusion of prostaglandin E1(0.05 - .1
mcgm/kg/min) to keep the ductus arteriosus
patent & thereby to improve pulmonary
circulation and is life saving.

 Treatment of cyanotic spells ( in hospital)
 Place the infant in a knee chest position
 Give O2 3-5 L/min
 Establish a calm environment by isolating the
patient

If the spell persists , give the following :
 Intravenous fluids : 10ml/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 reduce spasm

If these measures do not control the spell, then
arrange to transfer the child to ICU
 Phenylephrine :10-20mcgm/kg bolus IM or SC
followed by 0.1-0.5mcgm/kg/min IV infusion
titrated according to heart rate and blood
pressure. Phenylephrine raise systemic BP as
well as systemic vascular resistance. This will
reduce right to left shunt and ultimately promote
pulmonary blood flow.

 If the preceding steps do not relieve the spell or
if the infant is rapidly deteriorating , intubation
and ventilatory support should be given.

 Treatment at home
 Educate parents to recognize the spells and
know what to do.
 Propranolol : 0.25-1mg/kg/day orally to be
continued to prevent cyanotic spell
 Fluid & Nutrition
• Provide high calorie diets to ensure growth
• Supplement Iron 3-6 mg/kg/day elemental iron
orally to promote maturation of RBC
• Supplement vitamins & minerals

 Counsel parents to pay special attention to fluid
intake so as to prevent dehydration.
 Dehydration of any child with TOF should be
referred immediately for prompt rehydration.

SURGICAL
 Total surgical repair
Total surgical repair of TOF is a curative surgery.
Different techniques can be used in performing
TOF repair. However, a transatrial,
transpulmonary artery approach is used for most
cases. The repair consists of two main steps:
closure of the VSD with a patch and
reconstruction of the right ventricular outflow
tract.

Diagrammatic representation of surgical repair of tetralogy of Fallot.
1. Patch closure of a VSD
2. Right ventricular outflow/main pulmonary artery outflow patch
(transannular patch)

 This open-heart surgery is designed to relieve the
right ventricular outflow tract stenosis by
careful resection of muscle and to repair the VSD.
Additional reconstructive surgery may be done on
patients as required by their particular cardiac
anatomy.

 Timing of surgery in asymptomatic patients is
usually between the ages of 2 months to one
year. However, in symptomatic patients showing
worsening blood oxygen levels, severe tet-spells
(cyanotic spells), or dependence on
prostaglandins from early neonatal period (to
keep the ductus arteriosus open) need to be
planned fairly urgently.

 Surgery is now often carried out in infants one
year of age or younger with less than 5%
perioperative mortality. Post surgery, most
patients enjoy an active life free of symptoms.
Currently, long term survival is close to 90%.

Palliative surgery
 Classic Blalock-Taussing shunt: anastomosed
between the subclavian artery and the ipsilateral
PA, is usually performed for infants older than 3
months because the shunt is often thrombosed in
young infants.
Classic Blalock-
Taussing shunt

 Modified Blalock-Taussing shunt : a Gore-Tex
interposition shunt is placed between the
subclavian artery and the ipsilateral PA.
This is the most popular procedure for any age,
especially for infants younger than 3 months of
age.
Modified Blalock-
Taussing shunt

 The Waterston shunt : anastomosis between
the ascending aorta and the right PA, is no
longer performed because of a high incidence of
surgical complications.
 The Potts operation : anastomosed between
the descending aorta and the left PA, is no
longer performed either.
It may result in heart failure or pulmonary
hypertension, as in the Waterston operation.

PROGNOSIS
After successful total correction, patients are
generally asymptomatic and are able to lead
unrestricted lives. If left untreated, TOF carries a
35% mortality rate in the first year of life, and a
50% mortality rate in the first three years of life.
Patients with untreated TOF rarely progress to
adulthood.

NOTABLE CASES
 Shaun White,American professional
snowboarder and musician.
 Beau Casson , Australian cricketer
 Dennis McEldowney, New Zealand author
and publisher

TAKE HOME MESSAGE
 Tetralogy of Fallot is the most common form of
cyanotic congenital heart disease, and one of the
first to be successfully repaired by congenital
heart surgeons.
 The care of children with tetralogy of Fallot and
their transition to adult life has been a success of
modern medicine.
 Most of them now survive early repair and have
an essentially normal childhood.

Tetralogy of Fallot (TOF)

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