TOF.pdf

PAEDIATRICS AND CHILD HEALTH
• Paediatrics and Child Health
• Tetralogy of Fallot (TOF)
Dr. Chongo Shapi (BSc.HB, MBChB)
- Medical Doctor.
3/20/2022 Dr. Chongo Shapi, BSc.HB, MBChB, CUZ. 1

Introduction
• Tetralogy of Fallot (TOF) is one of the most common
cyanotic CHDs
• Patients with TOF initially present with cyanosis
shortly after birth, thereby attracting early medical
attention
• It is thus also known as the blue baby syndrome (BBS)
• TOF comprises the following 4 typical features:
1. Overriding aorta
2. Right infundibular stenosis or RT ventricular outflow
tract obstruction (RVOTO)
3. Right ventricular hypertrophy (RVH)
4. Ventricular septal defect (Right to left shunt)
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Dr. Chongo Shapi, BSc.HB, MBChB, CUZ.
.
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Historical Information
• Louis Arthur Fallot, after whom the name
tetralogy of Fallot is derived, was not the first
person to recognize the condition
• Niels Stensen first described it in 1672; however, it
was Fallot who first accurately described the
clinical and complete pathologic features of the
defects
• Although the disorder was clinically diagnosed
much earlier, no treatment was available until the
1940s

• Cardiologist Helen Brooke Taussig recognized that
cyanosis progressed and inevitably led to death in
infants with tetralogy of Fallot
• She postulated that the cyanosis was due to
inadequate pulmonary blood flow
• Her collaboration with Alfred Blalock with aid from
his assistant surgical technician Vivien Theodore
Thomas led to the first type of palliation for these
infants
• In 1944, Blalock with aid through his assistant surgical
technician operated on an infant with tetralogy of
Fallot and created the first Blalock-Thomas-Taussig
shunt between the right subclavian artery and the
right pulmonary artery
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Dr. Helen Brooke Taussig

Alfred Blalock
(April 5, 1899 – September 15, 1964)
• Was a 20th-century American surgeon most
noted for his research on the medical condition
of shock and for the development of the Blalock-
Thomas-Taussig Shunt
• This is a surgical procedure he developed
together with surgical technician Vivien Thomas
and pediatric cardiologist Helen Taussig to relieve
the cyanosis from Tetralogy of Fallot—known
commonly as the blue baby syndrome
• That operation ushered in the modern era of
cardiac surgery

Dr. Vivien Theodore Thomas
(August 29, 1910 – November 26, 1985)
• Was an African-American surgical technician who
developed the procedures used to treat blue baby
syndrome in the 1940s
• He was the assistant to surgeon Alfred Blalock in
Blalock's experimental animal laboratory at Vanderbilt
University in Nashville, Tennessee, and later at the
Johns Hopkins University in Baltimore, Maryland
• He served as supervisor of the surgical laboratories at
Johns Hopkins for 35 years
• In 1976 Hopkins awarded him an honorary doctorate
and named him an instructor of surgery for the Johns
Hopkins School of Medicine

• Without ANY education past high
school, Dr. Thomas rose above
poverty and racism to become a
cardiac surgery pioneer and a
teacher of operative techniques
to many of the country's most
prominent surgeons
• He was the first African American
without a doctorate to perform
open heart surgery on a white
patient in the United States
• There is a television film based on
his life entitled Something The
Lord Made which premiered May
2004 on Home Box Office (HBO)

Helen Brooke Taussig
(May 24, 1898 – May 20, 1986)
• Was an American cardiologist, working in Baltimore and
Boston who founded the field of pediatric cardiology
• Notably, she is credited with developing the concept for a
procedure that would extend the lives of children born with
TOF
• This concept was applied in practice as a procedure known as
the Blalock-Thomas-Taussig shunt
• The procedure was developed by Alfred Blalock and Vivien
Thomas, who were Taussig's colleagues at the Johns Hopkins
Hospital
• Taussig is also known for her work in banning thalidomide
and was widely recognized as a highly skilled physician
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Other shunts + Repair Operations
• The pioneering Blalock-Taussig shunt surgical
technique opened a new era in neonatal cardiac
surgery
• Development of the following shunts followed:
- Potts shunt (from the descending aorta to the left
pulmonary artery)
- Glenn shunt (from the superior vena cava to the
right pulmonary artery)
- Waterston shunt (from the ascending aorta to the
right pulmonary artery) followed

• Scott performed the first open correction in 1954
• Less than half a year later, Lillehei performed the
first successful open repair for tetralogy of Fallot
using controlled cross-circulation, with another
patient serving as oxygenator and blood reservoir
• The following year, with the advent of
cardiopulmonary bypass by Gibbons, another
historic era of cardiac surgery was established
• Since then, numerous advances in surgical
technique and myocardial preservation have
evolved in the treatment of tetralogy of Fallot

Clinical Presentation
• Infants
a. With mild degrees of right ventricular outflow
obstruction
- Initially have heart failure caused by a ventricular-
level left-to-right shunt
- Cyanosis is not present at birth
- With increasing hypertrophy of the right ventricular
infundibulum and patient growth, cyanosis occurs
later in the 1st year of life
- Cyanosis is most prominent in the mucous
membranes of the lips and mouth and in the
fingernails and toenails
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b. With severe degrees of right ventricular outflow
obstruction
- Neonatal cyanosis is noted immediately
- Pulmonary blood flow may be dependent on flow
through the ductus arteriosus
- When the ductus begins to close in the 1st few hours
or days of life, severe cyanosis and circulatory collapse
may occur
Older children who have not undergone surgery:
- Dusky blue skin
- Gray sclerae with engorged blood vessels, and
- Marked clubbing of the fingers and toes

Infants/Toddlers:
• Dyspnea occurs on exertion
• Infants and toddlers play actively for a short time and
then sit or lie down
• Older children may be able to walk a block or so
before stopping to rest
• Characteristically, children assume a squatting
position for the relief of dyspnea caused by physical
effort; the child is usually able to resume physical
activity within a few minutes
• These findings occur most often in patients with
significant cyanosis at rest
• Tet spells are a particular problem in the first 2 years
of life

Paroxysmal Hypercyanotic Attacks
• Also called hypoxic, “blue,” or “tet” spells
• Are a particular problem during the 1st 2 yr of life
• The infant becomes:
- Hyperpneic and restless
- Cyanosis increases
- Gasping respirations ensue
- Syncope
• The spells occur most frequently in the morning
on initially awakening or after episodes of
vigorous crying

• Temporary disappearance or a decrease in
intensity of the systolic murmur is usual
• This is due to that flow across the right ventricular
outflow tract diminishes
• The spells may last from a few minutes to a few
hours but are rarely fatal
• Short episodes are followed by generalized
weakness and sleep
• Severe spells may progress to unconsciousness
and, occasionally, to convulsions or hemiparesis
• The onset is usually spontaneous and
unpredictable

• Spells are associated with reduction of an already
compromised pulmonary blood flow
• When this is prolonged, results in severe systemic
hypoxia and metabolic acidosis
• Infants who are only mildly cyanotic at rest are
often more prone to the development of hypoxic
spells
• This is because they have not acquired the
homeostatic mechanisms to tolerate rapid
lowering of arterial oxygen saturation, such as
polycythemia
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Factors Worsening Cyanosis in TOF
• Acidosis
• Stress
• Dehydration
• Infection
• Posture
• Exercise
• Beta adrenergic agonists

Complications
1. Paradoxical emboli resulting in cerebral
thromboses (Strokes)
2. Polycythaemia (phlebotomy and volume
replacement with albumin when HCT > 65%)
3. Iron deficiency anemia, frequently with Hb and
HCT levels in the normal range (but too low for
cyanotic heart disease)
4. Brain abscess with there attendant risks e.g.
seizures, ICP. Confirmed by CT/MRI
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5. Bacterial endocarditis in right ventricular
infundibulum or on the pulmonic, aortic, or, rarely,
tricuspid valves. Prophylaxis before surgery vital
6. Heart failure is not a usual feature. It may occur
in a young infant with “pink” or acyanotic tetralogy
of Fallot

Management

Investigations
• Diagnostic
1. CXR
2. ECG
3. Echo
• Supportive
1. FBC/DC
2. U/Es + Creatinine
3. LFTs

CXR: Boot-shaped or wooden shoe
(“coeur en sabot”) heart
Why this shape?
- Hypertrophied RV causes
the rounded apical shadow
to be uptilted so that it is
situated higher
above the diaphragm than
normal
- The proximal aorta is larger
than normal
- Diminished pulmonary trunk
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• ECG
- RAD
- RVH
- Dominant R wave in right precordial chest leads (Rs, R, qR,
qRs) or an RSR′ pattern
- Positive T wave in leads V3R and V1
- P wave is tall and peaked or sometimes bifid
• ECHO : establishes the diagnosis and provides information
about
- Extent of aortic override of the septum
- Location and degree of the right ventricular outflow tract
obstruction
- Size of the proximal branch pulmonary arteries
- Side of the aortic arch
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Treatment of TOF
• Medical
- Manage the spells
- Complications
• Surgical

Surgery in TOF
• Done around 1-2 yrs
A. Primary repair is preferred (ideal)
- Usually under cardiopulmonary bypass
B. Palliative procedures are done if primary is
contraindicated
- Modified Blalock-Taussig-Thomas shunt
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• Contraindications to primary repair:
1. Presence of an anomalous coronary artery
2. VLBW
3. Small pulmonary arteries
4. Multiple VSDs (Swiss cheese appearance)
5. Multiple co-existing intracardiac
malformation
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Blalock-Taussig-Thomas shunt
Blood shunting left to
right across the shunt
from the right
subclavian artery to the
right pulmonary artery
increases total PBF and
results in a higher
oxygen saturation than
would exist without the
shunt
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• Postoperative complications after a Blalock-
Taussig-Thomas shunt:
1. Chylothorax
2. Diaphragmatic paralysis
3. Horner’s syndrome

Management of a Tet Spell
1. Place the infant on the mother’s abdomen or
shoulder in the knee-chest position while making
certain that the infant's clothing is not constrictive
- This provides a calming effect and decreases VR
and increases PVR
- This is similar to TOF child squatting
2. Administer O2
- This is of little value as the primary abnormality is
intracardiac shutting of blood and reduced PBF
- Hence, this will not reverse the cyanosis
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3. IV bolus of NS at 20mL/kg
4. Inject morphine sulphate SC or IM about 0.1-0.2
mg/kg
- This reduces ventilatory drive and decrease VR
5. IV Beta blockers are also helpful. They decrease
right ventricular infundibular spasms
- Propranolol (0.1-0.2 mg/kg)
- Esmolol

6. Give vasopressors e.g. IV phenylephrine (0.02 mg/kg)
or epinephrine:
- Increase PVR
- Improve right ventricular outflow
- Decrease the right-to-left shunt
7. Give NaHCO3 to correct metabolic acidosis which
develops when arterial PO2 is <40 mm Hg
8. General anaesthesia is the last resort. Call
anaesthetists while patient has been given
vasopressors

Thanks
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33

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