Tetralogy
of Fallot
Tetralogy
of Fallot (TOF or "TET") is a complex condition
of several congenital (present at birth) defects
that occur due to abnormal development of the
fetal heart during the first 8 weeks of pregnancy.
These problems include the following:
- ventricular septal
defect (VSD) - an opening in the
ventricular septum, or dividing wall between
the two lower chambers of the heart known as
the right and left ventricles.
- pulmonary (or right
ventricular outflow tract) obstruction -
a muscular obstruction in the right ventricle,
just below the pulmonary valve, that decreases
the normal flow of blood. The pulmonary valve
may also be small.
- overriding aorta -
the aorta is shifted towards the right side
of the heart so that it sits over the ventricular
septal defect.
"Tetralogy"
refers to four heart problems. The fourth problem
is that the right ventricle becomes enlarged as
it tries to pump blood past the obstruction into
the pulmonary artery.
Normally,
oxygen-poor (blue) blood returns to the right
atrium from the body, travels to the right ventricle,
then is pumped through the pulmonary artery into
the lungs where it receives oxygen. Oxygen-rich
(red) blood returns to the left atrium from the
lungs, passes into the left ventricle, and then
is pumped through the aorta out to the body.
In tetralogy
of Fallot, blood flow within the heart varies,
and is largely dependent on the size of the ventricular
septal defect, and how severe the obstruction
in the right ventricle is.
- With mild right ventricle
obstruction, the pressure in the right ventricle
can be slightly higher than the left. Some of
the oxygen-poor (blue) blood in the right ventricle
will pass through the VSD to the left ventricle,
mix with the oxygen-rich (red) blood there,
and then flow into the aorta. The rest of the
oxygen-poor (blue) blood will go its normal
route to the lungs. These children may have
slightly lower oxygen levels than usual, but
may not appear blue.
- With more serious obstruction
in the right ventricle, it is harder for oxygen-poor
(blue) blood to flow into the pulmonary artery,
so more of it passes through the VSD into the
left ventricle, mixing with oxygen-rich (red)
blood, and then moving on out to the body. These
children will have lower than normal oxygen
levels in the bloodstream, and may appear blue,
especially whenever the pressure in the right
ventricle is very high and large amounts of
oxygen-poor (blue) blood passes through the
VSD to the left side of the heart.
Tetralogy
of Fallot makes up about 5 to 7 percent of all
cases of congenital heart defects and occurs equally
in boys and in girls.
Some
congenital heart defects may have a genetic link,
either occurring due to a defect in a gene, a
chromosome abnormality, or environmental exposure,
causing heart problems to occur more often in
certain families.
Maternal
abuse of alcohol during pregnancy, leading to
fetal alcohol syndrome (FAS), is linked to tetralogy
of Fallot. Mothers who take medications to control
seizures and mothers with phenylketonuria (PKU)
are also more likely to have a baby with tetralogy
of Fallot.
Most
of the time, this heart defect occurs sporadically
(by chance), with no clear reason evident for
its development.
The
amount of oxygen-poor (blue) blood that passes
through the VSD to the left side of the heart
varies. If the right ventricle obstruction is
severe, or if the pressure in the lungs is high,
a large amount of oxygen-poor (blue) blood passes
through the VSD, mixes with the oxygen-rich (red)
blood in the left ventricle, and is pumped to
the body. The more blood that goes through the
VSD, the less blood that goes through the pulmonary
artery to the lungs, and the less oxygen-rich
(red) blood that returns to the right side of
the heart. Soon, nearly all the blood in the left
ventricle is oxygen-poor (blue). This is an emergency
situation, as the body will not have enough oxygen
to meet its needs.
Some
situations, such as crying, increase the pressure
in the lungs temporarily, and increasing blueness
might be noted as a baby with tetralogy of Fallot
cries. In other situations, the pathway from the
right ventricle to the pulmonary artery becomes
tighter, preventing much blood from passing that
way, and allowing oxygen-poor (blue) blood to
flow through the VSD into the left heart circulation.
Both of these situations are nicknamed "TET spells."
Sometimes, steps can be taken to lessen the pressure
or the obstruction, and allow more blood to flow
into the lungs and less through the VSD. These
steps, however, are not always effective.
The
following are the most common symptoms of tetralogy
of Fallot. However, each child may experience
symptoms differently. Symptoms may include:
- Because large amounts
of oxygen-poor (blue) blood can flow to the
body under certain circumstances, one of the
indications of tetralogy of Fallot is blueness
(blue color of the skin, lips, and nail beds)
that occurs with such activity as crying or
feeding, and quickly becomes more obvious.
- Some babies do not
have noticeable cyanosis (blue color of the
skin, lips, and nailbeds), but may instead be
very irritable or lethargic due to a decreasing
amount of oxygen available in the bloodstream.
- Some children become
pale or ashen in color, and may have cool, clammy
skin.
Any
of these can be symptoms of tetralogy of Fallot.
The symptoms of tetralogy of Fallot may resemble
other medical conditions or heart problems. Always
consult your child's physician for a diagnosis.
Your
child's physician may have heard a heart murmur
during a physical examination, and referred your
child to a pediatric cardiologist for a diagnosis.
A heart murmur is simply a noise caused by the
turbulence of blood flowing through the obstruction
from the right ventricle to the pulmonary artery.
Symptoms your child exhibits will also help with
the diagnosis.
A pediatric
cardiologist specializes in the diagnosis and
medical management of congenital heart defects,
as well as heart problems that may develop later
in childhood. The cardiologist will perform a
physical examination, listening to the heart and
lungs, and make other observations that help in
the diagnosis. The location within the chest that
the murmur is heard best, as well as the loudness
and quality of the murmur (harsh, blowing, etc.)
will give the cardiologist an initial idea of
which heart problem your child may have. However,
other tests are needed to help with the diagnosis,
and may include the following:
- chest x-ray -
a diagnostic test which uses invisible electromagnetic
energy beams to produce images of internal tissues,
bones, and organs onto film.
- electrocardiogram
(ECG or EKG) - a test that records
the electrical activity of the heart, shows
abnormal rhythms (arrhythmias or dysrhythmias),
and detects heart muscle stress.
- echocardiogram (echo)
- a procedure that evaluates the
structure and function of the heart by using
sound waves recorded on an electronic sensor
that produce a moving picture of the heart and
heart valves.
- cardiac catheterization
- a cardiac catheterization is an
invasive procedure that gives very detailed
information about the structures inside the
heart. Under sedation, a small, thin, flexible
tube (catheter) is inserted into a blood vessel
in the groin, and guided to the inside of the
heart. Blood pressure and oxygen measurements
are taken in the four chambers of the heart,
as well as the pulmonary artery and aorta. Contrast
dye is also injected to more clearly visualize
the structures inside the heart.
Specific
treatment for tetralogy of Fallot will be determined
by your child's physician based on:
- your child's age, overall
health, and medical history
- extent of the condition
- your child's tolerance
for specific medications, procedures, or therapies
- expectations for the
course of the condition
- your opinion or preference
Tetralogy
of Fallot is treated by surgical repair of the
defects. A team of cardiac surgeons performs the
surgery, usually before an infant is 1 year old.
In many cases, the repair is made at around 6
months of age, or even a little earlier. Repairing
the heart defects will allow oxygen-poor (blue)
blood to travel its normal route through the pulmonary
artery to receive oxygen.
The
operation is performed under general anesthesia,
and involves the following:
- The ventricular septal
defect is closed with a patch.
- The obstructed pathway
between the right ventricle and the pulmonary
artery is opened and enlarged with a patch.
If the pulmonary valve is small, it may be opened
as well.
Children
will spend time in the intensive care unit (ICU)
after tetralogy of Fallot repair. During the first
several hours after surgery, your child will be
very drowsy from the anesthesia that was used
during the operation, and from medications given
to relax him/her and to help with pain. As time
goes by, your child will become more alert.
While
your child is in the ICU, special equipment will
be used to help him/her recover, and may include
the following:
- ventilator -
a machine that helps your child breathe while
he/she is under anesthesia during the operation.
A small, plastic tube is guided into the windpipe
and attached to the ventilator, which breathes
for your child while he/she is too sleepy to
breathe effectively on his/her own. After a
truncus repair, children will benefit from remaining
on the ventilator overnight or even longer so
they can rest.
- intravenous (IV) catheters
- small, plastic tubes inserted
through the skin into blood vessels to provide
IV fluids and important medicines that help
your child recover from the operation.
- arterial line -
a specialized IV placed in the wrist or other
area of the body where a pulse can be felt,
that measures blood pressure continuously during
surgery and while your child is in the ICU.
- nasogastric (NG) tube
- a small, flexible tube that keeps
the stomach drained of acid and gas bubbles
that may build up during surgery.
- urinary catheter -
a small, flexible tube that allows urine to
drain out of the bladder and accurately measures
how much urine the body makes, which helps determine
how well the heart is functioning. After surgery,
the heart will be a little weaker than it was
before, and, therefore, the body may start to
hold onto fluid, causing swelling and puffiness.
Diuretics may be given to help the kidneys to
remove excess fluid from the body.
- chest tube -
a drainage tube may be inserted to keep the
chest free of blood that would otherwise accumulate
after the incision is closed. Bleeding may occur
for several hours, or even a few days after
surgery.
- heart monitor -
a machine that constantly displays a picture
of your child's heart rhythm, and monitors heart
rate, arterial blood pressure, and other values.
Your
child may need other equipment not mentioned here
to provide support while in the ICU, or afterwards.
The hospital staff will explain all of the necessary
equipment to you.
Your
child will be kept as comfortable as possible
with several different medications; some which
relieve pain, and some which relieve anxiety.
The staff will also be asking for your input as
to how best to soothe and comfort your child.
After
discharged from the ICU, your child will recuperate
on another hospital unit for a few days before
going home. You will learn how to care for your
child at home before your child is discharged.
Your child may need to take medications for a
while at home, and these will be explained to
you. The staff will give you instructions regarding
medications, activity limitations, and follow-up
appointments before your child is discharged.
Pain
medications, such as acetaminophen or ibuprofen,
may be recommended to keep your child comfortable
at home. Your child's physician will discuss pain
control before your child is discharged from the
hospital.
After
surgery, older children usually have a fair tolerance
for activity. Your child may become tired easily,
and sleep more right after surgery, but, within
a few weeks, your child should be fully recovered.
Most
children who have had a tetralogy of Fallot surgical
repair will live healthy lives. Activity levels,
appetite, and growth will eventually return to
normal in most children. Your child's cardiologist
may recommend that antibiotics be given to prevent
bacterial endocarditis after discharge from the
hospital.
After
initial repair of tetralogy of Fallot, pulmonary
valve replacement is often indicated in the second
or third decade of life to prevent complications
such as enlargement of the right ventricle, dysrhythmias,
and heart failure. For women wishing to have children,
pre-conception evaluation by echocardiogram and/or
magnetic resonance imaging (MRI) is recommended.
Consult
your child's physicians regarding the specific
outlook for your child.
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