Truncus
Arteriosus
Truncus
arteriosus is a congenital (present at birth)
defect that occurs due to abnormal development
of the fetal heart during the first 8 weeks of
pregnancy. The heart begins as a hollow tube,
and the chambers, valves, and great arteries develop
throughout the first 8 weeks of pregnancy. The
aorta and pulmonary artery start as a single blood
vessel, which eventually divides and becomes two
separate arteries. Truncus arteriosus occurs when
the single great vessel fails to separate completely,
leaving a connection between the aorta and pulmonary
artery.
Truncus
arteriosis is a complex defect where there is
a single (normally there are two separate arteries)
vessel arising from the heart that forms the aorta
and pulmonary artery. Another congenital heart
defect that occurs with truncus arteriosus is
a ventricular septal defect (ventricular septum,
or dividing wall between the two lower chambers
of the heart known as the right and left ventricles).
Normally,
there are two separate arteries (the aorta and
the pulmonary artery. 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 truncus
arteriosus, oxygen-poor (blue) and oxygen-rich
(red) blood mix back and forth through the ventricular
septal defect. This mixed blood then flows through
the common truncal vessel. Some of it will flow
through the branch that becomes the pulmonary
artery and on to the lungs, and some of the mixed
blood will go into the aortic branch and continue
to the body. The mixed blood that goes to the
body does not have as much oxygen as normal, and
will cause varying degrees of cyanosis (blue color
of the skin, lips, and nailbeds).
Truncus
arteriosus occurs in less than one out of every
10,000 live births. It makes up 1 percent of all
cases of congenital heart disease.
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. Other times this heart defect
occurs sporadically (by chance), with no clear
reason for its development.
The
blood that passes through the common truncal vessel
has a lower oxygen content than normal. Oxygen-poor
(blue) blood from the right ventricle and oxygen-rich
(red) blood from the left ventricle mix together
before entering the common vessel. Some of this
mixed blood will go into the aorta and on to the
body, producing cyanosis (blue color of the skin,
lips, and nailbeds).
The
pulmonary artery section of the common vessel
gets more blood flow than the aorta does, because
the pressure is lower in the lungs than the body
and it is easier for blood to travel in that direction.
If not repaired, the blood vessels in the lungs
become damaged by the extra blood flow. As the
pressure in the blood vessels in the lungs becomes
higher, less blood goes to the lungs and more
goes to the body. Cyanosis becomes worse as blood
with lower amounts of oxygen travels to the body.
The
following are the most common symptoms of truncus
arteriosus. However, each child may experience
symptoms differently. Symptoms may include:
- cyanosis
- fatigue
- sweating
- pale skin
- cool skin
- rapid breathing
- heavy breathing
- rapid heart rate
- congested breathing
- disinterest in feeding,
or tiring while feeding
- poor weight gain
The
symptoms of truncus arteriosus 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 heart
defects. 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 truncus arteriosus 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
Truncus
arteriosus must be treated by surgical repair
of the defects. However, medical support may be
necessary until the best time for the operation
to take place. Treatment may include:
- medical management
Many children will eventually need to take medications
to help the heart and lungs work better. Medication
that may be prescribed includes the following:
- digoxin -
a medication that helps strengthen the heart
muscle, enabling it to pump more efficiently.
- diuretics -
the body's water balance can be affected
when the heart is not working as well as
it could. These medications help the kidneys
remove excess fluid from the body.
- ACE (angiotensin-converting
enzyme) inhibitors - dilates
the blood vessels, making it easier for
the heart to pump blood forward into the
body.
- adequate nutrition
Infants may become tired when feeding, and may
not be able to eat enough calories to gain weight.
Options that can be used to ensure your baby
will have adequate nutrition include:
- high-calorie formula
or breast milk
Special nutritional supplements may be added
to formula or pumped breast milk that increase
the number of calories in each ounce, thereby
allowing your baby to drink less and still
consume enough calories to grow.
- supplemental tube
feedings
Feedings given through a small, flexible
tube that passes through the nose, down
the esophagus, and into the stomach, can
either supplement or take the place of bottle
feedings. Infants who can drink part of
their bottle, but not all, may be fed the
remainder through the feeding tube. Infants
who are too tired to bottle feed may receive
their formula or breast milk through the
feeding tube alone.
- surgical repair
Surgery is usually performed after the infant
is 2 weeks old, but before the blood vessels
in the lungs are overwhelmed by extra blood
flow and become diseased.
The operation is performed under general anesthesia,
and involves the following:
- The pulmonary arteries
are detached from the common artery (truncus
arteriosus) and connected to the right ventricle
using a homograft (a section of pulmonary
artery with its valves intact from a tissue
donor).
- The ventricular
septal defect is closed with a patch.
Children
will spend time in the intensive care unit (ICU)
after a truncus repair.
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.
Often,
infants who fed poorly prior to surgery have more
energy after the recuperation period, and begin
to eat better and gain weight faster. However,
high-calorie formulas may be needed for several
weeks or months after surgery to help your child
catch up growth-wise. Tube feedings may also be
helpful until your child is able to feed better.
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.
You
may receive additional instructions from your
child's physicians and the hospital staff.
Many
children who have had truncus arteriosus surgical
repair can live healthy lives. Activity levels,
appetite, and growth will eventually return to
normal in most children.
Future
intervention may be necessary if the pulmonary
artery branches were small and do not grow well
after surgery. The homograft connecting the right
ventricle to the pulmonary artery may also need
to be replaced in the future as your child grows.
Your
child's cardiologist may recommend that antibiotics
be given to prevent bacterial endocarditis after
discharge from the hospital.
Regular
follow-up care at a center offering pediatric
or adult congenital cardiac care should continue
throughout the individual’s lifespan.
Consult
your child's physician regarding the specific
outlook for your child.
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