Atrial
Septal Defect (ASD)
An atrial
septal defect is an opening in the atrial septum,
or dividing wall between the two upper chambers
of the heart known as the right and left atria.
ASD is a congenital (present at birth) heart defect.
As the fetus is growing, something occurs to affect
heart development during the first eight weeks
of pregnancy, resulting in an ASD.
Normally,
oxygen-poor (blue) blood returns to the right
atrium from the body, travels to the right ventricle,
then is pumped 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 out to the body
through the aorta.
An atrial
septal defect allows oxygen-rich (red) blood to
pass from the left atrium, through the opening
in the septum, and then mix with oxygen-poor (blue)
blood in the right atrium.
Arial
septal defects occur in 4 percent to 10 percent
of all children born with congenital heart disease.
For unknown reasons, girls have atrial septal
defects twice as often as boys.
The
heart is forming during the first eight weeks
of fetal development. It begins as a hollow tube,
then partitions within the tube develop that eventually
become
the septa (or walls) dividing the right side of
the heart from the left. Atrial septal defects
occur when the partitioning process does not occur
completely, leaving an opening in the atrial septum.
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. Most atrial septal defects occur
sporadically (by chance), with no clear reason
for their development.
There
are three major types of atrial septal defects:
- secundum atrial septal
defect
This is the most common atrial septal defect,
affecting 80 percent of people with this defect.
It is caused when a part of the atrial septum
fails to close completely while the heart is
developing. This causes an opening to develop
between the atria.
- ostium primum atrial
septal defect
This defect is part of the AV canal defects,
and is often found with a split (cleft) in the
leaflet of the mitral valve.
- sinus venosus atrial
septal defect
This defect occurs at the superior vena cava
and right atrium junction. In this defect, one
or more of the pulmonary veins enter the right
atrium instead of correctly entering the left
atrium.
This
heart defect can cause lung problems if not repaired.
When blood passes through the ASD from the left
atrium to the right atrium, a larger volume of
blood than normal must be handled by the right
side of the heart. Extra blood then passes through
the pulmonary artery into the lungs, causing higher
pressure than normal in the blood vessels in the
lungs.
A small
opening in the atrial septum allows a small amount
of blood to pass through from the left atrium
to the right atrium. A large opening allows more
blood to pass through and mix with the normal
blood flow in the right heart. Extra blood causes
higher pressure in the blood vessels in the lungs.
The larger the volume of blood that goes to the
lungs, the higher the pressure in the lungs.
The
lungs are able to cope with this extra pressure
for a while, depending on how high the pressure
is. After a while, however, the blood vessels
in the lungs become diseased by the extra pressure.
Many
children have no symptoms and seem healthy. However,
if the ASD is large, permitting a large amount
of blood to pass through to the right side of
the heart, the right atrium, right ventricle,
and lungs will become overworked, and symptoms
may be noted. The following are the most common
symptoms of atrial septal defect. However, each
child may experience symptoms differently. Symptoms
may include:
- child tires easily
when playing
- fatigue
- sweating
- rapid breathing
- shortness of breath
- poor growth
The
symptoms of an atrial septal defect 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 opening
from the left side of the heart to the right.
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. With an ASD, the
heart may be enlarged because the right atrium
and ventricle have to handle larger amounts
of blood flow than normal. Also, there may be
changes that take place in the lungs due to
extra blood flow that can be seen on an x-ray.
- 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. An echo
can show the pattern of blood flow through the
septal opening, and determine how large the
opening is, as well as how much blood is passing
through it.
- 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. Although an echocardiogram often
provides enough diagnostic information, device
closure of the ASD can be performed at the time
of the catheterization.
Specific
treatment for ASD will be determined by your child's
physician based on:
- your child's age, overall
health, and medical history
- extent of the disease
- your child's tolerance
for specific medications, procedures, or therapies
- expectations for the
course of the disease
- your opinion or preference
Secundum
atrial septal defects may close spontaneously
as a child grows. Once an atrial septal defect
is diagnosed, your child's cardiologist will evaluate
your child periodically to see whether it is closing
on its own. Usually, an ASD will be repaired if
it has not closed on its own by the time your
child starts school - to prevent lung problems
that will develop from long-time exposure to extra
blood flow. The decision to close the ASD may
also depend on the size of the defect. Individuals
who have their atrial septal defects repaired
in childhood can prevent problems later in life.
- medical management
Many children have no symptoms, and require
no medications. However, some children may need
to take medications to help the heart work better,
since the right side is under strain from the
extra blood passing through the ASD. Medications
that may be prescribed include 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.
- infection control
Children with certain heart defects are at risk
for developing an infection of the inner surfaces
of the heart known as bacterial endocarditis.
A common procedure that puts your child at risk
for this infection is a routine dental check-up
and teeth cleaning. Other procedures may also
increase the risk of the heart infection occurring.
However, bacterial endocarditis can often be
prevented by giving children with heart defects
an antibiotic by mouth before the procedure.
It is important that you inform all medical
personnel that your child has an ASD so they
may determine if the antibiotics are necessary
before a procedure.
- surgical repair
Your child's ASD may be repaired surgically
in the operating room. The surgical repair is
performed under general anesthesia. The defect
may be closed with stitches or a special patch.
- device closure
Device closure is frequently performed for secundum
ASD, depending on the size of the defect and
the weight of the child. During the cardiac
catheterization procedure, the child is sedated
and a small, thin, flexible tube (catheter)
is inserted into a blood vessel in the groin
and guided to the inside of the heart. Once
the catheter is in the heart, the cardiologist
will pass a special device, called a septal
occluder, into the open ASD, preventing blood
from flowing through it.
Post-procedure
care for your child:
- device closure procedure
When the procedure is complete, the catheter(s)
will be withdrawn. Several gauze pads and a
large piece of medical tape will be placed on
the site where the catheter was inserted to
prevent bleeding. In some cases, a small, flat
weight or sandbag may be used to help keep pressure
on the catheterization site and decrease the
chance of bleeding. If blood vessels in the
leg were used, your child will be told to keep
the leg straight for a few hours after the procedure
to minimize the chance of bleeding at the catheterization
site.
Your child will be taken to a unit in the hospital
where he/she will be monitored by nursing staff
for several hours after the test. The length
of time it takes for your child to wake up after
the procedure will depend on the type of medicine
given to your child for relaxation prior to
the test, and also on your child's reaction
to the medication.
After the procedure, your child's nurse will
monitor the pulses and skin temperature in the
leg or arm that was used for the procedure.
Your child may be able to go home after a specified
period of time, providing he/she does not need
further treatment or monitoring. You will receive
written instructions regarding care of the catheterization
site, bathing, activity restrictions, and any
new medications your child may need to take
at home.
- surgical repair
In most cases, children will spend time in the
intensive care unit (ICU) for several hours,
or overnight, after an ASD repair. During the
first several hours after surgery, your child
will most likely be 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. Many children have the ventilator
tube removed right after surgery, but some
other children will benefit from remaining
on the ventilator for a few hours afterwards
so they can rest.
- intravenous (IV)
catheters - small, plastic tubes inserted
through the skin into blood vessels to provide
IV fluids and important medications 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 fluids 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 may also ask for your input as to how best
to soothe and comfort your child.
After
discharge 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 and these will be explained to you. The
staff will provide instructions regarding medications,
activity limitations, and follow-up appointments
before your child is discharged.
Most
children feel fairly comfortable when they go
home, and have a fair tolerance for activity.
Your child may become tired quicker than before
the repair, but usually will be allowed to play
with supervision, while avoiding blows to the
chest that might cause injury to the incision
or breastbone. Within a few weeks, your child
should be fully recovered and able to participate
in normal activity.
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.
The
majority of children who have had an atrial septal
defect repair will live healthy lives. Your child's
cardiologist may recommend that your child take
antibiotics to prevent bacterial endocarditis
for a specific time period after discharge from
the hospital.
Outcomes
also depend on the type of ASD, as well as how
early in life the ASD was diagnosed and whether
or not it was repaired. With early diagnosis and
repair of an ASD, the outcome is generally excellent,
and minimal follow-up is necessary. When an ASD
is diagnosed later in life, if complications occur
after surgical closure, or the ASD is never repaired,
the outlook is generally poor. There is a risk
for developing pulmonary hypertension (high blood
pressure in the blood vessels of the lungs) or
Eisenmenger's syndrome. These individuals should
receive follow-up care at a center that specializes
in congenital heart disease.
Consult
your child's physician regarding the specific
outlook for your child.
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