- The heart is made up of four
chambers: the right and left atria, and the right and left
ventricles. Here is a simplified description of how the
normal flow of blood works. Blood from the venous system of
the body is returned to the right atrium, which acts like a
reservoir and pumps it into the right ventricle. The right
ventricle, in turn, pumps blood through the lungs so it can
be oxygenated and have carbon dioxide removed. Blood from
the lungs empties into the left atrium, where it is pumped
into the left ventricle. The left ventricle then pumps blood
to the body.
- Even though the right and left atria
are attached by a septum, they should not exchange blood.
When a defect (a hole) occurs in the septum between them, it
is known as an atrial septal defect. In this case, some of
the blood from the left atrium gets pumped into the right
atrium, instead of the left ventricle. Thus, the heart is
forced to do increased work by pumping blood back through
the right atrium, right ventricle, and lungs -- even though
the blood has already been oxygenated.
- There are three areas of the atrial
septum where the defect may occur. The most common (80%)
occur in the mid septum (medically called the ostium
secundum). The other two areas occur in the lower septum
(ostium primum) and the upper septum (sinus venosus defect).
(Note: this section discusses the disease in adults only;
for infants and children, see the pediatric
- Small or moderate -- sized defects
usually have no symptoms.
- Large defects -- shortness of breath on
exertion -- usually occur in an individual in his/her
- Congenital -- the patient is born with the defect.
- Heart -- systolic ejection murmur is heard at the
parasternal borders of the 2nd and 3rd intercostal spaces;
the S2 is widely split and remains fixed with
(EKG) -- right axis deviation or right
ventricular hypertrophy may be present. The hypertrophy is caused
by volume overload.
- Chest X-Ray shows increased
pulmonary vascularity, large pulmonary arteries, and
enlarged right atrium and right ventricle (the aortic knob
will be small).
- Standard Echocardiogram will
show enlarged right atrium and right ventricle.
- Echocardiography with saline
bubble contrast and doppler flows can demonstrate the
- Transesophageal echo (special echo
in which a camera is passed down the esophagus to get a
better view of the heart) is sometimes necessary.
- Cardiac catheterization (a catheter
is passed through the groin, and dye is injected to
get a good view of the heart and vessels) can make a definite
diagnosis by allowing a sampling of blood from the
vena cava and the right ventricle -- normally their
oxygen levels should be identical, but with an atrial
septal defect the oxygen level will be higher in the blood
sampled from the right ventricle.
- MRI of the heart is sometimes
- A radionuclide flow study can quantify (tell us how
much blood) is being passed through the
- Small shunts -- no treatment
- Large shunts -- these cause significant heart damage (right atrium and right ventricle enlarge due to the increased workload). Also pulmonary Hypertension (high
blood pressure in the blood vessels of the lungs) occurs.
Additionally, heart arrythmias (irregularities) may occur.
- Treatment techniques include
deployment of an umbrella device that is passed from a
catheter into the heart. It is then "opened up" in the
defect and closes it off.
- Open surgical repair may also be
formed (a patch is sewn over the
- Paradoxical emboli -- patients who develop blood clots in their legs might release them, after which the clots normally go to the lungs (not a good development). In patients with an atrial septal defect, the blood clots may go from the right atrium into the left atrium, and thus bypass the lungs, but unfortunately, such clots can go directly to vital organs, such as the brain (causing a Stroke) or kidneys (causing
- Atrial septal defect in infants and children -- see pediatric section.
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