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- A non-hereditary birth defect of unknown cause that is twice as common in girls than boys.
- 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).
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- Small or moderate-sized defects usually have no symptoms.
- Some children may have faint Heart Murmurs.
- Older children may complain of fatigue, or shortness of breath.
- Rarely, irregular heartbeats may be present.
- Large defects -- shortness of breath on exertion-usually occur in an individual in his/her 30s.
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- Congenital -- the patient is born with the defect.
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- 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 breathing.
- Electrocardiogram (EKG) -- right axis deviation or
right ventricular hypertrophy may be present. EKG
may show volume overload of the right ventricle.
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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 defect.
- 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 useful.
- A radionuclide flow study can tell us how much blood is being passed through the defect.
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- 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 defect).
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- 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 kidney damage).
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