Atrial Septal Defects are one of the most common types of heart defects. An atrial septal defect is a hole in the wall of the heart that separates the right atrium and the left atrium. The septum is the wall or barrier that separates the two upper chambers of the heart called the atriums that are the receiving chambers of the heart. The lower chambers are the ventricles and these are the pumping chambers. What the atriums receive is blood.
There are 3 kinds of atrial septal defects (ASD). The reason there are three kinds of atrial septate defects is due to where they are located on the wall called the septum.

1.The first atrial septal defect we will talk about is called:
Ostium Secundum Atrial Septal Defect, (OSASD). An Ostium secundum ASD is the most common of the three types of ASD. It happens in the middle of the septum between the right and left atrium. If you remember that while a baby is still in the womb the foramen ovale (an opening) allows blood to go from one atrium to the other and when the baby is born the foramen ovale usually closes itself or seals it self off.
Another type of this ASD is called a patent (means opening) foramen ovale (PFO) and this hole is very small.

2. The second type of Atrial Septal Defect (ASD) is called Ostium Primum and this is the next most common type of ASD. The hole is located in the lower part of the atrial septum. With this kind of ASD it is quite common that the mitral valve is also affected and this is called a mitral valve cleft. A mitral valve cleft is a hole in one of the leaflets that form the mitral valve.

3. The third type of Atrial Septal Defect (ASD) we will talk about is called Sinus Venosus Atrial Septal Defect. A Sinus venosus defect is the least common type of Atrial Septal Defect. The hole is found in the upper part of the atrial septum. If one has this type ASD it is common to also have an abnormal pulmonary vein connection seen with it. There are 4 pulmonary veins. Two veins from the right lung and two veins from the left lung usually return red oxygenated blood to the left atrium. With a Sinus venosus defect a pulmonary vein from the right lung will be abnormally connected to the right atrium instead of where it is suppose to connect to the left atrium. This is called an anomalous pulmonary vein.

This is just a brief summary of what the different kinds of Atrial Septal Defects there are.

Many kinds of Atrial Septal Defects (ASD) can happen as one single heart defect or it can happen with many other heart defects such as Ventricular Septal Defect (VSD), Patent Ductus Arteriosis (PDA), Coarctation of the Aorta (CoA) and others. It is very common for babies to grow up before they need care, have symptoms or are diagnosed with an Atrial Septal Defect (ASD).

There are two sides to the heart and they are separate from each other. The two sides or parts are called the right side and the left side. The right side and the left side are normally completely separate from each other. If there is a hole, an opening or a tiny slit between the right and left side of the heart in the upper chamber called the atrium there is no longer a separation between the two sides.

Now there is a connection between the two sides. The hole in one side of the heart now allows blood to flow to the other side. Remember that the atriums are the holding or receiving chambers of the heart and the blood in the upper chambers are under pressure sort of like filling a balloon with water. The left atrium is under higher pressure than the right atrium. This means that blood rich with oxygen and red in color will be shunted through the atrial septal defect from the left atrium of the heart that is a high pressure zone to the right atrium of the heart that is low pressure zone and this can cause many problems such as:

1. Enlargement of both the upper chamber of the heart on one side called the right atrium and enlargement of the lower chamber of the heart called the right ventricle. Remember the right upper chamber passes blood down to the right lower chamber the right ventricle. With the increase in the amount of blood volume to the right side of the heart that is caused by the left to right shunting of the blood through the hole in atrial septal defect will cause the right side of the heart chambers the right atrium and right ventricle to get bigger and enlarge overtime because of the unequal pressure of blood flow.
2. Remember there is a valve between the right atrium and the right ventricle called the tricuspid valve to allow blood to continue to flow. If both the right atrium and right ventricle enlarge this valve called the tricuspid valve will stretch apart too much and will not close back properly. If the valve stretches and does not close normally this will allow the blood to flow backwards called (regurgitation) into the right atrium instead of continuing to flow forward.
3. Too much blood flow or an increase in blood flow to the right side of the heart can cause an increase in pressure to the lungs and cause pulmonary hypertension. With the increase in pressure in the lungs over time this can cause and irreversible change in the pulmonary blood vessels called pulmonary vascular disease and can become a very serious complication of an atrial septal defect.
4. The heart has a specific pace or rhythm that it tries to keep when it is not being exercised. Each heart beat starts within a type of pacemaker that is a grouping of special cells in the right atrium. This special type of pacemaker is called the sinus node or sinus atrial node. The sinus atrial node (SAN) generates an electrical impulse that travels around the heart and causes a heart beat. When the right atrium enlarges this will irritate the sinus node and interrupt the regularity of the heart beat that results in atrial arrythmias. A specific type of atrial arrhythmia called atrial fibrillation is often associated with an atrial septal defect.
5. Blood in the heart normally flows from the right sided chambers to the lungs and then to the left sided chambers then out to the rest of the body. Should a blood clot or air bubble enter the blood circulation it would normally be filtered out of the blood by the lungs. However, with an atrial septal defect there is a small chance that a blood clot could bypass the lungs and travel directly to the brain resulting in a stroke. Not only that but if an irregular heart rhythm develops the risk of a blood clot forming in the right atrium is increased and the risk of a stroke is increased.

What can be done to treat this?
The treatment of the heart defect called an atrial septal defect (ASD) depends on many things such as the location of the hole, how big the hole is, and the symptoms that are present and the effect the heart defect is having on the heart muscle itself. Operating to close the hole is standard treatment either with a patch or with sutures and this is an invasive technique which means they open the chest and the heart. There are also non-invasive techniques which means they don't have to open the chest or heart. There is the possibility of a non- surgical method of closing the atrial septal defect using a cathetheter based placement of a tool like an umbrella to occlude or close the hole in the atrial septum. This non-invasive procedure is gaining a large following. If the atrial septal defect is associated with high pulmonary pressures it may not be the right decision to close the defect. It may be better to use medical management of the symptoms by a cardiologist. It is important to realize that early detection, evaluation and treatment of an atrial septal defect be done to prevent serious complications of this heart defect and more serious problems later.