by Kimberly Allen RN
An atrial septal defect (ASD) is an opening or hole in the wall between the two upper chambers of the heart known as atria. It is the most commonly diagnosed congenital heart defect that presents in adults. ASD’s account for 30-40% of all congenital heart conditions that are seen in adults.
ASD is one of a number of congenital heart defects that can be present at birth. Drs know that these defects occur because of an error that occurs early in the hearts development, however why the error occurs is rarely clear. Drs believe that both genetics as well as environmental factors have an impact on the hearts development.
The heart is made of four chambers, two upper chambers called atria and two lower chambers called ventricles. There is one atria and one ventricle on the right and one atria and ventricle on the left. The chambers on the left side of the heart receive oxygenated blood from the lungs and pumps it out into the body. The chambers on the right side of the heart receive the blood that no longer has the oxygen because it has been distributed through out the body on its way back to the heart and pumps it to the lungs to receive a fresh supply of oxygen. When there is an opening in the wall between two chambers of the heart like the atria the fresh oxygenated blood is able to leak into the chamber with the deoxygenated blood. Even though the blood from the left is already oxygenated because it is now mixed with the deoxygenated blood it goes to the lungs even though it already has oxygen. The increased volume of blood going to the lungs can increase the pressure in the lungs and increase the workload of the heart.
Most ASD’s are small with minimal effects. However, the main reason they are usually diagnosed in adulthood is because as you age and the blood has been going through the hole the hole gets bigger causing more damage and more symptoms. There are several different types of ASD’s, the three most common of which account for 10% of all congenital heart disorders and up to 40% of the congenital heart defects seen in adults. The three most commonly diagnosed ASD’s are:
1. Ostium secundum is the most commonly diagnosed ASD with 75% of all diagnosed cases of ASD being this type. During fetal development an opening in the fetal heart known as the foramen ovale allows the blood to circulate through the heart without going to the lungs. The blood moves directly from the right atrium to the left atrium. In this type of ASD the flap of tissue that covers the foramen ovale after birth does not properly adhere to the wall or septum between the two atria.
2. Ostium primum is the second most commonly diagnosed type of ASD accounting for 15-20% of all ASD’s. This type of ASD is an atrioventricular septal defect, which occurs during fetal heart development. When the wall or septum that divides the atria grows it grows downward toward the ventricles eventually meeting the septum between the ventricles and fusing. In this type of ASD the fusion is incomplete. This type also frequently involves the valves between the atria and the ventricles.
3. Sinus venosus is seen in approximately 5-10% of all ASD’s. In this type of Asd there is a defect in the upper right atria near where the large vein retuning the deoxygenated blood to the heart enters the atria. It is frequently associated with abnormal drainage of the right pulmonary vein.
Many ASD’s are small and close throughout infancy however there are those with lager defects that can lead to complications if left untreated including right sided heart failure and abnormalities in the heart rhythm. there is also an increase risk of stroke and a shorter life expectancy.
The type of treatment depends on many factors, the severity of the defect and the age and overall health of the patient. A young child or infant probably won’t be treated in the same manor as an adult. Frequently the Dr will want to monitor the defect especially in infants and young children to see if it will close on it’s own. If the ASD is persistent eventually it may require surgical repair. Today most ASD’s are repaired through a type of surgery known as cardiac catheterization instead of open heart surgery. Your Dr will discuss the options available along with the potential complications and outcomes of each.