Atrial Septal Defect

Heart Problems related to Atrial Septal Defects

The right and left sides of the heart are normally separate. When a hole (ASD) is present, a connection between the right and left side of the heart allows blood to pass through it from the higher pressure left side to the lower pressure right side. Oxygen-rich red blood is "shunted" through the ASD from the left atrium to the right atrium. The consequences include the following:

• Right atrial and ventricular enlargement
  The increased blood volume to the right side of the heart caused by the left-to-right shunting of blood through the ASD causes the right heart chambers to enlarge over time.

• Tricuspid regurgitation
  As the right-side chambers enlarge, the valve between the right atrium and ventricle (tricuspid valve) stretches and does not close properly. Some blood leaks backward (regurgitation) into the right atrium instead of flowing forward.

• Pulmonary hypertension
  Over time, increased blood flow to the right side of the heart can transmit increased pressure to the lungs, known as pulmonary hypertension. Increased pressure in the lungs, over time, can cause irreversible changes in the pulmonary blood vessels. An irreversible change is called pulmonary vascular disease and can be a very serious complication of ASD. (See Eisenmenger's syndrome.)

• Rhythm disturbances
  Each heartbeat begins within a grouping of special cells in the right atrium. These cells are called the sinus node. The sinus node generates an electrical impulse that travels around the heart and causes a heartbeat. When the right atrium becomes enlarged this will "irritate" the sinus node and disrupt the regularity of the heartbeat resulting in atrial arrhythmias. A type of atrial arrhythmia called atrial fibrillation is often associated with an ASD.

• Stroke
  Blood normally flows from the heart's right-sided chambers to the lungs and then to the left-sided chambers and out to the body. If a blood clot or air bubble enters the vein, it is normally filtered out of the blood by the lungs. With an ASD, however, there is a small chance the clot could bypass the lungs and travel directly to the brain causing a stroke. Additionally, if an irregular heart rhythm develops, the risk of a blood clot forming in the atria increases and, therefore, the risk for stroke also increases.