Atrial Septal Defect (ASD)
Atrial Septal Defect, or ASD, is a congenital anomaly of the heart and most ASD's are not serious and can be easily fixed. During the normal development of a fetus, there is an opening, which persists between the two upper chambers of heart (the atria). Oxygenated blood returning from the mother enters the umbilical cord in utero and then crosses the opening in the heart to reach the left side of the heart. In the fetus, this is how red oxygenated blood is normally pumped through the body. This atrial opening normally closes after birth, and blood is pumped through the lungs and then to the left side of the heart, thus separating off the non-oxygenated and oxygenated blood for life.
Atrial septal defects occur if the tissue (known as the atrial septum) between the two atria does not completely close after birth. The persistent opening can vary in size from miniscule to very large. If this opening continues for a long time or into adulthood, the persistent or extra flow of blood across that opening (called a shunt) can place a strain on the heart. There are 3 types of ASD's: Ostium secundum (the most common), Ostium primum, and Sinus venosus.
The ostium secundum defects make up approximately about 90% of all ASD's. This defect is usually easy to repair and requires simple suturing or the placement of a patch of tissue to completely close the opening. Sinus venosus defects are similar to the ostium secundum defects. However, the opening between the atria (atrial septum) is located in such a way that simple closure would not allow proper drainage of blood into the appropriate sides of the heart. In this type of ASD, a patch is secured which allows both closure of the opening, and proper direction of the red blood to the left heart, as was originally intended. Ostium primum defects are probably the most complicated defect to repair because they are associated with abnormalities of the two adjoining heart valves (the mitral and tricuspid valves). They also have a corresponding defect in the muscle wall between the two lower pumping ventricular chambers (called a ventricular septal defect or VSD). Most patients with an ostium primum defect present in early childhood have signs and symptoms of congestive heart failure. If repaired early before 1 year of age, the results are excellent. The valves can be reconstructed while both the ASD and VSD are closed with a patch.
In the majority of cases, leaving an isolated ASD unrepaired can expose the patient to certain risks. First, by leaving this defect intact it permits an extra amount of the blood flow across the two upper chambers. This adds more blood to the pumping responsibilities of the right heart and can infrequently lead to signs of right heart decompensation or failure. Second, later in life the patients can develop atrial fibrillation (a rapid heart rhythm due to progressive dilation of the right heart chambers). And finally, an opening between the heart chambers raises the risk of a blood clot migrating into the left sided heart circulation and travel to the brain, causing a stroke. This is one of the main reasons that ASD repair is recommended in adults, even without symptoms.
In adults, repair of an ostium secundum or the sinus venosus defect is very safe and effective. Surgery carries a very small risk and in most centers, the operative mortality is less than 1% for repair of an ostium secundum ASD. Most patients will be discharged from the hospital in 4-5 days, and back to normal function in 2 or 3 weeks. These procedures are now being performed in many centers, like ours, in a minimally invasive approach. A small incision beneath the skin crease of the breast and is barely visible in women.
Related link: Pediatric Atrial Septal Defect