1. ASD is a Common Congenital Heart Defect
An atrial septal defect (ASD) is a persistent communication between the upper chambers of the heart. It is present in about one to two percent of the population. The defect results when tissue fails to form correctly between the atria. An ASD can be found in a variety of locations in the upper chamber including the central portion ("ostium secundum" type), around the vena cava ("sinus venosis" type) and near the valves ("ostium primum" type).
2. Patients are Often Asymptomatic
Many people live their entire lives with a small ASD and never have any symptoms. A large ASD can result in significant symptoms even at an early age. The persistent flow from left to right causes overload of the right heart. In the young this can result in poor feeding and difficult breathing. In adults the right heart continues to grow and the lungs are often affected. This results in breathing difficulty, palpitations and, at times, stoke.
3. Stoke and Atrial Fibrillation are Common
Stroke in ASD patients is a common occurrence. Flow across an ASD is left to right, but blood can easily move right to left with a cough or valsalva maneuver (straining with a bowel movement or heavy lifting). A PFO (patent foramen ovale) is a type of ASD. There is a clear cut association with stroke and PFO in patients under 60 but there is still no indication to repair a PFO after a first stroke in this population (although studies are underway). Atrial fibrillation is also very common as the defect affects the upper heart chamber and causes dilation of the chamber and subsequent electrical instability.
4. Severe Pulmonary Hypertension Complicates Repair
An ASD that goes untreated for decades will often result in enlargement of the right heart chambers and elevated lung pressures (pulmonary hypertension). When the lung pressures are chronically elevated the damage can be irreversible. As the pressure builds up it can reverse the flow across the ASD. If an ASD is repaired in this situation this consequences can be life threatening as the pressure in the lungs will transmit to the right heart and cause immediate failure of the pump.
5. ASD Can be Repaired Percutaneously and Surgically
Repair of an ASD can be performed or by open heart surgery. Secundum type defects can usually be fixed percutaneously with a double clam-shell umbrella type device, if appropriate tissue rims are present. The devices approved for ASD repair are the Amplatzer septal occluder and the Gore Helix Occluder. The mode of treatment depends on the size of the defect and the tissue rims present. If more than two tissue rims are missing a device may not stay in place. Open surgical repair of an ASD was one of the first successful open heart procedures. When necessary it is very durable. The key to ASD repair is performing the repair before lung pressures become severely elevated.
