Atrial Septal Defect (ASD) is a hole in the heart, specifically in the wall separating the left and right atria. There are 3 main types of ASD, the most commonly seen is called a Patent Foramen Ovale and can exist in adults with no symptoms. ASDs are the 4th most common congenital defect. A more serious defect (Ostium secundumcum) where the septum has failed to grow properly in the foetus, leads to blood shunting from the left side of the heart (high pressure) to the right side (low pressure).
This can lead to volume overload, high blood pressure in the lungs and arrhythmias. There is a known link between ASDs' and strokes. In recent years there have also been a number of studies carried out which show that there may also be a link to migraine. Clinical findings normally show up in the 2nd, 3rd decade of life. Closures of ASDs are more commonly carried out in childhood or at the time of the diagnosis later in life. Patients need to have a full echo study to assess their cardiac status and to measure the ASD in multiple views.
Surgical closure is very effective but carries higher risks of morbidity and other complications related to surgery as well as increased hospital stays. Closure can also be performed transluminally using a catheter device called a Septal Occluder. The device is a self expanding double disc made of a nickel and titanium wire mesh and looks a bit like an umbrella.
The device is delivered into the heart through a long introducer sheath which is positioned across the ASD. The septal occluder(or umbrella) is positioned on one side of the septum and one of the discs is opened out, the catheter is then pulled back across the ASD to stent the defect.
The 2nd disc is then opened out and deployed on the other side of the septum. During the procedure a Trans Oesophageal Echo probe is positioned in the Oesophagus just behind the heart providing the cardiologist with a good view of the septum and the device as it is deployed. If a good position is confirmed then the device is released from the delivery system and the delivery system and sheath are removed. A whole range of sizes are required for the procedure as sizing the defect occurs at the time of the cardiac cath using a low pressure dilation balloon.