Atrial Septal Defect (ASD)
What is ASD?
The ASD or atrial septal defects are holes or defects in the partition
(septum) between the two upper chambers of the heart known as the atrial septum. As a result of this hole, the upper chambers on either side of the heart are connected to each other through the defect which is the communication between the two sides. Blood flows abnormally from the left side of the heart to the right side through the ASD, called the “shunt”. When the shunt or ASD is significantly large, the size of the right-sided chambers becomes bigger. If this is allowed to continue for a very long time certain complications can occur. This includes an increase in pressure in the lungs, failure of the right-sided pumping chamber and abnormal heart beats. These generally occur in patients in their 20’s, but can occur in childhood as well.
Which defects need closure and why?
Defects that are large enough to result in enlargement of the right-sided chambers of the heart need to be closed. Small defects can be watched and many of them may close over time. This is especially true for defects that are seen in young infants and small children.
What are the types of ASD and which defects are suited for closure with a device in the cardiac cath lab?
ASD can occur in different locations in the atrial septum. Defects in the uppermost parts of the septum or partition (Sinus venosus defects) and lowermost parts of the septum (Primum ASD) can only be tackled surgically. Central defects that have adequate margins are the only ones suited for closure in the catheterization lab. Careful echocardiographic assessment is needed before planning closure and all the margins of the defect have to be carefully measured. In selected instances, it may be necessary to perform a trans-esophageal echocardiogram (TEE) to determine suitability for closure with a device.
What are the results of ASD device closure?
In experienced hands and with careful case selection, the success rates are in excess of 95%. In a small minority of cases, especially when the defect is large, the procedure may be unsuccessful and the device may not be deployed altogether. These patients will need surgical closure.
What are the complications?
The following complications can be encountered:
Dislodgement of the device: In spite of all precautions a very small proportion of devices may dislodge in the first few hours after deployment. This often requires emergency open-heart surgery wherein the displaced device is removed and the ASD is closed.
Injury to the heart with bleeding around the heart. This is exceptionally rare with modern devices but has been reported.
Heart block: This can happen if the device is large, particularly in young children.
What are the long-term considerations?
Following a device closure, the patient needs to take aspirin or equivalent medication (Clopidogrel) once daily for the next 6 months until the device is covered with the heart’s natural membrane. During this period a few patients may encounter migraine-like headaches. This eventually subsides over a few months. Late erosion of the device into the adjacent parts of the heart has been described in a tiny proportion of patients (~1: 1000).
Following a device closure, follow-up visits are recommended after 1-3 months and often yearly thereafter. In general, patients do quite well and lead active and healthy lives.
Different Types of ASDs before and after closure