Ventricular Septal Defect (VSD)
What is VSD?
Ventricular Septal Defect (VSD) refers to a hole in the partition (septum) between the two main pumping lower chambers of the heart (the right and left ventricle). It is one of the commonest heart defects. As a result of the hole, the lower chambers on either side of the heart are connected to each other through the defect which is the communication between the two. Blood flows abnormally from the left side of the heart to the right side through the VSD, called the “shunt”. When the VSD is significantly large, the size of the left-sided chambers becomes bigger, and the lung pressure is high from the excess flow of blood. This can lead to heart failure, which causes symptoms like difficulty feeding (sucking at the breast followed by resting for a while and sucking again), prolonged feeding times, sweating of the forehead while feeding etc. Repeated infections of the chest can also be a feature. Children with small VSDs do not have symptoms. They are commonly diagnosed when a doctor hears a heart murmur on checking the child for some other reason.
There is considerable variety under the category of the VSD depending on the exact location and size. Usually, small VSDs are generally of little consequence and most children with small VSDs can lead perfectly normal lives. Small defects, where the “shunt” doesn’t change the size of the heart and also doesn’t affect lung pressure needs only lifelong follow-up but no surgery. Larger ones are recommended to be closed, preferably around 3 months of age. VSD is usually closed by open-heart surgery. Some VSDs, especially moderate-sized ones in older children can be closed by catheter techniques (keyhole through blood vessels). If large VSDs are not closed at the right time which is usually before one year of age, certain bad changes happen in the lungs, from the excess flow of blood. Large VSDs result in heart failure, growth retardation and can permanently damage the lung vessels. Once these changes become permanent, the child is unsuitable for surgical treatment. Such children become debilitated for life and also have a short life span compared to children with large VSDs who were operated on at the right time. Therefore, the vast majority of large VSDs need to be closed at a young age, often before the first year of life. When the defect is moderate-sized, the decision to close will differ from patient to patient depending on how the baby’s heart is functioning.
Who can undergo catheter closure of VSD?
In a small proportion of children with VSD, it may be necessary to consider closure in the cardiac catheterization laboratory. These are typically older children beyond 2-3 years old with defects that are not too large or too small. Very large defects typically need surgery and small defects do not need closure. Therefore, catheter closure is typically reserved for moderate size defects that result in enlargement of the heart chambers. Some of these children may complain of fatigue or breathlessness on exertion or may not be growing well. The decision to close a VSD in the cath lab needs to be taken carefully after comparing the potential risk of catheter closure versus the risk of doing nothing.
What is done during catheter closure of VSD?
During the procedure, a tube (also known as introducer sheath) is positioned across the VSD. A device that is made of nitinol is squeezed into this sheath and partially expanded in the ventricle. It is then precisely deployed in the defect under guidance from echocardiographic imaging. Once it is certain that the device is stable, it is released. The procedure typically lasts about an hour. If the procedure goes well, the patient can leave the hospital on the following day and return to normal activity in a few days.
What complications can occur during the procedure?
In expert hands complications are infrequent. However, the following complications are reported
The device may dislodge from the position and may need emergency surgery for retrieval
The device may interfere with adjacent structures (aortic valve or tricuspid valve) and may have to be removed prior to release
The child can develop a heart block because of injury to the conduction system of the heart. This may resolve once the device is removed prior to release. If the block develops after release the device may need to be removed by open-heart surgery
The VSD may not be completely closed and there could be flow around the margins of the defect. Typically these flows come down over a period of time but this needs periodic evaluation.
What are the long-term expectations?
If the procedure is successful, the heart chamber enlargement resolves and normal growth is often restored. The following long term concerns merit regular follow-up visits.
Heart block may develop late after VSD device closure: This is exceptionally rare with current generation devices (< 1%) but does occur and this requires ECG to be obtained on follow up visits
Development of leakage of the aortic valve: The commonest variety of VSD (membranous VSD) is close to the aortic valve. If the device comes in close contact with the aortic valve, it may get injured over time because of repeated contact.
What precautions are needed after the procedure?
There is a need to continue to maintain good care of teeth after the procedure because of the small risk of infection at the device implantation site. This is particularly important if there is some flow across the VSD after the placement of the device. If there is no flow remaining there is still a need to be cautious, especially for the first 6 months after the procedure. It is necessary to mention the fact that VSD closure has been done before visits to the dentist because specific precautions may be required.
Different types of VSDs before and after closure