Septal Defects – definition, diagnosis and treatment
Septal defects are holes in the wall (septum) that divides the left and right sides of the heart, with different categories for different parts of the heart:
- Holes in the wall dividing the heart’s upper two collecting chambers (the atria) are called atrial septal defects (ASD).
- Similarly, holes in the wall dividing the heart’s lower two pumping chambers (the ventricles) are called ventricular septal defects (VSDs).
VSDs and ASDs are two of the most common form of congenital cardiac lesions, and one or more holes may be present in any given patient; the presence of an ASD does not exclude the possibility of a VSD (or vice versa). Where multiple VSDs are present, the condition is called “Swiss cheese VSD”, for obvious reasons.
The left side of the heart receives oxygenated blood from the lungs, which is then pumped around the body through the aorta. The right side of the heart receives de-oxygenated blood from the veins and this is then pumped into the lungs, via the pulmonary artery. Thus, the right and left sides of the heart deal with de-oxygenated and oxygenated blood respectively, and this arrangement ensures a complete division between de-oxygenated and oxygenated blood.
If one or more holes in the walls between the chambers are present, then some degree of “mixing” of oxygenated and de-oxygenated blood will occur. This carries the corollary that blood that is already partially oxygenated will be pumped back into the lungs, and the systemic circulation will receive blood that is not adequately oxygenated. The problems this causes are in proportion to the size and location of the hole(s) in the septal wall.
With any septal defect, there will be a “shunt” – i.e., the side of the heart which is pumping at a higher pressure will force blood through the hole and into the other side. Unless there are other lesions present, the shunt will initially probably be from left to right, because the left side of the heart operates at a higher pressure. This is a dynamic process, and over time the direction of the shunt may well reverse (e.g. right – left, rather than left – right). The wording does repeat – the diseases themselves are morphologically related We could excise this section if you like?
ASDs and VSDs can both be clinically silent, and sufferers may not realise they have the condition.
One type of hole in the atrium is known as a patent foramen ovale. This communication is always present before birth. It usually closes shortly after birth. In a small minority of people, however, the foramen ovale remains open (that is, patent).
The symptoms and effects of septal defects
As above, smaller VSDs and ASDs may not cause symptoms and, if detected, it may suffice simply to monitor the child periodically. Smaller holes can close on their own over time.
With a larger hole (particularly a VSD), a child may breathe harder and faster than usual. That is because blood is being forced across from the left ventricle into the right side of the heart and thereafter into the lungs. Consequently, the lungs are becoming congested by the extra blood flow. If this is not corrected then permanent damage to the lungs may occur.
If there is an aperture between the right and left sides of the heart, it is possible for clots to cross over from the venous circulation and end up in the arterial circulation. From there, they will typically lodge in either the cerebral or possibly the coronary vessels. There is a particular association between (usually undiagnosed) patent foramen ovale and strokes.
Diagnosis and treatment of septal defects
In the case of children suffering from larger VSDs, a heart murmur is often audible on stethoscope.
Assuming the hole is significant enough to be causing symptoms (whether through its size or because it is disturbing the action of the heart valves), the child’s progress is likely to be monitored in the first instance.
If symptoms progress and/or the child’s condition deteriorates, then surgical intervention will be required.
In the first instance, pulmonary artery banding may be offered. As the name suggests, in this procedure a band is placed around the main pulmonary artery. This procedure is designed to limit the volume of blood flowing into the lungs. This is not a permanent solution: the aim is to “hold” the patient until definitive corrective surgery can be offered.
Surgery takes the form of a procedure which involves suturing (stitching a patch over the hole). The patch can be made either from fabric or pericardium. Over time, the heart’s tissue will grow and close over the patch, and the wall will self-seal.
The surgical procedures involved
Historically, patch closure of septal defects could only be offered as an open heart procedure, which is necessarily very invasive. It is now possible to offer patch closure of some defects as a closed procedure in some cases.
The closed procedure involves the insertion of a device on the end of a wire in a cardiac catheterisation lab. The device is inserted into the blood vessels and threaded through until it is in position. Thereafter, it is placed over the defect and sealed into place. The advantage of this technique is that it is minimally invasive.
If open heart surgery is required, it is conducted on cardiopulmonary bypass. As with any cardiac procedure which involves time spent on cardiopulmonary bypass and either the use of aortic cross-clamps or possibly total circulatory arrest, time is of the essence. There is a limited amount of time within which to effect the repair, as the likelihood of damage to the heart and other organs in the body mounts with the passage of time.
If surgery is successful, then the longer term outlook is generally very good, with normal life expectancy and probably normal or near-normal exercise tolerance.