Primum atrial septal defect
A primum atrial septal defect is a hole between the two upper chambers (atria) of the heart. The size of the hole can range anywhere from small to large, although they are most often large. Nearly all children with this type of defect also have a gap (cleft) in the mitral valve and as a result some degree of leaking at this valve (mitral regurgitation) is almost the rule.
What causes it?
Children are born with this type of defect, but it may not be identified until toddler age or even later depending on how much of a noise (murmur) the defect causes. There is no exposure or activity during pregnancy that we know of that can cause this to occur. Children with Down’s syndrome are much more likely to have this condition. Children of parents with this condition have a 9-14% risk of having congenital heart disease themselves.
What problems can it cause?
Physiologically a primum atrial septal defect behaves much as any other large atrial septal defect(ASD). Pink oxygen-rich blood returning from the lungs crosses the hole and it pumped back to the lungs. The result is some wasted work for the heart, and some enlargement of the right-sided heart chambers (right atrium and right ventricle) because of the increased amount of blood flowing through them. Over many years this can result in very gradual injury to the heart or the lungs, so it is generally recommended that a primum ASD should be repaired electively between 3 and 5 years of age.
In some children the cleft in the mitral valve can result in a significant amount of leaking (mitral regurgitation). In this situation, surgery may need to be scheduled earlier, either because the leaking is causing more work than the heart can handle (congestive heart failure), or because long-term leaking may damage the valve enough to make repair more difficult.
Some children with large ASDs have problems with growth, and in such cases weight is generally more greatly affected than height. Following surgical repair, children who are small-for-age often do grow better than they did prior to surgery. Although it has never been studied whether the timing of surgery plays an important role in the degree of catch up growth following repair, in the case of children who are having problems with growth it may make sense to consider earlier repair.
How is it treated?
Occasionally it is helpful for a child with an atrial septal defect primum to take medications to help with shortness of breath, but most children have no symptoms and require no medications. The only effective treatment is surgical repair. The surgery entails an incision along the breastbone (sternum) and closure of the atrial defect with a patch, often made of the child’s own tissue (pericardium). In many cases the surgeon will also repair the cleft in the mitral valve at the same time if there is any significant leaking. Although this operation is an open-heart surgery, it is usually fairly straightforward and should involve minimal risk when performed by a skilled surgeon in a center specializing in pediatric heart surgery.
What happens after surgery?
Following surgery it is necessary to have ongoing cardiology follow-up, but given a good repair it is quite likely that one will have normal exercise tolerance and life expectancy. Girls who have had heart surgery should be able to have normal pregnancies, but will need to have a cardiologist following them during pregnancy. Generally, everyone who has had surgical repair of a primum atrial septal defect will require endocarditis prophylaxis for at least 6 months after surgery.
If you have more questions about ASDs, please don't feel uncomfortable asking your pediatric cardiologist.
For more information about ASDs in the Internet, try some of the web links below. I cannot vouch for the contents, but with the Internet it's always a case of "browser beware".
Boston Children's Hospital
Overview of atrial septal defects
Royal Children's Hospital in Melbourne
A very clinical discussion intended for physicians, but with a lot of useful detail if that is what's needed.