Atrioventricular septal defect (AV canal), complete and partial
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An atrioventricular septal defect (AV Canal) is a congenital heart defect. It is also referred to as an atrioventricular septal defect (AVSD) or an endocardial cushion defect.
One area of the heart does not develop correctly, and this leads to several issues:
- The wall between the two bottom pumping chambers (ventricles), or ventricular septum, does not form correctly, leaving a hole, or ventricular septal defect (VSD).
- There is also a hole between the two top collecting chambers (atria), called an atrial septal defect (ASD).
This needs to be corrected by surgery. The long term outlook for AVSD patients is very good and the survival from the surgery is very high.
Children can participate in normal activities, including sports. Patients with AVSD who develop valve problems sometimes need medications, but most patients take no medications.
AV Canal - Complete or Partial?
AVSDs can be described as complete or partial. This refers to whether or not there is a hole in the ventricle. Patients with a complete AVSD typically have a large hole, while patients with a partial AVSD only have a hole between the top chambers. We call this type of ASD a primum ASD.
Patients with a partial AVSD have two separate valves instead of the common AV valve, however the mitral valve usually has a split in it called a cleft.
Symptoms develop over time and could include:
- Hard, fast breathing
- Heart murmur
- Trouble feeding
- Slowing in weight gain
AV Canal Causes and Diagnosis
AVSDs are common in Down syndrome and can occur with other genetic syndromes. However, this heart defect can develop in otherwise normal people. In those cases, we don’t know what causes the heart to form abnormally.
AVSDs are usually diagnosed with an echocardiogram, an ultrasound of the heart. Some may be diagnosed by a fetal echocardiogram before birth, but others may not be detected until after birth.
Treating AV Canal
All babies with AVSDs will require surgery. The timing of the surgery depends on the symptoms that the baby develops and hwot he baby responds to medications. Most babies with complete AVSD will have their surgery by 6 months of age, although some may need it sooner. Patients with partial AVSDs may not have surgery until they are older.
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Surgery is usually done around 3-6 months of age. It is an open heart procedure. The surgeon will repair the AVSD by closing both holes with a patch and dividing the common AV valve into two separate parts. Babies are usually in the hospital for 5 to 10 days after surgery.
The surgery is very effective at closing the holes and dividing the valve into two. However, the valve can never be made 100% normal.
Patients with AVSDs need lifelong follow-up with a cardiologist. The surgeon tries to repair the valves so that they don’t leak, but they still open easily.
Despite the best results, the valve may have leakage (regurgitation) or obstruction (stenosis). A mild amount of leakage or obstruction does not usually cause problems, but if these become more severe, some children need another surgery to repair or replace the valve. Around 10 percent of patients will need a repeat surgery on the valve.
Future Pregnancies After AV Canal Diagnosis
If your baby’s AVSD is related to a chromosome abnormality (like Down syndrome) or a genetic syndrome, a genetic counselor can tell you what the chances are that a future pregnancy would have the same condition.
Studies show that when an AVSD is not associated with a genetic problem, the chance that future children will have any heart defect is about 2.5 percent. In future pregnancies, nuchal translucency ultrasound (at the end of the first trimester), targeted anatomy ultrasound (between 18-20 weeks) and fetal echocardiography are recommended.