Atrioventricular canal defect (AV Canal), also known as atrioventricular septal defect (AVSD), occurs when structures of the heart do not form correctly.

This abnormal structure leads to several issues: 

  • Ventricular septal defect: The wall between the two bottom pumping chambers (ventricles), or ventricular septum, does not form correctly, leaving a hole, or ventricular septal defect (VSD).
  • Atrial septal defect: There is also a hole between the two top collecting chambers (atria), called an atrial septal defect (ASD).
  • Poorly formed mitral and tricuspid valves that do not close properly and leak blood back into the atria.  

AV Canal – Complete or Partial

AV Canal can be described as complete or partial based on whether or not there is a hole in the ventricle. Children with a complete AV Canal typically have a large hole, while children with a partial AV Canal have a hole only between the top chambers. We call this type of ASD a primum ASD.

Children with a partial AV Canal have two separate valves instead of the common AV valve. The mitral valve usually has a split in it called a cleft.

Symptoms may develop over time and could include:

  • Hard, fast breathing
  • Heart murmur
  • Slow weight gain
  • Trouble feeding

Read our Patient Guidebook on AV Canal

Our Patient Guidebooks provide additional information about the conditions we treat. They are not diagnoses and should never be used instead of medical advice. 

AV Canal – Causes and Diagnosis

AV Canals are common in children with Down syndrome and can occur with other genetic syndromes. However, this heart defect can develop in children with no genetic syndromes. In those cases, we don't know the cause of the abnormal heart structure.

AV Canal is usually diagnosed with an echocardiogram, which is an ultrasound of the heart. Diagnoses can also be made with a fetal echocardiogram before birth. Other AV Canal conditions may not be detected until after birth.

If your baby's AV Canal is related to a chromosome detection (such as Down syndrome) or a genetic syndrome, a genetic counselor can tell you the chances of a future pregnancy that would have the same condition.

Care Providers

The University of Maryland Children's Heart Program team that treats AV Canals includes a pediatric cardiac surgeon, pediatric cardiologists, pediatric and neonatal intensive care doctors and nurses, pediatric cardiac anesthesiologists, cardiac operating room staff, cardiac nurses and many others with expertise in providing this specialized cardiac care. 

Treating AV Canal

All babies with AV Canal will require open heart surgery. The timing of the surgery depends on the symptoms that the baby develops and how the baby responds to medications. Most babies with complete AV Canal will have their surgery by 6 months of age, although some may need it sooner. Patients with partial AV Canals may not have surgery until they are older.

The surgeon will repair the AV Canal 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.

Children with AV Canal 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 an may require future surgery. Around 10 percent of patients will need a repeat surgery on the valve.

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.

Contact Us

  • To learn more about Maternal Fetal Heart medicine, please call 410-328-3865.
  • To make an appointment with a Children's Heart Program physician, please call 410-328-4348.