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What is Atrioventricular Canal Defect (AVCD)?

Atrioventricular canal defect (AVCD), also known as atrioventricular septal defect, is a heart defect in the part of the heart that connects the atria to the ventricles. AVCD varies in severity from complete (which taxes the heart almost immediately and results in severe symptoms) to partial (which can be mild enough that some people only discover that they have the defect in their 20’s or 30’s). In AVCD there is a hole in the tissue that separates the left and right sides of the heart, and this hole is right in the center of the heart where the atria and ventricles meet. Because of this hole, the blood from both sides of the heart mixes, too much blood circulates through the lungs on its way to the body, and blood also leaks backwards into the atria. All of this of this puts enormous strain on the heart and can cause serious complications if untreated.

However, if treated early, the prognosis for even severe AVCD is promising. AVCD is relatively rare, happening in about 1 out of every 5,000 live births. Babies with Down’s Syndrome have a higher likelihood of AVCD—approximately 45% of children with Down’s Syndrome have some form of congenital heart disease, and about 25% of these have some type of atrioventricular canal defect. In a similar correlation, about 1/3 of children with AVCDs have Down’s syndrome.

How is AVCD diagnosed during pregnancy?

If your doctor suspects AVCD after reviewing your routine ultrasound, he or she may request a fetal echocardiogram, or an ultrasound of the fetus’s heart. This safe, noninvasive test shows the structure of the heart and how it is functioning, which can help us confirm the diagnosis and decide on the best option for treatment.

How does AVCD affect delivery?

Most babies with AVCD can be delivered vaginally, unless there are obstetric indications for another mode of delivery. It is best for these babies to be delivered at a medical center where there is immediate access to a team of pediatric cardiologists and neonatologists, along with an established NICU (Neonatal Intensive Care Unit).

After delivery, the baby needs PGE, a special medicine that gives a blood vessel the ability to remain patent, or open, after birth. The Fetal Heart Program at the St. Louis Fetal Care Institute has the experience, facilities and technology to handle the most medically challenging deliveries.

In the most severe cases the team can perform cesarean sections and EXIT procedures at SSM Cardinal Glennon Children’s Medical Center. The EXIT procedure allows the fetal and cardiothoracic surgeons to perform life-saving procedures on the baby before cutting the umbilical cord. If additional intervention is needed, the baby is next door to the pediatric operating room and the pediatric hybrid cardiac catheterization suite.

How is AVCD monitored and treated during pregnancy, and what is the surgery after birth?

Depending of the severity of the AVCD, the treatment can vary. Our team at FCI will work with you to determine the best timing and the best type of surgery. Typically, our surgeons perform surgery to close the defect by using a patch made either from the heart’s membrane or from synthetic material. Over time, the heart’s tissue grows over it. For partial defects, the surgeon often either repairs or replaces the heart’s mitral valve. For complete AVCDs, the surgeon separates the single valve into two, one on each side of the patch, or may need to replace the valve.

What happens after the surgeries, and what is the long-term prognosis?

Overall, if treated early, the long-term prognosis for AVCD is quite good. Your child will need regular follow-up visits with a cardiologist throughout their lives to monitor their progress, but will likely lead relatively normal and healthy lives. Children with AVCD usually need to take antibiotics before minor surgical or dental procedures to protect the heart from bacterial infections. There are possible complications later in life, such as heart valve leaks, that may need additional treatment or even follow-up surgeries.