What we know

We found out when I was 20 weeks pregnant that our baby boy has a heart defect. I'm now 26 weeks along. During the next couple weeks and several appts, we were given a little more information. We have done some genetic and chromosomal testing, and all the results have come back normal. As of now, we have been told he has Pulmonary Atresia, an atrioventricular septal defect (AVSD) and Heterotaxy Syndrome.

AVSD-

Atrioventricular septal defects (AVSD) are a relatively common family of congenital heart defects.

Also known as atrioventricular canal defects or endocardial cushion defects, they account for about 5 percent of all congenital heart disease.The primary defect is the failure of formation of the part of the heart that arises from an embryonic structure called the endocardial cushions. The endocardial cushions are responsible for separating the central parts of the heart near the tricuspid and mitral valves (AV valves), which separate the atria from the ventricles.

The structures that develop from the endocardial cushions include the lower part of the atrial septum (wall that divides the right atrium from the left atrium) and the ventricular septum (wall that divides the right ventricle from the left ventricle) just below the tricuspid and mitral valves.

The endocardial cushions also complete the separation of the mitral and tricuspid valves by dividing the single valve between the embryonic atria and ventricles. An atrioventricular septal defect may involve failure of formation of any or all of these structures.

PULMONARY ATRESIA-

Pulmonary atresia (PA) is a complicated congenital (present at birth) defect that occurs due to abnormal development of the fetal heart during the first 8 weeks of pregnancy.

The pulmonary valve is found between the right ventricle (RV) and the pulmonary artery. It has three leaflets that function like a one-way door, allowing oxygen depleted blood to flow from the right pumping chamber (RV) out to the lungs to pick up oxygen. This valve closes as the RV relaxes so that blood does not go backwards into the right ventricle

With pulmonary atresia, problems with valve development prevent the leaflets from opening, therefore, blood cannot flow forward from the right ventricle to the lungs. Before birth, while the fetus is developing, this actually is not a threat to life because the placenta provides oxygen for the baby and the lungs are not being used to oxygenate the blood. Blood entering the right side of the fetal heart passes through an opening called the foramen ovale that allows oxygen-rich (red) blood from the placenta to pass through to the left side of the heart and proceed to the body. In some cases, there may be a second opening, this time in the ventricular wall, that allows blood in the right ventricle a way out. This opening is called a ventricular septal defect (VSD). If there is no VSD, the right ventricle receives little blood flow before birth and does not develop fully.

At birth, when the baby is separated from the placenta, the lungs open on the first breath and now must do the work of oxygenating the baby’s blood. However, with no pulmonary valve opening present, blood must find another route to reach the lungs and receive oxygen.

The foramen ovale normally shuts at birth, but may stay open in this situation, allowing oxygen-poor (blue) blood to pass from the right atrium to the left atrium. From there, it goes to the left ventricle, out the aorta, to the body. This situation cannot support life, since oxygen-poor (blue) blood cannot meet the body's demands. Newborns also have a connection between the aorta and the pulmonary artery, called the ductus arteriosus, that allows some of the oxygen-poor (blue) blood to pass into the lungs. Unfortunately, this ductus arteriosus normally closes within a few hours or days after birth. Because of the low amount of oxygen provided to the body, pulmonary atresia is one of the heart problems that is labeled "blue-baby syndrome." Pulmonary atresia occurs in about one out of every 10,000 live births.

(I got this info from the Cincinnati Childrens Hospital website. They gave good info there)

HETEROTAXY SYNDROME-

Heterotaxy syndrome is a rare birth defect that involves the heart and other organs. The beginning of the word (hetero-) means “different” and the end (–taxy) means “arrangement.”
In heterotaxy syndrome, paired organs, such as the lungs or kidneys, are often mirror images of one another instead of having the unique characteristics of right and left that are normally present.
There are different forms of heterotaxy. All usually involve heart defects, of varying type and severity. In addition, organs such as the stomach, intestines, liver and lungs may be in abnormal places in the chest and abdomen. The intestines may have malrotation, which is when the loops of bowel are lined up incorrectly. With this problem the bowel can twist on itself (volvulus), so many children with malrotation need abdominal surgery to correct it. Some children with heterotaxy can have a very serious condition of the liver called biliary atresia. This also may require surgical intervention. There may also be irregularities with the skeleton, central nervous system and urinary tract.
The spleen may not work correctly or may be missing entirely. This can cause many problems, because the spleen helps the body fight infections. When the spleen is missing or doesn’t work correctly, patients have a more difficult time recovering from surgeries or infections. (Patients with heterotaxy may require multiple surgeries.) In some cases, there may be a functioning spleen, but it may be divided into several smaller spleens (polysplenia).
Sometimes children with heterotaxy have dextrocardia. This means the heart is in the right chest instead of the left chest.
Here are general descriptions of two types of heterotaxy. The morphology (structure) of the heart varies from child to child. Types of heterotaxy include:

• Asplenia or right atrial isomerism: Children with this condition have multiple heart defects. They may have septal defects (holes between the tissue dividing the two sides of the heart) and problems with heart valves, particularly the pulmonary valve. They may also have abnormalities of the blood returning from the lungs to the heart (anomalous pulmonary venous connection). The spleen may be absent (asplenia), and the liver and other organs may be on the wrong side of the body.
• Polysplenia or left atrial isomerism: Children with this condition may have septal defects (holes between the tissue dividing the two sides of the heart) as well as problems with heart valves and the heart’s electrical system. Some children with this problem have complete heart block, which is when the upper-chamber electrical system does not communicate with the lower-chamber electrical system. Most children require pacemakers for this problem. The spleen may be absent, or there may be several small spleens (polysplenia), instead of one spleen.

(heterotaxy info taken from Childrens Hospital of Philadelphia)

We don't know what kind of Heterotaxy we are dealing with yet. I am hoping they can tell us more about the heart defects and heterotaxy at our next Cardiology appt on Feb 18.