What is Atrioventricular Septal Defect (AVSD)?
An atrioventricular septal defect (AVSD) is a heart defect in which there are holes between the chambers on the right and left sides of the heart, and the valves that control blood flow between these chambers may be malformed. This condition is also called an atrioventricular canal defect or an endocardial cushion defect. With an AVSD, blood flows where it normally should not go. The blood may also contain less oxygen than usual, and the excess blood may be drawn into the lungs. This extra blood pumped to the lungs makes the heart and lungs work harder, which can lead to congestive heart failure.
There are two main types of AVSD that can occur depending on which structures are malformed:
Complete Atrioventricular Septal Defect
A complete AVSD occurs when there is a large hole in the center of the heart, allowing blood to flow between the four chambers of the heart. This hole occurs where the septa (walls) usually meet, separating the two upper chambers (atria) and the two lower chambers (ventricles). There is also a common atrioventricular valve in the center of the heart instead of two separate valves - the tricuspid valve on the right side of the heart and the mitral valve on the left side of the heart. This common valve often has leaflets(s) that may not properly form or close tightly. A complete AVSD occurs during pregnancy when the common valve does not separate into two separate valves (the tricuspid and mitral valves) and when the septa (walls) separating the upper and lower chambers of the heart do not develop until they meet in the heart center.
Partial or incomplete atrioventricular septal defect
A partial or incomplete AVSD occurs when the heart has some but not all of the defects of a complete AVSD. There is usually a hole in the wall of the atrium or in the wall of the ventricle near the center of the heart. A partial AVSD usually has both mitral and tricuspid valves, but one of the valves (usually the mitral) may not close completely, allowing blood to leak back from the left ventricle into the left atrium.
Causes and risk factors
The causes of congenital heart defects, such as an AVSD, are unknown in most children. Some children develop heart defects due to changes in their genes or chromosomes. In particular, an AVSD is common in children with Down syndrome, a genetic disorder that includes an extra chromosome 21 (also called trisomy 21). It is also believed that congenital heart defects are caused by a combination of genes and other risk factors, such as objects the mother comes into contact with in her environment, what she eats or drinks, or certain medications she takes during pregnancy.
Diagnosis
An AVSD may be diagnosed during pregnancy or shortly
after childbirth.
During pregnancy
During pregnancy, screening tests (also called prenatal tests) are done to check for birth defects and other conditions. An AVSD can be diagnosed during pregnancy with an ultrasound (which creates images of the baby using sound waves), but whether the defect can be seen with an ultrasound or not depends on the size or type (partial or complete) of the defect. AVSD. A doctor may order a fetal echocardiogram to confirm the diagnosis if an AVSD is suspected. A fetal echocardiogram is an ultrasound of a baby's heart that shows more detail than a typical prenatal ultrasound. A fetal echocardiogram can show problems with the structure of the heart and the proper functioning of the heart.
After the Baby is Born
During a physical examination of an infant, a complete AVSD may be suspected. With the help of a stethoscope, a doctor often hears a heart murmur (an abnormal "hissing" sound caused by blood flowing through an abnormal opening). However, not all heart murmurs are present at birth. Babies with a complete AVSD usually show signs of problems within the first few weeks after birth. When symptoms appear, they may include
- Breathing problems
- Beating heart
- Weak pulse
- Ash or bluish skin color
- Poor nutrition, slow weight gain.
- Easy to tire
- Swelling of the legs or abdomen
In partial atrioventricular septal malformations, if the openings between the chambers of the heart are small, signs and symptoms may not appear during the neonatal or infancy period. In these cases, people with a partial AVSD may go undiagnosed for many years.
Symptoms that may indicate worsening of a complete AVSD or partial AVSD in a child include:
- Arrhythmia, heart rhythm disorder. An arrhythmia can cause the heart to beat too fast, too slow, or erratically. When the heart is not beating properly, it cannot pump blood efficiently.
- Congestive heart failure, when the heart cannot pump enough blood and oxygen to meet the body's needs.
- Pulmonary hypertension, a type of high blood pressure that affects the arteries of the lungs and the right side of the heart.
A doctor may order one or more tests to confirm the diagnosis of an AVSD. The most common test is an echocardiogram. This is an ultrasound of the heart, which can show problems with the structure of the heart, such as holes between the chambers on the right and left sides of the heart, and any irregular blood flow. An electrocardiogram, which measures the electrical activity of the heart, a chest x-ray, and other medical tests can also be used to make a diagnosis. Because many children with Down syndrome have an AVSD, all children with Down syndrome need an echocardiogram to check for an AVSD or other heart defects.
Treatment
All defects of the atrioventricular septum, both partial and complete, usually require surgical intervention. During the operation, all holes in the chambers are closed with patches. If the mitral valve does not close completely, it is repaired or replaced. In a complete AVSD, the common valve splits into two separate valves—one on the right and one on the left.
The age at which the operation is performed depends on the state of health of the child and the structural features of the AVSD. If possible, surgery should be performed before the lungs are permanently damaged by too much blood being pumped into the lungs. Medicines can be used to treat congestive heart failure, but this is only a short-term measure until the baby is strong enough to have surgery.
Infants who have undergone surgical repair of an AVSD are not cured; they may have lifelong complications. The most common of these complications is mitral valve insufficiency. This is when the mitral valve does not close completely, allowing blood to flow back through the valve. A leaky mitral valve can force the heart to work harder to deliver enough blood to the rest of the body. a leaky mitral valve may need surgical repair. A child or adult with an AVSD will need regular follow-up visits with a cardiologist to monitor their progress, avoid complications, and check for other health problems that may develop over time as the child gets older. With proper treatment, most children with an AVSD grow up to be healthy and productive.