Varieties of Single Ventricle Defect
What is a single ventricle defect?
Single ventricle defect is a general term used to describe several distinct congenital heart defects. The same anatomical problem is at the root of each of these defects: The heart has only one functioning ventricle (instead of two).
A healthy heart is a strong, muscular pump that continuously pushes blood through the circulatory system to deliver oxygen and nutrients to the body. The heart has four chambers: Two on the right that pump oxygen-poor (blue) blood to the lungs for oxygen, and two on the left that pump oxygen-rich (red) blood through the aorta and out into the rest of the body.
The two chambers on the right are called the right ventricle, and the two on the left are called the left ventricle. In a heart with single ventricle defect, one of the ventricles is underdeveloped and the other must do all the work.
Because of this, your baby's heart is overworked and the blood is not receiving enough oxygen from the lungs. There may be a risk of stroke and other complications.
The most common types of single ventricle defects are:
- Hypoplastic left heart syndrome (HLHS): In this syndrome, the chambers of the left side of the heart are small and underdeveloped, with valves that don't work properly. The left side can't pump effectively, so the right side must take double duty, pumping to both the lungs and the rest of the body. A newborn baby with HLHS may appear to be well during the first hours or even days of life. However, a day or two after birth, the natural openings between the right and left sides of the heart close. That is normal but, in a baby with HLHS, it can be fatal because it leaves the overworked right side of the heart no way to pump blood to the body.
- Tricuspid atresia: This defect occurs when the tricuspid valve, which connects the right atrium and right ventricle, is underdeveloped. Variations in your baby's heart structure can influence this defect differently, but generally the result is that blood returning from the body to the heart cannot enter the right ventricle properly. This usually means the blood cannot reach the lungs to be oxygenated, especially after the natural openings between the right and left sides of the heart close a day or two after birth.
- Single left ventricle: This defect occurs when one ventricle of the heart (usually the right ventricle) is underdeveloped and both atria (pumping chambers) connect to the working ventricle. This connection can be either through one valve (a common-inlet ventricle) or two valves (a double-inlet ventricle). The resulting problem is that blood cannot be pumped to the lungs normally for oxygenation.
- Mitral valve atresia: The mitral valve connects the heart's left atrium and left ventricle. Mitral valve atresia occurs when the mitral valve does not develop properly. As a result, blood from the left atrium does not flow to the left ventricle. The left ventricle becomes small and underdeveloped, and the right ventricle must take on the work of pumping blood out to the body. Blood is not oxygenated properly because the right ventricle cannot efficiently pump blood both to the lungs and to the body.
- Double outlet right ventricle (DORV): In a healthy heart, each ventricle has one great vessel attached to it. For the left ventricle, it is the aorta, through which blood is pumped out into the body. For the right ventricle, it is the pulmonary artery leading to the lungs. In a heart with double outlet right ventricle, both the aorta and the pulmonary artery are attached to the right ventricle. As a result, proper oxygenation does not occur in the blood being pumped out to the body.
Often, there are other heart defects present in a heart with single ventricle defect. These other defects may actually be helpful in maintaining heart function while your child's diagnosis and treatment are being decided.
What causes a single ventricle defect?
A single ventricle defect occurs during the first eight weeks of fetal development, when the heart is forming, and only a single ventricle emerges.
Some congenital heart defects may have a hereditary link, causing heart problems to occur more often in certain families. Children born with Down syndrome are at increased risk of having congenital heart defects. Other chromosomal abnormalities or environmental factors may also contribute to the occurrence of a single ventricle defect.
Most of the time, however, this heart defect occurs by chance, for no clear reason. A single ventricle defect cannot be prevented but in most cases it can be treated.
What are the signs and symptoms of a single ventricle defect?
A baby born with a single ventricle defect will usually be critically ill and require immediate care. Symptoms vary for each child, but commonly may include:
- Cyanosis: A blue (or gray) tone to the skin, lips, or nails
- Pale, cool or clammy skin
- Difficult or rapid breathing
Accelerated heart rate
Your baby's doctor also may suspect a heart defect if he or she hears a heart murmur — an abnormal whooshing noise, heard through a stethoscope exam, that indicates troubled blood flow. If your child has a heart murmur, your doctor can analyze its quality, loudness and location within the chest to get an idea of whether your child may also have a more serious heart problem. At that point, other tests are needed to help with diagnosis (see below).
How is a single ventricle defect diagnosed?
Due to the advances in medical science in recent years, babies born with single ventricle defects today have a much improved outlook.
A clear diagnosis is the first step to treatment. A pediatric cardiologist (a children's heart doctor) can use several tests to confirm your child's diagnosis. These tests may include:
- Chest X-ray: A beam of electromagnetic energy creates images on film that show the inside structures of your baby's body. A chest X-ray doesn't provide a definitive diagnosis, but it helps the doctor determine your baby's heart size and structure.
- Cardiac magnetic resonance imaging (MRI): This test uses three-dimensional imaging technology produced by magnets. The resulting image helps to determine the blood flow and functioning of the heart as it pumps.
- Electrocardiogram (ECG or EKG): This test, conducted by attaching patches with wires (electrodes) to the baby's skin, records the heart's electrical activity. It will show if there are abnormal heart rhythms (arrhythmias or dysrhythmias) and heart muscle stress.
- Echocardiogram (Echo): This test uses high-pitched sound waves to produce a moving image of the heart on a video screen. It is similar to an ultrasound and can be used to assess the structure and position of the parts of the heart and heart defects. In most cases of single ventricle defect, an echocardiogram provides the definitive diagnosis.
- Cardiac catheterization: During this procedure, your doctor inserts a thin flexible tube (a catheter) into a blood vessel in your baby's groin, then guides it up to the inside of the heart. A dye may be injected through the catheter to make your baby's heart structures visible on X-ray pictures. The catheter also measures blood pressure and oxygen levels.
How is a single ventricle defect treated?
Once diagnosed, your child's specific treatment may vary depending on his or her individual needs. Your child may be admitted to the intensive care unit (ICU) or special care nursery and may be placed on oxygen or a ventilator to help with breathing. Intravenous (IV) medications may be given to assist heart function.
Children with single ventricle defects often need more than one procedure. Sometimes an initial procedure is necessary to regulate blood flow. If too much blood is flowing to the lungs, your child may require a band placed around the pulmonary artery to restrict it. If too little blood is flowing to the lungs, a shunt (a small tube) maybe inserted to increase it.
However, these are temporary treatments intended to regulate blood circulation in preparation for surgical repair of the defect. Without corrective surgery, your child may be at risk for a stroke or other complications.
Procedures vary but the most common is a Fontan operation, in which your baby's surgeon separates the heart into two circulations that will allow for improved oxygenation of the blood. This reduces the workload of the single ventricle and reduces the risk of other complications. In very serious cases, your baby's doctor may recommend a heart transplant.
After surgery for a single-ventricle defect, many children live a relatively normal life. However, vigorous physical activities and sports may need to be limited and regular checkups with a cardiologist will be necessary to monitor the possibility of infections, heart rhythm problems, fluid retention, and blood clots.
About treatment for single ventricle defect at Children's
Single ventricle defects is treated through Children's cardiovascular program one of the largest and oldest pediatric cardiovascular programs in the region. Team members consistently achieve treatment results that are among the best in the nation. Each year, care is provided for thousands of the region¹s sickest children with heart conditions, including fetuses, newborns, infants, children, adolescents, and adult, long-term patients with pediatric cardiovascular conditions.
For more information, please call Children's Heart Clinic at 1-800-938-0301.