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.