Single ventricle is one of the most complex and rare types of heart defects present at birth (congenital heart defect). It occurs when the fetal heart does not develop normally early in the first trimester of pregnancy. Prenatal heart circulation is different than adults and the heart continues to evolve after birth.The fetal heart begins its development as a long tube. During the first trimester, the lower part of this tube normally divides into two pumping chambers: the left ventricle and the right ventricle. However, there are rare cases in which this normal separation does not occur, and the baby is born with one functional ventricle instead of two. As a result of this defect, oxygen-rich blood and oxygen-poor blood mix together in the single ventricle instead of remaining separate. Some oxygen-rich blood needlessly travels back to the lungs, and some oxygen-poor blood uselessly travels to the rest of the oxygen-demanding body. Unless corrected surgically, single ventricle usually results in heart failure and death. However, surgical correction is available. Most patients will undergo at least two surgeries to correct single ventricle: the bi-directional Glenn (or the hemi-Fontan) and the Fontan. Together, these operations redirect oxygen–poor blood from the body straight to the lungs, bypassing the heart. In turn, the single ventricle is responsible for pumping freshly oxygenated blood to the body. Although these procedures may correct the defect, no procedure may cure it.
One sign of single ventricle is cyanosis – a bluish tint to the child’s skin, lips, fingernails and other parts of the body (often called blue baby). Other possible signs of single ventricle include: Blue Baby * Easily fatigued, especially during crying spells and at feeding time * Low tolerance for exercise or extra exertion * Shortness of breath (dyspnea) and/or rapid breathing * Fainting (syncope) or collapsing * Difficulty eating, breathing or sucking * Poor weight gain * Slow growth or other physical retardation * Heart murmur, as detected by a physician In severe cases, the child may also show signs of heart failure, which include the following: * An abnormal heart murmur * A crackling sound of fluid in the lungs (rales), which is a sign of pulmonary congestion * A rapid heartbeat (tachycardia) or abnormal heart rhythms (arrhythmias) * Swelling and fluid retention (edema) in the liver or gastrointestinal tract (in advanced stages of heart failure) * Hypertrophy (muscle thickening) or enlargement of the heart * Liver malfunction
In addition to a patient medical history and a complete physical examination, a physician will generally order one or more of the following tests when diagnosing single ventricle: * Chest x-ray to get an image of the heart's chambers, vessels and muscles. This will also help physicians to see whether there is an overcirculation of oxygen through the lungs, as is often seen with this condition. * Electrocardiogram (EKG) to gauge the electrical activity of the heart. * Echocardiogram to determine the relationships, dimensions, dynamics, and function of all heart chambers, valves, blood vessels, and walls. It also may gauge the direction and speed of blood flow within and around the heart, give some indication of the workload placed on the lungs and check the performance of the heart valves. Both fetal and infant echocardiograms are available. This is usually considered the definitive test to diagnose a single ventricle. * Cardiac catheterization to determine if there are abnormalities present that could not be defined with echocardiography. During the cardiac catheterization, an angiogram may be done, in which a special dye (contrast medium) is injected into the An angiogram is an imaging test used to visualize the size, shape and location of blood vessels.blood vessels to view the activity of vessel walls, valves and the heart muscle. This procedure is usually not required for the initial diagnosis of the condition nor planning the first surgical procedures. It is frequently done in order to plan subsequent surgical procedures. * Blood tests (particularly arterial blood gases) to assess oxygen levels and detect other indicators of illness that may be present in the blood.
The treatment for single ventricle has only been available for about 20 years, so long-term prognosis is not yet known. In the short-term, cardiovascular function improves tremendously. However, patients who have undergone surgery for single ventricle are at an increased risk for certain complications such as thrombosis, atrial flutter (a type of arrhythmia) and fluid around the heart (pericardial effusion) or chest (pleural effusion). This may require lifelong monitoring and possibly even medications. The patient may be advised to avoid certain competitive sports and training that involve short bursts of intense activity (e.g., sprinting, weight-lifting). However, many of these children may participate in aerobic sports such as swimming, running, baseball, soccer, and gymnastics so long as they can set their own pace. Additionally, antibiotics may be recommended before dental procedures and other surgeries to prevent infection of the heart lining (bacterial endocarditis). Because of an increased risk of clots in the lungs after the hemi-Fontan and Fontan procedures, most of these children receive low dose aspirin on a daily basis, similar to the precautions that adults with coronary artery disease follow. Monitoring the function of the liver and intestines is also necessary as some patients may development a malfunction in their performance. This may require dietary modifications and possibly medications In addition, children with single ventricle may be required to make changes to their routine infant immunization schedule during the first two years of life. Parents should consult with their pediatrition about what changes should be made. In the long-term, there have been reports of people experiencing heart failure and even requiring heart transplantation 10 to 20 years after being treated for single ventricle. Therefore, children who have been treated for single ventricle are urged to avoid the risk factors associated with heart failure, which include: * Smoking * Obesity (body mass index of 30 or greater) * Lack of exercise * Unhealthy dietary habits, such as high salt intake, instead of eating a heart-healthy diet * Alcohol abuse * Abuse of some types of drugs (primarily amphetamines and cocaine) A severe congenital heart defect of this nature may be corrected but never cured. Therefore, the child will require specialized care with a pediatric cardiologist and, later in life, an adult cardiologist with special training in the care of adult congenital heart disease, for life. Because the cause of single ventricle is unknown, there are no known strategies to prevent it. However, it has been shown that any type of congenital heart disease in either the mother or father increases the chances of a defect developing in the fetus.
The treatment for single ventricle generally involves at least two surgeries performed at separate times in the child’s life. If possible, the first surgery is usually performed at three to six months of age. There are a variety of names for this surgery, which include the following: * Glenn * Bidirectional Glenn procedure * Glenn shunt operation (or modified Glenn shunt operation) * Glenn anastomosis * Partial Fontan * HemiFontan During this surgery, the superior vena cava (which collects oxygen-poor blood from the upper part of the body) is connected directly to the pulmonary artery (which travels from the single ventricle to the lungs), bypassing the heart. This new pathway allows oxygen-poor blood from the head and upper body to passively flow to the lungs, without getting mixed with oxygen-rich blood in the single ventricle. Once the blood has become enriched with oxygen in the lungs, it goes back to the heart and is pumped out to the body. The interatrial septum (wall between the receiving chambers) is usually removed (atrial septectomy) at this time to allow free mixing of blood within the receiving chambers This is a crucial step in avoiding the mixing of oxygen-rich and oxygen-poor blood. However, it is only half-finished because the oxygen-poor blood returning from the lower part of the body has not yet been re-routed. At this stage, the baby will still have a bluish tinge, but will be better able to handle infection and other problems. The second surgery, called the Fontan, is usually performed before the child reaches the age of three, and allows oxygen-poor blood from the upper and lower body to flow directly to the lungs. After this surgery, there is no longer any mixture of oxygen-rich and oxygen-poor blood, and the skin tone should become normal and healthy. One variation of the Fontan is known as the lateral tunnel Fontan, or a total cavo-pulmonary connection (TCPC). In this procedure, a patch (made of either synthetic materials or the patient's own tissue) is used to create a tunnel within the right atrium. The tunnel links two major veins, the superior vena cava and the inferior vena cava, which are then connected to the pulmonary artery. A slight variation of the lateral tunnel Fontan is the fenestrated Fontan. In this procedure, a hole is made in the tunnel. This hole allows for decompression of the blood into the right atrium when the pressure within the tunnel gets too high. Later, if the patient has stabilized, the hole can be closed with either a stitch or a catheter procedure. Studies are ongoing toward perfecting computer-imaging techniques that, in turn, can help surgeons plan the best surgical treatment and outcome for each patient. In rare cases, patients who experience complications during surgery or who are unsuitable candidates for either of the two procedures may undergo a heart transplant.