Congenitally Corrected Transposition of the Great Arteries (CCTGA)
CCTGA is a rare heart defect in which the heart’s lower half is reversed.
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A normal heart has four "rooms", divided into two sides. The right side pumps blood from the body into the lungs. The left side pumps the blood from the lungs out to the body. Each side has an atrium and a ventricle. The atrium acts like a "waiting room" for the blood. The ventricle does the hard work of pushing the blood out to the lungs or body. At the entrance and exit from each ventricle is a valve, which acts like a door These valves allow the ventricle to fill with blood from one side, and then push it out the other.
Each ventricle and valve is designed to do its specific job. The right ventricle is designed to give the blood the gentle push to send it to the lungs. It is bigger than the left ventricle, and does not have as much muscle. The left ventricle is designed to give the blood a strong push out to the body. It has less space inside, because its thick walls take up more space. The valve between the left atrium and the left ventricle, the mitral valve, is the body’s strongest valve. It is designed to stay shut against the strong push of the blood out to the body.
How common is CCTGA?
CCTGA is a rare heart defect. 0.5%-1% of all those with heart defects are estimated to have CCTGA. This means there are about 5,000 – 10,000 people in the United States with CCTGA. These are rough estimates based on birth rates.
How does CCTGA develop?
In the womb the heart starts out as a simple tube. It then bends in two, creating the right and left sides of the heart. In CCTGA, it folds in the wrong direction. The ventricle that was supposed to grow on the right side is on the left. The ventricle meant to grow on the left is on the right. Because the valves are part of the ventricle, they are also reversed.
One of the most confusing things about CCTGA is the use of the words "left" and "right". It can be described as having "a right ventricle on the left side" and "a left ventricle on the right side". This only makes sense if you understand that a left ventricle is still a left ventricle, even when it is on the right side. This is because it still has its unique anatomy designed to serve the body, while the right ventricle is designed to serve the lungs. In CCTGA, the right ventricle serves the body, while the left serves the lungs. As the right ventricle was designed to serve the low pressure blood vessels in the lungs, it struggles to serve the high pressure blood vessels of the body.
What causes CCTGA to develop?
More research is needed on why all heart defects, including CCTGA, develop. CCTGA has one of the lowest reported rates of recurrence - one study reported that of 120 parents with L-TGA, none had babies with heart defects. One 2001 study reported that L-TGA shows clustering which suggests an environmental factor. More research is needed in the causes of L-TGA and other heart defects.
How is CCTGA diagnosed?
Some infants and children born with CCTGA have heart murmurs, heart rhythm problems, and/or show signs of heart failure. If they have a VSD (hole in the heart) they may also be cyanotic (blue). In these situations, an echocardiogram is typically done and a diagnosis made.
However, it is not unusual for CCTGA to be found later in childhood or adulthood. This is because you can have no symptoms and have CCTGA. Often it is the start of new symptoms - a new murmur, rhythm problems, or heart failure symptoms - that leads to a diagnosis of CCTGA. Sometimes it is found accidentally when routine heart tests are done.
Echocardiography can be used to diagnose CCTGA in adulthood. But rates of misdiagnosis of CCTGA using echocardiography at adult cardiac centers are high. One study reported that community level centers missed the diagnosis of CCTGA on echo. The unusual arrangement of the ventricles makes measuring CCTGA with echocardiography particularly difficult. Many doctors now prefer cardiac MRI when evaluating CCTGA. For those with implanted devices that make MRI impossible, CT scans can be used.
If I have CCTGA, can I have children?
Most women with CCTGA are able to have children successfully. The exceptions are if your heart function is too weak, if you have serious lung problems, and/or if you have low oxygen levels in your body. If you have CCTGA, you should get a consult from a specialized ACHD clinic before becoming pregnant. If you become pregnant, your ACHD cardiologist and ob/gyn team should take special steps to protect your heart from over-work. For example, vacuum-assisted delivery may be used to protect your heart from strain.
What are the long-term impacts of unrepaired CCTGA?
One of the mysteries of CCTGA is its wide range of health impacts. Some people born with CCTGA live many years with no health problems. It is not uncommon for people to be diagnosed with CCTGA in their forties or fifties. In one case, a woman was coincidentally diagnosed with CCTGA at age 83 having had five children. On the other hand, some babies born with CCTGA die in infancy. Many people diagnosed with CCTGA have no or few symptoms as children and young adults, but develop problems as they age. Outcomes seem to be better for those born without additional heart defects such as a hole in their heart (VSD).
One major factor is how well the right ventricle responds to pumping to the body. In most people with CCTGA, the right ventricle gets thicker than normal, or "hypertrophied". This helps it pump harder. When you have CCTGA, neither your right nor left ventricle look like “normal” ventricles, because they have each adapted to their new roles. How well you do in the long run depends in part on how well your heart can adapt. One study showed that 75% of those with CCTGA still have good heart function at age 45.
The four areas that tend to cause problems are rhythm issues, lung issues, valve issues, and heart function issues. Each of these areas is described below.
What health problems can occur with CCTGA?
- Problems with heart rhythm
Almost everyone born with CCTGA has abnormal "wiring" in his/ her heart. All hearts use an electric impulse to make the heart contract. The impulse starts at the top and makes the atria contract. It then travels through a "relay box", called the AV node. The AV node sends the impulse out to the two ventricles and causes them to contract. The heartbeat's distinctive "flub-dub" is caused by first the atria and then the ventricles contracting.
In almost everyone with CCTGA, the AV node is divided in two. This dual node often causes problems in the heart's rhythm. One common problem is heart block. In first-degree heart block, the beat slows down in the AV node. There is a delay between your "flub" and your "dub". In second-degree heart block, only some beats travel through the AV node to the ventricles. Your heart may not be able to beat as quickly or as efficiently as it should. In third degree heart block, or complete heart block, no beats travel through the AV node. Your atria and ventricles start to beat separately. This can cause light-headedness and fainting. In rare instances, it can be fatal. Pacemaker therapy is used to treat heart block. Up to 45% of those with CCTGA need pacemakers.
- Pulmonary hypertension
Many people born with CCTGA also are born with pressure problems in their lungs. Because the left ventricle is designed to pump out to the body, when it serves the lungs it can create too much force. People with CCTGA can also have narrowing or blockages in the vessels from the heart to the lungs. These can also cause lung pressure to rise. Over time, too much pressure in the lungs can cause pulmonary hypertension, heart enlargement, and a leaky tricuspid valve.
- Why a leaky tricuspid valve is a problem
People with CCTGA often develop leakage in their tricuspid valve. In CCTGA, this valve is located between the atria and the ventricle on the left side of the heart. This valve has to stay shut against the heart's strongest push out to the body. In a normal heart, this is the location of the mitral valve. The tricuspid valve is not designed for this additional workload. In addition, many people with CCTGA also have abnormalities in this tricuspid valve. This also makes this valve more prone to leakage.
Over time, tricuspid valve leakage ("insufficiency") can grow worse. There are two possible reasons why this might occur. One is the excess workload. The other is that the ventricle itself is stretching and weakening. This stretching can cause the valve to leak. These two reasons can be connected, since too much workload can cause the ventricle to stretch and weaken.
In some people with CCTGA, replacement of the tricuspid valve is recommended. When done early, replacing this valve may improve symptoms and protect or restore heart function. However, valve replacement can only be done if the heart function is only mildly weakened. f the systemic right ventricle is too weak, valve replacement is no longer an option. When done late, tricuspid valve replacement has been linked to high mortality. Valve replacement in CCTGA should only be done at centers that specialize in ACHD surgery.
- Problems with heart failure
In some people with CCTGA, the systemic right ventricle weakens enough to develop heart failure. Heart failure is when the heart becomes too weak to clearing fluid efficiently. More information can be found on heart failure here. Many medications now exist to help with heart failure. If heart function is only mildly weakened, valve replacement may also be considered to help improve heart function. Pacemaker therapy, including biventricular pacemakers, can also be used to help the heart beat more efficiently. If heart failure becomes too severe, heart transplant may be considered.
Are there restrictions on how much I can exercise?
This depends on your particular heart anatomy, heart function, and previous surgeries. Most people with CCTGA have few if any limitations on what they can do. You should ask your ACHD cardiologist what the particular recommendations are for you.
What other defects are common in CCTGA?
About 60% of those diagnosed with CCTGA also were born with a VSD - a hole between the two ventricles. This means that they were blue, or "cyanotic", at birth. This happens because some of the "blue" blood meant to go to the lungs goes through the hole and out to the body instead. People with CCTGA and a VSD are almost always diagnosed as babies. They also usually have surgery to close their hole as infants or children. It may be that the actual number of people without VSD is higher, since those without a VSD are much more likely to go undiagnosed.
About 40% of those with CCTGA also have a single ventricle. This means that the hole in their heart is so big that the two ventricles merge. The right and left ventricles become two sides of a common chamber. About 20% of people with CCTGA have dextrocardia.
This means that their heart is on the right side of their chest. 30%-50% of those with CCTGA also are born with a narrowed pulmonary artery to their lungs (pulmonary stenosis), described below.
What surgical treatments exist for CCTGA?
Most adults with CCTGA will have undergone either no surgery or a VSD closure. Some people also have had a conduit or shunt put in to help reduce pressure in the lungs. Sometimes a valve is repaired. All of these techniques leave the left side serving the lungs and the right side serving the body.
In the 1980's, a new technique was developed called the "double switch procedure". In this operation, a conduit is created to shunt the blood from one side of the heart to the other. The heart's major arteries are also detached and reconnected. This corrects the circulation so that the heart's left side serves the body and the right side serves the lungs. This operation is complex and still has considerable risk. It is usually only undertaken in infants and children who have started developing significant heart function problems. The double switch procedure is very rarely used in adults. This is because the heart's ventricles usually do not adapt well to changing "jobs". The double switch operation is still considered to be experimental. It should only be undertaken by adult congenital cardiac centers that do many such surgeries a year.
What are the long-term outcomes of the double-switch procedure?
The oldest people to have undergone a double-switch procedure are now in their twenties. This means we do not yet know what the long-term outcomes will be. Short-term results are encouraging. If you had a double-switch procedure as a child, you no longer have a systemic right ventricle. Many problems discussed in this section will not apply to your anatomy. However, you still are prone to the electrical problems discussed below. Surgery cannot repair the heart’s "wiring". The surgery itself may also cause additional problems. Surgical scarring can cause future rhythm problems. Conduits may become blocked and need re-operation. It is important to remember that the double-switch is not a "cure" for CCTGA. Everyone born with CCTGA should continue to receive regular care at a specialized adult congenital heart clinic.
What are the long-term outcomes for adults with repaired CCTGA?
At adult age, two groups of patients can be distinguished. The first are patients in which diagnoses was made by a pediatric cardiologist. These patients most frequently have associated heart defects, either operated on or not. Residual VSD or pulmonary stenosis are common. Second, asymptomatic patients that are diagnosed in adulthood, having been referred to the cardiologist due to ECG abnormalities, chest radiograph deviations, systolic murmurs due to failing AV valve, or atrial tachycardia or AV block. One study reported a 20-year survival of 75% in patients with congenitally corrected transposition of the great arteries (60). Common complications seen in patients with l-TGA are right ventricular dysfunction, tricuspid regurgitation, residual left ventricle outflow obstruction, and complete heart block (Table 71-10). Heart failure can occur, most typically in the fifth decade, as the morphological right ventricle fails to serve as the systemic ventricle.
What kind of cardiology care is recommended for adults with repaired and unrepaired CCTGA?
CCTGA is considered a moderate complex CHD, and the American College of Cardiology has recommended that CCTGA patients be seen regularly at regional ACHD centers.
During adulthood, focus of treatment will be placed on avoidance of systemic ventricle dilatation and failure by tricuspid valve surgery. Cardiac MRI for assessment of RV function is optimal, due to the limitations of using echocardiography in the context of a systemic RV. Cardiac CT can be used in patients for whom MRI is no longer an option. Tricuspid valvuloplasty is rarely successful because of recurrent regurgitation. Tricuspid valve replacement may lead to worsening of heart failure postoperatively. Valve replacement should only be undertaken in the context of well-preserved RV function at a regional ACHD center by a surgeon with experience in ACHD. You should also continue to protect yourself from heart infection (endocarditis).
Since CCTGA is a complex defect, you should receive regular care at a specialized ACHD clinic. It is important that you see doctors who know about your special needs and can help keep you feeling your best. New treatments for your symptoms may also be available.