It is a serious form of cyanotic congenital heart disease (CHD). In this CHD, there is malposition of two large vessels of heart known as aorta and pulmonary artery.
Anatomy and Physiology of TGA
Normally aorta arises from left sided ventricle (LV) and pulmonary artery from right sided ventricle (RV). In normal anatomy of the heart, there is pure blood coming to left ventricle and that is supplying pure blood to body parts via aorta, impure blood is coming to right ventricle and that is going to both lungs for blood purification.
When aorta and pulmonary artery origin reverses i.e. aorta from right ventricle and pulmonary artery from left ventricle, then it is known as Transposition of great arteries (d-TGA). When there is d-TGA, pure blood goes to the lungs via pulmonary artery and impure blood to the body from right ventricle to the aorta so child is blue in colour (cyanosis) as compared to pink colour of normal child.
So, child become blue very early in life, sometimes, within hours of the birth of the newborn.
In this situation, survival of the baby depends on mixing of pure and impure blood in heart via a hole in the heart itself. It can be either atrial septal defect (ASD)/patent foramen ovale (PFO), ventricular septal defect (VSD) or patent ductus arteriosus (PDA).
If this is not the case, then patient becomes early symptomatic in the form of bluish discolouration of lips and fingers or sometimes baby may be in shock like state.
Sometimes, TGA can be associated with narrowing of artery that supplies blood to the lungs (pulmonary artery), known as pulmonary stenosis (TGA with PS).
Cause of transposition of great arteries
Although no known causes are there but few like genetics, rubella or other viral illnesses during pregnancy, diabetes during pregnancy or if age of the mother is more than 35 years during pregnancy are some of the high risk factors related to TGA association.
Associated cardiac lesions with TGA
Associated lesions can be VSD, PDA, pulmonary stenosis, arch narrowing etc.
Clinical features of Transposition of Great Arteries in children
As mentioned above, if mixing of pure and impure blood is inadequate then patient will be very blue immediately after birth or may be in shock.
If not symptomatic early, then depending upon size of ASD, VSD, or PDA, child may be less symptomatic in first month of life and cyanosis may be missed by clinical examination as well.
If large VSD is there with TGA then child is generally not blue after birth and may present as difficulty in breathing or cough and cold like picture can be there.
If there is severe PS, then may have early cyanosis as compared when there is no PS.
Diagnosis of transposition of great vessels in children
It can be easily diagnosed even before birth of the baby by doing “Fetal echocardiogram (Fetal echo test)”. By antenatal diagnosis of TGA, we can timely plan delivery of the newborn.
After birth, it can be suspected clinically by seeing bluish-black discolouration of lips and fingers, shortness of breath etc, but can be confirmed by doing “Pediatric Echocardiogram” from the chest of the baby. By this test almost all cases can be easily diagnosed.
Other tests can be helpful in making the diagnosis are chest x ray and ECG.
Palliation for TGA
Sometimes, cardiac catheterization needs to be done for assessing whether operation can be done or not or used mainly for doing “Balloon atrial septostomy (BAS)” in newborns who are not having VSD, PDA but having a very small PFO and baby needs mixing of the blood and is in critical state. So that baby can be palliated for future surgery.
Treatment of Transposition of Great Vessels in children
Treatment of choice is by doing open heart surgery only in the form of “Arterial switch operation (ASO) in children”.
TGA repair in children
Total repair of transposition of great vessels needs to be done as early as possible, preferably in first 2 weeks of life when there is no VSD or PDA.
If there is large VSD or large PDA is there, then we can delay surgery for 1-2 months of age.
Arterial switch operation (ASO) in children
Coronary arteries are transplanted at great vessels level with closure of holes in heart if present. This is a complex operation and is done on cardiac bypass machine by opening the chest in midline.
Atrial switch operation in children (Senning or Musturd operation
In this operation, surgeon creates a baffle or tunnel between two upper chambers of the heart known as right and left atrium. By baffles, surgeon diverts pure blood to right ventricle and impure blood to left ventricle so that pure blood goes to the body by aorta and impure blood goes to the lungs for blood purification.
This is a palliative surgery only and needs to be done when patient can not be taken up for arterial switch operation in view of poor left ventricle size (regressed left ventricle or LV).
There is a risk of complications after Senning or Musturd operation that may include heart failure, baffle obstruction, and rhythm disturbances etc.
TGA with PS
If transposition of great artery is associated with pulmonary stenosis, then Rastelli operation needs to be carries out (VSD closure with placement of artificial conduit between RV and pulmonary artery for relieving PS).
If Rastelli operation is not possible then other surgical options like Nikaidoh, REV surgery to be done.
In TGA, child needs to be on lifelong follow up with pediatric cardiologist.
After arterial switch operation (ASO), many children do not undergo repeat surgery. But whenever there is some problems in the form of heart beat or rhythm issues (arrhythmia), leakage in heart valves etc, may need additional surgery or treatment.
After Rastelli operation, conduit may be require another surgery for replacing it as it will be short with the growth of the child.
TGA with Pregnancy
If transposition of the great arteries repaired (arterial switch operation) in early months of the life and is uncomplicated with no problems, it may be possible to have pregnancy but it needs to be cared closely. Always needs to talk with pediatric cardiologist before planning the pregnancy.
Results of surgery after TGA operation
Results of TGA surgery has been improved in last decades.
By doing arterial switch operation (ASO), we can achieve good cardiac function and quality of life.
In small number of patients, pulmonary arteries can be narrowed with the time, and it may require placement of stent in the narrowed section in cardiac cath lab by without surgical technique (Pulmonary Artery Stenting).
If operative result is good, then child usually can participate in physical activity and sports (After ASO operation).
Adults with TGA
All adolescents and adults with transposition of the great arteries require lifelong follow-up by an expert who deals with congenital heart disease (pediatric cardiologist).
After Mustard or Senning operation, there may be issue with heart rates or rhythms, poor heart pumping, abnormal leakage of the valves etc. Few patients may require placement of pacemakers.
After arterial switch procedure (ASO), quality of life is better as compared to Mustard and Senning operated patients. But, after ASO as well, patiet may have issues with coronary arteries, narrowing in pulmonary arteries, leakage in the valves etc.
After Rastelli repair, patient may require replacement of conduit as previously placed conduit may fall short with the growth of the patient.