Congenital Heart Diseases

Congenital heart diseases are malformations of the heart and the large blood vessels arising from it. They are the consequence of abnormal development of the organ while a baby is in the uterus. About 6-8 babies in every 1000 are born with congenital heart diseases. Many heart defects are relatively mild and do not require treatment. For children with significant heart lesions majority of them can be managed by medications, interventional cardiac catheterisation and cardiac operations. In only very small number of babies the heart defects are so severe that they are considered as inoperable, and the babies may die soon after birth.

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Causes

In most cases the congenital heart defects are unknown but there are two major factors influencing the development of fetal heart :

(1) Genetic factors

The development of all fetal organs is controlled by genes. Theoretically there should be an explanation to each case of congenital heart disease from the genetic point of view. However the link between genes and congenital heart malformation is very complicated, and is not well understood by scientists. Therefore for majority of patients it is still not possible to identify the exact genetic mechanism.

In some cases there may be a family history of similar heart problems, for example, one of the parents or siblings may have congenital heart defects. This is a signal that genetic influence is strong in that particular family with congenital heart defects. Still it does not mean that the genes responsible for the disease are known.

We know that children suffering from certain genetic disease such as Down's syndrome, which is caused by presence of an extra chromosome 21, have higher chance of having congenital heart defects. Again the mechanism of how an extra chromosome can modify the fetal heart development is far from clear.

(2) Environmental factors

These are extrinsic influence on the development of fetal hearts. They are often the results of maternal drug taking and maternal illness during pregnancy, usually in the first trimester when the fetal heart development is most critical. German measles that the mother has had while pregnant is well known to cause pulmonary stenosis, and also eye and brain defects. Certain drugs such as thalidomide, alcohol, radiation during pregnancy increase the risk of developing congenital heart disease and should be avoided if possible.

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Types

(1) Atrial Septal Defect

Atrial septal defect (ASD) is a common cardiac malformation often referred to as'hole in the heart'. The defect is a hole in the atrial septum, which is a structure separating the right and left atrium. The pressure in the left atrium is slightly higher than that in the right ventricle. Because of the pressure difference an ASD will allow shunting of blood from the left atrium to the right atrium and to the lung via the pulmonary arteries. The haemodynamic effects of an ASD depends on the amount of blood shunting to the lungs, and hence will be determined by the size of the defect.

Clinical presentation:

ASD rarely produces symptoms in a child even in moderate size defect. In infants a very large ASD may cause heart failure symptoms, such as breathlessness, feeding difficulty and impaired growth.


Treatment:

Small ASDs does not necessarily require treatment. Some small defects may close spontaneously 1-2 years after birth. Moderate size ASD should be closed either by surgery or transcatheter occlusion.

a) Medical treatment:

Drugs will be prescribed to control symptoms if heart failure develops.

b) Interventional cardiac catheterisation:

Transcatheter occlusion is suitable for moderate size ASD which is centrally located in the atrial septum. The occluding device is delivered through a large catheter advanced into the atria via a blood vessel in the groin. It involves only a small wound in the groin and the child can usually be discharged home the next day after the procedure.

c) Surgical treatment:

Large ASDs and defects not suitable for transcatheter occlusion are closed by surgery. Cardiopulmonary bypass is required to facilitate the procedure. Children usually stay in the hospital for 5-7 days after the surgery.

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(2) Coarctation of Aorta

Coarctation of aorta (CA) is a constriction or narrowing of the aorta, usually at a site opposite the ductus arteriosus which may or may not be patent at the time of diagnosis. The narrowing will create obstruction to the blood flow through the aorta. The left ventricle has to work hard to pump the blood through.

Clinical presentation:

1. If the narrowing of the aorta is mild it will not produce symptom. However the pulses in the legs will be weak because the narrowing creates resistance to the blood flow to the lower part of the body. The pulses in the arms are not affected and in fact may be stronger. This is reflected by higher blood pressure in the arms when compared to the legs. Also a heart murmur may be audible even though there is no symptom.

2. In babies if the narrowing is severe it may result in heart failure with symptoms such as breathlessness and feeding difficulty. Treatments: Coarctation of aorta in babies is a medical emergency because of the possibility of circulatory collapse. Surgical correction should be done as soon as possible.

a) Medical treatment:

Medications are prescribed to control heart failure and to stabilize the baby's condition before surgery. Prostaglandin may be used to keep the ductus arteriosus open or to reverse the constriction of the ductus. This may alleviate the narrowing of the aorta and improve the heart failure symptoms.

b) Surgical Treatment:

The operation is carried out to cut out the narrowed segment of the aorta and join the ends together. Alternatively the narrowed segment can be enlarged by incorporating the wall of an adjacent blood vessel to it.

c) Interventional cardiac catheterisation:

In older children with coarctation of aorta the lesion can be managed by dilatation using a specially designed catheter with an inflatable balloon at the tip. The catheter is advanced to the narrowed site through a vessel in the groin. This procedure can be applied to children who have residual obstruction of the aorta after previous surgical correction. In a small number of cases the narrowed site may constrict again after balloon dilatation. In this situation, a stent maybe useful to prevent reconstruction.

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(3) Ventricular Septal Defect

Ventricular septal defect (VSD) is a common cardiac malformation often referred to as'hole in the heart'. The defect is a hole in the ventricular septum, the structure separating the right and left ventricle. The pressure in the left ventricular is normally much higher than that in the right ventricle. Because of the pressure difference a VSD will allow shunting of blood from the left ventricle to the right ventricle, and to the lungs via the pulmonary arteries. The haemodynamic effect of a VSD depends on the amount of blood shunting to the lungs, and hence will be determined by the size of the VSD.

Clinical presentation:

Small VSDs cause no trouble but the child will have a heart murmur. Moderate or large VSDs produce heart failure symptoms, such as breathlessness, feeding difficulty and impaired growth. Some children may have recurrent infection in the lungs.

Treatments:

A small VSD without significant haemodynamic effect does not require treatment. Some small defects may close spontaneously 1-2 years after birth. Defects causing symptoms need surgical closure or transcatheter occlusion.

a) Medical treatment:

Drugs will be prescribed to control symptoms if heart failure develops.

b) Interventional cardiac catheterisation:

Although transcatheter approach is not widely used, it may be considered in selected cases to close haemodynamically significant VSD.

c) Surgical treatment:

Moderate and large sized VSDs are usually closed by surgery. Cardiopulmonary bypass is required to facilitate the procedure. Children usually stay in the hospital for 5-7 days after the surgery.

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(4) Transposition of Great Arteries

This is an uncommon disorder in which the aorta and pulmonary artery are in the wrong places. The aorta is connected to the right ventricle and the pulmonary artery is connected to the left ventricle. Because of the abnormal great artery connection the deoxygenated blood is delivered to the systemic circulation from the right ventricle via the aorta, without going through the lungs. Oxygenated blood from the lungs will be re-circulated via left atrium, left ventricle, pulmonary artery and back to the lungs. Babies born with this condition develop cyanosis immediately after birth. Without treatment many of them die soon because of lack of oxygen supply to major organs.

Clinical presentation:

1. the baby starts to look blue immediate after birth.
2. the baby may develop signs of heart failure such as shortness of breath and feeding difficulties several days later. Treatment:

a) Medical treatment:

A baby with TGA requires intravenous infusion, or the oral form of Prostaglandin to maintain the patency of the ductus arteriosus, a small vessel connecting the aorta and pulmonary artery, to allow oxygenated blood from the lungs to be distributed to the systemic circulation.

b) Interventional cardiac catheterisation:

Balloon atrial septostomy is performed soon after birth to enlarge the communication between the left and right atriums. A specially designed catheter is advanced to the left atrium from the right atrium usually via a large vein at the groin. The balloon at the catheter tip is then distended with fluid and pulled back rapidly. This will create an opening at the atrial septum allowing oxygenated and deoxygenated blood to mix.

c) Surgical correction:

The cardiac malformation is usually corrected by surgery within 7 days after birth. The aorta and pulmonary artery are disconnected and switched to their normal positions. The atrial septal defect is closed and the ductus arteriosus is ligated.

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(5) Patent Ductus Arteriosus

The ductus arteriosus is a normal structure in the fetus. It is a small vessel connecting the aorta and the pulmonary artery. Soon after birth it will close spontaneously within 2 days. If it remains patent it becomes a congenital heart malformation. Because the arterial blood pressure in the lungs is normally lower than that in the systemic blood vessel, a PDA will allow blood from the aorta shunting to the pulmonary arteries. The haemodynamic effect of a PDA depends on the amount of blood shunting to the lungs, and hence will be determined by the size of the PDA.

Clinical presentation:

1. A small PDA does not produce symptoms but the child will have a heart murmur.
2. A moderate or large PDA causes large amount of blood shunting to the lungs and put a strain on the heart. The child may have symptoms of heart failure, such as breathlessness, feeding difficulty, impaired growth.

Treatment:

a) Medical treatment:

Drugs will be prescribed to control symptoms if heart failure develops.

b) Interventional cardiac catheterisation:

Treatment of the PDA is now mostly performed by transcatheter occlusion. The procedure is to deliver a occluding device or occluding coil(s) to the PDA through a catheter advancing from vessel(s) at the groin. It requires only two small stab wounds at the groin and hence less traumatic than the surgical approach. After the procedure the child can be discharged the next day. However transcatheter occlusion is not suitable for newborn or for babies with small body size.

c) Surgical treatment:

The standard surgical procedure requires a large wound at the left chest to expose the PDA for ligation. The hospital stay will be longer. It is usually performed on small babies not suitable for transcatheter occlusion.

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(6) Tetralogy of Fallot

Tetralogy of Fallot is a common congenital cyanotic heart malformation.

In medical terms it has four elements of structural abnormalities:

1. ventricular septal defect
2. overriding of aorta
3. pulmonary stenosis
4. right ventricular hypertrophy

Basically there is a large hole in the ventricular septum. The pulmonary valve and part of the right ventricle leading up to the pulmonary artery are narrowed. As a result of the obstruction at the exit, the pressure of the right ventricle is increased and a significant amount of the blood flow from the right ventricle will be shunted to the left ventricle through the hole in the ventricular septum. There are two consequences with this abnormal blood flow: 1, the amount of blood distributed to the lungs is reduced and 2, deoxygenated blood from right ventricle is mixed with oxygenated blood in the left ventricle. These will result in cyanosis in the affected children.

Clinical presentations:

The symptoms of children with ToF is determined by the amount of blood circulating in the lungs.

1. In mild cases the blueness may not be very obvious.
2. In moderate to severe cases the cyanosis becomes significant. The affected children will develop breathlessness even on light exercise, and frequently need to adopt a squatting position.
3. A small number of children with ToF may develop 'spells', during which the cyanosis suddenly becomes extremely severe. If the spell is not reversed either spontaneously or by medical treatments the child may lapse into unconsciousness because of inadequate oxygen supply to the brain. Treatment:

It is rare for anyone with ToF to survive into adulthood without some form of surgical treatment.

a) Medical treatment:

When a child with ToF is having 'spell' the parents should calm the child especially if he or she is agitated. Placing the child in the knee-chest position may help to reduce the cyanosis. If the child does not recover in minutes he or she should be taken to the Emergency Department for urgent medical treatment. Oral medication may be prescribed to prevent recurrence of spells.

b) Surgical treatment:

Surgical correction of ToF is usually performed at around one year of age. Some small babies with ToF have early onset of severe cyanosis. Shunt operation is performed to improve the oxygenation. The procedure involves implantation of a small tube between a branch of the aorta and a branch of the pulmonary artery. This is to direct more blood to the lungs from the aorta making the babies less cyanotic while waiting for corrective surgery at one year of age.

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Treatment

Children who have minor heart defect may not need treatment and most of them are healthy and active. However they are at risk of bacterial infection involving the heart. Dental extraction or some surgical procedures may introduce bacteria to the blood stream therefore patients with congenital heart defects undergoing those procedures are advised to have a dose of antibiotic beforehand.

Significant heart lesions can be treated by the following methods:

(A) Medical treatment:

Medications are useful in controlling heart failure symptoms, maintaining the blood oxygen level and prevention of spells in certain heart lesions. But medications at the best are only able to improve symptoms only; there is no effect on the structural abnormalities. Surgical correction or interventional cardiac catheterisation is required to repair the heart lesion to normal or near normal.

(B) Interventional cardiac catheterisation

To perform a cardiac operation the heart must be exposed by a large incision on the chest. A large wound will increase the risk of infection and bleeding. It will be more painful and the recovery will be longer. Children undergoing cardiac operation will stay in the hospital for 5-7 days after the procedure. Interventional cardiac catheterisation is developed as an alternative to surgical treatment to correct heart lesions by transcatheter methods. The procedure is performed by introducing specially designed catheters into the heart or blood vessels. Devices to close holes in the heart or to occlude abnormal vessels are then deployed via these catheters. Some catheters have a inflatable balloon incorporated to the tips. Inflation of the balloon by fluid will enlarge narrow heart valves and blood vessels. By these means a lot heart lesions can be managed without surgery. As the catheter is advanced into the heart through blood vessels in the groin only tiny incision is required. Therefore the recovery is much shorter than surgical operation. Children treated by interventional cardiac catheterisation can be discharged home the next day after the procedure.

(C) Surgical treatment:

The idea of surgical correction is to reverse the structural abnormalities to normal anatomy, for example to close a hole in the heart, to enlarge narrowed segment of blood vessel or narrowed heart valves, to replace non-functional heart valves with artificial valves etc. Sometimes the surgery involves adding in new structures, e.g. shunt operation to increase blood flow to the lungs in Tetralogy of Fallot. The procedure is to implant a small tube between a branch of the aorta and a branch of the pulmonary artery, to direct more blood to the lungs from the aorta.

In some cardiac operations the heart beat must be stopped before the surgeons can cut open the heart chambers to repair the lesions. In these situation the child will be put on a heart-lung machine that take over the child's circulation and breathing. This is referred to as 'open heart surgery'.

Medications, surgical corrections and interventional cardiac catheterisation are complimentary to each other. Some patients have had all three kinds of treatment before the heart lesions can be corrected totally. Nowadays very few congenital heart diseases are regarded as not treatable. Even for the extremely complicated heart lesions some form of treatment can be offered to relieve the symptom or to achieve partial if not complete correction.

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Care

(1) Knowledge of the heart lesions and operation

Children are dependent of their parents. To care for a child with congenital heart disease before or after cardiac operation it is important for parents to know the heart lesion; how it will affect the child and how the child will respond if the condition changes. Parents need not to be an expert on the child's heart lesion but to be confident on the day-to-day assessment of the child's symptoms. Nurses and doctors will discuss with you about the results of the operation, possible complications during the recovery phase, medications that are required, and warning signs that indicates something wrong. The cardiac operation that is performed may be just one of the stages towards total correction. Parents should have a clear idea of what is going on. The child may be seen by other doctors for other illnesses and it is important that parents can communicate with them about the heart lesion and the latest development.

(2) Follow-up visits

Close and regular follow-up is necessary after cardiac operation to detect any complication. Some complications are fatal if not treated promptly, e.g. pericardial effusion which means accumulation of fluid within the 'sac' surrounding the heart. During the visits medications may be adjusted according to findings of physical examination, cardiac ultrasound and chest X-ray. If the child's condition is stable the follow-up can be spaced out gradually.

(3) Observation at home

The child's condition may change after discharge home. Parents are advised to observe the followings: general state, overall activity, respiration, colour, temperature, puffiness of face, feeding difficulty, vomiting and abdominal discomfort. Inform our staff at the Day Care centre or the Children's ward by phone if you think the child is ill or if you worry about your child's condition. An early assessment may be required to clarify the observation. However if the child is obviously ill and immediate treatment may be needed then you should bring your child to the nearest Accident & Emergency Department without delay. Arrangement to see our specialist again will be made by the concerned paediatricians.

(4) Medications

Drugs should be taken according to the instruction from the pharmacy. The medications should not be withheld without the advice from doctors or nurses. Our pharmacist or nursing staff will explain to you the action and possible side effects of each medication. If you have any question about your child's medications you should clarify with our staff before going home.

(5) Chest Physiotherapy

It is not uncommon to have retention of sputum and secretion in the lungs after cardiac operation. This may result in chest infection. All children will have post-operative chest physiotherapy while staying in hospital. Parents are advised to learn simple skills such as chest percussion and breathing exercise from our physiotherapists so that the therapy can be continued at home if necessary.

(6) Wound Care

The surgical wound usually heals in 10-14 days. The importance of personal hygiene cannot be overemphasized. Redness, swelling of the wound may indicate infection and should be reported immediately. If the wound does not gap the child can have a bath every day at home. After a bath the wound should be kept dry and protected with dressings.