Congenital Heart Defects
What are congenital heart defects?
The word congenital means 'from birth'. A congenital heart defect is therefore an abnormal condition of the heart that has been present since birth, though it may not be recognised until some time later.
A congenital heart defect is usually a structural malformation, but occasionally can be a disturbance in the rhythm or the pumping ability of the heart. It results from a derangement in the building processes of the heart in the first 12 weeks (first trimester) of pregnancy, during which all the major body organs are being formed.
The most common structural problem is a 'hole in the heart'. This is an abnormal internal communication between the left and right sides of the heart. It may be a result of development failure (eg ventricular septal defect). Instead it could be due to a 'hole', which is present naturally before birth, which has failed to close afterwards. In medical terms this is known as patent foramen primum and secundum.
There is an artery present in babies in the womb which normally closes off and shrivels after birth. If this stays open for some reason, the blood flow of the heart becomes abnormal. Another reason is the narrowing of a heart valve or major artery, which causes the heart to work harder to overcome the extra resistance to flow. Less common reasons for congenital defects include arteries and veins connected up wrongly to the heart, and even more rarely, hearts with the wrong number of chambers and vessels.
There are many kinds of congenital heart defect with combinations of different abnormalities.
How does it occur?
Any baby can be born with a congenital heart defect. About 1 in 100 babies are born with some sort of a congenital heart defect. The risk of it happening again is very slightly higher if a couple have already had a baby with a congenital heart defect. It is more likely in babies of women, for example, who have diabetes which is not well controlled or Systemic Lupus Erythematosus.
Why does it occur?
In about 97% of cases, a specific cause cannot be identified. German measles (rubella) infection of the mother during the first trimester is a known cause. The baby is most vulnerable in non-immune women up to the 16th week of pregnancy. This is why a rubella test is always done early in the first pregnancy to see whether immunity has naturally developed from previous infection. Rubella-immune women are not at risk from contact with people with active rubella infection. Ideally rubella testing should be performed before pregnancy so that immunisation can be carried out well in advance.
Rare causes are excessive exposure to X-rays, and drugs. It is always best not to take any medication during pregnancy unless the benefits to mother and baby far outweigh the risks. Chromosomal and congenital abnormalities, such as Down's and Marfan's syndromes are often associated with congenital heart defects.
Very rarely, congenital heart disease can be inherited. It is always helpful to know if there is a family history of similar problems.
What are the symptoms?
Many heart defects are now picked up when a mother has a routine ultrasound scan whilst pregnant. If there is any suspicion of a problem, then a foetal echocardiogram may be done. This is a specialist test done at about 16-20 weeks of pregnancy, which enables a more detailed view of the heart.
There may be none at all, and the problem may only be picked up during a medical check after birth or at school. Babies may fail to thrive, with poor feeding, and a lack of weight gain.
A bluish complexion may be noticed, particularly on the lips and tongue (cyanosis). This happens because blood which has yet to reach the lungs to pick up oxygen (deoxygenated blood which is dusky bluish-red in colour.) mixes with blood that has been through the lungs (oxygenated blood which is bright red). This process happens with a big 'hole in the heart' or with a change in direction of blood flow through the heart because of other types of congenital defect.
As the child gets older, shortness of breath may develop. This can be because of the mixing of blood as described, and also because the heart is pumping blood very inefficiently through the lungs, causing a need to breathe faster to get more oxygen into the blood. This type of shortness of breath is a symptom of 'heart failure', better thought of as heart strain. This can happen as a result of a narrow main artery or heart valve, which the heart works hard to overcome, but gets strained and tired in the process.
Some children find that squatting relieves the shortness of breath, and learn to do this quite naturally. This is because the squatting position alters blood flow to the heart, and reduces some of the strain on the heart.
In severe heart strain, the feet, ankles and legs may become puffy and swollen. This is because the heart is not clearing the venous blood returning to it fast enough, and a back pressure builds up, forcing fluid back out into the tissues. The effect is obviously greater lower down the body, so that is where the fluid builds up.
What are the risks?
A minor congenital heart defect may present very little or even no risk to the child, and may even heal itself in time. More severe congenital heart defects obviously present risks to the child's well being and growth, becoming greater with the increasing severity of the defect. Severe congenital heart defects can increase the blood flow through the lungs, and this damages them in time if left untreated.
These defects result in abnormal blood flow, and increase the risk of bacteria in the bloodstream settling in the heart and causing an infection (endocarditis). This is rare except during surgical or dental procedures, which can introduce bacteria to the bloodstream, so antibiotic cover is usually given just before these treatments to prevent endocarditis.
This field is evolving so rapidly that better and more treatments are becoming available all the time. A parent may feel especially anxious about a child with a congenital heart defect because of knowledge of peers during their own childhood, but it is important to remember that today's investigations and treatment have become very much more effective and far safer.
What are the tests?
- Blood tests: These are useful to check that anaemia, kidney or liver problems are not developing as a result of the congenital heart defect.
- Electrocardiogram (ECG): This measures the electrical activity of the heart through sticky wires on the chest and limbs, and gives information about the heart structure and function.
- X-rays: A chest x-ray can show enlargement of the heart and may show congestion of the lungs by fluid caused by heart strain.
- Ultrasound: This is a very useful and painless investigation. A harmless beam of high-frequency sound waves are bounced off the heart and related structures, creating a moving image of the heart. It can pinpoint problems in a very detailed way. Doppler ultrasound is used to study the direction and quantity of blood flow. There are newer and very sophisticated variations on this theme constantly evolving.
- CT/MRI Scan: This provides a much clearer picture of the heart and its structures and is totally painless. The images produced can be used to give the treating doctor a better visualisation of the heart. It can be very helpful with diagnosis and for monitoring on-going treatment.
- Cardiac catheterisation: This method is used if the defect is complicated, or if there is a need for greater detail, and is done often before surgery. A thin long tube (catheter) is threaded into the heart from a vein in the groin. It makes it possible to measure the blood pressure in different parts of the heart, take blood samples to measure the oxygen content, and inject dye which shows up on x-ray filming, enabling moving images of the heart to be taken.
What is the treatment?
Good doctor-patient communication: An important part of treatment is a good explanation of the disorder and how symptoms are produced, and what to expect from the investigation and treatment options. A specialist in congenital heart defect (paediatrician or paediatric cardiologist) is best placed to provide detailed explanations and outline the exact plan for an individual child. The whole field is developing rapidly, and new techniques are constantly being introduced.
Drug treatment: This includes taking oxygen by inhalation and diuretics (drugs that promote the formation of urine) by mouth or injection. The aim is to offload some of the fluid building up in the lungs and body and reduce the strain on the heart. Small babies may need to be fed through a tube running down the back of the nose and into the stomach (nasogastric tube). All these treatments apply to ill children, who often need hospitalisation.
Surgery: Heart surgery may be needed to correct defects which do not heal on their own, such as big holes in the heart or narrowed valves which need to be opened. These forms of surgery are commonplace, with a low risk and a high success rate. The result usually cures the problem at once and permanently.
Bigger and more complicated defects may not be totally curable, but very ingenious techniques are now available to get the best possible result, aiming for a normal quality of life. In this case, regular specialist check ups are normal. It is also possible that more than one operation will be necessary, with the first during infancy and further surgery when the child is older. If a serious congenital heart defect cannot be corrected surgically, heart transplantation may be considered. If the lungs become damaged, heart and lung transplantation may be felt to be necessary.
What are the treatment side effects?
All drug treatment can cause allergic rashes and reactions, though these are rare. A careful assessment of their likelihood and whether the risk is worth taking will be made by the prescribing doctor.
The anaesthetic has its own particular side effects. These can be quite different between individuals, and they should be discussed with the anaesthetist beforehand. In general, the anaesthetics used for children's' surgery are low risk, and are administered by highly trained specialist anaesthetists with great experience of their field.
All forms of surgery carry a small but recognised danger of excess bleeding and infection, even with the best possible technique. The particular side-effects of the actual operation being done can be explained by the surgeon performing the operation. The majority of operations performed are for the most common and simplest defects, and are considered low risk. Heart surgery on babies is particularly less uncertain than ever before.
Organ transplantation carries the risk of rejection of the donor organs by the child receiving them. This is combated with a combination of drugs which damp down the rejection response. These in turn have their own risks, and they will be explained by the specialist planning the treatment.
What self-help strategies are there?
General health and lifestyle: Following a healthy lifestyle, with no tobacco, taking none or only very small quantities of alcohol in pregnancy, coupled with a healthy balanced diet and avoiding all drugs as far as possible will minimise the controllable risk factors for a congenital heart defect occurring, or recurring in a subsequent pregnancy.
Further pregnancies: As there is a small risk of a congenital heart defect occurring in subsequent pregnancies, a detailed ultrasound scan of the unborn baby may be done early on in the pregnancy to screen for congenital heart defects.
Last updated 21 December 2021