Internationally, congenital heart disease is one of the most common forms of birth defects in children. Priya Kulasagaran looks at what this disease entails and how it manifests.
In Malaysia, the Health Ministry estimates that about 4,000 to 5,000 children are born with congenital heart disease every year.
This projection is based on the global incidence of congenital heart disease of eight to 10 per 100 births, coupled with the country’s annual birth rate of 500,000.
The ministry’s statistics further reveal that around a third of children with congenital heart disease do not require any medical intervention.
Of those who do require intervention, half would need surgery during early infancy, while the other half will need medical help later in life.
“Congenital” essentially means problems that are present at birth, and congenital heart disease actually refers to a myriad of heart defects – ranging from simple defects with no symptoms, to complicated defects with serious consequences.
While the diagnosis and treatment of complex heart defects has greatly improved in recent years, children and adults with congenital heart disease require specialised care to manage their condition in the long-term.
How the heart works
The size of a closed fist, the heart is divided into four chambers, namely the two upper atria and the two lower ventricles.
The atria have thin walls and serve as reservoirs for blood, and boost the amount of blood moving into the ventricles.
The right side of the heart takes in oxygen-depleted blood, while the left side pumps out oxygen-rich blood to the entire body.
Leading in and out of the heart are a few main vessels; the inferior vena cava; the superior vena cava; the aorta (the largest artery in the body); the pulmonary artery; and the four pulmonary veins.
The heart also has valves to make sure the blood flows in only one direction; these open and close as a result of pressure changes within the four heart chambers.
Each valve has cusps, which are anchored to the heart wall by cords of fibrous tissue, to maintain tight closure and prevent blood from flowing backwards.
The left ventricle pumps oxygen-rich blood out to the rest of the body; since this involves a high level of pressure, the left ventricle wall is three times thicker than the right ventricle.
Blood then enters the aorta, before flowing into the branches of many smaller arteries, providing the body’s organs and tissues with the oxygen and nutrients they need.
After oxygen in the blood is released to the tissues, the now deoxygenated (oxygen-poor) blood returns to the heart through veins, the blood vessels that carry deoxygenated blood.
This blood, which looks blue, enters the right atrium of the heart and then travels into the right ventricle.
The right ventricle then pumps deoxygenated blood into the lungs, where blood cells bind with the oxygen we breathe in.
The oxygen-rich blood, which appears red, then returns to the left atrium and enters the left ventricle, where it is pumped out to the body once again.
Types of heart defects
Among the problems that heart defects cause is to allow too little or too much blood flow to the lungs; in the former case, the body will not be able to get the oxygen it needs, while excess blood passing through will cause undue stress on the lungs.
Meanwhile, undeveloped heart chambers or blockages in the veins restrict the sufficient amount of blood that the body needs.
Simple heart problems may only require continuous monitoring and can be managed with medicines.
In some cases, simple defects may close up on their own as the baby matures into an adult.
Examples of such a congenital heart defect are septal defects, more commonly known as “holes in the heart”.
The septum is the wall that separates the right and left heart chambers, and prevents blood from mixing between the two sides of the heart.
There are two types of septal defects; the atrial septal defect, where there is a hole in the part of the septum that separates the atria; and the ventricular septal defect, where the hole is positioned between the ventricles of the heart.
While smaller septal defects tend to close on their own as the baby grows into childhood, medium and larger sized ones may require treatment or surgery.
Simple congenital heart defects also can involve the heart’s valves, including improperly formed valves which do not allow enough blood to pass through, or do not close tightly enough to prevent blood from flowing in the wrong direction.
The most common sort of valve defect is pulmonary valve stenosis, where the pulmonary valve (which allows blood from the heart to flow into the lungs) is narrowed.
In severe cases, heart can get overworked from trying to pump blood into the lungs, and cause symptoms such as fatigue and heavy breathing.
With complex congenital heart diseases, the problem tends to be the presence of more than one sort of defect – these, more often than not, need to be remedied with surgery.
Tetralogy of Fallot is a common example of such a complex defect, and is actually a combination of four heart defects.
This includes a ventricular septal defect, pulmonary valve stenosis, an “overriding aorta” that is located right above the hole in the heart, and right ventricular hypertrophy (where the right ventricle is thicker than normal).
In tetralogy of Fallot, not enough blood is able to reach the lungs to get oxygen, and oxygen-poor blood flows to the body.
Babies and children who have tetralogy of Fallot have episodes of cyanosis, which refers to the blueish tinge on the skin due to the lack of oxygen in the body.
Possible risks and symtomps
Usually, congenital heart defects occur within the first eight weeks of pregnancy.
At this stage, the heart is in the process of developing from a simple tubular structure to a more fully-formed organ.
Studies carried out so far indicate there are links between some types of congenital heart defects and a mother’s exposure to drugs, diseases or chemicals during pregnancy.
Alcohol overconsumption during pregnancy for instance, can lead to foetal alcohol syndrome, and a high proportion of children with this syndrome develop congenital heart disease.
Genetic conditions, such as Down’s syndrome and Turner’s syndrome, can cause congenital heart disease – although these disorders tend to cause a wide range of complications as well.
Women with diabetes are five times more likely to give birth to a baby with congenital heart disease than women who do not have diabetes.
The theory here is that high levels of insulin in the blood may interfere with the normal development of a foetus.
However, the general consensus among doctors and scientists is that there no is direct evidence as to what exactly causes congenital heart defects
While researchers continue to study the role of genetic and environmental factors, in vast majority of cases, there is no known reason as to why these defects occur.
Usually, more severe congenital heart defects are detected after delivery, or within a month of delivery.
In some cases, symptoms can be obvious, such as a bluish tint to the skin, lips or fingernails; or rather benign, like a heart murmur.
Since the condition refers to a range of different heart defects, general symptoms may include extreme fatigue, poor feeding as an infant, chest pains, or rapid breathing.
Symptoms may also sometimes not develop until the teenage years or early adulthood.
Managing in the long-term
Thanks to advances in science and healthcare, many children with congenital heart disease go on to live full and productive lives as adults.
Reflecting this success rate is an emerging sub-speciality within cardiology, with medical professionals catering to the needs to adults who have congenital heart disease, particularly those with more complex defects.
Most people who have complex heart defects may need to pay special attention to how their condition affects issues such as employment, pregnancy, and medication for other health issues.
Among the complications which may crop in adulthood are respiratory tract infections (infections in the lungs and airways) – a higher risk in people with congenital heart disease.
They are also more prone to or endocarditis, an infection of the heart lining or valves; this usually develops when an infection in another part of the body, such as gums or skin, spreads through the blood into the heart.
Heart rhythm problems, or arrhythmia, are a common problem as well, and can increase the risk for blood clots.
Some types of congenital heart disease can cause the blood pressure inside the arteries that connect the heart and lungs to be much higher than it should be, leading to pulmonary hypertension.