Birth defects involving the heart

What are birth defects of the heart?

Birth defects of the heart are structural malformations occurring during development of a baby in the mothers womb. Such defects are thus present at birth and not acquired during life. In medical parlance they are termed congenital heart defects. Therefore, they are heart problems of children but may also be found in adults if the diagnosis was not made in childhood. With improvements in health care, more children are being diagnosed with defects of the heart because of improved access to hospitals, greater awareness amongst medical professionals and technological advances that allow easier detection.

There are different types of congenital heart defects. Based on their severity they may be classified as simple or more complex. Defects can involve the structure of the heart itself or the blood pipes (vessels) carrying blood to and from the heart. Alterations in the way blood flows as well as the pumping function of the heart lead to a circulatory system that is not copacetic (functioning in excellent order). Simply put, there may be holes in the heart, obstructions to blood flow, pipes that are not connected in the normal manner, patency of pipes that usually close after birth or defects that result in leaky valves. Consequently the cardiovascular system does not perform its function efficiently. Congenital heart problems can occur as isolated defects or as part of other systemic and organ defects.

What factors cause birth defects of the heart?

Like the development of other organs, formation of the heart and blood vessels is influenced by multiple factors. Birth defects involving the heart may come about as a result of the interplay between many of these factors. In many instances no specific cause is identifiable.

Environmental factors refer to biochemical conditions in which the baby develops (the mother). Thus certain illnesses affecting the mother as well as the ingestion of some drugs/chemicals during pregnancy may alter heart development.

The other important causative factors are genetic and chromosomal abnormalities. The general incidence of congenital heart disease is about 1 % . Chances of a child being born with an abnormal heart increase if one parent or sibling has a birth defect of the cardiovascular system. Other syndromes such as Trisomy 21 are associated with higher incidence of heart defects. Beyond genetic counselling and the adoption of informed reproductive decisions by parents, genetic factors are not within our control.

How do heart defects manifest?

Let us recall from the last article that normally the heart has a right atrium and ventricle separated by valves. Likewise there is left atrium and ventricle separated by valves. The right and left chambers are separated by a wall called a septum. A wall thus separates the atria and similarly another more thicker wall separated the ventricles. Right heart chambers pump blood to the lungs for oxygenation which returns to the left heart chambers for pumping to the body. Circulatory normality requires that the blood vessels are connected to the correct chamber.

Heart defects can be detected at birth during routine examination of the newborn baby or diagnosis can also be made later in life. Broadly defects may lead to bluish/purplish discolouration of the skin and mucous membranes visible at the finger tips and lips due to circulating blood containing lower oxygen content (cyanosis) or this phenomenon may be absent (acynotic defects). Some heart defects remain relatively without any particular symptom. Heart failure may be a manifestation of other congenital defects. Children with more severe or complex forms of defects are usually symptomatic soon after birth leading to earlier diagnosis.

Signs and symptoms that may indicate presence of heart defects include:

cyanosis (bluish discolouration of the skin)

a child that gets tired easily especially compared to their peers

rapid or laboured breathing

slow growth (failure to thrive)

abnormal heart beat patterns palpitations

poor feeding

excessive sweating

How are heart defects diagnosed?

Doctors can suspect the presence of a heart defect through noting reported symptoms and performing an examination on the child. Clinical suspicion needs to be confirmed through a series of test. Commonly an electrocardiogram, a chest X ray may paint a known pattern of certain types of heart defects. Because of the structural nature of the defects, imaging of the heart via echocardiogram (sonar of the heart) is usually needed. Cardiac catheterization is required in more complex defects or for specific clinical reasons and catheter based treatment.

Treatment of heart defects?

Correcting the defect and normalizing functioning of the heart and circulatory system is the goal of treatment in all defects. This is usually possible in simple defects such as closing holes in the heart. In more complex cases simply normalizing the physiological functioning of the circulatory system may be the only option. Treatment may involve a procedure performed by a paediatric cardiologist in the catheterization laboratory where the hole is closed with a device. Surgery is required when this is not possible. A holistic approach to treatment including consideration for the family is the usual practice.

Some minor defects that are inconsequential to the child may not require any treatment. Other simple defects may self correct or with the aide of medical treatment.

Some common defects

Holes in the heart

Atrial Septal Defect (ASD)

Holes in the heart refers to openings in either the wall between the upper two chambers (atria) or the lower pumping chambers (ventricles). These holes allow oxygenated blood to flow from the higher pressured left chambers into the lower pressure right chambers. In essence, inefficiency is created because this oxygenated blood is returned to the lungs instead of going to the body for use.

When the defect is in the inter-atrial septum it is referred to as an Atrial Septal Defect. The term Ventricular Septal Defect applies when the inter-ventricular septum has a hole. It is important to note that such simple defect may be part of a series of other structural abnormalities.

Defects causing cyanosis

Tetralogy of Fallot

This defect which cause what is referred to as the blue baby is one of the commonest cyanotic heart defects. The hallmark is that oxygen poor blood from the right heart mixes or flows to the left heart and thence to the body making circulating blood have a lower oxygen concentration manifested by cyanosis.

There are many other birth defects of the heart with various structural abnormalities. A discussion of these is beyond the scope of this article.

In a nutshell

Birth defects of the heart are not uncommon

Causes include various environmental and genetic factors

Defects may be simple or complex

Defects may lead to cyanosis (blue baby) or not

Symptoms are not specific for heart disease

Diagnosis requires medical examination and special tests

Most defects can be treated or the physiology corrected

The next article in the heart series will focus on Rheumatic Heart Disease.

* Dr Jones Nghaamwa is a cardiothoracic, heart and lung surgeon at Windhoek Central Hospital and Lady Pohamba Hospital.

Source: New Era Newspaper Namibia