About the disease
A congenital heart defect is a malformation of the heart or the great vessels. It is referred to as a ‘defect’ because it is the result of something ‘going wrong’ during the embryonic development of the heart and surrounding vessels, which takes place in the early weeks of pregnancy. There are many possible reasons why such defects should occur. There is no single causal factor; a number of different contributing factors must coincide to affect the development of the heart. Unfortunately, so little is still known about this process that such defects cannot be avoided. Certain malformations are known to be linked with genetic faults such as chromosome disorders (e.g. the ventricular septal defect that leads to Trisomy 21 / Down's syndrome).
Defects can occur in any phase of the heart's development. That is why there are such a large number of different heart defects and heart defect combinations. One possibility is that the interventricular septum does not develop properly and is left with ‘holes’. This is known as a ventricular septal defect (VSD), see Fig. 2.
Another possibility is that the heart does not rotate correctly during its development phase. This leads to positional defects of the major vessels, e.g. transposition of the great arteries (TGA), see Fig. 3.
It is also possible for several defects to occur together, for example an underdeveloped heart ventricle, failure of the vessels to rotate, and incomplete development of the interventricular septum (Fig. 4). This is a serious heart defect which has to be treated immediately after the child is born in order for it to survive.
Another, very different, type of defect is when the bypass connections of the foetal circulation required during pregnancy do not close after birth. This may result, for example, in an open foramen ovale (hole in the atrial septum) or a persistent arterial duct (open passage between the aorta and the pulmonary artery).
It is not the intention of this article to present a detailed description of all possible heart defects. For those seeking more complete information, we recommend the website Corience.
Patients and/or their families must make sure that the paediatric or general cardiologist treating them explains their particular condition in such a way that they understand which kind of heart defect they are dealing with, which restrictions it will involve, and what particular things they must bear in mind.
Author: Dr. med. Ulrike Bauer
Last update: March 24, 2010