Congenital heart defects, or lesions, are parts of the heart that have not formed properly. They occur very early in pregnancy, often even before a woman knows she’s pregnant. These defects can include “holes” in parts of the heart, or missing or malformed parts of the heart.
The vast majority of heart problems in newborn babies are due to a combination of genetic factors and teratogens. Heart disease in the mother may lead to congenital heart disease in the baby. Chromosomal abnormalities are associated with heart defects: up to 10% of newborn babies with heart defects have a chromosomal abnormality and 33% of all children with a chromosomal abnormality will have a congenital heart defect. Maternal diseases such as type 1 diabetes have also been linked to heart defects. Classic examples of cardiovascular teratogens include rubella virus, thalidomide, isotretinoin, and alcohol.
Symptoms can be very subtle or quite severe, resulting in serious illness. Some defects may become apparent later in life. Congenital heart defects are more common in people with certain syndromes, like Down syndrome, which affects a number of organs.
Defects generally affect the heart in two ways: they block or slow down blood flow in the heart or the blood vessels near the heart, or they make the blood flow through the heart in abnormal patterns, forcing the heart to work harder.
Types of heart defects
There are about 35 known types of congenital heart defects. They range from the simple to the complex. Some are more common than others. There are many varieties of any given type of defect and a large potential for combination defects. The more common ones include ventricular septal defect, tetralogy of Fallot, transposition of the great arteries, atrioventricular septal defect, and coarctation of the aorta. A number of defects occur in combination.
The most common kind of congenital heart defects are what are referred to as "flow defects" since they affect how blood flows through the heart. These include atrial and ventricular septal defects. With these conditions, blood flows from the left side of the heart to the right side, meaning that too much blood flows into the lungs. These defects are also referred to as “left to right shunts.”
Heart conditions are often classified into two groups: cyanotic and acyanotic. A cyanotic condition has cyanosis as a symptom. Cyanosis is a bluish discolouration of the lips, gums and skin, caused by the circulation of blood that doesn’t have enough oxygen. In contrast, someone with an acyanotic heart condition does not show symptoms of cyanosis.
Cyanotic heart conditions include tetralogy of Fallot, truncus arteriosus, transposition of the great arteries, and tricuspid atresia. Acyanotic heart conditions include patent ductus arteriosus, atrial septal defect, and ventricular septal defect.
Symptoms of heart defects
Babies and children with heart defects may have difficulties eating or gaining weight, breathe faster than normal, or sweat when eating or sleeping. These symptoms are referred to as congestive heart failure. Some children turn blue or have abnormal blood pressure. Not all children have symptoms, while some have a combination. Sometimes the existence of a heart murmur may indicate a problem.
Diagnosis of heart defects
Sometimes doctors can diagnose a heart defect even before the baby is born, using a fetal echocardiogram, which provides a picture of the baby’s heart. However, defects are usually identified days or even months after birth, when symptoms become obvious.
To diagnose a heart defect after birth, the cardiologist will usually take a history and do a physical examination of the newborn baby. A chest X-ray will give the doctor information about your baby’s lungs, as well as the size, shape, and position of the heart. An electrocardiogram shows heartbeat rhythms, while an echocardiogram shows the structure of the heart and how well it’s working. An echocardiogram is a lot like an ultrasound that a pregnant woman may undergo to measure her baby’s progress during the pregnancy.
A test called cardiac catheterization may be done also. This is an invasive test in which catheters, or tubes, are inserted in the groin at the top of the leg and passed through the blood vessel into the heart. Dye is used to show blood flow, and the size and shape of blood vessels and chambers in the heart. Pressures and oxygen levels can be measured.
Treatment of heart defects
Treatment depends on which part of the heart is affected. Some children will not need treatment if the effect on blood flow is minor, while others will require medication or intervention such as cardiac catheterization or surgery. Many heart defects can be successfully managed, often in early infancy and sometimes even in the womb, before the baby is born. Some defects aren’t treated right away, but can wait until the child is older. And some defects are treated in stages. While heart defects generally aren't curable, they can be managed well enough to enable the child to function well.
With advances in technology and our understanding of heart defects, the outlook for most children is positive. The risk of serious side effects and complications from treatment is much lower than it used to be. The majority of children will reach adulthood. Children with simple conditions may lead completely normal lives. Children with more complex conditions usually face more challenges.
For more information, see the "Heart Conditions" resource centre.