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Diagnosis of Congenital Heart Defects

Baby and doctor with stethescope
What are congenital heart defects? 

Congenital heart defects, or lesions, are parts of the heart that have not formed properly. They occur very early in a pregnancy, often even before a woman knows she is pregnant. These defects can include “holes” in parts of the heart, or missing or malformed parts of the heart.

What causes heart defects?

Defects tend to occur just after a woman becomes pregnant. What causes them is not very clear. One factor that seems to increase the risk of a defect is family history. If someone in your family has a defect, it is slightly more likely that your child will too. The risk increases from about 1 in 100 children to about 3 in 100.

How do defects affect the heart?

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.
  • They make the blood flow through the heart in abnormal patterns, forcing the heart to work harder.

How common are heart defects?

About 1 out of every 100 babies born each year have a heart defect. It's more common than people think it is. Congenital heart defects are the most common birth defect. 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.

What kinds of heart defects are there?

Heart conditions are often classified also divided into two groups: cyanotic and acyanotic.

A cyanotic condition has cyanosis as a symptom. Cyanosis is a bluish discolouration of the skin, caused by the circulation of blood that does not have enough oxygen. Cyanotic conditions include tetralogy of Fallot, truncus arteriosus, transposition of the great arteries, and tricuspid atresia.

In contrast, someone with an acyanotic condition does not show symptoms of cyanosis. Acyanotic conditions include patent ductus arteriosus, atrial septal defect, and ventricular septal defect.

What are the different 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.

When and how are children diagnosed with 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 do a history and physical exam. The cardiologist may also order one or more tests.

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 (ECG) shows heartbeat rhythms. An echocardiogram (echo) shows the structure of the heart and how well it is working. An echo is a lot like an ultrasound that a pregnant woman may have to measure the baby’s progress during her pregnancy.

A test called cardiac catheterization may be done as well. This is an invasive test in which tubes called catheters are inserted in the groin at the top of the leg and passed through the blood vessel into the heart. Catheters are used to measure pressures and oxygen levels. A dye may be used to to take pictures of the size and shape of blood vessels and chambers in the heart and how the blood flows through the heart and lungs.

What are the symptoms of a heart defect?

Babies and children may also have difficulties eating or gaining weight, or breathe faster than normal, or sweat when eating or sleeping. These symptoms are referred to as congestive heart failure. Some children turn blue (a condition called cyanosis) 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.

What is the most common type of heart defect?

The most common kind of congenital heart defects affect how blood flows through the heart. These include atrial/ventricular septal defects and patent ductus arteriosus. 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 "shunt lesions" or “left to right shunts.”

How are heart defects treated?

Many heart defects can be successfully managed, often in early infancy and sometimes even in the womb, before the baby is born. While heart defects generally are not “cureable,” they can be managed well enough to enable the child to function well.

Treatment depends on which part of the heart is affected. Some children will not need treatment if the effect on blood flow is minor. Others will need medication or intervention such as cardiac catheterization or surgery. Some defects are not treated right away, but wait until the child is older. Some defects are treated in stages.

What is the outlook for children with heart defects?

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.

Risks associated with heart defects: bacterial endocarditis

Certain types of heart defects put a child at risk of bacterial endocarditis, an infection of the heart valves. To protect against it, antibiotics before certain surgical procedures or a trip to the dentist will likely be prescribed.

Fraser Golding, MD, FRCPC

 

 

12/4/2009




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