CHD Info From the March of Dimes

The March of Dimes is a one of the several reliable sources of information on Congenital Heart Defects. Below are some excerpts from their website.
Congenital Heart Defects

About 40,000 infants (1 out of every 125) are born with heart defects each year in the United States (1). The defect may be so slight that the baby appears healthy for many years after birth, or so severe that its life is in immediate danger.

Heart defects are among the most common birth defects and are the leading cause of birth defect-related deaths (2). However, advances in diagnosis and surgical treatment have led to dramatic increases in survival for children with serious heart defects.

What tests are used to diagnose heart defects?
Babies and children who are suspected of having a heart defect are usually referred to a pediatric cardiologist (children’s heart disease specialist). This doctor will do a physical examination and often recommend one or more tests. These tests often include a chest X-ray, an electrocardiogram (which records heart rate patterns) and an echocardiogram (a special form of ultrasound that uses sound waves to take pictures of the heart). All of these tests are painless and non-invasive (nothing enters the child’s body). Some children with heart disease also may need to undergo a procedure called cardiac catheterization. In this procedure, a thin, flexible tube is inserted into the heart after the child is given medications to make him sleepy. This test provides detailed information about the heart and how it is working.

What causes congenital heart defects?
In most cases, scientists do not know what makes a baby's heart develop abnormally. Both environmental and genetic factors appear to play roles.

A few environmental factors are known to contribute to congenital heart defects. Women who contract rubella (German measles) during the first three months of pregnancy have a high risk of having a baby with a heart defect. Other viral infections also may contribute, as may exposure to certain industrial chemicals (solvents) (1, 3). Drinking alcohol in pregnancy also can increase the risk of heart defects, as may cocaine (3).

Certain medications increase the risk. These include the acne medication isotretinoin (Accutane and other brand names), lithium (used to treat certain forms of mental illness) and certain anti-seizure medications (3).

Certain chronic illnesses in the mother may contribute to the risk. For example, women with diabetes are at increased risk of having a baby with a heart defect (3). However, women with diabetes can reduce their risk by seeing their health care provider before pregnancy to make sure their blood sugar levels are well controlled. Women with an inherited error of body chemistry called phenylketonuria (PKU) also are at high risk of having an affected baby, unless they follow a special diet before and during pregnancy (4). Some studies suggest that women who do not consume enough of the B vitamin folic acid before and during the early weeks of pregnancy may be at increased risk of having a baby with a heart defect (3).

Scientists are making progress in understanding the genetics of heart defects. Since the 1990s, they have identified several gene mutations (changes) that can cause heart defects. For example, a March of Dimes grantee discovered a series of genetic steps that appears to contribute to a common, important group of malformations affecting the heart’s outflow tract (5). He also identified a gene that can cause a heart defect called an atrial septal defect (a hole between the upper chambers of the heart) and one that may contribute to hypoplastic left heart syndrome (underdevelopment of the heart’s main pumping chamber) (6, 7).

Heart defects also can be part of a wider pattern of birth defects. For example, about one-half of children with the chromosomal abnormalities Down syndrome (mental retardation and physical birth defects) and Turner syndrome (short stature and lack of sexual development) have heart defects (8). Children with Down syndrome, Turner syndrome and certain other chromosomal abnormalities should be routinely evaluated for heart defects. Heart defects also are common in children with a variety of inherited disorders, including Noonan (short stature, learning disabilities), velocardiofacial (craniofacial defects and immune deficiencies), and Holt-Oram (limb defects) syndromes (9).

What research is under way on congenital heart defects?
Scientists funded by the March of Dimes are among many who are trying to learn more about the causes of heart defects, so that they can develop better ways of preventing and treating them. For example, a number of March of Dimes grantees are studying genes that may underlie specific heart defects. March of Dimes grantees also are looking at how environmental factors (such as a form of vitamin A called retinoic acid) may contribute to congenital heart defects. Other researchers are exploring the possibility of prenatal surgery to correct heart valve abnormalities and help prevent serious heart problems (10).

For more information

• American Heart Association
• Congenital Heart Information Network
• Little Hearts

References
1. American Heart Association. Congenital Heart Defects. Accessed 7/8/05.

2. Kochanek, K.D., et al. Deaths: Final Data for 2002. National Vital Statistics Reports, volume 53, number 5, October 12, 2004.

3. Mone, S.M., et al. Effects of Environmental Exposures on the Cardiovascular System: Prenatal Period Through Adolescence. Pediatrics, volume 113, number 4, April 2004, pages 1058-1069.

4. Michals-Matalon, K., et al. Nutrient Intake and Congenital Heart Defects in Maternal Phenylketonuria. American Journal of Obstetrics and Gynecology, volume 187, 2002, pages 441-444.

5. Yamagishi, H., et al. Tbx1 is Regulated by Tissue-Specific Forkhead Proteins Through a Common Sonic Hedgehog-Responsive Enhancer. Genes & Development, volume 17, January 15, 2003, pages 269-281.

6. Garg, V., et al. GATA4 Mutations Cause Human Congenital Heart Defects and Reveal an Interaction with TBX5. Nature, volume 424, July 24, 2003, pages 443-447.

7. Garg, V., et al. Mutations in NOTCH1 Cause Aortic Valve Disease. Nature advance online publication, July 17, 2005.

8. Hoffman, J.I.E. Congenital Heart Disease, in Rudolph, C.D, and Rudolph, A.M. (editors): Rudolph’s Pediatrics, New York, McGraw-Hill Medical Publishing Division, 2003, pages 1780-1783.

9. Pajkrt, E., et al. Fetal Cardiac Anomalies and Genetic Syndromes. Prenatal Diagnosis, volume 24, 2004, pages 1104-1115.

10. Ohye, R.G., and Bove, E.L. Current Topics in Congenital Heart Surgery, in: Allen, H.D., et al (editors), Moss and Adams’ Heart Disease in Infants, Children, and Adolescents, 6th Edition, volume 1, Philadelphia, Lippincott Williams and Wilkins, 2001.