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| Heart Disease |
| What Is Dilated Cardiomyopathy? |
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By Stephanie Trelogan, MS
Reviewed
by Andy Avins, MD
Dilated cardiomyopathy occurs when diseased heart muscle fibers become weakened and cannot effectively pump blood to the body. The weak heart muscles also allow one or more chambers of the heart to expand. With time, the enlarged heart gradually deteriorates, causing congestive heart failure.
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Who Gets Dilated Cardiomyopathy?
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| About 30 percent of the time, dilated cardiomyopathy has genetic causes. |
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About two 2 out of every 100 people get dilated cardiomyopathy. It occurs most often in middle age, and it affects more men than women. However, this disease can occur in people of all ages, including children. Although dilated cardiomyopathy often occurs in people with no family history of the disease, about 30 percent of cases are thought to have genetic causes. |
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Nongenetic Causes of Dilated Cardiomyopathy
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Most cases of dilated cardiomyopathy occur as a result of other diseases and nongenetic risk factors. These include:
- Coronary artery disease is the most common cause of dilated cardiomyopathy.
- Chronic, excessive alcohol consumption can weaken the heart muscle, resulting in dilated cardiomyopathy.
- Peripartum cardiomyopathy is a form of dilated cardiomyopathy caused by pregnancy or recent delivery. This disorder is most common in women over the age of 30, and is more prevalent among women of African descent than in Caucasian women. People who are most at risk for this form of cardiomyopathy have a personal or family history of other risk factors for heart disease such as obesity, myocarditis, smoking, alcoholism, and malnutrition.
- Infections. Certain viral illnesses can cause an infection of the heart muscle known as acute myocarditis. Although myocarditis is rare, it can cause permanent damage that may result in dilated cardiomyopathy. In tropical regions, certain parasitic infections are also a major cause of dilated cardiomyopathy.
- Anticancer drugs, such as doxorubicin and daunorubicin, can damage the heart and cause dilated cardiomyopathy in about 0.4 to 9 percent of people, depending on the dose.
If you have any of these risk factors for dilated cardiomyopathy, or a family history of the disease, your doctor may suggest a screening schedule that is more aggressive than for the general public.
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More on Screening for Heart Disease (Coming Soon)
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Genetics of Cardiomyopathy
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| There are several genes that appear to cause dilated cardiomyopathy, although only one has been identified. |
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About 30 percent of the time, dilated cardiomyopathy occurs as a result of inheriting mutations in certain genes. (For news about recently discovered genes, see Related News below.)
The dystophin gene. So far, only one gene has been identified that is linked to risk of dilated cardiomyopathy. This gene makes a protein called dystrophin, which is found in muscle fibers. Mutations in this gene are responsible for certain types of muscular dystrophy, but can also cause a rare disease called familial X-linked dilated cardiomyopathy. This gene is on the X chromosome, which means that it follows an X-linked inheritance pattern. Men only need to inherit one copy of the mutated gene from their mother to be at risk, whereas women must inherit two mutated genes – a mutated copy of the gene from both parents – in order to be at risk.
Unidentified genes. Although researchers have only identified one specific gene that causes cardiomyopathy, they have identified several chromosomal locations that are linked to the disease. With time, researchers should be able to find mutations in genes at those locations that increase a person's risk for dilated cardiomyopathy. These unidentified genes are inherited in an autosomal dominant fashion, which means that a person only needs to inherit a mutated copy of the gene from one parent in order to be at risk.
Mitochondrial genes. In past studies, researchers had noticed that some people with dilated cardiomyopathy had structural defects in subunits of their cells called mitochondria. Mitochondria make energy for the cell and contain their own DNA. In a recent study, researchers decided to look more closely at the mitochondrial DNA in people with distorted mitochondria. They found that about 23 percent of these people had mutations in the mitochondrial DNA. This suggests that some cases of dilated cardiomyopathy may be passed on through the mitochondria. A person only inherits mitochondria from their mother, so although both men and women can inherit mitochondrial mutations that put them at risk for dilated cardiomyopathy, only women pass those mutations on to their children.
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Genetic Testing
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At this time there is no genetic test for the one gene that is known to cause dilated cardiomyopathy. If you have a family history of the disease, your doctor will probably recommend that you adopt lifestyle changes that are recommended for the general population, such as exercising, not smoking, and not drinking excessively. Your doctor may also recommend that you be screened for heart disease more regularly than people in the general population.
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More on Screening for Heart Disease (Coming Soon)
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Treatment
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| In most cases, doctors cannot treat cardiomyopathy once it develops. For this reason, it is important to be screened regularly if you have a family history of the disease or if you have other risk factors. Some patients with advanced dilated cardiomyopathy may require a heart transplant. Of those who do get a heart transplant, 75 percent live an additional five years. In the United States donor hearts are scarce, so those who qualify for heart transplantation often have to wait months, or even years, for a suitable match. While waiting, some people with declining heart function can use a small, implanted mechanical pump called a left ventricular assist device (LVAD) to take over much of the heart's blood pumping activity. Unfortunately, LVADs only work temporarily, so they are not a good substitute for transplant. |
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 Protein mutation linked to heart disorder |
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References
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Giles, T. D. (1997) Dilated Cardiomyopathy. In P. A. Poole-Wilson, et al. (Eds.), Heart Failure. (pp. 401–422). New York, NY: Churchill Livingstone, Inc.
Grünig, E., et al. (1998) Frequency and phenotypes of familial dilated cardiomyopathy. Journal of the American College of Cardiologists, 31, 186–194.
Durand, J. B., et al. (1995) Localization of a gene responsible for familial dilated cardiomyopathy to chromosome 1q32. Circulation, 92, 3387–3389.
Krajinovic, M., et al. (1995) Linkage of familial dilated cardiomyopathy to chromosome 9. American Journal of Human Genetics, 57, 846–852.
Bowles, K. R., et al. (1994). Gene mapping of familial autosomal dominant dilated cardiomyopathy to chromosome 10q21-23. Journal of Clinical Investigation, 98, 1355–1360.
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