Cardiomyopathy is a serious condition in which the heart muscle becomes damaged and cannot pump blood adequately. While serious, cardiomyopathy is relatively rare, affecting approximately 50,000 Americans. Usually symptoms do not appear until the disease has progressed. When they occur, symptoms include shortness of breath, fatigue, and heartbeat abnormalities.
There are three major forms of cardiomyopathy Figure 01.
- Dilated (congestive) cardiomyopathy. This is the most common type of cardiomyopathy. In this type, one or more of the chambers of the heart stretches out of shape and becomes larger and weaker. This form occurs most often in middle-aged men, although it also affects women, children, and older people.
- Hypertrophic cardiomyopathy. This is the second most common type of cardiomyopathy, and yet it occurs in only around 0.2% of the US population. In this form, the muscular walls of the heart thicken so that the main pumping chamber (the left ventricle) becomes smaller, and its pumping action is limited.
- Restrictive cardiomyopathy. This third form occurs even less often than the second type. In this rare disease, extra tissue grows in the heart, causing the chamber walls to stiffen and lose their ability to pump blood.
Figure 01. Types of Cardiomyopathy
Dilated cardiomyopathy can occur as a result of infections, as a complication of pregnancy, and as a result of abusing certain drugs or alcohol. However, in approximately 80% of cases the cause remains a mystery.
- Infections. Some cases are caused by bacterial or viral infections that inflame the heart muscle (myocarditis).
- Pregnancy. Dilated cardiomyopathy sometimes occurs in women during the last three months of pregnancy, or within six months after delivery. The group most at risk is African-American women who have had several children already, and who are older than 30 years of age.
- Medications. Some powerful medications given to treat cancer (particularly doxorubicin and daunorubicin) can also cause the heart muscle to stretch and weaken. Cocaine and alcohol abuse can also cause the disease.
- Nutrition and hormones. Nutritional deficiencies such as a lack of vitamin B1 or potassium, and hormonal imbalances caused by metabolic diseases such as diabetes and thyroid problems can also lead to dilated cardiomyopathy.
- Other diseases. About 8% of patients with HIV develop dilated cardiomyopathy. A family history of dilated cardiomyopathy, suggesting a genetic cause, occurs in up to 30% of cases of this disease.
Genes seem to be responsible for the heart thickening of hypertrophic cardiomyopathy. An abnormal gene may be inherited from a parent, or a normal gene may mutate later in life. Researchers have identified at least four genes that may be involved in hypertrophic cardiomyopathy.
Restrictive cardiomyopathy is usually caused by one of three rare conditions.
- Amyloidosis causes abnormal protein fibers to accumulate in the heart muscle.
- Sarcoidosis produces lumps (called granulomas) in organs, including the heart.
- Hemochromotosis is a genetic condition that causes iron to build up in the heart and other parts of the body.
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