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Dilated cardiomyopathy is the most common form of cardiomyopathy. It generally occurs in adults aged 20 to 60 years. Men are more likely than women to develop dilated cardiomyopathy.
Dilated cardiomyopathy affects the heart's ventricles (VEN-trih-kuls) and atria. The ventricles are the two lower chambers of the heart, and the atria are the two upper chambers. Dilated cardiomyopathy usually starts in the left ventricle, where the heart muscle begins to dilate or stretch and become thinner. This leads to enlargement of the inside of the ventricle. The problem often spreads to the right ventricle and then to the atria as the disease gets worse.
When the chambers dilate, the heart can't pump blood very well. The heart tries to cope by dilating the chambers even more. Over time, the heart becomes weaker and heart failure can occur. Symptoms of heart failure include feeling tired, swelling of the legs and feet, and shortness of breath. Dilated cardiomyopathy also can lead to heart valve problems, arrhythmias, and blood clots in the heart. Having advanced dilated cardiomyopathy is a common reason for needing a heart transplant.
Up to one-half of all cases of dilated cardiomyopathy may be hereditary (passed down in the genes from parent to child). These cases are called familial dilated cardiomyopathy. Dilated cardiomyopathy also can be a complication of many conditions, including coronary artery disease and high blood pressure. It also can be caused by viral infections, excessive use of alcohol, and exposure to certain drugs (including cocaine, amphetamines, and some drugs used in cancer treatments). In some cases, no cause can be found.
Hypertrophic cardiomyopathy occurs when the heart muscle thickens abnormally. The thickening generally happens in the left ventricle, the heart's main pumping chamber. This type of cardiomyopathy can affect people of any age.
Hypertrophic cardiomyopathy can be obstructive or nonobstructive. In the obstructive type, the septum (the wall that divides the left and right sides of the heart) thickens and bulges into the left ventricle. This bulge blocks the flow of blood out of the ventricle. The ventricle must work much harder to pump blood past the blockage and out to the body. Symptoms can include chest pain, dizziness, shortness of breath, or fainting.
Obstructive hypertrophic cardiomyopathy also can affect the heart's mitral (MI-trul) valve, causing blood to leak backward through the valve.
In nonobstructive hypertrophic cardiomyopathy, the thickened heart muscle does not block the flow of blood out of the ventricle. The entire ventricle may become thicker (symmetric ventricular hypotrophy) or it may happen only at the bottom of the heart (apical hypertrophy). The right ventricle also may be affected.
In both kinds of hypertrophic cardiomyopathy, the thickened muscle makes the inside of the left ventricle smaller so that it holds less blood. The walls of the ventricles also may become stiff. As a result, they are less able to relax and fill with blood. This causes increased pressure in the ventricles and the blood vessels of the lungs. Changes also occur to the cells in the damaged heart muscle. This may interfere with the heart's electrical signals, leading to arrhythmias.
Some people with hypertrophic cardiomyopathy have no symptoms, and the condition does not affect their lives. Others have severe symptoms or develop complications such as serious arrhythmias. A few people with the condition have sudden cardiac arrest because of dangerous arrhythmias.
Hypertrophic cardiomyopathy can be inherited because of a gene mutation or develop over time because of high blood pressure or aging. Often, the cause is unknown.
Restrictive cardiomyopathy tends to mostly affect older adults. In this cardiomyopathy, the ventricles become stiff and rigid due to replacement of the normal heart muscle with abnormal tissue, such as scar tissue. As a result, the ventricles cannot relax normally and expand to fill with blood, which causes the atria to become enlarged. Eventually, blood flow in the heart is reduced, and complications such as heart failure or arrhythmias occur.
Restrictive cardiomyopathy can occur for no known reason, or it can develop because the person has another disease. Some of the diseases that can cause restrictive cardiomyopathy include hemochromatosis, sarcoidosis, amyloidosis, and connective tissue disorders. Restrictive cardiomyopathy also can occur as a result of radiation treatments, infections, or scarring after surgery.
Arrhythmogenic right ventricular dysplasia (ARVD) is a rare type of cardiomyopathy. ARVD develops when the muscle tissue in the right ventricle dies and is replaced with scar tissue. This process causes problems in the heart's electrical signaling, resulting in arrhythmias. Symptoms include a feeling of strong or irregular heartbeats (palpitations) and fainting after exercise.
ARVD usually develops in teens or young adults and is often the cause of sudden cardiac death in young athletes. ARVD is thought to be an inherited disease.
Author/Source: National Heart, Lung & Blood Institute, Division of the National Institutes of Health [NIH]
Retrieved: June 2008