Dilated cardiomyopathy is the most common type of the disease. It mostly occurs in adults aged 20 to 60. Men are more likely than women to have this type of cardiomyopathy.
Dilated cardiomyopathy affects the heart's ventricles (VEN-trih-kuls) and atria (AY-tree-uh). These are the lower and upper chambers of the heart, respectively.
The disease often starts in the left ventricle, the heart's main pumping chamber. The heart muscle begins to dilate (stretch and become thinner). This causes the inside of the chamber to enlarge. The problem often spreads to the right ventricle and then to the atria as the disease gets worse.
When the heart chambers dilate, the heart muscle doesn't contract normally. Also, the heart can't pump blood very well. Over time, the heart becomes weaker and heart failure can occur.
Common symptoms of heart failure include shortness of breath, fatigue (tiredness), and swelling of the ankles, feet, legs, abdomen, and veins in the neck.
Hypertrophic cardiomyopathy (HCM) is very common and can affect people of any age. About 1 out of every 500 people has HCM. It affects men and women equally.
HCM is a common cause of sudden cardiac arrest (SCA) in young people, including young athletes.
HCM occurs if heart muscle cells enlarge and cause the walls of the ventricles (usually the left ventricle) to thicken. Despite this thickening, the ventricle size often remains normal. However, the thickening may block blood flow out of the ventricle. If this happens, the condition is called obstructive hypertrophic cardiomyopathy.
Sometimes, the septum thickens and bulges into the left ventricle. This also can block blood flow out of the left ventricle. (The septum is the wall that divides the left and right sides of the heart.)
If a blockage occurs, the ventricle must work hard to pump blood to the body. Symptoms can include chest pain, dizziness, shortness of breath, or fainting.
HCM also can affect the heart's mitral (MI-trul) valve, causing blood to leak backward through the valve.
Sometimes the thickened heart muscle doesn't block blood flow out of the left ventricle. This is called nonobstructive hypertrophic cardiomyopathy. The entire ventricle may thicken, or the thickening may happen only at the bottom of the heart. The right ventricle also may be affected.
In both types of HCM (obstructive and nonobstructive), the thickened muscle makes the inside of the left ventricle smaller, so it holds less blood. The walls of the ventricle also may stiffen. As a result, the ventricle is less able to relax and fill with blood.
These changes can raise blood pressure in the ventricles and the blood vessels of the lungs. Changes also occur to the cells in the damaged heart muscle. This may disrupt the heart's electrical signals and lead to arrhythmias.
Some people who have HCM have no signs or symptoms. The disease doesn't affect their lives. Others have severe symptoms and complications. For example, they may have shortness of breath, serious arrhythmias, or an inability to exercise.
Rarely, people who have HCM can have SCA during very vigorous physical activity. The physical activity can trigger dangerous arrhythmias. If you have HCM, ask your doctor what types and amounts of physical activity are safe for you.
Restrictive cardiomyopathy tends to mostly affect older adults. With this disease, the ventricles become stiff and rigid. This happens because abnormal tissue, such as scar tissue, replaces the normal heart muscle.
As a result, the ventricles can't relax normally and fill with blood, and the atria become enlarged. Over time, blood flow in the heart is reduced. This can lead to problems such as heart failure or arrhythmias.
Arrhythmogenic right ventricular dysplasia (ARVD) is a rare type of cardiomyopathy. ARVD occurs if the muscle tissue in the right ventricle dies and is replaced with scar tissue.
This process disrupts the heart's electrical signals and causes arrhythmias. Symptoms include palpitations and fainting after physical activity. (Palpitations are feelings that your heart is skipping a beat, fluttering, or beating too hard or too fast.)
ARVD usually affects teens or young adults. It can cause SCA in young athletes.
The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.