In dilated cardiomyopathy, the chambers of the heart are large and the heart won't pump blood effectively. In hypertrophic cardiomyopathy, the heart muscle thickens, reducing the size of the left heart ventricle. The ventricles can't expand well and fill with enough blood. In restrictive cardiomyopathy, the inside of the ventricle walls become stiff and unable to expand. Again, enough blood cannot fill the ventricles.
Restrictive cardiomyopathies are the least common of the cardiomyopathies in the western world.
Several diseases may cause the ventricle walls to become rigid, although many times the cause is unknown. Dilated cardiomyopathy may be caused by alcohol or infections. Other conditions associated with it include high blood pressure, pregnancy, and cigarette smoking. Dilated cardiomyopathy is generally found in middle-aged people, more commonly men. However, the tendency to develop this disease is inherited in over half the cases.