Cardiomyopathy refers to diseases of the heart muscle. These diseases have numerous causes, signs and symptoms, and treatments. In cardiomyopathy, the heart muscle becomes inflated, broad, or inflexible. In uncommon cases, the muscle tissue in the heart is replaced with scar tissue. As cardiomyopathy worsens, the heart becomes weaker. It is less able to pump blood through the body and maintain a normal electrical rhythm.