The main feature of Hypertrophic Cardiomyopathy is an excessive thickening of the heart muscle. Heart muscle may thicken in normal individuals as a result of high blood pressure or prolonged athletic training. In Hypertrophic Cardiomyopathy (HCM), however, the muscle thickening occurs without an obvious cause. The condition has been known by a number of other names including "hypertrophic obstructive cardiomyopathy" (HOCM), "idiopathic hypertrophic sub-aortic stenosis" (IHSS) and "muscular sub-aortic stenosis" The general term "hypertrophic cardiomyopathy" is now the most widely used and recommended. Cardiomyopathy differs from many of the other disorders of the heart in several ways, including the following:
- Cardiomyopathy can, and often does, occur in the young.
- The condition is fairly uncommon, affecting only about 50,000 Americans (adults and children).
- Cardiomyopathy is a leading cause for heart transplantation.
- The condition tends to be progressive and sometimes worsens fairly quickly.
- It may be associated with diseases involving other organs, as well as the heart.