Hypertrophic cardiomyopathy is a primary disease of the myocardium (muscle of the heart), in which a portion of the myocardium is hypertrophied (thickened) without any obvious cause, creating functional impairment of the cardiac muscle. It is a leading cause of sudden cardiac death in young athletes. The occurrence of hypertrophic cardiomyopathy is a significant cause of sudden unexpected cardiac death in any age group and as a cause of disabling cardiac Sx. Younger patients are likely to have a more severe form of hypertrophic cardiomyopathy.