Hypertrophic cardiomyopathy (HCM) is a thickening of the heart muscle. It can lead to a stiffening of the walls of the heart and to problems with the heart valves, both of which hinder blood flow out of the heart. HCM can run in families, develop with age, or arise from high blood pressure or unknown causes. Many people with HCM experience no symptoms. For others, symptoms may worsen as heart function worsens. These symptoms include chest pain or pressure (either with activity or at rest), shortness of breath, fatigue, fainting, palpitations, even Sudden Cardiac Death.