As American Heart Health Awareness Month comes to a close, think about preventing sudden cardiac death in children and young adults. One of the most common causes of sudden cardiac death is hypertrophic cardiomyopathy (HCM). HCM is a genetic disease in which the heart muscle becomes abnormally thick, making it harder to pump blood throughout the body. Most people have few, if any, symptoms of this disease. Some people experience shortness of breath when exercising, chest pain, fainting, dizziness, fatigue, or abnormal heart rhythms (arrhythmias).