Hypertrophic Cardiomyopathy (HCM)

What is HCM?

Hypertrophic Cardiomyopathy (HCM) is a complex disorder of the heart which can affect individuals of all ages. It is characterized by a thickening of the septum (the heart's dividing muscular wall), stiffening of the left ventricle (the heart's main pumping chamber), mitral valve changes and cellular changes.

Two types of HCM (From the National Institute of Health)

Obstructive HCM

In obstructive HCM, the septum (the wall dividing the heart's left and right sides) thickens and bulges into the left ventricle, obstructing blood flow.  The ventricle must work much harder to pump blood past the blockage and out to the body. It can also affect the heart's mitral valve, causing the blood to leak backward through the valve.

Non-Obstructive HCM

In non-obstructive HCM, the thickened heart muscle does not block the blood flow out of the ventricle.  The entire ventricle may become thicker (symmetric ventricular hypotrophy) or it may only happen at the bottom of the heart (apical hypertrophy).  The right ventricle may also be affected.

In both kinds of HCM, the thickened muscle reduces the inside of the left ventricle so that it holds less blood.  The left ventricle may become stiff, and as a result, less able to relax and fill with blood.  This causes increased pressure in the ventricles and blood vessels of the lungs. Changes also occur to the cells in the damaged heart muscle possibly causing an interference with the heart's electrical signals, leading to arrhythmias.

Causes and Risks

  • HCM may be inherited. It can be passed down through an abnormal gene.  
  • Adults have a 50/50 chance of giving this gene to their children. 
  • HCM may develop due to high blood pressure or aging.
  • In other cases of HCM, the cause may simply be unknown.
  • Younger people are more likely to have a severe form of HCM.
  • People with a family member that has died from sudden cardiac death are at higher risk.

How often does HCM occur?

  • HCM affects 600,000 to 1.5 million people in the U.S. (1 in 500)
  • 100,000 young athletes die each year from all cardiovascular disorders, including HCM, which is often but not always a result from sports. (According to the Center for Disease Control in Atlanta)
  • The number of deaths related to sudden cardiac death is double the number of auto accidents
  • HCM is more common than multiple sclerosis, affecting 1 in 700

Symptoms & Warnings

Unfortunately, when sudden death strikes as a result of HCM, there are usually NO SYMPTOMS! However, many people with HCM may have only minor symptoms and live a normal life with proper medical treatment.  Others can develop symptoms at any age as the condition of the heart grows worse. Symptoms may include: 

  • Chest pain or pressure with an increase of physical activity 
  • Chest pain or pressure at rest or after meals 
  • Fatigue or shortness of breath due to exertion
  • Fainting (syncope) affects people with HCM 15 to 25 percent of the time
  • Palpitations due to abnormal heart rhythms
  • Sudden death

What else do we screen for?  Learn more.