What is Hypertrophic Cardiomyopathy (HCM)?

What is Hypertrophic Cardiomyopathy (HCM)?

Hypertrophic cardiomyopathy (HCM) is the most common type of heart disease. This condition causes the heart muscle to thicken, making it difficult for the heart to circulate blood. Hypertrophic cardiomyopathy is a genetic condition that may go undiagnosed for years. For this reason, HCM is considered an autosomal dominant condition, meaning a person has a 50% chance of inheriting or passing it down to their children. It affects about one in 500 people and could present itself at any time during a person's life.

Hypertrophic cardiomyopathy displays few symptoms for many people; others experience shortness of breath, chest pain, heart palpitations, or even a fatal heart attack. Hypertrophic cardiomyopathy typically involves the thickening of the heart's left ventricle, although it could also affect the right ventricle.

Types of Hypertrophic Cardiomyopathy


There are two types of hypertrophic cardiomyopathy:

  • Hypertrophic obstructive cardiomyopathy (HOCM). The most common type of HCM, causes the heart muscle and walls of the heart to thicken, which blocks the blood from leaving the heart. Hypertrophic obstructive cardiomyopathy can also affect the bottom of the heart, called the apex.
  • Non-obstructive hypertrophic cardiomyopathy (HNCM). A less common form of hypertrophic cardiomyopathy, where the heart muscle thickens but not enough to block the blood flowing out of the heart.

Signs and Symptoms of Hypertrophic Cardiomyopathy


Hypertrophic cardiomyopathy is sometimes referred to as a hidden disease because in some people, the condition may remain symptomless for years. Hypertrophic cardiomyopathy symptoms mimic those of conditions such as asthma, anxiety, hypertension, or coronary artery disease.

Common hypertrophic cardiomyopathy symptoms include:

  • Chest pain, worsening with activity
  • Shortness of breath, especially when physically active
  • Fatigue
  • Heart palpitations or fluttering (arrhythmias)
  • Dizziness or feeling lightheaded
  • Fainting
  • Swelling of the legs, ankles, feet, and abdomen.

What Causes Hypertrophic Cardiomyopathy?


Hypertrophic cardiomyopathy is an inherited condition. In cases of obstructive hypertrophic cardiomyopathy, the heart muscle wall (septum) begins to thicken between the ventricles located at the bottom of the heart. This thickening can eventually stop the flow of blood from exiting the heart.

When blood flow is not blocked from exiting the heart, the heart's left ventricle (the pumping chamber) might begin to stiffen. This makes the heart work harder since it cannot relax the muscle, making it difficult for the heart to circulate enough blood through the body.

Some forms of hypertrophic cardiomyopathy involve the abnormal structure of the heart muscle. In addition, people with this condition often have electrical conduction problems with the wiring of their hearts. HCM can also change the heart muscle cells (myofiber disarray), which may prompt arrhythmias.



People can live normal lives without complications from hypertrophic cardiomyopathy. However, there are several related complications, which may include:  

  • Cardiac arrest - as the left ventricle wall of the heart thickens, it becomes more difficult for the heart to pump blood, which may bring on sudden cardiac death (SCD).
  • Heart failure - when the weakened heart muscle becomes too thick, the ventricle may become enlarged, diminishing the force of blood flowing from the heart. The heart could fill with blood which may lead to congestive heart failure. This condition is more common among people with uncontrolled high blood pressure.
  • Atrial fibrillation - an irregular heartbeat that affects the heart's ability to pump blood normally..
  • Blood clots - occur when blood cells form into a mass and travel through the bloodstream, causing a stroke or heart attack
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Trust NewYork-Presbyterian for Hypertrophic Cardiomyopathy Care

NewYork-Presbyterian cardiologists and cardiac surgeons are world leaders in heart care and treat hypertrophic cardiomyopathy patients of all ages.

NewYork-Presbyterian provides a full range of cardiovascular care services by leading heart specialists. Learn more about available treatment options at one of our cardiovascular care centers located throughout the New York City metropolitan area, including Westchester and Hudson Valley.