There are two common types of HCM:

  • Obstructive hypertrophic cardiomyopathy – when the wall between the two bottom chambers of the heart (the left and right ventricle) become thickened, it blocks blood from flowing freely from the heart out into the body. Because the blood flow is blocked, or obstructed, it is called obstructive HCM.
  • Nonobstructive hypertrophic cardiomyopathy – when the left ventricle itself becomes thickened and stiff as a result of HCM, it can make it harder for the ventricle to fill with enough blood to pump out. Although the blood flow is not obstructed directly, the result is the same – not enough blood is going out with each heartbeat.

Hypertrophic Cardiomyopathy Causes

Hypertrophic cardiomyopathy is an inheritable disease. For those who have HCM, cardiogenetic testing can confirm the diagnosis in 60-70 percent of cases.

There is a 50 percent chance that a parent with HCM will pass it down to their children. That means that if one of your parents has a genetic mutation associated with HCM, there is a 50-50 chance that you will have the mutation as well. We recommend genetic screening for parents, siblings, and children of anyone diagnosed with HCM.

Genetic screening and counseling are key parts of the University of Maryland Heart and Vascular Center’s Hypertrophic Cardiomyopathy Program. Our cardiogenetics specialists work with families affected by HCM to determine who else might be at risk of developing HCM, and make a plan to prevent cardiac emergencies.

Hypertrophic Cardiomyopathy Symptoms

In many cases, people with hypertrophic cardiomyopathy have no symptoms. As a result, many people with this condition don’t know they have it. When symptoms do occur, they can include:

  • Shortness of breath, especially during exercise
  • Chest pain
  • Fatigue
  • Light-headedness
  • Sensation of heart racing (palpitations)
  • Fainting (syncope)
  • Sudden cardiac death

If you or a member of your family is experiencing one or more of these symptoms, it’s time to schedule an appointment with your doctor for an evaluation.

While many people who have HCM may lead normal lives with no problems, in other cases HCM can cause problems. These can include:

  • Heart failure: HCM can make it harder for the heart to fill with blood and pump it out efficiently. When the heart is not able to pump blood well enough to meet the body’s needs, it’s called heart failure.
  • Mitral valve disease: Sometimes, the thickened heart muscle may affect the heart’s mitral valve, pulling it out of shape and making it difficult for the heart valve to close. This can cause a leaky valve and lead to heart failure symptoms.
  • Heart rhythm problems (arrhythmias) and sudden cardiac death: Hypertrophic cardiomyopathy often causes problems with the heart’s rhythm, including atrial fibrillation and ventricular tachycardia, which can lead to sudden cardiac death. This is more common in people under 30. Untreated HCM is one of the more common causes of death among young athletes.
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