Hypertrophic Cardiomyopathy (HCM)

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What is Hypertrophic Cardiomyopathy?

Hypertrophic cardiomyopathy is most often caused by abnormal genes in the heart muscle. These genes cause the walls of the heart chamber (left ventricle) to contract harder and become thicker than normal. 

The thickened walls become stiff. This reduces the amount of blood taken in and pumped out to the body with each heartbeat.

Diagram showing normal heart and one with HCM

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Obstructive and Nonobstructive HCM

In obstructive HCM, the wall (septum) between the two bottom chambers of the heart thickens. The walls of the pumping chamber can also become stiff. It may block or reduce the blood flow from the left ventricle to the aorta. Most people with HCM have this type.

In nonobstructive HCM, the heart’s main pumping chamber still becomes stiff. This limits how much blood the ventricle can take in and pump out, but blood flow is not blocked. 

Signs, Symptoms and Risks

Some people with hypertrophic cardiomyopathy don’t have symptoms. Others may not have signs or symptoms in the early stages of the disease but may develop them over time. 

Knowing the signs and symptoms of HCM is important. It can help with getting an early diagnosis, when treatment may be most effective.

Signs and symptoms of HCM include:

  • Chest pain, especially with physical exertion
  • Shortness of breath, especially with physical exertion
  • Fatigue
  • Arrhythmias (abnormal heart rhythms)
  • Dizziness
  • Lightheadedness
  • Fainting (syncope)
  • Swelling in the ankles, feet, legs, abdomen and veins in the neck

HCM is a chronic disease that can get worse over time. This can lead to poorer function and quality of life, long-term complications and more financial and social burden. 

People with HCM often need to make lifestyle changes, such as limiting their activity, to adjust for their disease.  

As HCM progresses, it can cause other health problems. People with HCM are at higher risk for developing atrial fibrillation, which can lead to blood clots, stroke and other heart-related complications. HCM may also lead to heart failure. It can also lead to sudden cardiac arrest, but this is rare. 

HCM has been cited as the most common reason for sudden cardiac death in young people and athletes under the age of 35.

Getting a Diagnosis 

Hypertrophic cardiomyopathy is most often inherited. HCM is the most common form of genetic heart disease. It can happen at any age, but most receive a diagnosis in middle age. 

It’s estimated that 1 in every 500 people have HCM, but a large percentage of patients are undiagnosed. Of those diagnosed, two-thirds have obstructive HCM and one-third have non-obstructive HCM.

A cardiologist or pediatric cardiologist often diagnoses and treats HCM. You may also be referred to a cardiomyopathy center where the health care team has specialized training.

HCM is diagnosed based on your medical history, family history, a physical exam and diagnostic test results.  

Medical and Family Histories

Knowing your medical history and any signs and symptoms you may have is an important first step. Your physician will also want to know if anyone in your family has been diagnosed with HCM, heart failure or cardiac arrest.

Physical Exam

Your heart and lungs will be checked. Your physician will listen for certain sounds with a stethoscope. For example, the loudness, timing and location of a heart murmur may suggest obstructive HCM. 

Diagnostic Tests

Diagnosis is typically done by echocardiogram. It checks the thickness of the heart muscle and blood flow from the heart. In some cases, another type of echocardiogram, transesophageal echo (or TEE), may be performed. A TEE is done using a probe inserted in the throat while the patient is under sedation.

Other diagnostic tests may include:

Diagnostic Procedures

Confirming diagnosis or preparing for surgery may also involve one or more medical procedures including:

Treatment and Management of HCM

There are currently no disease-specific medications for hypertrophic cardiomyopathy.  

For people with HCM who don’t have symptoms, lifestyle changes and medications for conditions that may contribute to cardiovascular disease are recommended.

For those with symptoms, the focus is on symptom management using medications and procedures.


Medications called beta-blockers, calcium channel blockers and diuretics offer limited and varying relief of symptoms. They may help with function but may also have adverse side effects. 


A range of surgical and nonsurgical procedures can be used to treat HCM:

  • Septal myectomy – Septal myectomy is open-heart surgery. It’s considered for people with obstructive HCM and severe symptoms. This surgery is generally reserved for younger patients and for people whose medications aren’t working well. A surgeon removes part of the thickened septum that’s bulging into the left ventricle. This improves blood flow within the heart and out to the body.

  • Alcohol septal ablation (nonsurgical procedure) – In this procedure, ethanol (a type of alcohol) is injected through a tube into the small artery that supplies blood to the area of heart muscle thickened by HCM. The alcohol causes these cells to die. The thickened tissue shrinks to a more normal size. The risks and complications of heart surgery increase with age. For this reason, ablation may be preferred to myectomy in older patients with other medical conditions.

  • Surgically implanted devices – Surgeons can implant several types of devices to help the heart work better, including:
    • Implantable cardioverter defibrillator (ICD) – An ICD helps maintain a normal heartbeat by sending an electric shock to the heart if an irregular heartbeat is detected. This reduces the risk of sudden cardiac death.
    • Pacemaker – This small device uses electrical pulses to prompt the heart to beat at a normal rate.
    • Cardiac resynchronization therapy (CRT) device – This device coordinates contractions between the heart’s left and right ventricles.
  • Heart transplant – In HCM patients with advanced, end-stage disease, a heart transplant may be considered. In this procedure, a person’s diseased heart is replaced with a healthy donor heart.

Other types of cardiomyopathy:

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HCM for Professionals

It is estimated that 1 in every 500 adults living in the U.S. have hypertrophic cardiomyopathy (HCM), but a large percentage of patients are undiagnosed. Which of your patients is undiagnosed?

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Hypertrophic Cardiomyopathy Podcast Series

Hear from medical experts and patients living with HCM in our podcast series.


Bristol Myers Squibb is proud to support the American Heart Association.

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The Hypertrophic Cardiomyopathy Association participates in the American Heart Association’s Hypertrophic Cardiomyopathy initiative to improve HCM awareness and care.

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