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Hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a heart muscle disease. Find out about its causes, symptoms and treatments, and hear from people living with HCM.

Hypertrophic cardiomyopathy (HCM) is part of a group of diseases that affect the heart muscle. The general term for these diseases is cardiomyopathy.

HCM affects around 1 in 200 people of any age or gender. Many people with the condition have no symptoms.

HCM can lead to other heart conditions, such as heart failure and heart arrhythmias. In very rare cases, mostly associated with vigorous physical activity, it can cause a cardiac arrest. Part of your assessment when you’re diagnosed with HCM is to see if you’re at high risk of cardiac arrest.

How does HCM affect the heart?

In a normal heart, the cells that make up the heart muscle (myocardium) lie flat in smooth, straight layers.

When you have HCM, these cells become disorganised and form uneven layers. This causes the muscle of your heart to thicken and become stiffer. It can also scar the heart muscle. This stiffness and scarring can stop your heart from pumping properly and lead to rhythm disorders.

HCM usually affects the walls of the lower left chamber of the heart (the left ventricle). The thickened muscle makes the inside of the left ventricle smaller, which means it can’t hold as much blood. This means less oxygen-rich blood is pumped around the body.

Normal heart and heart with hypertrophic cardiomyopathy showing the left ventricle smaller and the heart muscle (myocardium) thickened around it

Most people with HCM have normal coronary arteries and valves. However the condition sometimes affects the mitral valve, causing blood to leak backwards through it. This also reduces the heart’s ability to pump effectively.

Changes can also occur in the damaged heart muscle that may trigger problems with the heart's electrical signals, causing an irregular heart beat (arrhythmia).

Find out how the heart works

Obstructive or non-obstructive hypertrophic cardiomyopathy?

In around one in four people with HCM, the thickening of the heart muscle causes an obstruction which reduces the blood flow from the heart to the body. This is called hypertrophic obstructive cardiomyopathy (HOCM).

If you have HOCM, you’re more likely to experience chest pain, breathlessness, and fainting. You’re also more likely to develop arrhythmias, particularly atrial fibrillation.

People without this obstruction may sometimes have their condition referred to as hypertrophic non-obstructive cardiomyopathy (HNCM). Sometimes HNCM will go on to become HOCM.

Causes and risk factors for hypertrophic cardiomyopathy

HCM is an inherited condition (a condition that is passed on through families).

There’s a 50% (one in two) chance that the children of a parent with hypertrophic cardiomyopathy will also have inherited the risk of developing the disease. If you have HCM, your first-degree relatives (parents, brothers, sisters or children) may want to consider screening for the condition.

Symptoms of HCM

Some people with HCM have no symptoms and their condition may go undiagnosed for a long time. Usually the condition is picked up in adolescence or adulthood.

In other people HCM causes a number of symptoms, the most common of which are:

  • breathlessness
  • chest pain
  • rapid or irregular heartbeats (palpitations)
  • light-headedness and/or fainting.

Hypertrophic cardiomyopathy complications

Because of the changes to the heart’s structure, HCM can lead to a number of other heart conditions. You may hear these referred to as ‘complications’ of your hypertrophic cardiomyopathy. These complications include:

How is HCM diagnosed?

In many cases HCM is picked up as a heart murmur at routine check-ups, or as a result of screening for another condition.

To confirm a diagnosis, you’re likely to have one or more of the following tests:

  • Electrocardiograph (ECG) to record the electrical activity of your heart.
  • Echocardiogram (echo test) (PDF) a soundwave test to review the structure, including wall thickness, and working of your heart.
  • Exercise tolerance test (ETT) (PDF) a type of ECG carried out while you’re exercising on a treadmill.
  • Holter monitor test, (PDF) to measure your heart rhythm over a 24-48 hour period.
  • Magnetic Resonance Imaging (MRI), a non-invasive test that uses strong magnetic fields and radio frequency to create detailed images of your heart. People with pacemakers or implantable cardiac defibrillators may not be able to undergo this test.

Screening for HCM

If you have HCM, it’s important to talk to your doctor about further screening for your children and other first degree relatives (brothers, sisters and parents). This screening will include an ECG and/or echocardiography.

Some people may be referred for genetic testing, which involves a simple blood test that is sent away to a laboratory for DNA testing. Genetic testing for HCM may be useful for family screening, but should be done with pre-testing advice and within a specialised cardiac genetics service, such as the Cardiac Inherited Disease Group.

Treatments for hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy can’t be cured, but treatments can help reduce your symptoms and lower your risk of complications such as atrial fibrillation or heart failure. There are a range of medications and procedures available. Your doctor will discuss your options with you.

HCM medication

Medication is often prescribed to reduce the amount of work your heart has to do and to relieve your symptoms. Common HCM medications include:

  • beta blockers. A group of medications that slow your heart rate and lower your blood pressure. Common types of beta blocker include: bisoprolol and metoprolol.
  • calcium channel blockers. These medications are also used to lower your blood pressure and slow your heart rate but work in a different way to beta blockers. Common examples include: verapamil, diltiazem, amlodipine and felodipine.
  • anti-arrhythmics. This group of medications is used to prevent irregular heart rhythms. Common types of anti-arrhythmics include amiodarone, sotolol and flecainide.

If you think your medication is causing side-effects, talk to your doctor or pharmacist as soon as possible. Never stop taking your medication without talking to your doctor first.

Read more about heart medications

HCM procedures

People who continue to experience lots of symptoms even on medication, or are at risk of a life-threatening heart rhythm problem, may also need one of the following:

A pacemaker. This is a small device which corrects your heart rate and rhythm. It’s inserted under the skin, during a short hospital procedure using local anaesthetic and sedation.

An implantable cardioverter defibrillator (ICD). This is a small device which helps control your heart rhythm and restarts your heart automatically if it stops. It’s inserted under the skin, during a short hospital procedure using local anaesthetic and sedation.

A septal ablation (sometimes called alcohol septal ablation). This is a non-surgical procedure that reduces symptoms by destroying part of the thickened muscle wall. It’s a short procedure carried out in hospital using a local anaesthetic and sedation to make you comfortable. Doctors insert alcohol into the area via a long thin tube (catheter). The alcohol causes the thickened area to shrink and die.

A septal myectomy (surgical myectomy). This is a type of open-heart surgery carried out under general anaesthetic. During the procedure the medical team removes part of the thickened heart muscle. This should improve blood flow, relieve symptoms and reduce problems with your heart valve.

Living with HCM

If you’ve recently been diagnosed with hypertrophic cardiomyopathy, you may feel worried about how it will affect you and your family/whānau.

With proper treatment and regular cardiology appointments, you can continue to live a normal life. However you may need to make some adjustments to your lifestyle.


Most people will be able to continue their work without a problem, however if you have a physically strenuous job you may need to discuss this with your doctor and your employer. You should also talk to your doctor if you’re required to drive for work (hold a vocational licence).


The majority of people with hypertrophic cardiomyopathy will be able to drive, however there’s sometimes a stand down period for people who have experienced significant symptoms such as fainting. Talk to your doctor about this.

Exercise and hypertrophic cardiomyopathy

It’s important to talk to your cardiologist about exercise that’s safe for you. Because there’s a risk of sudden cardiac death in people with hypertrophic cardiomyopathy, competitive sports and very intense athletic training are usually not recommended.

However, low to moderate intensity, non-competitive forms of exercise are recommended for most people. Exercise is important for your mental health and well-being and will also reduce your risk of other kinds of heart disease.

If you experience any of the following symptoms during exercise, it’s important to stop and seek advice from your doctor:

  • Chest pain
  • Dizziness
  • Severe shortness of breath
  • Sudden heart palpitations (very rapidly beating heart)
  • Taking an unusually long time to recover from exercise
  • Worsening of existing HCM symptoms

Diet and drinking

Being overweight puts extra strain on your heart so it’s important to follow heart healthy eating guidelines. You can find out more about this in our booklet Eating for a healthy heart. Sometimes you may be recommended to limit how much alcohol you drink.

Ask your doctor for advice about food and alcohol specific to you.

Sex and HCM

Sex is safe for people living with HCM. As with any kind of exercise, it’s important to listen to your body and to stop if you experience any warning signs during such as:

  • Chest pain
  • Dizziness
  • Severe shortness of breath
  • Sudden heart palpitations (very rapidly beating heart)

Sometimes your HCM symptoms or the medication you’ve been prescribed may have an impact on your sex life. If this is the case, talk to your doctor. Never stop taking your medication without talking to your doctor first. It’s also important to talk to your doctor before taking any kind of medication or alternative therapies designed to improve your sex life.

Hear from others living with hypertrophic cardiomyopathy

Sometimes it’s helpful to hear from others living with the same condition. Our Journeys programme offers people the chance to hear from others living with heart conditions and to share their own story.

What's it like to live with cardiomyopathy?

Other types of cardiomyopathy