Cardiomyopathy is a general term for diseases of the heart muscle, where the walls of the heart chambers have become stretched, thickened or stiff. This affects the heart's ability to pump blood around the body.

The abnormal heart muscle seen in cardiomyopathy is not caused by blocked arteries in the heart (coronary artery disease), high blood pressure (hypertension), disease of the heart valves (valvular disease) or congenital heart disease.

Most types of cardiomyopathy are inherited and are seen in children and younger people.

Dilated cardiomyopathy

In dilated cardiomyopathy the muscle walls of the heart become stretched and thin, so they cannot contract (squeeze) properly to pump blood around the body.

How serious is it?

If you have dilated cardiomyopathy, you're at greater risk of heart failure, where the heart fails to pump enough blood around the body at the right pressure.

Heart failure typically causes shortness of breath, extreme tiredness and ankle swelling.

There's also a risk of heart valve problems, an irregular heartbeat and blood clots. You'll need to have regular appointments with a GP so the disease can be monitored.

Who's affected?

Dilated cardiomyopathy can affect both children and adults.

The following can all play a role in the condition:

  • inheriting a changed (mutated) gene that makes you more vulnerable to the condition
  • an underlying medical condition
  • uncontrolled high blood pressure
  • an unhealthy lifestyle, such as a lack of vitamins and minerals in your diet, drinking too much alcohol and using recreational drugs
  • a viral infection that causes inflammation of the heart muscle 
  • a heart valve problem
  • a disease of the tissues or vessels – such as granulomatosis with polyangiitis (GPA), sarcoidosis, amyloidosis, lupus, polyarteritis nodosa, vasculitis or muscular dystrophy
  • pregnancy – cardiomyopathy can sometimes develop as a complication of pregnancy

But for many people, the cause is unknown.

More information

Read the British Heart Foundation and Cardiomyopathy UK's booklet on living with dilated cardiomyopathy.

Hypertrophic cardiomyopathy

In hypertrophic cardiomyopathy, the heart muscle cells have enlarged and the walls of the heart chambers thicken.

The heart chambers are reduced in size so they can't hold much blood, and the walls can't relax properly and may stiffen. Also, the flow of blood through the heart may be obstructed.

How serious is it?

In most cases, hypertrophic cardiomyopathy will not have an impact on daily life. Some people do not have any symptoms and do not need treatment.

But that does not mean the condition cannot be serious. Hypertrophic cardiomyopathy is the most common cause of sudden unexpected death in childhood and in young athletes.

The main heart chambers can become stiff, leading to back pressure on the smaller collecting chambers. This can sometimes worsen the symptoms of heart failure and lead to abnormal heart rhythms (atrial fibrillation).

Blood flow from the heart may become reduced or restricted (called obstructive hypertrophic cardiomyopathy).

Also, the mitral heart valve can become leaky, causing blood to leak backwards. Find out more about mitral regurgitation.

You'll also be at greater risk of developing a heart infection (endocarditis).

These heart changes can cause dizziness, chest pain, shortness of breath and temporary loss of consciousness.

If you have severe hypertrophic cardiomyopathy, you'll need to see your doctor regularly so your condition can be monitored.

Your doctor will advise about the level and amount of exercise you can do and sensible lifestyle changes you can make.

Who's affected?

Hypertrophic cardiomyopathy is thought to affect 1 in 500 people in the UK. Most people inherit the disease from their parents.

More information

Read the British Heart Foundation and Cardiomyopathy UK booklet on living with hypertrophic cardiomyopathy.

Restrictive cardiomyopathy

Restrictive cardiomyopathy is rare. It's most often diagnosed in children, although it can develop at any age. The walls of the main heart chambers become stiff and rigid and can't relax properly after contracting. This means the heart cannot fill up properly with blood.

It results in reduced blood flow from the heart and can lead to symptoms of heart failure, such as breathlessness, tiredness and ankle swelling, as well as heart rhythm problems.

In many cases the cause is unknown, although sometimes the condition can be inherited.

More information

Find out more about restrictive cardiomyopathy.from Cardiomyopathy UK.

Arrhythmogenic right ventricular cardiomyopathy

In arrhythmogenic right ventricular cardiomyopathy (ARVC), the proteins that usually hold the heart muscle cells together are abnormal. Muscle cells can die and the dead muscle tissue is replaced with fatty and fibrous scar tissue.

The walls of the main heart chambers become thin and stretched, and can't pump blood around the body properly.

People with ARVC typically have heart rhythm problems. Reduced blood flow from the heart can also lead to symptoms of heart failure.

ARVC is an inherited condition caused by a mutation (change) in one or more genes. It can affect teenagers or young adults and has been the reason for some sudden unexplained deaths in young athletes.

There's increasing evidence that prolonged, strenuous exercise makes the symptoms of ARVC worse. It's important that people with or at risk of ARVC discuss this in detail with their heart specialist (cardiologist).

More information

Find out more about ARVC from Cardiomyopathy UK.

Diagnosing cardiomyopathy

Some cases of cardiomyopathy can be diagnosed after various heart scans and tests, such: 

If you've been diagnosed with an inherited type of cardiomyopathy, you may be advised to have a genetic test to identify the faulty gene (mutation) that caused this.

Your relatives can then be tested for the same mutation and, if they have it, their condition can be monitored and managed early.

Treating cardiomyopathy

There's usually no cure for cardiomyopathy, but the treatments can be effective at controlling symptoms and preventing complications. Some types of cardiomyopathy have specific treatments and early diagnosis is very important.

Not everyone with cardiomyopathy will need treatment. Some people only have a mild form of the condition they can control after making a few lifestyle changes.

Lifestyle changes

Whether the cause of cardiomyopathy is genetic or not, it should generally help to:


Medicines may be needed to control blood pressure, correct an abnormal heart rhythm, remove excess fluid or prevent blood clots.

Find out more about:

Hospital procedures

In some people with obstructive hypertrophic cardiomyopathy, the wall dividing the left and right side of the heart (septum) is thickened and bulges into the main heart chamber. They may need to have either:

  • an injection of alcohol into their heart – this is to reduce part of the muscle in the septum
  • a septal myectomy – heart surgery to remove part of the thickened septum (the mitral valve may be repaired at the same time, if necessary)

Those with heart rhythm problems may need to have arrhythmia ablation. This treatment carefully alters the diseased heart tissue that causes the heart rhythm problems.

Or they may have a device implanted, such as:

  • a pacemaker to regulate the heart rate
  • an implantable cardioverter defibrillator (ICD) to prevent a life-threatening abnormal heart rhythm

Find out more about having a pacemaker implanted.

Find out more about implantable cardioverter defibrillators from the British Heart Foundation.

As a last resort, a heart transplant may be necessary.

Broken heart syndrome

Some people who experience significant emotional or physical stress, such as bereavement or major surgery, go on to experience a temporary heart problem.

The heart muscle becomes suddenly weakened or "stunned", causing the left ventricle (one of the heart's main chambers) to change shape. It may be caused by a surge of hormones, particularly adrenaline, during a period of stress.

The main symptoms are chest pain and breathlessness, similar to those of a heart attack. Always call 999 if you or someone else experiences these.

The condition – known medically as Takotsubo cardiomyopathy, or acute stress cardiomyopathy – is more common in women. It's temporary and reversible. It's unusual for it to happen again.

Find out more about Takotsubo cardiomyopathy from Cardiomyopathy UK.

The information on this page has been adapted by NHS Wales from original content supplied by NHS UK NHS website
Last Updated: 24/11/2022 12:56:24