Hypertrophic Cardiomyopathy (HCM)

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What is Hypertrophic Cardiomyopathy?

An unexpected and unexplained death in apparently healthy young people is referred to as Sudden Death Syndrome. A probable cause of death in the majority of these cases when examined by a pathologist is cardiac. Hypertrophic Cardiomyopathy (HCM) is the cause attributed most often to sudden deaths in young people. In simplistic terminology it is called ‘chucky heart muscle heart disorder.

HCM is a relatively uncommon heart condition, although estimates show that 10,000 people in the UK have the condition.

The muscle fibres in a healthy heart are arranged in an organised way and have a normal thickness of

HCM has been known by a number of names, hypertrophic obstructive cardiomyopathy”, “idiopathic hypertrophic sub-aortic stenosis” and “muscular sub-aortic stenosis” but it is more commonly referred to as HCM.

What causes Hypertrophic Cardiomyopathy?

HCM is a hereditary disease (i.e. it is passed on from parent to child). It is caused by abnormalities in genes which make the protein which causes the contraction of the heart (sarcometric contractile proteins). It is a disease that affects both genders of any ethnic origin, but is slightly more common in the black population.

The condition is present from the time a baby is conceived. The increased growth of the muscle may start before the baby is born when the foetal heart is still developing. The overgrowth of muscle affects the heart’s normal heart beats, which results in less blood being ejected out from the heart.


The symptoms of HCM can vary from patient to patient, as can the severity of the condition. Some people start to suffer from infancy, others in childhood, and others as adults or in elderly life. The symptoms may begin in infancy, childhood or in middle or elderly life. Some people suffer no symptoms at all and the condition can cause unexpected sudden death when exerting themselves or just after.

It is unknown why the symptoms will begin. Many people do not realise they are a sufferer until a member of the family is found to have the condition and others are screened. There is a 50% chance that a child of a parent with the condition will also have the disease.

Symptoms of HCM are: shortness of breath; chest pains (normally brought on by physical exertion); palpitations (rapid, irregular heart beat); light-headedness / blackouts

It does not mean you have HCM if you suffer from any of these symptoms, but your GP may suggest you undertake some tests for the condition or refer to you a cardiologist (heart specialist).

Diagnosing Hypertrophic Cardiomyopathy?

HCM symptoms are similar to other conditions so tests need to be carried out.

One test that will be carried out is an electrocardiogram (ECG), which records the electric signals created by the heart. This is a painless test where electrodes are placed on the chest, ankles and wrists. An ECG will usually reveal an abnormal electrical signal on a patient with HCM, due to the thickening of the muscle heart muscle. If an ECG shows abnormal electrical signals then further tests will be carried out.

An echocardiogram (ECHO), is an ultrasound scan of the heart, and is the most important test in the diagnosis of HCM. This is a painless test very similar to the ultrasound scan that woman have when pregnant. The ECHO produces a picture of the heart in which the thickness of the heart muscle can be measured. Alongside a piece of equipment called a Doppler, the ECHO can create an image of the flow of blood within the heart.

In some centres a blood test may be used to diagnose HCM. This is not available everywhere though and results can take up to 9 months to get back.

What treatment is available?

At present there is no cure for HCM, treatment given is to prevent complications and improve symptoms. Treatment can include: drugs, specialised pacemakers, or possibly surgery in some cases.

When a patient presents with some or all of the symptoms of HCM, the first treatment offered is usually drugs. A number of drugs are used in the treatment of HCM and the choice of treatment varies from patient to patient. Beta-blockers may be used to relieve palpitations, breathlessness and chest pains. They work by slowing the heart beat which reduces its force of contraction. Other drugs may be used to try and reduce the thickening of the heart muscle.

Surgery may be suggested for patients with severe symptoms who do not respond well to treatment with drugs. An operation called a surgical myectomy is usually successful in relieving the symptoms of HCM. This is where a portion of the thickened heart muscle is removed, this widens the outflow tract in the left ventricle and relieves obstruction.

Other forms of treatment are sometimes recommended for HCM sufferers.

For patients suffering with irregular heartbeat (atrial fibrillation) they may be offered Electrical Cardioversion. Under general anaesthetic a small electric shock is given to the chest. This restores the normal heartbeat. In some HCM patients the electric signal of the heart may fail. In these cases a pacemaker may be fitted. A pacemaker is a small box containing a battery. It is placed under the skin in the chest. This box makes sure that the heart receives the electrical signals it requires.

An ICS (Implantable Cardioverter Defibrillator) can be fitted into patients in which a rapid heartbeat is thought could potentially cause a cardiac arrest, and where drugs are not working. An ICD is similar to a pacemaker where a box in placed in the chest under the skin. The box has fine wires which are attached to the heart and record and deliver electrical impulses when an abnormal heart rhythm occurs.

Another procedure called Alcohol Septal Ablation is another form of treatment that may be offered to patients. This is a procedure done under local anaesthetic and is far less invasive than open heart surgery. A tiny amount of alcohol is injected into the blood vessels that supply the thickened parts of the heart muscle. This is to cause death of that particular area because alcohol is extremely toxic to the heart muscles. The areas of dead heart muscle turn into scar tissue resulting in a reduction in the size of the muscle and decreased the obstruction.

The procedure is performed by an operator who gains access to the blood vessels through the wrist or groin. There is a risk that the procedure could cause damage to the electrical system of the heart and cause the patient to require a pacemaker to be fitted.

Occasionally a valve replacement may be required, this is if the mitral valve is affected and does not work properly. In some cases a heart transplant may be required.

The Future

All close family (mother, father, brother, sister, children) should have ECG’s and ECHO’s to establish whether they are a sufferer also. This is important as some people do not have any symptoms so may be a silent sufferer of the condition. There is a 1 in 2 chance of passing hypertrophic cardiomyopathy onto any children they have.

Depending on how severe the condition is for an individual patient, it may be advised not to take part in strenuous exercise or work.

It is important to try not to become overweight as this can put extra strain on the heart.

Avoid drinking too much alcohol as too much can affect the heart muscle.

Disclaimer: The facts and opinions shown in this article are as accurate and up to date as possible, but are provided as general “information resources”, which may not be relevant to individual persons. This article is not a substitute for individual assessment and always take advice from a doctor who is familiar with the particular person.

Related Links:

Booklet from the British Heart Foundation - www.cardiomyopathy.org/assets/files/BHF_HCM_FINAL_28_Sept_09.pdf

Researched by Desiree Rebbeck
Re-written by Lisa Lathane of Actual Admin
Webpage by CHD-UK