Hypertrophic cardiomyopathy (HCM)
is a condition where the heart muscle becomes thickened. Although HCM is a
relatively rare heart disease, it is the commonest of the cardiomyopathies,
affecting 1 in every 500 people.
Traditionally, the term HCM was
used for disease caused by abnormalities in genes which make the proteins
responsible for contraction of the heart, ‘the sarcomere’. More recently the
definition of HCM has been broadened to include a number of other conditions
that result in thickened heart muscle.
It is a disease that can affect
both men and women of any ethnic background. Excessive muscle thickening
tends to develop in puberty or early adulthood or can sometimes develop very
late in life. Rarely, it may even begin before birth when the baby’s heart
is developing and cause problems in childhood.
CRY Consultant
Cardiologist Professor
Sanjay Sharma talks about
the heart muscle disorder
hypertrophic cardiomyopathy
(HCM)
In a healthy adult heart, the muscle fibres are arranged
in an organised fashion and the thickness of the heart’s wall remains
normal. In HCM, however, the heart muscle becomes excessively thick and the
fibres are arranged haphazardly making the heart vulnerable to life
threatening heart rhythms (ventricular fibrillation/ventricular
tachycardia). The thickening may also reduce the efficiency of the heart’s
pumping action or even lead to the blockage or ‘obstruction’ of blood
leaving the main pumping chamber of the heart. This can result in the
symptoms described below. Diagnosing HCM may pose a significant challenge
since the heart muscle may also thicken in individuals who have high blood
pressure or who participate in prolonged athletic training.
CRY Consultant
Cardiologist Professor
Sanjay Sharma discusses
hypertrophic
cardiomyopathy (HCM) in
children
If you have HCM
you may never experience any symptoms. If you do suffer symptoms they can
vary from person to person and may begin in infancy, childhood, middle or
elderly life. No particular symptom or complaint is unique to HCM sufferers.
The most common
symptoms are:
shortness of breath, usually brought on by
physical exertion
chest pains, usually brought on by physical
exertion
palpitations, a rapid and/or irregular heart
beat
light-headedness, blackouts
If you suffer
from any of these symptoms it does not mean that you necessarily have HCM
but if you visit your GP he/she may suggest that you have some tests; or
refer you to a cardiologist.
Diagnosis involves you having an
ECG and an
ultrasound scan of the heart known as an
echocardiogram (ECHO). Most people with HCM have an abnormal ECG and often the ECG may
become abnormal long before thickening of the heart can be seen on an ECHO.
If HCM is suspected, an
exercise ECG and a
Holter monitor will be required. In some cases further imaging of the
heart may be necessary using a
magnetic resonance
imaging (MRI) scan.
Genetic testing can identify carriers of the HCM gene.
Unfortunately, this form of testing is limited at the moment, as 3 - 4 in every
10 people who are known to have HCM do not have mutations of the genes known
to be associated with HCM. An additional problem is that many families who
do have the mutations appear to have a specific change to the DNA code which
is not found in other families (known as a ‘private’ mutation). This
sometimes makes it difficult to decide whether a mutation is causing the
disease or not. Things are further complicated because people with the same
mutation can have different effects. However, if a well known mutation is
identified, genetic testing can be used to confirm the diagnosis, or offered
to the family to screen for the condition.
There is no cure at present for hypertrophic
cardiomyopathy. Treatment is aimed at preventing complications and improving
symptoms. If your tests prove positive your specialist will advise you on
your lifestyle. You will probably be advised not to participate in
competitive sport and strenuous activities. You will also be advised to keep
well hydrated, particularly when exercising or in hot weather. For many people the condition
should not significantly interfere with their lifestyle.
Drugs are given when a patient has symptoms. A variety of
drugs are used in the treatment of HCM and the choice will vary from patient
to patient. However, if you have severe symptoms due to blockage or
‘obstruction’ of blood flow, and you do not improve on tablets, surgical
myectomy or alcohol septal ablation may be suggested (see below). These can
be successful in the relief of symptoms due to obstruction by removing or
damaging a portion of the thickened muscle.
There are other forms of treatment, which are
occasionally recommended:
Electrical cardioversion may be used to treat atrial
fibrillation (irregular heart beat), which is quite common.
A pacemaker may be fitted if your heart’s normal
electric signal fails.
An
Implantable Cardiac Defibrillator (ICD) may be fitted for you if you
have suffered a previous cardiac arrest or a dangerous ventricular
arrhythmia. An ICD will also be considered even if you have not had
these symptoms but have other signs of risk during your assessment.
In a small number of patients the heart pump weakens
eventually and symptoms of heart failure (breathlessness and ankle swelling)
will require treatment (described in dilated cardiomyopathy).
Non-pharmacological treatment of Hypertrophic Cardiomyopathy
A subset
of patients with hypertrophic cardiomyopathy (approximately 25%) can develop
substantial increase in their heart muscle thickness, which can cause
obstruction for the blood to be pumped out the heart. This can lead to
development of significant symptoms such as chest pain and/or difficulty in
breathing.
Such individuals can be
treated with drugs such as beta-blockers. However in some patients, symptoms
continue to persist in spite of treatment with drugs. There are two other
forms of treatments available for such patients to improve their symptoms.
1.
Surgical Myomectomy
This is a major operation
which involves opening of the chest and taking out a ‘chunk’ of the heart
muscle that is causing obstruction. Since this is a major operation, it
comes with some risks such as hazardous effects of general anaesthesia, risk
of damaging other areas of the heart, etc.
2.
Alcohol Septal Ablation
This is a relatively less
invasive procedure which is done under local anaesthesia. In this procedure
a small amount of alcohol is injected into the blood vessels supplying
thickened areas of the heart muscle in an attempt to cause death of that
particular area. This is because alcohol is extremely toxic to the heart
muscles. The dead muscles are then replaced by a scar tissue (see the
figures below). These changes result in reduction in bulk of the muscle,
which in turn relieves obstruction. This also leads to a relatively bigger
chamber (left ventricle) which aids the heart to receive larger amounts of
blood.
The procedure is performed
like an angiogram where the operator gains access to the blood vessels in
the heart via groin or via wrist. However this procedure also carries some
risk such as damage to the electrical system of the heart which might result
in the need for a pacemaker. In some cases, the wrong areas of heart muscle
might be destroyed causing some unwanted effects. However, due to minimal
invasive nature of the procedure, it is gaining more popularity than the
traditional surgical operation.
If your tests prove positive your specialist will advise
you on your lifestyle and you will probably be advised not to participate in
continuous strenuous activities - e.g. competitive sports. Most of the time
the condition should not significantly interfere with your lifestyle and can
be controlled by drugs if necessary.
It will be necessary for you to have at least annual
check-ups. However, the severity of the disease varies from person to person
and even if you have been diagnosed with HCM you may not necessarily present
any symptoms and can live a normal life. Since the disease runs in families,
all immediate blood relatives of affected patients have to be screened with
an ECG and an ECHO.
It is recommended that when HCM is identified in a family member, those
first degree blood relatives where the condition is NOT identified
should return for repeat testing
yearly until the age of 21, then every 5 years until the age of 60.
We are grateful to Camilla Wheeler of the
Community Education Department, Yorkshire Television, for permission to
reproduce information on Hypertrophic Cardiomyopathy from a factsheet produced
to coincide with a 3-D programme on Sudden Death Syndrome, first transmitted in
April 1995
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