Sudden Death Syndrome is the
term which is now used to describe unexpected and unexplained death occurring in
apparently healthy young people. When the heart is examined by an expert
pathologist a probable cardiac cause of death is found in the majority of
cases.
Sudden death in older people is usually due to coronary artery disease
(blocked arteries in the heart), whereas sudden death in young people (35 years
of age or less) is usually from inherited heart conditions that run in families.
Hypertrophic Cardiomyopathy (HCM) is the most common cause of sudden death in young
people.It is a relatively uncommon heart
disease, although it is estimated that ten thousand people in the United Kingdom
have the condition.
CRY Consultant
Cardiologist Professor
Sanjay Sharma talks about
the heart muscle disorder
hypertrophic cardiomyopathy
(HCM)
In a normal healthy heart, the
muscle fibres are arranged in an organised fashion and they have normal
thickness (<11mm). However in the HCM heart, muscle becomes excessively
thick and the fibres are arranged haphazardly making the heart vulnerable to
some dangerous and potentially fatal heart rhythms (ventricular fibrillation /
ventricular tachycardia).
The heart muscle may thicken in individuals
who have high blood pressure or who have prolonged athletic training, but in HCM patients the muscle thickens without an obvious cause.
HCM was first recognised in the late 1950’s and has been known by a
number of names, hypertrophic obstructive cardiomyopathy", "idiopathic hypertrophic sub-aortic stenosis" and"muscular
sub-aortic stenosis" but it is generally referred to as HCM.
HCM is caused by abnormalities in genes which make the protein responsible for
contraction of the heart (sarcometric contractile proteins) It is a
hereditary disease i.e. it is passed on from parents. In the majority of cases
the condition is inherited from a defective gene of one of the parents. It is a
disease that can affect both men and women of any ethnic origin,
but the condition is
slightly more prevalent in the black population (African / Afro-caribbean
origin).
The condition is present from conception and excessive growth of the muscle
may begin before birth when the foetal heart is developing.
The overgrowth of muscle
interferes with the heart's normal contracting and relaxation, which results in
reduced blood being ejected out from the heart.
CRY Consultant
Cardiologist Professor
Sanjay Sharma discusses
hypertrophic
cardiomyopathy (HCM) in
children
Symptoms and severity can vary from person to person. They may begin in
infancy, childhood or in middle or elderly life. Some patients never have any
symptoms of HCM and the disease can cause unexpected sudden death during or
after excessive exertion.
The reason for the onset of symptoms is not known and no particular symptom
or complaint is unique to HCM sufferers.
Many do not even realise that they have
the disease and it is not until a member of the family presents that other
family members are screened and are found to have the condition.
As it is a
hereditary condition if a parent presents then there is a 50% chance
that each child will also have the disease.
The most common symptoms of HCM are:
Shortness of breath
Chest pains (usually brought on by physical exertion)
Palpitations (rapid, 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 General Practitioner he/she may suggest that you
undertake some tests any may refer you to a cardiologist (a heart specialist).
Because the symptoms of HCM are similar to those of other conditions certain
tests need to be carried out. An electrocardiogram (or ECG) records the
electrical signals from the heart. This test is painless. Electrodes are placed
on the chest, ankles and wrists. If the patient has HCM the ECG usually reveal
an abnormal electrical signal due to the thickening of the muscle and further
tests may be carried out.
Echocardiogram (ultrasound scan of the heart) is the gold standard test in the
diagnosis of this condition. Again
this is painless and is very similar to an ultrasound scan performed on pregnant
women. In this test the ECHO produces a picture of the heart. It is an entirely
safe test and the thickness of the heart muscle can be measured. Together with
equipment called a Doppler, the ultrasound can produce a colour image of the
blood flow within the heart and can measure the heart’s contractions and
filling.
Advances in molecular genetics means that in some
centres, the condition may be diagnosed using a blood test.
This test is not available in every hospital and the results may take up to 9
months.
There is no cure at present for Hypertrophic Cardiomyopathy. Treatment is
aimed at preventing complications and improving symptoms. Treatment can be
obtained through drugs, specialised pacemakers, or in some cases, surgery.
Drugs are given initially when a patient presents some or all on the
symptoms. A variety of drugs are used in the treatment of HCM and the choice of
treatment will vary from patient to patient. The relieve palpitations,
breathlessness and chest pains beta-blockers may be used. These are widely used
for other types of heart disease and high blood pressure and 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 muscle. However, in patients with severe
symptoms, who do not respond too well to treatment with drugs, surgery may be
suggested. A surgical myectomy, where some muscle is removed, is usually
successful in the relief of symptoms. The operation involves removing a portion
of the thickened muscle, which widens the outflow tract in the left ventricle
and relieves obstruction.
There are other forms of treatment, which are occasionally recommended for
people with HCM.
Electrical Cardioversion
–
This is for sufferers of atrial
fibrillation (irregular heart beat). It is carried out under general
anaesthetic and involves the patient being given a small electric shock to
the chest, which restores the normal heartbeat.
Pacemaker
– In HCM sufferers the normal electric signal may fail,
and
if so a pacemaker can be fitted. This is a small box containing a battery,
which is placed in the chest under the skin and ensures the heart receives
the necessary electrical signals.
–
In cases where rapid heart
beat is seen that could potentially cause cardiac arrest, and cannot be
controlled by drugs, an ICD may be fitted. This is similar to a pacemaker
where a box is implanted under the skin in the chest. The box has fine
wires which are attached to the heart to record and deliver electrical
impulses in the presence of an abnormal heart rhythm.
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 lifestyle
modifications. You will probably be advised not to participate in continuous
strenuous activities e.g. competitive sports. For many people the condition
should not significantly interfere with their lifestyle and can be
controlled by drugs. It will be necessary for you to have 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 fairly normal life.
Since the disease runs in families, all first degree relatives of the
affected patients have to be screened with ECG and an echocardiogram.
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.
With special thanks for the Medical Information
that has been
provided by our team
of experts.
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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