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What is
Dilated Cardiomyopathy?
In Dilated Cardiomyopathy the main pumping chambers of the heart are dilated
and contract poorly. This results in a low output of the blood from the heart
and features of heart failure, with build up of fluid behind the left side of
the heart leaving the congestion in the lungs and breathlessness. Occasionally
the right side of the heart is also involved with fluid accumulating in the body
tissues, particularly the ankles and abdomen.
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What
causes
Dilated Cardiomyopathy?
The cause of Dilated
Cardiomyopathy remains uncertain, but it is probable that there are many
different factors that are important. These include viral
infection. Usually viral infections are self-limiting illnesses as the body’s
defence mechanism is able to control the virus, prevent it from spreading, and
kill it. Enteroviruses are common causes of viral infections often presenting
with flu like symptoms. One of the Enteroviruses, CoxsackieB, can affect the
heart but does not usually cause permanent damage. In some instances however,
the evidence suggests that the virus may either persist within the heart or
trigger an auto immune process that continues to damage the heart muscle.
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Auto Immune Disease
Normally the body’s immune system provides a defence against infection.
Occasionally however, for reasons that are uncertain, the immune system may be
activated mistakenly, and begin to attack itself. Viruses are believed to be a common
cause or trigger of the auto immune process which is seen in several conditions
including rheumatoid arthritis where the joints are damaged; juvenile onset
diabetes mellitus where the pancreas is damaged; and the thyroiditis where the
thyroid gland may be involved. In these auto immune conditions, antibodies
circulating in the blood develop in the tissue or organ which is being attacked.
In Dilated Cardiomyopathy, antibodies against the heart are found in
approximately 30% of patients and in a similar proportion of the asymptomatic
relatives. This and other evidence suggests that an auto immune component may
play an important part in the development and progression of Dilated
Cardiomyopathy. The significance of the cardiac antibody in asymptomatic first
degree relatives is under study; in other conditions (diabetes) the presence of
the antibody in asymptomatic relatives identifies those at risk of developing
the condition.
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Genetics
Recently it has become apparent that Dilated Cardiomyopathy is familial in at
least 20% of cases. Evaluation, however, of the family has potential to clarify
the genetic contribution to the development of the condition within individual
families.
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Other aspects
Excessive alcohol consumption has a depressant effect on the heart muscle and
can exacerbate an underlying cardiomyopathy. Abstinence from further alcohol
prevents further damage to the heart muscle and often allows the heart to
recover.
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Pregnancy
There is a form of Dilated Cardiomyopathy which develops during late
pregnancy and in the period shortly following childbirth. The cause is
uncertain, but it is believed that the additional demand of pregnancy on the
heart may be a triggering factor in the development of the condition.
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Symptoms
Symptoms will depend on the stage and evolution of the condition.
–
This is a common symptom which becomes worse
with exertion. It is caused by the build-up of fluid and elevated pressure
in the lungs. When severe, there may be marked breathlessness, even at rest.
Lack of energy – If the cardiac output is low and the body is not
able to get enough blood, the muscles are unable to contract normally and
easily become tired.
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Ankle swelling –
When the right side of the heart fails to expel
the blood it receives, the fluid builds up in the body tissues. This is
called oedema and usually presents initially in the ankles.
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Chest pain –
This may occur at rest or during exercise. Though the
cause of the pain is usually not clear, it is important to emphasise that
the pain is not due to coronary artery disease (coronary arteries are normal
in Dilated Cardiomyopathy) and that the pain does not cause damage to the
heart.
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Arrhythmias – arrhythmias are a common complication. The heart can
either beat too rapidly (tachycardia) or too slowly (bradycardia). Such
arrhythmias are often associated with an uncomfortable awareness of the
heart beat (palpitations) and/or accompanied by dizziness and fainting.
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How
is
Dilated Cardiomyopathy
diagnosed?
This diagnosis relies on a careful history and physical examination to
document symptoms or abnormalities in the physical examination suggestive of cardiac
failure.
An electrocardiogram
should be performed to look for evidence of damage to the heart muscle and 2
dimensional echocardiography is done to provide images of the heart with
measurements of the size of the chambers as well as determination of their
contractile performance. Exercise testing, either on a treadmill or a bicycle,
should be performed to stress the heart. This test is particularly useful as
symptoms may not be obvious at rest and only become apparent during exertion.
Monitoring of the heart rate with a continuous tape recording is also important
to detect arrhythmias which may not be symptomatic. Top of the page
What
treatment is available?
Treatment aims to improve the symptoms of heart failure and to prevent
complications, particularly those arising from the development of arrhythmia. Heart
failure treatment includes water tablets (diuretics) to rid the body of excess fluid,
angiotensin converting enzyme inhibitors to reduce the amount of work the heart has to do,
and beta-blockers to
reduce the heart rate and allow extra filling and improve the contractile
performance of the heart. Anti-arrhythmic drugs
may be necessary if arrhythmias are documented. Occasionally Brady arrhythmias
develop and a pacemaker may be necessary. A small number of patients with Dilated
Cardiomyopathy do not respond to medical treatment and deteriorate to such an extent that
their quality of life and prognosis is poor. At this stage, an individual
should be referred to a specialist hospital for assessment of the potential role of cardiac transplantation.
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With special thanks for the Medical Information
that has been
provided by our team
of experts
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