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DILATED CARDIOMYOPATHY
Dilated
cardiomyopathy
or DCM, also known as congestive
cardiomyopathy, is a condition in which the
heart becomes weakened and enlarged, and
cannot pump blood efficiently. The decreased heart
function can affect the lungs, liver, and other body
systems.
In DCM a portion of
the myocardium is dilated, often without any obvious
cause. Left and/or right ventricular
systolic pump function of the heart is
impaired, leading to progressive cardiac enlargement
and
hypertrophy, a process called
remodeling.
Dilated
cardiomyopathy is the most common form of
cardiomyopathy. It occurs more frequently in men
than in women, and is most common between the ages
of 20 and 60 years. About one in three cases of
congestive heart failure (CHF) is due to
dilated cardiomyopathy. Dilated cardiomyopathy also
occurs in children.
Causes
Although no cause (etiology)
is apparent in many cases, dilated cardiomyopathy is
probably the end result of damage to the
myocardium produced by a variety of
toxic,
metabolic, or
infectious agents. It may be the late
sequel of acute
viral
myocarditis, possibly mediated through an
immunologic mechanism.
Autoimmune mechanisms are also suggested
as a cause for dilated cardiomyopathy. A reversible
form of dilated cardiomyopathy may be found with
alcohol abuse,
pregnancy,
thyroid disease,
stimulant use, and
chronic uncontrolled
tachycardia. Many cases of dilated
cardiomyopathy are described as idiopathic -
meaning that the cause is unknown.
Genetics
About 20-40% of patients have
familial forms of the disease, with
mutations of genes encoding
cytoskeletal, contractile, or other
proteins present in myocardial cells. The disease is
genetically heterogeneous. Relatives of dilated
cardiomyopathy patients have been found to show
preclinical, asymptomatic heart-muscle changes.
Symptoms
Dilated cardiomyopathy can be present
for several years without causing significant
symptoms. With time, however, the enlarged heart
gradually weakens.
Typical signs and symptoms of heart
failure include: fatigue; weakness; shortness of
breath, sometimes severe and accompanied by a cough,
particularly with exertion or when lying down; and
swelling of the legs and feet, resulting from fluid
accumulation that may also affect the lungs
(congestion) and other parts of the body. It also
produces abnormal weight gain.
Because the heart is enlarged, the
heart valves may be unable to close normally. The
mitral valve, and the tricuspid valve, often leak.
Damage to and stretching of the heart muscle may
result in abnormal heart rhythms (arrhythmias). The
leakage of the valves and the abnormal heart rhythms
may interfere further with the heart's pumping
action.
Diagnosis
The diagnosis is based on the
symptoms and the results of a physical examination.
Electrocardiography (ECG) may detect abnormalities
in the electrical activity of the heart. However,
these abnormalities are usually not sufficient
evidence for a diagnosis. Echocardiography can show
the size and pumping action of the heart. Magnetic
resonance imaging (MRI), which produces very
detailed images of the heart, may be used to confirm
the diagnosis.
If the diagnosis remains in doubt,
cardiac catheterization,an invasive procedure, can
provide additional information about the pumping
ability of the heart or help confirm the diagnosis.
A biopsy can sometimes identify the characteristic
microscopic changes of some disorders that cause
dilated cardiomyopathy (such as a viral infection
that has just developed) and thus confirm the
diagnosis
Treatment
Patients are given
the standard therapy for heart failure, typically
including salt restriction,
angiotensin-converting enzyme (ACE)
inhibitors,
diuretics, and
digitalis.
Anticoagulants may also be used. Alcohol
should be avoided.
Artificial pacemakers may be used in
patients with intraventricular conduction delay, and
implantable cardioverter-defibrillators
in those at risk of arrhythmia. These forms of
treatment have been shown to improve symptoms and
reduce hospitalization.
In patients with
advanced disease who are refractory to medical
therapy, cardiac
transplantation may be considered.
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