Facts
about
Cardiomyopathy
Introduction
Nonischemic Cardiomyopathy
Dilated (Congestive) Cardiomyopathy
Hypertrophic Cardiomyopathy
Restrictive Cardiomyopathy
Future Directions
Glossary
Cardiomyopathy
is a disease of the heart muscle. The heart loses its ability
to pump blood and, in some instances, heart rhythm is disturbed,
leading to irregular heartbeats, or arrhythmias.
Usually, the exact cause of the muscle damage is never found.
Cardiomyopathy
differs from many other heart disorders in a couple of ways. First,
the types not related to coronary atherosclerosis are fairly uncommon.
Cardiomyopathy affects about 50,000 Americans. However, the condition
is a leading reason for heart transplantation.
Second,
unlike many other forms of heart disease that affect middle-aged
and older persons, certain types of cardiomopathies can, and often do, occur in the young. The
condition tends to be progressive and sometimes worsens fairly
quickly.
As
noted, there are various types of cardiomyopathy. These fall into
two major categories: "ischemic" and "nonischemic"
cardiomyopathy.
- Ischemic
cardiomyopathy typically refers to heart muscle damage that
results from coronary artery disease, such as heart attack,
and will not be discussed here (see page 8 on how to get information
on the disorder).
- Nonischemic
cardiomyopathy includes several types. The three main types
are covered in this fact sheet. They are: dilated, hypertrophic,
and restrictive. The name of each describes the nature of its
muscle damage.
By
far the most common type of nonischemic cardiomyopathy, the dilated
(stretched) form occurs when disease-affected muscle fibers lead
to enlargement, or dilation, of one or more chambers of the heart.
This weakens the heart's pumping ability. The heart tries to cope
with the pumping limitation by further enlarging and stretching--a
process known as "compensation."
Dilated
cardiomyopathy occurs most often in middle-aged people and
more often in men than women. However, the disease has been diagnosed
in people of all ages, including children.
In
most cases, the disease is idiopathic--a
specific cause for the damage is never identified.
But some factors have been linked to the disease's occurrence.
For instance, alcohol has a direct suppressant effect on the heart.
Dilated cardiomyopathy can be caused by chronic, excessive consumption
of alcohol, particularly in combination with dietary deficiencies.
Also, dilated cardiomyopathy occasionally occurs as a complication
of pregnancy and childbirth. Other factors are: various infections,
mostly viral, which lead to an inflammation of the heart muscle
(myocarditis); toxins (such as cobalt, once used in beers, for
instance); and, rarely, heredity.
Some
drugs, used to treat a different medical condition, also can damage
the heart and produce dilated cardiomyopathy. Such drugs include
doxorubicin and daunorubicin, both used to treat cancer.
Whatever
the cause, the clinical and pathological manifestations of dilated
cardiomyopathy are usually the same.
Symptoms
Dilated
cardiomyopathy can be present for several years without causing
significant symptoms. With time, however, the enlarged heart gradually
weakens.
This
condition is commonly called "heart failure,"
and it is the hallmark of dilated cardiomyopathy. 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. (The cough and congestion mimic and, therefore,
can be misdiagnosed as pneumonia or acute bronchitis. Also, heart
failure is often from heart disease other than cardiomyopathy.)
Because
of the congestion, some physicians use the older term "congestive
cardiomyopathy" to refer to dilated cardiomyopathy. In advanced
stages of the disease, the congestion may cause pain in the chest
or abdomen.
In
advanced stages, some patients develop irregular heartbeats, which
can be serious and even life threatening.
Diagnosis
Once
symptoms appear, the condition may be tentatively diagnosed based
on a physical examination and a patient's medical history. More
often, though, further examination is needed to differentiate
dilated cardiomyopathy from other causes of heart failure.
A
firm diagnosis typically requires a chest x ray to show whether
the heart is enlarged, an electrocardiogram
to reveal any abnormal electrical activity of the heart, and an
echocardiogram, which uses sound waves to produce pictures of
the heart.
Other,
more specific tests may also be needed. These include:
- A
radionuclide ventriculogram. This involves injecting low-dose
radioactive material (usually equal to that in a set of chest
x rays) into a vein, through which it flows to the heart. Pictures
are generated by a special camera to show how well the heart
is functioning.
- A
cardiac catheterization. In this
procedure, a thin plastic tube is inserted through a blood vessel
until it reaches the heart. A dye is injected and x rays taken
to assess the heart's structure and function.
Treatment
Since
dilated cardiomyopathy is hard to diagnose early, it is rarely
treated in its beginning stage.
The
goal of treatment is to relieve any complicating factor, if known,
control the symptoms, and stop the disease's progression. However,
no cure now exists.
Therapy
begins with the elimination of obvious risk factors, such as alcohol
consumption. Weight loss and dietary changes, especially salt
restriction, may also be advised.
Drugs
used to treat the condition include:
- Diuretics,
which reduce excess fluid in the body;
- Vasodilators,
such as angiotensin-converting enzyme (ACE) inhibitors,
which relax blood vessels, helping to lower blood pressure and
reducing the effort needed by the heart to pump blood through
the body;
- Digitalis,
which helps to improve pumping action and regulate heartbeat;
and,
- Calcium
blockers or beta blockers, which may be used in some patients to
help regulate heartbeat and to alter the work of the heart muscle.
Also,
patients with irregular heartbeats may be put on any of various
drugs to control the rhythm.
In
critical cases where the condition is advanced and the patient
does not sufficiently respond to other treatments, a heart transplantation
may be needed. The patient's heart is replaced with a donor heart.
Most heart transplant recipients are under age 60 and in good
health other than their diseased heart.
Course
of the disease
As
the heart enlarges, it steadily decreases its efficiency in pumping
blood and the amount of blood it can pump. As a result, some patients
cannot perform even simple physical activities.
However,
the disease also may remain fairly stable for years, especially
with treatment and regular evaluation by a physician.
Unfortunately,
by the time it is diagnosed, the disease often has reached an
advanced stage and heart failure has occurred.
Consequently, about 50 percent of patients with dilated cardiomyopathy
live 5 years once heart failure is diagnosed; about 25 percent
live 10 years after such a diagnosis.
Typically,
patients die from a continued decline in heart muscle strength,
but some die suddenly of irregular heartbeats.
For
patients with advanced disease, heart transplantation greatly
improves survival: 75 percent of patients live 5 years after a
transplantation. However, in the United States, the scarcity of
donor hearts limits the number of transplantations to about 2,000
persons a year. Those who qualify for heart transplantation often
have to wait months, or even years, for a suitable donor heart.
Some patients with dilated cardiomyopathy die awaiting a transplant
but, according to recent studies, others improve enough from aggressive
medical treatment to be taken off the waiting list.
Also,
some critically ill cardiomyopathy patients with declining heart
function use a small, implanted mechanical pump as a bridge to
transplantation. Called left ventricular assist
devices (LVADs), these pumps take over part or virtually all
of the heart's blood pumping activity. The devices provided only
temporary assistance and are not now used as substitutes for heart
transplantation.
The
second most common form of heart muscle disease is hypertrophic cardiomyopathy. Physicians sometimes call it by
other names: idiopathic hypertrophic subaortic stenosis (IHSS),
asymmetrical septal hypertrophy (ASH), or hypertrophic obstructive
cardiomyopathy (HOCM).
In
hypertrophic cardiomyopathy, the growth and arrangement of muscle
fibers are abnormal, leading to thickened heart walls. The greatest
thickening tends to occur in the left ventricle (the heart's main pumping chamber), especially
in the septum, the wall that separates the
left and right ventricles. The thickening reduces the size of
the pumping chamber and obstructs blood flow. It also prevents
the heart from properly relaxing between beats and so filling
with blood. Eventually, this limits the pumping action.
Hypertrophic
cardiomyopathy is a rare disease, occurring in no more than
0.2 percent of the U.S. population. It can affect men and women
of all ages. Symptoms can appear in childhood or adulthood.
Most
cases of hypertrophic cardiomyopathy are inherited. Because of
this, a patient's family members often are checked for signs of
the disease, although the signs may be much less evident or even
absent in them. In other cases, there is no clear cause.
Symptoms
Many
patients have no symptoms. For those who do, the most common are
breathlessness and chest discomfort. Other signs are fainting
during physical activity, strong rapid heartbeats that feel like
a pounding in the chest, and fatigue, especially with physical
exertion.
In
some cases, the first and only manifestation of hypertrophic cardiomyopathy
is sudden death, caused by a chaotic
heartbeat. The heart's lower chambers beat so chaotically and
fast that no blood is pumped. Instead of beating, the heart quivers.
In
advanced stages of the disease, patients may have severe heart failure and its associated symptoms, including fluid accumulation
or congestion.
Diagnosis
By
listening through a stethoscope, a physician may hear the abnormal
heart sounds characteristic of hypertrophic
cardiomyopathy The electrocardiogram
(EKG, or ECG) may help diagnose the condition by detecting changes
in the electrical activity of the heart as it beats.
Echocardiography
is one of the best tools for diagnosing hypertrophic cardiomyopathy.
It uses sound waves to detect the extent of muscle-wall thickening
and to assess the status of the heart's functioning.
Physicians
also may request radionuclide studies to gather added information
about the disease's effect on how the heart is pumping blood.
Other
tests that also may provide useful information are the chest x
ray, cardiac catheterization, and
a heart muscle biopsy.
Treatment
Treatments
for hypertrophic cardiomyopathy vary but can include the following:
- Lifestyle
changes. Patients with serious electrical and blood-flow abnormalities
must be less physically active.
- Medications.
Various drugs are used to treat the disease. They include beta
blockers (to ease symptoms by slowing the heart's pumping
action), calcium channel blockers (to relax the heart and reduce
the blood pressure in it), antiarrhythmic medications, and diuretics
(to ease heart failure symptoms).
However,
drugs do not work in all cases or may cause adverse side effects,
such as fluid in the lungs, very low blood pressure, and sudden
death. Then, other treatment, such as a pacemaker or surgery,
may be needed.
- Pacemakers.
These change the pattern and decrease the force of the heart's
contractions. The pacemaker can reduce the degree of obstruction
and so relieve symptoms. A pacemaker needs to be carefully monitored
after its insertion in order to properly adjust the electrical
impulse. Some patients who have a pacemaker inserted feel no
relief and go on to have heart surgery.
- Surgery.
This usually calls for removal of part of the thickened septum
(the muscle wall separating the chambers) that is blocking the
blood flow. Sometimes, surgery also must replace a heart valve--the
mitral valve, which connects the left ventricle and the left
atrium, the upper chamber that receives oxygen-rich blood from
the lungs.
Surgery
to remove the thickening eases symptoms in about 70 percent
of patients but results in death in about 1 to 3 percent of
patients. Also, about 5 percent of those who have surgery
develop a slow heartbeat, which is then corrected with a pacemaker.
Course
of the disease
The
course of the disease varies. Many patients remain stable; some
improve; some worsen in symptoms and lead severely restricted
lives. Patients may need drug treatment and careful medical supervision
for the rest of their lives.
Hypertrophic
cardiomyopathy patients also are at risk of sudden death. About
2 to 3 percent die each year because the heart suddenly stops
beating. This cardiac arrest is
brought on by an abnormal heartbeat. Over 10 years, the risk of
sudden death can be 20 percent or more.
Restrictive
cardiomyopathy is rare in the United States and most other
industrial nations. In this disease, the walls of the ventricles
stiffen and lose their flexibility due to infiltration by abnormal
tissue. As a result, the heart cannot fill adequately with blood
and eventually loses its ability to pump properly.
Restrictive
cardiomyopathy typically results from another disease, which
occurs elsewhere in the body. In the United States, restrictive
cardiomyopathy is most commonly related to the following: amyloidosis,
in which abnormal protein fibers (amyloid) accumulate in the heart's
muscle; sarcoidosis, an inflammatory disease that causes the formation
of small lumps in organs; and hemochromatosis, an iron overload
of the body, usually due to a genetic disease.
In
general, restrictive cardiomyopathy does not appear to be inherited;
however, some of the diseases that lead to the condition are genetically
transmitted.
Symptoms
Typical
signs of the condition include symptoms of congestive heart failure:
weakness, fatigue, and breathlessness. Swelling of the legs, caused
by fluid retention, occurs in a significant number of patients.
Other symptoms include nausea, bloating, and poor appetite, probably
because of the retention of fluid around the liver, stomach, and
intestines.
Diagnosis
A
physician may suspect restrictive cardiomyopathy
based on a patient's symptoms and the presence of another disease.
Although symptoms of congestive heart failure may predominate,
the size of the heart remains relatively small, unlike other cardiomyopathies.
Diagnostic
information comes from an electrocardiogram or any of several
imaging studies that provide pictures of the heart. These include
echocardiography, magnetic resonance imaging, and computed tomography.
A
definite diagnosis usually requires cardiac catheterization studies or a biopsy, in which
a tiny piece of tissue--including heart muscle--is removed for
laboratory analysis.
Treatment
Restrictive
cardiomyopathy has no specific treatment. The underlying disease
that leads to the heart problem also may not be treatable.
In
general, the use of traditional heart drugs has been limited in
this cardiomyopathy, although diuretics
may help control fluid accumulation.
In
rare cases, surgery is sometimes used to try to improve blood
flow into the heart.
Course
of the disease
The
condition is similar to dilated cardiomyopathy and tends to worsen
with time. Only about 30 percent of patients survive more than
5 years after diagnosis.
Future
advances in the diagnosis and treatment of cardiomyopathy depend
on a better understanding of the disease process and why heart
muscle is damaged. A lot of research is under way to identify
these processes and whether they can be halted or even reversed.
Much of the research is conducted at or supported by the National
Heart, Lung, and Blood Institute (NHLBI).
Promising
clues came from investigators at and supported by the NHLBI who
discovered some of the genes responsible for hypertrophic cardiomyopathy.
Their work represents an important first step in understanding
how the disease is transmitted and how it progresses.
Researchers
also are trying to determine the best use of currently available
treatments, especially drug therapies. Drugs useful for other
conditions may help treat cardiomyopathy. For example, drugs effective
in treating high blood pressure also help manage heart failure
and irregular heartbeats.
Additionally,
much work has been--and continues to be--done on identifying factors
that increase or decrease the risk of death for persons with cardiomyopathy.
Knowing which patients are at the greatest risk is very important
in determining the best approach to evaluation and treatment of
their condition.
The
development of improved treatments for cardiomyopathy, however,
awaits still more research and a better understanding of the disease
process.
Angiotensin
converting enzyme (ACE) inhibitor--A drug used to decrease
pressure inside blood vessels.
Arrhythmia--An
irregular heartbeat.
Beta
blocker--A drug used to slow the heart rate and reduce pressure
inside blood vessels. It also can regulate heart rhythm.
Calcium
channel blocker (or calcium blocker)--A drug used to relax
the blood vessel and heart muscle, causing pressure inside blood
vessels to drop. It also can regulate heart rhythm.
Cardiac
arrest--A sudden stop of heart function. See also "sudden
death."
Cardiac
catheterization--A procedure in which a thin, hollow tube
is inserted into a blood vessel. The tube is then advanced through
the vessel into the heart, enabling a physician to study the heart
and its pumping activity.
Cardiomyopathy--A
disease of the heart muscle (myocardium).
Congestion--Abnormal
fluid accumulation in the body, especially the lungs.
Digitalis--A
drug used to increase the force of the heart's contraction and
to regulate specific irregularities of heart rhythm.
Dilated
cardiomyopathy--Heart muscle disease that leads to enlargement
of the heart's chambers, robbing the heart of its pumping ability.
Diuretic--A
drug that helps eliminate excess body fluid; usually used in the
treatment of high blood pressure and heart failure.
Dyspnea--Shortness
of breath.
Echocardiography--A
test that bounces sound waves off the heart to produce pictures
of its internal structures.
Edema--Abnormal
fluid accumulation in body tissues.
Electrocardiogram
(EKG or ECG)--Measurement of electrical activity during heartbeats.
Heart
failure--Loss of pumping ability by the heart, often accompanied
by fatigue, breathlessness, and excess fluid accumulation in body
tissues.
Hypertrophic
cardiomyopathy--Heart muscle disease that leads to thickening
of the heart walls, interfering with the heart's ability to fill
with and pump blood.
Idiopathic--Results
from an unknown cause.
Left ventricular assist device (LVAD)--A
mechanical device used to increase the heart's pumping ability.
Pulmonary
congestion (or edema)--Fluid accumulation in the lungs.
Restrictive
cardiomyopathy--Heart muscle disease in which the muscle
walls become stiff and lose their flexibility.
Septum--In the heart, a muscle wall
separating the chambers.
Sudden death--Cardiac arrest caused
by an irregular heartbeat. The term "death" is somewhat
misleading, because some patients survive.
Ventricles--The two lower chambers
of the heart. The left ventricle is the main pumping chamber in
the heart.
Ventricular fibrillation--Rapid,
irregular quivering of the heart's ventricles, with no effective
heartbeat.
Reference:
from the National Heart, Lung, and Blood Institute
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