Cardiomyopathy
Source:
National Heart, Lung, and Blood Institute
Table
of Contents
Introduction
Nonischemic Cardiomyopathy
Dilated (Congestive) Cardiomyopathy
Hypertrophic Cardiomyopathy
Restrictive Cardiomyopathy
Future Directions
Glossary
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.
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.
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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:
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:
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.
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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:
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.
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.
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 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.
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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.
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.
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."
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.
Diuretic--A drug that helps eliminate excess body fluid; usually used in the treatment of high blood pressure and heart failure.
Edema--Abnormal fluid accumulation in body tissues.
Electrocardiogram (EKG or ECG)--Measurement of electrical activity during heartbeats.
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.
NHLBI Information Center
P.O. Box 30105
Bethesda, MD 20824-0105
Telephone: (301) 251-1222
Fax: (301) 251-1223
U.S. DEPARTMENT
OF HEALTH AND HUMAN SERVICES
Public Health Service
National Institutes of Health
National Heart, Lung, and Blood Institute
NIH Publication No. 97-3082
Originally printed 1995
Revised July 1997
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