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Cardiomyopathy is a disease of the heart muscle. The heart loses its ability to pump blood effectively. Irregular heartbeats (arrhythmias) can occur. The exact cause of the muscle damage is never found in most cases. This is termed idiopathic Cardiomyopathy.
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 cardiomyopathies can, and often do, occur in the young. The condition tends to be progressive and sometimes worsens fairly quickly.
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As noted, there are various types of cardiomyopathy. These fall into two major categories: "ischemic" and "nonischemic" cardiomyopathy.
- Ischemic
cardiomyopathy generally refers to damage resulting from not enough
oxygen getting to the heart muscle. Things that decrease blood flow
to the heart muscle itself, such as coronary artery disease or a heart
attack, are the most common causes. Ischemic cardiomyopathy is much
more common than nonischemic types. These topics(coronary
artery disease and heart attacks)
are discussed elsewhere.
- Nonischemic
cardiomyopathy includes several types. The three main types are
discussed below. The name of each describes the nature of its muscle
damage. Although poor blood flow (Ischemia) to the heart muscle may
be present in later stages it is not the main cause of poor
heart function.
They are:
Dilated (Congestive) Cardiomyopathy
By far the most common type of nonischemic cardiomyopathy, dilated cardiomyopathy occurs when disease-affected muscle fibers "stretch". This leads to enlargement (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." An example would be a balloon that thins out as more and more are is blown into it. Repeated expansion causes the balloon latex to thin out and weaken.
Dilated cardiomyopathy occurs most often in middle-aged people and more often in men than women. However, it 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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Known Causes
Dilated cardiomyopathy can be caused by:
- chronic, excessive consumption of alcohol, particularly in combination with dietary deficiencies. Alcohol has a direct suppressant effect on the heart
- a complication of pregnancy and childbirth.
- various infections, mostly viral, which lead to an inflammation of the heart muscle (myocarditis)
- parasitic infections (a leading cause in many third world countries)
- toxins (such as cobalt, once used in beers, for instance)
- heredity (rare)
- medications - including 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 called "heart failure."
Typical signs and symptoms of heart failure include some or all of the following:
- fatigue
- weakness
- shortness of breath
- cough, particularly with exertion or when lying down
- swelling of the legs and feet
- abnormal weight gain
Many of the above symptoms are caused by too much fluid accumulation in various parts of the body. Fluid in the lungs(congestion) may cause cough and breathing problems. The cough and congestion 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. Further tests may be needed to differentiate dilated cardiomyopathy from other causes of heart failure.
Tests include:
- Chest x ray to show whether the heart is enlarged
- Electrocardiogram (EKG or ECG) to reveal any abnormal electrical activity of the heart.
- Echocardiogram, which uses sound waves to produce movie type pictures of the heart. This test is the most useful because it can show the size of the heart chambers and how well each is pumping.
Other tests may also be needed. These include:
- Radionuclide ventriculogram 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.
- Cardiac catheterization. - 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
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, control the symptoms, and stop the disease's progression. However, no cure now exists.
Therapy begins with the elimination of treatable 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.
- 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, its ability to efficiently pump blood and the amount of blood it can pump decrease. Some patients cannot perform even simple physical activities.
However, the disease may remain stable for years, especially with regular evaluation and treatment by a physician.
Unfortunately, by the time it is diagnosed, the disease often has reached an advanced stage and heart failure has occurred. Damage done to the heart can not be reversed in many patients. 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.
Patients usually die from a continued decline in heart muscle strength; however, 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, donor hearts are scarce. This 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.
Hypertrophic Cardiomyopathy
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 blocks blood flow. It also prevents the heart from properly relaxing between beats and so filling with blood. Eventually, this limits the pumping action. In earlier stages the heart muscle is not weak.
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,symptoms include:
- Breathlessness and chest discomfort (most common)
- Fainting during physical activity
- Strong rapid heartbeats that feel like a pounding in the chest
- 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.
- 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
- Diuretics (to ease heart failure symptoms). Diuretics must be used cautiously as they may decrease the amount of circulating blood (by removing fluid from the body) and thus decrease the amount of blood filling the heart chambers. They are not indicated in all patients with hypertrophic cardiomyopathy.
Medications that increase the forcefulness of heart contractions or speed up the heart rate are usually avoided.
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 Part of the thickened septum (the muscle wall separating the chambers) blocking the blood flow is removed. Sometimes, surgery 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
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 is usually caused by 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. Amyloidosis may be idiopathic (unknown cause) or result from
another disease, such as multiple myeloma (a cancer involving a certain
type of blood cell)
- Sarcoidosis,
an inflammatory disease that causes the formation of small lumps in
organs
- 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
- Congestive heart failure: weakness, fatigue, and breathlessness.
- Swelling of the legs, caused by fluid retention (common)
- 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.
- Useful information can be obtained from an EKG or any of several imaging studies that provide pictures of the heart. These include echocardiography, magnetic resonance imaging, and computed tomography.
- Definitive 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.
GLOSSARY
Other sites/resources
For more information, contact the NHLBI Information Center, a service of the NHLBI and the National Institutes of Health. The Information Center provides information to health professionals, patients, and the public about the treatment, diagnosis, and prevention of heart, lung, and blood diseases.
NHLBI Information Center
P.O. Box 30105
Bethesda, MD 20824-0105
Telephone: (301) 251-1222
Fax: (301) 251-1223
Or check the NHLBI site at: http://www.nhlbi.nih.gov/index.htm