Dilated Cardiomyopathy
(from sources on our Heart Links) page)



INTRODUCTION

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, it is fairly uncommon, affecting 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-age and older persons, cardiomyopathy can, and often does, occur in the young. The condition tends to be progressive and sometimes worsens fairly quickly.


DILATED (CONGESTIVE) CARDIOMYOPATHY

By far the most common type of heart muscle disease, dilated cardiomyopathy occurs when diseased muscle fibers have stretched, leading to enlargement, or dilation, of a chamber of the heart. This weakens the heart's pumping ability. The heart tries to adjust by further enlarging and stretching--a process known as "compensation."

Dilated cardiomyopathy occurs most often in middle-age 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, and chronic, excessive consumption of alcohol may cause dilated cardiomyopathy. Also, dilated cardiomyopathy occasionally occurs as a complication of pregnancy and childbirth. Other factors are: a variety of infections, mostly viral, which lead to an inflammation of the heart muscle (myocarditis); toxins (such as cobalt); and, rarely, heredity.

Some drugs, used to treat a different medical condition, also can damage the heart and produce the condition. Such drugs include doxorubicin and daunorubicin, both used to treat cancer.

Whatever the cause, the clinical and pathological signs 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 and that produces abnormal weight gain. (The cough and congestion mimic, and so can be misdiagnosed as, pneumonia or acute bronchitis.)

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 is often tentatively diagnosed based on a physical examination and a patient's medical history. As part of the examination, a stethoscope is used to detect abnormal heart sounds, which are typical of the condition.

A final diagnosis may also require 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-level radioactive material (usually equal to that in a set of chest x rays) into a vein, through which it flows to the heart. There, the material is picked up by a computer, which generates pictures showing how well the heart is functioning.

*A cardiac catheterization. In this procedure, a thin plastic tube is inserted into and through a blood vessel until it reaches the heart. A dye is injected, and x rays are taken to assess the heart's structure and function.


Treatment--

Dilated cardiomyopathy is hard to diagnose early. So, 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 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;

*Digitalis, which helps to improve pumping action and regulate the heartbeat;

*Vasodilators, such as angiotensin-converting enzyme (ACE) inhibitors, which relax blood vessels, helping to lower to pump blood through the body; and

*Calcium blockers or beta blockers, which may be used in some patients to help regulate the heartbeat.

Also, patients with irregular heartbeats may be put on any of various drugs to control the rhythm.

Sometimes, if the condition is advanced and the patient does not sufficiently respond to other treatments, a heart transplantation may be performed. 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 loses its ability to circulate blood. As a result, some patients cannot perform even simple physical activities.

However, the disease also can 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, the scarcity of donor hearts limits its availability to about 2,000 Americans a year. People 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 provide only temporary assistance and are not now used as substitutes for heart transplantation.


FUTURE DIRECTIONS

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 NHLBI.

Promising clues came from a team of NHLBI investigators that 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 a person's risk of death in cardiomyopathy. Knowing which patients are at the greatest risk is very important in determining the best approach to the 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.


GLOSSARY

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--A drug used to relax the blood vessel and heart muscle, causing pressure inside blood vessels to drop, or to 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 and advanced into the heart, enabling a physician to study the heart's 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.
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.
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.