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Authors: Marilyn Weigner, MD; James P Morgan, MD, PhD
Editors: William J McKenna, MD; Leah K Moynihan, RNC, MSN; Susan B Yeon, MD, JD, FACC
DILATED CARDIOMYOPATHY OVERVIEW — Cardiomyopathy is a disease of the heart muscle, or myocardium, which prevents the heart from functioning normally. There are several types of cardiomyopathy, including:
* Dilated cardiomyopathy
* Hypertrophic cardiomyopathy
* Restrictive cardiomyopathy
* Arrhythmogenic right ventricular cardiomyopathy
* Unclassified cardiomyopathies
In the United States, dilated cardiomyopathy occurs in approximately five to eight people per 100,000; it causes approximately 10,000 deaths and 46,000 hospitalizations each year. It is the most common reason for heart transplantation.
This topic review discusses the definition, symptoms, diagnosis, and treatment of dilated cardiomyopathy. Hypertrophic cardiomyopathy is discussed separately. (See "Patient information: Hypertrophic cardiomyopathy".)
HEART FUNCTION
Normal heart function — The heart is a pump that contains four chambers: the right atrium, right ventricle, left atrium, and left ventricle (figure 1). Blood returning to the heart from the body flows into the right atrium, and then the right ventricle. Blood is pumped out of the right ventricle into the lungs, where oxygen is added. Blood then returns to the heart through the left atrium. Blood in the left atrium flows into the left ventricle, which pumps the blood out the aorta to deliver oxygen to the brain, muscles, and other organs and tissues.
Heart function in dilated cardiomyopathy — Dilated cardiomyopathy (DCM) is a disease of the heart muscle in which the heart chambers become enlarged or dilated (figure 2). The heart muscle is weakened, making it more difficult for blood to flow from the body and lungs into the heart and for blood to be pumped from the heart to the rest of the body. The left ventricle is affected most commonly by DCM, although the right ventricle can also be affected. The dilatation often becomes severe and the heart may become quite enlarged (picture 1). As the function of the left (and/or right) ventricle worsens, signs and symptoms of heart failure may develop.
The term "heart failure" can be misleading because the heart does not completely fail or stop, but instead functions less effectively. Heart failure (HF) may range in severity from a mild condition that causes no symptoms, to one in which the heart muscle is significantly damaged, leaving the person with multiple debilitating symptoms, such as shortness of breath and fatigue at rest. (See "Patient information: Heart failure causes, symptoms, and diagnosis".)
CAUSES OF DILATED CARDIOMYOPATHY — Dilated cardiomyopathy can be caused by a variety of disorders, as listed in the table (table 1). In more than 50 percent of cases, however, no cause can be found and the cardiomyopathy is called "idiopathic".
Some causes of dilated cardiomyopathy are reversible and the condition improves once the cause is treated or eliminated or the condition subsides. Other causes of DCM produce irreversible damage. In these cases, treatment focuses on optimizing the function of the heart, preventing worsening of heart failure, reducing symptoms and preventing complications (eg, irregular heartbeat, blood clots). (See 'Dilated cardiomyopathy treatment' below.)
DILATED CARDIOMYOPATHY SYMPTOMS — The most common symptoms of dilated cardiomyopathy include the following:
* Shortness of breath (dyspnea) with exertion, which may progress to shortness of breath at rest
* Shortness of breath when lying down (orthopnea)
* Sudden shortness of breath at night, often awakening the patient (paroxysmal nocturnal dyspnea)
* Impaired ability to be active or exercise
* Swelling of the lower legs, ankles, and feet (peripheral edema)
Most people develop symptoms of dilated cardiomyopathy between the ages of 20 and 60, although it can occur at any age. Symptoms of heart failure typically do not occur until late in the disease. Symptoms may worsen gradually or abruptly appear or worsen.
Often, there are no early symptoms of DCM and the heart is discovered to be enlarged as a result of a test done for another reason (eg, a chest x-ray, (picture 1).
 DILATED CARDIOMYOPATHY DIAGNOSIS — The diagnosis and evaluation of dilated cardiomyopathy focuses upon determining if there are treatable or reversible causes. This process is described in detail in a separate topic review. (See "Patient information: Heart failure causes, symptoms, and diagnosis", section on Diagnosis.)
Testing of family members — Between 30 and 50 percent of people with idiopathic dilated cardiomyopathy have inherited a genetic mutation for the disease. Some of these mutations can be identified with blood testing. People who have one or more family members who experienced sudden cardiac death or developed unexplained HF before age 60 should be evaluated by a genetics center that is experienced with cardiovascular diseases; a genetics counselor can help to determine if genetic testing would be helpful (see www.nsgc.org, click on "Find a counselor").
If there is no family history of dilated cardiomyopathy, unexplained heart failure, or sudden cardiac death, first degree family members (eg, parents, siblings, children) of a person with DCM can consider screening tests, including an electrocardiogram and echocardiogram, to determine if there are early signs of DCM. However, there are a few caveats related to screening:
* Screening tests cannot always predict which relatives will be affected by DCM or how severe the disease will be.
* Having a single normal screening test does not mean that cardiomyopathy will not develop in the future. Screening tests are usually repeated every three to five years, unless symptoms develop sooner.
The initial symptoms of DCM are variable (shortness of breath, fainting, sudden death). In people with a family history of DCM, any new symptoms should be evaluated promptly.
DILATED CARDIOMYOPATHY TREATMENT — The treatment of dilated cardiomyopathy depends upon the cause, the severity, and whether or not symptoms are present.
Treat the underlying cause — If the cause of dilated cardiomyopathy can be identified, the first step is to treat this cause (table 1). This may include avoiding exposure to toxins (eg, alcohol, cocaine) or treating endocrine disorders (eg, diabetes, thyroid disease).
Treatment of idiopathic DCM — If the cause of dilated cardiomyopathy is not known (ie, idiopathic DCM), no specific treatment is available. Instead, treatments will be recommended to optimize heart function, reduce the risk of worsening disease, prevent complications, and/or reduce symptoms caused by heart failure.
Treatment of heart failure caused by dilated cardiomyopathy is the same as that for heart failure caused by other conditions. Treatment of heart failure is discussed in detail in a separate topic review.
Reference:
http://www.uptodate.com/patients
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