Understanding Dilated Cardiomyopathy


What is dilated cardiomyopathy?

Dilated cardiomyopathy (DCM) is the most common form of heart muscle disease affecting 50-60% of children with cardiomyopathy. "Dilated" refers to the enlarged or stretched muscle fibers of the heart. DCM usually starts in the left ventricle, the chamber that pumps oxygenated blood to the body. Like an overstretched rubber band, the heart muscle becomes weak and is unable to pump blood efficiently, forcing the heart to work harder and the heart chamber to enlarge. In some cases, the heart becomes so weak that it cannot pump enough blood to meet the body's needs, limiting the amount of physical activity that can be performed. Fluid may also build up in the lungs and other organs, a condition known as congestive heart failure (CHF).

How many children are affected?

According to the Pediatric Cardiomyopathy Registry, DCM occurs at a rate of 6 per million children. It is more commonly diagnosed in younger children with the average age of diagnosis at 2 years.

Dilated cardiomyopathy (DCM) is the most common form of heart muscle disease affecting 50-60% of children with cardiomyopathy. "Dilated" refers to the enlarged or stretched muscle fibers of the heart. DCM usually starts in the left ventricle, the chamber that pumps oxygenated blood to the body. Like an overstretched rubber band, the heart muscle becomes weak and is unable to pump blood efficiently, forcing the heart to work harder and the heart chamber to enlarge. In some cases, the heart becomes so weak that it cannot pump enough blood to meet the body's needs, limiting the amount of physical activity that can be performed. Fluid may also build up in the lungs and other organs, a condition known as congestive heart failure (CHF).

 

What causes dilated cardiomyopathy?

The most common causes of DCM in children are neuromuscular disorders (e.g. Duchene muscular dystrophy, Becker muscular dystrophy) and myocarditis. Myocarditis is a viral infection that inflames and damages the heart muscle cells. Viruses that cause myocarditis include influenza, Coxsackie B, adenovirus, echovirus and HIV. Other causes of DCM include immune system diseases, exposure to chemicals, toxins or very powerful medications (e.g. chemotherapy drugs), excessive alcohol use, severe anemia or nutritional deficiencies.

Genetic defects are also a major cause of DCM. Gene defects can be familial and it is estimated that 20-30% of children with DCM have a relative with the disease, although they may not be diagnosed or have symptoms. To date, 13 genes have been identified to cause the familial form of DCM in adults. Most of the familial inherited cases are caused by mutations in cytoskeletal genes that maintain the structure of heart muscle cells or by mutations in genes that regulate the way heart muscle cells generate energy. Mutations are changes in the DNA of a gene that can be either inherited or occur "spontaneously" for unknown reasons during fetal development. Familial DCM is usually inherited in an autosomal dominant manner in which one parent contributes the defective gene and the chance that a son or daughter will inherit the condition is 50%.

Children may have DCM associated with a metabolic disorder (e.g. mitochondrial defects) or a genetic malformation syndrome (e.g. Kearns-Sayre syndrome). In these cases, the contraction of the heart muscle is affected because gene defects cause the abnormal processing of protein substances such as calcium. Other gene defects can limit heart growth and lead to the abnormal stretching of muscle cells. These rare disorders are usually inherited in an autosomal recessive manner in which both parents contribute a defective gene and the chance that a son or daughter will inherit the condition is 25%. Rare disorders leading to DCM, such as Barth syndrome or Duchene muscular dystrophy, are X-linked diseases in which the mother contributes the defective gene and the chance that a son will inherit the condition is 50%.

 

What are the common symptoms?

A very common symptom is difficulty breathing and often this is first noticed with increased activity, such as during feeding or exercise or when there is an upper respiratory infection. In babies and young children, additional symptoms include irritability, poor feeding and slow weight gain. In older children, additional symptoms include fatigue, difficulty exercising, a persistent cough, decreased appetite, abdominal pain, nausea and/or vomiting. As the heart function deteriorates, there may be swelling of the abdomen, legs and ankles, decreased urine output, excessive sweating (diaphoresis) and pale or ashen skin.

Some children may develop abnormal heart rhythms (arrhythmia) where the heart beats too slow (bradycardia) or too fast (tachycardia). Symptoms include feeling strange or fast heartbeats (palpitations), fainting (syncope) and/or convulsions (seizures). These symptoms may appear at any stage of the disease even without a child having congestive heart failure.

Children with DCM caused by metabolic abnormalities may also have low blood sugar (hypoglycemia), excessive acid in the blood (metabolic acidosis) or neurological abnormalities such as decreased muscle tone (hypotonia) and changes in mental status or behavior (encephalopathy). These symptoms may arise when the body's metabolic demand exceeds supply or when the body cannot break down accumulated toxins.

 

How do you diagnose dilated cardiomyopathy?

DCM is most often diagnosed in a physical examination when the child shows signs of congestive heart failure such as excessive tiredness, fluid in the lungs (crackles), enlarged liver, a heart murmur or a rapid galloping heartbeat. To diagnose DCM, physicians rely on noninvasive cardiac tests such as the echocardiogram with Doppler ultra-sound and the electrocardiogram (EKG). A diagnosis of DCM is confirmed by an echocardiogram, which measures the size of the heart and how well the heart is pumping. From this test, an ejection fraction can be calculated by measuring the percentage of blood ejected from the heart with each beat. A result of less than 40% indicates severe DCM. An EKG provides information on the heart's electrical activity, abnormal heart rhythms and heart size.

Other tests may be ordered to help determine a child's medical management and prognosis. These include a chest X-ray to check the heart's shape and size and to look for fluid in the lungs, blood tests to look for signs of poor blood flow from the heart, an exercise stress test to see how well the heart can respond to exercise, a Holter monitor to look for abnormal heartbeats and magnetic resonance imaging (MRI) to evaluate heart and blood vessel function.

In some cases, more invasive cardiac tests may be needed. A cardiac catheterization may be performed to measure heart and lung pressures and to take a heart biopsy. A heart biopsy involves re-moving tiny pieces of heart muscle for microscopic inspection to look for signs of myocarditis or metabolic disease.

What are the treatment options?

For children with DCM, medical therapy aims to control the symptoms of congestive heart failure, improve heart function and prevent complications such as blood clots or arrhythmias. With optimal treatment, symptoms can be improved or eliminated in many children with DCM.

Several types of drugs are used in children with DCM to treat heart failure and to stop the heart from deteriorating. The most common medications include angiotensin converting enzyme (ACE) inhibitors (captopril, enalapril, lisinopril) to relax the arteries and decrease the amount of work required by the heart to pump blood to the body, diuretics (bumetanide, chlorothiazide, furosemide, spironolactone) to reduce excess fluid in the lungs or other organs and digoxin to improve the pumping of the heart. More recently, beta-blockers (atenolol, carvedilol, metoprolol) are being prescribed to reduce stress on the heart muscle. Some children with severe heart dysfunction may also require anti-coagulation medications (aspirin, dipyridamole, enoxaparin, heparin, warfarin) to prevent the development of blood clots.

For children with heart rhythm problems, anti-arrhythmic medications (amiodarone, lidocaine, procaineamide) may be prescribed to keep the heart beating at a regular rate. A pacemaker or automatic implantable cardioverter defibrillator (AICD) may be surgically implanted to control arrhythmias that do not respond to medication. Biventricular pacing, which involves pacing the left and right lower heart chambers to beat at the same time, may be used to help a failing heart pump more efficiently.

Close monitoring of the child with DCM is important since heart failure can worsen quickly. A heart transplant may be necessary when a child does not respond to medical treatment or shows signs of severe heart failure, poor growth or high lung pressure (pulmonary hypertension). Children with DCM are more prone to congestive heart failure and therefore have a higher rate of heart transplantation compared to other forms of cardiomyopathy. If DCM results from a disease that affects other systems or organs in the body, unfortunately, a heart transplant may not be an option.

 

What is the prognosis?

In children with DCM, approximately one-third recover, one-third stabilize and the remaining third get worse. If the cause of DCM is myocarditis, children are more likely to improve and have better outcomes than those who have DCM from other causes.

 

What is the Children’s Cardiomyopathy Foundation?

The Children’s Cardiomyopathy Foundation (CCF) is a national non-profit organization dedicated to finding causes and cures for pediatric cardiomyopathy through the support of research, education, awareness and advocacy.

Register with CCF:
www.childrenscardiomyopathy.org

Contact Information:

Children’s Cardiomyopathy Foundation
P.O. Box 547 | Tenafly, New Jersey 07670
Tel: 201-227-8852 | Fax: 201-227-7016
Toll Free: 866-808-CURE (2873)
E-Mail

Funded in part by a grant from the
Medtronic Foundation and eBay Foundation.

Strategy and design provided by
Healthcare Branding Group, Inc.

© Copyright 2006 Children’s Cardiomyopathy Foundation