Understanding Restrictive Cardiomyopathy


What is restrictive cardiomyopathy?


Restrictive cardiomyopathy (RCM) is a less common type of heart muscle disease affecting 3-5% of children with cardiomyopathy. With RCM, the walls of the lower chambers of the heart (ventricles) are abnormally stiff but not necessarily thickened or enlarged. The heart's rigid walls fail to relax and expand adequately, "restricting" the ability of the heart to fill with blood. Despite normal pumping function, the heart may not be able to supply enough blood to meet the body's needs. This puts pressure on the upper chambers of the heart (atria), overfilling them so they become enlarged and out of proportion to the size of the lower chambers of the heart (ventricles). In advanced stages of the disease, blood may back up into the liver and lungs resulting in symptoms of congestive heart failure (CHF).

 

How many children are affected?

According to the Pediatric Cardiomyopathy Registry, RCM occurs at a rate of less than 1 per million children.

What causes restrictive cardiomyopathy?

In most cases, the cause of RCM in children is unknown (idiopathic). Most RCM cases are believed to result from sporadic gene mutations (changes

in the DNA of a gene) that occur "spontaneously" for unknown reasons during fetal development. On rare occasions, RCM can run in families where it is 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%.

RCM can also result from conditions that lead to the build-up of fat and proteins in the heart muscle (amyloidosis, sarcoidosis, glycogen, desmin), excess iron in the heart (hemochromatosis), chest exposure to radiation, connective tissue diseases (scleroderma) or rare metabolic disorders. RCM caused by the infiltration of the heart muscle is more likely to be 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%.

 

What are the common symptoms?

Symptoms are often subtle in children with RCM because the disease progresses slowly. Symptoms arise from the decreased filling of the heart and insufficient blood flow to the body. Infants and young children may show irritability, poor feeding and slow weight gain. Older children may experience fatigue, difficulty exercising or breathing (dyspnea), a persistent cough or wheezing, fainting (syncope), abnormal heart beat (palpitations), chest pain (angina) and/or an upset stomach. As RCM advances, fluid builds up in the lungs as well as in the veins and blood vessels that bring blood back to the heart. This may cause neck veins to bulge, an enlarged liver and fluid in the abdomen, face and legs.

Some children may develop abnormal heart rhythms (arrhythmia) where the heart beats too slow (bradycardia) or too fast (tachycardia). Children with some forms of RCM can develop a slow heart rate due to heart block, the abnormal conduction of signals to the heart's pumping chambers.

Pulmonary hypertension (high blood pressure in the lungs) may occur as a result of the heart not being able to fill adequately when blood returns from the lungs. Another complication is blood clots, which can form in the enlarged atria and travel to parts of the body such as the brain, sometimes leading to a stroke.

 

How is restrictive cardiomyopathy diagnosed?

In the early stages, RCM may be difficult to detect in a physical examination because of the absence of symptoms. Therefore, physicians rely on noninvasive cardiac tests such as the echocardiogram with Doppler ultrasound and the electrocardiogram (EKG) to evaluate the condition. An echocardiogram measures the size of the heart's chambers, how well the heart is pumping and the presence and severity of pulmonary hypertension. From this test, an ejection fraction can be calculated by measuring the percentage of blood ejected from the heart with each beat. Unlike other forms of cardiomyopathy, children with RCM typically have normal ejection fractions of 50-70% because the heart's pumping function is unaffected until the later stages of the disease. An EKG provides information on the heart's electrical activity, abnormal heart rhythms or possible heart block associated with RCM. This test nearly always shows abnormal patterns associated with the enlargement of the heart's upper chamber (atria).

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, a Holter monitor to look for abnormal heartbeats and magnetic resonance imaging (MRI) to evaluate heart and blood vessel function.

To confirm the diagnosis of RCM, more invasive cardiac tests are usually needed. A cardiac catheterization is performed to measure heart and lung pressures, which are usually elevated with RCM. A cardiac biopsy, which involves removing tiny pieces of heart muscle for microscopic inspection, may be performed at the same time to look for abnormal deposits in the heart muscle and to distinguish RCM from a potentially treatable disease called constrictive pericarditis.

What are the treatment options?

For children with RCM, medical therapy aims to improve symptoms of heart failure, control arrhythmias and prevent blood clots. Because the cause of cardiac dysfunction is different, drugs such as angiotensin converting enzyme (ACE) inhibitors, calcium channel blockers and beta-blockers often prescribed for other forms of cardiomyopathy are not commonly used to treat patients with RCM. Low doses of diuretics (bumetanide, chlorothiazide, furosemide, spironolactone) may be used to alleviate symptoms related to excess fluid in the lungs and body. Anti-coagulation medication or blood thinners (aspirin, dipyridamole, enoxaparin, heparin, warfarin) may also be prescribed to prevent the development of blood clots.

With RCM caused by deposits in the heart muscle, special diets and anti-inflammatory medications may be helpful in treatment. For children with heart rhythm problems, anti-arrhythmic medications (amiodarone, digoxin, procaineamide) may be prescribed to keep the heart beating at a regular rate. In rare instances, a pacemaker or automatic implantable cardioverter defibrillator (AICD) may be surgically inserted to control arrhythmias that do not respond to medication.

Close monitoring of the child with RCM is important since children with RCM can remain stable for years and then suddenly worsen quickly. A heart transplant may be necessary when a child does not respond to medical treatment or shows signs of severe heart failure. The development of high blood pressure in the lungs (pulmonary hypertension) occurs more frequently in children with RCM than in other forms of cardiomyopathy and can negatively affect the outcome of a heart transplant. Therefore, children with RCM need to be considered for earlier transplant listing if they develop symptoms of pulmonary hypertension. Unfortunately, a heart transplant may not be an option for RCM when it is related to a disease that causes abnormal deposits in the heart and other organs.

 

What is the prognosis?

RCM is a rare disease and there is limited information on the disease in children. Long-term survival increases for children who receive heart transplants. Irreversible severe pulmonary hypertension has been the only risk factor associated with poor outcome for children with RCM.

 

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

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