NORD gratefully acknowledges Steve D. Colan, MD, Professor of Pediatrics at Harvard Medical School and Director of Clinical Research, Boston Children's Hospital, and the Children's Cardiomyopathy Foundation, for assistance in the preparation of this report.
Pediatric cardiomyopathy is a rare heart condition that affects infants and children. Specifically, cardiomyopathy means disease of the heart muscle (myocardium). Several different types of cardiomyopathy exist and the specific symptoms vary from person to person. In some affected individuals, no symptoms may be present (asymptomatic); in many people, cardiomyopathy is a progressive condition that may result in an impaired ability of the heart to pump blood; fatigue; heart block; irregular or rapid heartbeats (tachycardia); and, potentially, heart failure and sudden cardiac death.
Cardiomyopathy may be termed ischemic or nonischemic. Ischemic cardiomyopathy refers to a lack of blood flow and oxygen (ischemia) to the heart and in pediatrics is due to a congenital abnormality of the blood vessels that supply the heart (coronary arteries). Nonischemic cardiomyopathy refers to structural damage or malfunction of the heart muscle due to causes other than coronary artery abnormalities. Nearly all patients with pediatric cardiomyopathy have the nonischemic type. This report deals with nonischemic pediatric cardiomyopathy.
Cardiomyopathy may also be termed primary or secondary. Primary cardiomyopathy occurs by itself (no other parts of the body are involved) due to a genetic defect or an external cause such as heart muscle inflammation (myocarditis) caused by viral or bacterial infections; exposure to certain toxins such as heavy metals or excessive alcohol use. Some disorders affect the heart in addition to additional organ systems and in this case it is called a secondary cardiomyopathy. According to the Pediatric Cardiomyopathy Registry, approximately 79 percent of pediatric cardiomyopathy is idiopathic (that is, the cause is unknown).
Cardiomyopathy has traditionally been divided into three basic subtypes based upon the specific changes within the heart. These subtypes are: dilated, hypertrophic, and restrictive. There are several other less common forms such as arrhythmogenic right ventricular dysplasia, noncompaction, and others where it is controversial whether they are subtypes of the three principle forms or should be considered as completely different diseases.
The specific symptoms of pediatric cardiomyopathy depend upon the type of cardiomyopathy present. Many individuals with cardiomyopathy will not exhibit any symptoms (asymptomatic) throughout life. Common symptoms of cardiomyopathy that may occur include fatigue, shortness of breath (dyspnea) especially with exertion, and chest pain. Additional symptoms potentially associated with all forms of cardiomyopathy include irregular heartbeats (arrhythmias) such as abnormally fast (tachycardia) or slow (bradycardia) heartbeats. In some individuals, cardiomyopathy may progress to cause congestive heart failure, cardiac arrest, and sudden death. Cardiomyopathy can be present at birth or have new onset at any age, and symptoms may or may not be present for many years.
The normal heart has four chambers. The two upper chambers, known as atria, are separated from each other by a fibrous partition known as the atrial septum. The two lower chambers are known as ventricles and are separated from each other by the ventricular septum. Valves connect the atria (left and right) to their respective ventricles. The valves allow for blood to be pumped through the chambers and prevent the flow from going backwards. Blood travels from the right ventricle through the pulmonary artery to the lungs where it receives oxygen. The blood returns to the heart through pulmonary veins and enters the left ventricle. The left ventricle sends the now oxygen-filled blood into the main artery of the body (aorta). The aorta distributes the blood throughout the body.
The various forms of nonischemic cardiomyopathy occur because of structural damage and malfunction of the heart muscle itself. For most people with nonischemic cardiomyopathy, the main pumping chamber of the heart, the left ventricle, is affected. However, the right ventricle and the atria may also become involved.
Dilated cardiomyopathy is characterized by abnormal enlargement (dilatation) of the left and/or right ventricle because of a weakening of the heart’s pumping action, causing a limited ability to circulate blood to the lungs and the rest of the body which may result in fluid buildup in the lungs and various body tissues, a condition known as congestive heart failure. In some individuals, all four chambers of the heart may be affected. Symptoms of congestive heart failure may depend upon an affected child’s age and other factors. In young children, for example, heart failure may be manifest as fatigue and shortness of breath (dyspnea) upon exertion. Additional symptoms may include swelling of the legs and feet and, in some people, chest pain. Initial symptoms of dilated cardiomyopathy in infants and children may include irritability, a persistent cough, shortness of breath, and poor feeding resulting in the failure to gain weight at the expected rate (failure to thrive). Affected individuals may also experience excessive sweating, fatigue, wheezing, and paleness of the skin (pallor). More serious complications may include fainting episodes (syncope), abdominal pain, irregular heartbeats, and fluid accumulation within the lungs (pulmonary congestion) resulting in a persistent cough.
Hypertrophic cardiomyopathy is characterized by abnormal thickening of the walls of the heart potentially resulting in obstruction of blood flow in and out of the heart. In most patients, the left ventricle is primarily affected. The symptoms of hypertrophic cardiomyopathy vary widely among affected individuals. In many cases, affected individuals have no symptoms. Affected infants and children may experience shortness of breath upon exertion, fatigue, excessive sweating, and poor appetite and weight gain resulting in growth failure. As affected children age, they may experience chest pain or discomfort, irregular heartbeats, dizziness or fainting episodes (syncope) usually upon heavy exertion, and, eventually, congestive heart failure and fluid accumulation within the lungs. In some cases, affected individuals may experience sudden cardiac arrest and, potentially, sudden death.
Restrictive cardiomyopathy is extremely rare in children. In this form of cardiomyopathy, the muscular walls of the heart become stiff, impeding blood flow into the heart. Symptoms associated with restrictive cardiomyopathy in infants and children include shortness of breath, fatigue, chest pain, and poor appetite and weight gain, resulting in growth failure. Additional symptoms may include fluid collection in the abdomen (ascites) and feet, congestion of the lungs, and an abnormally large liver (hepatomegaly). Irregular heartbeats, the formation of blood clots and heart block may also occur. Restrictive cardiomyopathy may progress to cause congestive heart failure and sudden death.
Arrhythmogenic Right Ventricular Dysplasia
Arrhythmogenic right ventricular dysplasia (ARVD) is a rare form of nonischemic cardiomyopathy in which the normal muscular tissue of the right ventricle is replaced by fatty tissue and may also occasionally affect the left ventricle. The symptoms of ARVD vary greatly. Symptoms may develop during childhood, but in most people do not appear until the 30s or 40s. Symptoms associated with ARVD may include irregular heartbeats (arrhythmias), shortness of breath, swollen neck veins, abdominal discomfort, and fainting episodes (syncope). In some patients, no symptoms are apparent until an affected individual goes into cardiac arrest and possibly sudden death.
Most cases of pediatric cardiomyopathy occur for unknown reasons (idiopathic). Pediatric cardiomyopathy may be inherited or acquired. In recent years, investigators have determined that the cause of pediatric cardiomyopathy in many children may be disruption or changes (mutations) of certain genes. Researchers have discovered more than 300 different genetic mutations that may play a role in the development of different forms of cardiomyopathy.
In most patients, the cause of dilated cardiomyopathy is unknown (idiopathic). However, dilated cardiomyopathy may be acquired or inherited. The development of dilated cardiomyopathy has been linked to excessive alcohol use, viral or bacterial infections that result in inflammation of the heart muscle (myocarditis), autoimmune disease, and metabolic deficiencies. Exposure to certain toxins including heavy metals (e.g., cobalt or lead) and certain chemotherapy drugs may lead to the development of the disorder. Dilated cardiomyopathy may also occur as part of certain endocrine, blood (hematological), and collagen vascular disorders. It can also occur as a consequence of congenital heart malformations or acquired heart valve abnormalities that result in an excess workload on the heart.
Dilated cardiomyopathy may also occur secondary to a generalized genetic disorder such as one of the muscular dystrophies, certain metabolic disorders, or a rare genetic disorder such as Barth syndrome. In some cases, dilated cardiomyopathy may be inherited as an isolated genetic condition (familial dilated cardiomyopathy). It has been estimated that genetic factors play a role in more than 30 percent of dilated cardiomyopathy. Most are inherited as an autosomal dominant trait, but autosomal recessive or X-linked inheritance has also been reported.
Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary for the appearance of the disease. The abnormal gene can be inherited from either parent, or can be the result of a new mutation (gene change) in the affected individual. The risk of passing the abnormal gene from affected parent to offspring is 50% for each pregnancy. The risk is the same for males and females.
Recessive genetic disorders occur when an individual inherits the same abnormal gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk for two carrier parents to both pass the abnormal gene and, therefore, have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier like the parents is 50% with each pregnancy. The chance for a child to receive normal genes from both parents is 25%.
X-linked genetic disorders are conditions caused by a non-working gene on the X chromosome and manifest mostly in males. Females that have a non-working gene present on one of their X chromosomes are carriers for that disorder. Carrier females usually do not display symptoms because females have two X chromosomes and only one carries the non-working gene. Males have one X chromosome that is inherited from their mother and if a male inherits an X chromosome that contains a non-working gene he will develop the disease. Female carriers of an X-linked disorder have a 25% chance with each pregnancy to have a carrier daughter like themselves, a 25% chance to have a non-carrier daughter, a 25% chance to have a son affected with the disease and a 25% chance to have an unaffected son. If a male with an X-linked disorder is able to reproduce, he will pass the non-working gene to all of his daughters who will be carriers. A male cannot pass an X-linked gene to his sons because males always pass their Y chromosome instead of their X chromosome to male offspring.
Hypertrophic cardiomyopathy is inherited as an autosomal dominant condition in more than 50 percent of patients. In some people, there is no apparent family history of the disorder. In some of these individuals, hypertrophic cardiomyopathy may be caused by new genetic changes (mutations) that occur spontaneously for unknown reasons (sporadically). These mutations may be passed onto future generations as an autosomal dominant trait. Non-genetic factors, in combination with genetic factors, may play a role in determining who develops hypertrophic cardiomyopathy. In other cases, the cause of hypertrophic cardiomyopathy is unknown (idiopathic).
In most patients, restrictive cardiomyopathy occurs secondary to a systemic disorder such as amyloidosis, sarcoidosis or hemochromatosis. In amyloidosis, specific proteins (amyloids) abnormally accumulate in the heart resulting in stiffening of the ventricles, which prevents proper blood flow through the heart. In sarcoidosis, certain white blood cells abnormally accumulate in the heart. In hemochromatosis, iron accumulates in the heart. Some people with restrictive cardiomyopathy have certain connective tissue diseases.
Restrictive cardiomyopathy may also occur as a result of scarring from open-heart surgery or exposure of the chest to radiation. In a rare subset of cases, restrictive cardiomyopathy has run in families suggesting that hereditary (genetic) factors may play a role in the development of the disorder in rare cases. In children, the cause of restrictive cardiomyopathy is unknown in more than 90% of those affected.
Genetic factors play a role for most individuals affected with ARVD. For many people, the disorder is inherited as an autosomal dominant trait. Some people with ARVD may have had an infection of the heart muscle.
The exact prevalence of pediatric cardiomyopathy in the general population is unknown and estimates vary within the medical literature. However, because children who are asymptomatic often go unrecognized, pediatric cardiomyopathy is under-diagnosed, making it difficult to determine the true frequency of these disorders in the pediatric population.
According to the national Pediatric Cardiomyopathy Registry, 1 in every 100,000 children in the United States under the age of 18 is diagnosed with primary cardiomyopathy.
This estimate, however, excludes children affected by secondary cardiomyopathy and potentially children who are undiagnosed because they are asymptomatic. Within the pediatric population, cardiomyopathy as a whole occurs in approximately 12 children out of every million. Approximately 1,000 to 5,000 children are diagnosed each year.
The estimated incidence of dilated cardiomyopathy is 36.5 per 100,000 children. According to the Pediatric Cardiomyopathy Registry, the estimated incidence of hypertrophic cardiomyopathy is 5 per 1 million children. The overall prevalence of hypertrophic cardiomyopathy is estimated to be less than .2 percent of the general population. The prevalence of restrictive cardiomyopathy is unknown. According to one estimate, ARVD occurs in 1 out of 5,000 people in the general population.
According to two studies published in the April 24th, 2003 issue of the New England Journal of Medicine, children are much more likely to develop cardiomyopathy early in life than previously thought. In fact, children are 10 times more likely to develop cardiomyopathy before the age of one than between ages two through 18 combined. In one of the studies, the overall incidence rate of cardiomyopathy was 1.13 per 100,000 children.
Dilated and restrictive cardiomyopathies affect males and females in equal numbers. Hypertrophic cardiomyopathy is slightly more common in males. ARVD affects more males than females. Cardiomyopathy continues to be the leading reason for heart transplants in children.
Pediatric cardiomyopathy may be diagnosed based upon a thorough clinical evaluation, identification of characteristic physical findings, a complete patient and family history, and a variety of specialized tests. Such tests may include x-ray studies (e.g., computed tomography), electrocardiography (EKG), or echocardiography. An EKG, which records the electrical activities of heart muscle, may reveal abnormal electrical patterns (e.g., resulting in arrhythmias). During an echocardiogram, sound waves are bounced off the heart (echoes), enabling physicians to study cardiac function and motion.
Three additional tests that may be performed for evaluation of heart disease are cardiac catheterization, cardiac magnetic resonance imaging (MRI) and radionuclide ventriculogram. During the cardiac catheterization, a small hollow tube (catheter) is inserted into a large vein and threaded through the blood vessels leading to the heart. Cardiac catheterization may enable physicians to withdraw blood to assess oxygen content, measure blood pressure in the heart, evaluate heart function, obtain small samples of myocardial tissue for microscopic evaluation, or thoroughly identify certain anatomical abnormalities. Cardiac MRI generates images of the heart similar to echocardiography but uses magnetic waves instead of sound waves. During radionuclide ventriculogram, tiny amounts of low-dose radioactive materials (tracers) are injected into to a vein and travel into the heart. Tracers release energy that is used by special cameras to produce pictures of the heart.
Because certain forms of cardiomyopathy may occur as part of a larger genetic disorder, infants and young children with a diagnosis of cardiomyopathy should receive specific tests to rule out any potentially associated disorders such as metabolic disorders.
The treatment of pediatric cardiomyopathy is directed toward the specific symptoms that are apparent in each individual. Such treatment may require the coordinated efforts of a team of medical professionals, such as pediatricians; physicians who specialize in childhood heart disease (pediatric cardiologists); specialists in the study of the blood and blood-forming tissues (hematologists); pediatric cardiothoracic surgeons; physical therapists; occupational therapists; and/or other health care professionals. Individuals with pediatric cardiomyopathy may be treated by lifestyle changes, dietary restrictions, various medications, and surgery.
It is important to note that many drug therapies and surgical techniques used to treat cardiomyopathy have predominantly been used and tested in adults. Only limited information exists detailing the effectiveness of such therapies in children with cardiomyopathy. More research is necessary to determine the long-term safety and effectiveness of such therapies in the pediatric population.
Specific therapeutic procedures and interventions may vary, depending upon numerous factors such as the specific type of cardiomyopathy present; the progression of the disease upon diagnosis; an affected individual’s age; associated health conditions; an individual’s tolerance to certain medications; and additional factors.
Individuals with dilated cardiomyopathy may be treated with a variety of medications including drugs that reduce abnormal fluid retention by promoting the production and excretion of urine (diuretics); drugs that reduce the workload of the heart by blocking certain substances from binding to structures within the heart (beta blockers); and digitalis medications such as digoxin, which increase the efficiency of heart muscle contractions and produce a more regular heartbeat. Another type of medication used to treat individuals with dilated cardiomyopathy are vasodilators, which relax blood vessels, thereby lowering the blood pressure and minimizing the effort needed by the heart to pump blood throughout the body. Angiotensin-converting enzyme (ACE) inhibitors are a type of vasodilator.
Children with a more serious dilated cardiomyopathy may need surgery to implant a device that helps maintain normal heart rhythm through electrical stimulation (pacemakers or defibrillators. If drug therapy fails some individuals may require a heart transplant (see below).
Individuals with hypertrophic cardiomyopathy may be treated with a variety of drugs including beta-blockers, calcium channel blockers, and drugs that regulate irregular heartbeats (anti-arrhythmics). If drug therapy does not work, a permanent pacemaker or defibrillator may be implanted to help control irregular heartbeats. In some patients where drug therapy does not work, the blockage that causes the enlargement of the heart and restricts blood flow that characterizes hypertrophic cardiomyopathy may be treated with surgery. Surgical techniques may include septal myectomy or alcohol ablation.
Septal myectomy is a type of open-heart surgery, in which a portion of the abnormally thick and stiff ventricular septum (the partition that separates the left and right ventricles) is removed. This procedure allows for improved blood flow and reduces the symptoms associated with severe hypertrophic cardiomyopathy. Alcohol ablation is a new catheterization procedure in which alcohol is used to destroy certain heart cells, thereby shrinking the heart muscle and resulting in improved blood flow. In some cases of hypertrophic cardiomyopathy, a heart transplant may ultimately be necessary (see below).
Restrictive cardiomyopathy may be treated with diuretics and drugs that prevent blood clotting (anticoagulants). A pacemaker or defibrillator may be implanted to help control irregular heartbeats. In most cases, heart transplantation will be necessary. Some physicians recommend that affected children be listed for transplant as soon as the diagnosis is made.
ARVD may be treated by avoidance of severe physical and emotional stress; drugs that help regulate heart rhythms, and/or the implantation of a defibrillator.
In many children with pediatric cardiomyopathy, the disorder progresses to the point where medications and surgical treatment options are ineffective. In such cases, affected children may require a heart transplant, a form of open-heart surgery in which a severely diseased heart is replaced with a healthy donor heart. Pediatric cardiomyopathy is the leading cause of heart transplantation in children. A heart transplant is considered a last resort for individuals with end-stage heart failure. Drawbacks of heart transplantation include the potential for rejections and the limited availability of a suitable donor.
Genetic counseling may be of benefit for affected individuals and their families. Other treatment is symptomatic and supportive.
Numerous clinical studies related to pediatric cardiomyopathy are in progress. These studies are focused on improving diagnostic techniques, improving existing treatments options and developing new ones, and learning about various genetic aspects of cardiomyopathy such as locating disease genes. For more information on clinical trials dealing with cardiomyopathy, contact the Children’s Cardiomyopathy Foundation listed in the Resources section of this report or the National Institutes of Health (NIH) clinical trials web site: http://www.clinicaltrials.gov
The Dilated Cardiomyopathy Research Project aims to advance understanding of the genetics of dilated cardiomyopathy by combining clinical and genetic information from a large number of families.
For more information contact:
Dilated Cardiomyopathy Research Project
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: [email protected]
Some current clinical trials also are posted on the following page on the NORD website:
For information about clinical trials sponsored by private sources, contact:
For information about clinical trials conducted in Europe, contact:
Contact for additional information about pediatric cardiomyopathy:
Steven D. Colan, MD
Director of Clinical Research, Department of Cardiology
Boston Children’s Hospital
300 Longwood Avenue
Boston MA 02115
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