Health Library

Cardiomyopathies

Cardiomyopathies are diseases of the heart muscle, also known as the myocardium, in which the actual heart muscle cells and heart tissues are sick.

Cardiomyopathies can be primary, meaning the sickness is only in the heart.

They can also be secondary, meaning the sickness is a result of another disease or toxin and may also affect other organs within the body, including the heart.

Patients with cardiomyopathy will most commonly have a heart that looks normal but does not work well.

What are Causes of Cardiomyopathy?

The cause of cardiomyopathy in most cases is unknown, also referred to as idiopathic. Some causes of cardiomyopathy may include:

• changes in a gene/DNA, where it may run in families
• a viral infection of the heart, or myocarditis, which weakens the heart muscle
• metabolic disorder and inherited muscle disorders
• problems of the coronary arteries, either present at birth or appearing later

There are many possible causes of cardiomyopathy, but few are directly treatable, and most therapy is done to treat the secondary effects on the heart.

There are other less common forms of cardiomyopathy that can be caused by hormone deficiencies, chronic medical conditions, and heart rhythm problems. As part of the evaluation for cardiomyopathy, detailed medical and family histories are taken to find the cause of cardiomyopathy.

What are Symptoms of Cardiomyopathy?

Cardiomyopathy can show up in children in many ways. Some children have no symptoms and are asked to see a cardiologist because heart disease runs in their family, their doctor notices a change in their physical exam, or because of an abnormal test that was done for another reason. A child could also have signs and symptoms of congestive heart failure (CHF). In some very rare cases, a sudden cardiac event related to an abnormal heart rhythm may be the first sign of a heart problem in a child.

Infants with cardiomyopathy may have:

• fast and heavy breathing at rest or with feedings
• feedings that take longer than normal
• sweating with feedings
• increased tiredness or inactivity
• poor weight gain

Common symptoms in older children and adolescents are:

• abdominal pain
• nausea/vomiting
• decreased appetite
• chest pain
• trouble exercising or cannot keep up with other children their age
• trouble breathing
• cough
• swelling in face, belly or legs
• abnormal heart beats or palpitations
• dizziness
• passing out (passing out during exercise is a serious concern and children should be seen by a cardiologist)

How is Cardiomyopathy Diagnosed?

Physical Exam

A child’s health history and physical examination are key in making a cardiomyopathy diagnosis. Signs of congestive heart failure, such as fast breathing and fast heart rate, abnormal lung and heart sounds, and an enlarged liver can help the doctor make the right diagnosis.

A murmur or abnormal chest wall impulses can be found in cardiomyopathy. A murmur is heard with certain types of cardiomyopathy from blocked blood flow leaving the heart or leaking of one of the valves of the heart. If a child does not have a murmur, this does not mean they do not have cardiomyopathy. Parents and siblings of a child with cardiomyopathy may also be asked to see a cardiologist even if they have no signs or symptoms.

Tests to Help with Diagnosis Include:

• An electrocardiogram (EKG) checks the rhythm of the heart.
• An echocardiogram is an ultrasound of the heart. This test looks at the size and shape of the heart and how well the heart is squeezing/pumping.
• Magnetic resonance Imaging (MRI) is another way to look at the size, shape and function of the heart and may be done instead of the echocardiogram. Intravenous (IV) contrast is sometimes given to better look at the heart muscle itself.
• A chest X-ray is sometimes used to screen for cardiac disease and can show an enlarged heart and extra fluid in the lungs (also referred to as pulmonary edema).
• A cardiopulmonary exercise test is done on a treadmill or a bike for older children and teens. This helps to assess how well a child can exercise, and looks at the heart rhythm, heart rate and blood pressure with exercise.
• A heart monitor is another test to monitor heart rhythm. They are worn on the chest for 24 hours up to 30 days and help track abnormal heart rhythms.
• A cardiac catheterization may also be done, not only to evaluate the pressures within each chamber of the heart but also to evaluate the blood vessels. Sometimes small pieces of heart muscle are also taken during the cardiac catheterization for laboratory study; this is called a biopsy. Heart muscle biopsies are helpful in looking for possible infections of the heart, as well as certain other types of changes in the heart muscle.

What are the Types of Cardiomyopathy?

Cardiologists group cardiomyopathy into five categories:

1. Dilated cardiomyopathy (DCM): Also known as congestive cardiomyopathy. Dilated cardiomyopathy is the most common form of cardiomyopathy in children. In DCM, the heart becomes enlarged and does not work well.
2. Hypertrophic cardiomyopathy (HCM): With hypertrophic cardiomyopathy, the heart muscle is thickened. Another name for this is idiopathic hypertrophic subaortic stenosis (IHSS).
   Thickening of the heart muscle, particularly the walls of the left side of the heart, can make it hard for blood to flow through the heart and for the heart to relax. Children with hypertrophic cardiomyopathy are also at increased risk for abnormal heart rhythms.
3. Restrictive cardiomyopathy (RCM): With restrictive cardiomyopathy, the pumping chamber or ventricle does not relax very well. So blood backs up into the upper chambers of the heart, or atria, and they become enlarged or bigger, while the lower pumping chambers, the ventricles, stay normal in size. There is also a risk for abnormal heart rhythms.
4. Left Ventricular Non-Compaction (LVNC): On an echocardiogram, the heart muscle looks coarse and marked with fingerlike projections called trabeculations. It looks rough and jagged instead of smooth and compact. It may be related to other forms of congenital heart disease but can happen on its own. A few patients may go on to have poor function and heart failure.
5. Arrhythmogenic Cardiomyopathy (ACM): The muscle of the heart is replaced by fat tissue over time and leads to dangerous heart rhythms. This form of cardiomyopathy is often hard to diagnose and can affect the right and/or left side of the heart. It is usually first found when the patient has an abnormal rhythm. This is also sometimes referred to as arrhythmogenic right ventricular cardiomyopathy (ARVC), arrhythmogenic right ventricular dysplasia (ARVD), or arrhythmogenic left ventricular cardiomyopathy (ALVC).

How is Cardiomyopathy Treated?

Treatment of children with cardiomyopathies can be divided into immediate and long-term time frames.

Immediate Care

If a child is critically ill, treatment can require lifesaving measures such as placement of a breathing tube and use of a mechanical ventilator. Acutely ill patients may need IV fluids and medicines to improve blood pressure, heart function, and heart rhythms. If a child is very sick, they may need to have help from an artificial heart-lung machine called ECMO. A ventricular assist device may also be used if heart function remains poor.

In patients who have had a life-threatening heart rhythm related to their cardiomyopathy, surgically placed devices can "shock" a patient instantly at the time of a life-threatening event. These devices are called ICDs (internal cardioverter/defibrillator).

Long-Term Care

Once a child is more stable, long-term care can include the use of medicines and frequent visits and testing. Different kinds of medicines can be used depending on the type of cardiomyopathy. Blood pressure medicines such as ace inhibitors (ACEi) and beta blockers are often used if the heart is not squeezing well, as is the case with DCM. Diuretics are medicines that help remove extra fluid from the body. Blood thinners are used when clots form within the heart.

Depending on a child’s risk for an abnormal heart rhythm related to their cardiomyopathy, an ICD may be placed.

Hypertrophic Cardiomyopathy

Immediate Care

Patients with hypertrophic cardiomyopathy may have trouble with abnormal, fast heart rates. They may need medicines to slow their heart rate (beta-blockers) or even electrical shock to stop these abnormal rhythms. These patients may also need some of the same lifesaving treatments mentioned above.

Long-Term Care

Ongoing treatment options for hypertrophic cardiomyopathy address both the heart rhythm problems and blood flow problems. Treatment for outflow blockage can include medicines such as beta blockers (atenolol, metoprolol) and calcium channel blockers (verapamil), that slow the heart rate and "relax" the heart, decreasing the obstruction. There are some newer medications called myosin inhibitors that are used to treat people with HCM. These medications are not yet used in people under 18 years old.

Restrictive Cardiomyopathy

Immediate and Long-Term Care

Patients with restrictive cardiomyopathy are at high risk for blood clots within the heart, particularly the enlarged upper chambers. Blood thinners such as aspirin, coumadin (warfarin) or Lovenox may be needed. Gentle use of diuretics can also help some patients. Internal Cardioverter / Defibrillators (ICDs) are also used because these patients are at risk for sudden cardiac arrest related to fast or slow rhythms.

Arrhythmogenic Cardiomyopathy

Immediate and Long-Term Care

Patients with ACM can benefit from treatment with medicines to limit abnormal rhythms. Treatment also consists of placement of an ICD to protect against sudden cardiac events such as a cardiac arrest. In certain cases, a catheter-based procedure to stop the abnormal rhythm can be done.

Long-Term Outlook for Children with Cardiomyopathy

Dilated cardiomyopathy (DCM) is a serious disease. But like most diseases, dilated cardiomyopathy has a wide range of severity and outcomes.

For patients with dilated cardiomyopathy and heart failure from viral illnesses or myocarditis, about one-third have ongoing poor heart function, one-third improve but are left with some heart dysfunction, and one-third recover completely. It is hard to predict in which category an individual patient will fall. This is why frequent cardiology follow-up is important. Patients who have irreversible damage and persistent poor function may go on to need a heart transplant.

The exact number of patients with hypertrophic cardiomyopathy is unknown, as some patients have no symptoms. The chance of premature death is estimated to be less than 1%. Risk factors for sudden death include episodes of passing out, diagnosis at a young age, family history of sudden death, marked heart thickening on echocardiogram, and fast heart rhythms seen on monitoring. In less than 5% of patients, late complications can include enlargement of the left ventricle and decreased pumping function.

As restrictive cardiomyopathy accounts for only 5% of patients with cardiomyopathy, the total number of patients with this disease is small and the overall outcome data is limited. Unfortunately, the available information shows that the outlook is poor. Only 45% to 50% of patients with this type of cardiomyopathy are estimated to survive two years after the diagnosis. These patients are typically referred early to heart transplant, before they get other symptoms from their heart disease.

Left ventricular non-compaction can show up in different ways, and some patients never go on to develop heart disease. It is important to know the family history to find those patients at risk of developing heart disease, but most patients are found without knowing a family connection. Regular visits to a cardiologist are needed to find any changes in heart function.

The outcome for arrhythmogenic cardiomyopathy is hard to assess due to its rare nature and late diagnosis. How the condition is first discovered, for example after a cardiac arrest or due to family history, can influence the course of the disease.