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 the genetic code or DNA, where it may run in families
- A viral infection of the heart, or myocarditis, which weakens the heart muscle
- Metabolic disorder as well as inherited muscle disorders
- Problems of the coronary arteries, either present at birth or acquired
Although there is a long list of possible causes of cardiomyopathy, few are directly treatable and most therapy is aimed at treating 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.
Children with cardiomyopathy can present in a variety of 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 apetite
- Chest pain
- Trouble exercising or are not able to keep up with other children their age
- Trouble breathing
- Swelling in face, belly, or legs
- Abnormal heartbeats or palpitations
- Passing out (passing out during exercise is a serious concern and children should be seen by a cardiologist)
Diagnosis of Cardiomyopathy
For all children thought to have cardiomyopathy, the history and physical examination are key in making the 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, but their absence does not rule out the diagnosis.
A murmur or abnormal chest wall impulses can be found in cardiomyopathy With certain types of cardiomyopathy a murmur can be due to the obstruction of 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.
Test to Help with Diagnosis Include:
- An electrocardiogram (EKG) to check 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 adolescents. This helps to assess how well a child can exercise and looks at the heart rhythm, heart rate, and blood pressure with exercise.
- A holter or event monitor are other tests to monitor heart rhythm. They are worn on the chest for 24 hours up to 30 days and help assess for abnormal heart rhythms.
- A cardiac catheterization may also be performed, not only to evaluate the pressures within each chamber of the heart, but may also evaluate the coronary arteries. Sometimes small pieces of heart muscle are also taken during the cardiac catheterization for laboratory study - this is called a biopsy. Such heart muscle biopsies are helpful in the evaluation of possible infections of the heart, as well as certain metabolic abnormalities of the heart.
Types of Cardiomyopathy
Cardiologists group cardiomyopathy into five categories:
- Dilated cardiomyopathy (DCM), also known as congestive cardiomyopathy: Dilated cardiomyopathy is the most common form of cardiomyopathy in children, and ischemic cardiomyopathy is the most common type of dilated cardiomyopathy. In DCM, the heart becomes enlarged and does not work well.
- 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 fully relax. Children with hypertrophic cardiomyopathy are also at increased risk for abnormal heart rhythms
- Restrictive cardiomyopathy (RCM): With restrictive cardiomyopathy, the pumping chamber or ventricle is not able to relax very well. As a result, 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, remain normal in size. There is also a risk for abnormal heart rhythms.
- Left ventricular non-compaction (LVNC): On echocardiogram, the heart muscle appears coarse and marked with fingerlike projections called trabeculations. It appears coarse and jagged instead of smooth and compact. It may be related to other forms of congenital heart disease but can occur on its own. A few patients may go on to have poor function and heart failure.
- Arrhythmogenic right ventricular dysplasia (ARVD): 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) or arrhythmogenic right ventricular dysplasia (ARVD).
Treatment of Cardiomyopathy
Treatment of children with cardiomyopathies may best be divided into immediate and long-term time frames.
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.
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. Such devices are called ICDs (internal cardioverter / defibrillator).
Once a child is more stable, long-term care can involve a number of strategies including 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 such as Lasix are medicines designed to remove extra fluid from the body. Blood thinners are used when clots form within the heart.
Assessment of a child’s risk for an abnormal heart rhythm related to their cardiomyopathy and an ICD may be a planned procedure .
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.
The more chronic treatment options for hypertrophic cardiomyopathy address both the heart rhythm problems and obstruction of flow problems. Treatment for outflow obstruction can include medicines such as beta blockers (atenolol, metoprolol) and calcium channel blockers (verapamil), designed to slow the heart rate and "relax" the heart, thereby decreasing the obstruction.
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.
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 eliminate the abnormal rhythm can be performed.
Long-Term Outlook for Children with Cardiomyopathy
Dilated cardiomyopathy (DCM) is a serious disease. However, like most diseases, dilated cardiomyopathy occurs with a spectrum of severity and outcomes.
For patients with DCM and heart failure from viral illnesses or myocarditis, about one-third have persistent poor heart function, one-third improve but are left with some heart dysfunction, and one-third recover completely. It is hard to predict into 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 require 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 percent. 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 percent of patients, late complications can include enlargement of the left ventricle and decreased pumping function.
As restrictive cardiomyopathy accounts for only 5 percent 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 indicates that prognosis is poor. Only 45 percent to 50 percent 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 present in different ways and some patients never go on to develop heart disease. Family history in these cases is important to find those patients at risk of developing heart disease but most patients are found in isolation. Regular visits to a cardiologist are necessary to find any changes in heart function.
The outcome for ARVD is hard to assess due to its rare nature and late diagnosis. How the patient initially presents, for example after a cardiac arrest or due to family history, can influence the course of the disease.