Cardiomyopathies are diseases of the heart muscle, also known as the myocardium, in which the actual muscle cells and surrounding tissues are sick.
Cardiomyopathies can be primary, meaning the sickness predominantly involves the heart. They can also be secondary, meaning the sickness is a result of another disease or toxin and may also affect many organ systems within the body, including the heart. Patients with cardiomyopathy will most commonly have a heart with normal anatomy.
Cardiologists classify cardiomyopathy into three categories:
- Dilated cardiomyopathy (DCM): Also known as congestive cardiomyopathy. Most notable for an enlarged heart that contracts poorly.
- Hypertrophic cardiomyopathy (HCM): Most notable for thickening of the heart muscle. Some physicians will refer to this class of cardiomyopathy as idiopathic hypertrophic subaortic stenosis (IHSS).Hypertrophy, or thickening, particularly of the left ventricle, can result in problems with obstruction to forward flow and problems with relaxation of the left ventricle, and can thereby affect the ability of the heart to fill. Children with hypertrophic cardiomyopathy are also at increased risk for arrhythmias.
- Restrictive cardiomyopathy (RCM): Most notable for abnormal relaxation of the ventricles and well preserved pumping function. As a result, the upper chambers of the heart, the atria, become enlarged while the lower pumping chambers, the ventricles, remain normal in size. This is a rare form of cardiomyopathy in children.
The cause of most cases of cardiomyopathy is unknown. Other causes include:
- A viral infection of the heart, or myocarditis, which weakens the heart muscle
- Hypertrophic cardiomyopathy can run in families and genetic causes have been identified
- There are several metabolic disorders as well as congenital muscle disorders that can lead to dilated cardiomyopathy
- A persistent rhythm abnormality can lead to weakening of the heart
- Problems of the coronary arteries, either congenital or acquired, can eventually lead to cardiomyopathy
Although there is a long list of possible causes of cardiomyopathy, few of them are directly treatable and most therapy is aimed at treating the secondary effects on the heart.
Dilated cardiomyopathy presents with signs and symptoms of congestive heart failure (CHF). Infants with this disease may demonstrate fast and heavy breathing with feedings, sweating with feedings, lethargy or inactivity, or poor weight gain. Older children may have difficulty with exercise, difficulty with breathing, abnormal heart beats, dizziness or weight loss due to nausea or decreased appetite.
Dilated cardiomyopathy is a serious disease that occurs with a spectrum of severity and outcome. Depending on the cause and the degree of irreversible damage to the heart muscle following the acute illness, about one-third of patients have persistent very poor heart function, one-third improve but are left with some heart dysfunction, and one-third recover completely. It is difficult to predict which category an individual patient will fall, therefore frequent cardiology follow-up is extremely important.
Patients who do have irreversible damage and persistent poor function may go on to require a heart transplant.
Restrictive cardiomyopathy is notable for increased work of breathing, often associated with a respiratory illness such as colds, bronchiolitis, and pneumonia. Other symptoms can include fatigue, dizziness and fainting. The patient may have an enlarged abdomen due to high pressure on the right side of the heart which causes a large liver and fluid buildup in the abdomen.
If the patient is critically ill, initial treatment may require lifesaving measures such as placement of a breathing tube and use of a mechanical ventilator. Acutely ill patients may require intravenous fluids and medications to improve blood pressure and heart function. The very sickest of patients may require placement on an artificial heart-lung machine called ECMO.
Diuretics are medications designed to remove excess fluid from the body. Blood thinners are used when clots develop within the poorly functioning heart chambers. Rhythm problems may develop from the dilated heart and medications to treat these abnormalities may be necessary.
Once the patient is more stable, long term therapy can involve a number of medications. Medications such as captopril and enalapril relax the arteries in the body, decreasing the blood pressure and consequently, the amount of work the heart has to perform to pump blood to the rest of the body. Common diuretics, like Lasix and Aldactone, are used to reduce the excess fluid in the lungs. Digoxin is an oral medication that improves the pumping function of the heart, as well as helping to prevent certain types of arrhythmias.
Research in adults has indicated that the use of a group of blood pressure medications called beta-blockers (propranolol, atenolol) has some long-term benefit and these are sometimes used in children.
Only 45 to 50 percent of patients with this type of cardiomyopathy are estimated to survive two years after the diagnosis. Some patients may also require heart or heart lung transplantation. However, the severity of these diseases can vary greatly and each child should be evaluated and treated on an individual basis.
Hypertrophic cardiomyopathy presents in a variety of ways. Infants can present with signs of congestive heart failure as noted above. Older children can demonstrate exercise intolerance, chest pain with exercise, palpitations, dizziness or passing out. Some children have no symptoms and are first brought to attention by the presence of a murmur, usually due to the obstruction to flow out of the ventricle or leaking of one of the valves of the heart. Often, the murmur is absent until they reach their teenage years, with such children remaining asymptomatic.
Patients with hypertrophic cardiomyopathy may initially have a lot of difficulty with arrhythmias. Patients may require antiarrhythmic medications or even electrical shock to stop these abnormal rhythms. These patients may require some of the same life saving treatments mentioned above.
In patients who have either had a life-threatening arrhythmia, which can arise from the thickened ventricle, or with risk factors for such arrhythmias, surgically placed devices can “shock” a patient immediately at the time of a life threatening event. Such devices are called ICDs (internal cardioverter/defibrillator). The more chronic treatment options for hypertrophic cardiomyopathy address both the problems of arrhythmia and obstruction to flow by the thickened heart muscle.
Treatment for outflow obstruction can include medications such as propranolol and verapamil, designed to slow the heart rate and “relax” the heart, thereby decreasing the obstruction. Diuretics and digoxin are not usually used in this type of cardiomyopathy as it can worsen the obstruction of blood flow out of the heart.
Patients with restrictive cardiomyopathy are at high risk for blood clots within the heart, particularly the enlarged upper chambers, therefore blood thinners such as heparin, coumadin or Lovenox may be necessary.
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
- Young age at presentation
- Family history of sudden death
- Marked heart thickening on echocardiogram
- 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.