What is cardiomyopathy?
Cardiomyopathy is diseased heart muscle that cannot function (contract) adequately. Cardiomyopathy results in the failure of the heart muscle to meet the needs of the body for oxygen rich blood and removal of carbon dioxide and other waste products. There are many causes of cardiomyopathy, but the end result is a heart that is weak and cannot maintain a normal ejection fraction or cardiac output.
How does the heart function?
The heart is an electrically-innervated, muscular pump that pushes blood throughout the body through blood vessels. A specialized group of cells located in the upper chamber (atrium) of the heart, acts as a pacemaker that generates an electrical impulse. This impulse begins a sequential electrical stimulation of heart muscle that then contracts in a coordinated way. Accordingly, first the upper chamber of the heart is stimulated to contract and send blood into the lower chambers (ventricles) of the heart. There is a slight delay in the electrical signal that allows the ventricles to fill. Then the ventricles contract pumping blood throughout the body. Another slight delay then occurs, allowing blood to return to the upper chambers of the heart, refilling the heart for the next cycle.
Cardiac output is a measurement of heart function that measures the amount of blood that the heart pumps in a specific period of time.
- The stroke volume is the amount of blood that the heart pumps with one contraction.
- The stroke volume multiplied by the number of heart beats per minute is the cardiac output.
- Normally, the adult heart pumps about 5 liters of blood through the blood vessels of the body every minute.
The ejection fraction is a measurement of the heart's effectiveness in pumping blood. It is the percentage of blood in a filled ventricle that is pumped out of the heart with each contraction. A normal heart will have an ejection fraction of 60%-70%. This number can decrease if the heart muscle cannot squeeze or contract adequately.
What are the signs and symptoms of cardiomyopathy?
When the heart fails to contract properly oxygenated blood is not pumped adequately to the tissues and organs of the body. This inability to deliver oxygen to body tissues can lead to generalized weakness and fatigue. Other symptoms may include shortness of breath on exertion or chest pain.
If there is an electrical rhythm disturbance associated with the cardiomyopathy, abnormal heartbeats may cause palpitations and the sensation of an occasional skipped heart beat or lethal heart rhythms, such as ventricular fibrillation.
Over a period of time, cardiomyopathy can lead to significant decrease in ejection fraction and cardiac output leading to heart failure. Symptoms may include increasing shortness of breath and swelling of the feet, ankles, and legs.
What causes cardiomyopathy?
There are many causes of cardiomyopathy that can be categorized in several ways. One method of defining cardiomyopathy is based on the official definition by the American Heart Association (see below), which are broken into two categories, primary and secondary. Another method of categorizing cardiomyopathy causes are extrinsic and intrinsic (which are more commonly used when discussing the disease with patients, family, and caregivers) and are discussed later in this article.
The official definition of cardiomyopathy of the American Heart Association in 2006 is as follows:
"Cardiomyopathies are a heterogeneous group of diseases of the myocardium associated with mechanical and/or electrical dysfunction that usually (but not invariably) exhibit inappropriate ventricular hypertrophy or dilatation and are due to a variety of causes that frequently are genetic. Cardiomyopathies either are confined to the heart or are part of generalized systemic disorders, which may lead to cardiovascular death or progressive heart failure-related disability."
The definition divides heart disease into:
- Primary cardiomyopathies, those that usually affect the heart alone (primary). The primary cardiomyopathies are further divided into inherited (genetic) diseases, those that are acquired, and those that are a combination of both.
- Secondary cardiomyopathies, those that are a result of an underlying condition affecting many areas of the body.
What causes primary cardiomyopathy?
Some of the causes are of primary cardiomyopathy are:
- Hypertrophic cardiomyopathy
- Ion conduction abnormalities
- Prolonged QT syndrome
- Brugada syndrome
- dilated cardiomyopathy
- restrictive cardiomyopathy
- inflammatory myocarditis
- physically and physiologically stress induced (tako-tsubo syndrome or "broken heart syndrome")
What causes secondary cardiomyopathy?
Some of the causes are of primary cardiomyopathy are:
- Gaucher disease
- drugs/ Alcohol
- heavy metals
- Noonan syndrome
- Nutritional deficiencies
- Autoimmune and collagen disease
- Electrolyte imbalance
- Cancer therapy complications
What causes extrinsic and intrinsic cardiomyopathies?
As previously mentioned, another method of categorizing cardiomyopathy causes are extrinsic and intrinsic (which are more commonly used when discussing the disease with patients, family, and caregivers). Extrinsic and intrinsic causes of cardiomyopathies are discussed below.
- Extrinsic cardiomyopathies: Extrinsic cardiomyopathies are those that are due to diseases that are not uniquely due to heart muscle cell abnormalities
- Intrinsic cardiomyopathies: Intrinsic cardiomyopathies are due to abnormalities that originate in the heart muscle cell.
Examples of extrinsic cardiomyopathies include:
- Ischemic cardiomyopathy is a disease of heart muscle due to inadequate blood supply to heart muscle and is a common cause of cardiomyopathy. When blood vessels to heart muscle become blocked, heart muscle cells can be deprived of oxygen and fail to function normally. An example of this is a heart attack, where a complete blockage of a blood vessel causes muscle cells to die, decreases the total amount of muscle that can contract and cardiac output is compromised.
- Poorly controlled high blood pressure (hypertension) can lead to abnormally functioning heart muscle.
- Alcohol abuse
Examples of extrinsic cardiomyopathies include:
- Amyloidosis can infiltrate heart cells with amyloid protein.
- Sarcoidosis can cause heart cell inflammation.
- Viral infections may cause inflammation of heart muscle (myocarditis) with temporary or potentially permanent damage to heart muscles cells leading to a secondary cardiomyopathy.
- Dilated cardiomyopathies occur when the heart muscle fibers are abnormally stretched when the heart chambers increase in size and volume. The stretched muscles lose their ability to contract strongly, similar to a slinky or an elastic band that has been overstretched and loses its shape and function. As the heart walls continue to stretch, they can also cause damage to the heart valves between the chambers of the heart causing blood to regurgitate or backwash, and as a result there is decreased cardiac output and heart failure. There are many causes of dilated cardiomyopathy including:
- cancer therapies,
- chemical poisonings (for example, lead and arsenic),
- neuromuscular disorders such as muscular dystrophy, and
- a variety of genetic diseases.
- Hypertrophic cardiomyopathy is a genetic or familial disease where muscle in the left ventricle has a predisposition to thicken and prevent normal flow of blood out of the heart. Hypertrophic cardiomyopathy is the most common cause of sudden death in young people, such as exercising athletes.
- Peripartum cardiomyopathy is seen late in the third trimester of pregnancy, though it can continue to be a potential cause of cardiomyopathy for five months post-partum. It is more common in obese older
pregnant women who develop preeclampsia.
How is cardiomyopathy diagnosed?
The diagnosis of cardiomyopathy begins with history. Usually, the patient's symptoms consist of complaining of fatigue, weakness, and shortness of breath. There also may be chest discomfort. Other information may be gathered from past medical history including history of high blood pressure, high cholesterol, and diabetes. Noting the presence of other underlying illnesses such as sarcoidosis, amyloidosis, thyroid disorders, and rheumatoid arthritis can be helpful in determining potential causes of cardiomyopathy.
Social history including smoking, alcohol, and drug abuse can also be helpful in making the diagnosis. Family history is often important, especially if there is concern about sudden cardiac death at an early age.
Physical examination often will include monitoring vital signs including heart rate, blood pressure, respiratory rate, and oxygen saturation. The health care practitioner may obtain significant information from lung examination listening for fluid and from listening to the heart sounds. Murmurs may provide information about leaking heart valves. Examination of the jugular veins in the neck and swelling or fluid in the feet and ankles can be clues to the diagnosis of heart failure.
Blood tests may be helpful in screening for anemia, abnormalities in electrolytes, and kidney and liver function. Other blood tests and lab work may be ordered depending upon the clinical situation.
An electrocardiogram (EKG) is a screening test to look for electrical abnormalities in the heart. Evidence of previous heart attack or ventricular hypertrophy (heart muscle thickening) can be noted on the EKG.
An ultrasound of the heart (echocardiogram) can help evaluate wall motion function of the heart, the integrity of the heart valves, and the ventricle ejection fraction. It may also provide visualization of the sac (pericardium) that surrounds the heart.
Chest X-ray may reveal an enlarged or abnormal heart shape or excess fluid accumulation within the lungs.
When to seek medical care for cardiomyopathy
It is not normal to have chest pain or shortness of breath and persons experiencing these symptoms should seek medical care.
Swelling of the feet, ankles, and legs; increasing shortness of breath on exertion; difficulty lying flat and wakening in the middle of the night due to shortness of breath all may be symptoms of congestive heart failure. These symptoms should prompt a consultation with a health care practitioner.
It is also not normal to ever be partially or completely unconscious. A person who faints or passes out due to a heart rhythm disturbance may be in a life-threatening situation. It may be necessary for bystanders to activate the emergency medical services, usually by phone calling 911.
What is the treatment for cardiomyopathy?
While the treatment of a cardiomyopathy depends upon the specific cause, the goal for therapy is to maximize cardiac output, maintain ejection fraction, and prevent further heart muscle damage and loss of function.
If the cardiomyopathy is associated with electrical disturbances, heart pacemakers may be implanted to provide stable, coordinated electrical impulses to the heart muscle.
If there is a potential for sudden cardiac death, an implanted defibrillator may be considered. The device can recognize ventricular fibrillation, a rhythm that does not allow the heart to contract, and deliver an electrical shock to return the heart to a coordinated stable rhythm. If indicated, there are some implanted devices that are both pacemakers and defibrillators.
Severe cardiomyopathies may not be able to be controlled or treated with mediation, diet, or other surgical interventions. In this situation, heart transplantation may be a consideration as a final option.
What medications treat cardiomyopathies?
Medications prescribed to the patient will depend upon the underlying reason that caused the cardiomyopathy.
If appropriate, angiotensin converting enzyme (ACE) inhibitors and beta blocker medications may be used to allow the heart to beat more efficiently, potentially increasing cardiac output.
When congestive heart failure symptoms exist, diuretics in association with diet changes and salt restriction may be used to prevent water retention and decrease the workload of the heart.
Do I need to follow-up with my doctor after being diagnosed and treated for
Patients with cardiomyopathy often need lifetime care to monitor their heart function. Control of symptoms can be key to optimal outcome.
Blood tests may be needed to monitor medications and other markers in the body.
Echocardiograms and ultrasounds can be used to assess heart function including valve anatomy, ejection fraction, and function of the contraction of the atrium and ventricle walls.
As with all long-term illnesses, consistent monitoring is prudent.
Can cardiomyopathy be prevented?
Cardiomyopathy is a term that describes the end result of many diseases and illnesses. The type of heart muscle damage that occurs and the subsequent decrease in the pumping capability of the heart depends upon the injury, the amount of damage to the heart, and the potential for recovery.
Some cardiomyopathies are completely preventable, for example alcoholic cardiomyopathy due to long-term excessive alcohol consumption. Others are unavoidable such as cardiomyopathy due to a viral infection.
Living a healthy lifestyle will help minimize the risk of developing some cardiomyopathies. This includes maintaining a healthy, balanced diet and pursuing a routine exercise regimen, For ischemic cardiomyopathy, risk reduction includes life-long control of high blood pressure, high cholesterol, and diabetes.
In patients who are at risk for genetic cardiomyopathy such as hypertrophic cardiomyopathy, screening echocardiograms may be advisable to prevent sudden cardiac death.
What is the outlook for a person with cardiomyopathy?
Cardiomyopathy is a prevalent disease. In the United States, up to a half million people develop a dilated cardiomyopathy every year. Ischemic cardiomyopathy may be present in up to 1% of the population. Because cardiomyopathy tends to be progressive, mortality depends upon the amount of heart pumping function loss; and one goal of therapy is to slow the rate of this loss.
Research on new medical and surgical treatments continues, ranging from new medications, stem cell research, and innovative types of implantable heart assist devices. Ongoing clinical trials for patients with cardiomyopathies are being conducted by the National Institutes of Health.