Restrictive cardiomyopathy is a condition in which the heart cannot fill properly, resulting in possibly severe malfunction and heart failure. Restrictive cardiomyopathy is distinguished from the more common dilated cardiomyopathy and hypertrophic cardiomyopathy because the heart ventricles stay a normal size and continues to function normally during the contraction phase. The problem arises, however, during the filling phase, or diastolic phase. In a heart afflicted with restrictive cardiomyopathy, the muscular walls of the heart are rigid and cannot expand when the heart should be filling with blood. As a result, blood pressure rises in the ventricles and the amount of blood pumped to the body is reduced. Also, the upper chambers of the heart, or atria, may expand.
This condition is relatively rare. It may be caused by certain other illnesses, infiltration of the heart by abnormal substance (e.g., amyloid, iron), exposure to radiation, or unknown factors. The disease is called restrictive cardiomyopathy for the following reasons:
Restrictive refers to the reduced amount of blood that can fill the lower chambers of the heart (the ventricles) because their walls are too rigid.
Cardiomyopathy is a disease in which the heart is abnormally enlarged, thickened and/or stiffened. As a result, the heart cannot efficiently receive or pump blood as well as it should.
The most common sign of restrictive cardiomyopathy is heart failure, which can cause shortness of breath, arrhythmias and general weakness. The symptoms often occur during physical activity when the body's demand for oxygen-rich blood rises. Various diagnostic tests can used to detect the presence of restrictive cardiomyopathy, including electrocardiogram, chest x-ray and echocardiogram. In some cases, a biopsy of the heart muscle may be conducted to rule out other cardiac conditions
Treatment for this condition is difficult. It generally involves taking medication and making healthy lifestyle changes to reduce the risk of heart failure. If abnormal heart rhythms (arrhythmias) are present and cannot be controlled by medication, the patient may benefit from the surgical insertion of a pacemaker or implantable cardioverter defibrillator. In very severe cases, heart transplantation may be recommended.
About restrictive cardiomyopathy
The least common of the cardiomyopathies, restrictive cardiomyopathy is a condition in which the walls of the lower chambers (ventricles) are abnormally rigid, but not necessarily thickened or enlarged. These rigid walls lack the flexibility to expand as the ventricles fill with blood. Restrictive cardiomyopathies are characterized by normal ejection fractions (50 to 70 percent), but the pressure within the ventricle remains high through the relaxation phase of the heartbeat, due to increased stiffness of the ventricular walls. As a result, it is known as a diastolic cardiomyopathy, or one that affects the relaxation phase of the heart cycle.
Although the cause of restrictive cardiomyopathy is sometimes unknown (idiopathic), known causes include:
Buildup of fat and proteins (amyloidosis) around the heart muscle, a condition that is frequently inherited, but may be associated with acquired diseases such as multiple myeloma and chronic infections.
Iron overload (hemochromatosis) in the heart, a condition that may be inherited or may be the result of another condition that required multiple blood transfusions (e.g. Cooley’s anemia) and later resulted in iron overload and restrictive cardiomyopathy
Scarring of the heart from illness or open-heart surgery.
Chest exposure to radiation or chemotherapy.
Inflammation of the inner lining of the heart due to abnormal activity of eosinophils (a type of white blood cell), a condition known as hypereosinophilic syndrome.
Connective tissue diseases or various other illnesses.
Although restrictive cardiomyopathy is rare in the United States, it is a somewhat more common cause of death in the tropics, including Africa, India, South and Central America, because of the higher prevalence of endomyocardial fibrosis, a disease of the heart lining.
Signs of restrictive cardiomyopathy
The typical sign of a restrictive cardiomyopathy is heart failure. The primary symptoms of heart failure are:
Shortness of breath
Palpitations
Arrhythmia
Swelling of lower extremities (edema)
Abdominal distension (ascites)
Fatigue
General weakness
These symptoms tend to occur during physical activity. This is because the heart with restrictive cardiomyopathy has difficulty delivering oxygen-rich blood during exertion and the pressure within the heart chambers tend to rise. At rest, the heart is still able to pump oxygenated blood. Symptoms may include:
Nausea or upset stomach
Loss of appetite
Symptoms of the underlying disease process such as amyloid and iron deposits in other organs
Diagnosis of restrictive cardiomyopathy
The first step that a physician will take when diagnosing a restrictive cardiomyopathy is to obtain the patient’s personal and family medical history. Although restrictive cardiomyopathy does not appear to run in families, it will be important to note any history of trauma, radiation therapy or chemotherapy.
The patient will also be given a complete physical examination. As part of this examination, the physician will listen for crackles in the patient’s lungs (rales) or other unusual heart sounds. The physician will also take the patient’s blood pressure and may detect a type of high blood pressure called diastolic hypertension. Next, the physician may order one or more diagnostic tests to look for any stiffening of the ventricular walls or other signs of a restrictive cardiomyopathy. These tests include:
Electrocardiogram. A painless test that measures the heart’s electrical activity, aiding in the assessment of any abnormal heart rhythms (arrhythmias).
Chest x-ray. A painless radiation-based imaging test that offers the physician a picture of the general size, shape, and structure of the heart and lungs.
Echocardiogram. The most common test used to diagnose cardiomyopathy, echocardiogram is a painless test that uses sound waves to visualize the structures and functions of the heart. A moving image of the patient’s beating heart is displayed on a video screen, where a physician can study the heart’s thickness, size and function. From this image, a physician can measure the heart’s size and pumping, which tend to be abnormal in people with cardiomyopathies. The image also shows the motion pattern and structure of the four heart valves, revealing any potential leakage (regurgitation) or narrowing (stenosis). During this test, a Doppler ultrasound may be done to evaluate cardiac blood flow and the relaxation properties of the heart (known as diastolic function).
Computed tomography (CT) scan. Also known as a CAT scan, this painless test allows for multiple x-rays to be taken from different angles around the patient. With the help of a computer, a three-dimensional image can be created.
Blood tests. A recently developed test is capable of measuring the levels of the cardiac hormone brain natriuretic peptide (BNP). BNP is naturally produced by cardiac muscle, but excessive amounts are present in response to heart failure. Iron levels are measured when hemochromatosis is suspected.
In some cases, the physician may need to order more invasive tests, such as a biopsy of the heart, to tell the difference between a restrictive cardiomyopathy and constrictive pericarditis. It is important that constrictive pericarditis (which simulates restrictive cardiomyopathy) be ruled out. This is because constrictive pericarditis can be cured by surgery, whereas restrictive cardiomyopathy can only be controlled with medications. Rarely, surgery may be needed to confirm a diagnosis.
Treatment and prevention
Treatment for this condition is very challenging. The goal of therapy is to help treat heart failureas well as the underlying disease process, such as chelation of iron excess. Drugs typically used to fulfill this objective include diuretics (which help to flush excess fluids from the body and are used to control high venous blood pressure). Other medications may include:
Calcium channel blockers. To improve diastolic function.
Beta blockers. To help control heart rate.
ACE inhibitors. To improve diastolic function
In some cases, a pacemaker or implantable cardioverter defibrillator may be needed to control arrhythmias. In very severe cases, heart transplantation may be recommended. Since there is no definitive cause for a restrictive cardiomyopathy, there are no known prevention strategies.
Questions for your doctor
Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to restrictive cardiomyopathy:
Why do you suspect that I have restrictive cardiomyopathy?
How does this condition compare to other cardiomyopathies?
What tests will be used to diagnose the condition?
How soon do I need to have the tests?
What type of treatment do you recommend I use to treat this condition?
What medications will I be prescribed?
What are the risks with these medications?
How quickly will I see improvement once I have started my treatment?
What lifestyle changes may help my condition?
Will I need long-term treatment for this condition?
Could this condition be caused by any of the medications I am currently taking?
Could any of the medications I am currently taking interfere with your recommended treatment?
If I have restrictive cardiomyopathy do my children have an increased chance of developing this condition?
