What is Restrictive Cardiomyopathy?
Restrictive cardiomyopathy (RCM) is a type of heart disease where the heart is unable to stretch and fill with blood properly due to the stiffening of its walls. But, even though the heart’s walls are stiff, the size of the heart stays normal. There are different types of restrictive cardiomyopathies, and they all have different causes, symptoms, ways to diagnose them, treatments, and outcomes. Three of the most common causes of RCM are heart conditions called cardiac amyloidosis, cardiac sarcoidosis, and cardiac hemochromatosis. This article will provide a detailed overview of RCM, focusing specifically on these three main causes.
What Causes Restrictive Cardiomyopathy?
Restrictive cardiomyopathy is a heart condition that occurs for a number of reasons, including diseases like infiltrative diseases, storage diseases, and various other systemic diseases. Infiltrative diseases are illnesses that cause a substance to build up in your heart muscle. Examples of these diseases include amyloidosis, sarcoidosis, hereditary hemochromatosis, and primary hyperoxaluria. Amyloidosis is the most common type of infiltrative disease.
Storage diseases are rare diseases you’re born with that cause problems with your body’s metabolism. Storage diseases include Anderson-Fabry disease, Gaucher disease, glycogen storage disease, Hurler cardiomyopathy (also known as mucopolysaccharidosis type II), Niemann-Pick disease, Danon disease, and Friedrich ataxia.
Several other systemic diseases can also lead to restrictive cardiomyopathy. Some of these include diabetes, scleroderma, myofibrillar myopathies, pseudoxanthoma elasticum, Werner syndrome, sarcomeric protein disorders, carcinoid cardiomyopathy, idiopathic fibrosis, hypereosinophilic fibrosis, chronic eosinophilic leukemia fibrosis, endocardial fibroelastosis, and metastatic malignancies, which are cancers that have spread from their original location to the heart.
Other causes of restrictive cardiomyopathy include idiopathic causes (which means we don’t know why they occur), including radiation therapy and various drugs. Some drugs that are known to potentially cause restrictive cardiomyopathy include anthracycline, busulfan, ergotamines, methysergide, mercurial agents, and serotonin-containing agents.
Risk Factors and Frequency for Restrictive Cardiomyopathy
Restrictive cardiomyopathy (RCM) is quite rare but it accounts for approximately 5% of all cases of cardiomyopathy, a range of diseases affecting the heart muscle. There are three main types, including dilated, hypertrophic, and restrictive cardiomyopathy. Of these, RCM is the least common. Most people acquire RCM rather than inheriting it. The occurrence of RCM depends on factors like where you live, your ethnicity, your age, and your gender. Some specific causes of RCM and their statistics are:
- Amyloidosis: This is the top cause of RCM in the United States. It affects both men and women equally. There are several types of amyloidosis, with AL amyloidosis being the most common type causing RCM. Wild-type transthyretin amyloidosis typically affects older adults. Conversely, the V1221 mutant transthyretin variant is linked to a higher rate of symptomatic heart failure.
- Sarcoidosis: This cause of RCM affects women more than men, especially black women. Overall, the highest numbers of sarcoidosis cases are recorded in Japan.
- Hemochromatosis: This condition affects men and women equally. Around 1 in 200 people have this condition. Although both genders can get it, men are more likely to develop cirrhosis as a complication. The most common gene mutation connected with hemochromatosis is HFE C282Y, which is inherited in an autosomal recessive pattern. The H63D mutation is also commonly seen in this condition.
- Loffler’s Endocarditis: This is common in tropical climates and Sub-Saharan Africa, where it contributes to up to 20% of heart failure cases.
Other causes of RCM exist, each with variances in factors like prevalence, location, gender presentation, and associated genetic mutations. However, these causes are not detailed here as they are even rarer. If the causes listed above don’t align with a patient’s diagnosis, seeking a specialist’s advice is recommended.
Signs and Symptoms of Restrictive Cardiomyopathy
Restrictive cardiomyopathy (RCM) is a heart disease that can result in severe health issues. It’s usually detected when the disease is in advanced stages, and the patient is clearly showing signs of heart or lung stress. However, in some cases, a person may not show symptoms, and the condition is discovered by chance. Doctors generally consider the possibility of RCM if a patient has typical heart function but exhibits signs of diastolic dysfunction, a condition where the heart can’t properly relax and fill with blood, suggested by specific patterns on an echocardiogram (a test that uses sound waves to create pictures of the heart).
When patients do have symptoms of RCM, these may vary considerably. Some might have severe heart failure symptoms such as bulging veins in the neck, fluid in the abdomen, swelling in the legs, or sometimes fluid in the lungs. Others might have lesser tolerance to exercise or be newly diagnosed with an irregular heartbeat condition called atrial fibrillation. Unfortunately, the first indication of RCM in some people could be a sudden cardiac arrest. Less frequent symptoms include chest pain (as with a heart attack), blood clots, or being mistakenly diagnosed with another heart issue, hypertrophic cardiomyopathy, which involves an obstruction to the flow of blood from the left ventricle of the heart.
If a patient is suspected to have RCM, during physical examination, doctors also look for symptoms outside the heart, which could hint at the underlying cause of RCM. For example, carpal tunnel syndrome might suggest a condition called amyloidosis, while certain patterns on chest imaging could indicate a condition called sarcoidosis. People with a condition called hemochromatosis might have a classic symptom of skin turning bronze in color, as well as signs of liver disease, joint pain, and hormonal disorders such as diabetes.
During a physical examination of a patient with RCM, the doctor may find that the heart is less displaced than in dilated cardiomyopathy (another type of heart muscle disease) and less forceful than in hypertrophic cardiomyopathy. A fourth heart sound is more commonly detected than a third heart sound when the heart is in a regular rhythm, but irregular heart rhythm (atrial fibrillation) is frequently seen. The doctor might observe specific patterns in neck vein pressures, which could increase upon breathing in, indicating a positive Kussmaul’s sign, another clue to the diagnosis of RCM.
Testing for Restrictive Cardiomyopathy
When your doctor suspects you may have a heart problem, one of the first tests they might use is an electrocardiogram (ECG). This is a tool that tracks your heart’s electrical activity. If the waves of electrical activity (called the QRS complex) are weak or normal, but your heart muscle is thick despite no problems with your heart valves or high blood pressure, it’s possible you might have a disease called amyloidosis. However, just because the electrical activity is normal doesn’t mean you can’t have this disease.
The main tool a doctor uses to diagnose diseases like restrictive cardiomyopathy (a condition where the heart muscles become rigid and less elastic) is a procedure called an echocardiogram. This procedure uses sound waves to create images of your heart and helps differentiate restrictive cardiomyopathy from similar conditions such as constrictive pericarditis. The echocardiogram can also help hint towards a specific diagnosis.
A cardiac MRI (magnetic resonance imaging) can also be helpful in determining the cause of your symptoms. In some cases, when other tests don’t provide a clear answer, your doctor may need to carry out a procedure called an endomyocardial biopsy, where a small piece of your heart tissue is taken for examination.
In addition to the above, a cardiac MRI can provide helpful supporting evidence for the diagnosis of restrictive cardiomyopathy, especially in the case of amyloidosis, where a specific pattern is seen when a contrast dye called gadolinium is used. There’s also a type of imaging called nuclear imaging, which is particularly useful for diagnosing these conditions as it also shows a liking for amyloid, the substance that builds up in the heart in amyloidosis.
Blood tests for substances called biomarkers, such as troponin T, B-type natriuretic peptide (BNP), and pro-BNP can also be useful in diagnosing and predicting the course of these heart conditions.
To confirm a diagnosis, a biopsy (where a small piece of tissue is taken for close examination) or an aspirate (where fluid is taken) is usually needed. An endomyocardial biopsy is considered the best method for diagnosing cardiac amyloidosis. After the biopsy, a technique called mass spectrometry is used to analyze the tissue and give more details about the disease. For certain diseases like hereditary hemochromatosis, a genetic test may be used, as it’s often linked with specific genetic changes, such as HFE C282Y and H63D.
Treatment Options for Restrictive Cardiomyopathy
Treatment for RCM, or Restrictive Cardiomyopathy, generally involves addressing the underlying cause and handling any heart failure symptoms that might occur due to the disease. At the moment, we don’t have a cure for RCM, but there are treatments that can help to manage and reduce the symptoms.
For symptoms similar to heart failure, diuretics, which are medicines that help eliminate salt and water from your body, are frequently used to help reduce any overload of fluid in the body. However, care must be taken since patients with RCM need high filling pressures to ensure their heart maintains normal function. Medicines like beta-blockers or calcium channel blockers could also potentially be used to increase the time the heart has to fill with blood. These medications might also help in treating dysrhythmias, which are abnormal heart rhythms that are common in people suffering from this condition. If the patient also develops systolic heart failure, which is a condition where the heart can’t pump blood properly, medication like angiotensin-receptor blockers may be introduced.
In case of sarcoidosis, which is an inflammation that usually affects the lungs, skin, or lymph nodes, antiarrhythmics are commonly used because of the frequent occurrence of conduction disease, a condition that disrupts the electrical system of the heart. Immunosuppressive agents like corticosteroids and other steroid-related agents are sometimes used to manage sarcoidosis. When it comes to hemochromatosis, a disease caused by too much iron in the body, the preferred treatment is therapeutic phlebotomy, a procedure of drawing blood out of the veins. In situations where the heart failure is advanced, more drastic measures such as a heart transplant or the insertion of a left ventricular assist device, which is a mechanical pump that helps a weakened heart pump blood, may be necessary for some patients. The choice of treatment in each case will depend on the specific condition of the patient, the risks involved, and how well the patient can tolerate the treatment.
What else can Restrictive Cardiomyopathy be?
When a doctor is considering a diagnosis of restrictive cardiomyopathy (RCM), they have to rule out similar conditions, which include:
- Constrictive pericarditis
- Acute or chronic heart failure
- Hypertensive heart disease
- Hypertrophic cardiomyopathy
- Acute or chronic pericarditis
Among these, constrictive pericarditis (CP) is the one most commonly confused for RCM. That’s why it’s crucial to investigate the similarities and differences between the two. Both conditions have almost the same signs and symptoms – things like distended neck veins, a certain sign when inspecting the neck veins (Kussmaul sign), and specific heart sounds.
However, there are few subtle differences. There’s a unique heart sound called S3 and increased levels of BNP (a heart molecule), which are more common in RCM. On the other hand, a particular heart sound referred to as a pericardial knock, visible changes on the heart x-ray image, thickening of the heart’s covering under imaging, and BNP levels under 100 are more likely to be associated with CP.
Another big difference is what’s known as ventricular interdependence – a situation where when one part of the heart fills up with blood, the other part fills up less. This only happens in CP, not RCM.
What to expect with Restrictive Cardiomyopathy
Restrictive cardiomyopathy (RCM), like other heart muscle diseases, has a very poor outlook. In fact, among all such conditions, it has the worst expected outcome. Statistics reveal that people diagnosed with this disease often only live for 2 to 5 more years.
Possible Complications When Diagnosed with Restrictive Cardiomyopathy
Complications from RCM, or Restrictive Cardiomyopathy, can include a variety of health issues:
- Thromboembolism: A condition where blood clots form in the blood vessels and could potentially block blood flow.
- Dysrhythmias: Irregular heartbeats that can be too fast, too slow, or erratic.
- Heart Failure: A condition where the heart isn’t pumping blood as effectively as it should.
- Cardiac Cirrhosis: A condition where the liver is damaged due to heart problems, leading to scarring and liver damage.
- Extra-Cardiac Manifestations Depending on Etiology: Other health issues linked to the underlying cause of the Restrictive Cardiomyopathy.
Preventing Restrictive Cardiomyopathy
If you are diagnosed with restrictive cardiomyopathy, it’s very important that you understand the condition thoroughly. Most types of this heart disease, unfortunately, are fatal and, at present, modern medicine doesn’t have a cure for it. You really need to be aware of this reality.
Early in the process of managing this disease, it’s crucial that you and your loved ones are educated about its progression and outcome. Following this, you usually will undergo an evaluation for a heart transplant. This evaluation is necessary as it determines if a heart transplant could be a treatment option for you.
Additionally, you’ll be referred to a heart failure specialist who can guide you with a specific treatment plan. Depending on your preferences, you might also discuss end-of-life care with a palliative care team, who are experts in making you comfortable during serious illnesses and a hospice care team, who provides support and care if the condition becomes very severe.
