Common Causes of Restrictive Cardiomyopathy
Identifying the cause of restrictive cardiomyopathy is critical, as treatment is most effective when directed at the underlying condition.
Common causes and risk factors of RCM include:
- Cardiac amyloidosis: The most common cause of RCM, in which deposits of a protein called amyloid build up in the heart muscle, causing it to stiffen
- Cardiac sarcoidosis: A condition in which granulomas (small areas of inflammation) form in your heart
- Hemochromatosis: A condition caused by excessive iron buildup in the heart tissue
- Wilson disease: A rare condition caused by excessive copper accumulation
- Idiopathic restrictive cardiomyopathy (genetic RCM): In some cases, no external cause is found, and the condition is caused by an inherited gene mutation
- Radiation or chemotherapy-related damage: Prior cancer treatments can sometimes cause the heart muscle to stiffen over time
Types of Restrictive Cardiomyopathy
RCM can be categorized based on its underlying cause:
Infiltrative Restrictive Cardiomyopathy
Infiltrative cardiomyopathy is the most common form and occurs when abnormal substances, most often amyloid proteins, accumulate in the heart muscle, reducing its flexibility. Cardiac amyloidosis is the leading example of this type.
Non-Infiltrative Restrictive Cardiomyopathy (Idiopathic or Genetic)
In non-infiltrative RCM, no abnormal deposits are present, but the heart muscle stiffens due to genetic mutations or unknown causes. This form tends to be rarer and can affect multiple family members.
Storage Disease-Related Restrictive Cardiomyopathy
Certain metabolic storage disorders, such as hemochromatosis (iron overload) or Wilson's disease (copper accumulation), can cause RCM by depositing excessive minerals in the heart muscle.
Signs & Symptoms of Restrictive Cardiomyopathy
Many people with RCM experience symptoms gradually, and the condition is sometimes mistaken for other forms of heart disease or heart failure. Because the heart cannot fill properly, symptoms are often related to fluid backup and reduced cardiac output. When symptoms do appear, they should prompt immediate evaluation by a specialist. Symptoms often develop gradually, but in some cases the onset may be sudden or acute.
Symptoms may include any of the following:
Shortness of Breath
Shortness of breath is one of the most common symptoms of RCM, occurring during exercise or while sleeping. As the heart loses its ability to fill normally, fluid can back up into the lungs, making breathing increasingly difficult.
Fatigue
Fatigue or lack of energy is frequently reported by RCM patients, as the heart's impaired filling reduces the amount of blood pumped to the rest of the body with each beat, leaving tissues and muscles undersupplied.
Swelling (Edema)
Fluid retention can cause lower extremity swelling (feet, ankles or calves) and abdominal swelling**, particularly as the condition progresses. Swelling in these areas is a sign that the heart is struggling to manage normal fluid circulation.**
Heart Arrhythmia (Palpitations)
Palpitations and uneven rhythms of the heart are common in RCM. Because the condition is frequently associated with ventricular tachycardia (a dangerous, fast heart rhythm), arrhythmia symptoms should be evaluated promptly.
Chest Pain
Chest pain can occur in RCM patients as the stiffened heart muscle demands more from the coronary circulation, leading to discomfort or pressure, particularly during exertion.
Loss of Appetite and Decreased Urine Output
In more advanced cases of RCM, loss of appetite and decreased urine output can develop as reduced blood flow affects the digestive system and kidneys, signaling that the condition has progressed to a more serious stage.
How Restrictive Cardiomyopathy Is Diagnosed
Restrictive cardiomyopathy is distinguished from other causes of heart failure by a variety of tests and physical screenings. Identifying the specific cause early on is important for preventing further damage to your heart. The diagnosis of RCM at Houston Methodist requires our specialists to conduct a comprehensive evaluation that may include any of the following:
- Physical exam: A physical exam that includes assessing for signs of fluid retention such as swelling in the legs or ankles, listening for abnormal heart sounds, checking for elevated neck veins and evaluating other indicators of impaired cardiac filling.
- Family medical history review: Because RCM can be genetic in some cases, your doctor will ask whether anyone in your family has been diagnosed with cardiomyopathy or heart failure and whether anyone has experienced unexplained early cardiac events or cardiovascular health problems that led to death.
- Echocardiogram: An echo using echocardiography is the primary imaging tool for RCM, used to assess how well the ventricles fill and contract and to detect signs of stiffening or abnormal tissue.
- Cardiac MRI: A cardiac MRI provides detailed imaging of heart muscle structure and can help identify specific causes of RCM, such as amyloid deposits or inflammation.
- Cardiac catheterization: A cardiac catheterization measures the filling pressures within the heart and can help distinguish restrictive cardiomyopathy from constrictive pericarditis, a condition with similar symptoms that requires a different course of treatment.
- Fluorodeoxyglucose (FDG) cardiac PET scan: An FDG cardiac PET scan is used to proactively look for rare causes of restrictive cardiomyopathy, such as cardiac sarcoidosis, using innovative imaging techniques.
- Electrocardiogram (ECG/EKG): An EKG detects electrical abnormalities and arrhythmias commonly associated with RCM, including ventricular tachycardias.
- Electrical mapping and image-guided heart biopsy: Because RCM is often associated with ventricular tachycardias, our experts collaborate closely with electrophysiology specialists to offer these advanced techniques, which increase the chances of the most accurate diagnosis.
- Genetic testing and counseling: Genetic testing can confirm an inherited cause of RCM and help identify at-risk family members who should be screened.
- Holter monitoring: This wearable device records heart rhythm continuously over 24 hours to 30 days to detect arrhythmias, including the ventricular tachycardias commonly associated with RCM.
- Lab work and specialized testing: Lab work and specialized testing includes bloodwork to assess organ function, as well as tests to evaluate for systemic conditions such as hemochromatosis, Wilson's disease or amyloidosis.
Treatment Options for Restrictive Cardiomyopathy
The primary goal while caring for someone with restrictive cardiomyopathy is to identify and treat the underlying cause of the condition. RCM treatment is tailored to the specific cause and severity of the disease. When an underlying condition is identified, targeted treatment of that condition is the most effective approach.
Non-Surgical Treatment
For many patients, RCM can be effectively managed without surgery. Non-surgical treatment options include:
- Targeted therapies for cardiac amyloidosis: Including newer agents that stabilize or reduce amyloid protein production
- Immunosuppressive therapy for cardiac sarcoidosis: Used to reduce inflammation in the heart
- Phlebotomy or chelation therapy for hemochromatosis and Wilson disease: Used to reduce excess mineral buildup in the heart
- Diuretics: Help reduce fluid buildup and relieve symptoms of congestion
- Anticoagulants (blood thinners): Help reduce the risk of blood clots and stroke, particularly in patients with arrhythmias
- Antiarrhythmic medications: Help manage dangerous heart rhythm abnormalities
Surgical Treatment
When medications and other non-surgical approaches are not enough, our advanced heart failure specialists can help you explore all available options, which may include:
- Left ventricular assist device (LVAD): In select cases, an LVAD or other mechanical heart support may be considered as a bridge to transplant or as long-term therapy for patients whose symptoms cannot be controlled with medication alone.
- Heart transplant: Reserved for end-stage RCM when other treatments have been exhausted and heart function is critically impaired.