What Is Restrictive Cardiomyopathy?

Restrictive cardiomyopathy (RCM) is a heart condition in which the walls of the heart become rigid and cannot expand normally to fill with blood. Although it rarely produces noticeable symptoms, RCM can cause heart failure and must be monitored closely once it's diagnosed. Restrictive cardiomyopathy is the rarest form of cardiomyopathy (an umbrella term for any disease of the heart muscle), comprising fewer than 5% of all cardiomyopathies and affecting mostly older people. Treatment for restrictive cardiomyopathy can range from taking medication to receiving a heart transplant.

Types of Restrictive Cardiomyopathy

Restrictive cardiomyopathy occurs when scar or other abnormal tissue replaces healthy tissue, causing the ventricles of the heart to become stiff and unyielding to blood flow.

There are two classifications of restrictive cardiomyopathy: primary and secondary. Primary RCM refers to conditions in which the disease develops independently of underlying factors. Examples of restrictive cardiomyopathy in this category include:

• Endomyocardial fibrosis
• Löffler's endocarditis
• Idiopathic restrictive cardiomyopathy

Secondary RCM occurs as a result of another disease that interferes with the normal function of the heart muscle, reducing its elasticity and restricting the ability of the ventricles to fill with blood. There are two categories of such diseases:

• Infiltrative diseases, meaning inflammatory diseases that spread to organs such as amyloidosis, sarcoidosis, and radiation carditis
• Storage diseases, such as hemochromatosis, glycogen storage disorders, and Fabry's disease.

Symptoms

Restrictive cardiomyopathy causes relatively few symptoms, if any. Those that do occur resemble classic symptoms of heart failure: 

• Dyspnea (shortness of breath)
• Edema (swelling of the legs and feet)
• Weakness
• Fatigue
• Inability to exercise
• Heart palpitations
• Weight gain and bloating
• Nausea
• Poor appetite

Less common symptoms of restrictive cardiomyopathy include:

• Fainting, often caused by irregular heart rhythms or abnormal blood vessel performance during physical exertion
• Chest pain or pressure, which mainly occurs with activity, but can also happen at rest or after eating

Causes

Restrictive cardiomyopathy occurs when the heart muscle becomes stiff, preventing it from fully relaxing during the diastolic phase of the cardiac cycle—the period between heartbeats when the heart must expand to fill with blood. This makes it difficult for the ventricles of the heart to fill adequately. This causes the heart's atria to enlarge because they must work harder than normal. The size and systolic function of the ventricles usually remain normal or near-normal until later stages of the disease.

What causes the heart muscle to become stiff is not fully understood. The condition is not related to coronary artery disease (CAD), but a number of conditions are associated with RCM.

• Sarcoidosis, a rare condition in which groups of immune cells form lumps, called granulomas, in organs in the body. It most often affects the lungs and lymph nodes in the chest, but can directly impact the heart.
• Hemochromatosis, a disease characterized by the accumulation of excess iron in the body. Unneeded iron is toxic and can cause organ damage.
• Amyloidosis, in which abnormal proteins build up in the body's organs, including the heart.
• Connective tissue disorders, such as scleroderma
• Certain cancer treatments, including radiation and chemotherapy
• Storage diseases, such as Gaucher disease

Diagnosis

Your doctor can detect restrictive cardiomyopathy with a physical exam, medical history, and diagnostic tests. Echocardiogram, is the standard test used to confirm RCM. It shows diastolic abnormalities and evidence of blood not filling the ventricles properly. Your doctor may also order other tests to make a diagnosis such as:

• Electrocardiogram
• Chest X-ray
• Exercise stress test
• Cardiac catheterization
• CT scan
• MRI
• Nuclear heart scan, such as a multiple gated acquisition scan (MUGA) scan. Doctors use this noninvasive test to evaluate heart function.
• Blood tests to help determine which type of RCM you have.

In rare cases, your doctor will order a heart muscle biopsy, which can help make the diagnosis when an infiltrative disease (such as sarcoidosis) or storage disease is present.

Treatment

Treatment for restrictive cardiomyopathy involves heart failure management and addressing underlying causes. Unfortunately, there is no specific treatment that directly reverses the RCM itself.

There are, however, an array of treatment options that can help.

Lifestyle Changes

Your doctor will likely recommend diet and exercise as a part of your treatment plan. Exercise can help you lose weight and strengthen your heart. Adopting a low-sodium diet and losing weight help lower blood pressure, which eases the strain on your heart.

Diuretics

Diuretics, such as Lasix (furosemide), offer the most benefit in treating people with restrictive cardiomyopathy. These drugs reduce edema (swelling). However, it is possible to make people with this condition “too dry” with diuretics, further reducing the ventricles' filling of blood during diastole. Close monitoring of your condition is necessary when taking diuretics. This means measuring weight at least daily and periodically checking blood tests to look for signs of chronic dehydration. The optimal dose of diuretics may change over time, so vigilance is essential.

Calcium Channel Blockers

The use of calcium channel blockers can help RCM by directly improving the heart’s diastolic function and slowing the heart rate to allow more time to fill the ventricles between heartbeats. For similar reasons, beta-blockers can also be helpful. If atrial fibrillation is present, it is critical to control the heart rate to allow adequate time to fill the ventricles. The use of calcium channel blockers and beta-blockers can usually accomplish this goal.

Ace Inhibitors

There is some evidence that ACE inhibitors may benefit at least some people with restrictive cardiomyopathy, possibly by reducing heart muscle stiffness.

Heart Transplant

Your doctor may recommend a heart transplant as a surgical option if other treatments fail to control restrictive cardiomyopathy symptoms.

A Word From Verywell

Restrictive cardiomyopathy is rare, and you likely won't have symptoms and can live a normal life. One study showed that one-, five-, and 10-year survival for RCM patients overall is at 88%, 66%, and 45%, respectively.

The treatment outlook of restrictive cardiomyopathy is worse in men, people older than age 70, and people whose cardiomyopathy is caused by a condition with a poor prognosis, such as amyloidosis.

While this is the rarest type of cardiomyopathy there are numerous treatment options available. You can contact your doctor to determine what is the best path to getting diagnosed and treated.