What Is Restrictive Cardiomyopathy?

Restrictive cardiomyopathy (RCM) is a rare type of heart disease that affects the heart's ability to fill with blood effectively. The heart's ventricles (lower chambers) become stiff due to abnormal tissue that replaces the normal heart muscle. There are three main types of cardiomyopathy restrictive, hypertrophic, and dilated; restrictive is the least common of the three.

Restrictive cardiomyopathy can lead to a range of symptoms, like swelling of the limbs and abdomen, fatigue, and shortness of breath. It is important to receive appropriate medical treatment to prevent restrictive cardiomyopathy from worsening over time.

There are several types of RCMs, and they all vary in their clinical presentation and treatment. Further complications can also arise from RCMs, such as arrhythmias (irregular heartbeat) and heart failure (when the heart is unable to pump enough blood around the body properly).

Overview

The heart’s ventricular chamber sizes and systolic function (i.e., its ability to pump out blood) are typically normal until the later stages of disease progression. RCM can affect either one or both ventricles and may cause symptoms of left or right heart failure.

Causes of restrictive cardiomyopathy

There are numerous causes of restrictive cardiomyopathy; it can be the product of inherited or acquired predispositions and disease, or even a mixture of both. This can also be categorised as storage disease, infiltrative, non-infiltrative, and endomyocardial.

The most common identifiable causes of RCM are:

• Loeffler endocarditis – is an uncommon RCM characterised by the impaired function of the heart's relaxation pattern (diastolic dysfunction). It is also linked to eosinophilia (an increased level of eosinophils - a white blood cell). This condition is usually an indication of a parasitic infection or allergic reaction. Other associations are with endomyocardial fibrosis, which causes diastolic restrictions primarily to the right ventricle¹
• Cardiac amyloidosis – is a systemic disease in which a group of proteins form an extracellular deposition (a malfunction in protein assembly caused by mutation or environmental changes) in different body tissues, including the heart, and ultimately result in organ failure and death if not treated effectively. Cardiac amyloidosis typically presents with fast-progressing diastolic dysfunction in a non-dilated ventricle (when the chamber of the heart that pumps blood does not develop properly)²
• Cardiac sarcoidosis – is a granulomatous disease (an inherited immunodeficiency disease which increases inflammation affecting the organs, usually the lungs), resulting in infections caused by bacteria and fungi. Cardiac sarcoidosis is a rare form of sarcoidosis (<10% of patients); this abnormal immune response can cause small lumps of cells to form in organs such as the heart, resulting in infiltrative cardiomyopathy.³ Although rare, a study found that cardiac sarcoidosis was more common in those assigned female at birth, with the highest incidence worldwide in Japan⁴
• Cardiac hemochromatosis – is a hereditary or acquired disease characterised by high iron buildup in the body. The additional iron causes organ toxicity and dysfunction, damaging organs, including the heart. Cardiac hemochromatosis is a potentially preventable cause of heart failure, affecting both sexes equally⁵

There are several other rare causes of RCM, such as radiation and chemotherapy for cancer treatment, and medications; each cause varies in terms of mutation, sex variance, and occurrence.

Signs and symptoms of restrictive cardiomyopathy

Symptomatic presentation of RCM include:

• Chest pain
• Shortness of breath at rest
• Poor exercise tolerance
• Heart palpitations
• Dizziness
• Newly diagnosed arrhythmia (irregular heartbeat)
• Fainting
• Swelling of limbs, abdomen, and neck veins
• Heart murmur 

More serious cases of RCM may experience:

• Sudden cardiac death - (when the heart stops beating or is not beating adequately enough to sustain life)
• Ischemia (restricted blood flow/oxygen to a certain part of the body)
• Blood clots

Management and treatment for restrictive cardiomyopathy

There is currently no cure for RCM. However, primary prevention (preventing disease from occurring) under the guidance of a healthcare professional may include lifestyle changes such as:

• Smoking cessation 
• Avoiding drugs and alcohol
• Weight loss
• A healthy diet and physical exercise
• Treatment of underlying health conditions

Pharmacological treatments are available to alleviate symptoms and are aimed at targeting the underlying causes and symptoms of heart failure that may be experienced secondary to the disease.

• Diuretics (water pills) increase the body's urine production helping to get rid of salt and water from the body, thus reducing swelling and blood pressure
• Beta-blockers and calcium channel blockers help to control the heart rate and rhythm, an important part of treating an arrhythmia such as atrial fibrillation
• Treatment choice for hemochromatosis is therapeutic phlebotomy (drawing blood as part of  medical treatment)
• Anticoagulants (blood thinners) will assist in preventing blood clots from forming
• Corticosteroid medication is used to reduce inflammation 

Advanced treatments include; cardiac transplant or device implantation(e.g. pacemaker).

Diagnosis of restrictive cardiomyopathy

Diagnosing RCMs can be challenging due to the diverse nature in which it manifests itself. The first line of diagnosis may be through a physical examination by a healthcare professional. Physical signs can include swelling of the extremities. Using  a stethoscope, they may listen for sounds in the heart and lungs that indicate  cardiomyopathy. For further confirmation, the healthcare professional may order one or more of the cardiac diagnostic tests below:

Non-invasive tests

• Electrocardiogram (ECG/ EKG) - Gold standard test when a cardiac diagnosis is suspected. It records the heart's electrical activity and displays the heart rate and rhythm
• Echocardiogram - an ultrasound of the heart that utilises sound waves to create moving pictures of the heart's structures
• Cardiac magnetic resonance imaging (CMR) – creates magnetic and radio waves that produce detailed images of the inside of the heart
• Holter monitor - a portable device monitoring the heart's electrical activity during regular daily activities

Invasive tests

• Cardiac catheterisation - allows for the analysis of blood flow and pressure in your heart’s chambers. The procedure is carried out using a catheter (a long, thin, flexible tube) that is passed through a blood vessel to the heart
• Endomyocardial biopsy - a procedure involving a small piece of heart muscle being removed; this can be done during a cardiac catheterisation procedure. The muscle is studied to check for any cellular changes indicative of RCM

Risk factors

Certain conditions and factors can increase the risk of RCM; these include:

• Family history of sudden cardiac death or heart failure
• Diabetes
• Alcoholism
• Chronic high blood pressure
• Hemochromatosis
• Sarcoidosis
• Amyloidosis

Complications

RCM can cause several complications:

• Heart failure
• Abnormal heart rhythm
• Cardiac arrest
• Stroke

FAQs

How can I prevent restrictive cardiomyopathy

• Inherited RCM cannot be prevented; however, when an underlying condition precipitates RCM, treatment of this condition can help to prevent later complications.

How common is restrictive cardiomyopathy

• Around 5% of cardiomyopathies are RCMs, the least common type of cardiomyopathy. 

When should I see a doctor

If experiencing any of the below symptoms, medical advice from a healthcare professional must be sought out:

• Chest pain
• Shortness of breath 
• Poor exercise tolerance
• Palpitations
• Dizziness
• Fainting
• Swelling of limbs, abdomen and neck veins

Summary

Restrictive cardiomyopathy (RCM) is a rare form of heart disease affecting the heart's ability to fill with blood effectively. It can lead to a range of symptoms, including shortness of breath and swelling in the legs and feet. It is important to receive appropriate medical treatment to prevent RCM from worsening over time, as it can lead to complications such as stroke or cardiac arrest.