Restrictive Cardiomyopathy (Infiltrative Cardiomyopathy)

Restrictive (infiltrative) cardiomyopathy is a disorder of the heart muscle, in which the stiffened walls of the ventricles become resistant to adequate filling up with blood, when the heart relaxes (diastole) after every contraction, leading to heart failure.

  • Restrictive cardiomyopathy is the result of heart muscle being replaced by scar tissue, often due to the damage caused to it by the infiltration and accumulation of harmful substances.
  • A physical examination followed by echocardiography and cardiac catheterization help diagnose restrictive cardiomyopathy.
  • Treatment is focused mainly on treating the cause, as direct treatment of restrictive cardiomyopathy is not usually feasible.

Restrictive cardiomyopathy is the rarest form of cardiomyopathy and its cause is also rarely known. There are two types of restrictive cardiomyopathy.

In one type of restrictive cardiomyopathy, the heart muscle (myocardium) is gradually replaced by scar tissue possibly due to injury to the myocardium resulting from exposure to radiation during the treatment of cancer. But often, no such apparent cause can be attributed to this abnormal formation of scar tissue in the myocardium.

In the other type, certain substances infiltrate the heart muscle and accumulate there. When body has an excess of iron, as in the condition hemochromatosis, it may accumulate in the heart muscle too.

Amyloidosis, is a condition in which Amyloid protein accumulates in tissues, especially in older people. When amyloidiosis occur in the heart, restrictive cardiomyopathy may result.

Hypereosinophilic syndrome is a condition found in tropical countries, where a type of white blood cells called eosinophils , infiltrate the heart muscle.

Sarcoidosis is a disease where small granules of waste products are formed in various organs. This type of granuloma tissue can form in the heart muscle, causing restrictive cardiomyopathy.

Endocardial fibroelastosis, a congenital abnormality in which the left ventricle is lined by a thick layer of fibrous tissue, can usually be the cause of restrictive cardiomyopathy in children.

Symptoms

Restrictive cardiomyopathy exhibits the same symptoms of heart failure such as, shortness of breath and swelling due to fluid retention (edema). Chest pain may not be felt, but awareness of heartbeats (palpitations), due to abnormal heart rhythms are often felt on exertion. The heart can pump blood adequately during rest, because more than the pumping action, it is the heart’s capacity to fill up with blood, which is affected by the stiffening of the heart muscle. Hence, restrictive cardiomyopathy is usually asymptomatic at rest. However, symptoms appear during exercise, as the stiff heart is unable to pump efficiently to keep up with the body’s increased demand for blood and oxygen.

Diagnosis

Restrictive cardiomyopathy is diagnosed with the help of various tests.

Electrocardiography (ECG) may not help in proper diagnosis as it mainly shows the abnormalities in the electrical activity of the heart.

Echocardiography images of the structure and functioning of the heart can show whether the heart function is normal only during contraction (systole) and whether there is any enlargement of the atria.

Magnetic resonance imaging (MRI) is ideal as it can show changes in the texture of the heart muscle due to infiltration of substances such as iron and amyloid.

Cardiac catheterization helps remove a sample of the heart muscle for biopsy to detect the infiltrating substance.

Prognosis

Prognosis is bleak, as only 30 % people with restrictive cardiomyopathy survive beyond 5 years from the time symptoms appear.

The main reason for the poor prognosis is that many drugs used for treating heart failure are counteractive in the case of restrictive cardiomyopathy. Diuretics, which are the mainstay of the treatment of heart failure, help relieve leg swelling and reduce lung congestion. However, they worsen restrictive cardiomyopathy, since they decrease the volume of blood reaching the heart. Other main drugs used to treat heart failure such as angiotensin-converting enzyme (ACE) inhibitors, which help reduce the workload on the heart, also lowers blood pressure. It adversely affects those with restrictive cardiomyopathy, as it results in inadequate blood supply to the rest of the body. Often, Digoxin also doesn’t help.

Treatment

Treating the cause of the restrictive myopathy is the key to damage control. Even a partial reversal may be possible in certain cases.

  1. When infiltration of myocardium by iron is found to be the cause of restrictive cadiomyopathy, periodic blood-letting (phlebotomy) or removal of excess iron through chelation help reduce the amount of iron stored in the heart, thus reversing the condition.
  2. When sarcoidosis is the cause, corticosteroids may help clear up the granuloma tissue in the heart.

However, in many cases, the treatment of restrictive cadiomyopathy is difficult or even impossible, especially since the cause is often unknown.

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Yasser Elnahas

MD, PHD, Professor Of CardioVascular Surgery
Dr. Yasser Elnahas, Is an associate Professor of Cardiovascular Surgery. Dr. Elnahas was trained as a fellow At Texas Heart Institute And Mayo Clinic Foundation.Dr. Elnahas is dedicated to educating the general public about different disease conditions and simplifying the medical knowledge in an easy to understand terminology.

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