Cardiac Amyloidosis

Cardiac amyloidosis is a rare condition that affects a small number of people. Amyloidosis refers to a group of diseases caused by deposits of abnormal proteins, known as amyloid, in one or more organs of the body. Our bodies normally contain soluble proteins in our blood. For a variety of reasons, the proteins become insoluble and deposit in the tissues and organs, such as the kidneys, ligaments, gastrointestinal tract, heart, and nervous system.

What is cardiac amyloidosis?

Cardiac amyloidosis is a rare condition in which an abnormal protein, amyloid, is deposited in the heart. When this occurs, the heart becomes stiff and the walls of the lower heart chambers become much thicker than normal. As a result, the heart does not fill up properly and there is not enough blood to send around the body. Cardiac amyloidosis can result in congestive heart failure. Pressure builds in your heart and can cause fluid build-up in the lungs that leads to breathlessness and fluid build-up in soft tissues, which, in turn, leads to leg and abdominal swelling.

Causes 

There are two types of amyloidosis that can affect your heart. It is important to identify the type.

  1. Amyloid light chain (AL): In this form of amyloidosis, the bone marrow makes too much of a light chain immunoglobin, which is then deposited in the body’s tissues, such as the heart, gastrointestinal tract, and kidney. The light chain immunoglobin is normally used in fighting infections but, in this condition, the bone marrow makes too much. It is not known why the bone marrow makes too much AL.
  2. Transthyretin (TTR): The TTR protein is normally involved with transporting thyroid hormone and retinol (Vitamin A) in our bodies. There are two forms of TTR amyloidosis:
    1. Hereditary: A person with hereditary TTR has a mutation that makes the TTR protein abnormal, which results in fibril deposits in the body. This usually affects the nerves and the heart.
    2. Wild type (age related or previously called senile): For unknown reasons, the TTR protein forms an amyloid substance that deposits in the heart or carpel tunnel. Most commonly, this form of amyloidosis is seen in men over the age of 60.
Diagnosis 

Cardiac amyloidosis can be difficult to diagnose. The following are tests that may be used to diagnose cardiac amyloidosis.

  • Echocardiogram: This test looks for abnormalities in the heart muscle and heart wall thickness in addition to how stiff the heart is (its diastolic function). 
  • Cardiac magnetic resonance imaging (MRI): This test looks for abnormalities in the heart.
  • Blood tests:
    • BNP or NT-proBNP: BNP is released when your heart is stressed. This is measured over time.
    • Troponin.
  • Tissue biopsy: This test looks for the presence of amyloid protein. This is done by taking a small tissue sample. 
  • Strain imaging.
  • Electrocardiogram: This test identifies problems with heart rhythm.
  • Holter monitorThis test continuously monitors the heartbeat over one or two days to look for rhythm disturbances.
  • Nuclear imaging: Positron emission tomography (PET) tests measure inflammation and activity in different areas of the heart, using tiny amounts of radioactive compounds.
Treatment 

Treatment for cardiac amyloidosis is based upon the specific type of the condition present. Treatment for cardiac amyloidosis may include diuretics (to relieve pressure inside the heart) as well as specific therapies to slow or reverse the progression of the disease. 

An implantable cardioverter defibrillator (ICD) is like a pacemaker but can deliver an electrical shock when needed to restore normal heart rhythms. An ICD may be necessary for patients with more dangerous arrhythmias that can stop the heartbeat, such as ventricular fibrillation.

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