Cardiac Amyloidosis

Adopted from UKY website

Cardiac amyloidosis occurs when an abnormal protein — called amyloid — builds up in the heart tissue. This buildup makes it difficult for your heart to relax completely in between heart beats, making the heart stiff. This stops blood from getting into the heart. There is a “traffic-jam” of blood waiting to enter the heart all across the body, causing congestion. The congestion causes “leakage of fluid” from the blood into the tissues- manifesting as fluid in lungs, legs, various internal organs and elsewhere. The common symptoms are shortness of breath, swelling in legs, lethargy and loss of appetite. This is a progressive disease and an increasingly recognized cause of heart failure.

Figure 1: Normal heart chamber squeezing and relaxing

Read further to understand this in detail.

Normal heart:

Heart is supposed to relax completely in-between heart beats. This allows the blood to enter the heart chambers, like a balloon blowing up with air (figure 1).

The relaxation of the heart is an equally important requirement to keep the blood moving forward in the continuous circuit around the body.

The circuit around the heart:

This has been explained in details elsewhere

In brief, the blood goes around the body as shown in figure 2. Here, the left and right chambers are the chambers of the heart.

Figure 2: The journey of blood around the body

The issue with cardiac amyloidosis:

The essential problem is deposition of abnormal and sticky proteins (amyloid) in various organs which interfere with the function of that organ. When the deposition occurs in the heart, this is called cardiac amyloidosis.

Two main types of cardiac amyloidosis:

There are two main types of cardiac amyloidosis:

* Transthyretin amyloidosis (ATTR amyloidosis): This type results from mutated deposits of transthyretin, a protein made by the liver. The two subtypes of ATTR are:* Wild-type amyloidosis: Usually affects people in their 60s or older* Hereditary amyloidosis: Runs in families and typically affects people in their 40s or older

* Light chain amyloidosis (AL amyloidosis): This type of amyloidosis is associated with blood cancers like multiple myeloma. It is not a type of cancer, but it is treated with chemotherapy.

The type of amyloid protein deposited in the above two types of cardiac amyloidosis is completely different and formed by different mechanisms, however the essential problem is the same- abnormal protein deposition.

AL amyloidosis

In AL amyloidosis, excessive abnormal antibodies are being formed by abnormal antibody-forming cells. The antibody forming factory has malfunctioned and starts manufacturing multiple batches of unusable antibodies. These antibodies belong to the same mould and are being manufactured in large quantities (figure 3).

Figure 3: Excessive antibodies formed from the same mould in AL amyloidosis

Antibodies are made of heavy chains and light chains (figure 4)

Figure 4: Antibody