Amyloidosis refers to buildup of a fibril called amyloid in tissues anywhere in the body. Fibrils are proteins produced in excess that are deposited in different organs and slowly replace normal tissue.

Different types of amyloidosis are caused by different types of proteins, such as "AL" and "AA." In cardiac amyloidosis there may be associated conduction disturbances (changes in the way the cardiac electrical impulse is transmitted through the heart).

Cardiac amyloidosis usually occurs during primary amyloidosis (called AL type amyloidosis). Primary amyloidosis usually accompanies multiple myeloma, a blood disorder in which too much of a certain type of protein is produced. This excess protein is deposited in the heart and in other organs such as the kidney. Deteriorating kidney function also occurs.

The heart is less frequently compromised by secondary amyloidosis (called AA type amyloidosis). Senile amyloidosis, however, is a type of secondary amyloidosis which does involve the heart. It is caused by overproduction of a protein different from both the AA and AL types. This particular protein is deposited mainly in the heart, but it can also infiltrate blood vessels. Senile cardiac amyloidosis is becoming more common as the average age of the population increases.

Cardiac amyloidosis is the most typical restrictive cardiomyopathy, and it is also known as “stiff heart syndrome.” Much less frequently, cardiac amyloidosis leads to dilated cardiomyopathy.

Cardiac amyloidosis found more commonly in men than in women.