Cardiac Path Online
Pathology of Cardiac Amyloidosis
Amyloid deposits can be found commonly in hearts during autopsy examination.
The incidence increases with advanced age (mostly in patients over 60 years of age).
Myeloma - associated (primary) amyloidosis : Cardiac involvement occurs in approximately 90% of cases of myeloma-associated (primary) amyloidosis.
This form of amyloidosis occurs in association with multiple myeloma but may also occur in the absence associated disease.
Amyloid deposits are most likely to involve the spleen, kidneys, liver, and adrenal glands.
Secondary amyloidosis : Cardiac involvement also occurs in about 55% patients with amyloidosis associated with chronic illness (secondary amyloidosis) such as rheumatoid arthritis, tuberculosis, osteomyelitis, bronchiectasis, or lymphoma.
In this type of amyloidosis the major deposits occur in the tongue, gastrointestinal tract, lungs, skeletal muscles, skin and other mesodermal tissues and organs in addition to the heart.
Amyloidosis restricted to the heart: A distinctive type of amyloidosis has been described in which amyloid is restricted largely to the heart.
Deposits either do not appear in other organs or are present in insignificant amounts.
This is in contrast to the systemic forms of amyloidosis in which involvement of other organs is extensive.
It is of considerable interest that the average age of persons with amyloid deposits confined to the heart is higher than that of those with primary systemic amyloidosis or amyloid disease complicating multiple myeloma.
Senile cardiac amyloidosis: The disease affects elderly persons, usually in the seventh to ninth decades, and thus seems to be a manifestation of senescence.
It is sometimes referred to as senile cardiac amyloidosis.
Hereditary types: In addition to the foregoing forms of amyloidosis, certain hereditary types have been reported in which heart may become involved, and in one type it is the organ predominantly affected.
Although cardiac deposits of amyloid can be found, commonly in most instances the deposits are relatively slight and produce no gross morphologic change and are clinically insignificant.
Less commonly, cardiac amyloidosis may be sufficiently severe to cause cardiac symptoms, and in only rare instances can death from congestive cardiac failure be attributed to cardiac amyloidosis.
When the heart is severely involved, amyloid deposits may occur throughout the interstitium of ventricular and atrial myocardium.
Subendocardial deposits are especially common in the atria. The wall of the coronary arteries and arterioles and conduction pathways also may be involved.
These deposits may be readily detectable macroscopically, the ventricles may be enlarged, firm and rubbery in consistency, and tan in colour.
Discrete nodular deposits of amylod may be evident on cross sections of the ventricles or under the atrial endocardium.
There are multiple subendocardial deposits of glistening, partially translucent amyloid deposits in the atrium.
Similar nodules may occur on the epicardial surface or the parietal pericardium.
Involvement of the valvular endocardium also may occur.
Microscopically, amyloid occurs in extracellular, eosinophilic, amorphous hyaline deposits.
These deposits may form rings completely surrounding and compressing individual myocytes.
In severe cases atrophy vacuolization, or even complete loss of muscle fibers may occur.
Deposits may occur in the wall of small and medium-sized arteries and veins and in the interstitium of the endocardium or epicardium.
Amyloid may be suspected from evaluation of hematoxylin and eosin-stained microscopic sections because of the ring-like encircling of myofibers and the lack of the wavy fibrillar character of collagen.
However, amyloid can be more easily distinguished from collagen by staining with Congo Red or crystal violet.
With the Congo Red stain, amyloid is red orange, the protein is birefringent so that when Congo Red- stained tissue is viewed under polarized light it transmits an apple-green color.
With the crystal violet stain, amyloid has a metachromatic reddish-purple cast.
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