Restrictive Cardiomyopathy - Amyloidosis

Amyloidosis is a generic name given to an ifiltratitive process which is secondary to deposition of proteins(in a ß-pleated sheet conformation) in the interstitial space of the cardiac muscle, the endocardium, the valves or in the wall of small arteries. There are many proteins that can become organized in ß-pleated sheets and become deposited as amyloid. In the heart the more common ones are Transthyretin, Kappa and Lambda immunoglobulin chanisn, Amyloid A, Atrial Natriuretic Peptide and less commonly immunoglobulin heavy chains. There are many other proteins that caus amyloidosis, but these are far less common to involve the heart before they produce symptoms in other systems.

Amyloid panel
Left upper image,  the interstitium is expanded by an amorphous extracellular material (amyloid) which surrounds individual myocytes.  The  myocytes exhibit hypertrophy and degenerative changes. H&E. The right upper panel is a Toluidine blue  stained plastic section showing in greater detail the homogeneous nature of the amyloid deposits.  Left lower panel is a Thioflavin-S fluorescent stain,  when viewed under ultraviolet light amyloid deposits fluoresce in discrete intense light blue hue.  Right lower image shows that immunohistochemical determination of the source of amyloid deposits can be done with a number of commercially available antibodies. This section stained positively with immunoglobulin lambda light chains detected under fluorescence microscopy.  Note the green fluorescence of the amyloid deposits around the myocytes (black spaces). A complete set of examples of cardiac amyloidosis is shown here.
(Rahman JE, Helou EF, Gelzer-Bell R, Thompson RE, Kuo C, Rodriguez ER, Hare JM, Baughman KL, Kasper EK: Noninvasive diagnosis of biopsy-proven cardiac amyloidosis. J Am Coll Cardiol. 2004: 43; 410-415)