Cardiac Amyloidosis - III

Atrial involvement in transthyretin amyloidosis.  Close up of a four chamber view of the atria in a case of transthyretin-type amyloidosis.  There is a fine granularity of the endocardium (resembling wet sandpaper) of the pectinate muscles, the crista terminalis of the right atrium as well as the endocardium of the tricuspid valve. On microscopic exam, these deposits are small and clearly involve the subendocardium and endocardium.  The left atrium shows also the fine granularity which has been described as “glassy” or “waxy”.  However, the more conspicuous lesions are the yellow-ochre plaques throughout the white atrial endocardium, which are also present on the posterior leaflet of the mitral valve. Examination of the semilunar and atrioventricular valves can also reveal amyloid deposits, both as granules and as plaques. In addition ventricular infiltration, while subtle can be grossly seen in the ventricular myocardium. (IVC) = Inferior vena cava. (CT) = Crista terminalis. (IAS) = interatrial septum. (RA) = right atrium. (LA) = Left atrium.