Extracellular deposition in cardiac tissue of a proteinaceous material that, when stained with Congo red, demonstrates apple-green birefringence under polarized light and that has a distinct color when stained with sulfated Alcian blue. Viewed with electron microscopy, the amyloid deposits are seen to be composed of a beta-sheet fibrillar material. These nonbranching fibrils have a diameter of 7.5 to 10 nm and are the result of protein misfolding. [https://orcid.org/0000-0002-0736-9199, PMID:16186440]
