Histotopographic evidence that amyloid deposits in sclerocalcific heart valves and other chronic lesions of the cardiovascular system are related to old thrombotic material

Abstract

Deposition of amyloid in human sclero-calcific heart valves has been reported recently as a localized age-independent and dystrophic form of amyloidosis. Histochemical studies have shown that the deposits are permanganate resistant, contain tryptophan and P component and are immunologically unrelated to any known type of amyloid fibril protein. In this study histological observations from a series of four selected sclerotic heart valves show amyloid deposition in old thrombotic material covering fusing commissures or appositional collagen on the body of the leaflets. Similar cases from extravalvular sites have been added to the series: a partly hyalinized thrombus of the left atrium, a thrombotic aneurysm of the left ventricle, 2 thrombotic atherosclerotic aneurysms of the aorta and popliteal artery respectively, and an encapsulated haematoma of the scalp. The deposits are Congo red positive with typical green dichroism in polarized light, permanganate resistant and contain tryptophan. Electron microscopy of 3 cases displays small fibrils which are typical of amyloid. No patient showed evidence of systemic amyloidosis. The natural history of sclero-calcific valvulopathies and present observations favour the following pathogenesis: first, recurrent thrombotic deposition on thickened and fibrotic endocardium; second, degradation of a coagulation-related protein with beta potential during the aging of the clot with transformation into amyloid fibrils; finally, inclusion of the amyloid in sclerotic replacement tissue.