Histological Evidence of Amyloid Deposition in Old Thrombotic Lesions and in Longterm Bioprosthetic Cardiac Valve Implants in Man: Two Recently Observed and Possibly Related Forms of Localized Amyloidosis of the Cardiovascular System
In a series of old thrombotic lesions, amyloid deposition is shown in sclerotic heart valves, a thrombus of the left atrium, a post-infarction aneurysm of the left ventricle, two arterial aneurysms and an encapsulated scalp hematoma. The deposits are permanganate-resistant and contain tryptophan. Electron microscopy demonstrates typical fibrils in three cases. No patient showed evidence of systemic amyloidosis.
The natural history of sclerocalcific valvulopathies and present observations favor the following pathogenesis: ageing of the thrombus with degradation of a coagulation-related amyloid precursor protein and its transformation into amyloid fibrils; inclusion of amyloid in replacement sclerosis.
In a parallel study of bioprosthetic cardiac valve explants, amyloid microdeposits were demonstrated in a fascia lata valve and 23 porcine aortic valves (PAV) (47% of all longterm implants): Electron microscopy confirmed this finding in 3 PAV. All positive PAV had been implanted for at least 33 months and all except 5 presented dysfunction and/or severe cusp degradation. In most cases, amyloid was permanganate-resistant and tryptophan-positive.
The pathogenesis of this new form of amyloidosis might consist in penetration of human macrophages in deteriorated cusps and their interaction with blood-borne precursors. One of these may be identical to the precursor involved in thrombus-related amyloidosis.
KeywordsFormalin Citrate Paraffin Tryptophan Fibril
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