Ultrastructural alterations in acquired aortic and mitral valve disease as revealed by scanning and transmission electron microscopical investigations.

Scanning and transmission electron microscopical investigations were carried out on explanted human aortic and mitral valves to study the prevalence of hyperplastic and degenerative lesions in acquired valvular dysfunction. Biopsies were taken from 67 aortic and 23 mitral valves. All of the valves examined showed degenerative lesions including a loose binding of the endothelial cells, a partial denudation of the endothelial cover and areas of fibrous hyperplasia surrounded by calcium deposits. Additionally, the formation of various excrescences was detected by means of scanning electron microscopy. Of all excrescences identified, 90% were localized at the free margin of the leaflet, 3% in the subnodular region and 7% in the nodule of Arantius. The ratio of filiform to lamellar forms of hyperplastic lesions was approximately 80% in most of the samples examined. The results presented demonstrate the complex ultrastructural features of surgically explanted human valves showing both degenerative and hyperplastic lesions in the same valve.