Electron Microscopic Appearances of Rheumatic Lesions in the Left Auricular Appendage in Mitral Stenosis

Abstract

CELLULAR rheumatic lesions corresponding in structure to Aschoff nodules are found in the left auricular appendage in approximately 60 per cent of patients undergoing mitral valvotomy. The exact nature and structure of these lesions have not been elucidated. By light microscopy Aschoff cells, sometimes multinucleate, are noted together with less-characteristic mononuclear cells. Between the cells, acid mucopolysaccharide can be demonstrated by Ehrlich's hæmatoxylin, Hale's dialysed iron and meta-chromatic stains. In addition there is a variable amount of periodic acid–Schiff positive material, distinct from the acid mucopolysaccharide, which sometimes stains yellow with Van Gieson's fluid and sometimes stains red¹.