To analyze the myxomatous changes and the components of acidic glycosaminoglycans (GAG) of the mitral valve in aged patients with the mitral valve prolapse (MVP) syndrome, a pathological and histochemical study was performed on hearts of 18 autopsied cases with MVP. The histochemical study included toluidine blue Ohno's method, and 3 enzymatic digestion tests with streptomyces hyaluronidase, chondroitinase AC-II and chondroitinase ABC. The following results were obtained: 1. The incidence of MVP with mitral regurgitation among 2,060 elderly autopsy patients over 60 years of age was 0.87%. 2.
Pathological findings: marked prolapse was detected in the anterior leaflet of 3 patients, moderate prolapse in the anterior leaflet of 6 and moderate prolapse in the posterior leaflet of 5. Most patients showed greater prolapse in the anterior than in the posterior leaflets. The MVP of 11 patients (61%) was associated with tricuspid valve prolapse. 3. Histological findings: All cases exhibited thickening at the rough zone; 17 patients showed enlargement of the spongiosa layer, and 15 showed a decrease or disappearance of the fibrosa layer. All cases showed various degrees of change in the atrialis layer. The main site of myxomatous change in the mitral valve of MVP was the spongiosa layer of the rough zone. 4. Histochemical findings: Results using 3 methods of enzymatic digestion tests were positive in 13 patients, which suggested that the major component of increased GAG at the myxomatous changes in the mitral valve of MVP was hyaluronic acid, as did the results with Ohno's toluidine blue method.