Raymond Read and his colleagues reported a series of nine patients, aged from 14 to 49 years, with severe mitral or aortic valve regurgitation. None of these patients had a history of rheumatic fever. A great number of these patients underwent mitral valve replacement and the specimens were used for histological analysis. The authors introduced the term "floppy valve" based on the gross appearance of the valve intraoperatively. Regarding the histological findings, the case four is very characteristic and similar observations were reported in other mitral valve cases:
"...It was obvious that most of the collagenous structure of the cusps had been replaced with basophilic-staining mucoid material containing stellate fibroblasts. Special stains revealed an increase in mucopolysaccharide."
In the discussion of their work, the authors wrote:
"These nine patients have in common an unusual histologic appearance of their aortic or mitral valve leaflets. Varying degrees of hyalinization, disruption, and loss of the normal connective-tissue architecture was accompanied by an increase in ground substance and, in some instances fibrosis. There was a remarkable absence of the usual signs of inflammation [in reference to rheumatic valve disease]. The picture is that of myxomatous valvular transformation."
Read's study was among the first publication on the histological analysis of the mitral valve affected by degenerative disease. The authors introduced two new terminologies, floppy valve and valvular myxomatous transformation to describe their findings.
These histologic findings were further confirmed by Pomerance and Trent in 1969 and 1970 respectively. Trent's histological description was as follows:
"Dense collagenous tissue thickened the auricularis and ventricularis layers in the distal two thirds of the anterior mitral leaflet and the posteromedial and anterolateral scallops of the posterior leaflet. The spongiosa of the lengthened middle scallop was thickened by myxomatous , relatively acellular connective tissue (Fig. 4). Also, in the distal two thirds of its length progressively widening bands of connective tissue overlay the auricularis and ventricularis. On the ventricular side of the scallop this connective tissue was continuous with that thickening the chordae tendineae. Areas of the fibrosa in this scallop were disrupted by pockets of lossely textured connective tissue, a change that became more obvious as one progressed distally along the scallop. the chordae tendineae to the middle scallop were thickened by dense collagenous connective tissue deposited on their endothelial surfaces (Fig. 5). They did not show myxomatous change."
Pomerance A. Ballooning deformity (mucoid degeneration) of atrioventricular valves. Brit Heart J 1969;31:343-51
Trent JK, Adelman AG, Wigle ED, Silver MD. Morphology of a prolapsed posterior mitral valve leaflet. Am Heart J 1970;79:539-43