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This two-part article examines the histologic and morphologic basis for stenotic and purely regurgitant mitral valves. In Part I, conditions producing mitral valve stenosis are reviewed. In over 99% of stenotic mitral valves, the etiology is rheumatic disease. Other rare causes of mitral stenosis include congenital malformed valves, active infective endocarditis, massive annular calcium, and metabolic or enzymatic abnormalities. In Part II, conditions producing pure mitral regurgitation will be discussed. In contrast to the few causes of mitral stenosis, the causes of pure (no element of stenosis) mitral regurgitation are multiple. Some of the conditions producing pure regurgitation include floppy mitral valves, infective endocarditis, papillary muscle dysfunction, rheumatic disease, and ruptured chordae tendinae.

We have evaluated the nature of Aschoff cells within Aschoff bodies seen in 35 of 100 excised left atrial appendages from cases of rheumatic mitral stenosis who underwent closed mitral valvotomy. These were tested using a panel of monoclonal and polyclonal antisera by the indirect immunoperoxidase staining for leucocyte common antigen, macrophage, desmin, vimentin, alpha-1-antitrypsin, alpha-1-antichymotrypsin, lysozyme, acid phosphatase and nonspecific esterase. The Aschoff cell gave strong reactivity with monoclonal antisera to vimentin, macrophage and variable reaction with polyclonal antisera known to recognise macrophages/histiocytes in tissues, namely alpha-1-antitrypsin, alpha-1-antichymotrypsin and lysozyme. These were also strongly positive for acid phosphatase and nonspecific esterase. The Aschoff cell lacked affinity for desmin and only an occasional cell in 4 out of 20 and 6 out of 35 cases showed a weak reaction with myoglobin and leucocyte common antigen, respectively. Intense consistent reactivity with several histiocytic markers affirms the genesis of these cells from macrophages/histiocytes and not muscle cells; a controversy which must be laid to rest!

Among 543 necropsy patients over age 14 years with severe chronic valvular heart disease, Aschoff bodies were found in 11 patients (2%). The ages of the 11 patients ranged from 18 to 68 years (avg. 38), and nine had had a history of acute rhematic fever earlier in life. Clinically, nine of the 11 patients had mitral stenosis with or without dysfunction of one or more other cardiac valves, one had isolated aortic regurgitation, and one had both mitral and aortic regurgitation. All 11 patients had diffuse fibrous thickening of the mitral valve leaflets, and all but one had diffuse anatomic lesions of at least one other cardiac valve. No patient with anatomic lesions limited to the aortic valve had Aschoff bodies. Thus, among patients with chronic valvular heart disease, Aschoff bodies, the only anatomic lesion pathognomonic of rheumatic heart disease, indicate diffuse anatomic lesions of the mitral leaflets and usually also anatomic lesions of one or more other cardiac valves. The functional mitral lesion is usually stenosis.