Histopathological evaluation of chronic rheumatic mitral valve stenosis: the association with clinical presentation, pathogenesis, and management at a National Cardiac Institute, Tanzania.

Aims: The histopathology of mitral valve (MV) tissues have been reported in necropsy and retrospective studies. We prospectively studied the histopathological changes in rheumatic mitral stenosis using advanced techniques and corroborated these with clinical presentation, pathogenesis, and management.

Methods: From January 2020 to February 2021, surgically excised rheumatic stenotic MV from 54 Tanzanian patients were studied. These were examined using hematoxylin-eosin, von Kossa staining, and immunohistochemistry.

Results: The median (range) age of patients was 39 (14-57) years with 34 (63%) females. Secondary prophylaxis was given to 7 (13%) patients and 2 (3.7%) had evidence of rheumatic fever (RF). With hematoxylin-eosin, 37 (68.5%) specimens showed fibrinoid degeneration (FD), 44 (81.5%) leucocytic infiltrates, 6 (11.1%) Aschoff nodules, 30 (55.6%) calcification, and 39 (72.2%) fibrosis. Thirty-five (64.8%) specimens were positive to von Kossa. The proportion of specimens positive for CD3, CD20, CD68, and CD8 were 46 (85.2%), 35 (64.8%), 39 (72.2%), and 8 (14.8%) respectively. Valvular calcium was high among older patients, males and with a higher trans-MV gradient. The degree of inflammatory cellular infiltration was associated with valvular calcification, FD with ARF, leucocytic infiltrates with disease duration of <10 years, and fibrosis with the absence of atrial fibrillation. C-reactive protein and anti-streptolysin titres were high in CD20 and CD8 staining cells.

Conclusion: This study confirms that high MV calcium are found in patients who are old, male, and with severe mitral stenosis. The association between clinical parameters with histopathological-immunohistochemical studies observed in our study provides new insight to disease presentation. We found a low rate of secondary prophylaxis and two patients with ARF. Our findings are comparable with those from other countries suggesting similar pathogenesis and thus intervention modalities. This is the first study on mitral valve histopathology to be reported from Africa.