Osseous metaplasia within native cardiac valves: clinicopathologic characterization of a histologic constituent with particular focus upon aortic valves.

Native cardiac valves may undergo calcification in the setting of chronic injury, subsequently impeding normal valve structure and function. In the same setting, there may be evidence of metaplasia-specifically osseous metaplasia-with lamellar bone admixed with dystrophic calcification. In this study, the histologic features of 123 native aortic valves (identified from 1094 sequentially reviewed native valves of all types that included a total of 754 aortic valves) with osseous metaplasia are focused upon, as well as correlation with other histopathologic features, and clinical and echocardiographic findings. Osseous metaplasia was identified in aortic and significantly less frequently in mitral valves, and never in tricuspid or pulmonic valves. Notable observations included that osseous metaplasia in aortic valves were seen in patients with greater body mass index, and less commonly identified in patients with a history of autoimmune disease. Aortic valves with osseous metaplasia were more commonly tricuspid (as opposed to bicuspid), and with smaller aortic valve area and greater peak and mean gradients. The rate of osseous metaplasia in aortic valves increased with increasing degree of stenosis and decreasing degree of regurgitation. The rates of the presence of chondromatous metaplasia, smooth muscle, arterial vessels, capillary bed formation, chronic inflammation, and hemosiderin laden macrophages were greater in aortic valves with osseous metaplasia compared to valves without osseous metaplasia. Further investigation is required to determine potential physiologic and/or pathologic consequence of the presence of valvular osseous metaplasia.