Histologic changes that simulate atheroma and involve lipid deposition and inflammatory cell infiltration of the leaflets have been described in patients with early degenerative changes in the aortic leaflets. Occasionally, mitral annular calcification extends onto the valve leaflets, causing stenosis. The predominant hemodynamic manifestation of endocarditis is valvular regurgitation. In rare cases, large vegetations lead to valvular stenosis. Acute ischemia or infarction of a papillary muscle or of the wall to which the papillary muscle is attached leads to impaired leaflet coaptation and mitral regurgitation.
Regurgitation can be severe and can vary with the severity of the ischemia.
Papillary head rupture or, more rarely, muscle rupture leads to catastrophic regurgitation that is often fatal. Significant regurgitation and stenosis rarely occur acutely but are seen with scarring from chronic disease. Valvular involvement in rheumatoid arthritis is common and leads to valve thickening but is usually not of hemodynamic significance. Many other conditions can affect valve leaflets. Amyloid disease causes valvular thickening but rarely causes significant stenosis.