Abstract

The mitral valve is composed of leaflets, cords, and papillary muscles which must work in combination for the valve to function properly. The valve leaflets have three distinct layers, the atrialis, the spongiosa, and the fibrosa. Pathological changes affecting these structures may result in either stenosis or regurgitation of the valve and their consequential clinical symptoms and signs. The appearance of the valve changes with increasing age. Age-related changes include thickening of the valve leaflet substance, fatty streaks of the leaflets, nodular thickening along the lines of coaptation, and annular calcification. Diseases affecting the mitral valve include prolapse, rheumatic disease, infectious endocarditis, non-bacterial thrombotic endocarditis, hypertrophic cardiomyopathy, and congenital disease. Both prolapse and rheumatic disease show valve leaflet thickening with calcification, while prolapse shows myxomatous degeneration. Both infectious endocarditis and non-bacterial thrombotic endocarditis show vegetations on the atrial leaflet surfaces. These two conditions may only be distinguished on histology as a diagnosis of non-bacterial thrombotic endocarditis should only be made when the valve is devoid of bacterial colonies and acute inflammation. Advances in mitral valve interventions, both surgical and transvascular, are discussed along with their complications.