Mitral valve differences, opening when there is greater pressure in the left atrium than ventricle, and closing when there is greater pressure in the ventricle than atrium. In abnormal conditions, blood may flow backwards through the valve (mitral regurgitation) or the mitral valve may be narrowed (mitral stenosis). Rheumatic heart disease often affects the mitral valve; the valve may also prolapse with age, and be affected by infective endocarditis. The mitral valve is named after the mitre of a bishop, which resembles its flaps. The mitral valve is typically in area, and sits in the left heart between the left atrium and
Mitral valve prolapse "atrialis", "fibrosa", and "spongiosa". Patients with classic mitral valve prolapse have excess connective tissue that thickens the spongiosa and separates collagen bundles in the fibrosa. This is due to an excess of dermatan sulfate, a glycosaminoglycan. This weakens the leaflets and adjacent tissue, resulting in increased leaflet area and elongation of the chordae tendineae. Elongation of the chordae tendineae often causes rupture, commonly to the chordae attached to the posterior leaflet. Advanced lesions—also commonly involving the posterior leaflet—lead to leaflet folding, inversion, and displacement toward the left atrium. Echocardiography is the most useful method of diagnosing a prolapsed mitral valve.