Mitral valve stenosis most cases, the diagnosis of mitral stenosis is most easily made by echocardiography, which shows left atrial enlargement, thick and calcified mitral valve with narrow and "fish-mouth"-shaped orifice and signs of right ventricular failure in advanced disease. It can also show decreased opening of the mitral valve leaflets, and increased blood flow velocity during diastole. The trans-mitral gradient as measured by Doppler echocardiography is the gold standard in the evaluation of the severity of mitral stenosis. Another method of measuring the severity of mitral stenosis is the simultaneous left and right heart chamber catheterization. The right heart catheterization (commonly known
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.