Mitral valve stenosis secondary to mitral stenosis is severe, the P (pulmonic) component of the second heart sound (S) will become loud. An opening snap that is a high-pitch additional sound may be heard after the A (aortic) component of the second heart sound (S), which correlates to the forceful opening of the mitral valve. The mitral valve opens when the pressure in the left atrium is greater than the pressure in the left ventricle. This happens in ventricular diastole (after closure of the aortic valve), when the pressure in the ventricle precipitously drops. In individuals with mitral stenosis, the pressure in the
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.