Mitral valve annulus

Numerous companies have developed devices and techniques to treat mitral annular dilatation percutane-ously. Most of these devices take advantage of the close anatomic proximity of the coronary sinus to the posterior aspect of the mitral valve annulus, and involve the placement of a prosthetic device in the coronary sinus to decrease the anterior-posterior diameter of the mitral valve annulus, thereby improving mitral leaflet coaptation. Other techniques involve percutaneous direct plication of the mitral annulus with sutures or the use of a bridge to connect a coronary sinus anchor and a septal anchor. 

Ormiston, J.A., Shah, P.M., Tei, C., and Wong, M. 1981. Size and motion of the mitral valve annulus in man a two-dimensional echocardiographic method and findings in normal subjects. Circulation 64 113-120. 

A prosthetic mitral valve (St Jude Medical Silzone) that had been implanted in a 72-year-old woman became partially detached 4 months later, causing acute cardiac failure. The mitral annulus was ulcerated and there were multiple erosions in the tissues in contact with the valve. Histology showed chronic inflammation. 

Normal mitral valve function requires intact leaflet structure, preserved subvalvular apparatus (i.e., chordae tendinae and papillary muscles), and a nondi-lated mitral annulus. Disruption of any one of these elements can lead to regurgitation of blood into the left atrium under the high pressure of left ventricular systole. 

The mitral (Figure 55.5) and tricuspid valves are similar in structure with both valves composed of four primary elements (1) the valve annulus, (2) the valve leaflets, (3) the papillary muscles, and (4) the chordae tendineae. The base of the mitral leaflets form the mitral annulus, which attaches to the atrial and ventricular walls, and aortic root. At the free edge of the leaflets, the chordae tendinae insert at multiple locations and extend to the tips of the papillary muscles. This arrangement provides continuity between the valve and ventricular wall to enhance valvular function. The valvular apparatus, or complex, requires an intricate interplay between all components throughout the cardiac cycle. 

The mitral leaflet tissue can be divided into both a rough and clear zone. The rough zone is the thicker part of the leaflet and is defined from the free edge of the valve to the valve s line of closure. The term rough is used to denote the texture of the leaflet due to the insertion of the chordae tendineae in this area. The clear zone is thinner and translucent and extends from the line of closure to the annulus in the anterior leaflet and to the basal zone in the posterior leaflet. Unlike the mitral valve, the tricuspid valve has three leaflets (1) an anterior leaflet, (2) a posterior leaflet with a vciriable number of scallops, and (3) a septal leaflet. The tricuspid valve is larger and structurally more complicated than the mitral valve and the separation of the valve tissue into distinct leaflets is less pronounced than with the mitral valve. The surface of the leaflets is similar to that of the mitral valve however, the basal zone is present in all of the leaflets [Silver et al., 1971]. 

Another area of interest has been the motion of the mitral valve complex. The heart moves throughout the cardiac cycle similarly, the mitral apparatus moves and changes shape. Recent studies have been conducted which examined the three-dimensional dynamics of the mitral annulus during the cardiac cycle [Ormiston et al., 1981 Komoda et al., 1994 Pai et al., 1995 Glasson et al., 1996]. These studies... 

He, S., Lemmon, J.D., Weston, M.W., Jensen, M.O., Levine, R.A., and Yoganathan, A.P. 1999. Mitral valve compensation for annular dilatation in vitro study into the mechanisms of functional mitral regurgitation with an adjustable annulus model. /. Heart Valve Dis. 8 294—302. 

Silverman, M.E. and Hurst, J.W 1968. The mitral complex interaction of the anatomy, physiology, and pathology of the mitral annulus, mitral valve leaflets, chordae tendineae and papillary muscles. Am. Heart J. 76 399 18. 

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