Current concepts in the pathogenesis and treatment of ischemic mitral regurgitation
Under normal conditions, mitral valve competence is maintained by a complex interaction of the five components of mitral valve function: the ventricular wall, the fibrous annulus, the papillary muscles, the chordae tendineae, and the valve leaflets. Deran
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Mitral valve anatomy and physiology
Under normal conditions, mitral valve competence is maintained by a complex interaction of the five components of mitral valve function: the ventricular wall, the fibrous annulus, the papillary muscles, the chordae tendineae, and the valve leaflets. Derangements in any single component can produce valve dysfunction, but in ischemic incompetence, the primary defect is infarction of the ventricular wall and papillary muscles. With increasing interest in valvular reconstruction in ischemic mitral regurgitation, a detailed knowledge of mitral valve anatomy has become essential. The fibrous skeleton of the heart, to which the mitral valve attaches, is derived from the endocardial cushions [1]. The mitral annulus is a thin , incomplete ring of fibrous tissue , which is most apparent at two points , the right and left fibrous trigones (Fig . 1). The left fibrous trigone is situated at the left anterior aspect of the mitral ring and consists of fibrous tissue joining the mitral ring to the base of the aorta. The right fibrous trigone , or central fibrous body, lies in the midline of the heart and represents the confluence of fibrous tissue from the mitral valve , tricuspid valve, membranous septum , and posterior aspect of the base of the aorta .
Fig.!. Anatomic interrelationships of the atrioventricular valves. A is the anterior leaflet, P is the posterior leaflet , and S is the septal leaflet. The asteri sk represent s the area of the bundle of His
Supported by NIH Grants Nos . L09315, HL29536, HL17670
157 H. O. Vetter et al. (eds.), Ischemic Mitral Incompetence © Springer-Verlag Berlin Heidelberg 1991
Embryologically, the mitral valve is initially quadracuspid, and as development continues, the accessory or commissural cusps fuse with and become part of the lateral aspects of the posterior leaflet. Persistence of these fetal commissural cusps, especially at the posterior commissure, can produce scalloping of the lateral posterior leaflet or minor posterior leaflet defects. In most adults, however , only two leaflets are evident , the broader anterior leaflet and the narrower posterior leaflet. The anterior leaflet has a much longer base-to-margin length than the posterior leaflet; however, the annular attachment of the posterior leaflet is twice as great, so that the surface area of each leaflet is almost identical [2-4] . Both leaflets have a trapezoidal shape and attach by thin fibrous chordae tendineae to both the anterior and posterior papillary muscles. Stated differently, the chordae from each papillary muscle fan out and attach to nearly half of both cusp margins (Fig . 2). The commissures do not divide the leaflet tissue completely to the valve annulus, and the basal aspects at the commissures are composed of continuous valvular tissue
[2, 3].
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, • Fig. 2. Diagrammatic anatomy of the mitral apparatus . A, anatomy of the valve during leaflet closure ; B, the open valve showing relationships of the papillary muscles and chordal fans to the valve axis. (Reproduced fr
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