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The tricuspid valve consists of three leaflets (anterior, posterior, and septal), the chordae tendinea, two discrete papillary muscles, the fibrous tricuspid annulus, and the right atrial and right ventricular myocardium (Fig. 46-1A). Valve function depends on coordination of all these components. The anterior leaflet is the largest. The septal leaflet is the smallest and arises medially directly from the tricuspid annulus above the interventricular septum. Because the small septal wall leaflet is fixed and is relatively spared from annular dilation, tricuspid annular sizing has been based on the dimension of the base of the septal leaflet.1,2 The posterior leaflet often has multiple scallops. The anterior papillary muscle provides chordae to the anterior and posterior leaflets, and the medial papillary muscle provides chordae to the posterior and septal leaflets. The septal wall gives chordae to the anterior and septal leaflets. There may be accessory chordal attachments to the right ventricular free wall and the moderator band.
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Right ventricular dysfunction and dilation lead to chordal tethering contributing to loss of leaflet apposition.2 In addition, dilation of the free wall of the right ventricle results in tricuspid annular enlargement, primarily in its anterior/posterior (mural) aspect, resulting in significant functional TR (fTR) as a result of leaflet malcoaptation3 (Fig. 46-1B).
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The tricuspid annulus has a complex three-dimensional structure, which differs from the more symmetric "saddle-shaped" mitral annulus. The tricuspid annulus is dynamic and can change markedly with loading conditions. During the cardiac cycle, there is a ∼20% reduction in annular circumference (∼30% reduction in annular area) with atrial systole.4,5 This distinct shape has implications for the design and application of currently available annuloplasty rings in the tricuspid position. Most commercially available rings or bands are essentially planar except for the Edwards MC3 annuloplasty system.
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Fukuda et al.4 studied the shape and movement of the healthy and diseased tricuspid annulus performing a real-time three-dimensional transthoracic echocardiographic study. Healthy subjects had a nonplanar, elliptical-shaped tricuspid annulus, with the posteroseptal ...