Tricuspid valve

The tricuspid valve, like the mitral valve, consists of a complex of anatomical structures, including the fibrous ring, cusps, tendinous chordae, papillary muscles, and adjacent sections of the right atrium and ventricle. Typically, the tricuspid valve, as its name suggests, has three cusps, sometimes some of which are split. A distinction is made between septal, anterior, and posterior, and the commissures are called, respectively, anterior-septal, anteroinferior, and posterior.

The fibrous ring that forms the tricuspid valve contains a greater number of elastic fibers relative to the fibrous ring of the mitral valve. The area adjacent to the septal region is a continuation of the membranous part of the interventricular septum. The conduction pathways of the heart pass near this area. The rest is looser and contains muscle fibers. The dimensions of the fibrous ring are more pronounced in the area of its adjacency to the right fibrous triangle and become thinner as it moves away from this triangle. The outer part of the fibrous ring adjacent to the anterior and posterior cusps changes in shape and size (by 19-40%) due to contraction and relaxation of the myocardium during the cardiac cycle.

The cusps that form the tricuspid valve also have a base, an overlap zone (body), and a closure zone. The valve cusps (2 to 6) are supported by tendinous chords and papillary muscles. The main one is the anterior one, not located on the anterior wall of the right ventricle. Together with the supraventricular crest, the septal trabecula ("moderator strand") and the parietal wall of the right ventricle, the anterior one divides the ventricular cavity into the inflow and outlet sections. The posterior papillary muscle is smaller. Small papillary muscles can be on the interventricular septum, sometimes the chords extend directly from the ventricular wall. Most often, there are 3-4 muscles, sometimes up to 7-10.

The tricuspid valve, like the mitral valve, has chords that are divided into chords of the 1st, 2nd and 3rd orders. The chords of the septal leaflet originate from the heads of small papillary muscles on the interventricular septum. The chords from the anterior papillary muscle are attached to the anterior leaflet, and the tendinous chords of the posterior leaflet originate from the group of posterior papillary muscles of the trabecular part of the septum. In the area of the anterior-septal commissure, the leaflets are supported by chords coming from the Lancisi muscle. The functional significance of the chords attached to different sections is not the same. The intersection of the chords of the base of the leaflet does not disrupt the closure function of the valve. The intersection of the chords of the overlap zone of one leaflet does not cause regurgitation, two or more leaflets - leads to valve insufficiency. Damage to the marginal chords of even one valve leads to a disruption of the closing function of such a formation as the tricuspid valve.

The relationship of the conduction system and the elements that form the tricuspid valve is important from a surgical point of view. In particular, the bundle of His runs parallel to the line of attachment of the septal leaflet of the tricuspid valve, and then through the right fibrous triangle and the fibrous ring in the area of the anterior-septal commissure (danger zone) is directed along the lower edge of the membranous septum. The depth of the bundle of His in the area of the septal leaflet is 1-2 mm. In case of hypertrophy of the myocardium of the right ventricle (in case of heart defects) and rheumatic damage to such a formation as the tricuspid valve, the bundle of His can be located at a depth of 2-4 mm. In addition, the right coronary artery runs quite close to the anterior segments of the fibrous ring (2-4 mm), especially in the area of the lateral commissure.