Abstract
The chordae tendinae connect the papillary muscles to the mitral valve. While the first-order chordae serve to secure the leaflets to maintain valve closure and prevent mitral valve prolapse, the second-order chordae are believed that they play a role in maintaining normal LV size and geometry. The papillary muscles, from where the chordae tendinae originate, function as shock absorbers that compensate for the geometric changes of the left ventricular wall. The second-order chordae connect the PMs to both trigons under tension. The tension distributed towards the second-order chordae has been demonstrate to be more than three-fold that in the first-order counterpart. Cutting the second-order chordae puts all the tension on the first-order chordae, that can go closer to their rupture point. However, it has been experimentally demonstrated that the tension where the first-order chordae break is 6.8 N, by far higher than the maximal tension reached, that is 0.4 N. Even if the clinical reports have been favorable, the importance of cutting the second-order chordae to recover curvature of the anterior leaflet and increasing the coaptation length between the mitral leaflet has been slowly absorbed by the surgical world. Nevertheless, there are progressive demonstrations that chordal tethering affects the anterior leaflet not only in secondary, but also in primary mitral regurgitation, having a not negligeable role in the long-term outcome of mitral repair.
The chordae tendinae (CT) are strong and fibrous connections between the papillary muscles (PMs) and the leaflets of the mitral valve (MV). Each PM provides CT to its closest half of the anterior and the posterior MV leaflets.
According to the insertion site, CT can be classified as leaflet, commissural or cleft CT. Leaflet CT insert at the border (first-order or marginal CT) or at the ventricular surface of the leaflet (second-order or basal CT), close to the rough zone. The basal CT that insert to the anterior leaflet (AL), if thicker and stronger than the others, are called strut chordae. Commissural and cleft CT are typically fan-shaped.
The CT, after their origin, divide in branches, usually 3 to 6. In general, one goes to the margin of the leaflet, another one to the border between the rough and the clear zone and a third one to the clear zone. The number of first order CT inserted to a single cusp is 22 and of second order CT is 101. There are as well third-order chordae that arise from the wall of the left ventricle (LV) and insert exclusively into the posterior leaflet (PL).
CT are not vascularized. They convey blood to and from the leaflets in vessels coursing the length of their shafts, but the absence of branching vasculature suggests CT derive their nutrient supply by diffusion2. It is noteworthy to underline that neovascularization due to mechanical or hypoxic stress weakens the CT and is at the basis of chordal rupture3.