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.