Chordal "Translocation" for Functional Mitral Regurgitation (MR) ----
Towards Another Surgical Contribution in the Era of Percutaneous Vavle Treatment
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Objective: Chordal cutting method is tried for mitral valve tenting in functional MR such as ischemic MR. However, mitral valvular-ventricular continuity, especially secondary (i.e. strut) chordae tendineae (CT) of the anterior leaflet (AL), is known to be important for LV dimension and function. The secondary CT from papillary muscle (PM) are attached to the AL on the LV side and the anatomical direction runs toward mid-anterior mitral annulus (MA), so does force direction. Thus, apart from elimination of MR, chordal cutting method may deteriorate LV function. To maintain the valvular-ventricular continuity after the chordal cutting, we developed "translocation" of the secondary CT so that the force direction is maintained identical or similar to natural one. (Figure. Mitral valve tenting and chordal " translocation")
Methods: Six mongrel dogs had sonomicrometry crystal markers implanted to the LV, MA, and PMs under cardiopulmonary bypass (CPB). After the secondary CT of AL from both PMs were resected, each PM tip was connected to mid-anterior MA with 4-0 polypropylene. Polypropylenes as artificial CT were taken out through the rubber catheter via MA and then left atrium to control the chordal tension from outside thereafter. The condition that the chordae were released was defined as "redundant". The chordal tension that the polypropylenes were pulled with the 15gm weight was defined as "taut". After weaning off cardiopulmonary bypass, hemodynamic and three-dimensional marker data were acquired. The chordal tension was expressed by the reduced length (mm) between each PM tip and mid-anterior MA at end-diastole.
Results: The chordal length between mid-anterior MA and anterior and posterior PM tips during "taut" are 2.2±0.6 and 1.6±0.8mm respectively. With "redundant" condition, the LV function was moderately impaired in part because of long aortic cross-clamp time of 112.3 ± 18.3 minutes. With "taut" condition, however, end-systolic elastance (Ees) improved (1.8 ± 0.24 with "redundant" to 2.69 ± 0.89 mmHg/mL with "taut", P=0.012), and so did preload recruitable stroke work (PRSW) (41.2 ± 12 to 58.1 ± 19.7 mmHg, P=0.013) and short axis fractional shortening (FS) (10.1 ± 2.9 to 12.2 ± 3.7%, P=0.011). There was no difference in the dimension of the long axis between "redundant" and "taut".
Conclusions: "Translocation" of the secondary CT after chordal cutting improved LV systolic function compared to chordal cutting alone.
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