Off-pump transapical implantation of artificial chordae to correct MR is technically safe and feasible; however, it yields further potential for improvement of efficacy and durability. (Safety and Performance Study of the NeoChord Device [TACT]; NCT01777815).

Background-New insight into the 3D dynamic behavior of the mitral valve has prompted a reevaluation of annuloplasty ring designs. Force balance analysis indicates correlation between annulus forces and stresses in leaflets and chords. Improving this stress distribution can intuitively enhance the durability of mitral valve repair. We tested the hypothesis that saddle-shaped annuloplasty rings have superior uniform systolic force distribution compared with a nonuniform force distribution in flat annuloplasty rings. Methods and Results-Sixteen 80-kg pigs had a flat (nϭ8) or saddle-shaped (nϭ8) mitral annuloplasty ring implanted. Mitral annulus 3D dynamic geometry was obtained with sonomicrometry before ring insertion. Strain gauges mounted on dedicated D-shaped rigid flat and saddle-shaped annuloplasty rings provided the intraoperative force distribution perpendicular to the annular plane. Average systolic annular height to commissural width ratio before ring implantation was 14.0%Ϯ1.6%. After flat and saddle shaped ring implantation, the annulus was fixed in the diastolic (9.0%Ϯ1.0%) and systolic (14.3%Ϯ1.3%) configuration, respectively (PϽ0.01). Force accumulation was seen from the anterior (0.72NϮ0.14N) and commissural annular segments (average 1.38NϮ0.27N) of the flat rings. In these segments, the difference between the 2 types of rings was statistically significant (PϽ0.05). The saddle-shaped annuloplasty rings did not experience forces statistically significantly larger than zero in any annular segments. Conclusions-Saddle-shaped annuloplasty rings provide superior uniform annular force distribution compared to flat rings and appear to represent a configuration that minimizes out-of-plane forces that could potentially be transmitted to leaflets and chords.

Objectives The mitral valve annulus naturally conforms to a saddle shape in systole. This configuration is believed to put the leaflets into a lower-energy equilibrium with the annulus and subvalvular apparatus. Conventional flat annuloplasty rings restrict posterior leaflet motion, which may result in a “monocusp” valve, affecting valvular stress distribution. It is hypothesized that saddle-shaped annuloplasty rings cause less distortion of the physiologic leaflet geometry than do flat rings. Methods Twelve pigs were studied in an acute setting with 3-dimensional echocardiography and sonomicrometry before and after implantation of rigid flat (n = 5) and saddle-shaped (n = 7) annuloplasty rings. The rings were true sized to the annulus with equal anterior–posterior and commissure–commissure circumferential dimensions. The saddle-shaped rings had an annular height to commissural width ratio of 15%. Results Saddle-shaped rings maintained both leaflets operational (P <.01). Flat rings made the posterior leaflet immobile and the anterior leaflet aligned flat along the annulus in systole, effectively resulting in monoleaflet function. The average distance from the papillary muscle tips to the posterior annulus decreased by 2.4 ± 0.4 mm after flat ring implantation (P <.01). Conclusions Saddle-shaped annuloplasty rings provide better leaflet coaptation geometry than do flat rings by not hoisting the papillary muscles toward the posterior annulus through the commissural chordae, allowing greater leaflet mobility. This entails a potentially beneficial impact on valvular stress distribution that could affect durability of the repaired valve.

Overall, the chordal insertion site had little influence on the tension in the artificial neochordae compared with the interindividual variation. However, abnormal tension fluctuations in the transapically fixated neochordae might predispose to leaflet tears and early repair failure.

The major conclusion of this study is that, in the SVAS model, the remodelling process of the coronary artery is consistent with normalization of shear stress despite an increase in the circumferential stress. Furthermore, the remodelling of the zero-stress state is also dominated by flow overload.