Saddle-Shaped Mitral Valve Annuloplasty Rings Experience Lower Forces Compared With Flat Rings

Abstract

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.

Comparison of the mitral valve morphologies of Cavalier King Charles Spaniels and dogs of other breeds using 3D transthoracic echocardiography

“…In the present study, the differences between the MV morphology of CKCSs and dogs of other breeds did not include 3D indexes of annular nonplanarity, such as AHCWR or NPA, which have been associated with increased leaflet stress 8, 10. However, leaflets’ spatial configuration, is another fundamental characteristic that potentially minimizes valvular peak stress 8, 19.…”

“…Specifically, the MV of CKCSs was flatter than in dogs of other breeds, having a reduced AnH and reduced leaflet tenting, as demonstrated by reduced TnH, TnA, and nTnV (Figure 2), and, relative to dogs of other breeds, the AAo‐AP Angle of CKCS was greater. The morphology of the MV has an effect on the stress acting on the leaflets and on the tensioning apparatus,8, 9, 10, 11 and therefore an abnormal valvular shape and annular configuration could alter the forces applied on the MV during each cardiac cycle. Although most experimental evidence suggests that annular flattening is the source of increased valvular stress,8, 9, 10, 11 it is implied that this increase in stress is mediated through changes in leaflet geometry.…”

“…The morphology of the MV has an effect on the stress acting on the leaflets and on the tensioning apparatus,8, 9, 10, 11 and therefore an abnormal valvular shape and annular configuration could alter the forces applied on the MV during each cardiac cycle. Although most experimental evidence suggests that annular flattening is the source of increased valvular stress,8, 9, 10, 11 it is implied that this increase in stress is mediated through changes in leaflet geometry. Indeed, finite element analysis models demonstrating increased valvular stress associated with annular flattening have tested hypotheses that relate to the degree of flatness of the leaflets, not to flatness of the annulus 8.…”

A Comparison of 2 Mitral Annuloplasty Rings for Severe Ischemic Mitral Regurgitation: Clinical and Echocardiographic Outcomes

“…They might provide a more favorable and uniform annular force distribution when compared to the flat rings. 25,26 By diminishing mitral leaflet strain and improving leaflet coaptation geometry, saddle-shaped annuloplasty may thus enhance repair durability. Therefore, the mitral valve reconstruction primarily aims at restoring not only a normal valve anatomy but also a normal valve function.…”

Surgical approaches to treatment of ischemic mitral regurgitation (literature review)

“…[19], M. Jensen и соавт. [20]). Аннулопластика с использо-ванием плоских колец нарушает изгиб створок (I. Salgo и соавт.…”