Saddle-shaped mitral valve annuloplasty rings improve leaflet coaptation geometry

Abstract

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.

Is Physiologic Annular Dynamics Preserved After Mitral Valve Repair With Rigid or Semirigid Ring?

“…Moreover, few would argue that the flexible band is unlikely to retain a saddle shape if the native annulus was flattened in the first place. Additionally, the C-shaped flexible band is inherently unable to restore the 3:4 (vertical to transverse) annular physiologic relationship originally proposed by Carpentier and colleagues [5].…”

“…Carpentier and associates [5] designed the annuloplastic ring to remodel the annulus into the shape it takes in the systolic phase. Because the mitral valve experiences the highest stress during this phase, this configuration restores maximal leaflet coaptation.…”

“…Mitral valve repair with an annuloplasty ring is effective and the gold standard strategy for degenerative mitral valve insufficiency. At present, many kinds of annular rings are available based on individual concepts, a saddle-shaped ring has been developed to recover the mitral annulus physiologically, and the efficacy for the mitral complex has been analyzed in animal models [5][6][7]. According to those reports, maintaining or recovering the physiologic three-dimensional annular shape can reduce the leaflet strain and is important for the long-term valve function.…”

Quantitative Analysis of Mitral Valve Morphology in Mitral Valve Prolapse With Real-Time 3-Dimensional Echocardiography

“…Taken together, the findings of both Nguyen et al and the present study have lent strong support to our hypothesis that the annular flattening observed in MVP was not an epiphenomenon of MR but a determinant factor. Moreover, a decrease in annular nonplanarity, whatever its cause, will exert increased tension on the leaflets and chords, [30][31][32] promoting rupture of mechanically weakened chords and the progressive disease seen clinically. MR begets MR.…”

Simultaneous in- and out-of-plane Mitral Valve Annular Force Measurements

“…13 The lower area and saddle shaped configuration in systole establishes a favourable leaflet and chordae tendineae stress distribution 11 providing superior leaflet coaptation 9 and annular stress distribution. Hence saddle shaped annuloplasty rings may be advantageous compared to a flat rigid ring.…”