Rigid, Complete Annuloplasty Rings Increase Anterior Mitral Leaflet Strains in the Normal Beating Ovine Heart

Abstract

Background Annuloplasty ring or band implantation during surgical mitral valve repair perturbs mitral annular dimensions, dynamics and shape, which have been associated with changes in anterior mitral leaflet (AML) strain patterns and suboptimal long-term repair durability. We hypothesized that rigid rings with non-physiological 3-D shapes, but not saddle-shaped rigid rings or flexible bands, increase AML strains. Methods and Results Sheep had 23 radiopaque markers inserted: 7 along the anterior mitral annulus and 16 equally spaced on the AML. True-sized Edwards Cosgrove flexible, partial band (COS, n=12), rigid, complete St. Jude saddle-shaped annuloplasty ring (RSAR, n=12), Carpentier-Edwards Physio (PHYSIO, n=12), Edwards IMR ETlogix (ETL, n=11) and Edwards GeoForm (GEO, n=12) annuloplasty rings were implanted in a releasable fashion. Under acute open-chest conditions, four-dimensional marker coordinates were obtained using biplane videofluoroscopy along with hemodynamic parameters with the ring inserted and after release. Marker coordinates were triangulated and the largest maximum principal AML strains were determined during isovolumetric relaxation (IVR). No relevant changes in hemodynamics occurred. Compared to the respective Control state, strains increased significantly with RSAR, PHYSIO, ETL and GEO (0.14±0.05 vs. 0.16±0.05, p=0.024, 0.15±0.03 vs. 0.18±0.04, p=0.020, 0.11±0.05 vs. 0.14±0.05, p=0.042 and 0.13±0.05 vs. 0.16±0.05, p=0.009), but not with COS (0.15±0.05 vs. 0.15±0.04,p=0.973). Conclusions Regardless of 3-D shape, rigid, complete annuloplasty rings, but not a flexible, partial band, increased AML strains in the normal beating ovine heart. Clinical studies are needed to determine if annuloplasty rings affect AML strains in patients, and, if so, whether ring-induced perturbations in leaflet strain states are linked to repair failure.

Characterization of Mitral Valve Annular Dynamics in the Beating Heart

“…The piecewise cubic spline approximated all experimentally acquired marker coordinates v n (t) extremely well with a maximum error at any time and any marker location of less than 0.07 cm. This value is on the order of the digitization error of 0.01 ± 0.03 cm of the marker technique 4,19,32,44. Moreover, we observed no local maxima in curvature close to the original marker locations indicating a good choice for the smoothing parameter k.Figure 3aillustrates the annular excursion of the mitral valve as a measure of left ventricular long-axis shortening,25,43 displayed in an anterior view.…”

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

“…That may reduce the loading on the suture lines of the leaflet and potentially improve the repair durability, and also inhibit the progression of valve degeneration [6]. However, Bothe and colleagues [12] reported that the anterior leaflet strain was increased in the beating ovine heart when a complete rigid ring, either flat or three-dimensional, was implanted. In our study, both Physio II and RSR rings could restore the mitral annular three-dimensional saddle shape after the ring implantation.…”

A novel finite element-based patient-specific mitral valve repair: virtual ring annuloplasty

“…Previous studies have focused on the effect of types and size of the ring in animal models [5, 11], or utilized simplified FE MV models [11, 12]. Although these studies help us to understand the effect of ring implantation on restoration of MR, dynamic FE simulation using patient-specific MV models directly imported from clinical imaging data can provide improved biomechanical and physiological information of MV function, and help to better predict the degree of recovery to normal MV function following ring annuloplasty.…”

“…Mitral repair has been utilized as the most popular and most efficient surgical intervention for MR treatment rather than total valve replacement [4]. Undersized ring annuloplasty is commonly performed during MV repair to reduce dilated annular dimension [5]. An annuloplasty ring is implanted following complex reconstructive MV repairs to prevent potential reoccurrence of MR [6].…”