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

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 nonphysiological three-dimensional shapes, but not saddle-shaped rigid rings or flexible bands, increase AML strains

In vivo dynamic strains of the ovine anterior mitral valve leaflet

Understanding the mechanics of the mitral valve is crucial in terms of designing and evaluating medical devices and techniques for mitral valve repair. In the current study we characterize the in vivo strains of the anterior mitral valve leaflet. On cardiopulmonary bypass, we sew miniature markers onto the leaflets of 57 sheep. During the cardiac cycle, the coordinates of these markers are recorded via biplane fluoroscopy. From the resulting four-dimensional data sets, we calculate areal, maximum principal, circumferential, and radial leaflet strains and display their profiles on the averaged leaflet geometry. Average peak areal strains are 13.8 +/- 6.3%, maximum principal strains are 13.0 +/- 4.7%, circumferential strains are 5.0 +/- 2.7%, and radial strains are 7.8 +/- 4.3%. Maximum principal strains are largest in the belly region, where they are aligned with the circumferential direction during diastole switching into the radial direction during systole. Circumferential strains are concentrated at the distal portion of the belly region close to the free edge of the leaflet, while radial strains are highest in the center of the leaflet, stretching from the posterior to the anterior commissure. In summary, leaflet strains display significant temporal, regional, and directional variations with largest values inside the belly region and toward the free edge. Characterizing strain distribution profiles might be of particular clinical significance when optimizing mitral valve repair techniques in terms of forces on suture lines and on medical devices

How do annuloplasty rings affect mitral leaflet dynamic motion?

Objectives: To define the effects of annuloplasty rings (ARs) on the dynamic motion of anterior mitral leaflet (AML) and posterior mitral leaflet (PML). Methods: Fifty-eight adult, Dorsett-hybrid, male sheep (49 5 kg) had radiopaque markers inserted: eight around the mitral annulus, four along the central meridian (from edge to annulus) of the AML (#A(1)-#A(4)) and one on the PML edge (#P-1). True-sized Edwards Cosgrove (COS, n = 12), St Jude RSAR (St. Jude Medical, St. Paul, MN, USA) (n = 12), Carpentier-Edwards Physio (PHYSIO, n = 12), Edwards IMR ETlogix (ETL, n = 10) or Edwards GeoForm (GEO, n = 12) ARs were implanted in a releasable fashion. Under acute open-chest conditions, 4D marker coordinates were obtained using biplane videofluoroscopy with the respective AR inserted (COS, RSAR, PHYSIO, ETL and GEO) and after release (COS-Control, RSAR-Control, PHYSIO-Control, ETL-Control and GEO-Control). AML and PML excursions were calculated as the difference between minimum and maximum angles between the central mitral annular septal-lateral chord and the AML edge markers (alpha(1exc)-alpha(4exc)) and PML edge marker (beta(1exc)) during the cardiac cycle. Results: Relative to Control, (1) RSAR, PHYSIO, ETL and GEO increased excursion of the AML annular (alpha(4exc): 13 +/- 6 vs 16 +/- 70 degrees(star), 16 +/- 7 degrees vs 23 +/- 10 degrees(star), 12 +/- 4 degrees vs 18 +/- 9 degrees(star), 15 +/- 10 degrees(star) vs 20 +/- 9 degrees(star), respectively) and belly region (alpha(2exc): 41 +/- 10 degrees(star) vs 45 +/- 10 degrees(star), 42 +/- 8 degrees vs 45 +/- 6, n.s., 33 +/- 13 degrees vs 42 +/- 14 degrees(star), 39 +/- 6 degrees(star) vs 44 +/- 60 degrees(star), respectively, alpha(3exc): 24 +/- 9 degrees vs 29 +/- 11 degrees(star), 28 +/- 10 degrees vs 33 +/- 10 degrees(star), 16 +/- 9 degrees vs 21 +/- 12 degrees(star), 25 +/- 7 degrees vs 29 +/- 9 degrees(star), respectively), but not of the AML edge (alpha(1exc): 42 +/- 8 degrees(star) vs 44 +/- 8 degrees, 43 +/- 8 degrees vs 41 +/- 6 degrees, 42 +/- 11 vs 46 +/- 10 degrees, 39 +/- 9 degrees vs 38 +/- 8 degrees, respectively, all n.s.). COS did not affect AML excursion (ale c: 40 +/- 8 degrees vs 37 +/- 8 degrees, alpha(2exc): 43 +/- 9 degrees vs 41 +/- 9 degrees, alpha(3exc): 27 +/- 11 degrees vs 27 +/- 10 degrees, alpha(4exc): 18 +/- 8 degrees vs 17 +/- 7 degrees, all n.s.). (2) PML excursion (file,x) was reduced with GEO (53 5 vs 43 60*), but unchanged with COS, RSAR, PHYSIO or ETL (53 13 vs 52 150, 50 13 vs 49 + 10, 55 + 5 vs 55 7, 52 8 vs 58 6, respectively, all n.s); star = p < 0.05. Conclusions: RSAR, PHYSIO, ETL and GEO rings, but not COS, increase AML excursion of the AML annular and belly region, suggesting higher anterior mitral leaflet bending stresses with rigid rings, which potentially could be deleterious with respect to repair durability. The decreased PML excursion observed with GEO could impair left ventricular filling. Clinical studies are needed to validate these findings in patients. (C) 2010 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved

Anterior mitral leaflet curvature in the beating ovine heart: a case study using videofluoroscopic markers and subdivision surfaces

The implantation of annuloplasty rings is a common surgical treatment targeted to re-establish mitral valve competence in patients with mitral regurgitation. It is hypothesized that annuloplasty ring implantation influences leaflet curvature, which in turn may considerably impair repair durability. This research is driven by the vision to design repair devices that optimize leaflet curvature to reduce valvular stress. In pursuit of this goal, the objective of this manuscript is to quantify leaflet curvature in ovine models with and without annuloplasty ring using in vivo animal data from videofluoroscopic marker analysis. We represent the surface of the anterior mitral leaflet based on 23 radiopaque markers using subdivision surfaces techniques. Quartic box-spline functions are applied to determine leaflet curvature on overlapping subdivision patches. We illustrate the virtual reconstruction of the leaflet surface for both interpolating and approximating algorithms. Different scalar-valued metrics are introduced to quantify leaflet curvature in the beating heart using the approximating subdivision scheme. To explore the impact of annuloplasty ring implantation, we analyze ring-induced curvature changes at characteristic instances throughout the cardiac cycle. The presented results demonstrate that the fully automated subdivision surface procedure can successfully reconstruct a smooth representation of the anterior mitral valve from a limited number of markers at a high temporal resolution of approximately 60 frames per minute

Anterior Mitral Leaflet Curvature During the Cardiac Cycle in the Normal Ovine Heart

Background-The dynamic changes of anterior mitral leaflet (AML) curvature are of primary importance for optimal left ventricular filling and emptying but are incompletely characterized