Abstract 16874: Papillary Muscle Approximation Relieves Tethering Forces and Improves Systolic Mitral Valve Kinematics in an Ex-Vivo Model of Functional Mitral Regurgitation

Introduction: Undersizing annuloplasty (UA), which is the current standard to correct functional mitral regurgitation (FMR) is effective, but the resulting unphysiological systolic geometry causes FMR recurrence. On the other hand, papillary muscle approximation (PMA), a sub-annular technique, reduces inter-papillary separation and tethering forces, mobilizing the leaflets. Objective: To investigate the effect of PMA on mitral valve tethering forces and systolic coaptation geometry, compared to UA. Methods: A left heart model with pig mitral valves was used to create a tethered mitral valve geometry and to perform surgical repairs ( Fig. A ). Mitral valve geometry, and marginal and strut chordal forces acting on both leaflets were measured. Eight individual pig valves (n=8) were studied, with hemodynamic and mechanics data acquired at normal geometry (BASELINE) ( Fig. B) , after tethering (FMR) ( Fig. C) , undersizing annuloplasty (UA) to size 34 (Edwards Lifesciences Physio ring) ( Fig. D) , papillary muscle approximation (PMA), and combination (PMA+UA). Results: Tenting height, which increased after FMR, was least with PMA (0.46 cm± 0.21) and PMA+UA (0.50± 0.16) but remained significantly high with UA (0.73±0.21, p=0.03) ( Fig. E ). Excursion angles of anterior and posterior leaflets were restored close to baseline values after PMA and PMA+UA but remained significantly tethered after UA ( Fig. F & G ). Tethering of the valve increased the strut and marginal chordae forces from 0.47 and 0.14 N to 0.89 and 0.21 N, an increase of 89% and 50% respectively. PMA reduced the forces by 47% and 34%, and PMA+UA reducing it by 43% and 34%to 0.51 while UA only reduced it by 15% and 20% ( Fig. H & I ). Conclusion: PMA significantly reduced the tethering forces on both marginal and strut chordae of both leaflets. Decrease in tethering forces restored the physiologically favorable valve geometry enabling better leaflet mobility and coaptation compared to UA.