Papillary muscle approximation reduces systolic tethering forces and improves mitral valve closure in the repair of functional mitral regurgitation

• Type of Material: Article
• Authors: Samantha Zhan-Moodie, Emory University Hospital Midtown; Dong Xu, Emory University; Kirthana Sreerangathama Suresh, Emory University Hospital Midtown; Qi He, Emory University Hospital Midtown; Daisuke Onohara, Emory University; Kanika Kalra, Emory University Hospital Midtown; Robert Guyton, Emory University; Eric L Sarin, Emory University Hospital Midtown; Muralidhar Padala, Emory University
• Language: English
• Date: 2021-09-01
• Publisher: Elsevier Inc
• Publication Version: Final Published Version
• Copyright Statement: © 2021 The Authors
• License: Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1016/j.xjon.2021.04.008
• Title of Journal or Parent Work: JTCVS Open
• Volume: 7
• Start Page: 91
• End Page: 104
• Grant/Funding Information: This work was funded by grants from the National Heart, Lung and Blood Institute (NHLBI) (R01 HL135145, R01 HL133667, and R01 HL140325), INOVA Heart and Vascular Institute, and Carlyle Fraser Heart Center at Emory University Hospital Midtown.
• Keywords: ischemic mitral regurgitation; sub-annular repair; Mitral valve repair; annuloplasty; secondary mitral regurgitation; interpapillary muscle separation; heart failure; left ventricular remodeling
• Research Categories: Health Sciences, Medicine and Surgery

Abstract

Background: Undersizing mitral annuloplasty (UMA) to repair functional mitral regurgitation (FMR) lacks durability, as it forces leaflet coaptation without relieving the subleaflet tethering forces. In this biomechanical study, we demonstrate that papillary muscle approximation (PMA) before UMA can drastically relieve tethering forces and improve valve function, without the need for significant annular downsizing. Methods: An ex vivo model of FMR was used, in which pig mitral valves were geometrically perturbed to induce FMR, and the repairs were performed. Nine pig mitral valves were studied in the following sequence: normal (baseline), FMR, true-sized annuloplasty to 30 mm (true-sized ring [TSR]), and undersized annuloplasty to 26 mm (down-sized ring [DSR]), along with concomitant PMA at both ring sizes. Mitral regurgitation, valve kinematics, and chordal forces were measured and compared among the groups. Results: FMR geometry induced a mean regurgitant fraction of 16.31 ± 7.33% compared with 0% at baseline. TSR reduced the regurgitant fraction to 6.05 ± 5.63%, whereas DSR reduced it to 5.06 ± 6.76%. The addition of PMA before the use of these rings reduced the mean regurgitant fraction to 3.87 ± 6.79% with the TSR (TSR + PMA) and 3.71 ± 6.25% with the DSR (DSR + PMA). Mean peak anterior and posterior marginal chordal forces were elevated to 0.09 ± 0.1 N and 0.12 ± 0.1 N, respectively, with FMR and were not reduced by annuloplasty of either sizes. The addition of PMA significantly reduced these forces to 0.23 ± 0.02 N and 0.51 ± 0.04 N. Conclusions: This biomechanical study demonstrates that PMA relieves tethering forces, and concomitantly with annuloplasty it mobilizes the leaflets to achieve physiological valve closure. Such a result could be achieved without the need for extensive annular downsizing.