title: New mitral annular force transducer optimized to distinguish annular segments and multi-plane forces.
abstract: Limited knowledge exists about the forces acting on mitral valve annuloplasty repair devices. The aim of this study was to develop a new mitral annular force transducer to measure the forces acting on clinically used mitral valve annuloplasty devices. The design of an X-shaped transducer in the present study was optimized for simultaneous in- and out-of-plane force measurements. Each arm was mounted with strain gauges on four circumferential elements to measure out-of-plane forces, and the central parts of the X-arms were mounted with two strain gauges to measure in-plane forces. A dedicated calibration setup was developed to calibrate isolated forces with tension and compression for in- and out-of-plane measurements. With this setup, it was possible with linear equations to isolate and distinguish measured forces between the two planes and minimize transducer arm crosstalk. An in-vitro test was performed to verify the crosstalk elimination method and the assumptions behind it. The force transducer was implanted and evaluated in an 80kg porcine in-vivo model. Following crosstalk elimination, in-plane systolic force accumulation was found to be in average 4.0±0.1N and the out-of-plane annular segments experienced an average force of 1.4±0.4N. Directions of the systolic out-of-plane forces indicated movements towards a saddle shaped annulus, and the transducer was able to measure independent directional forces in individual annular segments. Further measurements with the new transducer coupled with clinical annuloplasty rings will provide a detailed insight into the biomechanical dynamics of these devices.
authors.affiliation: Department of Cardiothoracic and Vascular Surgery and Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark; Department of Engineering, Faculty of Science and Technology, Aarhus University, Aarhus, Denmark.
authors.forename: Søren Nielsen
authors.initials: SN
authors.lastname: Skov
authors.affiliation: Department of Cardiothoracic and Vascular Surgery and Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Diana Mathilde
authors.initials: DM
authors.lastname: Røpcke
authors.affiliation: Department of Cardiothoracic and Vascular Surgery and Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Christine
authors.initials: C
authors.lastname: Ilkjær
authors.affiliation: Department of Cardiothoracic and Vascular Surgery and Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Jonas
authors.initials: J
authors.lastname: Rasmussen
authors.affiliation: Department of Cardiothoracic and Vascular Surgery and Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Marcell Juan
authors.initials: MJ
authors.lastname: Tjørnild
authors.affiliation: Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA.
authors.forename: Jorge H
authors.initials: JH
authors.lastname: Jimenez
authors.affiliation: Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA.
authors.forename: Ajit P
authors.initials: AP
authors.lastname: Yoganathan
authors.affiliation: Department of Cardiothoracic and Vascular Surgery and Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Hans
authors.initials: H
authors.lastname: Nygaard
authors.affiliation: Department of Cardiothoracic and Vascular Surgery and Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Sten Lyager
authors.initials: SL
authors.lastname: Nielsen
authors.affiliation: Department of Cardiothoracic and Vascular Surgery and Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark; Department of Biomedical Engineering, University of Arkansas, Fayetteville, AR, USA. Electronic address: dr.morten.jensen@gmail.com.
authors.forename: Morten Olgaard
authors.initials: MO
authors.lastname: Jensen
mesh_terms: D000818:Animals; D008943:Mitral Valve / Q000601:surgery; D058386:Mitral Valve Annuloplasty; D013314:Stress, Mechanical; D013552:Swine; D013599:Systole; D014159:Transducers
keywords: Biomechanics; Force transducer; Mitral valve; Mitral valve annuloplasty; Strain gauge