1. How Local Annular Force and Collagen Density Govern Mitral Annuloplasty Ring Dehiscence Risk 
Eric L. Pierce, BS, Andrew W. Siefert, PhD, Deborah M. Paul, BS, Sarah K. Wells, BS, Charles H. Bloodworth, BS, Satoshi Takebayashi, MD, Chikashi Aoki, MD, Morten O. Jensen, PhD, Dr.Med, Matthew J. Gillespie, MD, Robert C. Gorman, MD, Joseph H. Gorman, MD, Ajit P. Yoganathan, PhD 
The Annals of Thoracic Surgery 
Volume 102, Issue 2, Pages (August 2016)
DOI: /j.athoracsur
Copyright © 2016 The Society of Thoracic Surgeons Terms and Conditions

2. Fig 1
Design and implementation of custom suture force transducers, first reported by Siefert and colleagues [17]. (A) Schematic representation of transducer, highlighting (a) suture holes for ring mounting, (b) annuloplasty mattress suture passages, (c) strain gauge for force measurement, and (d) wiring. (B) Each instrumented ring contains four anterior (orange) and six posterior (purple) transducers. (C) Device implantation. (D) Device (arrow) imaged by fluoroscopy after implantation.
The Annals of Thoracic Surgery  , DOI: ( /j.athoracsur )
Copyright © 2016 The Society of Thoracic Surgeons Terms and Conditions

3. Fig 2
Ex vivo suture holding strength testing. (A and B) Mitral valve before and after explantation from ovine heart. (C) Tie-down to custom fixture with the use of two continuous suture loops. Test sutures harnessed until pullout trial (red arrows). (D) Each suture was pulled out independently, at a perpendicular angle to the test plate. (LT = left trigone; RT = right trigone.)
The Annals of Thoracic Surgery  , DOI: ( /j.athoracsur )
Copyright © 2016 The Society of Thoracic Surgeons Terms and Conditions

4. Fig 3
Representative coupled in vivo recordings of annuloplasty suture forces and left ventricular pressure (LVP). Each trace corresponds to one mattress suture. The primary contributors to the observed increases in suture tension during systole are (1) constraint of the native annular shape to that of a flat, undersized ring; (2) radial expansion of contracting myocardial fibers; and (3) pressure acting on the valve leaflets, which may further pull the annulus and sutures [22]. Note, baseline pretension (ie, the minimum force in each trace) has been zeroed, to highlight the amplitude differences among the ten sutures. This baseline force is non-zero and positive and is a subject of ongoing investigation. (N = Newton.)
The Annals of Thoracic Surgery  , DOI: ( /j.athoracsur )
Copyright © 2016 The Society of Thoracic Surgeons Terms and Conditions

5. Fig 4
Cyclic forces (FCs) on each suture, recorded in vivo after cardiopulmonary bypass (mean ± SE). FC was computed from ten consecutive cycles with peak left ventricular pressure (LVPmax) of 100, 125, or 150 mm Hg. Anterior FC (orange) exceeded posterior FC (purple) by an average of 1.0 to 1.1 N, depending on LVPmax (p < 0.01 at each LVPmax). (Ant = anterior; LT = left trigone; N = Newton; Post = posterior; RT = right trigone.)
The Annals of Thoracic Surgery  , DOI: ( /j.athoracsur )
Copyright © 2016 The Society of Thoracic Surgeons Terms and Conditions

6. Fig 5
Analysis of variance plots, reporting 95% confidence intervals for the influence of each suture position on (A–C) cyclic forces or (D) holding strength. Positive or negative contribution to suture force at a given position indicates that position experienced force that was either greater or less than the grand mean force, respectively. Position pairs whose whiskers do not overlap are significantly different (p < 0.05). (LT = left trigone; N = Newton; RT = right trigone.)
The Annals of Thoracic Surgery  , DOI: ( /j.athoracsur )
Copyright © 2016 The Society of Thoracic Surgeons Terms and Conditions

7. Fig 6
A) Suture holding strength (HS) at each position, determined by ex vivo suture pullout testing. All Ant (anterior; orange) HSs exceeded all Post (posterior; purple) HSs, including an average differential of 2.5 N (p < ). (B) Residual strength (RS) at each position, that is, the difference between mean HS and mean cyclic force with peak left ventricular pressure of 150 mm Hg (Fig 3). Ant RS exceeded Post RS by 1.4 N on average (p = 0.10). (LT = left trigone; N = Newton; RT = right trigone.)
The Annals of Thoracic Surgery  , DOI: ( /j.athoracsur )
Copyright © 2016 The Society of Thoracic Surgeons Terms and Conditions

8. Fig 7
A) Normalized mean pixel intensity (nMPI), averaged over five mitral valves (MVs). (B) Collagen density at a given suture position, indicated by nMPI, correlated to residual strength at that position. (C) Representative MV annulus section at site of suture passage, visualized by autofluorescence; nonspecific fibers (red) versus collagen (green). Endocardial surface along right edge; leaflet hinge at lower-right corner. *p < 0.05; †p <  (Ant = central anterior; LT = left trigone; Post = central posterior; RT = right trigone.)
The Annals of Thoracic Surgery  , DOI: ( /j.athoracsur )
Copyright © 2016 The Society of Thoracic Surgeons Terms and Conditions