title: Mitral annular size predicts Alfieri stitch tension in mitral edge-to-edge repair.
abstract: OBJECTIVE
  Whilst increased 'Alfieri stitch' tension may reduce the durability of 'edge-to-edge' mitral repair, the factors affecting suture tension are unknown. In order to study hemodynamics and left ventricular (LV) and annular dynamics that determine suture tension, the central edge of the mitral leaflets was approximated with a miniature force transducer to measure leaflet tension (T) at the leaflet approximation point.
  
  
  METHODS
  Eight sheep were studied under open-chest conditions immediately after surgical placement of a force transducer and implantation of radiopaque markers on the left ventricle and mitral annulus (MA). Hemodynamic variables were altered by two caval occlusion steps (deltaV1 and deltaV2) and dobutamine infusion. Three-dimensional marker coordinates were obtained by simultaneous biplane videofluoroscopy to measure LV volume, MA area (MAA) and septal-lateral (SL) annular dimension throughout the cardiac cycle.
  
  
  RESULTS
  At baseline, peak Alfieri stitch tension (0.30 +/- 0.18 N) was observed 96 +/- 61 ms prior to end-diastole coincident with peak annular SL diameter (98 +/- 58 ms before end-diastole). Dobutamine infusion decreased suture tension (from 0.30 +/- 0.18 N to 0.20 +/- 0.12 N, p = 0.01), although peak systolic pressure increased significantly (138 +/- 19 versus 115 +/- 14 mmHg; p = 0.03). A regression model was fitted with the goal of interpreting the hemodynamic and geometric predictors of tension as their influence varied with time: Tt (N) = 0.1916 + 0.2115 x SL (cm) - 0.1996 x MAA/SL (cm2/cm) + ft x LVP (mmHg), where Tt is tension at any time during the cardiac cycle and ft is the time-varying coefficient of LVP.
  
  
  CONCLUSIONS
  Tension on the leaflets in the edge-to-edge repair is determined primarily by MA SL size, and paradoxically is lower when the contractile state is enhanced. This indicates that annular and/or LV dilatation increase stitch tension and may adversely affect durability of the repair if concomitant ring annuloplasty is not performed.
authors.affiliation: Department of Cardiothoracic Surgery, Stanford University School of Medicine, Stanford, CA 94305-5247, USA.
authors.forename: Tomasz A
authors.initials: TA
authors.lastname: Timek
authors.forename: Sten L
authors.initials: SL
authors.lastname: Nielsen
authors.forename: David T
authors.initials: DT
authors.lastname: Lai
authors.forename: Frederick
authors.initials: F
authors.lastname: Tibayan
authors.forename: David
authors.initials: D
authors.lastname: Liang
authors.forename: George T
authors.initials: GT
authors.lastname: Daughters
authors.forename: Philip
authors.initials: P
authors.lastname: Beineke
authors.forename: Trevor
authors.initials: T
authors.lastname: Hastie
authors.forename: Neil B
authors.initials: NB
authors.lastname: Ingels
authors.forename: D Craig
authors.initials: DC
authors.lastname: Miller
mesh_terms: D000818:Animals; D002315:Cardiopulmonary Bypass; D002316:Cardiotonic Agents / Q000008:administration & dosage; D004280:Dobutamine / Q000008:administration & dosage; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D019918:Heart Valve Prosthesis Implantation; D006352:Heart Ventricles / Q000503:physiopathology / Q000601:surgery; D008297:Male; D008943:Mitral Valve / Q000503:physiopathology* / Q000601:surgery*; D023421:Models, Animal; D008955:Models, Cardiovascular; D011237:Predictive Value of Tests; D012756:Sheep; D013223:Statistics as Topic; D013318:Stroke Volume / Q000187:drug effects / Q000502:physiology; D013536:Suture Techniques; D013599:Systole / Q000187:drug effects / Q000502:physiology; D013997:Time Factors; D017725:Ventricular Pressure / Q000187:drug effects / Q000502:physiology
chemical_list: D002316:Cardiotonic Agents; D004280:Dobutamine