title: Importance of mitral valve second-order chordae for left ventricular geometry, wall thickening mechanics, and global systolic function.
abstract: BACKGROUND
  Mitral valvular-ventricular continuity is important for left ventricular (LV) systolic function, but the specific contributions of the anterior leaflet second-order "strut" chordae are unknown.
  
  
  RESULTS
  Eight sheep had radiopaque markers implanted to silhouette the LV, annulus, and papillary muscles (PMs); 3 transmural bead columns were inserted into the mid-lateral wall between the PMs. The strut chordae were encircled with exteriorized wire snares. Three-dimensional marker images and hemodynamic data were acquired before and after chordal cutting. Preload recruitable stroke work (PRSW) and end-systolic elastance (E(es)) were calculated to assess global LV systolic function (n=7). Transmural strains were measured from bead displacements (n=4). Chordal cutting caused global LV dysfunction: E(es) (1.48+/-1.12 versus 0.98+/-1.30 mm Hg/mL, P=0.04) and PRSW (69+/-16 versus 60+/-15 mm Hg, P=0.03) decreased. Although heart rate and time from ED to ES were unchanged, time of mid-ejection was delayed (125+/-18 versus 136+/-19 ms, P=0.01). Globally, the LV apex and posterior PM tip were displaced away from the fibrous annulus and LV base-apex length increased at end-diastole and end-systole (all +1 mm, P<0.05). Locally, subendocardial end-diastolic strains occurred: Longitudinal strain (E22) 0.030+/-0.013 and radial thickening (E33) 0.081+/-0.041 (both P<0.05 versus zero). Subendocardial systolic shear strains were also perturbed: Circumferential-longitudinal "micro-torsion" (E12) (0.099+/-0.035 versus 0.075+/-0.025) and circumferential radial shear (E13) (0.084+/-0.023 versus 0.039+/-0.008, both P<0.05).
  
  
  CONCLUSIONS
  Cutting second-order chords altered LV geometry, remodeled the myocardium between the PMs, perturbed local systolic strain patterns affecting micro-torsion and wall-thickening, and caused global systolic dysfunction, demonstrating the importance of these chordae for LV structure and function.
authors.affiliation: Department of Cardiothoracic Surgery, Stanford University School of Medicine, Stanford, Calif 94305-5247, USA.
authors.forename: Filiberto
authors.initials: F
authors.lastname: Rodriguez
authors.forename: Frank
authors.initials: F
authors.lastname: Langer
authors.forename: Katherine B
authors.initials: KB
authors.lastname: Harrington
authors.forename: Frederick A
authors.initials: FA
authors.lastname: Tibayan
authors.forename: Mary K
authors.initials: MK
authors.lastname: Zasio
authors.forename: Allen
authors.initials: A
authors.lastname: Cheng
authors.forename: David
authors.initials: D
authors.lastname: Liang
authors.forename: George T
authors.initials: GT
authors.lastname: Daughters
authors.forename: James W
authors.initials: JW
authors.lastname: Covell
authors.forename: John C
authors.initials: JC
authors.lastname: Criscione
authors.forename: Neil B
authors.initials: NB
authors.lastname: Ingels
authors.forename: D Craig
authors.initials: DC
authors.lastname: Miller
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002815:Chordae Tendineae / Q000502:physiology* / Q000601:surgery; D006339:Heart Rate; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000648:ultrastructure*; D006439:Hemodynamics; D021621:Imaging, Three-Dimensional; D008943:Mitral Valve / Q000000981:diagnostic imaging / Q000648:ultrastructure*; D011859:Radiography; D012756:Sheep; D013314:Stress, Mechanical; D013599:Systole / Q000502:physiology*; D014102:Torsion Abnormality; D018487:Ventricular Dysfunction, Left / Q000209:etiology / Q000503:physiopathology; D016277:Ventricular Function, Left / Q000502:physiology*