TY - JOUR
T1 - Importance of mitral valve second-order chordae for left ventricular geometry, wall thickening mechanics, and global systolic function
AU - Rodriguez, Filiberto
AU - Langer, Frank
AU - Harrington, Katherine B.
AU - Tibayan, Frederick A.
AU - Zasio, Mary K.
AU - Cheng, Allen
AU - Liang, David
AU - Daughters, George T.
AU - Covell, James W.
AU - Criscione, John C.
AU - Ingels, Neil B.
AU - Miller, D. Craig
PY - 2004/9/14
Y1 - 2004/9/14
N2 - 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. Methods and 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 (Ees) 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=001). 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 (E12) 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). Conclusion-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.
AB - 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. Methods and 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 (Ees) 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=001). 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 (E12) 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). Conclusion-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.
KW - Contractility
KW - Mechanics
KW - Mitral valve
KW - Regurgitation
KW - Structure
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U2 - 10.1161/01.CIR.0000138580.57971.b4
DO - 10.1161/01.CIR.0000138580.57971.b4
M3 - Article
C2 - 15364849
AN - SCOPUS:4644330324
SN - 0009-7322
VL - 110
SP - II115-II122
JO - Circulation
JF - Circulation
IS - 11 SUPPL.
ER -