Effect of cutting second-order chordae on in-vivo anterior mitral leaflet compound curvature.
OBJECTIVE
Leaflet curvature determines leaflet stress. In order to assess the influence of second-order chordae (2 degrees CT) on anterior mitral valve leaflet (AMVL) geometry, AMVL curvature was measured before (Baseline) and after (CUT) cutting the 2 degrees CT.


METHODS
Miniature radiopaque markers were sutured onto the AMVL in eight sheep: four along the central-meridian from mid-septal annulus to the free-margin; and one each at the 2 degrees CT insertion. Biplane videofluoroscopic data were acquired (open-chest) before and after CUT. Marker-triplet 3-D coordinates were used to calculate radii-of-curvature at LVPmax along the central-meridian (ROCm) and across the AMVL belly (commissure-commissure axis, ROCc-c).


RESULTS
CUT did not change LVPmax (111 +/- 12 versus 106 +/- 11 mmHg; p = 0.19). At baseline, the AMVL central-meridian had compound curvature: Convex to the left ventricle near the annulus (-ROCm) and concave near the free-margin (+ROCm). After CUT, the AMVL flattened: ROCm increased near the annulus (from -1.37 +/- 0.52 to -12.58 +/- 29.04 cm; p = 0.02), but did not change near the edge. In the commissure-commissure axis, ROCc-c was concave to the left ventricle at baseline and increased after CUT in all eight animals. In five sheep, ROCc-c was increased (from 1.93 +/- 1.01 to 2.80 +/- 1.36 cm; p = 0.03), but in three sheep ROCc-c was increased and inverted (from 3.65 +/- 2.17 to -1.72 +/- 0.53 cm; p = 0.03), becoming convex to the left ventricle.


CONCLUSIONS
Compound curvature along the AMVL central-meridian appears to be an intrinsic leaflet property that persists even without support from second-order chordae, whereas concave curvature in the commissure-commissure axis is more dependent on intact second-order chordae. Leaflet compound curvature must be incorporated into future finite element models to characterize leaflet stresses accurately. The importance of second-order chordae in maintaining leaflet shape must be considered during mitral repair. A larger ROC increases leaflet stresses, while reversal of ROC changes tensile stress to compressive stress; this might trigger deleterious leaflet remodeling after chordal cutting.
Rodriguez
Filiberto
F
Department of Cardiothoracic Surgery, Falk Cardiovascular Research Center, Stanford University School of Medicine, Stanford, California 94305-5247, USA.
Langer
Frank
F
Harrington
Katherine B
KB
Tibayan
Frederick A
FA
Zasio
Mary K
MK
Liang
David
D
Daughters
George T
GT
Ingels
Neil B
NB
Miller
D Craig
DC
D000818:Animals; D002815:Chordae Tendineae / Q000473:pathology / Q000601:surgery*; D004195:Disease Models, Animal; D006350:Heart Valve Prosthesis; D019918:Heart Valve Prosthesis Implantation / Q000295:instrumentation / Q000379:methods*; D006352:Heart Ventricles / Q000473:pathology / Q000601:surgery; D008943:Mitral Valve / Q000473:pathology / Q000601:surgery*; D008944:Mitral Valve Insufficiency / Q000473:pathology / Q000601:surgery*; D008955:Models, Cardiovascular; D012720:Severity of Illness Index; D012756:Sheep; D013314:Stress, Mechanical