TY - JOUR
T1 - Septal-lateral annnular cinching perturbs basal left ventricular transmural strains
AU - Nguyen, Tom C.
AU - Cheng, Allen
AU - Tibayan, Frederick A.
AU - Liang, David
AU - Daughters, George T.
AU - Ingels, Neil B.
AU - Miller, David Craig
N1 - Funding Information:
This work was supported by Grants HL-29589 and HL-67025 from the National Heart, Lung and Blood Institute. Drs Nguyen and Cheng were Leah McConnell Cardiovascular Surgical Research Fellows. Dr Nguyen was a recipient of the Thoracic Society Foundation Research Fellowship Award. We deeply appreciate the technical expertise provided by Mary K. Zasio, B.A., Maggie Brophy, A.S., and Katha Gazda, B.A. We also thank Drs Akinobu Itoh and Robert A. Oakes for their generous help and advice.
PY - 2007/3
Y1 - 2007/3
N2 - Objective: Septal-lateral annular cinching ('SLAC') corrects both acute and chronic ischemic mitral regurgitation in animal experiments, which has led to the development of therapeutic surgical and interventional strategies incorporating this concept (e.g., Edwards GeoForm ring, Myocor Coapsys®, Ample Medical PS3). Changes in left ventricular (LV) transmural cardiac and fiber-sheet strains after SLAC, however, remain unknown. Methods: Eight normal sheep hearts had two triads of transmural radiopaque bead columns inserted adjacent to (anterobasal) and remote from (midlateral equatorial) the mitral annulus. Under acute, open chest conditions, 4D bead coordinates were obtained using videofluoroscopy before and after SLAC. Transmural systolic strains were calculated from bead displacements relative to local circumferential, longitudinal, and radial cardiac axes. Transmural cardiac strains were transformed into fiber-sheet coordinates (Xf, Xs, Xn) oriented along the fiber (f), sheet (s), and sheet-normal (n) axes using fiber (α) and sheet (β) angle measurements. Results: SLAC markedly reduced (∼60%) septal-lateral annular diameter at both end-diastole (ED) (2.5 ± 0.3 to 1.0 ± 0.3 cm, p = 0.001) and end-systole (ES) (2.4 ± 0.4 to 1.0 ± 0.3 cm, p = 0.001). In the LV wall remote from the mitral annulus, transmural systolic strains did not change. In the anterobasal region adjacent to the mitral annulus, ED wall thickness increased (p = 0.01) and systolic wall thickening was less in the epicardial (0.28 ± 0.12 vs 0.20 ± 0.06, p = 0.05) and midwall (0.36 ± 0.24 vs 0.19 ± 0.11, p = 0.04) LV layers. This impaired wall thickening was due to decreased systolic sheet thickening (0.20 ± 0.8 to 0.12 ± 0.07, p = 0.01) and sheet shear (-0.15 ± 0.07 to -0.11 ± 0.04, p = 0.02) in the epicardium and sheet extension (0.21 ± 0.11 to 0.10 ± 0.04, p = 0.03) in the midwall. Transmural systolic and remodeling strains in the lateral midwall (remote from the annulus) were unaffected. Conclusions: Although SLAC is an alluring concept to correct ischemic mitral regurgitation, these data suggest that extreme SLAC adversely effects systolic wall thickening adjacent to the mitral annulus by inhibiting systolic sheet thickening, sheet shear, and sheet extension. Such alterations in LV strains could result in unanticipated deleterious remodeling and warrant further investigation.
AB - Objective: Septal-lateral annular cinching ('SLAC') corrects both acute and chronic ischemic mitral regurgitation in animal experiments, which has led to the development of therapeutic surgical and interventional strategies incorporating this concept (e.g., Edwards GeoForm ring, Myocor Coapsys®, Ample Medical PS3). Changes in left ventricular (LV) transmural cardiac and fiber-sheet strains after SLAC, however, remain unknown. Methods: Eight normal sheep hearts had two triads of transmural radiopaque bead columns inserted adjacent to (anterobasal) and remote from (midlateral equatorial) the mitral annulus. Under acute, open chest conditions, 4D bead coordinates were obtained using videofluoroscopy before and after SLAC. Transmural systolic strains were calculated from bead displacements relative to local circumferential, longitudinal, and radial cardiac axes. Transmural cardiac strains were transformed into fiber-sheet coordinates (Xf, Xs, Xn) oriented along the fiber (f), sheet (s), and sheet-normal (n) axes using fiber (α) and sheet (β) angle measurements. Results: SLAC markedly reduced (∼60%) septal-lateral annular diameter at both end-diastole (ED) (2.5 ± 0.3 to 1.0 ± 0.3 cm, p = 0.001) and end-systole (ES) (2.4 ± 0.4 to 1.0 ± 0.3 cm, p = 0.001). In the LV wall remote from the mitral annulus, transmural systolic strains did not change. In the anterobasal region adjacent to the mitral annulus, ED wall thickness increased (p = 0.01) and systolic wall thickening was less in the epicardial (0.28 ± 0.12 vs 0.20 ± 0.06, p = 0.05) and midwall (0.36 ± 0.24 vs 0.19 ± 0.11, p = 0.04) LV layers. This impaired wall thickening was due to decreased systolic sheet thickening (0.20 ± 0.8 to 0.12 ± 0.07, p = 0.01) and sheet shear (-0.15 ± 0.07 to -0.11 ± 0.04, p = 0.02) in the epicardium and sheet extension (0.21 ± 0.11 to 0.10 ± 0.04, p = 0.03) in the midwall. Transmural systolic and remodeling strains in the lateral midwall (remote from the annulus) were unaffected. Conclusions: Although SLAC is an alluring concept to correct ischemic mitral regurgitation, these data suggest that extreme SLAC adversely effects systolic wall thickening adjacent to the mitral annulus by inhibiting systolic sheet thickening, sheet shear, and sheet extension. Such alterations in LV strains could result in unanticipated deleterious remodeling and warrant further investigation.
KW - Ischemic mitral regurgitation
KW - Mitral annuloplasty
KW - Mitral regurgitation
KW - Myocardial ischemia
KW - Myocardial strain
KW - Surgery
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U2 - 10.1016/j.ejcts.2006.12.019
DO - 10.1016/j.ejcts.2006.12.019
M3 - Article
C2 - 17223567
AN - SCOPUS:33847329727
SN - 1010-7940
VL - 31
SP - 423
EP - 429
JO - European Journal of Cardio-Thoracic Surgery
JF - European Journal of Cardio-Thoracic Surgery
IS - 3
ER -