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Effects of Different Annuloplasty Rings on Anterior Mitral Leaflet Dimensions
John-Peder E. Kvitting1, Wolfgang Bothe1, Julia C. Swanson1, Paul A. Chang1, Sigurd Hartnett1, Neil B. Ingels, Jr.2, *D. Craig Miller1
1Stanford University, Stanford, CA;2Palo Alto Medical Foundation Research Institute, Palo Alto, CA
BACKGROUND: Mitral valve (MV) repair typically includes implantation of an annuloplasty ring (AR). Recent studies indicate that AR insertion affects mitral leaflet shape, which alters leaflet stresses and potentially limits MV repair durability. It is currently unknown, however, how modifications in mitral annulus (MA) shape relate to leaflet dimensions. We therefore assessed the relationship between MA and anterior mitral leaflet (AML) dimensions under normal conditions and after implantation of two differently-shaped ARs.
METHODS: In twenty-four adult sheep radiopaque markers were placed as opposing pairs on the septal-lateral (S-L) and commissure-commissure (C-C) aspects of the MA and AML (Figure). Size 28 mm Physio (n=12) or GeoForm (n=12) rings (true-sized based on AML height) were implanted in a releasable fashion. Under acute open-chest conditions, 4-D marker coordinates were obtained using biplane videofluoroscopy (60 Hz) with the AR inserted (PHYSIO, GEO) and after AR release (PHYSIO-CTRL, GEO-CTRL). S-L and C-C dimensions were calculated from the respective marker pairs both for the MA (MAS-L and MAC-C, respectively) and the AML (AMLS-L and AMLC-C, respectively) at end-diastole (ED) and end-systole (ES). Systolic dimension changes are described as changes from ED to ES.
RESULTS: See Table. In PHYSIO-CTRL and GEO-CTRL MAS-L shortened significantly during systole, but AMLS-L did not change. In contrast, MAC-C did not change during systole whereas AMLC-C became significantly smaller. With PHYSIO: (1) MAS-L and MAC-C were smaller than PHYSIO-CTRL at ED and ES, and did not change during systole; (2) AMLC-C was smaller than control at ED and ES and decreased during systole; and, (3) AMLS-L was unchanged from control and remained constant during systole. With GEO: (1) MAS-L and MAC-C were smaller than GEO-CTRL at ED and ES, and did not change from ED to ES; (2) AMLC-C was smaller than control only at ED and decreased during systole; and, (3) AMLS-L was unchanged from control but, unlike PHYSIO, decreased during systole.
CONCLUSIONS: Under baseline conditions during systole, the MA predominantly shortens in the S-L while the AML mainly shortens in the C-C dimension demonstrating that systolic changes in MA and AML dimensions are not directly coupled. Implantation of PHYSIO and GEO reduces both MAS-L and MAC-C dimensions, but only reduces the AMLC-C dimension indicating that the AMLC-C dimension is crucial to describe the effects of an AR on mitral leaflet geometry. While AMLS-L was unchanged during systole with PHYSIO, it decreased with GEO suggesting that systolic alterations in AMLS-L dynamics result from the unphysiological shape of the GEO AR. With the increased use of real-time three-dimensional echocardiography, the assessment of leaflet dimensions and their systolic changes may play an important role in pre-operative technical planning of MV repair.
* = p<0.01 vs. ED, # = p<0.01 vs. CTRL. | PHYSIO-CTRL | PHYSIO | GEO-CTRL | GEO | | MA S-L | | ED | 3.01 ± 0.31 | 2.49 ± 0.14 # | 2.88 ± 0.20 | 1.98 ± 0.09 # | | ES | 2.88 ± 0.20 * | 2.47 ± 0.15 #, * | 2.63 ± 0.22 * | 1.98 ± 0.08 # | | MA C-C | | ED | 3.94 ± 0.24 | 3.29 ± 0.08 # | 3.77 ± 0.22 | 3.47 ± 0.13 # | | ES | 3.91 ± 0.21 | 3.30 ± 0.07 # | 3.68 ± 0.27 | 3.46 ± 0.15 # | | AML S-L | | ED | 1.75 ± 0.25 | 1.79 ± 0.22 | 1.70 ± 0.17 | 1.76 ± 0.18 | | ES | 1.69 ± 0.30 | 1.70 ± 0.26 | 1.64 ± 0.12 | 1.59 ± 0.15 * | | AML C-C | | ED | 3.32 ± 0.28 | 3.18 ± 0.26 # | 2.96 ± 0.37 | 2.90 ± 0.32 # | | ES | 3.03 ± 0.21 * | 2.98 ± 0.22 #, * | 2.82 ± 0.31 * | 2.81 ± 0.29 * |
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