Abstract
Transcatheter mitral valve (TMV) replacement technology has great clinical potential for surgically inoperable patients suffering from mitral regurgitation. An important goal for robust TMV design is maximizing the likelihood of achieving a geometry post-implant that facilitates optimal performance. To support this goal, improved understanding of the annular forces that oppose TMV radial expansion is necessary. In Part II of this study, novel circular and D-shaped Radial Expansion Force Transducers (C-REFT and D-REFT) were developed and employed in porcine hearts (N = 12), to detect the forces required to radially expand the mitral annulus to discrete oversizing levels. Forces on both the septal-lateral and inter-commissural axes (FSL and FIC) scaled with device size. The D-REFT experienced lower FSL than the C-REFT (19.8 ± 7.4 vs. 17.4 ± 10.8 N, p = 0.002) and greater FIC (31.5 ± 14.0 vs. 36.9 ± 16.2 N; p = 0.002), and was more sensitive to degree of oversizing. Across all tests, FIC/FSL was 2.21 ± 1.33, likely reflecting low resistance to radial expansion at the aorto-mitral curtain. In conclusion, the annular forces opposing TMV radial expansion are non-uniform, and depend on final TMV shape and size. Based on this two-part study, we propose that radial force applied at the commissural aspect of the annulus has the most potent effect on paravalvular sealing.
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Abbreviations
- C:
-
Circular
- D:
-
D-shaped
- IC:
-
Inter-commissural
- LV:
-
Left ventricle
- µCT:
-
Micro-computed tomography
- MV:
-
Mitral valve
- PVL:
-
Paravalvular leakage
- REFT:
-
Radial Expansion Force Transducer
- SL:
-
Septal-lateral
- TMV:
-
Transcatheter mitral valve
- TMVR:
-
Transcatheter mitral valve replacement
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Acknowledgments
This study was supported by a grant from the National Science Foundation (DGE-1148903; ELP), and by the National Heart, Lung, and Blood Institute (R01HL113216). The authors thank Dr. Joseph Gorman for his contributions to study design, 3D Printing Tech, Atlanta, GA, for their 3D printing/manufacturing expertise, and Holifield Farms, Covington, GA, for donating porcine hearts.
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Associate Editor Jane Grande-Allen oversaw the review of this article.
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Pierce, E.L., Kohli, K., Ncho, B. et al. Novel In Vitro Test Systems and Insights for Transcatheter Mitral Valve Design, Part II: Radial Expansion Forces. Ann Biomed Eng 47, 392–402 (2019). https://doi.org/10.1007/s10439-018-02139-3
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DOI: https://doi.org/10.1007/s10439-018-02139-3