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Novel In Vitro Test Systems and Insights for Transcatheter Mitral Valve Design, Part II: Radial Expansion Forces

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 (F_SL and F_IC) scaled with device size. The D-REFT experienced lower F_SL than the C-REFT (19.8 ± 7.4 vs. 17.4 ± 10.8 N, p = 0.002) and greater F_IC (31.5 ± 14.0 vs. 36.9 ± 16.2 N; p = 0.002), and was more sensitive to degree of oversizing. Across all tests, F_IC/F_SL 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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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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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.

1. Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, 387 Technology Circle NW, Suite 200, Atlanta, GA, 30313, USA

   Eric L. Pierce, Keshav Kohli, Beatrice Ncho, Vahid Sadri, Charles H. Bloodworth, Fiona E. Mangan & Ajit P. Yoganathan

1. Eric L. Pierce
2. Keshav Kohli
3. Beatrice Ncho
4. Vahid Sadri
5. Charles H. Bloodworth
6. Fiona E. Mangan
7. Ajit P. Yoganathan

Correspondence to Ajit P. Yoganathan.

Associate Editor Jane Grande-Allen oversaw the review of this article.

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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• Received: 10 May 2018

• Accepted: 22 September 2018

• Published: 17 October 2018

• Issue Date: 15 February 2019

• DOI: https://doi.org/10.1007/s10439-018-02139-3

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