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Research Papers

In Vitro Evaluation of a Novel Hemodynamically Optimized Trileaflet Polymeric Prosthetic Heart Valve

[+] Author and Article Information
Jawaad Sheriff

Department of Biomedical Engineering,
Stony Brook University,
Stony Brook, NY 11794

Ulrich Steinseifer

Helmholtz Institute of Applied Medical Engineering,
Aachen, D-52074 Germany

Marvin J. Slepian

Department of Medicine and Biomedical Engineering,
Sarver Heart Center,
University of Arizona,
Tucson, AZ 85724

Danny Bluestein

Department of Biomedical Engineering,
Stony Brook University,
Stony Brook, NY 11794
e-mail: danny.bluestein@sunysb.edu

1Corresponding author.

Contributed by the Bioengineering Division of ASME for publication in the Journal of Biomechanical Engineering. Manuscript received October 9, 2012; final manuscript received December 3, 2012; accepted manuscript posted December 22, 2012; published online February 7, 2013. Editor: Victor H. Barocas.

J Biomech Eng 135(2), 021021 (Feb 07, 2013) (8 pages) Paper No: BIO-12-1474; doi: 10.1115/1.4023235 History: Received October 09, 2012; Revised December 03, 2012

Calcific aortic valve disease is the most common and life threatening form of valvular heart disease, characterized by stenosis and regurgitation, which is currently treated at the symptomatic end-stages via open-heart surgical replacement of the diseased valve with, typically, either a xenograft tissue valve or a pyrolytic carbon mechanical heart valve. These options offer the clinician a choice between structural valve deterioration and chronic anticoagulant therapy, respectively, effectively replacing one disease with another. Polymeric prosthetic heart valves (PHV) offer the promise of reducing or eliminating these complications, and they may be better suited for the new transcatheter aortic valve replacement (TAVR) procedure, which currently utilizes tissue valves. New evidence indicates that the latter may incur damage during implantation. Polymer PHVs may also be incorporated into pulsatile circulatory support devices such as total artificial heart and ventricular assist devices that currently employ mechanical PHVs. Development of polymer PHVs, however, has been slow due to the lack of sufficiently durable and biocompatible polymers. We have designed a new trileaflet polymer PHV for surgical implantation employing a novel polymer—xSIBS—that offers superior bio-stability and durability. The design of this polymer PHV was optimized for reduced stresses, improved hemodynamic performance, and reduced thrombogenicity using our device thrombogenicity emulation (DTE) methodology, the results of which have been published separately. Here we present our new design, prototype fabrication methods, hydrodynamics performance testing, and platelet activation measurements performed in the optimized valve prototype and compare it to the performance of a gold standard tissue valve. The hydrodynamic performance of the two valves was comparable in all measures, with a certain advantage to our valve during regurgitation. There was no significant difference between the platelet activation rates of our polymer valve and the tissue valve, indicating that similar to the latter, its recipients may not require anticoagulation. This work proves the feasibility of our optimized polymer PHV design and brings polymeric valves closer to clinical viability.

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References

Figures

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Fig. 4

(a) The optimized valve compression mold, and (b) the molded xSIBS valve prototype

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Fig. 3

Structural FEA comparing the (a) Carpentier-Edwards Perimount Magna bioprosthesis, (b) the original Innovia composite polymer valve, and (c) the optimized xSIBS valve. The stress scales in each image are identical. Reduced stress concentrations are clearly evident in the optimized valve as compared to the composite and tissue valves.

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Fig. 2

Structural FEA comparing the (a) original Innovia SIBS-Dacron composite valve with corresponding material constants to (b) the same valve with the xSIBS material constants and to (c) a simulation in which the Innovia valve stent was fitted with our new tapered thickness leaflets modeled with the xSIBS material constants. The stress scales are identical in each frame. Reduced stress concentrations are clearly evident as we altered the valve design, first changing the material to xSIBS, then changing the valve leaflets to a tapered thickness profile.

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Fig. 1

(a) The original Innovia composite polymer valve geometry, (b) the original Innovia composite polymer valve leaflet geometry featuring a curved profile and uniform thickness, (c) the new optimized polymer valve leaflet geometry featuring a flat profile and variable thickness along the radial cross-section, and (d) the optimized polymer valve geometry

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Fig. 5

The hydrodynamics results from the LHS tests comparing the optimized xSIBS valve to the Carpentier-Edwards Perimount Magna bioprosthesis. (a) The transvalvular energy loss shows favorable results for the xSIBS valve at resting conditions (CO 4–6 l/min), (b) the transvalvular pressure gradient of the xSIBS valve tracks that of the tissue valve, (c) the xSIBS regurgitation is much lower than the tissue valve, and (d) the xSIBS valve Effective Orifice Area (EOA) tracks that of the tissue valve.

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Fig. 6

The bulk flow induced platelet activation measurements with the valves mounted in the pulsatile LVAD. There is no significant difference between the platelet activation rates (PAR) of the xSIBS and tissue valve. Both are significantly different (p < 0.05) from the control (LVAD operated with no valves).

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