2017 Cardiovascular Research Day Abstract Book

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Multilevel Mechanical Testing of Cardiac Valves
Arielle Waller 1 • Daniel Perry 1 • Luke Knudson 1 • RS Baker 2 • David Morales, MD 3 •
Farhan Zafar, MD 2 • Daria Narmoneva, PhD 1
1Biomedical Engineering, University of Cincinnati • 2 Division of Pediatric Cardiothoracic Surgery,
The Heart Institute, Cincinnati Children's Hospital • 3 Division of Pediatric Cardiothoracic Surgery,
The Heart Institute, Cincinnati Children's Hospital
Graduate Student
The lack of adequate heart valve replacement options represents a major problem in pediatric care,
where multiple operations are required to accommodate patient growth. Bioengineered valves may
provide a viable alternative to existing strategies. Knowledge of the relationship between macroand
micro-biomechanical properties and functional behavior of native or engineered valve tissue is
critical for success of bioengineered valves, yet it is still poorly understood. Here, a tubular
tricuspid valve bioprosthesis made of small intestinal submucosa-derived extracellular matrix (SIS-
ECM) was used as a valve replacement in the in vivo sheep model. Current study developed distinct
multilevel testing approaches to determine valve tissue biomechanical properties and quantify the
structure-function and behaviors. The following analyses were performed: (i) tissue/organ level
uniaxial testing of valve samples; (ii) microanalyses (cellular/subcellular level) of adjacent fullthickness
valve sections using atomic force microscopy (AFM) to determine valve mechanical
properties. The AFM approach was used in combination with MATLAB-based quantitative 2D
histological mapping of valve matrix content (collagen & proteoglycans), for functional analyses of
biomechanical behavior. Results demonstrated that valve tensile elastic modulus was higher for the
valve annulus vs. the cusp, consistent with proteoglycan rich regions on the distal end of the cusp,
and a collagen rich region on the proximal end of the cusp and fibrosa. Compression stiffness from
AFM testing demonstrated an increased Young’s modulus for the fibrosa vs. spongiosa, with
intermediate values for atrialis (mitral and tricuspid) and ventricularis (aortic and pulmonary),
consistent with a collagen-rich fibrosa, proteoglycan-rich spongiosa, and elastin-rich
atrialis/ventricularis. In summary, this demonstrates feasibility of this multilevel testing approach
in functional assessment of bioengineered valve and its ability to provide necessary mechanical
function immediately upon implantation, and to attain structural and biomechanical properties of
the native tissue during growth and remodeling.
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