1. University of Pittsburgh Vascular Bioengineering Laboratory Departments of Surgery and Bioengineering and the McGowan Institute for Regenerative Medicine Pittsburgh, PA Ascending aortic aneurysm biomechanical properties are variable depending on aortic valve morphology Joseph Muthu, ME,MS, Julie Philippi, PhD, Thomas Gleason, MD, David A. Vorp, PhD

2. Introduction Biomechanical models of wall strength are being developed to better predict Ascending Aortic Aneurysm (TAA) dissection or disruption as compared to diameter criterion TAA dissection/disruption represents a mechanical failure of the diseased aortic wall, and has been associated with diminished tensile strength. BAV patients are predisposed to TAA formation The correlation of variable TAA wall strength with aortic valve morphology is unknown

3. Purpose of This Study Determine whether differences in wall tensile strength exist between BAV and TAV TAAs Determine whether tensile strength depends on location and orientation of the tissue Evaluate biomechanical model differences in BAV and TAV

4. Methods Rectangular tissue specimens from TAA patients with BAV and TAV were harvested in circumferential and longitudinal orientations, and tested in uniaxial tensile test machine within 48 hrs. The specimens were preconditioned for 10 cycles of loading and unloading After preconditioning, the tissues were stretched at the rate of 8.5% of its initial gauge length until its failure The Cauchy stress and strain were derived from force displacement data and initial tissue dimensions

5. Uniaxial Tensile Testing (LONG) Ultimate Tensile Strength

6. Uniaxial Tensile Testing (CIRC) Ultimate Tensile Strength

8. P=0.0001 P=0.009 P= 0.29 P= 0.004

9. Histology: Collagen (Trichrome staining) Non-Aneurysmal Aneurysmal w/ TAV Aneurysmal w/ BAV 40X Brightfield Trichrome stain 5 µm paraffin sections Blue=collagen Red= cytoplasm

10. Diameter

11. Conclusion The average strength of aneurysmal wall in the circumferential direction was significantly higher than that of the longitudinal direction within the groups exhibiting anisotropic nature of the wall. Wall strength of BAV may be stronger than TAV in both the orientations