University of Pittsburgh Vascular Bioengineering Laboratory Departments of Surgery and...
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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
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Transcript of University of Pittsburgh Vascular Bioengineering Laboratory Departments of Surgery and...
University of PittsburghVascular 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
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
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
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
Uniaxial Tensile Testing (LONG)
Ultimate Tensile Strength
Uniaxial Tensile Testing (CIRC)
Ultimate Tensile Strength
THORACIC ANEURYSM TENSILE TESTING
0
50
100
150
200
250
300
Ult
imate
Ten
sil
e S
tren
gth
(UT
S)
N/c
m^
2
Longitudinal Circumferential
Comparison of Strength of TAA
0
20
40
60
80
100
120
140
160
180
200
Bicuspid-Avg (n=9) Tricuspid-Avg (n=5) Control- Avg (n=3)
Ult
ima
te T
en
sile
Str
en
th (
UT
S)
N/c
m^
2
Longitudinal Circumferential
P=0.0001
P=0.009
P= 0.29
P= 0.004
Histology: Collagen (Trichrome staining)
Non-Aneurysmal Aneurysmal w/ TAV Aneurysmal w/ BAV
40X BrightfieldTrichrome stain5 µm paraffin sections
Blue=collagenRed= cytoplasm
Diameter
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
