title: A Novel Approach to Assess the In Situ Versus Ex Vivo Mechanical Behaviors of the Coronary Artery.
abstract: Ex vivo mechanical testing has provided tremendous insight toward prediction of the in vivo mechanical behavior and local mechanical environment of the arterial wall; however, the role of perivascular support on the local mechanical behavior of arteries is not well understood. Here, we present a novel approach for quantifying the impact of the perivascular support on arterial mechanics using intravascular ultrasound (IVUS) on cadaveric porcine hearts. We performed pressure-diameter tests (n = 5) on the left anterior descending coronary arteries (LADCAs) in situ while embedded in their native perivascular environment using IVUS imaging and after removal of the perivascular support of the artery. We then performed standard cylindrical biaxial testing on these vessels ex vivo and compared the results. Removal of the perivascular support resulted in an upward shift of the pressure-diameter curve. Ex vivo testing, however, showed significantly lower circumferential compliance compared to the in situ configuration. On a second set of arteries, local axial stretch ratios were quantified (n = 5) along the length of the arteries. The average in situ axial stretch ratio was 1.28 ± 0.16; however, local axial stretch ratios showed significant variability, ranging from 1.01 to 1.70. Taken together, the data suggest that both the perivascular loading and the axial tethering have an important role in arterial mechanics. Combining nondestructive testing using IVUS with traditional ex vivo cylindrical biaxial testing yields a more comprehensive assessment of the mechanical behavior of arteries.
authors.affiliation: George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332.
authors.forename: Ruoya
authors.initials: R
authors.lastname: Wang
authors.affiliation: Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332.
authors.forename: Julia
authors.initials: J
authors.lastname: Raykin
authors.affiliation: Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Woodruff Memorial Research Building, 101 Woodruff Circle, Suite 5105, Atlanta, GA 30332;Department of Surgery, Emory University School of Medicine, Atlanta, GA 30307; Surgical and Research Services, Atlanta VA Medical Center, Atlanta, GA 30033 e-mail: lbrewst@emory.edu.
authors.forename: Luke P
authors.initials: LP
authors.lastname: Brewster
authors.affiliation: George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332;Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332;Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, 315 Ferst Drive, IBB 2305, Atlanta, GA 30332 e-mail: rudy.gleason@me.gatech.edu.
authors.forename: Rudolph L
authors.initials: RL
authors.lastname: Gleason
mesh_terms: D000818:Animals; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D003198:Computer Simulation; D003331:Coronary Vessels / Q000033:anatomy & histology / Q000000981:diagnostic imaging* / Q000502:physiology*; D055119:Elastic Modulus / Q000502:physiology; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008422:Materials Testing / Q000295:instrumentation / Q000379:methods*; D008955:Models, Cardiovascular; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013552:Swine; D013718:Tensile Strength / Q000502:physiology; D018084:Ultrasonography, Interventional / Q000379:methods*; D014655:Vascular Resistance / Q000502:physiology