title: Quantification of Coupled Stiffness and Fiber Orientation Remodeling in Hypertensive Rat Right-Ventricular Myocardium Using 3D Ultrasound Speckle Tracking with Biaxial Testing.
abstract: Mechanical and structural changes of right ventricular (RV) in response to pulmonary hypertension (PH) are inadequately understood. While current standard biaxial testing provides information on the mechanical behavior of RV tissues using surface markers, it is unable to fully assess structural and mechanical properties across the full tissue thickness. In this study, the mechanical and structural properties of normotensive and pulmonary hypertension right ventricular (PHRV) myocardium through its full thickness were examined using mechanical testing combined with 3D ultrasound speckle tracking (3D-UST). RV pressure overload was induced in Sprague-Dawley rats by pulmonary artery (PA) banding. The second Piola-Kirchhoff stress tensors and Green-Lagrangian strain tensors were computed in the RV myocardium using the biaxial testing combined with 3D-UST. A previously established non-linear curve-fitting algorithm was applied to fit experimental data to a Strain Energy Function (SEF) for computation of myofiber orientation. The fiber orientations obtained by the biaxial testing with 3D-UST compared well with the fiber orientations computed from the histology. In addition, the re-orientation of myofiber in the right ventricular free wall (RVFW) along longitudinal direction (apex-to-outflow-tract direction) was noticeable in response to PH. For normotensive RVFW samples, the average fiber orientation angles obtained by 3D-UST with biaxial test spiraled from 20° at the endo-cardium to -42° at the epi-cardium (Δ = 62°). For PHRV samples, the average fiber orientation angles obtained by 3D-UST with biaxial test had much less spiral across tissue thickness: 3° at endo-cardium to -7° at epi-cardium (Δ = 10°, P<0.005 compared to normotensive).
authors: Center for Ultrasound Molecular Imaging and Therapeutics, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.
authors: Dae Woo
authors: DW
authors: Park
authors: Heart and Vascular Institute, University of Pittsburgh Medical Center (UPMC), Pittsburgh, Pennsylvania, United States of America.
authors: Andrea
authors: A
authors: Sebastiani
authors: Department of Biomedical Engineering, National University of Singapore, Singapore.
authors: Choon Hwai
authors: CH
authors: Yap
authors: Heart and Vascular Institute, University of Pittsburgh Medical Center (UPMC), Pittsburgh, Pennsylvania, United States of America.|Department of Bioengineering, University of Pittsburgh School of Engineering, Pittsburgh, Pennsylvania, United States of America.|McGowan Institute for Regenerative Medicine, University of Pittsburgh and UPMC, Pittsburgh, Pennsylvania, United States of America.|Heart, Lung, and Blood Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
authors: Marc A
authors: MA
authors: Simon
authors: Center for Ultrasound Molecular Imaging and Therapeutics, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.|Heart and Vascular Institute, University of Pittsburgh Medical Center (UPMC), Pittsburgh, Pennsylvania, United States of America.|Department of Bioengineering, University of Pittsburgh School of Engineering, Pittsburgh, Pennsylvania, United States of America.|McGowan Institute for Regenerative Medicine, University of Pittsburgh and UPMC, Pittsburgh, Pennsylvania, United States of America.|Heart, Lung, and Blood Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
authors: Kang
authors: K
authors: Kim
mesh_terms: D000465:Algorithms; D000818:Animals; D001696:Biomechanical Phenomena; D006352:Heart Ventricles / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006976:Hypertension, Pulmonary / Q000473:pathology* / Q000662:veterinary; D008297:Male; D009206:Myocardium / Q000473:pathology*; D011651:Pulmonary Artery / Q000601:surgery; D051381:Rats; D017207:Rats, Sprague-Dawley; D013314:Stress, Mechanical; D014463:Ultrasonography; D020257:Ventricular Remodeling