Biomechanical properties of the aortic root are distinct from those of the ascending aorta in both normal and aneurysmal statesCentral MessagePerspective
Jennifer C.-Y. Chung, MD, MSc,
Daniella Eliathamby, MASc,
Hijun Seo, MASc,
Chun-Po Fan, PhD,
Rifat Islam, MD, MSc,
Karamvir Deol, RN,
Craig A. Simmons, PhD,
Maral Ouzounian, MD, PhD
Affiliations
Jennifer C.-Y. Chung, MD, MSc
Division of Cardiovascular Surgery, Peter Munk Cardiac Centre, University Health Network, Toronto General Hospital, Toronto, Ontario, Canada; Department of Surgery, University of Toronto, Toronto, Ontario, Canada; Address for reprints: Jennifer C.-Y. Chung, MD, MSc, Division of Cardiac Surgery, Toronto General Hospital, 200 Elizabeth St, 4N-466, Toronto, Ontario M5G 2C4, Canada.
Daniella Eliathamby, MASc
Institute of Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada; Translational Biology & Engineering Program, Ted Rogers Centre for Heart Research, The Hospital for Sick Children, Toronto, Ontario, Canada
Hijun Seo, MASc
Institute of Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada; Translational Biology & Engineering Program, Ted Rogers Centre for Heart Research, The Hospital for Sick Children, Toronto, Ontario, Canada
Chun-Po Fan, PhD
Rogers Computational Program, Peter Munk Cardiac Centre, University Health Network, Toronto, Ontario, Canada
Rifat Islam, MD, MSc
Division of Cardiovascular Surgery, Peter Munk Cardiac Centre, University Health Network, Toronto General Hospital, Toronto, Ontario, Canada
Karamvir Deol, RN
Division of Cardiovascular Surgery, Peter Munk Cardiac Centre, University Health Network, Toronto General Hospital, Toronto, Ontario, Canada
Craig A. Simmons, PhD
Institute of Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada; Translational Biology & Engineering Program, Ted Rogers Centre for Heart Research, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Mechanical & Industrial Engineering, University of Toronto, Toronto, Ontario, Canada
Maral Ouzounian, MD, PhD
Division of Cardiovascular Surgery, Peter Munk Cardiac Centre, University Health Network, Toronto General Hospital, Toronto, Ontario, Canada; Department of Surgery, University of Toronto, Toronto, Ontario, Canada
Background: Although aneurysms of the ascending aorta and the aortic root are treated similarly in clinical guidelines, how biomechanical properties differ between these 2 segments of aorta is poorly defined. Methods: Biomechanical testing was performed on tissue collected from the aortic root (normal = 11, aneurysm = 51) and the ascending aorta (normal = 21, aneurysm = 76). Energy loss, tangent modulus of elasticity, and delamination strength were evaluated. These biomechanical properties were then compared between (1) normal ascending and normal root tissue, (2) normal and aneurysmal root tissue, (3) normal and aneurysmal ascending tissue, and (4) aneurysmal root and aneurysmal ascending tissue. Propensity score matching was performed to further compare aneurysmal root and aneurysmal ascending aortic tissue. Clinical and biomechanical variables associated with decreased delamination strength in the aortic root were evaluated. Results: The normal aortic root demonstrated greater viscoelastic behavior (energy loss 0.08 [0.06, 0.10] vs 0.05 [0.04, 0.06], P = .008), and greater resistance against delamination (93 [58, 126] mN/mm vs 54 [40, 63] mN/mm, P = .05) compared with the ascending aorta. Delamination strength was significantly reduced in aneurysms in both the root and the ascending aorta compared with their normal states. Aneurysms of the aortic root matched to the ascending aortic aneurysms in terms of baseline characteristics including size, were characterized by a larger decrease in delamination strength from baseline (Δ −59 mN/mm vs Δ −24 mN/mm). Aging (P = .003) and the presence of hypertension (P = .02) were associated with weakening of the aortic root, while diameter did not have this association (P = .29). Conclusions: The normal aortic root was found to have distinct biomechanical properties compared with the ascending aorta. When aneurysms form in the aortic root, there is less strength against delamination, without other biomechanical changes such as increased energy loss observed in aneurysmal ascending aortas. Age and hypertension were associated decreased aortic wall strength in the aortic root, whereas diameter had no such association.
