Histopathological and biomechanical properties of the aortic wall in 2 patients with chronic type A aortic dissection

Type A aortic dissection is an acute condition that requires urgent surgical intervention. However, in a subset of patients, aortic dissections go undiagnosed and becomechronic, thereby allowing the dissectedwall to undergo a distinct remodeling process from that of the surrounding intact wall. Here, we observe the biomechanical and histological changes in the aortic wall of two patients with chronic Type A aortic dissection. Partial or complete disruption of the elastic structure of the medial layer was observed in the dissected wall of both patients; however, aortic stiffness in the region of dissection covaried with a change in collagen content. A similar to 50% increase in viscous energy losswas observed in the region of dissection of both patientswhich suggests an impaired elastic recoil andWindkessel function of the proximal aorta. MMP expression (2 and 9) differed between the dissected and intact wall and was distinct between the two patients. Our observations suggest that an active remodeling process occurs in the dissected aortic wall resulting in a vastly different biomechanical behavior. (C) 2017 Elsevier Inc. All rights reserved.