The association between venous structural alterations and biomechanical weakness in patients with abdominal aortic aneurysms

Objective: Abdominal aortic aneurysms (AAAs) are associated with generalized arterial dilation, torturosity, and altered matrix composition, which suggests a generalized systemic weakness throughout the entire vasculature. The aim of this study was to determine whether this phenomenon was present in the venous tissue of patients with AAA. Methods. A segment of inferior mesenteric vein was harvested from patients who underwent aneurysm repair (n=11) or colectomy for diverticulosis (n=11; control). Matrix composition of the vessel was determined with stereology, and dimensions were measured with a computerized image analysis system. Stress-strain measurements were calculated with elongation of inferior mesenteric vein tissue with a tensile-testing machine. Results. Histologic examination results showed fragmentation of elastin fibers within the medial layer of venous tissue obtained from patients with AAA. The medial elastin content in tissue from patients with aneurysms was 19.4%, compared with 26.8% in the control group (P=.018). Mechanical test results revealed a significant reduction in the tensile strength from 2.885 MPa in the control group to 1.405 MPa in the AAA group (P=.007). This reduction corresponded with a significant reduction of 59% in the stiffness of the vessel, with the mean Young's modulus of elasticity in the AAA group being 2.72 MPa, compared with 5.361 MPa in the control group (P=.0005). Conclusion: Reduction in tensile strength and stiffness in venous tissue from patients with AAA was associated with disruption and reduction of the elastin content of the vein wall. These changes are analogous to those observed in the arterial aneurysmal wall and confirm the systemic nature of this disorder.