Recent Advances in Biomechanical Characterization of Thoracic Aortic Aneurysms

Abstract

Thoracic aortic aneurysm (TAA) is a focal enlargement of the thoracic aorta, but the etiology of this disease is not fully understood. Previous work suggests that various genetic syndromes, congenital defects such as bicuspid aortic valve, hypertension, and age are associated with TAA formation. Though occurrence of TAAs is rare, they can be life-threatening when dissection or rupture occurs. Prevention of these adverse events often requires surgical intervention through full aortic root replacement or implantation of endovascular stent grafts. Currently, aneurysm diameters and expansion rates are used to determine if intervention is warranted. Unfortunately, this approach oversimplifies the complex aortopathy. Improving treatment of TAAs will likely require an increased understanding of the biological and biomechanical factors contributing to the disease. Past studies have substantially contributed to our knowledge of TAAs using various ex vivo, in vivo, and computational methods to biomechanically characterize the thoracic aorta. However, any singular approach typically focuses on only material properties of the aortic wall, intra-aneurysmal hemodynamics, or in vivo vessel dynamics, neglecting combinatorial factors that influence aneurysm development and progression. In this review, we briefly summarize the current understanding of TAA causes, treatment, and progression, before discussing recent advances in biomechanical studies of TAAs and possible future directions. We identify the need for comprehensive approaches that combine multiple characterization methods to study the mechanisms contributing to focal weakening and rupture. We hope this summary and analysis will inspire future studies leading to improved prediction of thoracic aneurysm progression and rupture, improving patient diagnoses and outcomes.

Keywords: aneurysm; aorta; biomechanical; computational; imaging; modeling; thoracic.

Figure 1

(A) Bellini et al. conducted ex vivo mechanical testing on ten mouse models to elucidate the biomechanical differences between models (1). (B) Witzenburg et al. used ex vivo testing to measure the effects of shear in the aortic wall and modeled the wall components (70).

Figure 2

(A) Pasta et al. used gated CT to investigate 3D strain in TAAs (102). (B) Rahman et al. compared peak blood flow velocities between enlarged ascending thoracic aortas (TAV vs BAV) and a control (103). (C) Emerel et al. estimated wall stresses in dissected TAAs and compared results normal thoracic aortas (104).