Poster

Rigid restriction: the aortic wall dilemma

Philip Friedrich¹, Josephina Haunschild², Sabrina Friebe^3,4, Frank Sauer¹, Jörg Schnauß^1,5,6,7, Jürgen Lippoldt¹, Jannis Korn¹, Thomas Fuhs¹, Pablo Gottheil¹, Kolya Lettl¹, Kevin Körner¹, Dimitrij Tschodu¹, Cary Tutmarc¹, Hannah Marie Eichholz^1,8,9, Xiaofan Xie¹, Paul Mollenkopf^1,10, Denny Böttcher¹¹, Stefan G. Mayr^3,4, Christian D. Etz², Josef A. Käs¹

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Patients with a bicuspid aortic valve (BAV) are predisposed to a higher risk of developing ascending thoracic aortic aneurysms (ATAAs), which can progress to life-threatening complications such as aortic dissection and rupture. Despite the clinical significance of these outcomes, the underlying biomechanical phenotype responsible for this increased risk remains poorly understood. In our study, we employed a novel multiscale approach in time and length, to conduct a detailed mechanical analysis of tissue samples from patients. We used various techniques, including tensile testing, shear rheology, atomic force microscopy, and tabletop magnetic resonance elastography to assess the mechanical properties of the aortic wall. In addition, we studied the architectural differences in a comprehensive histological analysis.

When comparing BAV ATAA samples to those from patients with a normal tricuspid aortic valve, we observed a distinctive, dense, and highly aligned collagen fiber structure in the tunica media layer of the aorta in BAV patients. This specific fiber organization leads to increased mechanical resistance across all scales, from microscopic to macroscopic levels. Paradoxically, while this structural alignment gives the aortic wall an appearance of mechanical stability, it actually compromises the overall function of the aortic wall, contributing to the development of aortopathy. Our findings suggest that mechanical resistance may serve as a useful predictor for ATAA rupture risk. It questions the diagnostic power of the aortic diameter, which is currently used as the gold standard in clinical diagnosis and highlights the potential of magnetic resonance elastography as a non-invasive tool for clinical risk assessment and monitoring of ATAA progression.