Hypertension-Induced Biomechanical Modifications in the Aortic Wall and Their Role in Stanford Type B Aortic Dissection

Objective: Hypertension is a major risk factor for the type B aortic dissection (TBAD), while many patients do not manage or regulate their hypertension consistently, leading to stable or unstable hypertension. Currently, the effects of stable and unstable hypertension on the biomechanical properties of the aorta remain unclear. The objective was to identify a blood pressure state that represents a greater risk for TBAD development. Methods: A total of 183 samples (108 axial and 75 circumferential) were divided into three groups. Fatigue tensile tests were carried out to simulate normotension, stable hypertension, and unstable hypertension conditions, respectively. Uniaxial tensile tests were performed; thus, the elastic modulus, energy loss, and the peeling force were assessed to evaluate the biomechanical properties. Results: Compared with normal blood pressure, the modulus of elastic fibers decreased under stable hypertension (0.05 ± 0.02 MPa vs. 0.11 ± 0.03 MPa, p < 0.001) and unstable hypertension (0.08 ± 0.02 MPa, p = 0.008), while collagen fibers increased under stable hypertension (2.14 ± 0.51 MPa vs. 1.10 ± 0.24 MPa, p < 0.001) but decreased under unstable hypertension (0.52 ± 0.14 MPa, p < 0.001) in the axial direction. Similar trends were observed circumferentially. Energy loss was highest under unstable hypertension (0.16 ± 0.03 vs. 0.08 ± 0.03, p < 0.001). Peeling force was significantly reduced under stable hypertension (81.69 ± 12.72 N/m vs. 111.10 ± 27.65 N/m, p < 0.001) and further under unstable hypertension (71.37 ± 16.13 N/m, p < 0.001). Conclusions: Stable and unstable hypertension significantly impair the biomechanical properties of the aortic wall, with unstable hypertension leading to greater damage. Hypertensive patients are recommended to strictly follow medical advice to control blood pressure to avoid a higher risk of TBAD due to improper blood pressure management.