Geometry and flow in ascending aortic aneurysms are influenced by left ventricular outflow tract orientation: Detecting increased wall shear stress on the outer curve of proximal aortic aneurysms

Background: The geometrical characterization of ascending thoracic aortic aneu-rysms in clinical practice is limited to diameter measurements. Despite growing in-terest in hemodynamic assessment, its relationship with ascending thoracic aortic aneurysm pathogenesis is poorly understood. This study examines the relationship between geometry of the ventriculo-aortic junction and blood flow patterns in ascending thoracic aortic aneurysm disease.Methods: Thirty-three patients with ascending thoracic aortic aneurysms (exclu-sions: bicuspid aortic valves, connective tissue disease) underwent 4-dimensional flow magnetic resonance imaging. After image segmentation, geometrical parame-ters were measured, including aortic curvature, tortuosity, length, and diameter. A unique angular measurement made by the trajectory of the left ventricular outflow tract axis and the proximal aorta was also conducted. Velocity profiles were quan-titatively and qualitatively analyzed. In addition, 11 patients (33%) underwent wall shear stress mapping of the ascending thoracic aortic aneurysm region using computational fluid dynamics simulation. Results: Greater left ventricular outflow tract aortic angles were associated with larger aortic diameters at the levels of the sinus (coefficient = 0.387, P = .014) and ascending aorta (coefficient = 0.284, P = .031). Patients with left ventricular outflow tract aortic angles greater than 60 & DEG; had marked asymmetric flow acceler-ation on the outer curvature in the proximal aorta, ascertained from 4-dimensional flow analysis. For patients undergoing computational fluid dynamics assessment, regression analysis found that higher left ventricular outflow tract aortic angles were associated with significantly higher wall shear stress values in the outer curve of the aorta (coefficient 0.07, 95% confidence interval 0.04-0.11, P = .002): Angles greater than 50 & DEG; yielded time-averaged wall shear stress values greater than 2.5 Pa, exhibiting a linear relationship. Conclusions: Our findings strengthen the hypothesis of flow-mediated ascending thoracic aortic aneurysm disease progression and that left ventricular outflow tract aortic angle may be a predictor of disease severity. (J Thorac Cardiovasc Surg 2023;166:11-21)

Automated summary

This study investigates the relationship between the angle of the left ventricular outflow tract and ascending thoracic aortic aneurysm disease. The findings suggest that a greater angle is associated with larger diameters in the sinus and ascending aorta. Computational fluid dynamics simulations also show that a larger angle is associated with higher wall shear stress values in the outer curve of the aorta. These results support the hypothesis of flow-mediated disease progression and propose the left ventricular outflow tract angle as a predictor of disease severity.