Wall Stress And Geometry Of The Thoracic Aorta In Patients With Aortic Valve Disease

BACKGROUND: Aortic valve disease increases velocity and changes the way blood enters the aorta. Over time, the biomechanical environment can cause aortic remodelling. We hypothesised that aortic geometry and wall stress would be different in patients with aortic valve disease compared to controls.

METHODS: We examined 40 patients with aortic sclerosis (n=10), mild (n=10), moderate (n=10) and severe (n=10) aortic stenosis, and also 10 control cases. The thoracic aorta of each case was reconstructed into a three-dimensional model from computed tomography. We measured geometric parameters and used finite element analysis to compute aortic wall stress. Statistical analyses were performed to test our hypothesis.

RESULTS: Aortic wall stress was significantly associated with tortuosity of the descending aorta (r=0.35, p=0.01), arch radius (r=0.49, p<0.01), ascending aortic diameter (r=0.59, p<0.01) and aortic centreline length (r=0.39, p<0.01). Wall stress was highest in patients with severe stenosis (p=0.02), although elevations in wall stress were also noted in subjects with mild stenosis (p=0.02), and aortic sclerosis (p=0.02) compared to controls. Similar trends were observed when we corrected for difference in blood pressure. Total centreline tortuosity was higher in patients with severe aortic stenosis compared to controls (p=0.04), as was descending aorta tortuosity (p=0.04).

CONCLUSIONS: Aortic geometry is associated with aortic wall stress. Patients with aortic valve disease have higher aortic wall stress than control cases, and those with severe aortic stenosis have more tortuous aortas. However, increases in geometric measures and wall stress are not stepwise with increasing disease severity.