Evaluation of Aortic Blood Flow and Wall Shear Stress in Aortic Stenosis and Its Association With Left Ventricular Remodeling

Abstract

Background— Aortic stenosis (AS) leads to variable stress for the left ventricle (LV) and consequently a broad range of LV remodeling. The aim of this study was to describe blood flow patterns in the ascending aorta of patients with AS and determine their association with remodeling. Methods and Results— Thirty-seven patients with AS (14 mild, 8 moderate, 15 severe; age, 63±13 years) and 37 healthy controls (age, 60±10 years) underwent 4-dimensional-flow magnetic resonance imaging. Helical and vortical flow formations and flow eccentricity were assessed in the ascending aorta. Normalized flow displacement from the vessel center and peak systolic wall shear stress in the ascending aorta were quantified. LV remodeling was assessed based on LV mass index and the ratio of LV mass:end-diastolic volume (relative wall mass). Marked helical and vortical flow formation and eccentricity were more prevalent in patients with AS than in healthy subjects, and patients with AS exhibited an asymmetrical and elevated distribution of peak systolic wall shear stress. In AS, aortic orifice area was strongly negatively associated with vortical flow formation ( P =0.0274), eccentricity ( P =0.0070), and flow displacement ( P =0.0021). Bicuspid aortic valve was associated with more intense helical ( P =0.0098) and vortical flow formation ( P =0.0536), higher flow displacement ( P =0.11), and higher peak systolic wall shear stress ( P =0.0926). LV mass index and relative wall mass were significantly associated with aortic orifice area ( P =0.0611, P =0.0058) and flow displacement ( P =0.0058, P =0.0283). Conclusions— In this pilot study, AS leads to abnormal blood flow pattern and peak systolic wall shear stress in the ascending aorta. In addition to aortic orifice area, normalized flow displacement was significantly associated with LV remodeling.