Aortic Viscous Energy Loss for Assessment of Valve-related Hemodynamics in Asymptomatic Severe Aortic Stenosis

Purpose: To investigate whether functional assessment of aberrant flow patterns by viscous energy loss (E-L') using four-dimensional (4D) flow MRI could determine aortic stenosis (AS) severity in accordance with transvalvular energy loss and aid in surgical decision-making in asymptomatic patients with severe AS. Materials and Methods: In this prospective, single-center study, E-L' was measured in the thoracic aorta of 74 consecutive asymptomatic patients with severe AS and preserved left ventricular ejection fraction who presented between January 2015 and December 2017, and 23 healthy volunteers using 4D flow MRI. Transvalvular energy loss was assessed based on the energy loss index (ELI) measured using Doppler echocardiography. The association between E-L' and AS-related events including aortic valve replacement was evaluated by receiver operating characteristic curve analysis, Kaplan-Meier analysis, and multivariable Cox regression analysis. Results: Among 74 asymptomatic patients with severe AS (mean age, 60 years +/- 9 [SD]; 43 men; 56 with bicuspid aortic valve), 33 experienced AS-related events during a median follow-up of 42 months (IQR, 30-53 months). Altered flow patterns in severe AS resulted in a sevenfold increase in peak systolic E-L' in the ascending aorta compared with controls (13.9 mW +/- 3.4 vs 1.80 mW +/- 0.44; P < .001). Peak systolic E-L' in the ascending aorta was independently associated with the ELI (standardized beta, -0.52; P < .001) and showed better discrimination for AS-related events (area under the curve, 0.83; 95% CI: 0.74, 0.93; P < .001) than conventional echocardiographic parameters. After adjustment for confounding variables, peak systolic E-L' in the ascending aorta was associated with a significant increase in AS-related events (P < .001 for adjusted hazard ratio). Conclusion: Changes in AS-mediated poststenotic three-dimensional outflow patterns can be quantified by 4D flow MRI-derived ener-getic markers to aid in the risk stratification and clinical management of asymptomatic patients with severe AS. (C) RSNA, 2022

Automated summary

Functional assessment of aberrant flow patterns by viscous energy loss (E-L') using four-dimensional (4D) flow MRI can determine aortic stenosis (AS) severity and aid in surgical decision-making in asymptomatic patients with severe AS.