Study On The Diagnosis And Treatment Of Aortic Valve Insufficiency Based On 4D Flow MRI

Objective:In this study,four-dimensional magnetic resonance imaging(4D Flow MRI)was used to analyze the hemodynamic parameters of aorta in patients with aortic regurgitation,to provide basis for diagnosis and treatment of aortic insufficiency,and to explore the correlation between aortic dilatation and hemodynamic changes..Materials and methods:This study prospectively included 30 patients with aortic valve insufficiency(AI)who underwent CMR examination in the first Hospital of Lanzhou University from May 2020 to December 2022,including 18 patients with AI and aortic dilatation and 12 patients with AI but normal aorta.At the same time,30 age-and sex-matched healthy volunteers were recruited as the control group to record the clinical baseline data of the patients.The left ventricular function parameters and hemodynamic parameters such as aortic forward flow,reverse flow,eddy current,spiral flow and wall shear stress(WSS)were obtained by CVI post-processing software.The differences among and within the three groups were analyzed by SPSS 28.0 statistical software.This study is divided into three parts:1.Pearson and spearman correlation tests were used to study the consistency of quantitative aortic insufficiency parameters between 4D Flow MRI and TTE.Cohen’s Kappa is used to calculate the semi-quantitative consistency of spiral or eddy current among observers,and to study the correlation between the occurrence and intensity of spiral or eddy current and aortic diameter.3.Independent sample t-test or Mann-Whitney U test was used to study the changes of six-plane hemodynamic parameters in patients with AI and healthy volunteers.Results:(1)There was a good correlation between 4D Flow MRI and TTE in evaluating AI(κ=0.79).There was a linear correlation between 4D Flow MRI and TTE in measuring forward blood flow,reverse blood flow and reflux fraction in patients with AI(R~2=0.775,0.765,0.874 respectively,P<0.05).(2)There was a good consistency among the observers of blood flow pattern classification(κ=0.86).The incidence of hyperphysiological helical flow in ascending aorta in patients with AI and aortic dilatation was significantly higher than that in AI but normal aorta group and healthy volunteers group(P=0.004 and P=0.003).Vortical flow was seen in the ascending aorta of most patients with incomplete closure and dilatation of the aorta(17/18,94%),but there was vortical flow in the ascending aorta in the normal aorta group(6/12,50%),and there was no vortical flow in the healthy volunteers group.The vortex intensity in patients with AI and aortic dilatation was significantly higher than that in patients with AI but normal aorta(1.5±0.6 vs.0.6±0.7,P=0.004).The occurrence and intensity of hyperphysiological helical flow and vortical flow currents on the ascending aorta are directly related to the increase of AAO diameter and AAO/DAO diameter ratio.(3)The peak flow velocity of AI patients was lower than that of healthy volunteers at six levels,the axial and circumferential WSS of AI patients was lower than that of healthy volunteers at plane 1 and 2,and the axial WSS of AI and aortic dilatation group was lower than that of AI but normal aorta group and healthy volunteers group[(0.129±0.046)vs.(0.170±0.035)vs.(0.206±0.056),P<0.056].The axial and circumferential WSS of patients with dilated aorta was lower than that of AI in patients with aortic dilatation at plane 4 and 5,but there was no significant difference in axial WSS between normal aorta group and healthy volunteers at plane 6.Conclusion:4D Flow MRI technique can be used to analyze the hemodynamic parameters of patients with AI noninvasively.The occurrence and intensity of hyperphysiological helical flow and vortical flow on ascending aorta are directly related to the increase of aortic diameter.The peak velocity and axial WSS parameters of patients with AI and aortic dilatation decrease more significantly,which can provide a basis for the diagnosis and treatment of AI.