Longitudinal Mechanical Characteristics Of Aortic Root In Normal Adults:A Two-dimensional Strain Study

Background Two-dimensional speckle tracking echocardiography(2D-STE)has been gradually used to evaluate the deformations of aorta in recent years.However,the regional longitudinal mechanical informations determined by the waveforms at different time intervals have rarely been reported.The aim of this study was to assess the mechanical motion characteristics of the aortic root in 208 healthy adult volunteers via 2D-STE.Methods A total of 220 healthy volunteers who underwent physical examinations were enrolled in the Second Affiliated Hospital of Dalian Medical University from March 2019 to Novembre 2020,among the enrolled healthy volunteers,12 were excluded due to poor image quality of echocardiography.The remaining 208 healthy volunteers(109 males and99 females,range: 20–71 years)were devided into four groups by age: group A(20 to 29 years old),group B(30 to 39 years old),group C(40 to 49 years old),and group D(50years old or above).The gender,height,weight,body surface area(BSA)and other basic information of each subject were recorded.Systemic arterial pressure was measured from the left brachial artery with an arm-cuff sphygmomanometer and pulse pressure(PP)was measured.The parasternal long-axis view of the left ventricle and proximal AAo,and apical two-,three-,and four-chamber views were recorded and stored during three consecutive cardiac cycles.Left ventricular ejection fraction(LVEF)and stroke volume were measured by Simpson’s biplane method,the stroke volume index(SVI)was calculated as the stroke volume divided by BSA.All of the images were transferred and analyzed with QLAB 10.5 off-line analysis software.The Valsalva sinus(VS)was subdivided into four segments for speckle tracking,namely the anterior aortic annular segment(AAA-VS),the posterior aortic annular segment(PAA-VS),the anterior sinotubular junction segment(ASJ-VS),and the posterior sinotubular junction segment(PSJ-VS).Four points were put on the walls of each segment and edited manually to fit the aortic border properly.The LS and LSR curves of the regional aortic root were generated automatically.The peak values of longitudinal strain(LS)and the peak values of longitudinal strain rate(LSR)in systole of the different segments were measured.Global longitudinal strain of left ventricle(LVGLS)was measured in the apical views.The LS and LSR values of the regional VS and proximal AAo were compared using analysis of variance(ANOVA).The correlation between age,LVGLS,SVI,PP and the peak LS values were assessed using Pearson’s correlation coefficient,and the correlation between LVGLS,SVI,PP and the peak systolic LSR of the VS were assessed using Pearson’s correlation coefficient.The Bland-Altman test and the intraclass correlation coefficients(ICC)were used to show the measurement reliability of the LS and LSR values.Results The LS curves of AAA-VS and PAA-VS were similar,the LS curves of AAAVS and PAA-VS were above the baseline,and the strain values were positive as well.The waveform characteristics showed a sharp rise during isovolumic contraction(IVC)and rapid ejection period,which was followed with a relatively slow ascending branch until the peak occurred at the end of isovolumic relaxation(IVR).The waveform demonstrated a drop during the rapid filling interval,followed by a slow decline during the reduced filling interval.Additionally,a notch with a minor peak was seen during the atrial systolic interval.The LS curves of ASJ-VS and PSJ-VS were similar,the waveform characteristics showed a short uptrend during IVC and the rapid ejection period,followed by a rapid decrease to the bottom until the aortic valve closed.The LS curves of ASJ-VS and PSJVS showed another rise during early diastole,and a very slow decline afterwards.There was also an incisura notch in the atrial systolic interval.The LS values of the VS and AAo were negatively correlated with age(r =-0.614,-0.507,P < 0.001),positively correlated with LVGLS(r = 0.487,0.313,P < 0.001),and positively correlated with SVI(r = 0.321,0.336,P < 0.001).There was no significant correlation between LS,peak systolic LSR values of aortic sinus and PP.The peak systolic LSR values of AA-VS and SJ-VS were positively correlated with LVGLS(r = 0.512,0.541,P < 0.001),respectively,but had no significant correlation with SVI.Furthermore,the LS values of anterior wall of aortic sinus and ascending aorta were lower than those of posterior wall(P < 0.001).Conclusions The waveforms of the LS and LSR curves of the aortic root in normal adults had the segmental characteristics.The longitudinal mechanical deformations of the aortic root showed regional variations.The LS of the aortic root are correlated with age,SVI and LVGLS.In addition,The systolic peak LSR values was useful to the further assess in understanding the ventricular-arterial coupling relationship.