| Objective : To evaluate left atrial energy loss(EL)based on vector flow mapping(VFM)in patients with essential hypertension,and to explore its clinical application potential.Methods : Ninty-one cases of hypertension patients were enrolled,those patients were divided into without left atrial enlargement group(group one,n=41)and left atrial enlargement group(group two,n=46)according to the left atrial volume index,and another 32 healthy persons were enrolled as control group.The left ventricular diameter(LVDd),septum diameter(IVSd)and left ventricular posterior wall diameter(LVPWd)were measured at the end diastole of left ventricle in long axis view.The left ventricular mass index(LVMI)and the left ventricular relative wall thickness(LVRWT)were calculated.The dual pulse-wave dopller technology was used to obtain the E peak velocity of mitral valve(E),A peak velocity of mitral valve(A),e peak velocity of mitral annulus at lateral wall of left ventricle(e),a peak velocity of mitral annulus at lateral wall of left ventricle(a),the ratio of E/A(E/A),the ratio of E/e(E/e),isovolumetric relaxation time(IVRT)and E peak deceleration time of mitral valve(EDT).The maximal left atrial volume,left atrial preliminary systole volume at the time of the P wave on the surface electrocardiogram,minimum left atrial volume were measured by double plane Simpson’s methods.The above volume values were divided by the surface area to obtain the maximal volume index of left atrium(LAVImax),left atrial preliminary systole volume index of left atrium(LAVIpre)and left atrium minimum volume index of left atrium(LAVImin),the total ejection volume(LASVt),passive ejection volume(LASVp),active ejection volume and(LASVa)of left atrium as well as the total ejection fraction(LATEF),passive ejection fraction(LAPEF),active ejection fraction(LAAEF)of left atrium.Two dimensional dynamic images of left atrium in apical four-chamber view were collected and those images were imported into workstation,the systolic peak strain of left atrial(SLAs),early diastolic peak strain of left atrial(SLAed),late diastolic peak strain of left atrial(SLAac),systolic peak strain rate of left atrial(SRLAs),early diastolic peak strain rate of left atrial(SRLAed)and late diastolic peak strain rate of left atrial(SRLAac)were achieved by the Two-dimensional ultrasound tissue tracking(2DTT)technology.The two dimensional color doppler dynamic images of left atrium of apical four-chamber view were obtained by the VFM technology and those dynamic images require a Frame rate >18 frame/sec and the blood flow sampling frame must wrap around the whole left atrium and clearly display the inflow path,import those images into workstation,a complete cardiac cycle was divided into 3 periods of Rapid ejection period,early diastolic period and atrial systolic period,according to the time flow curve,electrocardiogram and valve open and closure timing,and then,selected the "energy loss" option,drawed the left atrial endocardium and acquired the left atrial mean energy loss during rapid ejection period(EL-S),left atrial mean energy loss during Left ventricular early diastolic period(EL-ED)and left atrial mean energy loss during atrial systolic period(EL-AC).All parameters were tested by normality test and variance homogeneity test.The continuous variables that showed the normal distributions were expressed by Mean±standard deviation,difference among the three group in which data showed the normal distributions and homogeneity of variance was analyzed with ANOVA test,Post Hoc was used LSD method.Welch test is used for data that showed the normal distributions but did not showed the homogeneity of variance,Post Hoc was used the Dunnett T3 method,Correlation between two variables was analyzed with Pearson correlation.The data which did not showed normal distribution and homogeneity of variance were expressed in median(four bits interval),rank sum test was adopted,and correlation between two variables was analyzed with Sperman correlation.The independent factor of energy loss was used multiple linear regression analysis method.The Bland-Altman analysis method was used to test the repeatability.P<0.05 was considered as significant.Results : 1.General information and serum biochemical indicators: There were no significant difference of age,high density lipoprotein,low density lipoprotein,total cholesterol,and glucose between the three groups(P>0.05).The low density lipoprotein of group two was higher than that of control group(P<0.05),systolic pressure,diastolic pressure,body mass index,body surface area and triglyceride were both in group one and group two were all higher than those in control group(P<0.05).There was no significant difference between group one and group two(P > 0.05).2.Parameters of two-dimensional echocardiography and Doppler :(1)Parameters of two-dimensional echocardiography: There were significant differences in AAO,LVMI,LVDd,LVPWd,IVSd and LVRWT between the three groups(P<0.05).AAO and LVMI in Group two were higher than those of control group and group one(P<0.05),AAO and LVMI in the group one was higher than the control group(P<0.05),LVDd in Group two was higher than that of the control group and group one(P<0.05),and there was no significant difference between the group one and the control group(P>0.05).LVPWd,IVSd and LVRWT in Group two and group one were higher than those of control group(P<0.05),and there was no singnificant difference between group one and group two(P>0.05).There was no significant difference in LVEF between the three groups(P>0.05).(2)The Doppler ultrasound parameters: There were significant difference of A,E/A,E/e,IVRT,EDT,E between the three groups(P<0.05);A,E/A in group two were higher than the control group and the group one,and group one was higher than that of control group(P<0.05);e,a,E/e and IVRT in group two and group one were higher than that of the control group(P < 0.05),but group one and group two showed no significant difference(P>0.05);EDT in group two was higher than that of the control group(P<0.05),there was no significant difference between the group and the control group(P>0.05);E in The group one was higher than the control group,and the E in group two was higher than the group one(P<0.05),and there was no significant difference between the group two and the control group(P>0.05).3.left atrium Volume parameters: LAVImax,LAVIpre,LAVImin,LASVt,LASVp,LASVa,LAPEF and LAAEF in Group two were all higher than those in control group and group one(P<0.05),and there was no significant difference between group one and control group(P>0.05).There was no singnificant of LATEF between the three groups.4.The mechanical parameters of the left atrium: There were singnificant difference of SLAs,SLAed,SLAac,SRLAs,SRLAed and SRLAac between the three groups(P<0.05 or P<0.01);SLAs and SLAed in group one and group two were lower than the control group,and the group of two lower than that in group one(P<0.05 or P<0.01);SLAac,SRLAed in group two lower than the control group(P<0.05 or P<0.01),and there were no significant difference between group one and group two(P>0.05);SRLAs in group one and group two were lower than the control group(P<0.05),but group one and group two showed no significant difference(P>0.05);SRLAac in group two was higher than of the control group and group one(P<0.05),there was no significant difference between the group one and the control group(P > 0.05).5.Parameters of left atrial energy loss: EL-S:Group one and group two were higher than those of control group,and group two was higher than group one(P<0.05 or P<0.01).EL-ED: Group two was lower than control group(P<0.05),there was no significant difference between the group one and the control group(P>0.05).EL-AC:Group one and group two were higher than those of control group,and group two was higher than group one(P<0.05 or P<0.01).6.regression analysis:The independent factors of EL-S: SRLAS(β =-0.399,P<0.001)、SRLAac(β = 0.263,P=0.001)、EL-AC(β = 0.366,P<0.001);The independent factors of EL-ED:EL-AC(β =0.254,P=0.015)、a(β =-0.274,P=0.001)、EDT(β =-0.178,P=0.040);The independent factors of EL-AC:EL-S(β =0.426,P<0.001)、EDT(β =0.173,P=0.025)、a(β =0.178,P=0.026)、e(β =-0.230,P=0.003)。Conclusion: 1.When the size of left atrium not increased,although there was no significant changes of left atrial volume,but left atrial mechanical parameters have significantly changes compared with the control group,the impairment of left atrial function was earlier than that of the structure.2.In the group of without left atrial enlargement,the energy loss of systolic and late diastolic period were higher than that in the control group,and the energy loss parameter was earlier than the left atrial volume to reflect atrial function.3.The left atrial volume and left atrial energy loss in the left atrial enlargement group were significantly different than those in the control group and the group without left atrial enlargement,suggesting that the structure and function in the left atrial enlargement group were impaired.4.In the stage of left atrial enlargement,left atrium passive emptying fraction decreased,active emptying fraction increased which compensate left ventricular filling insufficiency in early left ventricular diastolic period,left atrial active contractility enhanced,compensatory changes in blood flow of left atrium in late diastolic period,The energy loss increased.5.Left atrial strain rate in systolic period,left atrial strain rate in late diastolic period and left atrial energy loss late diastolic period were independent factors of left atrial energy loss in systolic period,suggestting the interaction between the mechanical and flow field of the left atrium,The damage to the mechanics of the left atrium was accompanied by a change in the blood flow field in the left atrium.6.The Doppler parameter of a peak and E peak deceleration time were independent factors of left atrial energy loss in early diastolic period and late diastolic period,the changes of the structure and function of the left atrium were accompanied by the changes of diastolic function,he diastolic function parameters were positively related to the energy loss parameters. |
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