Evaluation Of Left Atrium Energy Loss And Myocardial Function In Patients With Atrial Fibrillation Using Ultrasonic Vector Flow Mapping Combined With Two-dimensional Speckle Tracking Imaging

Objective:Assessment of left atrial myocardial function and blood flow energy loss in patients with different types of atrial fibrillation（Af）using vector flow mapping and two-dimensional speckle tracking imaging.Methods:A total of 43 patients with persistent atrial fibrillation（persistent Af group）,30 patients with paroxysmal atrial fibrillation（paroxysmal Af group）and 35 healthy volunteers（control group）were enrolled in the study.Left atrial end-systolic diameter（LADS）,left ventricular end-diastolic diameter（LVDd）,posterior wall thickness at end-diastole（LVPWd）,and inter ventricular septal thickness at end-diastole（IVSd）were measured on the long-axis view of the left ventricle near the left sternum,and the corresponding left ventricular mass index（LVMI）was calculated.The E value and A value of mitral valve orifice blood flow velocity and the velocity of mitral annulus side wall and septum were measured synchronously by pulse bi-spectral Doppler technology in apical four-chamber view,and the average value of the two values was e value,and the ratio of E to A（E/A）and the ratio of E to e（E/e）were calculated.Left ventricular ejection fraction（LVEF）was measured using the Simpson biplane method in apical four-chamber and apical two-chamber views,simultaneously obtain left atrial maximum volume(LAV_max),left atrial preliminary systole volume(LAV_pre),left atrial minimum volume(LAV_min).After BSA standardization,the corresponding left atrial maximum volume index(LAVI_max),left atrial pre-systolic volume index(LAVI_pre),and left atrial minimum volume index(LAVI_min)were obtained;Left atrial total stroke volume（LASVt）,left atrial passive stroke volume（LASVp）,left atrial active stroke volume（LASVa）,left atrial total emptying fraction（LATEF）),left atrial passive emptying fraction（LAPEF）,left atrial active emptying fraction（LAAEF）were calculated.Collect and store dynamic two dimensional gray-scale and color Doppler flow images of the left atrium in the standard apical four-chamber and two-chamber views,and import them into the post-analysis workstation offline,enter the 2D-STI analysis mode,measure the left atrial myocardial mechanical parameters,and calculate the systolic peak strain and strain rate of left atrial（SLAs,SRLAs）,early diastolic peak strain and strain rate（SLAed,SRLAed）of left atrial,atrial systolic peak strain and strain rate（SLAac,SRLAac）of left atrial.Activating VFM mode to obtain the left atrial systolic total energy loss（EL-S）and the diastolic total energy loss（EL-D）.Left atrial strain,strain rate,and EL were averaged on the apical four-chamber heart and two-chamber heart views.The differences of the above observation parameters among the three groups were compared,and the correlations between EL-S,EL-D and the left atrium structure and function parameters were analyzed.Results:（1）Comparison of general clinical parameters:The heart rate in persistent Af group was faster than that in paroxysmal Af group and control group（P<0.01）.There was no significant difference in heart rate between paroxysmal Af group and control group（P>0.05）;There was no significant difference in age,gender,BSA,BMI,SBP and DBP among the three groups（P≧0.05）.（2）Comparison of conventional echocardiographic parameters:LADs in persistent Af group were higher than those in paroxysmal Af group and control group,and LADs in paroxysmal Af group were higher than those in control group,the difference was statistically significant（P<0.05）;LVPWd and IVSd of the three groups were all within the normal reference range,LVPWd and IVSd of persistent Af group were higher than those of paroxysmal Af group and control group（P<0.05）,LVPWd and IVSd had no significant difference between paroxysmal Af group and control group（P>0.05）.Compared with control group,LVDd and LVMI increased in persistent Af group and paroxysmal Af group,but did not reach the statistical difference level（P>0.05）.LVEF of persistent Af group was lower than that of paroxysmal Af group（P<0.05）,and LVEF of three groups were all within the normal reference range.（3）Comparison of PW and TDI parameters:E in persistent Af group was higher than that in paroxysmal Af group and control group（P<0.05）.Compared with control group,E in the paroxysmal Af group was increased,but the difference between the two groups was not statistically significant（P>0.05）;e in paroxysmal Af group and persistent Af group was lower than that in control group,but the difference between persistent Af group and control group was not statistically significant（P>0.05）;E/e of persistent Af group and paroxysmal Af group was higher than that of control group,the difference was statistically significant（P<0.01）,E/e had no statistical significance between persistent Af group and paroxysmal Af group（P>0.05）;A had no statistical difference between paroxysmal AF group and control group（P=0.890）,and E/A of paroxysmal Af group was higher than that of control group,but did not reach the level of statistical difference（P>0.0 5）.（4）Comparison of left atrial volume parameters:LAVI_max and LAVI_min of persistent Af group and paroxysmal Af group were significantly higher than those in control group（P<0.01）,and those in persistent Af group were higher than those in paroxysmal Af group（P<0.05）;LATEF in persistent Af group and paroxysmal Af group was lower than that in control group（P<0.05）,and that in persistent Af group was significantly lower than that in paroxysmal Af group（P<0.01）;LAVI_pre and LASVa in paroxysmal Af group were higher than those in control group（P<0.05）;LAPEF and LAAEF in paroxysmal Af group were significantly lower than those in control group（P<0.01）;there was no significant difference in LASVt among the three groups（P>0.05）,and there was no significant difference in LASVp between paroxysmal Af group and control group（P>0.05）.（5）Comparison of left atrial myocardial mechanical parameters:SLAs and SRLAs in persistent Af group,paroxysmal Af group were lower than those in control group（P<0.01）,SLAs and SRLAs in persistent Af group were lower than those in paroxysmal Af group（P<0.01）;SLAed,SLAac,SRLAed and SRLAac in paroxysmal Af group were lower than those in control group（P<0.01）.（6）Comparison of left atrial energy loss parameters:EL-S and EL-D in persistent Af group and paroxysmal Af group were lower than those in control group（P<0.05）;compared with paroxysmal Af group,EL-S and EL-D in persistent Af group were lower,but there was no significant difference between the two groups（P>0.05）.（7）Correlation analysis:EL-S was positively correlated with LATEF,SLAs,and SRLAs（r=0.379,P<0.01;r=0.437,P<0.01;r=0.285,P<0.0）,EL-S was negatively correlated with LAAD and LAVI_max（r=-0.421,P<0.01;r=-0.345,P<0.01）;EL-D was positively correlated with LATEF,LAPEF,SLAs,SRLAs,and SRLAed（r=0.349,P<0.01;r=0.265,P<0.05;r=0.418,P<0.01;r=0.362,P<0.01;r=0.27,P<0.05）,EL-D is negatively correlated with LAAD,LAVI_max,LAVI_min,LASVa（r=-0.507,P<0.01;r=-0.446,P<0.01;r=-0.458,P<0.01;r=-0.254,P<0.05）.Conclusion:（1）Various types of Af can cause damage to left atrial myocardial function and blood flow energy,and the damage of left atrial fluid-solid mechanics is more obvious in patients with persistent Af.（2）The reduction of left atrial total EL may provide additional information for predicting the risk of thromboembolism in patients with Af,and provide a new idea and direction for clinical research on the occurrence of Af related thromboembolism and stroke complications.（3）The decrease of EL in the left atrium has a negative correlation with the index reflecting the size of the left atrium and a positive correlation with the myocardial mechanical index of the left atrium.It shows that the decrease of EL in the left atrium of Af patients is closely related to the reconstruction of the left atrium.The change of EL in the left atrium is affected by the anatomical structure of the left atrium and the changes of myocardial mechanics.（4）VFM combined with 2D-STI technology can quantitatively evaluate left atrial myocardial function and blood flow energy loss in patients with different types of Af,providing a new method for systematically observing left atrial fluid-solid mechanics in Af patients.