The Study Of The Evaluation Of Left Atrial Enlargement In The Patients With Atrial Fibrillation On Computed Tomography Angiography

Objective:To investigate the predictive value of different measurement parameters in left atrial enlargement（LAE）by measuring left atrial diameter and left atrial area on left atrial pulmonary vein CT angiography and exponentiating them with vertebral parameters and body surface area respectively,in order to find parameters for rapid and accurate diagnosis of left atrial enlargement in patients with atrial fibrillation on CT.Materials and Methods:In this study,300 patients with atrial fibrillation who underwent left atrial pulmonary vein CT angiography with dual-source CT in the department of radiology of our hospital from December 2020 to August 2021 were included,their height and weight were recorded before the examination.Left atrial volume（LAV）was measured at the end of ventricular systole（ES）and mid-diastole（MD）and recorded as LAV_ESand LAV_MDrespectively,and it was exponentiated to body surface area（BSA）and recorded as LAVI_ESand LAVI_MDrespectively.Left atrial anteroposterior diameter（LAD1）,left atrial transverse diameter（LAD2）and left atrial area（LAA）were measured at the ostium of the right inferior pulmonary vein at the slice with the largest left atrial area.The left atrial measurement parameters were recorded as LAD1_ES,LAD2_ES,LAA_ESin ES phase and LAD1_MD,LAD2_MDand LAA_MDin MD phase respectively.The vertebral body at the same level as the left atrial parameter measurement was selected,and the anteroposterior diameter of the vertebral body,the transverse diameter of the vertebral body,and the vertebral area were measured at the level 1/2 of the center of its upper and lower diameter lines and recorded as VD1,VD2,and VA,respectively.The atrial to vertebral ratio was obtained by dividing the measured parameters of the left atrium by the measured parameters of the thoracic spine,including the anteroposterior diameter ratio of the atrium（LAVD1=LAD1/VD1）,the transverse diameter ratio of the atrium（LAVD2=LAD2/VD2）,and the area ratio of the atrium（LAVA=LAA/VA）.The parameters were recorded as LAVD1_ES,LAVD2_ES,LAVA_ESin the ES phase and LAVD1_MD,LAVD2_MD,and LAVA_MDin the MD phase respectively.Left atrial indices,including left atrial anteroposterior diameter index（LADI1=LAD1/BSA）,left atrial transverse diameter index（LADI2=LAD2/BSA）,and left atrial area index（LAAI=LAA/BSA）,were obtained by indexing the left atrial measurement parameters with BSA respectively,and recorded as LADI1_ES,LADI2_ES,LAAI_ESin ES phase,and LADI1_MD,LADI2_MD,LAAI_MDin MD phase respectively.According to the literature,all patients were divided into left atrial enlargement group and normal left atrium group using LAVI_ES>77.7ml/m2 as the reference standard.Statistical analysis used Pearson’s correlation coefficient to assess the correlation between LAV_ESand LAV_MD,LAVI_ESand LAVI_MD,all measured parameters and LAV_ES/LAVI_ESrespectively.Bland-Altman curves and interclass correlation coefficients（ICC）were used to evaluate intra-observer and inter-observer agreement for all the above measured parameters.Using LAVI_ES>77.7 ml/m2 as the reference standard,ROC curves were plotted to assess the efficacy of each measured parameter in the diagnosis of LAE（area under the curve,sensitivity,specificity,positive predictive value,negative predictive value,and coincidence rate）,and finally a method for rapid and accurate diagnosis of left atrial enlargement on CT cross-section was obtained.Results:1.A total of 227 patients were enrolled in the analysis.The left atrium enlargement was present in 44.5%（101 patients）of all the patients.There was no statistically significant difference in the general data between the two groups of patients with enlarged and normal left atrium（P>0.05）.2.There was a good positive correlation between LAV_ESand LAV_MD（r=0.983,P<0.001）,LAVI_ESand LAVI_MD（r=0.984,P<0.001）,LAA_ESand LAVI_ES（r=0.817,P<0.001）,LAA_MDand LAVI_ES（r=0.814,P<0.001）.3.All measured parameters had good agreement within and between observers.The ICC for LAA_ESand LAA_MDwere 0.914 and 0.928 within observers,0.907 and 0.902between observers,respectively.4.According to the results of ROC curve,all measured parameters（left atrial diameter,left atrial diameter index,left atrial area,left area index）are feasible for the diagnosis of left atrial enlargement,and the diagnostic efficacy from high to low is left atrial area/area index,left atrial diameter,and left atrial diameter index.The diagnostic efficacy of left atrial diameter was superior to that of left atrial diameter index:AUC of LAD1_ESand LAVD1_ES（0.810 vs 0.766,P=0.0149）,AUC of LAD2_ESand LAVD2_ES（0.881 vs 0.766,P=0.0001）,AUC of LAD2_ESand LADI2_ES（0.881 vs 0.787,P=0.0006）,AUC of LAD1_MDand LAVD1_MD（0.795 vs 0.754,P=0.0385）,AUC of LAD2_MDand LAVD2_MD（0.860 vs 0.777,P=0.0016）;AUC of LAD2_MDand LADI2_MD（0.860 vs 0.794,P=0.0044）;the diagnostic efficacy of left atrial transverse diameter was superior to that of left atrial anteroposterior diameter:AUC of LAD2_ESand LAD1_ES（0.881 vs 0.810,P=0.0187）,AUC of LAD2_MDand LAD1_MD（0.860 vs 0.795,P=0.0459）;the differences in diagnostic efficacy for left atrial area and area index were not statistically significant:AUC for LAA_ESand LAAI_ES（0.917 vs 0.926,P=0.4603）,AUC for LAA_MDand LAAI_MD（0.913 vs 0.911,P=0.8407）,with preference given to the use of left atrial area because it is more readily available than the left atrial area index.The use of left atrial area was considered first.The diagnostic efficacy of left atrial area was superior to that of left atrial transverse diameter:AUC of LAA_ESand LAD2_ES（0.917 vs 0.881,P=0.0336）,and AUC of LAA_MDand LAD2_MD（0.913 vs 0.860,P=0.0042）.5.It evaluated the diagnostic efficacy of LAE When the LAA_ESthreshold was 28.63cm2（AUC:0.917,Se:84.2%,Sp:88.9%,PPV:85.9%,NPV:87.5%,coincidence rate86.8%）,and when LAA_MDthreshold was 25.58cm2（AUC:0.913,Se:79.2%,Sp:88.1%,PPV:84.1%,NPV:84.1%,coincidence rate 84.1%）.Conclusion:Axial left atrial area can be used as a rapid and accurate parameter for the diagnosis of LAE in patients with atrial fibrillation on CT angiography.This study suggests that LAA_ES>28.63 cm²or LAA_MD>25.58 cm²has high sensitivity and specificity for the diagnosis of LAE in patients with atrial fibrillation.