2.3 Echocardiographic image analysis
(1) RT-3DE: Philips Qlab 10. 4 software was used to off-line analyze the full-volume image. In the 3DQA mode, the left atrial volume curve was obtained, and we recorded the maximal, minimal and pre-atrial contraction left atrial volume (LAVmax, LAVmin, LAVp). Then, each left atrial volume index (LAVImax, LAVImin, LAVIp) was obtained by normalizing BSA. Finally, we calculated LATEF, LAAEF and LAPEF. the calculation method was as follows: LATEF= (LAVImax-LAVImin)/LAVImax×100%; LAAEF= (LAVIp-LAVImin)/LAVIp×100%; LAPEF= (LAVImax-LAVIp)/LAVImax×100%. (2) 2D-STI: Off-line analysis of apical two-chamber and four-chamber images of four consecutive cardiac cycles using Philips Qlab 10. 4 software. In the aCMQ mode, we recorded the intima of the left atrium and plotted the region of interest to obtain the left atrial strain curve. LASr, LASct and LAScd were recorded respectively, and the strain values of the the two views were added together and included in the analysis after averaging. The mean peak strain during left atrial systole, late diastole and early diastole respectively represents LASr, LASct and LAScd. Where LASr is positive, LASct and LAScd are both negative, so the absolute value was taken and analyzed.