Introduction: The aim of this study was to evaluate the utility of 2D-STI and real-time three-dimensional echocardiography (RT-3DE) in assessing changes in left atrial (LA) structure and function in patients with paroxysmal atrial fibrillation (PAF) post-radiofrequency catheter ablation (RFCA). Methods: A retrospective analysis was conducted on 44 PAF patients who underwent RFCA at BA Hospital from March 2022 to March 2023. An age- and gender-matched control group of 32 healthy individuals was also included. Comprehensive echocardiographic parameters including LA dimensions (LAAPD, LALRD), volumes (LAVmin, LAVmax), ejection fraction (LAEF), and tissue velocities (a’, Ar) were compared between groups. Post-RFCA changes in these parameters were also assessed at 1, 3, and 6 months. Results: Pre-RFCA, PAF patients demonstrated larger LA dimensions and volumes with reduced LAEF and tissue velocities compared to controls. Post-RFCA, there was a significant improvement in LAEF and left ventricular ejection fraction at 1, 3, and 6 months, with the most pronounced changes observed at 6 months. LA dimensions increased initially but then decreased from 1 to 6 months post-RFCA. Notably, strain rate (SRS, SRE, SRA) measurements in various LA segments improved progressively, with the most significant enhancements at 6 months, suggesting improved atrial mechanics. Conclusion: The application of 2D-STI and RT-3DE provides a quantitative means to evaluate the structural and functional changes in the LA of PAF patients following RFCA. The progressive improvements in LA dimensions, volumes, and strain measurements up to 6-month post-RFCA indicate the potential of these techniques in monitoring treatment efficacy and patient recovery.

Atrial fibrillation (AF) is one of the most prevalent sustained arrhythmias that seriously endanger public health, which can lead to deterioration of cardiac function, physical decline, and, in severe cases, arterial thromboembolism, posing great threat to human health [1]. Clinically, AF is often divided into paroxysmal atrial fibrillation (PAF), persistent AF, and permanent AF, with PAF being the initial symptom for most patients [2].

Therefore, it is of great significance to treat AF. Currently, radiofrequency catheter ablation (RFCA) is the most widely used therapy for PAF, and an increasing number of studies have shown that RFCA can cure AF and improve clinical symptoms, the quality of life, and cardiac function of patients while improving their survival rates [3, 4]. Meanwhile, RFCA has been found to reduce the risk of stroke and transient ischemic attack in AF patients without increasing their risk of heart failure compared with medical therapies [5]. Numerous studies have suggested that RFCA may be superior to medical therapies in the treatment of PAF. However, as an invasive therapy, structural and functional changes in the left atrium of patients after radiofrequency ablation are of great concern [6].

Currently, echocardiography is widely applied in preoperative evaluation and postoperative assessment of left atrial (LA) function in AF patients undergoing radiofrequency ablation. Despite being able to dynamically measure changes in LA volume at different phases of the cardiac cycle, calculate active and passive injection fractions of the left atrium, and reflect LA function from a volumetric perspective [7], conventional two-dimensional echocardiography typically employs the Simpson’s area-length method to measure LA volume [8]. Meanwhile, due to the highly irregular morphology of the left atrium, the conventional method of geometric modeling for LA calculation has certain theoretical limitations, which restricts its clinical application [9]. By contrast, real-time three-dimensional echocardiography (RT-3DE) is a newly developed echocardiographic technique that can visually and dynamically display the 3D anatomical structure of the heart in real time. In particular, when measuring LA volume with RT-3DE, there is no need for assumptions on the geometric shape of the left atrium as with 2D echocardiography, which can directly display the authentic structure of the left atrium, with the advantages of simple operation, real-time collection, thus providing a more comprehensive, realistic, and accurate assessment of LA function.

As an advanced technique used in recent years both domestically and globally to evaluate changes in LA function [10], 2D-STI can track the acoustic speckle motion of the myocardium in a noninvasive way to obtain indicators such as myocardial tissue velocity, strain, and strain rate (SR), making it a more sensitive technique for evaluating changes in LA function. Due to the fact that myocardial deformation is not affected by the traction of surrounding tissues or the heart’s own movement, this technique is not influenced by the angle of the ultrasound bean and can quantitatively assess myocardial motion in various directions such as longitudinal, radial, and tangential directions, with better signal-to-noise ratio, image stability, and low variability, making it the optimal approach for quantifying overall and local cardiac function at present [11].

In comparison, real-time 3D ultrasonography can directly obtain the overall volume of the left atrium without relying on geometric assumptions. 2D-STI technique is a novel ultrasound quantitative analysis tool that can quantitatively analyze myocardial motion speed, strain, and SR in 2D grayscale dynamic images, providing a novel approach for clinically evaluating overall and local heart function. In recent years, several studies have validated the feasibility of evaluating LA function with the noninvasive 2D-STI technique [12, 13]. In this study, RT-3DE combined with 2D-STI was utilized to evaluate LA volume and myocardial deformation function in PAF patients, along with follow-ups on changes in LA remodeling and function pre- and post-RFCA, thereby providing an objective reference for the treatment and prognosis assessment of patients.

This study was conducted in accordance with the Declaration of Helsinki and approved by the Research Ethics Committee of Beijing Anzhen Hospital, approval number: 2024098X. Due to the nature of retrospective study and anonymized patient’s information, informed consent is waived with the approval of Ethics Committee of Beijing Anzhen Hospital. All methods were carried out in accordance with relevant guidelines and regulations.

Research Subjects

Patients with PAF who underwent successful RFCA in the Cardiology Department of BA Hospital, CM University, from March 2022 to March 2023 were retrospectively collected using convenience sampling. The control group was selected based on a similar sampling principle to ensure representativeness and matched for age and gender to the PAF patient group, who underwent physical examinations during the same period. These controls were confirmed to have no history of AF or other significant cardiovascular diseases and had normal echocardiographic findings. Inclusion criteria were as follows: (1) patients who met the diagnostic criteria for PAF as outlined in the 2019 ACC/AHA/ESC Guidelines for the Management of Atrial Fibrillation [14]: AF episodes lasting no longer than 24 h or self-converting to sinus rhythm within 7 days; (2) patients who successfully reverted to sinus rhythm after RFCA and maintained it for 3 days. Exclusion criteria were as follows: (1) age <30 or >80 years old; (2) atients with valvular heart disease, untreated hyperthyroidism, uncorrected electrolyte disturbances; (3) patients with intra-atrial thrombus detected by transesophageal echocardiography; (4) patients with impaired liver or kidney function; (5) patients with concurrent cerebrovascular accidents or other neurological disorders; (6) patients diagnosed with persistent or permanent AF, those experiencing AF recurrence within 3 days after ablation, and those with unsuccessful surgery; (7) patients with poor acoustic windows or inability to cooperate with the examination. AF recurrence was defined as any atrial tachyarrhythmia lasting longer than 30 s on a 24-h Holter monitor or 12-lead electrocardiogram performed 3 months after the surgery [15].

Research Methods

Radiofrequency Ablation

All patients underwent electrophysiological examination and radiofrequency ablation. Prior to the procedure, routine intracardiac electrophysiological examination was performed, and individualized ablation strategies were determined based on the results of the electrophysiological examination. The main steps included puncturing both femoral veins, placing a coronary sinus electrode, introducing a transseptal sheath into the atrial septum, and performing transseptal puncture, followed by the angiography for left atrium and pulmonary veins. After completing LA mapping, a cryoablation catheter was used for pressure-controlled radiofrequency ablation at 43°C and 30W for circumferential pulmonary vein isolation, with local discharge no longer than 60 s. Ablation endpoint: immediate disappearance of AF that cannot be induced; and disappearance of pulmonary vein potentials with bidirectional conduction block between the left atrium and pulmonary veins, and intact circumferential pulmonary vein lines. All procedures were performed using the CARTO system (Biosense Webster). In addition, all patients received subcutaneous injections of low molecular weight heparin for 3 days preoperatively and intravenous unfractionated heparin intraoperatively. After radiofrequency ablation, all patients were prescribed oral anticoagulants and antiarrhythmic drugs following medical advice.

Echocardiographic Examination

The Philips EPIQ-7C color Doppler ultrasound diagnostic instrument was used, with a 2.0–3.5 MHz 2D phased array probe (S5-1) and a 1–3 MHz 3D matrix probe (X5-1), equipped with the QLAB 13.0 image analysis software package. The subjects were placed in the left lateral position, breathing calmly, and connected to an electrocardiogram. Routine M-mode and 2D echocardiographic measurements were performed. Three to five 2D images of the parasternal long axis, parasternal short axis, apical four-chamber view, and apical two-chamber view were obtained over 3–5 cardiac cycles, with a frame rate of 60–90 FPS. All images were stored on a hard drive for offline analysis. Afterward, the probe was switched to X5-1, and clear 2D images were obtained in the standard apical four-chamber view. The “HM ACQ” imaging key was activated, with the endocardium of the left atrium completely placed in the sampling box, and the probe position was fixed, with patients instructed to hold their breath, followed by capturing images and storing them on the instrument’s hard drive. All dynamic images were stored in the DICOM format, and all parameters were measured 3 times, with the average value taken. The QLAB 13.0 software was used for quantitative analysis of both 2D and 3D images.

Examination Indicators

Following the guidelines of the American Society of Echocardiography (ASE) [16], routine baseline parameters were measured: the parasternal long axis view was used to measure the left atrial anteroposterior diameter (LAAPD), left ventricular end-diastolic diameter (LVEDD), and left ventricular end-systolic diameter (LVESD). The left ventricular ejection fraction (LVEF) was calculated using the biplane Simpson method following the ASE guidelines. Meanwhile, the apical four-chamber view was used to measure the left atrial superior and inferior diameter (LARDD) and left atrial left-right diameter (LALRD); mitral valve flow spectra were obtained to measure the early diastolic flow velocity E peak and late diastolic flow A peak velocity. Moreover, the pulmonary venous flow pattern was obtained, with the sample volume placed 0.5–1 cm from the entrance of the left atrium at the right upper pulmonary veins to measure the flow velocity of late diastolic reverse flow peak velocity of the right upper pulmonary vein (Ar) waves in pulmonary veins. Afterward, the “TDI” button was pressed to enter the tissue Doppler imaging mode, with tissue Doppler imaging utilized to record the early diastolic tissue velocity (e’) and late diastolic tissue velocity (a’) of the interventricular septum at the mitral annulus, followed by obtaining the early diastolic mitral peak velocity E peak to mitral annular tissue velocity e’ peak ratio (E/e’) ratio as an indicator of left ventricular filling pressure.

STI data analysis: after entering the QLAB 13.0 system, clear and complete images of each wall of the left atrium were selected, with each sampling point for SR imaging located on the interatrial septum and LA lateral wall, followed by sampling at the basal, middle, and apical segments to obtain SR curves for the corresponding segments of each wall. In the meantime, the peak strain rates (SRS, SRE, SRA) of each wall of the left atrium during left ventricular systole, early diastole, and LA systole were measured while simultaneously obtaining the peak global longitudinal strain rate (GLSR) during LA systole. Afterward, combined with synchronous recording of the electrocardiogram, the cardiac cycle was defined as the interval from the peak of one R wave to the peak of the next R wave on the ultrasound image, with the moment of aortic valve closure on the echocardiogram defined as end systole.

RT-3D data analysis: apical four-chamber view images at end-diastole were selected before entering the 3DQ mode, with sampling points placed on the LA wall. Afterward, the LA morphology was adjusted to divide the left atrium into 3 parts, followed by manually delineating each part to obtain the respective LA volumes and then calculating the minimum left atrial volume (LAVmin). With a similar method, images at the point just before the mitral valve opening were selected before entering the 3DQ mode, followed by analysis and calculation to obtain the maximum left atrial volume (LAVmax). Meanwhile, the left atrial presystolic volume (LAVp) was measured at the onset of the P wave on the electrocardiogram by electrocardiographic localization, through which the left atrial ejection fraction (LAEF), left atrial active ejection fraction (LAAEF), and left atrial passive ejection fraction (LAPEF) were calculated using the following formulas: Left Atrial Ejection Fraction (LAEF) = (LAVmax − LAVmin)/LAVmax; Left Atrial Active Ejection Fraction (LAAEF) = (LAVp − LAVmin)/LAVp; Left Atrial Passive Ejection Fraction (LAPEF) = (LAVmax − LAVp)/LAVmax.

Data Collection

Baseline data for both groups of subjects were collected: gender, age, BMI, heart rate, systolic blood pressure, and diastolic blood pressure. Baseline echocardiographic data: LAAPD, left atrial anterior-posterior diameter; LARDD, left atrial superior and inferior diameter; LALRD, left atrial left-right diameter; LVEDD, left ventricular end-diastolic diameter; LVESD, left ventricular end-systolic diameter; LVEDV, left ventricular end-diastolic volume; LVESV, left ventricular end-systolic volume; LVEF, left ventricular ejection fraction; E/A, early diastolic E peak velocity/late diastolic A peak velocity; e’, early diastolic tissue velocity of the interventricular septum; a’, late diastolic tissue velocity of the interventricular septum; E/e’, ratio of early diastolic mitral flow peak velocity E peak to tissue velocity e’ peak; Ar, late diastolic reverse flow peak velocity of the right upper pulmonary vein; LAVmin, minimum left atrial volume; LAVmax, maximum left atrial volume; LAEF, left atrial ejection fraction. STI data: peak strain rates (SRS, SRE, SRA) of each wall of the left atrium during left ventricular systole, early diastole, and LA systole, along with the peak GLSR obtained during LA systole.

Collection of 3DE data for the PAF group at 1, 3, and 6 months postoperatively: LAAPD, LARDD, LALRD, LAVmin, LAVmax, LAVp, LAEF, LAAEF, LAPEF. Collection of STI data for the PAF group at 1, 3, and 6 months postoperatively: Peak strain rates (SRS, SRE, SRA) of each wall of the left atrium during left ventricular systole, early diastole, and LA systole, along with the peak GLSR obtained during LA systole.

To assess intraobserver and interobserver variability, two independent observers performed the measurements on a subset of 10 randomly selected patients at two different times. The variability was quantified using the intraclass correlation coefficient, which provides a measure of the consistency and reproducibility of peak strain rates (SRS, SRE, SRA) and GLSR.

Statistical Analysis

SPSS 26.0 statistical software was used for the statistical analysis, the normality test was performed using the K-S method. Measurement data meeting normality were expressed as mean ± standard deviation (x±s), and independent sample t test was utilized. Count data were expressed as frequency (n) or rate (%), and χ2 test was used for eligible data, with Fisher exact probability method used for ineligibly data. Bilateral p < 0.05 was considered statistically significant.

General Data

Based on inclusion and exclusion criteria, the PAF (n = 50) and control groups (n = 36) were screened for echocardiographic evaluation. Six patients (12.0%) in the PAF group and 4 patients (11.1%) in the control group were excluded due to poor image quality, suggesting a high feasibility of echocardiography. Finally, the PAF group consisted of 44 patients (male = 31, female = 13), with the mean age of 50.67 ± 8.03 years and mean heart rate of 72.16 ± 11.18, and there were 32 patients in the control group (male = 20, female = 12), with the mean age of 45.33 ± 13.32 years and mean heart rate of 73.16 ± 11.83. No significant differences were observed in gender, age, BMI, heart rate, systolic blood pressure, and diastolic blood pressure between the 2 groups (p > 0.05) (see Table 1).

Table 1.

General data

ItemControl group (n = 32)PAF group (n = 44)t/χ2p value
Gender 20/12 31/13 0.531 0.466 
Age 45.33±13.32 50.67±8.03 0.832 0.409 
BMI 24.2817±4.11 25.97±3.28 0.983 0.330 
Heart rate 73.16±11.83 72.16±11.18 −0.714 0.478 
Systolic blood pressure 128.16±12.52 129.45±15.07 1.452 0.152 
Diastolic blood pressure 81.50±10.55 75.16±11.63 −0.624 0.535 
ItemControl group (n = 32)PAF group (n = 44)t/χ2p value
Gender 20/12 31/13 0.531 0.466 
Age 45.33±13.32 50.67±8.03 0.832 0.409 
BMI 24.2817±4.11 25.97±3.28 0.983 0.330 
Heart rate 73.16±11.83 72.16±11.18 −0.714 0.478 
Systolic blood pressure 128.16±12.52 129.45±15.07 1.452 0.152 
Diastolic blood pressure 81.50±10.55 75.16±11.63 −0.624 0.535 

BMI, body mass index.

Comparison of Echocardiographic Data

The findings indicated that LAAPD (32.00 ± 4.46 vs. 37.24 ± 4.64, t = −4.292, p < 0.001), LARDD (46.84 ± 6.93 vs. 51.46 ± 6.69, t = −3.367, p = 0.001), LALRD (34.87 ± 5.24 vs. 38.70 ± 4.89, t = −3.564, p = 0.001), LVEDD (45.03 ± 3.72 vs. 46.84 ± 4.23, t = −2.101, p = 0.039), LVESD (27.29 ± 3.73 vs. 30.00 ± 3.95, t = −3.059, p = 0.003), LAVmin (20.69 ± 9.11 vs. 27.84 ± 12.11, t = −2.947, p = 0.005), and LAVmax (44.11 ± 18.45 vs. 59.62 ± 20.21, t = −2.852, p = 0.006) in the control group were lower than those in the PAF group. In the meantime, LVEF (68.96 ± 5.76 vs. 64.57 ± 4.51, t = 3.464, p = 0.001), a’ (9.83 ± 1.59 vs. 8.86 ± 1.41, t = 3.138, p = 0.003), Ar (34.62 ± 9.47 vs. 29.38 ± 6.27, t = −3.227, p = 0.002), LAEF (61.26 ± 10.08 vs. 55.87 ± 8.24, t = 5.774, p < 0.001) in the control group were higher than those in the PAF group, as shown in Table 2.

Table 2.

Comparison of echocardiographic data

ItemControl group (n = 32)PAF group (n = 44)tp value
LAAPD (x±s), mm 32.00±4.46 37.24±4.64 −4.292 <0.001 
LARDD (x±s), mm 46.84±6.93 51.46±6.69 −3.367 0.001 
LALRD (x±s), mm 34.87±5.24 38.70±4.89 −3.564 0.001 
LVEDD (x±s), mm 45.03±3.72 46.84±4.23 −2.101 0.039 
LVESD (x±s), mm 27.29±3.73 30.00±3.95 −3.059 0.003 
LVEDV (x±s), mm 115.45±37.15 121.76±36.34 −0.617 0.539 
LVESV (x±s), mm 41.03±14.73 44.00±18.89 −0.615 0.541 
LVEF (x±s), % 68.96±5.76 64.57±4.51 3.464 0.001 
E/A (x±s) 1.45±1.01 1.07±0.43 1.169 0.246 
e’ (x±s), cm/s 7.48±1.60 6.76±1.77 1.566 0.122 
a’ (x±s), cm/s 9.83±1.59 8.86±1.41 3.138 0.003 
E/e’ (x±s) 9.75±3.10 11.53±3.38 −2.860 0.005 
Ar (x±s), cm/s 34.62±9.47 29.38±6.27 −3.227 0.002 
LAVmin (x±s), mL 20.69±9.11 27.84±12.11 −2.947 0.005 
LAVmax (x±s), mL 44.11±18.45 59.62±20.21 −2.852 0.006 
LAEF (x±s), % 61.26±10.08 55.87±8.24 5.774 <0.001 
ItemControl group (n = 32)PAF group (n = 44)tp value
LAAPD (x±s), mm 32.00±4.46 37.24±4.64 −4.292 <0.001 
LARDD (x±s), mm 46.84±6.93 51.46±6.69 −3.367 0.001 
LALRD (x±s), mm 34.87±5.24 38.70±4.89 −3.564 0.001 
LVEDD (x±s), mm 45.03±3.72 46.84±4.23 −2.101 0.039 
LVESD (x±s), mm 27.29±3.73 30.00±3.95 −3.059 0.003 
LVEDV (x±s), mm 115.45±37.15 121.76±36.34 −0.617 0.539 
LVESV (x±s), mm 41.03±14.73 44.00±18.89 −0.615 0.541 
LVEF (x±s), % 68.96±5.76 64.57±4.51 3.464 0.001 
E/A (x±s) 1.45±1.01 1.07±0.43 1.169 0.246 
e’ (x±s), cm/s 7.48±1.60 6.76±1.77 1.566 0.122 
a’ (x±s), cm/s 9.83±1.59 8.86±1.41 3.138 0.003 
E/e’ (x±s) 9.75±3.10 11.53±3.38 −2.860 0.005 
Ar (x±s), cm/s 34.62±9.47 29.38±6.27 −3.227 0.002 
LAVmin (x±s), mL 20.69±9.11 27.84±12.11 −2.947 0.005 
LAVmax (x±s), mL 44.11±18.45 59.62±20.21 −2.852 0.006 
LAEF (x±s), % 61.26±10.08 55.87±8.24 5.774 <0.001 

LAAPD, anteroposterior diameter of left atrium; LARDD, supero-inferior diameter of left atrium; LALRD, left and right diameters of left atrium; LVEDD, left ventricular end-diastolic diameter; LVESD, left ventricular end-systolic diameter; LVEDV, left ventricular end-diastolic volume; LVESV, left ventricular end-systolic volume; LVEF, left ventricular ejection fraction; E/A, early diastolic E peak-to-peak velocity/late diastolic A peak-to-peak velocity; e’, left ventricular early diastolic mitral annular interventricular septal tissue velocity; a’, left ventricular late diastolic mitral annular interventricular septal tissue velocity; E/e’, early diastolic mitral peak velocity E peak to mitral annular tissue velocity e’ peak ratio; Ar, late diastolic right superior pulmonary vein peak reverse flow velocity; LAVmin, left atrial minimum volume; LAVmax, left atrial maximum volume; LAEF, left atrial ejection fraction.

Comparison of Global and 6-Segment SR Parameters in the Left Atrium

The intraobserver coefficients of SRS, SRE, SRA, GLSRS, GLSRE, and GLSRA were 0.948, 0.948, 0.993, 0.901, 0.983, and 0.976, respectively. The interobserver coefficients of SRS, SRE, SRA, GLSRS, GLSRE, and GLSRA were 0.886, 0.943, 0.990, 0.861, 0.987, and 0.995, respectively. The findings revealed that in the control group, SRS of the lateral basal (1.89 ± 0.37 vs. 1.48 ± 0.36, t = −5.032, p < 0.001), lateral mid (1.64 ± 0.38 vs. 1.39 ± 0.31, t = −7.403, p < 0.001), septal basal (1.83 ± 0.36 vs. 1.60 ± 0.38, t = 2.871, p = 0.006), and septal mid (1.55 ± 0.38 vs. 1.27 ± 0.31, t = −3.124, p = 0.002) segments, GLSRS (1.82 ± 0.42 vs. 1.49 ± 0.34, t = −2.918, p = 0.015), SRE (−1.77 ± 0.42 vs. −1.35 ± 0.35, t = −2.921, p = 0.003), and SRA (−1.65 ± 0.32 vs. −1.41 ± 0.31, t = −4.674, p < 0.001) of the lateral basal segments, SRE (−1.49 ± 0.34 vs. −1.26 ± 0.32, t = −7.732, p < 0.001) and SRA (−1.46 ± 0.41 vs. −1.14 ± 0.40, t = 3.522, p = 0.001) of the lateral mid segments, SRE (−1.57 ± 0.38 vs. −1.23 ± 0.35, t = −3.482, p < 0.001) and SRA (−1.77 ± 0.42 vs. −1.24 ± 0.42, t = 3.268, p = 0.002) of the septal basal segments, SRE (−1.48 ± 0.37 vs. −1.28 ± 0.30, t = −3.682, p < 0.001) and SRA (−1.65 ± 0.43 vs. −1.31 ± 0.40, t = −2.662, p = 0.011) of the septal mid segments, GLSRE (−1.68 ± 0.41 vs. −1.28 ± 0.32, t = −2.757, p = 0.016) and GLSRA (−1.59 ± 0.43 vs. −1.30 ± 0.32, t = 6.193, p < 0.001) were higher than those in the PAF group (see Table 3).

Table 3.

Comparison of global and 6-segment strain rate parameters in the left atrium

Sampling sectionParameterControl group (n = 32)PAF group (n = 44)tp value
Lateral basal SRS 1.89±0.37 1.48±0.36 −5.032 <0.001 
SRE −1.77±0.42 −1.35±0.35 −2.921 0.003 
SRA −1.65±0.32 −1.41±0.31 −4.674 <0.001 
Lateral mid SRS 1.64±0.38 1.39±0.31 −7.403 <0.001 
SRE −1.49±0.34 −1.26±0.32 −7.732 <0.001 
SRA −1.46±0.41 −1.14±0.40 3.522 0.001 
Lateral roof SRS 1.58±0.33 1.53±0.32 −0.561 0.570 
SRE −1.38±0.31 −1.29±0.28 −0.309 0.760 
SRA −1.41±0.42 −1.39±0.41 −0.103 0.918 
Septal basal SRS 1.83±0.36 1.60±0.38 2.871 0.006 
SRE −1.57±0.38 −1.23±0.35 −3.482 <0.001 
SRA −1.77±0.42 −1.24±0.42 3.268 0.002 
Septal mid SRS 1.55±0.38 1.27±0.31 −3.124 0.002 
SRE −1.48±0.37 −1.28±0.30 −3.682 <0.001 
SRA −1.65±0.43 −1.31±0.40 −2.662 0.011 
Septal roof SRS 1.61±0.39 1.59±0.30 −0.635 0.528 
SRE −1.42±0.33 −1.38±0.27 1.842 0.071 
SRA −1.62±0.45 −1.46±0.38 1.150 0.256 
GLSRS 1.82±0.42 1.49±0.34 −2.918 0.015 
GLSRE −1.68±0.41 −1.28±0.32 −2.757 0.016 
GLSRA −1.59±0.43 −1.30±0.32 6.193 <0.001 
Sampling sectionParameterControl group (n = 32)PAF group (n = 44)tp value
Lateral basal SRS 1.89±0.37 1.48±0.36 −5.032 <0.001 
SRE −1.77±0.42 −1.35±0.35 −2.921 0.003 
SRA −1.65±0.32 −1.41±0.31 −4.674 <0.001 
Lateral mid SRS 1.64±0.38 1.39±0.31 −7.403 <0.001 
SRE −1.49±0.34 −1.26±0.32 −7.732 <0.001 
SRA −1.46±0.41 −1.14±0.40 3.522 0.001 
Lateral roof SRS 1.58±0.33 1.53±0.32 −0.561 0.570 
SRE −1.38±0.31 −1.29±0.28 −0.309 0.760 
SRA −1.41±0.42 −1.39±0.41 −0.103 0.918 
Septal basal SRS 1.83±0.36 1.60±0.38 2.871 0.006 
SRE −1.57±0.38 −1.23±0.35 −3.482 <0.001 
SRA −1.77±0.42 −1.24±0.42 3.268 0.002 
Septal mid SRS 1.55±0.38 1.27±0.31 −3.124 0.002 
SRE −1.48±0.37 −1.28±0.30 −3.682 <0.001 
SRA −1.65±0.43 −1.31±0.40 −2.662 0.011 
Septal roof SRS 1.61±0.39 1.59±0.30 −0.635 0.528 
SRE −1.42±0.33 −1.38±0.27 1.842 0.071 
SRA −1.62±0.45 −1.46±0.38 1.150 0.256 
GLSRS 1.82±0.42 1.49±0.34 −2.918 0.015 
GLSRE −1.68±0.41 −1.28±0.32 −2.757 0.016 
GLSRA −1.59±0.43 −1.30±0.32 6.193 <0.001 

SRS, left ventricular peak systolic strain rate; SRE, left ventricular early diastolic peak strain rate; SRA, left atrial peak systolic strain rate; GLSRS, left ventricular systolic left atrial global peak strain rate; GLSRE, left ventricular early diastolic left atrial global peak strain rate; GLSRA, left atrial global peak systolic strain rate.

Comparison of LA Structure and RT-3DE Functional Parameters Pre- and Post-Radiofrequency Ablation in the PAF Group

Meanwhile, the findings suggested that compared with preoperative values, patients exhibited elevated LVEF at 1, 3, and 6 months postoperatively, as well as increased LAPEF and LAAEF at 6 months postoperatively (p < 0.05). In addition, LAAPD, LALRD, and LAVp at 6 months postoperatively were lower than preoperative values (p < 0.05). Moreover, LAAPD, LALRD, LAVmin, LAVmax, and LAVp were decreased at 6 months postoperatively compared with values at 1 month postoperatively (p < 0.05). Furthermore, LVEF and LAAEF were higher at 6 months postoperatively than those at 1 month postoperatively (p < 0.05) (see Table 4).

Table 4.

Comparison of left atrial structure and RT-3DE functional parameters pre- and post-radiofrequency ablation in the PAF group

ItemPreoperativePostoperative 1 monthPostoperative 3 monthsPostoperative 6 months
LAAPD (x±s), mm 38.32±4.58 38.03±4.76 35.73±4.18 34.79±4.03a,b 
LARDD (x±s), mm 51.70±6.50 51.71±8.38 51.25±7.06 51.52±6.96 
LALRD (x±s), mm 39.03±4.88 39.42±4.25 38.40±5.72 35.48±5.84a,b 
LAVmin (x±s), mL 29.27±17.02 30.05±11.14 28.55±11.61 23.58±11.94a,b 
LAVmax (x±s), mL 68.81±21.53 70.53±19.12 66.25±16.88 59.18±19.40a,b 
LAVp (x±s), mL 38.39±15.11 37.98±14.32 35.22±8.11 30.02±9.11a,b 
LAEF (x±s), % 59.11±12.60 57.71±12.34 58.95±9.81 60.85±12.80 
LVEF (x±s), % 64.92±4.66 69.83±6.12a 72.32±5.20a 74.34±5.31a,b 
LAAEF (x±s), % 34.03±10.86 37.05±9.06 40.12±8.65 43.48±12.72a,b 
LAPEF (x±s), % 0.36±0.11 0.40±0.13 0.41±0.21 0.43±0.12a 
ItemPreoperativePostoperative 1 monthPostoperative 3 monthsPostoperative 6 months
LAAPD (x±s), mm 38.32±4.58 38.03±4.76 35.73±4.18 34.79±4.03a,b 
LARDD (x±s), mm 51.70±6.50 51.71±8.38 51.25±7.06 51.52±6.96 
LALRD (x±s), mm 39.03±4.88 39.42±4.25 38.40±5.72 35.48±5.84a,b 
LAVmin (x±s), mL 29.27±17.02 30.05±11.14 28.55±11.61 23.58±11.94a,b 
LAVmax (x±s), mL 68.81±21.53 70.53±19.12 66.25±16.88 59.18±19.40a,b 
LAVp (x±s), mL 38.39±15.11 37.98±14.32 35.22±8.11 30.02±9.11a,b 
LAEF (x±s), % 59.11±12.60 57.71±12.34 58.95±9.81 60.85±12.80 
LVEF (x±s), % 64.92±4.66 69.83±6.12a 72.32±5.20a 74.34±5.31a,b 
LAAEF (x±s), % 34.03±10.86 37.05±9.06 40.12±8.65 43.48±12.72a,b 
LAPEF (x±s), % 0.36±0.11 0.40±0.13 0.41±0.21 0.43±0.12a 

LAAPD, left atrial anteroposterior diameter; LARDD, left atrial superior and inferior diameter; LALRD, left atrial left and right diameters; LVEF, left ventricular ejection fraction; LAVp, left atrial presystolic volume; LAAEF, left atrial active ejection fraction; LAPEF, left atrial passive ejection fraction; LAVmin, left atrium minimum volume; LAVmax, left atrial maximum volume; LAEF, left atrial ejection fraction.

ap < 0.05 compared with that before operation.

bp < 0.05 compared with that at 1 month after operation.

Comparison of Global and 6-Segment SR Parameters of the Left Atrium Pre- and Post-Operation

Besides, the findings also showed no significant changes in all indicators at 1 month postoperatively compared with preoperative values. Compared with values pre-operation and at 1 month postoperatively, the SRE and SRA of the lateral basal segments, SRE and SRS of lateral mid segments, SRS, SRE, and SRA of the septal basal segments, and SRS of the septal mid segments were all elevated at 3 months postoperatively. At the same time, the SRS, SRE, and SRA of the lateral basal segments; SRE and SRS of the lateral mid segments; SRS, SRE, and SRA of the septal basal segments; SRA and SRS of the septal mid segments; GLSRS, GLSRE, and GLSRA at 6 months postoperatively were all higher than values pre-operation and at 1 month postoperatively. Additionally, the SRE and SRS of the lateral basal segments and the SRS of the septal basal segments at 6 months postoperatively were elevated compared with the values at 3 months postoperatively (see Table 5).

Table 5.

Comparison of global and 6-segment strain rate parameters of the left atrium pre- and post-operation

Sampling sectionParameterPreoperativePostoperative 1 monthPostoperative 3 monthsPostoperative 6 months
Lateral basal SRS 1.47±0.37 1.42±0.41 1.52±0.34 1.78±0.42a,b,c 
SRE −1.36±0.34 −1.35±0.35 −1.45±0.52 a,b −1.67±0.45 a,b,c 
SRA −1.39±0.33 −1.40±0.37 −1.61±0.43 a,b −1.63±0.41 a,b 
Lateral mid SRS 1.35±0.34 1.34±0.33 1.44±0.34a,b 1.57±0.40a,b 
SRE −1.23±0.32 −1.22±0.31 −1.32±0.41a,b −1.43±0.35a,b 
SRA −1.18±0.28 −1.26±0.40 −1.30±0.40 −1.39±0.41a 
Lateral roof SRS 1.55±0.33 1.53±0.32 1.54±0.42 1.58±0.40 
SRE −1.30±0.31 −1.31±0.28 −1.32±0.31 −1.33±0.32 
SRA −1.40±0.42 −1.39±0.41 −1.40±0.31 −1.43±0.29 
Septal basal SRS 1.57±0.39 1.58±0.37 1.68±0.41a,b 1.89±0.42a,b,c 
SRE −1.28±0.36 −1.23±0.35 −1.43±0.33a,b −1.58±0.39a,b 
SRA −1.27±0.33 −1.26±0.34 −1.36±0.35a,b −1.49±0.40a,b 
Septal mid SRS 1.28±0.33 1.27±0.31 1.37±0.24a,b 1.49±0.38a,b 
SRE −1.32±0.33 −1.31±0.30 −1.34±0.32 −1.38±0.34 
SRA −1.28±0.35 −1.26±0.32 −1.36±0.34 −1.51±0.43a,b 
Septal roof SRS 1.61±0.34 1.59±0.35 1.60±0.37 1.62±0.40 
SRE −1.41±0.29 −1.38±0.29 −1.39±0.34 −1.42±0.32 
SRA −1.50±0.39 −1.48±0.38 −1.50±0.41 −1.54±0.37 
GLSRS 1.45±0.35 1.43±0.34 1.53±0.32 1.75±0.41a,b 
GLSRE −1.29±0.37 −1.28±0.32 −1.41±0.54 −1.59±0.38a,b 
GLSRA −1.36±0.36 −1.30±0.33 −1.42±0.37 −1.55±0.39a,b 
Sampling sectionParameterPreoperativePostoperative 1 monthPostoperative 3 monthsPostoperative 6 months
Lateral basal SRS 1.47±0.37 1.42±0.41 1.52±0.34 1.78±0.42a,b,c 
SRE −1.36±0.34 −1.35±0.35 −1.45±0.52 a,b −1.67±0.45 a,b,c 
SRA −1.39±0.33 −1.40±0.37 −1.61±0.43 a,b −1.63±0.41 a,b 
Lateral mid SRS 1.35±0.34 1.34±0.33 1.44±0.34a,b 1.57±0.40a,b 
SRE −1.23±0.32 −1.22±0.31 −1.32±0.41a,b −1.43±0.35a,b 
SRA −1.18±0.28 −1.26±0.40 −1.30±0.40 −1.39±0.41a 
Lateral roof SRS 1.55±0.33 1.53±0.32 1.54±0.42 1.58±0.40 
SRE −1.30±0.31 −1.31±0.28 −1.32±0.31 −1.33±0.32 
SRA −1.40±0.42 −1.39±0.41 −1.40±0.31 −1.43±0.29 
Septal basal SRS 1.57±0.39 1.58±0.37 1.68±0.41a,b 1.89±0.42a,b,c 
SRE −1.28±0.36 −1.23±0.35 −1.43±0.33a,b −1.58±0.39a,b 
SRA −1.27±0.33 −1.26±0.34 −1.36±0.35a,b −1.49±0.40a,b 
Septal mid SRS 1.28±0.33 1.27±0.31 1.37±0.24a,b 1.49±0.38a,b 
SRE −1.32±0.33 −1.31±0.30 −1.34±0.32 −1.38±0.34 
SRA −1.28±0.35 −1.26±0.32 −1.36±0.34 −1.51±0.43a,b 
Septal roof SRS 1.61±0.34 1.59±0.35 1.60±0.37 1.62±0.40 
SRE −1.41±0.29 −1.38±0.29 −1.39±0.34 −1.42±0.32 
SRA −1.50±0.39 −1.48±0.38 −1.50±0.41 −1.54±0.37 
GLSRS 1.45±0.35 1.43±0.34 1.53±0.32 1.75±0.41a,b 
GLSRE −1.29±0.37 −1.28±0.32 −1.41±0.54 −1.59±0.38a,b 
GLSRA −1.36±0.36 −1.30±0.33 −1.42±0.37 −1.55±0.39a,b 

SRS, left ventricular peak systolic strain rate; SRE, left ventricular early diastolic peak strain rate; SRA, left atrial peak systolic strain rate; GLSRS, left ventricular systolic left atrial global peak strain rate; GLSRE, left ventricular early diastolic left atrial global peak strain rate; GLSRA, left atrial global peak systolic strain rate.

ap < 0.05 compared with that before operation.

bp < 0.05 compared with that at 1 month after operation.

cp < 0.05 compared with that at 3 months after operation.

The causal relationship between AF and the left atrium has long been a topic of debate, but the current theory of “atrial remodeling” provides a reasonable explanation for the occurrence, development, and maintenance of AF. Specifically, atrial remodeling mainly includes structural remodeling, electrical remodeling, and neural remodeling of the atria [17]. Structural remodeling of the left atrium is mainly characterized by LA enlargement, accompanied by changes in ultrastructure such as increased cardiomyocyte volume, atrial fibrosis, and abnormal expression of atrial gap-junction proteins [18]. Once enlarged, the left atrium can accommodate more reentrant waves, thereby facilitating and sustaining the occurrence and development of AF. Therefore, AF and LA structural remodeling are causally related and interconnected. In recent years, it has been found that successful radiofrequency ablation depends on the status of preoperative LA structural remodeling [19]. Therefore, prompt and comprehensive assessment of the structure and function of the left atrium before and after ablation in PAF patients is of great significance for guiding early clinical treatment and prognosis assessment. The novelty of our study lies in the combined use of 2D-STI and RT-3DE to provide a more comprehensive evaluation of LA structural and functional changes post-RFCA. Previous studies have highlighted the value of LA strain in post-RFCA patients; however, our study uniquely integrates both 2D and 3D echocardiographic techniques to assess LA dimensions, volumes, ejection fraction, and SRs over multiple time points (1, 3, and 6 months). This approach offers a more detailed and dynamic understanding of the LA remodeling process and its recovery trajectory post-ablation. By comparing our results with an age- and gender-matched control group, we were able to delineate the specific changes attributable to RFCA, thus providing new insights into the utility of advanced echocardiographic methods in the management and prognosis of PAF patients. Currently, echocardiography has become the preferred approach for evaluating LA structural remodeling and reverse remodeling due to its advantages of real-time convenience, noninvasiveness, and repeatability.

Myocardial strain (S) refers to the deformation of myocardial tissue under external forces [20], expressed as a percentage (%) of changes in myocardial length, with positive values indicating myocardial elongation or wall thickening and negative values indicating myocardial shortening or wall thinning. In the meantime, myocardial SR refers to the speed at which myocardial tissue deforms, based on the velocity of myocardial tissue in the direction of the ultrasound beam. 2D-STI tracks and analyzes high-frame-rate myocardial echo speckles using 2D echocardiography, in which each tracked speckle can change its position with the movement of surrounding myocardial tissue, and the movement and deformation of myocardial tissue within the entire region of interest can be tracked in real-time by identifying these acoustic speckles. This technique can evaluate strain and SR in any direction on a 2D image [21], providing a mechanical assessment of myocardial contraction and relaxation function and quantifying parameters such as displacement, velocity, and strain of myocardial motion, with unique advantages [22] due to its lack of angle dependency. Studies abroad on LA wall strain have shown [23] that quantitative evaluation of deformation in the longitudinal direction of atrial muscle with STI is feasible and can enhance understanding of the pathophysiological processes of the left atrium. In addition, Kim et al. [24] have demonstrated that assessing atrial function using atrial muscle strain and SR is feasible, accurate, and highly repeatable. RT-3DE is a relatively novel ultrasound technique that allows for easy operation, rapid imaging, real-time 3D visualization of the spatial structure, adjacent relationships, and dynamic activities of the heart without relying on assumptions about cardiac chamber geometry, enabling it to accurately measure cardiac volume and function. Moreover, studies at home and abroad have shown that RT-3DE can accurately measure cardiac structure and function [25].

Regarding the pathophysiology, it is crucial to understand the relationship between LA dysfunction and LV diastolic dysfunction, as well as the interplay between LA reservoir function and conduit function. LA dysfunction can contribute to LV diastolic dysfunction due to the impaired ability of the LA to act as a reservoir and conduit during the cardiac cycle [26]. The reservoir function of the LA refers to its capacity to store blood during LV systole, while the conduit function pertains to the passive transfer of blood from the LA to the LV during early diastole. When the LA reservoir function is compromised, it can lead to reduced LV filling and increased LV filling pressures, exacerbating LV diastolic dysfunction. Conversely, improved LA function post-ablation can enhance LV filling dynamics and potentially ameliorate diastolic dysfunction. The assessment of LA strain and SR through advanced imaging techniques such as 2D-STI and RT-3DE provides valuable insights into these functional interactions and their impact on overall cardiac performance.

According to the literature, PAF patients exhibit enlarged left atria and weakened atrial pump function, which is related to the frequency and duration of AF occurrences [27], consistent with the findings of this study. Preoperatively, patients in the PAF group had an enlarged LA diameter and decreased LAEF, E/e’, and Ar wave velocity, indicating that the LA reservoir and booster pump function in PAF patients were significantly affected. Additionally, due to the lack of coordination in atrial contraction during AF, the late diastolic contraction function was compromised, which led to increased volume load and subsequent enlargement of the left atrium, ultimately resulting in atrial fibrosis and structural remodeling of the left atrium in AF patients. In this study, patients in the sinus rhythm group who successfully maintained sinus rhythm at 6 months postoperatively showed a significant reduction in LA diameter, along with decreased LAVmin, LAVp, and LAVmax, indicating an increased LAAEF and LAPEF of LA booster pump function and conduit function. This demonstrated that the LA booster pump function and conduit function improved in patients at 6 months postoperatively.

Understanding the relationship between LA strain and volume is crucial for interpreting these changes in atrial function. LA strain provides insight into the deformation of atrial myocardial tissue, while LA volume reflects the overall size and capacity of the atrium. The role of LAVmin compared to LAVmax is particularly relevant, as LAVmin is directly influenced by LV diastolic pressure and serves as a better correlate of LV diastolic function than LAVmax. Studies have shown that LAVmin is significantly associated with LV diastolic function parameters and is a stronger predictor of diastolic dysfunction compared to LAVmax [28]. Additionally, LA expansion index, which considers both LAVmin and LAVmax, has been shown to predict AF and inhospital mortality following coronary artery bypass graft surgery [29]. Furthermore, bi-atrial function assessed by 2D and 3D speckle tracking echocardiography can stratify the risk of PAF in patients with atrial septal devices [30]. Incorporating these parameters into the assessment of LA function provides a comprehensive evaluation and aids in understanding the pathophysiological processes involved in atrial remodeling.

The value of the combined assessment of LA strain and volume in predicting PAF is noteworthy. Recent studies have highlighted the importance of integrating LA strain and volume measurements for a more comprehensive evaluation of atrial function. Specifically, the combination of these parameters has been shown to enhance the prediction of PAF development [31]. The integration of speckle tracking echocardiography with traditional volumetric assessments provides a detailed understanding of both the mechanical and volumetric aspects of atrial function. This combined approach allows for the identification of subtle changes in atrial mechanics that may precede the onset of PAF, thus offering a valuable tool for early intervention and management. The study by Tarsia et al. [32] demonstrated that patients who underwent occluder implantation had significantly worse strain indices and different minimal volumes compared with baseline at 1-year follow-up, underscoring the relevance of these combined metrics in clinical practice. Therefore, the inclusion of LA strain and volume assessments in the routine evaluation of patients at risk for PAF can improve predictive accuracy and guide therapeutic strategies.

LA myocardial fibrosis is the foundation for the occurrence, development, and persistence of AF, and the 2D-STI technique can accurately assess the mechanical function of the left atrium by quantitatively evaluating LA longitudinal strain and SR, thereby assessing the severity of LA fibrosis [33]. This study revealed that PAF patients exhibited varying degrees of reduction in preoperative SRS, SRE, and SRA in the basal and mid segments of the LA lateral wall, as well as in the basal and mid segments of the interatrial septum compared with the control group. According to Inaba et al. [34], on the SR curve of the left atrium, SRS, SRE, and SRA refer to reservoir, conduit, and booster pump functions, respectively, and it was concluded in this study that in PAF patients, the reservoir, conduit, and booster pump functions in the basal and mid segments of the left atrium were impaired, consistent with related research results [35]. Therefore, LA longitudinal strain and SR are independent and stable predictive indicators for evaluating LA fibrosis [36]. In addition, this study showed that in the sinus rhythm group, there was little change in SR parameters of various segments of the left atrium at 1 month postoperatively compared with preoperative values. At 6 months postoperatively, however, except for segments at the apex, SRS, SRE, and SRA increased in other segments, with more significant changes in SRS and SRA representing reservoir and booster pump functions, which also indicated reverse remodeling of the left atrium after successful restoration of sinus rhythm.

The findings of this study have significant clinical implications for the management and prediction of PAF. The observed changes in LA strain and volume provide valuable insights into the pathophysiology of atrial remodeling in PAF patients. Preoperative reductions in LA strain and SR, particularly in the basal and mid segments of the LA lateral wall and interatrial septum, indicate impaired atrial reservoir, conduit, and booster pump functions. These functional impairments are associated with the development and persistence of PAF [37]. Therefore, early assessment of LA strain and volume can help identify patients at higher risk for PAF, allowing for targeted interventions. Additionally, the study highlights the potential benefits of monitoring LA function postoperatively. The improvement in strain parameters and LA function observed in patients who maintained sinus rhythm at 6 months suggests that successful rhythm restoration can reverse some of the atrial remodeling associated with PAF. This underscores the importance of effective rhythm control strategies and follow-up assessments in managing PAF. Incorporating detailed LA function evaluations into routine clinical practice can enhance predictive accuracy and guide therapeutic decisions [38]. Specifically, integrating LA strain and volumetric assessments can aid in identifying patients who may benefit from more aggressive treatment strategies or closer monitoring. This approach may ultimately improve patient outcomes by facilitating early intervention and personalized management plans for those at risk of PAF.

However, this study also comes with certain limitations: (1). the sample size was small, which should be expanded for further research. (2). The follow-up period was only 6 months, which currently demonstrates trends of change, but an extended follow-up period could provide more reliable prognostic value for clinical practice. (3). The study did not utilize 3D strain imaging, which could offer more detailed insights into LA function. 3D strain imaging allows for a comprehensive assessment of atrial deformation and may provide additional information on the spatial distribution of atrial strain, potentially improving the accuracy of our findings. The inclusion of 3D strain data in future research could enhance our understanding of atrial remodeling and its implications for predicting and managing AF.

The application of 2D-STI and 3D imaging techniques can quantitatively analyze the LA structure and function before and after radiofrequency ablation in PAF patients. Additionally, PAF patients demonstrate enlarged LA diameter and volume, decreased SR in various segments and overall, and varying degrees of impairment in reservoir, conduit, and booster pump functions. Furthermore, AF patients after radiofrequency ablation experience reverse remodeling of the left atrium, with improved structure and function.

This study was conducted in accordance with the Declaration of Helsinki and approved by the Research Ethics Committee of Beijing Anzhen Hospital, Approval No. 2024098X. Due to the nature of retrospective study and anonymized patient’s information, informed consent is waived with the approval of Ethics Committee of Beijing Anzhen Hospital. All methods were carried out in accordance with relevant guidelines and regulations.

The authors have no conflicts of interest to declare.

This work was supported by Beijing JST Research Funding (code: ZR-202212) from Beijing Jishuitan Hospital. The funder had no role in the design, data collection, data analysis, and reporting of this study.

Study design, data acquisition, and manuscript review: H.R., M.-Y.C., L.-H.W., L.-R.J., H.-Y.H., W.-Z.F., and W.-Y.Q. Data analysis and interpretation: M.-Y.C., L.-H.W., L.-R.J., H.-Y.H., and W.-Z.F. Manuscript preparation: H.R., M.-Y.C., L.-H.W., L.-R.J., H.-Y.H., and W.-Z.F. Critical revision of the manuscript for intellectual content and obtaining financing: W.-Y.Q.

The data that support the findings of this study are not publicly available due to the privacy of research participants but are available from the corresponding author:

W.-Y.Q., wu35yongquan02@126.com and wuyongquan67@163.com.

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