Introduction

Atrial fibrillation (AF), the most prevalent cardiac arrhythmia, has emerged as a global health challenge. AF not only impairs patients’ quality of life but also significantly heightens the risks of stroke, heart failure, and all-cause mortality1. Left atrial (LA) remodeling, involving both structural and functional changes, plays a crucial role in the onset and persistence of AF2. Even in patients with preserved left ventricular ejection fraction, AF-induced electrical and mechanical dyssynchrony can cause progressive LA dilation, fibrosis, and weakened contractility3. These alterations disrupt the normal atrial filling and emptying, further exacerbating the arrhythmia. Catheter ablation has become an effective treatment for restoring and maintaining sinus rhythm in AF patients. While many studies have shown its clinical effectiveness, the post-ablation temporal dynamics of LA reverse remodeling remain unclear. Understanding these dynamics is vital as it can offer insights into arrhythmia recurrence mechanisms and guide personalized management. Recent advancements in echocardiography, especially two-dimensional speckle-tracking imaging (2D-STI), have transformed the assessment of LA mechanics. As demonstrated in research published in JACC Cardiovascular Imaging, 2D-STI can precisely quantify LA strain and strain rate, detecting subtle atrial function changes4. There is a lack of longitudinal data on the post-ablation recovery p.a. tterns of LA stiffness and strain. Existing studies mainly focus on short-term outcomes or single-time point assessments, failing to capture the dynamic nature of LA remodeling over time5. This prospective study aims to using multi-parametric echocardiography to systematically evaluate the dynamic changes in LA structure, function, and stiffness in paroxysmal AF patients with preserved LVEF, we aim to reveal the characteristic patterns of LA reverse remodeling, identify predictors of arrhythmia recurrence, and provide evidence-based suggestions for post-ablation clinical follow-up.

Data and Methods

General information

Objects

This study enrolled 89 patients with paroxysmal atrial fibrillation (PAF) who underwent catheter ablation at our hospital from March 2023 to April 2024. Of these patients, 42 were male and 47 were female, with a mean age of 59.48 ± 8.91 years. Clinical data of patients were collected, and informed consent was obtained from all participants. All patients completed the full follow-up schedule, with no missing data.

Inclusion criteria

(1) Patients with a confirmed diagnosis of PAF (meeting the ESC/HRS guideline6 criteria, with atrial fibrillation episodes lasting < 7 days and terminating spontaneously); (2) Patients with a left ventricular ejection fraction (LVEF) of ≥ 50% and no structural heart disease (e.g., hypertrophic cardiomyopathy, moderate or severe valvular disease); (3) Patients scheduled for first-time radiofrequency ablation (pulmonary vein isolation); (4) Patients aged 18–80 years who had signed an informed consent document.

Exclusion criteria

(1) Patients with valvular heart disease or those who have undergone valve replacement procedure; (2) Patients with a history of atrial fibrillation ablation; (3) Patients with congenital heart disease; (4) Patients showing thrombosis in the atrium or auricle during transesophageal echocardiography; (5) Patients with hyperthyroidism.

Instruments and Examination Methods

Instrument: The Philips EPIQ7C ultrasound diagnostic device was used, with a transthoracic ultrasound probe model X5-1, frequency between 1 and 5 MHz, and a probe depth of 15–20 mm. The quantitative analysis software was QLAB10.5. Patients were positioned on the examination bed in the left lateral decubitus position and instructed to breathe calmly. Before the examination, limb lead electrocardiography was connected, and continuously collecting and storing clear dynamic images of three cardiac cycles for subsequent offline analysis. The patients’ height and weight were recorded, and input into the ultrasound diagnostic instrument, and the system automatically calculated the body surface area (BSA).

Two - dimensional echocardiography

In the parasternal long - axis view of the left ventricle, left atrial diameter (LAD) and left ventricular ejection fraction (LVEF) were measured. In the apical four-chamber view, left atrial appendage flow velocity (LAA-v) and the mitral valve early diastolic peak velocity (E peak) were measured. Also, in this view, Simpson’s method was used to measure the left atrial end - diastolic volume (LAEDV), left atrial end - systolic volume (LAESV) (Fig. 1), left atrial presystolic volume (LAVp), and left atrial ejection fraction (LAEF).

Fig. 1
figure 1

Left atrial end-diastolic volume (A) and left atrial end-systolic volume (B) before catheter ablation; Left atrial end-diastolic volume (C) and left atrial end-systolic volume (D) three months after catheter ablation.

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Calculated the:

Left atrial active ejection fraction (LAAEF): LAAEF=(LAVp-LAESV)/LAVp×100%.

Left atrial passive ejection fraction (LAPEF): LAPEF=(LAEDV-LAVp)/LAEDV×100%.

Left atrial volume index (LAVI): LAVI = LAEDV/BSA.

2D-STI

Acquired standard two - chamber and four - chamber views in the apical long-axis position, saving three consecutive cardiac cycles for each. Opened the QLAB10.5 quantitative analysis software, entered the aCMQ mode, selected TMAD, and imported the saved images. Placed fixed points at the left atrial apex and both sides of the mitral valve annulus. The system generated left atrial myocardial segmental strain curves. If the endocardium was unclear or incomplete, manually adjusted the fixed points until the endocardium was clearly displayed. Then, the peak left atrial systolic strain (LASRs), peak left atrial systolic strain rate (mLASRs), peak early left atrial diastolic strain (LASRe), peak early left atrial diastolic strain rate (mLASRe), peak late left atrial diastolic strain (LASRa) and late left atrial diastolic strain rate (mLASRa) were obtained, and data analysis was performed after getting the average values. This study takes the QRS wave of the electrocardiogram as the starting point, thus LASRs and mLASRs are positive values, while LASRe, mLASRe, LASRa, and mLASRa are negative values (Fig. 2).

Fig. 2
figure 2

left atrial strain (A) and strain rate (B) in the apical four-chamber view before catheter ablation; Left atrial strain (C) and strain rate (D) in the apical four-chamber view three months after catheter ablation.

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TDI: In the apical four-chamber view, activated the TDI mode, placed the sampling points sequentially at the left atrial side and septal side of the mitral valve annulus. The early diastolic peak velocity of the septal side of the mitral valve annulus (septal e’) and the early diastolic velocity of the left atrial side of the mitral valve annulus (left atrial e’) were measure, then calculated the average value to get the early diastolic peak velocity of the mitral valve annulus (e’), and calculated the left atrial stiffness (LASt) using the formula: LASt = (E/e’)/LASRs.

Ablation Procedure

During the procedure, a coronary sinus electrode catheter was inserted into the coronary sinus via the patient’s internal jugular vein or left femoral vein, then a guidewire was placed in the superior vena cava through the right femoral vein, followed by the placement of a sheath over the guidewire, and a puncture needle was then inserted through the sheath for atrial septal puncture. Heparin was administered at a dose of 100 IU/kg during the procedure. The Pentaray multipolar mapping catheter was advanced into the left atrium via the sheath. Under the guidance of the CARTO 3D electrophysiological mapping system, structural reconstruction of the left atrium and bilateral pulmonary veins was performed. The radiofrequency output power was set at 35–40 W, and the radiofrequency generator temperature at 43℃ for ablation. The target was to achieve pulmonary vein isolation, with ablation duration adjusted based on tissue contact and impedance changes6.

Statistical analysis

Data analysis was performed using SPSS 26.0. Count data were presented as cases or percentages and analyzed using the chi-square test. Normally distributed measurement data were expressed as mean ± standard deviation (¯X ± S) and compared using the t-test. Non-normally distributed data were presented as median (interquartile range) and analyzed using the rank - sum test. P < 0.05 was considered statistically significant. To assess the predictive value of LA parameters for AF recurrence, a Cox proportional hazards model was used, with clinical follow-up for 12 months post-ablation.

Results

General information of patients

This study included 89 patients, with an average age of 59.48 ± 8.91 years, including 42 males, accounting for 47.19% (Table 1).

Table 1 Baseline data of patients.
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Comparison of left atrial structure and function parameters before and after catheter ablation procedure

One day after ablation, LVEF, LASRs, LASRe, LASRa, mLASRe, and mLASRa were lower than pre - ablation, while LAEF was higher (P < 0.05). One month post-ablation, LAD, LAEDV, LAESV, LAVp, LASt, and LAVI were decreased compared with those before ablation, whereas LAA - V, LAEF, LVEF, LASRs, LASRe, LASRa, mLASRs, and mLASRe were increased (P < 0.05). Three months post-ablation, LAD, LAEDV, LAESV, LAVp, LAVI, and LASt were decreased compared with those before ablation, and LAA - V, LAEF, LVEF, LASRs, LASRe, LASRa, mLASRs, mLASRe, and mLASRa were increased compared to pre - ablation (P < 0.05) (Table 2).

Table 2 Changes of left atrial structure and function parameters before and after catheter ablation procedure.
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Cox regression analysis showed that the recovery rate of LASRs at 1 month post-ablation (ΔLASRs) was an independent predictor of AF recurrence (hazard ratio [HR] = 0.72, 95% confidence interval [CI]: 0.54–0.96, P = 0.023). Patients with ΔLASRs < 10% had a significantly higher recurrence rate than those with ΔLASRs ≥ 10% (32.1% vs. 11.5%, P = 0.014).

Discussion

1 AF is one of the most common arrhythmias, with its incidence rising markedly with age7. This study systematically reveals the dynamic evolution patterns of left atrial structure, function, and stiffness after radiofrequency ablation in PAF patients who have normal ejection fractions via multi-time-point echocardiography, as well as its clinical significance, which offer new insights into the mechanisms of atrial reverse remodeling and AF recurrence prediction.

2 Left atrial remodeling is an important pathological basis for the occurrence and maintenance of AF8. This study observed that the structure and function parameters of left atrium after radiofrequency ablation showed a characteristic time-dependent change pattern. In the early postoperative stage, significant changes in left atrial function occurred, manifested as reduced strain parameters and increased stiffness, possibly reflecting acute myocardial injury and inflammatory responses caused by ablation8. The transient decrease in LASRs (12.7% reduction) at 1 day post-ablation aligns with previous findings of acute myocardial stunning after thermal ablation9. Notably, recent advancements in ablation technology have introduced pulsed field ablation (PFA) as a novel strategy. Studies have shown that PFA may offer distinct advantages in preserving left atrial compliance compared to traditional thermal ablation techniques. A recent publication in JACC Clinical Electrophysiology highlighted that PFA is associated with a significantly lower risk of stiff left atrial syndrome, potentially due to its non-thermal mechanism of action that minimizes tissue fibrosis and structural damage10. This finding is particularly relevant as our study demonstrates that LA stiffness (LASt) recovery post-ablation is closely linked to clinical outcomes. While our cohort exclusively underwent radiofrequency ablation, the emerging evidence on PFA’s effects on LA mechanics warrants future investigation. Comparative studies between ablation modalities—specifically evaluating their impact on LA strain, stiffness, and long-term reverse remodeling—could further refine personalized treatment strategies for PAF patients10. Notably, left atrial structural parameters had not shown significant changes at this point, indicating that functional abnormalities may occur before structural alterations. As time went by, one month after the operation, there was an obvious reverse remodeling of the left atrium, shown as the continuous improvement of structural parameters and the gradual recovery of function, and this time-dependent change pattern provided important clues for understanding the reversibility of atrial remodeling11.

3 The early increase in LAEF (53.0% at 1 day post-ablation) deserves specific discussion. This may be attributed to compensatory mechanisms, such as reduced left atrial presystolic volume (LAVp) and improved ventricular diastolic function. The maintenance of LAEF despite decreased strain parameters suggests a transient adjustment in atrial-ventricular coupling, which warrants further investigation in future studies.

4 In terms of the predictive value of AF recurrence, this study found that the dynamic changes of left atrial stiffness and strain parameters had important clinical significance. The increase in stiffness in the early postoperative period may reflect the degree of myocardial injury12, while the subsequent sustained improvement suggests an effective reverse atrial remodeling process13. Notably, the recovery rate of LASRs at 1 month post-ablation emerged as a robust predictor of long-term outcomes, which is consistent with prior research showing that LA strain recovery correlates with sinus rhythm maintenance14. The observed HR of 0.72 for ΔLASRs indicates that each 10% increase in strain recovery reduces the recurrence risk by 28%, highlighting its clinical utility.

5 The dynamic evolution of left atrial structural and functional parameters may stem from multiple mechanisms15. Restored sinus rhythm reduces atrial volume and pressure load, creating conditions for reverse remodeling. Ablation may break the vicious cycle of electrical and structural remodeling by removing AF triggers and improving atrial substrate16. In addition, the regression of the inflammatory response17 and the initiation of the myocardial repair process jointly promote the gradual recovery of atrial function18. These mechanisms work together and eventually lead to the continuous improvement of structure and function of the left atrium19.

6 From the perspective of clinical application, the results of this study support the inclusion of the dynamic assessment of left atrial structure and function into the postoperative follow-up system. By monitoring the changes of parameters at specific times points, clinicians can evaluate the ablation effect and predict prognosis more accurately20. Especially, the time-independent change pattern of left atrial stiffness and strain parameters may provide important references for individualized treatment decisions21. For patients with suboptimal parameter improvement, early intervention and enhanced follow-up may contribute to improving the long-term prognosis.

7 Notably, the RFA procedure in this study utilized a standardized power setting of 35–40 W with a target temperature of 43 °C, consistent with conventional thermal ablation protocols for pulmonary vein isolation. However, we did not employ ablation index (AI) or contact force guidance, which are increasingly recognized as tools to optimize lesion transmurality and reduce complications9. Recent data from Europace highlighted that power settings significantly influence ablation efficacy in the left atrial posterior wall-specifically, higher power (40 W) achieved more consistent transmural isolation compared to lower settings (30 W), albeit with a slightly increased risk of collateral damage9. This aligns with our observation that LA strain parameters (e.g., LASRs) showed transient impairment at 1 day post-ablation, potentially reflecting acute thermal injury to atrial myocardium, particularly in the posterior wall where tissue thickness and proximity to adjacent structures may amplify energy effects.

8 In contrast, the absence of AI guidance means our approach relied on impedance monitoring and procedural experience to adjust lesion duration (typically 30–60 s per point), which may introduce variability in lesion quality. Future studies comparing AI-guided vs. conventional RFA could clarify whether standardized lesion parameters further enhance LA reverse remodeling, as more uniform transmural ablation might reduce residual atrial substrate and accelerate functional recovery. The correlation between posterior wall ablation power and LA stiffness recovery-observed in our 1-month follow-up data-merits exploration, as optimized energy delivery to this region may be critical for preserving atrial compliance and reducing recurrence risk10.

9 It is important to acknowledge several limitations of this study. First, the study cohort included only patients who underwent radiofrequency ablation, and the findings may not be generalizable to other ablation modalities such as cryoballoon or pulsed field ablation (PFA). Recent data have highlighted that PFA may preserve left atrial compliance more effectively than thermal ablation, which is an important consideration for future comparative studies22. Second, the baseline characteristics lacked detailed assessment of AF burden (e.g., attack frequency, duration), which could influence LA remodeling dynamics. Third, the follow-up period was limited to 3 months, and long-term data on the persistence of LA reverse remodeling are needed.

10 In summary, following radiofrequency ablation, the left atrium undergoes characteristic dynamic changes in structure, function, and stiffness. Study results suggest that: (1) A temporary drop in left atrial function within 1 day post-ablation is a normal physiological response and should not be over-interpreted as procedural failure; (2) The 1-month post-procedure evaluation is highly predictive of long-term surgical outcomes, with LASRs recovery rate serving as a key biomarker; (3) Left atrial strain parameters, particularly LASRs, are more sensitive than traditional parameters for assessing left atrial function. These findings provide an important basis for the clinical assessment of procedural outcomes and prognosis, and support incorporating 2D speckle tracking imaging into routine follow-up protocols.

Conclusion

10 This study systematically evaluates the dynamic changes in left atrial (LA) structure and function after catheter ablation in paroxysmal atrial fibrillation (PAF) patients using conventional echocardiography and 2D speckle-tracking imaging (2D-STI). The key findings reveal that LA reverse remodeling follows a characteristic pattern of “functional recovery preceding structural recovery". LA strain parameters transiently decreased at 1 day post-ablation, with structural and functional improvements observed from 1 month onward. The recovery rate of LA strain at 1 month is an independent predictor of atrial fibrillation recurrence. Multi-modal echocardiography, especially 2D-STI, effectively monitors these dynamic changes. Clinically, evaluating LA functional parameters at 1 month post-procedure aids in predicting long-term prognosis and guiding personalized follow-up.