Temporal predictive value of left atrial strain and stiffness index for atrial fibrillation recurrence after electrical cardioversion

Abstract

Objective

To evaluate the predictive value of LA strain parameters and LASI for AF recurrence following electrical CV, and to compare them to conventional echocardiographic, biochemical, and clinical markers.

Methods

In this prospective, observational pilot study, 31 patients with persistent AF underwent electrical CV and were followed for six months. Echocardiographic evaluation included LA reservoir, conduit, and contractile strain, left atrial stiffness index, left atrial volume index (LAVI), left atrial appendage (LAA) morphology, left ventricular ejection fraction (LVEF), right atrial (RA) area, and right ventricular systolic pressure (RVSP). AF recurrence was assessed at three and six months.

Results

At three months post-CV, LA reservoir, conduit, and contractile strain values were significantly negatively associated with AF recurrence (p < 0.001), while LASI and E/E′ ratios were positively associated (p < 0.001). At six months, only contractile strain retained prognostic significance (p = 0.008). LVEF showed a positive correlation with recurrence at six months (p = 0.003), potentially reflecting the role of diastolic dysfunction.

Conclusion

LA strain parameters and LASI are valuable tools for predicting AF recurrence after CV, particularly in the early post-procedural period. Contractile strain may serve as a more reliable long-term predictor, emphasizing the importance of longitudinal atrial function assessment in rhythm outcome prediction. However, given the small sample size and single-center design, these results should be considered hypothesis-generating, requiring validation in larger studies.

Keywords

left atrium atrial fibrillation fibrosis electrical cardioversion

Key points

Left atrial reservoir, conduit, and contractile strain parameters were significantly associated with AF recurrence at three months post-cardioversion, supporting their utility in short-term rhythm outcome prediction.

The left atrial stiffness index (LASI), which integrates LA strain and LV filling pressure, showed significant positive correlation with AF recurrence at three months, highlighting its role in early risk stratification.

Among all strain parameters, only contractile strain remained a significant predictor of AF recurrence at six months, suggesting it may better reflect persistent atrial dysfunction.

LA strain imaging enables more sensitive and earlier identification of atrial dysfunction compared with traditional indices such as LAVI.

Measuring LA strain offers clinically relevant prognostic information, supporting its integration into routine evaluation of patients with persistent AF undergoing cardioversion.

1 Introduction

Atrial fibrillation (AF) is the most common cardiac arrhythmia, associated with significant clinical consequences, including thromboembolism and heart failure. It induces both structural and functional remodeling of the left atrium (LA), often leading to fibrosis.^1,2

Left atrial volume index (LAVI) has traditionally been used to predict AF recurrence,³ but recent studies suggest that LA strain, which directly reflects atrial deformation throughout the cardiac cycle, may be a more sensitive predictor.^4–6 Speckle tracking echocardiography (STE), initially developed for ventricular assessment, has become increasingly applied in atrial evaluation due to its angle independence and reduced susceptibility to artifacts.^1,7

Average LA longitudinal strain and strain rate have been shown to inversely correlate with the extent of atrial fibrosis, as confirmed by cardiac magnetic resonance imaging or histology, indicating their potential role as non-invasive markers of structural remodeling.⁸

The left atrial stiffness index (LASI), calculated as the ratio between LA reservoir strain and estimated LV filling pressure (e.g., E/e′), represents the relationship between LA deformation and ventricular diastolic load.⁹ This index may offer improved predictive accuracy for AF recurrence compared to conventional echocardiographic parameters.¹⁰

Beyond arrhythmia prediction, recent data have highlighted LA strain as a prognostic marker for broader outcomes, including ischemic stroke and cognitive decline.¹¹

The primary aim of this study was to assess the predictive value of LA strain parameters and LASI for AF recurrence in patients undergoing electrical cardioversion (CV). The secondary aim was to explore associations between clinical and biochemical factors with echocardiographic measures of LA function and diastolic filling, and AF recurrence after cardioversion.

2 Patients and methods

2.1 Patients and study design

This prospective, observational pilot study included 31 patients treated at the Department of Cardiology, General Hospital “Prim. Dr Abdulah Nakaš,” between May 2023 and May 2024. Eligible patients were older than 18 years with persistent AF (lasting 7 days to 12 months) who underwent electrical CV with successful restoration of sinus rhythm. Patients were excluded if they had prior AF ablation, significant valvular disease, left ventricular ejection fraction (LVEF) < 30%, poor echocardiographic image quality, recent cardiac surgery, active infection, malignancy, autoimmune disease, untreated hyperthyroidism, advanced renal dysfunction (eGFR <30 mL/min/1.73 m²), pregnancy or inability to complete follow-up. All patients provided written informed consent prior to inclusion. The study was conducted in accordance with the Declaration of Helsinki and approved by the institutional ethics committee.

2.2 Methods

All patients underwent both transthoracic and transesophageal echocardiography prior to CV, irrespective of prior anticoagulation therapy. The following echocardiographic parameters were evaluated: LVEF, LAVI, E/E’ ratio, LA reservoir, conduit, and contractile strain, LASI (calculated as E/E’ divided by LA reservoir strain), right ventricular systolic pressure (RVSP), and right atrial (RA) area. Additional clinical data included age, sex, body mass index (BMI), high-sensitive C-reactive protein (hs-CRP), N-terminal pro-B-type natriuretic peptide (NT-proBNP), and left atrial appendage (LAA) morphology.

Patients were followed for six months, with assessments at three and six months post-CV. The primary endpoint was AF recurrence, defined as an episode lasting more than 30 s on 24-h Holter ECG monitoring. For the analysis of recurrence at six months, only patients who maintained sinus rhythm at the three-month follow-up were included.

2.3 Statistical analysis

Normality of distribution for continuous variables was assessed using the Shapiro–Wilk test. Variables were presented as mean ± standard deviation (SD) or median with interquartile range (IQR), as appropriate. Association of AF recurrence and LAA morphology with other parameters were performed using the Independent Samples t-test (assuming equal variances based on Levene's test) or the Mann–Whitney U test, depending on data distribution. Correlations among echocardiographic parameters, and with age, BMI, and serum biomarkers, were analyzed using Pearson's or Spearman's coefficients, as appropriate. A p-value ≤ 0.05 was considered statistically significant. Statistical analyses were conducted using IBM SPSS Statistics, version 29.0 (IBM Corp., Armonk, NY, USA).

3 Results

The study cohort consisted of 31 patients aged 52 to 75 years, with a median age of 59 years (IQR: 56-66). Men represented for 64.5% of the population (n = 20), and women 35.5% (n = 11). The median BMI was 31 kg/m² (IQR: 28-32). The mean NT-proBNP concentration was 585 ± 312 pg/mL, and the median hs-CRP level was 1.5 mg/L (IQR: 1.0-1.5).

Regarding LAA morphology, the majority of patients (n = 19, 61.3%), exhibited a chicken-wing configuration. A windsock morphology was identified in 9 patients (29%), a cauliflower-type in 2 patients (6.5%), and a cactus-type in 1 patient (3.2%).

At three months post-CV, AF recurred in 6 patients (18.8%). Among the 25 patients who remained in sinus rhythm at that point, 6 additional patients experienced recurrence by six months, resulting in an overall recurrence rate of 37.5%.

A statistically significant negative correlation was found between AF recurrence at three months post-CV and the following echocardiographic parameters: LA reservoir strain (p < 0.001), LA conduit strain (p < 0.001), and LA contractile strain (p < 0.001). In contrast, both LASI and the E/E′ ratio demonstrated a significant positive correlation with AF recurrence three months post-CV (p < 0.001 for both). Six months post-CV, only LA contractile strain showed statistically significant negative correlation with AF recurrence (p = 0.008). No significant correlation was found between LAVI and AF recurrence at either follow-up point (Table 1).

Table 1.
Association between echocardiographic parameters and atrial fibrillation recurrence three and six months after electrical cardioversion.

Total AF recurrence after 3 months AF recurrence after 6 months No recurrence

(N=31) (N = 6) (N = 6) (N = 19)

95% CI 95% CI

Echocardiographic

parameters Mean ± SD Mean ±SD p Lower Upper Mean ±SD p Lower Upper Mean ±SD

LAVI (mL/m²) 55.59 ± 1.83 58.88 ±5.87 0.38 −13.59, 5.44 60.21 ±13.26 0.16 −3.52, 17.48 53.1 ±9.87

E/E’ ratio 16.85 ±0.53 20.53 ±1.39 <0.001 −6.79, −2.34 16.9 ±1.69 0.31 −1.23, 3.69 15.67 ±2.73

LA reservoir strain (%) 23.35 ±0.88 17.17 ±2.13 <0.001 4.02, 11.33 22.5 ±3.01 0.12 −7.02, 0.87 25.58 ±4.32

LA conduit strain (%) 11.61 ± 0.66 7 ±1.89 <0.001 2.96, 8.48 11.17 ±1.94 0.17 −5.02, 0.93 13.21 ±3.32

LA contractile strain (%) 8.00 ± 0.46 4.5 ±1.37 <0.001 2.54, 6.14 7 ±1.67 0.008 −4.14, −0.70 9.42 ±1.80

LASI 0.77 ±0.05 1.21 ±0.20 <0.001 −0.74, −0.35 0.77 ±0.16 0.20 −0.07, 0.33 0.64 ±0.21

LVEF (%) 52 ±3 52.67 ±3.20 0.76 −3.84, 2.83 55 ±1.67 0.003 1.46, 6.00 51.26 ±3.67

RVSP (mmHg) 35 ±3 34.83 ±2.13 0.67 −2.10, 3.24 34.17 ±1.60 0.12 −4.50, 1.26 35.79 ±3.25

RA area (cm²) 17 (15.6, 18.5) 16.0 (15, 18.4) 0.38 16.25 (15.5, 17.2) 0.14 17.5 (15.9, 19)

	Total	AF recurrence after 3 months	AF recurrence after 6 months	No recurrence
LAVI (mL/m²)	55.59 ± 1.83	58.88 ±5.87	0.38	−13.59, 5.44	60.21 ±13.26	0.16	−3.52, 17.48	53.1 ±9.87
E/E’ ratio	16.85 ±0.53	20.53 ±1.39	<0.001	−6.79, −2.34	16.9 ±1.69	0.31	−1.23, 3.69	15.67 ±2.73
LA reservoir strain (%)	23.35 ±0.88	17.17 ±2.13	<0.001	4.02, 11.33	22.5 ±3.01	0.12	−7.02, 0.87	25.58 ±4.32
LA conduit strain (%)	11.61 ± 0.66	7 ±1.89	<0.001	2.96, 8.48	11.17 ±1.94	0.17	−5.02, 0.93	13.21 ±3.32
LA contractile strain (%)	8.00 ± 0.46	4.5 ±1.37	<0.001	2.54, 6.14	7 ±1.67	0.008	−4.14, −0.70	9.42 ±1.80
LASI	0.77 ±0.05	1.21 ±0.20	<0.001	−0.74, −0.35	0.77 ±0.16	0.20	−0.07, 0.33	0.64 ±0.21
LVEF (%)	52 ±3	52.67 ±3.20	0.76	−3.84, 2.83	55 ±1.67	0.003	1.46, 6.00	51.26 ±3.67
RVSP (mmHg)	35 ±3	34.83 ±2.13	0.67	−2.10, 3.24	34.17 ±1.60	0.12	−4.50, 1.26	35.79 ±3.25
RA area (cm²)	17 (15.6, 18.5)	16.0 (15, 18.4)	0.38		16.25 (15.5, 17.2)	0.14		17.5 (15.9, 19)

Abbreviations: AF – atrial fibrillation; CI – confidence interval; LA – left atrial; LAVI – left atrial volume index; LASI – left atrial stiffness index; LVEF – left ventricular ejection fraction; N – number of participants; p – probability value; RA – right atrial; RVSP – right ventricular systolic pressure; SD – standard deviation.

Data are expressed as mean ± SD, except for RA area, which is presented as median (interquartile range). Intergroup differences were assessed using the Independent Samples T-test, except for RA area (Mann-Whitney U test). Equal variances were assumed based on Levene's test, except for LVEF. P-value <0.05 was considered statistically significant.

LVEF was positively associated with AF recurrence at six months post-CV (p = 0.003), whereas RA area and RVSP showed no significant correlation with AF recurrence at either time point (Table 1).

There was no statistically significant correlation between hs-CRP levels, NT-proBNP levels, age, or BMI with AF recurrence at three or six months.

LVEF, RA area, and RVSP did not correlate with any parameters of LA function or diastolic filling. BMI and NT-proBNP each demonstrated a significant positive correlation exclusively with LAVI (p = 0.001 and p = 0.045, respectively), while neither age nor hs-CRP showed a significant correlation with any of the evaluated echocardiographic parameters of LA function and diastolic filling.

There was no statistically significant correlation between LAA morphology and AF recurrence at three or six months. Similarly, echocardiographic parameters were not significantly associated with LAA morphology (Table 2).

Table 2.

Association of parameters of left atrial function and diastolic filling and left atrial appendage morphology.

Variable	LAA morphology^a
Variable	Windsock (N = 9)	Chicken-wing (N = 19)	t-value	Df	p-value	95% CI (Lower, Upper)
LAVI (mL/m²)	57.07 ± 5.75	55.72 ± 11.72	0.325	26	0.747	(−7.18, 9.88)
E/E’ ratio	17.51 ± 3.08	16.33 ± 3.03	0.962	26	0.345	(−1.35, 3.72)
LA reservoir strain (%)	22.56 ± 4.45	23.84 ± 5.21	−0.637	26	0.529	(−5.44, 2.86)
LA conduit strain (%)	11.11 ± 3.41	11.95 ± 4.14	−0.526	26	0.604	(−4.11, 2.43)
LA contractile strain (%)	7.78 ± 2.44	8.16 ± 2.65	−0.363	26	0.72	(−2.53, 1.77)
LASI	0.82 ± 0.26	0.74 ± 0.32	0.588	26	0.562	(−0.18, 0.33)

Abbreviations: CI – Confidence interval; df – degrees of freedom; LA – left atrial; LAA – left atrial appendage; LASI – left atrial stiffness index; LAVI – left atrial volume index; N – number of participants; p – Probability value; SD – standard deviation.

Three patients with other LAA morphologies were excluded.

Data are expressed as mean ± SD. Differences between variables were assessed by Independent Samples T-test. Equal variances assumed based on Levene's test.

4 Discussion

Our findings suggest that LA strain parameters have prognostic value for predicting AF recurrence post-CV, although this predictive capacity may diminish over time. While LA reservoir, conduit, and contractile strain showed significant inverse correlations and LASI showed significant positive association with AF recurrence at three months, only contractile strain remained significantly associated at six months. This temporal pattern likely reflects progressive atrial remodeling in the chronic post-CV phase. Although the predictive role of LA strain and LASI has been reported previously, our analysis adds the perspective of temporal dynamics, which should be regarded as preliminary and hypothesis-generating.

Previous studies have already established the predictive role of LA strain in the early period following CV or ablation, but few have specifically investigated whether this prognostic value changes over time. Most prior research focused on LA reservoir strain as the most robust predictor of AF recurrence, especially in the short term.^12–15 Vincenti et al. demonstrated persistent reservoir strain impairment after ECV in patients with larger and stiffer atria and higher E/e′ ratios.¹⁶ These patients exhibited higher LA filling pressures compared with those showing mechanical recovery, reinforcing the concept that structural and functional remodeling can attenuate recovery of atrial mechanics and increase recurrence risk.

On the other hand, our findings suggest contractile strain as a more reliable long-term marker. Whether this observation reflects genuine physiological differences in atrial remodeling or methodological limitations inherent to our study remains uncertain and warrants further investigation.

More robust evidence exists for the prognostic role of LA strain after catheter ablation. The CASA-AF trial identified contractile strain as a key predictor of arrhythmia recurrence at three months post-ablation.¹⁷ Other studies have demonstrated that reduced global LA strain and elevated LASI are associated with a higher risk of recurrence following ablation procedures.^10,18,19 Additionally, LA strain values have been inversely associated with atrial fibrosis detected by cardiac MRI or histology,^8,20 reinforcing their value as non-invasive markers of structural remodeling. Despite variable cut-off values reported across studies, strain parameters have shown consistent prognostic value, though age- and sex-specific thresholds may improve predictive accuracy.²¹

Notably, our study also identified a positive association between LVEF and AF recurrence at six months post-cardioversion. While reduced LVEF is typically associated with adverse atrial remodeling, our findings indicate that atrial dysfunction can also be present in patients with preserved or mildly reduced EF, possibly due to underlying diastolic dysfunction.^22–24 Indeed, patients with higher EF exhibited higher E/E′ ratios, although this correlation was not statistically significant. Given the narrow LVEF range in our cohort (mean 52% ± 3%), as well as the potential confounding factors such as unmeasured comorbidities (e.g., hypertension, diabetes, coronary disease), pharmacologic therapy, variability in diastolic function and selection bias, this result should be interpreted cautiously. Larger validation studies are therefore required to clarify whether this association reflects a true causal link or is attributable to residual confounding.

Among biochemical markers, NT-proBNP was significantly associated with LAVI, but not with other functional parameters.^25–27 Similarly, the predictive value of hs-CRP remains inconsistent in the literature.^28–30 Our findings suggest that echocardiographic strain parameters may provide more robust and sensitive prognostic insights than biochemical markers alone.

No significant association was observed between LAA morphology and AF recurrence, which aligns with previous studies.^31,32 However, we observed higher NT-proBNP levels in patients with windsock-type LAA morphology, possibly reflecting increased atrial wall stress associated with that anatomical configuration.

To date, few studies have comprehensively evaluated all components of LA strain in relation to AF recurrence, particularly in the context of electrical cardioversion. Most prior research has relied on small cohorts (typically 20-130 patients) and focused predominantly on reservoir strain, often without integrating biochemical or morphological parameters. In contrast, our study employed a multifaceted approach, simultaneously assessing reservoir, conduit, and contractile strain, integrating LASI, and examining clinical, echocardiographic, and biochemical correlations. This offers a more complete characterization of atrial function and its impact on rhythm outcomes after CV.

4.1 Study limitations

Study limitations include a small sample size, reliance on single-timepoint strain measurements, and use of two-dimensional STE, which may not fully capture complex atrial mechanics. Three-dimensional STE could offer improved spatial resolution, while integration with CMR-based fibrosis imaging may enhance patient stratification.^1,33–36 Additionally, the observational, single-center design of the study limits causal inference and generalizability, while the relatively short follow-up period may not fully reflect long-term recurrence patterns. Variability in image quality and operator dependency inherent to STE may also impact reproducibility of strain measurements. Furthermore, the absence of continuous rhythm monitoring may have led to underestimation of asymptomatic or short-duration AF episodes. Finally, the limited sample size precluded meaningful multivariable adjustment, and as such, the present findings should be regarded as exploratory and hypothesis-generating, requiring validation in larger multicenter studies.

5 Conclusion

Strain imaging allows for earlier and more sensitive detection of LA dysfunction compared to conventional indices such as LAVI. LA strain parameters, including LASI, are valuable tools for predicting AF recurrence, particularly in the early post-cardioversion period. Our findings highlight contractile strain as a potentially more durable marker, suggesting its role in anticipating rhythm outcomes during progressive atrial remodeling. However, given the small, single-center sample and absence of multivariable adjustment, these results should be considered exploratory and hypothesis-generating, requiring confirmation in larger multicenter studies.

Footnotes

Acknowledgments

None.

Ethical considerations

Ethical approval was obtained from the institutional ethics committee.

Consent to participate

All participants provided written informed consent prior to inclusion.

Consent for publication

Not applicable.

Author contributions

NMV: Conceptualization, methodology, data collection, statistical analysis, writing—original draft, AD: Data acquisition, echocardiographic analysis, BA: Patient recruitment, clinical data interpretation, AI: Statistical support, data verification, ZB: Echocardiographic measurements, data curation, NSB: Data interpretation, supervision, EB: Data acquisition, echocardiographic analysis, Methodology refinement, writing—review and editing, AM: Supervision, critical revision of the manuscript, guidance on study design. TKP: Supervision, critical revision of the manuscript, BS: Critical review, guidance on study design, MO: Senior supervision, final approval of the manuscript

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Statements and declarations

Preliminary, incomplete results from this study were presented as an abstract at the 15th Congress of the Croatian Cardiac Society with International Participation, held in November 2024.

ORCID iDs

Nejra Mlaco-Vrazalic

Ada Dozic

Zijo Begic

Nirvana Sabanovic-Bajramovic

Edin Begic

Akif Mlaco

Bojan Stanetic

Miodrag Ostojic

Buena Aziri

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	Total	AF recurrence after 3 months				AF recurrence after 6 months				No recurrence
	(N=31)	(N = 6)				(N = 6)				(N = 19)
				95% CI				95% CI
Echocardiographic
parameters	Mean ± SD	Mean ±SD	p	Lower	Upper	Mean ±SD	p	Lower	Upper	Mean ±SD
LAVI (mL/m²)	55.59 ± 1.83	58.88 ±5.87	0.38	−13.59, 5.44		60.21 ±13.26	0.16	−3.52, 17.48		53.1 ±9.87
E/E’ ratio	16.85 ±0.53	20.53 ±1.39	<0.001	−6.79, −2.34		16.9 ±1.69	0.31	−1.23, 3.69		15.67 ±2.73
LA reservoir strain (%)	23.35 ±0.88	17.17 ±2.13	<0.001	4.02, 11.33		22.5 ±3.01	0.12	−7.02, 0.87		25.58 ±4.32
LA conduit strain (%)	11.61 ± 0.66	7 ±1.89	<0.001	2.96, 8.48		11.17 ±1.94	0.17	−5.02, 0.93		13.21 ±3.32
LA contractile strain (%)	8.00 ± 0.46	4.5 ±1.37	<0.001	2.54, 6.14		7 ±1.67	0.008	−4.14, −0.70		9.42 ±1.80
LASI	0.77 ±0.05	1.21 ±0.20	<0.001	−0.74, −0.35		0.77 ±0.16	0.20	−0.07, 0.33		0.64 ±0.21
LVEF (%)	52 ±3	52.67 ±3.20	0.76	−3.84, 2.83		55 ±1.67	0.003	1.46, 6.00		51.26 ±3.67
RVSP (mmHg)	35 ±3	34.83 ±2.13	0.67	−2.10, 3.24		34.17 ±1.60	0.12	−4.50, 1.26		35.79 ±3.25
RA area (cm²)	17 (15.6, 18.5)	16.0 (15, 18.4)	0.38			16.25 (15.5, 17.2)	0.14			17.5 (15.9, 19)