Exploratory phase angle assessment after atrial fibrillation ablation in overweight patients: a pilot study

Abstract

Background

The phase angle (PhA), derived from bioelectrical impedance analysis (BIA), is an indicator of cellular health and nutritional status. Its role in patients with atrial fibrillation (AF), particularly after catheter ablation, is not well-established. This study aimed to investigate changes in PhA and their correlation with cardiac remodeling in overweight patients with persistent AF after cryoballoon ablation.

Methods

Thirteen overweight patients (BMI ≥ 23 kg/m²) with persistent AF scheduled for ablation were prospectively enrolled. One patient was excluded due to sick sinus syndrome requiring pacemaker implantation; thus, final analyses were performed on 12 patients. Baseline clinical, echocardiographic, and BIA parameters were collected. At 6 months, follow-up data were available for 12 patients. AF recurrence was defined as any documented atrial tachyarrhythmia ≥ 30 s beyond a 3-month blanking period, confirmed by ECG or Holter monitoring.

Results

Five patients experienced AF recurrence (PEF group), while seven maintained sinus rhythm (NSR group). Overall changes were modest; ECW/TBW was significant but numerically minimal, with no significant changes in other parameters. However, subgroup analysis demonstrated divergent changes in body composition. The NSR group showed substantial improvements in intracellular water and phase angle values, whereas the PEF group exhibited consistent declines (p < 0.05 for group comparisons).

Conclusion

These preliminary findings suggest that successful rhythm control after ablation may be associated with systemic recovery reflected by BIA-derived parameters. Larger, multicenter studies incorporating functional and clinical outcomes are warranted to validate the potential role of PhA as a biomarker for post-AF ablation recovery.

Trial registration

Not applicable.

Background

Atrial fibrillation (AF) is the most common arrhythmia increasing with age, and its prevalence is projected to grow worldwide substantially [1]. It is associated with significant morbidity, including stroke and heart failure, thereby impairing quality of life [2]. The pathophysiology of AF involves profound hemodynamic consequences; the loss of coordinated atrial contraction and an irregular ventricular response can reduce cardiac output, leading to systemic hypoperfusion and neurohormonal activation [3]. These changes aggravate fluid retention, a key feature in AF-related heart failure. Beyond its direct arrhythmogenic effects, AF is now increasingly recognized as a systemic condition associated with chronic inflammation and neurohormonal activation [4]. These processes contribute to adverse body composition changes, such as sarcopenia and cardiac cachexia, which are potent independent predictors of poor outcomes in patients with AF [5, 6]. Furthermore, obesity is a well-established risk factor for the development and progression of AF and is associated with lower success rates after catheter ablation [7]. The underlying mechanisms are complex, involving structural changes like left atrial enlargement, epicardial adipose tissue, and systemic inflammation [8]. Given this intricate relationship with obesity, understanding how rhythm control impacts body composition, particularly in overweight individuals, is of significant clinical importance. This highlights the need for tools that can assess the systemic burden of AF beyond traditional cardiac metrics. Bioelectrical Impedance Analysis (BIA) is a validated, non-invasive method for assessing body composition and fluid status in patients with cardiac conditions [9, 10]. While parameters such as the ratio of extracellular to total body water (ECW/TBW) can be used to quantify fluid overload [11], the phase angle (PhA) has emerged as a particularly valuable metric for this purpose. The PhA is a robust indicator of cellular health and membrane integrity [12]. A lower PhA reflects compromised cell membranes and is a powerful predictor of mortality in chronic diseases, particularly heart failure [13, 14]. It is considered an objective measure of systemic health, integrating information on fluid balance, nutritional status, and inflammation [15].

While rhythm control strategies for AF aim to improve cardiac function, their impact on systemic cellular integrity has not been fully elucidated. Therefore, this preliminary study was designed to investigate whether successful rhythm control can reverse systemic cellular impairments in this metabolically vulnerable overweight population, which is characterized by a higher burden of systemic inflammation and structural remodeling, by comprehensively evaluating changes in phase angle and body water composition following cryoablation.

Methods

Study population and design

This prospective, single-center, observational pilot study was approved by the Institutional Review Board of St. Vincent’s Hospital, The Catholic University of Korea (IRB No. VC24OISI0017), and all participants provided written informed consent. The study was conducted in accordance with the principles of the Declaration of Helsinki. We enrolled patients diagnosed with persistent atrial fibrillation who were scheduled for rhythm control therapy. The inclusion criteria were: (1) age ≥ 20 years, and (2) overweight, defined as a Body Mass Index (BMI) ≥ 23 kg/m². This cutoff value is based on the World Health Organization (WHO) Asia-Pacific guidelines and the Korean Society for the Study of Obesity [16, 17]. Baseline characteristics, echocardiographic data, and BIA parameters were collected before the procedure. All patients underwent follow-up assessments, including BIA and echocardiography, at 6 months (± 1 month) post-ablation. A total of 13 patients were initially enrolled. One patient was excluded from the follow-up analysis due to the aggravation of sick sinus syndrome requiring permanent pacemaker implantation after the AF ablation procedure. Consequently, the final analysis of post-ablation changes was performed on 12 patients.

The primary outcome was the change in phase angle from baseline to 6 months, stratified by rhythm outcome. Secondary outcomes included changes in intracellular water (ICW), total body water (TBW), extracellular water (ECW), and echocardiographic parameters such as LVEF, LAVI, and E/e’.

AF recurrence was defined as any episode of atrial tachyarrhythmia lasting ≥ 30 s, confirmed by 12-lead ECG, 24-hour Holter monitoring, or event recorder, beyond a 3-month blanking period. All patients underwent a scheduled ECG at each follow-up outpatient clinic visit, and a symptom-triggered ECG or Holter monitor was performed when clinically indicated. To ensure accurate classification at the study endpoint, rhythm status was re-evaluated at the 6-month follow-up visit. Regardless of symptoms, all patients underwent a mandatory 12-lead ECG concurrent with the BIA measurement. In cases where rhythm status was ambiguous or verification was needed, 24-hour Holter monitoring was utilized to confirm the maintenance of sinus rhythm or clinical recurrence.

Procedure

Cryoablation

All procedures were performed in fasting patients under conscious sedation, which was maintained with a continuous infusion of remifentanil. Following local anesthesia with 1% lidocaine, percutaneous vascular access was obtained from the right and left femoral veins. A 5Fr diagnostic catheter (typically quadripolar or decapolar) was positioned in the superior vena cava (SVC) for pacing and monitoring. A single transseptal puncture was performed under fluoroscopic and hemodynamic guidance to access the left atrium. In every case, intracardiac echocardiography (ICE) was also utilized for guidance. An 8.5Fr SL1 sheath was used for the puncture and subsequently exchanged for a 15Fr steerable sheath (FlexCath Advance™, Medtronic, Minneapolis, MN, USA). A 28 mm second-generation cryoballoon catheter (Arctic Front Advance Pro™, Medtronic) and an integrated circular mapping catheter (Achieve™, Medtronic) were then advanced into the left atrium. The procedure consisted of the complete electrical isolation of all four pulmonary veins (PVs). The target ablation temperature was typically between − 40 °C and − 60 °C. During ablation of the right-sided PVs, the phrenic nerve was continuously monitored by high-output pacing from the catheter in the SVC to prevent phrenic nerve injury. After successful pulmonary vein isolation, patients underwent synchronized direct current cardioversion (DCCV) under deep sedation with intravenous etomidate to restore sinus rhythm. The procedure was completed without any immediate complications.

Data collection

Clinical, echocardiographic, and bioelectrical impedance analysis (BIA) data were collected at baseline and the 6-month follow-up visit. Clinical data included demographics, comorbidities, and medications. Blood samples were collected for serum creatinine and N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels. At baseline, cardiac computed tomography (CT) was also performed to measure the left atrial (LA) diastolic volume, excluding the appendage. Transthoracic echocardiography was performed to assess left ventricular ejection fraction (LVEF), left atrial volume index (LAVI), E/e’, and right ventricular systolic pressure (RVSP). Body composition was measured using a multi-frequency BIA device (InBody BWA2.0, InBody Co., Ltd, Seoul, Korea). Patients were instructed to fast for at least 4 h before the measurement. All measurements were taken in a lying position, with electrodes attached to the hands and feet according to the manufacturer’s protocol. Baseline computed tomography left atrial volume (CT LAV) data were missing for one patient in the PEF group and were thus excluded from the relevant analyses.

Statistical analysis

As this was a preliminary study with a small sample size, non-parametric tests were employed for statistical analysis. Data are presented as median (interquartile range) for continuous variables and n (%) for categorical variables. To compare baseline characteristics between the two groups, the Mann-Whitney U test was used for continuous variables and Fisher’s exact test for categorical variables.

Paired comparisons between baseline and follow-up measurements within each group were performed using the Wilcoxon signed-rank test. To compare the magnitude of changes (Δ) in parameters between the two groups (NSR vs. PEF), the Mann-Whitney U test was employed. A p-value of less than 0.05 was considered statistically significant. All analyses were performed using R statistical software (version 4.2.3; R Foundation for Statistical Computing, Vienna, Austria).

Results

Baseline characteristics

Of the 13 initially enrolled patients, one patient was excluded from the final analysis due to post-procedural sick sinus syndrome requiring permanent pacemaker implantation. Therefore, rhythm monitoring and follow up analysis were performed in 12 patients, including 5 patients with persistent AF recurrence (PEF) and 7 patients maintaining sinus rhythm (NSR). Their baseline characteristics are summarized in Table 1. The median age of the total cohort was 59.5 years (IQR 56.3–64.5), and 11 patients (91.7%) were male. The median BMI was 27.8 kg/m² (IQR 26.5–30.2).

Table 1.

Baseline characteristics (n = 12)

	Total (n = 12)	Final Rhythm
		PEF (n = 5)	NSR (n = 7)	P-value
Age, years	59.50 (56.25–64.50)	61.0 (60.0–66.0)	58.0 (54.5–61.5)	0.412
Sex, male	11 (91.7%)	4 (80.0%)	7 (100.0%)	0.417
Weight, kg	83.05 (76.22–92.43)	72.4 (70.0-77.5)	88.0 (83.0-94.8)	0.030
BMI, kg/m²	27.80 (26.52–30.18)	25.6 (25.5–26.8)	30.0 (28.5–32.1)	0.003
Hypertension	8 (66.7%)	4 (80.0%)	4 (57.1%)	0.576
Diabetes mellitus	4 (33.3%)	2 (40.0%)	2 (28.6%)	1
Dyslipidemia	8 (66.7%)	5 (100.0%)	3 (42.9%)	0.081
COPD	0 (0.0%)	0 (0.0%)	0 (0.0%)	1
CKD	1 (8.3%)	1 (20.0%)	0 (0.0%)	0.417
E/e’	7.66 (6.60–9.39)	7.4 (7.0-8.3)	8.0 (6.6–9.4)	1
LVEF, %	58.50 (55.42–62.85)	57.7 (56.3–59.1)	61.6 (55.3–63.6)	0.530
LAVI, mL/m²	39.65 (37.10–52.80)	50.3 (35.6–76.4)	38.8 (38.0-42.4)	0.530
LAV, mL	84.55 (75.42–98.15)	93.5 (62.6–136.0)	81.9 (79.8–87.8)	0.530
RVSP, mmHg	28.40 (25.45–36.20)	35.2 (27.6–38.0)	26.9 (25.3–32.5)	0.290
CT LAV, mL*	214.96 (203.09-239.39)	213.7 (210.4-220.5)	231.6 (198.4-267.5)	0.927
Creatinine, mg/dL	1.00 (0.90–1.10)	1.0 (0.9–1.1)	1.0 (0.9–1.1)	0.934
NT-proBNP, pg/mL	379.00 (245.50-550.75)	631.0 (344.0-644.0)	313.0 (180.5–446.0)	0.106
Total Body Water, L	43.05 (39.98–45.80)	42.9 (39.1–43.9)	43.2 (41.5–46.5)	0.464
ICW, L	26.55 (24.90-28.68)	26.5 (24.3–26.6)	26.6 (25.7–28.9)	0.569
ECW, L	16.60 (15.30-17.65)	16.4 (14.8–17.3)	16.6 (16.0-17.6)	0.624
ECW/TBW	0.38 (0.38–0.39)	0.381 (0.380–0.389)	0.385 (0.377–0.388)	0.684
Phase Angle	6.60 (6.35–7.30)	6.6 (6.5–7.2)	6.6 (6.2–7.6)	1
Phase Angle T-score	-1.55 (-2.28–0.68)	-1.1 (-2.1-0.9)	-2.0 (-2.6–0.5)	0.569
Phase Angle Z-score	-0.05 (-1.10-0.38)	0.2 (-0.8-0.3)	-0.3 (-1.7-0.4)	0.625

*Final analyses were performed in 12 patients after exclusion of one patient who required permanent pacemaker implantation due to post-procedural sick sinus syndrome

At the 6-month follow-up, 5 patients experienced AF recurrence (PEF group), while 7 maintained sinus rhythm (NSR group). At baseline, the NSR group exhibited significantly higher body weight (PEF: 72.4 kg [IQR 70.0–77.5] vs. NSR: 88.0 kg [IQR 83.0–94.8]; p = 0.030) and BMI (PEF: 25.6 kg/m² [IQR 25.5–26.8] vs. NSR: 30.0 kg/m² [IQR 28.5–32.1]; p = 0.003) compared to the PEF group.

Other clinical demographics and comorbidities were comparable between the groups. The median age was 61.0 years (IQR 60.0–66.0) in the PEF group and 58.0 years (IQR 54.5–61.5) in the NSR group (p = 0.412). Echocardiographic parameters, including LVEF (PEF: 57.7% vs. NSR: 61.6%; p = 0.530) and LAVI (PEF: 50.3 mL/m² vs. NSR: 38.8 mL/m²; p = 0.530), did not differ significantly, although the PEF group showed numerically higher LAVI values.

Regarding baseline BIA parameters, there were no significant differences between the two groups. The whole-body phase angle was identical in both groups (Median 6.6 [IQR 6.5–7.2] in PEF vs. 6.6 [IQR 6.2–7.6] in NSR; p = 1.000), and the ECW/TBW ratio was also similar (PEF: 0.381 vs. NSR: 0.385; p = 0.684).

Changes in body composition and echocardiographic parameters

The parameter changes for the 12 patients who completed follow-up are presented in Table 2. In the total cohort, most parameters did not change significantly; ECW/TBW showed a statistically significant change, with a negligible absolute change. However, the subgroup analysis based on the rhythm outcome revealed substantial differences, particularly in BIA parameters. Changes in body weight (PEF: -3.60 kg vs. NSR: -0.40 kg; p = 0.625) and BMI (PEF: -1.27 kg/m² vs. NSR: -0.13 kg/m²; p = 0.639) were not significantly different between the groups. Similarly, changes in echocardiographic parameters such as LVEF (PEF: -1.10% vs. NSR: +1.00%; p = 0.343), LAVI (PEF: +1.2 mL/m² vs. NSR: +0.8 mL/m²; p = 1.00), and E/e’ (PEF: -0.48 vs. NSR: +0.88; p = 1.000) did not show significant differences. However, the change in Intracellular Water (ICW) was significantly different, showing a median decrease of -0.60 L (IQR − 1.40 to -0.50) in the PEF group versus a median increase of 0.30 L (IQR − 0.25 to 0.95) in the NSR group (p = 0.048). Furthermore, the change in the phase angle was also significantly different. The PEF group showed a median decrease of -0.20 (IQR − 0.30 to -0.10), whereas the NSR group showed a significant median increase of 0.50 (IQR 0.25 to 0.70) (p = 0.03). This opposing trend was observed across all phase angle-related variables. The changes in the Phase Angle T-score (PEF: -0.20 vs. NSR: +0.70; p = 0.03) and Z-score (PEF: -0.20 vs. NSR: +0.80; p = 0.03) were also significantly different between the two groups. In contrast, other BIA variables, including Total Body Water (PEF: -0.50 L vs. NSR: +0.60 L; p = 0.073), Extracellular Water (PEF: -0.10 L vs. NSR: +0.10 L; p = 0.222), and the ECW/TBW ratio (PEF: +0.01 vs. NSR: 0.00; p = 0.086), did not show statistically significant differences between the groups.

Table 2.

Comparison of changes in parameters at 6-Month Follow-up, stratified by rhythm outcome (n = 12)

	Total (n = 12)	P-value	Final Rhythm
			PEF (n = 5)	NSR (n = 7)	P-value
Weight, kg	-0.80 (-5.03-1.17)	0.176	-3.60 (-4.70-0.40)	-0.40 (-3.60-1.25)	0.625
BMI, kg/m²	-0.28 (-1.60-0.42)	0.204	-1.27 (-1.42-0.15)	-0.13 (-1.27-0.43)	0.639
E/e’	0.27 (-0.98-1.19)	0.677	-0.48 (-0.84-0.93)	0.88 (-1.50-1.45)	1
LVEF, %	0.15 (-1.33-2.57)	0.733	-1.10 (-2.20-0.80)	1.00 (-0.70-2.65)	0.343
LAVI, mL/m²	1.00 (-4.15-6.10)	0.733	1.20 (-3.80-5.10)	0.80 (-3.05-7.00)	1
LAV, mL	1.55 (-7.45-9.92)	0.791	1.50 (-7.10-5.20)	1.60 (-4.80-12.55)	0.876
RVSP, mmHg	0.70 (-6.13-4.18)	0.45	1.90 (1.40-4.00)	-4.00 (-7.55-2.35)	0.268
Creatinine, mg/dL	-0.03 (-0.13-0.04)	0.241	-0.05 (-0.10-0.04)	0.00 (-0.15-0.03)	0.871
NT-proBNP, pg/mL	-209.00 (-309.52-22.50)	0.151	24.00 (-277.00-236.00)	-279.20 (-401.15-136.65)	0.106
Total Body Water, L	-0.10 (-0.60-0.65)	0.838	-0.50 (-1.90-0.20)	0.60 (-0.25-1.35)	0.073
ICW, L	-0.25 (-0.65-0.42)	0.569	-0.60 (-1.40-0.50)	0.30 (-0.25-0.95)	0.048
ECW, L	0.00 (-0.10-0.32)	0.541	-0.10 (-0.50-0.00)	0.10 (-0.05-0.55)	0.222
ECW/TBW	0.00 (0.00-0.01)	0.026	0.01 (0.01–0.01)	0.00 (0.00–0.00)	0.086
Phase Angle	0.10 (-0.23-0.52)	0.373	-0.20 (-0.30-0.10)	0.50 (0.25–0.70)	0.03
Phase Angle T-score	0.15 (-0.32-0.72)	0.328	-0.30 (-0.40-0.20)	0.70 (0.35-1.00)	0.03
Phase Angle Z-score	0.15 (-0.25-0.82)	0.373	-0.20 (-0.40-0.10)	0.80 (0.35–1.05)	0.03

*Final rhythm classification was available in 12 patients at 6-month follow-up (PEF n = 5, NSR n = 7)

Discussion

In this preliminary pilot study, we investigated changes in body composition in overweight patients with persistent AF following cryoablation. While the overall cohort showed only modest, non-significant changes, a subgroup analysis revealed that the rhythm outcome was strongly associated with significant changes in markers of systemic cellular health. Our main finding is that patients who successfully maintained sinus rhythm (NSR group) exhibited a statistically significant improvement in both intracellular water (ICW) and all phase angle parameters. In contrast, patients with AF recurrence (PEF group) showed a consistent decline in these same markers. These findings suggest that successful rhythm control may promote systemic recovery, as detected by BIA.

Mechanism of body water changes: a shift from catabolism to anabolism

Our main finding is the divergent change in intracellular water (ICW), suggesting a shift from a persistent catabolic state in the PEF group to an anabolic recovery in the NSR group. Chronic AF is known to perpetuate a catabolic state, driven by systemic inflammation and neurohormonal activation that can lead to a reduction in body cell mass, of which ICW is a primary component [18, 19]. Conversely, our results suggest that restoring sinus rhythm can reverse this process. Successful rhythm control improves cardiac efficiency, which likely mitigates the systemic inflammatory and neurohormonal insults characteristic of chronic AF [20, 21]. This systemic stabilization creates a more favorable anabolic environment for cellular repair and rehydration. Therefore, the significant increase in ICW observed in the NSR group is not pathological fluid retention but rather a marker of improved lean body mass and cellular health [22].

Phase angle as an indicator of cellular recovery

PhA is considered a global marker of cellular health, and numerous studies have demonstrated its prognostic value across various chronic conditions [23–26]. We hypothesized that successful ablation might lead to favorable changes in cellular function, reflected by an increase in PhA. Our results support this hypothesis. The significant increase in phase angle and its standardized scores in the NSR group suggests that the benefits of restoring sinus rhythm extend beyond cardiac remodeling to a systemic cellular level. This recovery is likely multifaceted.

First, successful rhythm control attenuates the chronic, low-grade inflammation and oxidative stress that are intrinsically linked to AF [27]. This systemic inflammatory state is known to compromise cell membrane integrity, a key determinant of PhA [28]. Therefore, restoration of sinus rhythm may lead to recovery of cell membrane function, as reflected by an improvement in PhA.

Second, the hemodynamic stabilization following successful ablation likely mitigates the sustained neurohormonal activation, particularly of the renin-angiotensin-aldosterone system, which contributes to a systemic catabolic state in chronic AF [29]. The concurrent rise in ICW in our NSR group supports this notion, suggesting a favorable shift from catabolism to an anabolic state of cellular repair and rehydration.

The divergence in PhA change between our groups suggests that persistent AF perpetuates systemic cellular distress, while restoring sinus rhythm may actively reverse it. Consequently, PhA may reflectsystemic cellular recovery beyond conventional nutritional assessment parameters.

Although the absolute increase in PhA observed in the NSR group (+ 0.50°) may appear modest, it is clinically significant given the narrow physiological range of this parameter. Previous studies have established that small variations in PhA carry substantial prognostic weight. For example, Mullie L, et al. reported that a 1° decrease in PhA is associated with a more than 3-fold increase in mortality risk among patients with cardiac disease [30]. Furthermore, Colin-Ramirez et al. demonstrated that the thresholds that distinguish prognostic quartiles in heart failure patients are often separated by less than 1 °. In their study, the transition from the lowest quartile (associated with the worst survival) to the next quartile was marked by a difference of only approximately 0.7° (e.g., < 4.2° vs. 4.2–4.9°) [14]. Thus, the observed divergence in PhA trajectories between our study groups likely reflects a meaningful reversal of systemic catabolism rather than a trivial fluctuation.

These observations are further supported by the explicit definition of arrhythmia recurrence and the structured monitoring strategy employed in this study. However, potential confounders such as changes in pharmacologic therapy—particularly diuretics or antiarrhythmic drugs—may have affected BIA results and were not tightly controlled. In the future, larger trials should adopt uniform follow-up protocols that include continuous or extended rhythm monitoring, systematic documentation of medication adjustments, and assessments of functional status, such as exercise capacity or NYHA classification. Incorporating these elements will help to clarify whether phase angle may serve as a reliable biomarker of systemic recovery after ablation. Ultimately, validation in broader, multicenter populations will be necessary to determine whether PhA can complement ECG, echocardiography, and natriuretic peptide testing as part of post-ablation follow-up.

Limitations

First, it is essential to emphasize that this is a preliminary, hypothesis-generating study with a small sample size. The statistical power is inherently limited, and the findings should be interpreted with caution as exploratory. One patient was excluded from the final analysis due to a procedure-related complication, which further limited the already small sample size. This small cohort size likely contributed to the lack of statistical significance for parameters with observed trends. While we observed a strong association between rhythm outcome and changes in PhA, this observational study cannot establish causality. Although the PEF group exhibited numerically higher values for markers of structural stress (LAVI, RVSP) and lower ICW, suggesting a more advanced underlying disease burden, the NSR group had a significantly higher baseline BMI. This disparity may be partly attributable to the sex distribution, as the NSR group consisted exclusively of male patients. While baseline phase angle values were comparable between the two groups, the PEF group declined, whereas the NSR group increased, suggesting that the rhythm outcome itself may have played a critical role in altering the trajectory of systemic cellular health. Nevertheless, due to the limited statistical power, these results should be regarded as preliminary and interpreted with caution. A larger, prospective study, perhaps with serial measurements, would be needed to elucidate the temporal relationship and causal pathways between rhythm restoration and systemic cellular recovery.

Second, this study focused on surrogate endpoints derived from BIA and echocardiography without incorporating patient-centered clinical outcomes. Data on changes in functional status, such as NYHA functional class, exercise capacity (e.g., 6-minute walk test), and clinical events like rehospitalization for heart failure, were not collected. Consequently, the direct clinical relevance of the observed changes in phase angle and intracellular water remains to be established. While these findings lay the groundwork for the potential use of PhA as a biomarker of systemic recovery in the context of AF, it remains speculative and requires further validation.

Third, as a single-center study, the findings may have limited generalizability. The patient population and procedural techniques may not be representative of other centers. Furthermore, the 6-month follow-up period is relatively short compared to standard AF outcome trials. This limited study period likely led to underdetection of late arrhythmia recurrences, resulting in an underestimated recurrence rate. However, strictly confirming rhythm status at the 6-month endpoint via mandatory ECG/Holter minimized misclassification at the time of BIA assessment. Moreover, if patients destined for late recurrence were categorized in the NSR group, this would likely attenuate the observed differences between groups (a bias toward the null). Thus, the significant divergence in BIA parameters observed despite this short observation window suggests that phase angle may be a sensitive marker of early systemic recovery. Future studies with longer follow-up are necessary to confirm the sustainability of these changes.

Fourth, several potential confounders that could influence BIA measurements, such as dietary changes, physical activity levels, and medication adjustments (particularly diuretics), were not rigorously controlled for in this pilot study. Future studies should incorporate standardized protocols for these variables to isolate the effect of rhythm control on body composition.

Finally, regarding the echocardiographic findings, the trend toward a reduction in RVSP in the NSR group is physiologically plausible and consistent with prior studies, which have shown that successful AF ablation can lead to left atrial reverse remodeling, reduced filling pressures, and a subsequent decrease in pulmonary pressures [31, 32]. However, we did not observe significant changes in LAVI itself. This lack of difference is likely attributable to the small sample size and a relatively short follow-up period, as structural remodeling is a process that may evolve over a longer timeframe. Despite these limitations, our findings provide early evidence that systemic recovery after rhythm control in AF may be captured by BIA-derived metrics, which are simple, non-invasive, and repeatable, making them attractive adjuncts for monitoring recovery in clinical practice. These initial results provide a further rationale for large-scale multicenter prospective studies to validate these findings, establish the long-term prognostic value of BIA parameters, and correlate them with hard clinical outcomes in patients with atrial fibrillation.

Conclusion

In this pilot study of overweight patients with persistent AF, the successful maintenance of sinus rhythm after cryoablation was associated with a favorable change in intracellular water and phase angle. While these results provide preliminary evidence supporting BIA-derived parameters as potential indicators of systemic recovery, they should be interpreted with caution, given the small sample size and the absence of clinical outcome measures. Future large-scale, multicenter studies are required to confirm these associations and to determine the prognostic utility of PhA in the follow-up of patients undergoing AF ablation.

Abbreviations

AF

Atrial Fibrillation

BIA

Bioelectrical Impedance Analysis

BMI

Body Mass Index

CT

Computed Tomography

DCCV

Direct Current Cardioversion

ECG

Electrocardiogram

ECW

Extracellular Water

ICE

Intracardiac Echocardiography

ICW

Intracellular Water

IQR

Interquartile Range

LA

Left Atrial

LAVI

Left Atrial Volume Index

LVEF

Left Ventricular Ejection Fraction

NSR

Normal Sinus Rhythm

NT-proBNP

N-terminal pro-B-type natriuretic peptide

PEF

Persistent/Recurrent Atrial Fibrillation

PhA

Phase Angle

PV

Pulmonary Vein

RVSP

Right Ventricular Systolic Pressure

SVC

Superior Vena Cava

TBW

Total Body Water

Authors’ contributions

YMH designed and performed the experiments, derived the models, and analysed the data. SJK assisted with measurements. SSC led the manuscript preparation. All authors provided critical feedback and contributed to shaping the research, analysis, and manuscript.

Funding

Not applicable.

Data availability

The data that support the findings of this study are not openly available due to reasons of sensitivity and are available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

This study was approved by the Institutional Review Board of St. Vincent’s Hospital, The Catholic University of Korea (IRB No. VC24OISI0017). It was conducted in accordance with the principles of the Declaration of Helsinki. Written informed consent was obtained from all participants.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.