Mechanical and hemodynamic assessment of the LA is essential for diagnosing, stratifying risk, and managing AF and related cardiovascular diseases.

LA contributes to ventricular filling through 3 distinct mechanical phases that occur sequentially during the cardiac cycle. During ventricular systole, the LA acts as a reservoir, collecting blood from the pulmonary veins; in early diastole, it serves as a conduit, allowing passive blood flow into the left ventricle; and in late diastole, it functions as a booster pump, actively contracting to augment ventricular preload. LA mechanical performance—encompassing reservoir, conduit, and booster pump phases—reflects the integrated effects of LA relaxation, stiffness, and contractility, modulated by ventricular interaction.

In this review, mechanical function refers to the intrinsic contractile and reservoir properties of the atrial myocardium, including deformation, strain, emptying fraction and phasic contribution to ventricular filling. In contrast, hemodynamic function describes flow and pressure characteristics such as compliance, transmitral flow, and filling dynamics that reflect the interaction between the LA and left ventricle.

A multimodal approach incorporating electrocardiography (ECG), intracardiac electrogram analysis, echocardiography, cardiac computed tomography (CT), and cardiac magnetic resonance imaging (CMR) provides complementary insights into LA structure, function, and electrical substrate. While surface ECG and imaging characterize global remodeling and mechanical performance, electrocardiogram analysis during ablation offers real-time information on local conduction properties and fibrosis.

Surface ECG parameters can identify atrial myopathy and predict AF recurrence or stroke. Prolonged P-wave duration or increased P-wave dispersion reflect interatrial conduction delay, while abnormal P-wave terminal force in V1 correlates with LA enlargement and fibrosis. ^,,,,,

Strengths: widely available, low cost.

Limitations: limited spatial resolution; unable to localize structural remodeling, rhythm-dependent measurements (sinus rhythm vs AF).

Echocardiography remains the first-line tool to assess LA size and function. Left atrial volume index (LAVI) and peak atrial longitudinal strain (PALS) are among the strongest predictors of AF recurrence and thromboembolism. ^,,,,, Reduced LA strain reflects fibrosis and impaired compliance.

Strengths: dynamic, real-time functional data.

Limitations: operator-dependent, geometry assumptions, rhythm-dependent measurements (sinus rhythm vs AF).

CT allows accurate volumetric assessment and characterization of LA morphology. Increased LA wall thickness and sphericity are associated with recurrence, while epicardial adipose tissue indicates local inflammation. ^,,,,

Strengths: high spatial resolution.

Limitations: radiation exposure, limited functional information, rhythm-dependent measurements (sinus rhythm vs AF).

CMR provides the gold standard for noninvasive fibrosis quantification using late gadolinium enhancement (LGE). The Utah classification and DECAAF studies established the prognostic relevance of fibrosis burden for ablation outcomes. ^,,, Percentage distribution of LA fibrosis across atrial walls as assessed by LGE-CMR, based on the study by Benito et al is illustrated in Figure 1 .

Percentage distribution of left atrial fibrosis across atrial walls as assessed by LGE-CMR (based on the study by Benito et al ).

Strengths: direct fibrosis visualization.

Limitations: availability, cost, gadolinium use, rhythm-dependent measurements (sinus rhythm vs AF).

Intracardiac electrograms recorded during ablation provide complementary information to surface ECG by directly characterizing the atrial substrate. Low-voltage and fractionated signals reflect fibrosis and conduction heterogeneity, correlating with impaired mechanical function and higher recurrence risk. Recent data from Starek et al demonstrated that electrogram complexity and voltage reduction during ablation predict AF recurrence and postprocedural stiff left atrial syndrome (SLAS).

Strengths: Real-time identification of arrhythmogenic substrate and direct quantification of electrical remodeling during the procedure.

Limitations: Invasive, affected by rhythm status, catheter contact, and mapping density; interpretation remains operator-dependent and lacks standardized thresholds.

Each imaging or electrophysiologic technique provides complementary insights into atrial remodeling. Combining morphological, mechanical, and electrical parameters enables more precise identification of atrial cardiomyopathy and risk stratification.

Together, these modalities support early identification of atrial cardiomyopathy and guide individualized therapeutic strategies to improve patient outcomes. Key methods and parameters for assessing left atrial function are summarized in Tables 1 and 2 .

Pulmonary vein isolation (PVI) is a well-established treatment for AF, particularly its paroxysmal form, and can be effectively performed using various ablation techniques. Although clinical outcomes are generally comparable across methods, PFA appears to offer a lower risk of complications, such as pulmonary vein stenosis, atrio-esophageal fistula, or phrenic nerve injury, due to its tissue selectivity. The primary goal of PVI is to achieve durable electrical isolation between the pulmonary veins and the LA.

AF is closely associated with progressive structural and functional remodeling of the LA, including dilation, impaired contractility, altered reservoir function, and eventual fibrotic transformation. ^,, These changes contribute not only to arrhythmia maintenance, but also to hemodynamic compromise, heart failure, and increased thromboembolic risk. ^, The reversal or stabilization of these adverse processes following successful rhythm control is thus of clinical relevance beyond arrhythmia suppression alone. Evidence suggests that PVI may induce beneficial mechanical and hemodynamic remodeling of the LA.

Several studies have demonstrated significant reductions in left atrial volume (LAV) and improvement in LA function parameters following ablation, particularly in patients who maintain sinus rhythm. ^, This reverse remodeling likely reflects a combination of decreased atrial pressure, restoration of atrial contraction, and interruption of maladaptive neurohormonal signaling. Furthermore, successful ablation has been associated with decreased plasma levels of B-type natriuretic peptide (BNP), a biomarker reflecting atrial wall stress and stretch.

The dual nature of ablation effects represents a fundamental paradox in atrial remodeling. While lesion creation inevitably destroys myocardial tissue and can impair local compliance, the overall physiological goal is to restore coordinated atrial contraction, reduce pressure overload, and prevent further maladaptive dilation. Successful rhythm restoration often outweighs the local loss of tissue integrity, leading to improved mechanical efficiency and hemodynamics. Conversely, in patients with advanced atrial disease—characterized by extensive preablation fibrosis, enlarged LA, or long-standing persistent AF—the potential for recovery is limited. ^,, In these cases, ablation may stabilize rather than reverse atrial dysfunction. Moreover, excessive lesion formation may itself lead to SLAS impaired compliance. Therefore, the net effect of ablation reflects a dynamic balance between injury and recovery, highly dependent on the baseline degree of atrial remodeling.

Notably, the scar identified intraoperatively by electroanatomical mapping (EAM)- defined as areas of very low voltage (<0.01–0.1 mV)- does not always correlate with fibrotic tissue as visualized by LGE on CMR imaging (CMR). This discrepancy underscores the evolving and sometimes unpredictable nature of postablation atrial remodeling. The dynamic interplay between fibrosis, volume changes, and functional recovery remains an area of active investigation. Understanding how PVI influences LA mechanics and hemodynamics is not only crucial for optimizing procedural outcomes but also for refining patient selection, predicting recurrence, and assessing long-term cardiovascular risk.

In the following sections, we explore the specific mechanical and hemodynamic changes in the LA following PVI, as assessed across different ablation strategies- including RF, CBA, PFA, and surgical techniques. Rather than focusing on detailed procedural aspects, we aim to compare the broader physiological consequences of achieving PVI by various means, with particular attention to how each method may influence atrial remodeling, function, and long-term clinical outcomes.

RFCA is conducted using a point-by-point technique to achieve durable PVI. Two main approaches are used for PVI: ostial isolation of the pulmonary veins and wide antral pulmonary vein isolation (WACA). In a meta-analysis comparing these 2 methods, PVI performed using the wide antral approach was found to be more effective than ostial PVI in achieving long-term freedom from total atrial tachyarrhythmia recurrence.

Recently, Peters et al reported that patients with a larger RFCA-induced scar volume in the right inferior pulmonary vein region experienced a lower rate of AF recurrence compared to those with a smaller scar volume in the same area. A meta-analysis of 17 studies, including 869 patients, investigated also the impact of RF ablation on the LA. The findings confirmed that, following the procedure, both LA diameter and LAVI were reduced. The effectiveness of the procedure significantly influenced these outcomes. In patients who experienced arrhythmia recurrence, these dimensions remained unchanged. Moreover, in this same group, a reduction in the ejection fraction of both the left atrial appendage (LAAEF) and the LA (LAEF) was observed. On the other hand, in patients without arrhythmia recurrence, no changes in LA function (LAAEF and LAEF) were noted, whereas a significant reduction in atrial size was observed (LAD and LAVI).

Other study raised the question of whether all patients are responders to positive remodeling following RFCA ablation. In this study, patients were classified as responders if their LA volume decreased by 15% or more approximately 13 months after catheter ablation. About 63% of patients met this criterion. Responders had a significantly higher baseline LA strain (19±8%) compared to nonresponders (14% ± 6%; p <0.001). This indicates that patients with better atrial function before ablation were more likely to show reverse remodeling after the procedure. It is assumed that not everyone could benefit with catheter ablation in the same way.

Attempts have been made to assess the short-term impact of ablation on LA mechanical function. In an analysis including 113 patients with both paroxysmal and persistent AF, LA strain was evaluated using MRI. The results indicated that acute impairment of mechanical function occurred within 24 hours postprocedure. Additionally, in 95% of patients, functional recovery to baseline values was observed within 11 days. This effect persisted at the 3-month follow-up. On the other hand, several analyses and clinical studies have explored the potential adverse impact of catheter ablation- particularly extensive LA ablation- on atrial mechanical and hemodynamic function. Of particular concern is the development of SLAS a condition characterized by impaired atrial compliance, elevated LA pressures, and exercise intolerance, which may occur as a consequence of extensive atrial scarring. Wylie et al found that an excessive amount of scar tissue was associated with a reduction in LAEF in the short term after ablation. Moreover, they reported a positive correlation between the extent of scar formation and the progressive decline in LA mechanical function. Gibson et al were the first to prospectively investigate the occurrence of SLAS in patients undergoing catheter ablation. In their study, pulmonary hypertension (PH) was identified based on the presence of prominent V-waves (>7 mm) recorded on pulmonary capillary wedge pressure (PCWP) or direct LA pressure tracings, with cases of mitral regurgitation carefully excluded. Their findings indicated that approximately 1.4% of patients developed PH secondary to impaired atrial diastolic function following ablation. Notably, this diastolic dysfunction was closely linked to an increased burden of atrial scarring. Interestingly, both LA and left ventricular systolic performance remained preserved despite these changes.

Beyond these hemodynamic and neurohumoral factors, several clinical predictors of SLAS following RFCA have been identified. Independent risk factors include a LA diameter under 45 mm, the presence of diabetes mellitus, obstructive sleep apnea (OSA), and elevated baseline LA pressures. Together, these findings emphasize the multifactorial nature of atrial remodeling and dysfunction after ablation procedures. This suggests that the restoration of LA function following RFCA is a multifaceted process that depends on achieving an optimal balance of LA scarring, reestablishing sinus rhythm, and/or reducing AF burden. It remains challenging to determine whether the decline in LA function among patients with AF recurrence post-RFCA is due to the persistent presence of AF (including any occurrence or a certain level of AF burden) or the formation of excessive scar tissue as a result of the RFCA procedure.

The CBA is a double layer balloon that is introduced into the LA via a steerable sheath. CBA is an alternative energy source that utilizes liquid nitrous oxide, which is delivered under pressure within a balloon to induce freezing of the surrounding tissue. On the market there are several manufacures that implement this technology and also there are a few sizes of balloon that could fit the demands of different LA sizes. Due to the widespread availability of both CBA and RF ablation on the market for many years, these techniques are frequently compared.

Two studies have analyzed the differences between these methods in terms of their effects on the mechanical properties of connective tissues, including tendons and cardiac tissue. In the first study, porcine tendon tissue was examined, while in the second study, both porcine and human cardiac tissues were analyzed. In both studies, a statistically significant reduction in stiffness and tensile strength was observed in the RF ablation group. The authors reported that thermal injury from RF ablation at temperatures exceeding 65°C induces collagen denaturation, leading to reduced structural integrity, while CBA exerts minimal effects on structural proteins and tensile strength. The extent of biomechanical changes following both ablation modalities was further influenced by tissue type and species-specific properties.

Baran et al investigated the immediate hemodynamic and tissue effects of CBA in patients with AF. They found that the procedure caused a significant acute increase in pulmonary venous and LA pressures, along with transient tissue edema and structural changes in the pulmonary veins, suggesting temporary hemodynamic impairment immediately after ablation.

Assessment of the scar tissue formed, following CBA is also of clinical importance. Meaningful consideration is the optimal timing for assessing the maturation of ablation-induced scar tissue and the resolution of procedurerelated edema. Moreover, it is particularly crucial to ensure that the ablation scar forms a continuous circumferential lesion around the pulmonary veins, a factor that can be effectively assessed using LGE magnetic resonance imaging (LGE-MRI).

Other studies analyzed hemodynamical function of CBA. Canpolat et al observed that successful CBA in paroxysmal AF, led to improved electrical conduction in the LA and a reduction in the LAVI. However, this remodeling effect was only seen in patients who remained free of AF recurrence, while those with recurrence did not experience improvements. In a retrospective cohort of 192 matched patients with paroxysmal AF, both CBA and RFA led to significant electrical and structural reverse remodeling of the LA- measured by reductions in P-wave dispersion, LA diameter, and LAVI- at 1, 2, and 3 years postprocedure. Notably, at 6 months, the CBA group showed larger improvements in these parameters compared to RFA, though this advantage diminished over the long term. In CRYO-LAEF study authors compared CBA to RFCA and the change in LAEF after 1 and 3 months after ablation. They found that there were significantly higher number of patients with increased LAEF in CBA group after 1 and 3 months. The study also revealed that patients with decreased LAEF after ablation had a 6.5 higher chance of AF recurrence in a follow-up.

Important factor is also LA stunning which is often observed after restoration of sinus rhythm in AF and could last longer and requires a longer follow-up. A randomized study comparing RFA, CBA, and 3D mapping-guided CBA showed that all techniques led to transient impairment in atrial contractility within the first 3 months postprocedure, with gradual recovery over time. Importantly, no significant differences in the long-term functional outcomes between the ablation strategies were observed within a year. These findings suggest that while LA stunning is a common early consequence of ablation, the choice of technique may not influence long-term atrial performance.

PFA employs high-intensity electrical pulses to induce nonthermal irreversible electroporation, resulting in selective cardiac myocyte death. Emerging evidence suggests that PFA offers efficacy comparable to conventional catheter ablation while minimizing the risk of thermally mediated complications.

Although PFA is classified as a nonthermal technique, experimental and clinical data indicate that limited thermal effects may occur, depending on the total energy delivered and peak voltage, without leading to the collateral tissue injury typically associated with conventional thermal ablation. ^, PFA results in lesion formation with minimal long-term fibrosis, distinguishing it from conventional thermal ablation techniques. While thermal ablation often induces excessive fibrotic remodeling due to inflammatory responses and microvascular injury, PFA maintains the structural integrity of the extracellular matrix, reducing these adverse effects. This distinct healing mechanism is proposed to limit collagen deposition, potentially preserving tissue elasticity and promoting better restoration of LA mechanical function over time.

Evidence regarding the impact of PFA on LA hemodynamic and mechanical function remains limited.

To date, only a limited number of studies have evaluated the effects of PFA on LA mechanical and hemodynamic function. Mahrous et al reported a significant improvement in PALS following PFA, with more pronounced benefits observed in patients with preprocedural sinus rhythm and paroxysmal AF. Additionally, comparative imaging studies have shown that PFA produces more homogeneous acute LGE lesions, most of which resolve during long-term follow-up, without evidence of microvascular injury or intramural hemorrhage when compared with RFCA.

Although early studies consistently demonstrate favorable safety and preservation of LA compliance after PFA, current evidence is limited to short-term follow-up and relatively small cohorts. Long-term data on structural remodeling, atrial strain recovery, and clinical outcomes are still lacking. Further prospective studies with standardized imaging and extended observation are needed to establish the true impact of PFA on atrial mechanical and hemodynamic function.