Effect of fibrosis regionality on atrial fibrillation recurrence: insights from DECAAF II

Characterization of arrhythmia-induced cardiomyopathy using magnetic resonance imaging in patients with persistent atrial fibrillation and left ventricular systolic dysfunction - insights from DECAAF II

AIMS

Atrial fibrillation (AF) ablation in heart failure reduces mortality and hospitalizations and improves ejection fraction. Arrhythmia-induced cardiomyopathy (AIC) is diagnosed after complete recovery of left ventricular systolic function after ablation. We aimed to identify the prevalence and pre-ablation predictors of AIC among patients with AF and left ventricular systolic dysfunction (LVSD).

METHODS AND RESULTS

We utilized the DECAAF II database, where 815 patients with persistent AF underwent late gadolinium enhancement cardiac magnetic-resonance imaging (LGE-CMR) before and 3 months after AF ablation. We only included patients with available left ventricular ejection fraction (LVEF) and LVSD. AF burden was continuously monitored. AIC was defined as LVSD and coexisting AF in patients with ejection fraction improvement to ≥50% following ablation. We identified 119 patients with LVSD and AF with a mean LVEF of 39.1 ± 7.8% and mean baseline fibrosis of 20.0 ± 7.3%. Mean AF burden post-ablation was 16.8 ± 20.2%, and mean LVEF recovery was 13.9 percentage points. Seventy-two patients (60.5%) fulfilled the criteria for AIC, and 47 (39.5%) did not. AIC patients had a mean baseline LVEF of 39.1 ± 7.9% (vs. 39.2 ± 7.9% in non-AIC patients; p = 0.9), a significantly lower percentage of fibrosis in the left atrial septal wall (12.2 ± 10.0% vs. 20.7 ± 11.4% in non-AIC patients, p < 0.001). Additionally, LVEF improvement was correlated with lower AF burden post-ablation (r = -0.23, p = 0.02).

CONCLUSIONS

In this post-hoc analysis of the DECAAF II trial, we found that the majority of patients with LVSD and persistent AF have AIC rather than primary cardiomyopathy. We identified LGE-CMR as a differentiator between AIC and other cardiomyopathies.

Persistent atrial fibrillation with left atrial low-voltage area: who benefit from additional modification?

AIMS

The presence of low-voltage areas (LVAs) is associated with increased recurrence rate following ablation of persistent atrial fibrillation (PeAF). However, the benefit of additional LVA modification remains controversial. This substudy of the STABLE-SR-II trial aims to explore the factors that influence the benefit of additional LVA ablation for PeAF patients with LVAs.

METHODS AND RESULTS

In the STABLE-SR-II trial, PeAF patients with de novo ablation were randomized to receive either circumferential pulmonary vein isolation (CPVI, CPVI-alone group) or CPVI plus LVA ablation (CPVI-plus group). Patients with LVAs were included and analyzed in this substudy. The primary outcome was freedom from atrial arrhythmias 18 months after a single ablation procedure. LVAs were detected in 133 out of 276 PeAF patients (48%). Age and LVA burden were potential factors influencing the relative success of additional LVA ablation compared with CPVI alone in the univariable analysis. In multi-adjusted models, significant benefit from additional LVA ablation was found in patients aged ≥65 years [n = 50, hazard ratio (HR) 0.14, 95% confidence interval (CI) 0.02-0.83] or with LVA burden ≥ 15% (n = 18, HR 0.01, 95% CI: 0-0.44). LVA burden ≥15% was observed in 10 of 50 patients aged ≥65 years (20%) and in 8 of 83 patients aged <65 years (10%). Combined subgroup analysis demonstrated that LVA ablation was particularly beneficial for patients aged ≥65 years, regardless of LVA burden.

CONCLUSION

LVA ablation following CPVI may provide additional benefits for older PeAF patients (≥65 years) in the first procedure.

CLINICAL TRIAL REGISTRATION

NCT03448562 [CPVI Alone Versus CPVI Plus Electrophysiological Substrate Ablation in the LA During SR for the Treatment of Non-PAF (STABLE-SR_II)].

Recurrence and non-improvement of European Heart Rhythm Association symptom scores after atrial fibrillation ablation: the role of left atrial fractal dimension

Background

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia. Atrial remodeling often leads to impaired clinical outcomes after AF ablation. Understanding the factors influencing AF recurrence after ablation is crucial for improving patient prognosis. This study aimed to investigate the relationship between left atrial (LA) morphologic heterogeneity, quantified by fractal dimension (FD), and AF recurrence, as well as the impact on European Heart Rhythm Association (EHRA) symptom scores following ablation.

Methods

This study retrospectively collected the data of patients with AF who underwent their first radiofrequency ablation procedure at Lanzhou University Second Hospital between October 2019 and September 2022 and underwent cardiac computed tomography angiography (CTA) within 3 days before the procedure. Patients with less than 1 year of follow-up or those who did not meet the inclusion criteria were excluded from the analysis. On the cardiac CTA images, we calculated the FD of each patient's LA using fractal analysis. Cox proportional risk models were used to calculate the risk ratios for predictors of AF recurrence and for predictors of EHRA symptom score non-improvement.

Results

A total of 512 patients with AF were included with a median follow-up of 29 (range, 18-37) months, of which 349 had paroxysmal AF and 163 had persistent AF, 341 were male and 171 were female, 146 had recurrence of AF and 366 did not have recurrence, and 48 had improvement of EHRA symptoms and 98 did not have improvement. Cox regression analysis showed that LA-FD was an independent predictor of recurrence [hazard ratio (HR) =16.056, 95% confidence interval (CI): 7.493-34.406, P<0.001] and non-improvement in EHRA symptom score (HR =10.500, 95% CI: 3.086-35.728, P<0.001) after AF ablation. In patients with paroxysmal and persistent AF, LA-FD (HR =21.750, 95% CI: 8.533-55.444, P<0.001; HR =7.291, 95% CI: 1.977-26.896, P<0.05) is also an independent predictor of recurrence after AF ablation. Furthermore, patients with a larger LA-FD (>1.208) had a higher incidence of AF recurrence and EHRA symptom score non-improvement than those with a smaller LA-FD (<1.208, P<0.05).

Conclusions

A larger LA-FD (>1.208) on cardiac CTA could be a predictor for adverse LA remodeling and was independently associated with recurrence and non-improvement of the EHRA symptom score after AF ablation.

Aggressive ablation vs. regular ablation for persistent atrial fibrillation: a multicentre real-world cohort study

AIMS

Current guidelines for the optimal ablation strategy for persistent atrial fibrillation (PerAF) remain unclear. While our previous RCT confirmed the favourable prognosis of aggressive ablation, real-world evidence is still lacking.

METHODS AND RESULTS

Among 4833 PerAF patients undergoing catheter ablation at 10 centres, two groups were defined: regular ablation (PVI-only or PVI plus anatomical ablation) and aggressive ablation (anatomical plus electrogram-guided ablation), with 1560 patients each after propensity score (PS) matching. The primary endpoint was 12-month AF/atrial tachycardia (AT) recurrence-free survival off anti-arrhythmic drugs after a single procedure. Additional PS matching was performed within the regular group between PVI-only and anatomical ablation (n = 455 each). Furthermore, anatomical ablation from the regular group was independently matched with aggressive ablation (n = 1362 each). At 12 months, the aggressive group showed superior AF/AT-free survival (66.2% vs. 59.3%, P < 0.001; HR 0.745), similar AT recurrence (12.0% vs. 11.3%, P = 0.539), and significantly higher procedural AF termination (67.0% vs. 21.0%, P < 0.001) than regular group. Moreover, patients with AF termination had improved AF/AT-free survival (72.3% vs. 55.2%, P < 0.001). Safety endpoints did not differ significantly between the two groups. Both the ablation outcomes and AF termination rate showed increasing trends with the extent of ablation aggressiveness but declined with extremely aggressive ablation. After additional PS matching, within the regular group, no statistical differences were observed though AF/AT-free survival in the anatomical group was slightly higher than the PVI-only group (60.7% vs. 55.6%, P = 0.122); while aggressive ablation showed improved AF/AT-free survival compared to anatomical ablation alone from regular group (67.5% vs. 59.9%, P < 0.001).

CONCLUSION

Aggressive ablation achieved more favourable outcomes than regular ablation, and moderately aggressive ablation may be associated with better clinical outcomes. AF termination is a reliable ablation endpoint.

Application of artificial intelligence to analyze data from randomized controlled trials: An example from DECAAF II

BACKGROUND

Causal machine learning (ML) provides an efficient way of identifying heterogeneous treatment effect groups from hundreds of possible combinations, especially for randomized trial data.

OBJECTIVE

The aim of this paper is to illustrate the potential of applying causal ML on the DECAAF II trial data. We proposed a causal ML model to predict the treatment response heterogeneity.

METHODS

We applied causal tree learning to the DECAAF II trial data as an example of real applications, identifying subgroups that may be superior when subject to one of the treatments over the other through an easily interpretable process. For each subgroup identified, the characteristics were summarized, and the relationship between treatment arms and risk for recurrence of atrial tachyarrhythmia (aTA) among subjects was assessed.

RESULTS

Causal tree learning demonstrated that, among all the preablation predictors, dividing subgroups according to age, with a cutoff of 58 years, provides the most heterogeneous subgroups in response to fibrosis-guided ablation in addition to pulmonary vein isolation (PVI) compared with PVI alone. The difference in the risk of recurrence of aTA between 2 treatments was nonsignificant in older patients (hazard ratio [HR] 1.06; 95% confidence interval [CI] 0.77-1.47; P = .72). However, among the younger patients, the risk of aTA recurrence was significantly lower in the fibrosis-guided ablation group compared with PVI-only (HR 0.50; 95% CI 0.28-0.90); P = .02).

CONCLUSION

Applying causal ML on random controlled trial datasets helped us identify groups of patients that profited from the treatment of interest in an efficient and unbiased manner.

Evolution in electrophysiology 100 years after Einthoven: translational and computational innovations in rhythm control of atrial fibrillation

In 1924, the Dutch physiologist Willem Einthoven received the Nobel Prize in Physiology or Medicine for his discovery of the mechanism of the electrocardiogram (ECG). Anno 2024, the ECG is commonly used as a diagnostic tool in cardiology. In the paper 'Le Télécardiogramme', Einthoven described the first recording of the now most common cardiac arrhythmia: atrial fibrillation (AF). The treatment of AF includes rhythm control, aiming to alleviate symptoms and improve quality of life. Recent studies found that early rhythm control might additionally improve clinical outcomes. However, current therapeutic options have suboptimal efficacy and safety, highlighting a need for better rhythm-control strategies. In this review, we address the challenges related to antiarrhythmic drugs (AADs) and catheter ablation for rhythm control of AF, including significant recurrence rates and adverse side effects such as pro-arrhythmia. Furthermore, we discuss potential solutions to these challenges including novel tools, such as atrial-specific AADs and digital-twin-guided AF ablation. In particular, digital twins are a promising method to integrate a wide range of clinical data to address the heterogeneity in AF mechanisms. This may enable a more mechanism-based tailored approach that may overcome the limitations of previous precision medicine approaches based on individual biomarkers. However, several translational challenges need to be addressed before digital twins can be routinely applied in clinical practice, which we discuss at the end of this narrative review. Ultimately, the significant advances in the detection, understanding, and treatment of AF since its first ECG documentation are expected to help reduce the burden of this troublesome condition.

Atrial fibrillation substrate and impaired left atrial function: a cardiac MRI study

AIMS

Structural and fibrotic remodelling is a well-known contributor to the atrial fibrillation (AF) substrate. Epicardial adipose tissue (EAT) is increasingly recognized as a contributor through electrical remodelling in the atria. We aimed to assess the association of LA fibrosis and EAT with LA strain and function using cardiac magnetic resonance (CMR) imaging in patients with AF.

METHODS AND RESULTS

LA fibrosis was assessed using late gadolinium enhancement CMR, LA EAT was assessed using the fat-water separation Dixon sequence, and feature tracking was applied to assess global longitudinal strain in its three components [reservoir (GLRS), conduit (GLCdS), and contractile (GLCtS)]. LA emptying fraction and LA volume were measured using the cine sequences. All CMR images were acquired in sinus rhythm. One hundred one AF patients underwent pre-ablation CMR (39% female, average age 62 years). LA fibrosis was negatively associated with the three components of global longitudinal strain (GLRS: R = -0.35, P < 0.001; GLCdS: R = -0.24, P = 0.015; GLCtS: R = -0.2, P = 0.046). Out of the different sections of the LA, fibrosis in the posterior and lateral walls was most negatively correlated with GLRS (R = -0.32, P = 0.001, and R = -0.33, P = 0.001, respectively). LA EAT was negatively correlated with GLCdS (R = -0.453, P < 0.001). LA fibrosis was negatively correlated with LA emptying fraction but LA EAT was not (R = -0.27, P = 0.007, and R = -0.22, P = 0.1, respectively). LA EAT and fibrosis were both positively correlated with LA volume (R = 0.38, P = 0.003, and R = 0.24, P = 0.016, respectively).

CONCLUSION

LA fibrosis, a major component of the AF substrate, and EAT, an important contributor, are associated with a worsening LA function through strain analysis by CMR.

Relationships between biatrial substrate and recurrence after radiofrequency ablation in patients with persistent atrial fibrillation

BACKGROUND

Global longitudinal strain (GLS) and atrial voltage are acknowledged markers for worse rhythm outcome after ablation of persistent atrial fibrillation (PeAF). The majority of research efforts have been directed towards the left atrium (LA), with relatively fewer studies focusing on the right atrium (RA). The aim of this study was to investigate the effect of the biatrial substrate on the outcome following radiofrequency catheter ablation (RFCA).

METHODS

All patients underwent two-dimensional speckle tracking echocardiography (2D-STE) and high-density mapping (HDM) on LA and RA in preoperative and postoperative stages of RFCA. Atrial substrate was assessed by GLS, average voltage, and low voltage zone (LVZ).

RESULTS

This retrospective study enrolled 48 patients. With a follow-up of 385.98 ± 161.78 days, 22.92% (11/48) of all patients had AF recurrence and 63.64% in low strain group. Left atrial-low voltage zone (LA-LVZ) prior to RFCA was 67.52 ± 15.27% and 54.21 ± 20.07%, respectively, in the recurrence group and non-recurrence group. Multivariate regression analysis showed that preoperative LA-GLS (OR 0.047, 95%CI 0.002-0.941, p = .046) was independent predictors of AF recurrence. Biatrial average voltage in preoperative and postoperative stages were positively correlated (preoperative: r = 0.563 p < .001; postoperative: r = 0.464 p = .002). There was no significant difference in the proportion of RA in the recurrence group except the septum in preoperative and postoperative stages.

CONCLUSIONS

Low LA-GLS and high LA-LVZ may be predictors of RFCA recurrence in PeAF patients. Biatrial average voltage were positively correlated in preoperative and postoperative stages.

Factors predicting the recurrence of atrial fibrillation after catheter ablation: A review

Atrial fibrillation (AF) is the most common and clinically significant type of cardiac arrhythmia. Although catheter ablation (CA) can restore sinus rhythm in patients with AF, some patients experience recurrence after the procedure. This requires us to find a simple and effective way to identify patients at a high risk of recurrence and to intervene early in the high-risk population to improve patient prognosis. The mechanism of AF recurrence is unclear, but it involves several aspects including patient history, inflammation, myocardial fibrosis, and genes. This article summarizes the current predictors of AF recurrence after CA, including myocardial fibrosis markers, inflammatory markers, MicroRNAs, Circular RNAs, AF recurrence scores, and imaging indicators. Each predictor has its own scope of application, and the predictive capacity and joint application of multiple predictors may improve the predictive power. In addition, we summarize the mechanisms involved in AF recurrence. We hope that this review will assist researchers understand the current predictors of AF recurrence and help them conduct further related studies.

Pre- and post-procedural cardiac imaging (computed tomography and magnetic resonance imaging) in electrophysiology: a clinical consensus statement of the European Heart Rhythm Association and European Association of Cardiovascular Imaging of the European Society of Cardiology

Imaging using cardiac computed tomography (CT) or magnetic resonance (MR) imaging has become an important option for anatomic and substrate delineation in complex atrial fibrillation (AF) and ventricular tachycardia (VT) ablation procedures. Computed tomography more common than MR has been used to detect procedure-associated complications such as oesophageal, cerebral, and vascular injury. This clinical consensus statement summarizes the current knowledge of CT and MR to facilitate electrophysiological procedures, the current value of real-time integration of imaging-derived anatomy, and substrate information during the procedure and the current role of CT and MR in diagnosing relevant procedure-related complications. Practical advice on potential advantages of one imaging modality over the other is discussed for patients with implanted cardiac rhythm devices as well as for planning, intraprocedural integration, and post-interventional management in AF and VT ablation patients. Establishing a team of electrophysiologists and cardiac imaging specialists working on specific details of imaging for complex ablation procedures is key. Cardiac magnetic resonance (CMR) can safely be performed in most patients with implanted active cardiac devices. Standard procedures for pre- and post-scanning management of the device and potential CMR-associated device malfunctions need to be in place. In VT patients, imaging-specifically MR-may help to determine scar location and mural distribution in patients with ischaemic and non-ischaemic cardiomyopathy beyond evaluating the underlying structural heart disease. Future directions in imaging may include the ability to register multiple imaging modalities and novel high-resolution modalities, but also refinements of imaging-guided ablation strategies are expected.

Assessing left atrial intramyocardial fat infiltration from computerized tomography angiography in patients with atrial fibrillation

AIMS

Epicardial adipose tissue might promote atrial fibrillation (AF) in several ways, including infiltrating the underlying atrial myocardium. However, the role of this potential mechanism has been poorly investigated. The aim of this study is to evaluate the presence of left atrial (LA) infiltrated adipose tissue (inFAT) by analysing multi-detector computer tomography (MDCT)-derived three-dimensional (3D) fat infiltration maps and to compare the extent of LA inFAT between patients without AF history, with paroxysmal, and with persistent AF.

METHODS AND RESULTS

Sixty consecutive patients with AF diagnosis (30 persistent and 30 paroxysmal) were enrolled and compared with 20 age-matched control; MDCT-derived images were post-processed to obtain 3D LA inFAT maps for all patients. Volume (mL) and mean signal intensities [(Hounsfield Units (HU)] of inFAT (HU -194; -5), dense inFAT (HU -194; -50), and fat-myocardial admixture (HU -50; -5) were automatically computed by the software. inFAT volume was significantly different across the three groups (P = 0.009), with post-hoc pairwise comparisons showing a significant increase in inFAT volume in persistent AF compared to controls (P = 0.006). Dense inFAT retained a significant difference also after correcting for body mass index (P = 0.028). In addition, more negative inFAT radiodensity values were found in AF patients. Regional distribution analysis showed a significantly higher regional distribution of LA inFAT at left and right superior pulmonary vein antra in AF patients.

CONCLUSION

Persistent forms of AF are associated with greater degree of LA intramyocardial adipose infiltration, independently of body mass index. Compared to controls, AF patients present higher LA inFAT volume at left and right superior pulmonary vein antra.

Catheter ablation approach and outcome in HIV+ patients with recurrent atrial fibrillation

INTRODUCTION

Earlier studies have shown a clear association between severity of human immunodeficiency virus (HIV) infection and incident atrial fibrillation (AF). We present the long-term outcome of catheter ablation (CA) and electrophysiological characteristics in HIV+ AF patients.

METHODS

This study evaluated 1438 consecutive AF patients [31 (2.15%) with HIV and 1407 (97.8%) without HIV diagnosis] undergoing their first CA at our center. A total of 31 HIV patients and 31 controls were generated by propensity matching, based on calculated risk factor scores, using a logistic model. During first procedure, all received isolation of pulmonary vein (PV) + posterior wall and superior vena cava. Non-PV triggers, defined as ectopic triggers originating from sites other than PVs, were identified at the redo ablation with high-dose isoproterenol challenge.

RESULTS

Clinical characteristics were not different between the groups. When compared to the control, by the end of 5 years after the first procedure, recurrence was significantly greater in HIV group [100% vs. 54%, p < .001]. Among patients that underwent redo ablation non-PV triggers were higher in HIV group [93.5% vs. 54%, p < .001], and most frequently originated from the coronary sinus [67.7% vs. 45.2%, p < .001] and left atrial appendage [41.9% vs. 25.8%, p < .001]. After focal ablation of non-PV trigger, no difference in arrhythmia recurrence between two groups [80.6% vs. 87.1%, p = .753] at 1-year follow up was found.

CONCLUSION

Our findings suggest that non-PV triggers are highly prevalent in HIV+ AF patients resulting in higher rate of the mid- and long-term arrhythmia recurrence.

Effect of fibrosis regionality on atrial fibrillation recurrence: insights from DECAAF II

AIMS

The amount of fibrosis in the left atrium (LA) predicts atrial fibrillation (AF) recurrence after catheter ablation (CA). We aim to identify whether regional variations in LA fibrosis affect AF recurrence.

METHODS AND RESULTS

This post hoc analysis of the DECAAF II trial includes 734 patients with persistent AF undergoing first-time CA who underwent late gadolinium enhancement magnetic resonance imaging (LGE-MRI) within 1 month prior to ablation and were randomized to MRI-guided fibrosis ablation in addition to standard pulmonary vein isolation (PVI) or standard PVI only. The LA wall was divided into seven regions: anterior, posterior, septal, lateral, right pulmonary vein (PV) antrum, left PV antrum, and left atrial appendage (LAA) ostium. Regional fibrosis percentage was defined as a region's fibrosis prior to ablation divided by total LA fibrosis. Regional surface area percentage was defined as an area's surface area divided by the total LA wall surface area before ablation. Patients were followed up for a year with single-lead electrocardiogram (ECG) devices. The left PV had the highest regional fibrosis percentage (29.30 ± 14.04%), followed by the lateral wall (23.23 ± 13.56%), and the posterior wall (19.80 ± 10.85%). The regional fibrosis percentage of the LAA was a significant predictor of AF recurrence post-ablation (odds ratio = 1.017, P = 0.021), and this finding was only preserved in patients receiving MRI-guided fibrosis ablation. Regional surface area percentages did not significantly affect the primary outcome.

CONCLUSION

We have confirmed that atrial cardiomyopathy and remodelling are not a homogenous process, with variations in different regions of the LA. Atrial fibrosis does not uniformly affect the LA, and the left PV antral region has more fibrosis than the rest of the wall. Furthermore, we identified regional fibrosis of the LAA as a significant predictor of AF recurrence post-ablation in patients receiving MRI-guided fibrosis ablation in addition to standard PVI.