Regression of Diffuse Ventricular Fibrosis Following Restoration of Sinus Rhythm With Catheter Ablation in Patients With Atrial Fibrillation and Systolic Dysfunction

[Atrial fibrillation and heart failure]

Atrial fibrillation and heart failure are among the most common cardiovascular diseases and have a significant impact on the mortality and morbidity of affected patients. From a pathophysiological perspective, the two diseases are closely related and often perpetuate each other. Therefore, effective management of atrial fibrillation is now a central component of modern heart failure treatment. Based on current data, sinus rhythm should primarily be permanently maintained in patients with systolic heart failure. Catheter ablation has recently proven to be advantageous over purely pharmacological therapy and is therefore the treatment of choice for many patients with heart failure and atrial fibrillation. In patients with diastolic heart failure (heart failure with preserved ejection fraction [HFpEF]), the effect of catheter ablation is less clear. Data from randomized studies are urgently needed in order to further assess efficacy in this population.

Chinese guidelines for the diagnosis and management of atrial fibrillation

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, significantly impacting patients' quality of life and increasing the risk of death, stroke, heart failure, and dementia. Over the past two decades, there have been significant breakthroughs in AF risk prediction and screening, stroke prevention, rhythm control, catheter ablation, and integrated management. During this period, the scale, quality, and experience of AF management in China have greatly improved, providing a solid foundation for the development of the guidelines for the diagnosis and management of AF. To further promote standardized AF management, and apply new technologies and concepts to clinical practice timely and fully, the Chinese Society of Cardiology of Chinese Medical Association and the Heart Rhythm Committee of Chinese Society of Biomedical Engineering jointly developed the Chinese Guidelines for the Diagnosis and Management of Atrial Fibrillation. The guidelines comprehensively elaborated on various aspects of AF management and proposed the CHA2DS2‑VASc‑60 stroke risk score based on the characteristics of the Asian AF population. The guidelines also reevaluated the clinical application of AF screening, emphasized the significance of early rhythm control, and highlighted the central role of catheter ablation in rhythm control.

Chinese Guidelines for the Diagnosis and Management of Atrial Fibrillation

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, significantly impacting patients' quality of life and increasing the risk of death, stroke, heart failure, and dementia. Over the past two decades, there have been significant breakthroughs in AF risk prediction and screening, stroke prevention, rhythm control, catheter ablation, and integrated management. During this period, the scale, quality, and experience of AF management in China have greatly improved, providing a solid foundation for the development of guidelines for the diagnosis and management of AF. To further promote standardized AF management, and apply new technologies and concepts to clinical practice in a timely and comprehensive manner, the Chinese Society of Cardiology of the Chinese Medical Association and the Heart Rhythm Committee of the Chinese Society of Biomedical Engineering have jointly developed the Chinese Guidelines for the Diagnosis and Management of Atrial Fibrillation. The guidelines have comprehensively elaborated on various aspects of AF management and proposed the CHA2DS2-VASc-60 stroke risk score based on the characteristics of AF in the Asian population. The guidelines have also reevaluated the clinical application of AF screening, emphasized the significance of early rhythm control, and highlighted the central role of catheter ablation in rhythm control.

2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines

AIM

The "2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation" provides recommendations to guide clinicians in the treatment of patients with atrial fibrillation.

METHODS

A comprehensive literature search was conducted from May 12, 2022, to November 3, 2022, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, the Agency for Healthcare Research and Quality, and other selected databases relevant to this guideline. Additional relevant studies, published through November 2022, during the guideline writing process, were also considered by the writing committee and added to the evidence tables, where appropriate.

STRUCTURE

Atrial fibrillation is the most sustained common arrhythmia, and its incidence and prevalence are increasing in the United States and globally. Recommendations from the "2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation" and the "2019 AHA/ACC/HRS Focused Update of the 2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation" have been updated with new evidence to guide clinicians. In addition, new recommendations addressing atrial fibrillation and thromboembolic risk assessment, anticoagulation, left atrial appendage occlusion, atrial fibrillation catheter or surgical ablation, and risk factor modification and atrial fibrillation prevention have been developed.

Immunology of human fibrosis

Fibrosis, defined by the excess deposition of structural and matricellular proteins in the extracellular space, underlies tissue dysfunction in multiple chronic diseases. Approved antifibrotics have proven modest in efficacy, and the immune compartment remains, for the most part, an untapped therapeutic opportunity. Recent single-cell analyses have interrogated human fibrotic tissues, including immune cells. These studies have revealed a conserved profile of scar-associated macrophages, which localize to the fibrotic niche and interact with mesenchymal cells that produce pathological extracellular matrix. Here we review recent advances in the understanding of the fibrotic microenvironment in human diseases, with a focus on immune cell profiles and functional immune-stromal interactions. We also discuss the key role of the immune system in mediating fibrosis regression and highlight avenues for future study to elucidate potential approaches to targeting inflammatory cells in fibrotic disorders.

Outcomes of catheter ablation vs. medical treatment for atrial fibrillation and heart failure: a meta-analysis

Background

The benefit of catheter ablation vs. medical treatment has been reported to be inconsistent in randomized controlled trials (RCTs) for patients with atrial fibrillation (AF) and heart failure (HF) due to different enrollment criteria. This meta-analysis aimed to decipher the differential outcomes stratified by different left ventricular ejection fractions (LVEFs) and AF types.

Methods

We searched PubMed, Embase, ProQuest, ScienceDirect, Cochrane Library, ClinicalKey, Web of Science, and ClinicalTrials.gov databases for RCTs comparing medical treatment and catheter ablation in patients with AF and HF published before March 31, 2023. Nine studies were included.

Results

When patients were stratified by LVEF, improved LVEF and 6-min walk distance, less AF recurrence, and lower all-cause mortality in favor of catheter ablation were observed in patients with LVEF ≤50% but not in patients with LVEF ≤35%, and short HF hospitalization was observed in patients with LVEF ≤50% and LVEF ≤35%. When patients were stratified by AF types, improved LVEF and 6-min walk distance, better HF questionnaire score, and short HF hospitalization in favor of catheter ablation were observed both in patients with nonparoxysmal AF and mixed AF (paroxysmal and persistent) and less AF recurrence and lower all-cause mortality in favor of catheter ablation were observed in only patients with mixed AF.

Conclusions

This meta-analysis showed improved LVEF and 6-min walk distance, less AF recurrence, and lower all-cause mortality in favor of catheter ablation vs. medical treatment in AF patients with HF and LVEF of 36%-50%. Compared with medical treatment, catheter ablation improved LVEF and had better HF status in patients with nonparoxysmal AF and mixed AF; however, AF recurrence and all-cause mortality in favor of catheter ablation were observed in only HF patients with mixed AF.

Atrial Fibrillation Ablation Outcomes and Heart Failure (from the Kansai Plus Atrial Fibrillation Registry)

The impact of rhythm outcomes on heart failure (HF) hospitalizations remains unknown after radiofrequency catheter ablation (RFCA) of atrial fibrillation (AF). We sought to elucidate whether AF recurrence was associated with HF hospitalizations after AF RFCA. We conducted a large-scale, prospective, multicenter, observational study (Kansai Plus Atrial Fibrillation Registry), enrolling 5,010 consecutive patients (age 64 ± 10 years, 27.3% female, and 35.7% nonparoxysmal AF) who underwent an initial AF RFCA at 26 centers. The median follow-up duration was 2.9 years. The cumulative 3-year incidence of HF hospitalizations after the initial RFCA was 1.84% (0.69%/year). Hospitalized patients with HF were older with a higher prevalence of nonparoxysmal AF, renal dysfunction, diabetes, and underlying heart disease pre-RFCA. HF hospitalizations occurred more often in patients with than without recurrences (3.27 vs 0.84%, log-rank p <0.0001). After adjusting for confounders using a Cox model, AF recurrence remained an independent predictor of HF hospitalizations (hazard ratio [HR] 2.84, 95% confidence interval [CI] 1.80 to 4.47, p <0.0001). AF recurrence was a distinct HF hospitalization risk in patients with a left ventricular ejection fraction ≥50% (HR 4.54, 95% CI 2.38 to 8.65, p <0.0001) but not <50% (HR 1.31, 95% CI 0.65 to 2.62, p = 0.45), with significant interactions. Furthermore, patients with AF recurrences within 1 year had a greater HF hospitalization risk after 1 year (1.61% vs 0.79%, log-rank p = 0.019). In conclusion, AF recurrence after RFCA was independently associated with HF hospitalizations.

Atrial Fibrillation and Heart Failure

Atrial fibrillation (AF) is the most common sustained arrhythmia worldwide and has a strong association with heart failure (HF). It often remains unclear if HF is the cause or consequence of AF due to the complexity of the processes that are involved in both the perpetuation of AF and the development of HF. To date, two therapeutic strategies are accepted as the standard of care in AF patients with heart failure. Rhythm control aims to permanently restore sinus rhythm, whereas a rate-control strategy aims to slow ventricular rate without the termination of AF. In the last 5 years a tremendous number of important studies have been published investigating the optimal therapeutic strategy in HF patients. This review highlights the important studies with respect to the involvement of AF in promoting left-ventricular dysfunction and discusses the optimal strategy in HF patients suffering from AF.

Automatic 3D Surface Reconstruction of the Left Atrium From Clinically Mapped Point Clouds Using Convolutional Neural Networks

Point clouds are a widely used format for storing information in a memory-efficient and easily manipulatable representation. However, research in the application of point cloud mapping and subsequent organ reconstruction with deep learning, is limited. In particular, current methods for left atrium (LA) visualization using point clouds recorded from clinical mapping during cardiac ablation are proprietary and remain difficult to validate. Many clinics rely on additional imaging such as MRIs/CTs to improve the accuracy of LA mapping. In this study, for the first time, we proposed a novel deep learning framework for the automatic 3D surface reconstruction of the LA directly from point clouds acquired via widely used clinical mapping systems. The backbone of our framework consists of a 30-layer 3D fully convolutional neural network (CNN). The architecture contains skip connections that perform multi-resolution processing to maximize information extraction from the point clouds and ensure a high-resolution prediction by combining features at different receptive levels. We used large kernels with increased receptive fields to address the sparsity of the point clouds. Residual blocks and activation normalization were further implemented to improve the feature learning on sparse inputs. By utilizing a light-weight design with low-depth layers, our CNN took approximately 10 s per patient. Independent testing on two cross-modality clinical datasets showed excellent dice scores of 93% and surface-to-surface distances below 1 pixel. Overall, our study may provide a more efficient, cost-effective 3D LA reconstruction approach during ablation procedures, and potentially lead to improved treatment of cardiac diseases.

The Effect of Obesity, Hypertension, Diabetes Mellitus, Alcohol, and Sleep Apnea on the Risk of Atrial Fibrillation

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia associated with a two-fold increase in mortality caused by a higher risk of stroke and heart failure. Currently, AF is present in ~ 2 % of the general population, and its incidence and prevalence are increasing. Obesity, hypertension, diabetes mellitus, obstructive sleep apnea, and alcohol consumption increase the risk of AF. Each unit of increase in BMI increases the risk of AF by 3 %, and intensive weight loss is also associated with reduced AF recurrence. Hypertension increases the risk of AF by 50 % in men and by 40 % in women, and explains ≈ 20 % of new AF cases. Patients with obstructive sleep apnea are at four times higher risk of developing AF than subjects without sleep apnea. Higher concentrations of pro-inflammatory cytokines, higher amounts of epicardial adipose tissue, and a higher degree of ventricular diffuse myocardial fibrosis are present in AF patients and patients with the aforementioned metabolic disorders. Several prospective cohort studies and randomized trials have been initiated to show whether weight loss and treatment of other risk factors will be associated with a reduction in AF recurrences.

Meta-Analysis of Catheter Ablation versus Medical Therapy for Heart Failure Complicated with Atrial Fibrillation

Objective

To compare the efficacy of catheter ablation and medical therapy in patients with heart failure and atrial fibrillation.

Methods

We searched randomized controlled trials comparing catheter ablation versus medical therapy for heart failure and atrial fibrillation through PubMed, MEDLINE, Embase, Cochrane Clinical Trials Database, Web of Science, and China National Knowledge Infrastructure. Articles were investigated for their methodological quality using the Cochrane Collaboration risk of the bias assessment tool. Forest plots, funnel plots, and sensitivity analysis were also performed on the included articles. Results were expressed as risk ratio (RR) and mean difference (MD) with 95% confidence intervals.

Results

Nine (9) studies were included in this study with 1131 patients. Meta-analysis showed a reduction in all-cause mortality from catheter ablation compared with medical therapy (RR = 0.53, 95% CI = 0.37 to 0.76; P=0.0007) and improved left ventricular ejection fraction (LVEF) (MD = 6.45, 95% CI = 3.49 to 9.41; P < 0.0001), 6-minute walking time (6MWT) (MD = 28.32, 95% CI = 17.77 to 38.87; P < 0.0001), and Minnesota Living with Heart Failure Questionnaire (MLHFQ) score (MD = 8.19, 95% CI = 0.30 to 16.08; P=0.04).

Conclusion

Catheter ablation had a better improvement than medical treatment in left ventricular ejection fraction, cardiac function, and exercise ability for atrial fibrillation and heart failure patients.

Impact of exercise capacity on the long-term incidence of atrial arrhythmias in heart failure

We sought to demonstrate the impact of improved peak exercise oxygen consumption (V̇O₂) during maximal exercise testing after cardiac rehabilitation (CR) on the incidence of arrhythmias in patients with heart failure (HF). The present study comprised of 220 patients with HF, and peak V̇O₂ was examined at 2 and 5 months after CR. Of the 220 patients, 110 (50%) had a low peak V̇O₂ of < 14 mL/min/kg at 2 months. The peak V̇O₂ improved in 86 of these 110 (78%) patients at 5 months after CR. During a median follow-up of 6 years, the patients with improvement in peak V̇O₂, compared to those without peak V̇O₂ improvement, had a lower rate of mortality (4% vs. 29%, log-rank, P < 0.001) and HF hospitalization (6 vs. 17%, log-rank, P = 0.044) and a lower incidence of new-onset atrial arrhythmias (9 vs. 27%, log-rank, P = 0.013), with no difference in the incidence of ventricular arrhythmias between groups (1 vs. 4%, log-rank, P = 0.309). The majority of deaths in the patients without an improved peak V̇O₂ were because of cardiovascular events (73%), particularly progressive HF (55%). Early detection and management of atrial arrhythmias may improve outcomes in patients without peak V̇O₂ improvement after CR.

Left atrial fibrosis progression detected by LGE-MRI after ablation of atrial fibrillation

BACKGROUND

Left atrial (LA) fibrosis is thought to be a substrate for atrial fibrillation (AF) and can be quantified by late gadolinium enhancement magnetic resonance imaging (LGE-MRI). Fibrosis formation in LA is a dynamic process and may either progress or regress following AF ablation. We examined the impact of postablation progression in LA fibrosis on AF recurrence.

METHODS

LA enhancement in LGE-MRI was quantified in 127 consecutive patients who underwent first time AF ablation. Serial LGE-MRIs were done prior to AF ablation, 3 months postablation and at least 12 months after second LGE-MRI. Transient postablation lesion (TL) was defined as atrial enhancement caused by ablation lesions that was detected on the first (3 month) but not on the second postablation LGE-MRI. New fibrosis (NF) was defined as atrial enhancement detected on the most recent LGE-MRI, at least 15 months after the ablation procedure. AF recurrence and its correlation with TL and NF was assessed in all patients during the follow-up period.

RESULTS

An increase of 1% NF increased the chance of postablation AF recurrence by 3% (hazard ratio [HR] 1.03, 95% CI 1-1.06, P = .05). TL had no significant impact on recurrence (P = .057). After adjusting for cardiovascular risk factors, HR increased as NF became greater. Greater volume of NF (≥21%) corresponded with lower arrhythmia-free survival (37% vs 62%, P = .01).

CONCLUSION

NF formation postablation of AF is a novel marker of long-term procedural outcome. Extensive NF is associated with significantly higher risk of atrial arrhythmia recurrence.

Long-term outcomes of index cryoballoon ablation or point-by-point radiofrequency ablation in patients with atrial fibrillation and systolic heart failure

Catheter ablation is an established effective approach for the treatment of atrial fibrillation (AF) in patients with heart failure, however, the role of cryoablation in this setting is unclear. Procedural success and left ventricular systolic dysfunction (LVEF) improvement in patients with LVEF ≤ 45% undergoing index catheter ablation with cryoablation were evaluated. Freedom from AF recurrence was seen in 43% rising to 59% following repeat procedure. There were significant improvements in LVEF and functional status at long-term follow-up. Results were comparable to a contemporaneous cohort of heart failure patients undergoing index ablation with radiofrequency ablation. Cryoablation is an effective first-line AF ablation approach in the setting of heart failure.

Atrial fibrosis underlying atrial fibrillation (Review)

Atrial fibrillation (AF) is one of the most common tachyarrhythmias observed in the clinic and is characterized by structural and electrical remodelling. Atrial fibrosis, an emblem of atrial structural remodelling, is a complex multifactorial and patient-specific process involved in the occurrence and maintenance of AF. Whilst there is already considerable knowledge regarding the association between AF and fibrosis, this process is extremely complex, involving intricate neurohumoral and cellular and molecular interactions, and it is not limited to the atrium. Current technological advances have made the non-invasive evaluation of fibrosis in the atria and ventricles possible, facilitating the selection of patient-specific ablation strategies and upstream treatment regimens. An improved understanding of the mechanisms and roles of fibrosis in the context of AF is of great clinical significance for the development of treatment strategies targeting the fibrous region. In the present review, a focus was placed on the atrial fibrosis underlying AF, outlining its role in the occurrence and perpetuation of AF, by reviewing recent evaluations and potential treatment strategies targeting areas of fibrosis, with the aim of providing a novel perspective on the management and prevention of AF.

Rhythm Control in Heart Failure Patients with Atrial Fibrillation

AF and heart failure (HF) commonly coexist. Left atrial ablation is an effective treatment to maintain sinus rhythm (SR) in patients with AF. Recent evidence suggests that the use of ablation for AF in patients with HF is associated with an improved left ventricular ejection fraction and lower death and HF hospitalisation rates. We performed a systematic search of world literature to analyse the association in more detail and to assess the utility of AF ablation as a non-pharmacological tool in the treatment of patients with concomitant HF.

Association Between Atrial Fibrillation and Sudden Cardiac Death

Emerging evidence suggests that atrial fibrillation (AF) may be associated with an increased risk of sudden cardiac death (SCD). However, AF shares risk factors with numerous cardiac conditions, including coronary heart disease and heart failure—the 2 most common substrates for SCD—making the AF-SCD relationship particularly challenging to address. A careful consideration of confounding factors is essential, since interventions for AF will be effective in reducing SCD only if there is a causal association between these 2 conditions. In this translational review, we detail the plausible underlying pathophysiological mechanisms through which AF may promote or lead to SCD, as well as the existing epidemiological evidence supporting an association between AF and SCD. While the role of AF in predicting SCD in the general population appears limited and not established, AF might be integrated to improve risk stratification in some specific phenotypes. Optimal AF management, including that of its associated conditions, appears to be of interest to prevent AF-related SCD, especially because the AF-SCD relationship is in part driven by heart failure.

Advanced heart failure: non-pharmacological approach

Patients with advanced heart failure have poor prognosis despite traditional pharmacological therapies. The early identification of these subjects would allow them to be addressed on time in dedicated centers to select patients eligible for heart transplantation or ventricular assistance. In this article we will report the current management of these patients based on latest international guidelines, underlining some critical aspects, with reference to future perspectives.

Cardiac MRI and Fibrosis Quantification

Left atrial fibrosis plays an important role in the pathophysiology of atrial fibrillation. Left atrial ablation is an effective and increasingly used strategy to restore and maintain sinus rhythm in patients with atrial fibrillation. Late gadolinium enhancement (LGE) MRI and custom image analysis software have been used to visualize and quantify preablation atrial fibrosis and postablation scar and new fibrosis formation. This article reviews technical aspects of imaging atrial fibrosis/scar by LGE-MRI; use of atrial fibrosis and scar in predicting outcomes; applications of LGE-MRI to assess ablation lesions and optimize ablation parameters while avoiding collateral damage.

Ablation of persistent atrial fibrillation and beyond

PURPOSE OF REVIEW

Percutaneous catheter ablation is an effective treatment for atrial fibrillation. However, catheter ablation for the treatment of persistent atrial fibrillation or long-standing persistent atrial fibrillation is associated with unsatisfying success rates. This review aims to summarize the recent literature on the progress of catheter ablation among patients with persistent atrial fibrillation RECENT FINDINGS: In this review, we outline the potential future therapeutic techniques of catheter ablation of persistent atrial fibrillation. We highlight the innovative techniques (rotor mapping, substrate mapping, delayed enhancement MRI, and high-resolution mapping catheter) of current approaches and optimal procedural endpoint for persistent atrial fibrillation.

SUMMARY

In summary, the optimal catheter ablation strategy for persistent atrial fibrillation remains unknown. Current data highlight the need for a better understanding of the substrate and mechanisms of arrhythmia maintenance in this population. Current mapping technologies offer additional tools (improved automatic algorithm for annotation, multiple electrode mapping, high-resolution mapping, and application of different processing techniques) for identifying the putative mechanism underlying atrial fibrillation. Further prospective studies are needed for the optimal procedural endpoint and the recent innovative techniques and their clinical benefits in ablation strategies.

[Atrial fibrillation : Recent studies and new treatment options]

Catheter ablation by pulmonary vein isolation (PVI) is established in patients suffering from drug-refractory symptomatic atrial fibrillation (AF). According to recent guidelines, it can also be offered to AF patients as a first-line treatment. The CASTLE-AF study randomized AF patients with severely impaired left ventricular (LV) function to catheter ablation or drug therapy. The patients in the ablation group experienced a significantly lower all-cause mortality and hospitalization rate compared to the conservatively managed group. This result is supported by the CAMERA-MRI trial. The benefit of AF ablation in heart failure was not reproducible in the large randomized CABANA trial. Due to a high cross-over rate, the results are vigorously being discussed and the consequences for clinical practice remain unclear. The DECAAF study described a positive correlation with left atrial fibrosis and the risk for recurrence following PVI. Whether those fibrotic areas should be targeted during the first ablation attempt is now part of the ongoing DECAAF-II trial. Its results might affect the preprocedural planning phase and future ablation strategies. Finally, new ablation techniques are being investigated. In this context, high-power short-duration ablation (HPSD) is of growing interest. In the QDOT-FAST trial, the procedure and fluoroscopy times could be significantly reduce using HPSD catheter technology. However, future studies are still required to evaluate the long-term performance of this novel ablation approach.

Atrial Fibrillation–Mediated Cardiomyopathy

AF-mediated cardiomyopathy (AMC) is an important reversible cause of heart failure that is likely underdiagnosed in today’s clinical practice. AMC describes AF either as the sole cause for ventricular dysfunction or exacerbating ventricular dysfunction in patients with existing cardiomyopathy or heart failure. Studies suggest that irreversible ventricular and atrial remodeling can occur in AMC, making timely diagnosis and intervention critical to optimize clinical outcome. Clinical correlation between AF onset/burden and progression of cardiomyopathy/heart failure symptoms provides strong evidence for the diagnosis of AMC. Cardiac MRI, continuous cardiac monitoring, and biomarkers are important diagnostic tools. From the therapeutic standpoint, early data suggest that AF ablation may improve long-term outcomes in AMC patients compared with medical rate and rhythm control. Patients with more AF burden and less severe underlying structural heart disease are more likely to experience left ventricle function recovery with successful AF ablation. Despite recent advances, significant knowledge gaps exist in our understanding of the epidemiology, mechanisms, diagnosis, management strategies, and prognosis of AMC.

Effect of catheter ablation on pre-existing abnormalities of left atrial systolic, diastolic, and neurohormonal functions in patients with chronic heart failure and atrial fibrillation

The critical role of the left atrium (LA) in cardiovascular homoeostasis is mediated by its reservoir, conduit, systolic, and neurohormonal functions. Atrial fibrillation is generally a reflection of underlying disease of the LA, especially in patients with heart failure. Disease-related LA remodelling leads to a decline in both atrial contractility and distensibility along with an impairment in the control of neurohormonal systems that regulate intravascular volume. Catheter ablation can lead to further injury to the atrial myocardium, as evidenced by post-procedural troponin release and tissue oedema. The cardiomyocyte loss leads to replacement fibrosis, which may affect up to 30-35% of the LA wall. These alterations further impair atrial force generation and neurohormonal functions; the additional loss of atrial distensibility can lead to a 'stiff LA syndrome', and the fibrotic response predisposes to recurrence of the atrial arrhythmia. Although it intends to restore LA systole, catheter ablation often decreases the chamber's transport functions. This is particularly likely in patients with long-standing atrial fibrillation and pre-existing LA fibrosis, especially those with increased epicardial adipose tissue (e.g. patients with obesity, diabetes and/or heart failure with a preserved ejection fraction). Although the fibrotic LA in these individuals is an ideal substrate for the development of atrial fibrillation, it may be a suboptimal substrate for catheter ablation. Such patients are not likely to experience long-term restoration of sinus rhythm, and catheter ablation has the potential to worsen their haemodynamic and clinical status. Further studies in this vulnerable group of patients are needed.

Post-cardioversion Improvement in LV Function Defined by 4D Flow Patterns and Energetics in Patients With Atrial Fibrillation

Background

Atrial fibrillation (AF) is a prevalent cause of cardiovascular morbidity, including thromboembolism and heart failure. Left ventricular dysfunction (LVD) detected in AF patients may be either precursor or consequence of the arrythmia. Successful cardioversion of chronic AF is often followed by a transient period of left atrial (LA) stunning, where depressed mechanical atrial contraction persists despite reinstitution of sinus rhythm. To determine if AF-associated LVD would improve with resolution of LA dysfunction, AF patients were examined immediately and 4 weeks after cardioversion to sinus rhythm. 4D flow cardiovascular magnetic resonance (CMR) assesses ventricular function according to the volumes and energetics of functional components of the LV volume. Previously, described 4D CMR markers of LVD include decreased volume and end-diastolic kinetic energy (KE) of the Direct flow, which is the portion of LV volume that passes directly from inflow to outflow in a single cycle. We hypothesize that impaired LV flow patterns and energetics will be found immediately after cardioversion during atrial stunning, and that those parameters will improve as atrial function returns.

Methods

Ten patients with a history of AF underwent CMR 2-3 h (Time-1) and 4 weeks (Time-2), following electrical cardioversion to sinus rhythm. 4D phase-contrast velocity data and morphological images were acquired at a 3T CMR system. Using a previously evaluated method, pathlines were emitted from the LV end diastolic volume (LVEDV) and traced forward and backward in time until end-systole. The LVEDV was automatically separated into four functional flow components whose volume and KE were calculated.

Results

Left atrial fractional area change increased over the follow-up period (P = 0.001), indicating recovery of LA mechanical function. LVEF increased between Time-1 and Time-2 (P = 0.003); LVEDVI did not change (P = 0.319). Over that interval, the ratios of Direct flow/LVEDV volume and KE increased (P = 0.001 and P = 0.003, respectively), while the ratios of Residual volume/LVEDV volume and KE decreased (P = 0.001 and P = 0.005, respectively).

Conclusion

Post-cardioversion recovery of LA function was associated with improvements in conventional and 4D CMR markers of LV function. Flow-specific measures demonstrate the negative but potentially reversible impact of LA dysfunction on volume and energetic aspects of LV function.

Relaxin and fibrosis: Emerging targets, challenges, and future directions

The peptide hormone relaxin is well-known for its anti-fibrotic actions in several organs, particularly from numerous studies conducted in animals. Acting through its cognate G protein-coupled receptor, relaxin family peptide receptor 1 (RXFP1), serelaxin (recombinant human relaxin) has been shown to consistently inhibit the excessive extracellular matrix production (fibrosis) that results from the aberrant wound-healing response to tissue injury and/or chronic inflammation, and at multiple levels. Furthermore, it can reduce established scarring by promoting the degradation of aberrant extracellular matrix components. Following on from the review that describes the mechanisms and signaling pathways associated with the extracellular matrix remodeling effects of serelaxin (Ng et al., 2019), this review focuses on newly identified tissue targets of serelaxin therapy in fibrosis, and the limitations associated with (se)relaxin research.

Management of asymptomatic arrhythmias: a European Heart Rhythm Association (EHRA) consensus document, endorsed by the Heart Failure Association (HFA), Heart Rhythm Society (HRS), Asia Pacific Heart Rhythm Society (APHRS), Cardiac Arrhythmia Society of Southern Africa (CASSA), and Latin America Heart Rhythm Society (LAHRS)

Asymptomatic arrhythmias are frequently encountered in clinical practice. Although studies specifically dedicated to these asymptomatic arrhythmias are lacking, many arrhythmias still require proper diagnostic and prognostic evaluation and treatment to avoid severe consequences, such as stroke or systemic emboli, heart failure, or sudden cardiac death. The present document reviews the evidence, where available, and attempts to reach a consensus, where evidence is insufficient or conflicting.

The Evolving Role of Catheter Ablation in Patients With Heart Failure and AF

AF and heart failure are emerging epidemics worldwide. Several recent trials have provided a growing evidence base for the benefits of catheter ablation in this patient group, which are yet to be universally adopted in clinical practice guidelines. This paper provides a summary of recent developments in this field and provides pragmatic advice to the treating physician regarding the appropriate role of catheter ablation in the overall management of patients with comorbid AF and heart failure.