Vagal responses induced by endocardial left atrial autonomic ganglion stimulation before and after pulmonary vein antrum isolation for atrial fibrillation

Early Clinical Outcomes and Advantages of a Novel-Size Adjustable Second-Generation Cryoballoon: A Proof-of-Concept Study

(1) Background/Objective Balloon-guided catheter ablation (CA) has emerged as an alternative option for atrial fibrillation (AF) management. The recent introduction of a novel-size adjustable second-generation cryoballoon (CB) system offers innovations, but clinical outcomes remain unexplored. This study aims to assess the acute performance of the POLARx FIT™ CB system in AFCA. (2) Methods: Consecutive patients undergoing AF ablation with the POLARx FIT™ CB system in our center were included. The primary outcome was the rate of 31 mm balloon-size utilization, with secondary outcomes including acute pulmonary vein isolation (PVI) rate, periprocedural complications, and in-hospital AF recurrences. (3) Results: Twenty-four patients with a mean age of 59.5 years, predominantly male (87.5%), and exhibiting paroxysmal AF (91.7%) were enrolled. Procedural characteristics demonstrated a high acute success rate (100% PV isolation) with a favorable safety profile. Notably, the 31 mm CB configuration was utilized in 51% of applications, showcasing its adaptability in challenging anatomies. No major complications occurred, with two patients experiencing in-hospital self-limiting AF recurrences. (4) Conclusions: This study represents the first comprehensive assessment of the POLARx FIT™ CB system in AF ablation. While acknowledging the study's limitations, this novel CB emerges as a promising tool, warranting further exploration in larger studies with extended follow-up periods.

Pulmonary vein isolation with adjunctive left atrial ganglionic plexus ablation for treatment of atrial fibrillation: a meta-analysis of randomized controlled trials

BACKGROUND

Adjunctive ganglionic plexus (GP) ablation may increase the efficacy of pulmonary vein isolation (PVI) for treatment of atrial fibrillation (AF). Prior meta-analyses examining PVI with adjunctive GP ablation have included non-randomized trials and have included trials evaluating thorascopic epicardial ablation. The objective of this study is to perform a meta-analysis of randomized controlled trials (RCTs) comparing endocardial catheter-based PVI to PVI with adjunctive GP ablation.

METHODS

Summary odds ratio (OR) and 95% confidence intervals (CIs) were calculated. Heterogeneity was assessed with I² values. Sub-group analysis was performed comparing arrhythmia recurrence between patients with paroxysmal versus persistent AF at trial baseline. Meta-regressions were performed with mean left atrial diameter and left ventricular ejection fraction at trial baseline as the moderator variables.

RESULTS

Five RCTs were identified including 814 patients: 406 PVI + GP ablation and 408 PVI alone. The mean age of participants was 56.5 years and 74.7% were male. Four of these trials evaluated catheter-based endocardial ablation for a total of 574 patients: 289 PVI + GP ablation and 285 PVI alone. The odds of arrhythmia recurrence in patients undergoing adjunctive GP ablation with PVI compared with PVI alone were a reduced: odds ratio (OR) 0.58, 95% confidence interval (CI) 0.41-0.82, I² = 40.2%. In the subgroup analysis, the odds of arrhythmia recurrence with adjunctive GP ablation were reduced in those with paroxysmal AF (OR 0.396, 95% CI 0.23-0.69, I² = 0%). A non-significant trend to reduced arrhythmia recurrence was also observed in those with persistent AF (OR 0.726, 95% CI 0.475-1.112, I² = 0%). When performing the meta-regression, increased left atrial diameter was associated with decreased treatment effect of adjunctive GP ablation (R² index = 1.0, I² = 0%).

CONCLUSIONS

The addition of GP ablation to PVI was associated with reduced arrhythmia recurrence. Adjunctive GP ablation was more effective in paroxysmal AF and in patients with smaller atria. Larger RCTs are needed to confirm the efficacy of GP + PVI ablation.

Pulsed Field Ablation to Treat Atrial Fibrillation: Autonomic Nervous System Effects

BACKGROUND

During atrial fibrillation ablations using thermal energy, the treatment effect is attributed to not just pulmonary vein isolation (PVI), but also to modulation of the autonomic nervous system by ablation of cardiac ganglionated plexi (GP).

OBJECTIVES

This study sought to assess the impact of pulsed field ablation (PFA) on the GP in patients undergoing PVI.

METHODS

In the retrospective phase, heart rate was assessed pre- versus post-PVI using PFA, cryoballoon ablation, or radiofrequency ablation. In the prospective phase, a pentaspline PFA catheter was used in a protocol: 1) pre-PFA, high-frequency stimulation (HFS) identified GP sites by vagal effects; 2) PVI was performed assessing for repetitive vagal effects over each set of PF applications; 3) mapping defined PVI extent to identify those GP in the ablation zone; and 4) repeat HFS at GP sites to assess for persistence of vagal effects.

RESULTS

Between baseline and 3 months, heart rates in the retrospective radiofrequency ablation (n = 40), cryoballoon (n = 40), and PFA (n = 40) cohorts increased by 8.9 ± 11.4, 11.1 ± 9.4, and -0.1 ± 9.2 beats/min, respectively (P= 0.01 PFA vs radiofrequency ablation; P= 0.01 PFA vs cryoballoon ablation). In the prospective phase, pre-PFA HFS in 20 additional patients identified 65 GP sites. During PFA, vagal effects were noted in 45% of first PF applications, persisting through all applications in 83%. HFS post-PFA reproduced vagal effects in 29 of 38 sites (76%) in low-voltage tissue.

CONCLUSIONS

PFA has minimal effect on GP. Unlike with thermal ablation, the mechanism by which PFA treats atrial fibrillation is mediated solely by durable PVI.

Autonomic modulation and cardiac arrhythmias: old insights and novel strategies

The autonomic nervous system (ANS) plays a critical role in both health and states of cardiovascular disease. There has been a long-recognized role of the ANS in the pathogenesis of both atrial and ventricular arrhythmias (VAs). This historical understanding has been expanded in the context of evolving insights into the anatomy and physiology of the ANS, including dysfunction of the ANS in cardiovascular disease such as heart failure and myocardial infarction. An expanding armamentarium of therapeutic strategies-both invasive and non-invasive-have brought the potential of ANS modulation to contemporary clinical practice. Here, we summarize the integrative neuro-cardiac anatomy underlying the ANS, review the physiological rationale for autonomic modulation in atrial and VAs, highlight strategies for autonomic modulation, and finally frame future challenges and opportunities for ANS therapeutics.

Migraine and risk of stroke

Migraine and stroke are two common and heterogeneous neurovascular disorders responsible for a significant burden for those affected and a great economic cost for the society. There is growing evidence that migraine increases the overall risk of cerebrovascular diseases. In this review, based on available literature through a PubMed search, we found that ischaemic stroke in people with migraine is strongly associated with migraine with aura, young age, female sex, use of oral contraceptives and smoking habits. The risk of transient ischaemic attack also seems to be increased in people with migraine, although this issue has not been extensively investigated. Although migraine appears to be associated with haemorrhagic stroke, the migraine aura status has a small influence on this relationship. Neuroimaging studies have revealed a higher prevalence of asymptomatic structural brain lesions in people with migraine. They are also more likely to have unfavourable vascular risk factors; however, the increased risk of stroke seems to be more apparent among people with migraine without traditional risk factors. The mechanism behind the migraine-stroke association is unknown. In light of the higher risk of stroke in people with migraine with aura, it is important to identify and modify any vascular risk factor. There is currently no direct evidence to support that a migraine prophylactic treatment can reduce future stroke in people with migraine.

Migraine with visual aura is a risk factor for incident atrial fibrillation: A cohort study

OBJECTIVE

Migraine with visual aura is associated with cardioembolic stroke risk. The aim of this study was to test association between migraine with visual aura and atrial fibrillation (AF), in the Atherosclerosis Risk in Communities study.

METHODS

In the Atherosclerosis Risk in Communities study, a longitudinal, community-based cohort study, participants were interviewed for migraine history in 1993-1995 and were followed for incident AF through 2013. AF was adjudicated using ECGs, discharge codes, and death certificates. Multivariable Cox proportional hazards models were used to study the relation between migraine and its subtypes with incident AF, compared with controls without headaches. Mediation analysis was conducted to test whether AF was a mediator of migraine with visual aura-associated stroke risk.

RESULTS

Of 11,939 participants assessed for headache and without prior AF or stroke, 426 reported migraines with visual aura, 1,090 migraine without visual aura, 1,018 nonmigraine headache, and 9,405 no headache. Over a 20-year follow-up period, incident AF was noted in 232 (15%) of 1,516 with migraine and 1,623 (17%) of 9,405 without headache. After adjustment for multiple confounders, migraine with visual aura was associated with increased risk of AF compared to no headache (hazard ratio 1.30, 95% confidence interval 1.03-1.62) as well as when compared to migraine without visual aura (hazard ratio 1.39, 95% confidence interval 1.05-1.83). The data suggest that AF may be a potential mediator of migraine with visual aura-stroke risk.

CONCLUSIONS

Migraine with aura was associated with increased risk of incident AF. This may potentially lead to ischemic strokes.

A novel approach to mapping the atrial ganglionated plexus network by generating a distribution probability atlas

Introduction

The ganglionated plexuses (GPs) of the intrinsic cardiac autonomic system are implicated in arrhythmogenesis. GP localization by stimulation of the epicardial fat pads to produce atrioventricular dissociating (AVD) effects is well described. We determined the anatomical distribution of the left atrial GPs that influence atrioventricular (AV) dissociation.

Methods and Results

High frequency stimulation was delivered through a Smart‐Touch catheter in the left atrium of patients undergoing atrial fibrillation (AF) ablation. Three dimensional locations of points tested throughout the entire chamber were recorded on the CARTO™ system. Impact on the AV conduction was categorized as ventricular asystole, bradycardia, or no effect. CARTO maps were exported, registered, and transformed onto a reference left atrial geometry using a custom software, enabling data from multiple patients to be overlaid. In 28 patients, 2108 locations were tested and 283 sites (13%) demonstrated (AVD‐GP) effects. There were 10 AVD‐GPs (interquartile range, 11.5) per patient. Eighty percent (226) produced asystole and 20% (57) showed bradycardia. The distribution of the two groups was very similar. Highest probability of AVD‐GPs (>20%) was identified in: inferoseptal portion (41%) and right inferior pulmonary vein base (30%) of the posterior wall, right superior pulmonary vein antrum (31%).

Conclusion

It is feasible to map the entire left atrium for AVD‐GPs before AF ablation. Aggregated data from multiple patients, producing a distribution probability atlas of AVD‐GPs, identified three regions with a higher likelihood for finding AVD‐GPs and these matched the histological descriptions. This approach could be used to better characterize the autonomic network.

Coincidental ganglionated plexus modification during radiofrequency pulmonary vein isolation and post-ablation arrhythmia recurrence

Aims

Vagal responses (VR) during left atrial ablation for atrial fibrillation (AF) treatment have been reported to be associated with less recurrences, presumably because they are a sign of ganglionated plexi modification. Our objective was to evaluate whether coincidentally elicited VR during left atrial ablation are associated with lower AF recurrence rates.

Methods and results

This is a post hoc analysis of a prospective study of 291 patients with paroxysmal AF undergoing radiofrequency pulmonary vein isolation (PVI). Vagal responses were defined as episodes of heart rate <40 bpm or asystole lasting >5 s elicited during energy application. Sixty-eight patients (23.4%) had a VR during ablation. In Kaplan-Meier analysis, mean recurrence-free survival was 449 days (95% confidence interval 411-488) in patients with VR when compared with 435 days (95% confidence interval 415-455) in those without (P = 0.310). The 12-month recurrence rate estimates were 25 and 27%, respectively. In an unadjusted Cox model, VR was associated with an odds ratio for recurrence of 0.77 (95% confidence interval 0.46-1.28).

Conclusion

Coincidentally elicited VR during radiofrequency PVI in patients with paroxysmal AF do not appear to be related to lower risk of arrhythmia recurrence. This may mean that, even if a VR is truly a sign of coincidental ablation of a ganglionated plexus, this does not necessarily mean that a therapeutic modification has been effected, at least to a degree associated with clinical benefit.

Mechanisms of atrial fibrillation in athletes: what we know and what we do not know

Exercise is an emerging cause of atrial fibrillation (AF) in young individuals without coexisting cardiovascular risk factors. The causes of exercise-induced atrial fibrillation remain largely unknown, and conclusions are jeopardised by apparently conflicting data. Some components of the athlete's heart are known to be arrhythmogenic in other settings. Bradycardia, atrial dilatation and, possibly, atrial premature beats are therefore biologically plausible contributors to exercise-induced AF. Challenging findings in an animal model suggest that exercise might also prompt the development of atrial fibrosis, possibly due to cumulative minor structural damage after each exercise bout. However, there is very limited, indirect data supporting this hypothesis in athletes. Age, sex, the presence of comorbidities and cardiovascular risk factors, and genetic individual variability might serve to flag those athletes who are at the higher risk of exercise-induced AF. In this review, we will critically address current knowledge on the mechanisms of exercise-induced AF.

What Is the Appropriate Lesion Set for Ablation in Patients with Persistent Atrial Fibrillation?

OPINION STATEMENT

Special attention must be paid to detect, diagnose, and optimize management of reversible or treatable causes of long-standing persistent atrial fibrillation (LSPAF) such as obesity, obstructive sleep apnea (OSA), hypertension, hypo or hyperthyroidism, inflammatory and infectious diseases, and stress. Though, we strongly believe that the role of the pulmonary veins (PVs) is more pronounced in paroxysmal atrial fibrillation (AF) than in persistent AF, performing an adequate pulmonary vein isolation is still key in LSPAF. Patients with LSPAF will frequently require a more aggressive mapping and ablative approach. We do not encourage the use of empiric lines or complex fractionated atrial electrograms. Ablation of sites associated with non-PV triggers such as the entire posterior wall, the roof, the anterior part of the left atrium septum, left atrial appendage (LAA), the CS and SVC has been shown to improve the freedom from AF at follow-up when combined with PVs isolation. During the isoproterenol challenge, non-PV triggers are detected in most patients with AF. Mapping non-PV triggers is guided by multiple catheters positioned along both the right and left atriums: a 10-pole circular mapping catheter in the left superior PV recording the far-field LAA activity, the ablation catheter in the right superior PV that records the far-field interatrial septum and a 20-pole catheter with electrodes spanning from the SVC to the CS. With this simple catheter setup, when focal ectopic atrial activity is observed (a single ectopic beat is enough) their activation sequence is compared to that of sinus rhythm, allowing to quickly identify their area of origin. For significant non-PV triggers (repetitive isolated beats, focal atrial tachycardias or beats triggering AF/atrial flutter, a more detailed activation mapping is performed in the area of origin. They are subsequently targeted with focal ablation, exception being the triggers originating from the SVC, LAA or CS, in which cases complete isolation of these structures is the ablation strategy of choice. We truly believe the LAA deserves special consideration when managing patients with persistent AF and LSPAF.

Catheter Ablation of Recurrent Paroxysmal Atrial Fibrillation: Is Gap-Closure Combining Ganglionated Plexi Ablation More Effective?

BACKGROUND

For repeat treatment with paroxysmal atrial fibrillation (PAF) recurrence, gap-closure at pulmonary vein ostia alone is not enough. Many recent studies indicated that ganglionated plexi (GPs) denervation could reduce the recurrence of AF. However, it is unclear whether the clinical outcomes of additional GP ablation plus pulmonary veins (PVs ) reisolation during a repeat procedure were associated with less recurrence in PAF patients. The purpose of this study was to evaluate if a repeat procedure of GP ablation (GPA) combining repeated procedure of pulmonary vein isolation (re-PVI), i.e., gap-closure, can offer additional benefit for patients with PAF recurrence.

METHOD

A total of 123 consecutive patients with PAF recurrence who underwent success repeat procedures were retrospectively analyzed in our center (2014-2015). Note that 64 patients (group 1, GPA group) were performed with GPA plus re-PVI, while 59 patients (group 2, re-PVI group) had re-PVI (gap-closure) alone. Organized atrial tachycardias (OATs) documented or induced at the end of the procedure were all mapped and ablated. Patients were scheduled for a 12-month follow-up. Clinical presentation and outcome data for the two groups were assessed.

RESULT

At the 12-month follow-up 58 of 64 patients (90.6%) in group 1 and 46 of 59 patients (78%) in group 2 remained in sinus rhythm (SR) off antiarrhythmia drugs (AADs) (P = 0.045).

CONCLUSION

GPA conferred incremental benefit when performed in addition to re-PVI in patients with PAF recurrence; the GPA group yielded higher success rates than the re-PVI group.

Modulation of Autonomic Nervous Activity in the Termination of Paroxysmal Atrial Fibrillation

BACKGROUND

Autonomic nervous activity plays a critical role in the genesis of paroxysmal atrial fibrillation (AF, PAF). However, the role of autonomic nervous activity on AF termination has not been elucidated. Heart rate variability (HRV) is widely used to evaluate autonomic nervous activity in humans. The purpose of this study was to assess whether autonomic nervous activity assessed by HRV contributes to AF termination.

METHODS

Electrocardiograms (ECGs) and HRV were studied in patients with termination of sustained (>30 s) PAF by 24-hour ambulatory Holter monitoring. The 20-minute interval after termination of AF was divided into four segments of 5 minutes each, and a frequency analysis was applied to each 5-minute segment.

RESULTS

In 52 AF episodes, the ultra-low-frequency power, very-low-frequency power, low-frequency power (LF), high-frequency power (HF), and total power significantly decreased with time after episodes of AF termination. The LF/HF (L/H) ratio, normalized LF (LFnu), and normalized HF (HFnu) significantly changed after AF termination. Eighteen (35%) episodes had decreased LFnu and increased HFnu (sympathetic withdrawal and vagal activation), which had slower average AF ventricular responses (92 ± 16 beats/min vs 105 ± 24 beats/min, P < 0.05) than the AF termination episodes (n = 34, 65%) with increased LFnu and decreased HFnu (sympathetic activation and vagal withdrawal). Moreover, older patients (aged >65 years) had a higher incidence (n = 27, 75%) of AF termination with increased LFnu and decreased HFnu than did younger patients (aged ≤65 years, n = 7, 44%, P < 0.05).

CONCLUSION

Autonomic changes critically regulate termination of PAF, which is modulated by aging.

Comparison of the Efficacy of Empiric Thoracic Vein Isolation for the Treatment of Paroxysmal and Persistent Atrial Fibrillation in Patients Without Structural Heart Disease

INTRODUCTION

The guidelines suggest that an adjuvant substrate modification in addition to pulmonary vein isolation (PVI) may be needed for persistent atrial fibrillation (PerAF) assuming that catheter ablation is less successful for PerAF than paroxysmal AF (PAF). To revisit the above assumption, we compared the outcome of the same catheter ablation strategy between PAF and PerAF.

METHODS AND RESULTS

Two hundred and thirty-three consecutive patients (mean age 60 ± 10 years, 53 PerAF and 8 long-lasting PerAF) without structural heart disease underwent catheter ablation of AF by the same strategy using an empiric thoracic vein isolation (a wide circumferential PVI plus empiric superior vena cava isolation) as a major part of the strategy without any adjuvant substrate modification. The duration of AF in the patients with PerAF was 6 ± 4 months. During 25 ± 10 months of follow-up after single procedures, 71 (30%) patients had atrial tachyarrhythmia recurrences without antiarrhythmic drugs. A Kaplan-Meier analysis of the recurrence-free survival rate after a single procedure and after repeat procedures revealed no significant difference between the patients with PAF and those with PerAF (log-rank, P = 0.38 and P = 0.27, respectively). A Cox regression multivariate analysis of the variables including the age, gender, PerAF, body mass index, left ventricular ejection fraction, and left atrial volume index demonstrated that none of the variables were an independent predictor of an atrial tachyarrhythmia recurrence after a single ablation procedure.

CONCLUSION

In patients without underlying heart disease, the procedural outcome of an empiric thoracic vein isolation is comparable for PAF and PerAF.

Ganglionated Plexi Ablation: Physiology and Clinical Applications

Ganglionated plexi (GP), consisting of conglomerations of autonomic ganglia on the epicardial surface of the heart, have been shown to play a significant role in different arrhythmias, including atrial fibrillation. GP ablation has become an adjunctive procedure in the treatment of atrial fibrillation, while it has been used successfully in preliminary studies in vasovagal syncope. This review will present the current data on the physiology and clinical applications of GP ablation in the treatment of atrial fibrillation and other diseases.

Ablation therapy for left atrial autonomic modification

The autonomic nervous system is implicated in the multifactorial pathogenesis of atrial fibrillation (AF) but few studies have attempted neural targeting for therapeutic intervention. We have demonstrated that short bursts of stimulation, at specific sites of left atrial ganglionated plexi (GPs), trigger fibrillation-inducing atrial ectopy and importantly continuous stimulation of these sites may not induce AV block, the 'conventional' marker used to locate GPs. We have shown that these ectopy-triggering GP (ET-GP) sites are anatomically stable and can be rendered inactive by either ablation at the site or by ablation between the site and the adjacent pulmonary vein (PV). This may have important implications for planning patient specific strategies for ablation of paroxysmal AF in the future.

Catheter Ablation for Long-Standing Persistent Atrial Fibrillation

Atrial fibrillation (AF) is the most common sustained arrhythmia worldwide and represents a major burden to health care systems. Atrial fibrillation is associated with a 4- to 5-fold increased risk of thromboembolic stroke. The pulmonary veins have been identified as major sources of atrial triggers for AF. This is particularly true in patients with paroxysmal AF but not always the case for those with long-standing persistent AF (LSPAF), in which other locations for ectopic beats have been well recognized. Structures with foci triggering AF include the coronary sinus, the left atrial appendage (LAA), the superior vena cava, the crista terminalis, and the ligament of Marshall. More than 30 studies reporting results on radiofrequency ablation of LSPAF have been published to date. Most of these are observational studies with very different methodologies using different strategies. As a result, there has been remarkable variation in short- and long-term success, which suggests that the optimal ablation technique for LSPAF is still to be elucidated. In this review we discuss the different approaches to LSPAF catheter ablation, starting with pulmonary vein isolation (PVI) through ablation lines in different left atrial locations, the role of complex fractionated atrial electrograms, focal impulses and rotor modulation, autonomic modulation (ganglionated plexi), alcohol ablation, and the future of epicardial mapping and ablation for this arrhythmia. A stepwise ablation approach requires several key ablation techniques, such as meticulous PVI, linear ablation at the roof and mitral isthmus, electrogram-targeted ablation with particular attention to triggers in the coronary sinus and LAA, and discretionary right atrial ablation (superior vena cava, intercaval, or cavotricuspid isthmus lines).

Mechanisms Underlying AF: Triggers, Rotors, Other?

OPINION STATEMENT

There is ongoing debate regarding the precise mechanisms underlying atrial fibrillation (AF). An improved understanding of these mechanisms is urgently needed to improve interventional strategies to suppress and eliminate AF, since the success of current strategies is suboptimal. At present, guidelines for AF ablation focus on pulmonary vein (PV) isolation for the prevention of arrhythmia. Additional targets are presently unclear, and include additional linear ablation and electrogram-guided substrate modification, without clear mechanistic relevance. PV and non-PV triggers are likely central in the first few seconds of AF initiation. Rapid activation from such triggers interacts with transitional mechanisms including conduction velocity slowing, action potential duration (APD) alternans, and steep APD restitution to cause conduction block and initiate functional reentry. However, complete suppression of potential triggers has proven elusive, and the intra-procedural mapping and targeting of transitional mechanisms has not been reported. A growing body of research implicates electrical rotors and focal sources as central mechanisms for the maintenance of AF. In several recent series, they were observed in nearly all patients with sustained arrhythmia. Ablation of rotor and focal source sites, prior to pulmonary vein isolation, substantially modulated atrial fibrillation in a high proportion of patients, and improved ablation outcomes versus pulmonary vein isolation alone. These results have subsequently been confirmed in multicenter series, and the improved outcomes have been found to persist to a mean follow-up of 3 years. Recently, rotors have been observed by multiple groups using diverse technologies. These findings represent a paradigm shift in AF, focusing on sustaining mechanisms, as is currently done with other arrhythmias such as atrioventricular node reentrant tachycardia. Studies are currently underway to assess the optimal strategy for the application of rotor-based ablation in AF management, including clinical trials on the relative efficacy of rotor-only ablation versus PVI-only ablation, which will inform future practice guidelines.

The role of the autonomic ganglia in atrial fibrillation

Recent experimental and clinical studies have shown that the epicardial autonomic ganglia play an important role in the initiation and maintenance of atrial fibrillation (AF). In this review, we present the current data on the role of the autonomic ganglia in the pathogenesis of AF and discuss potential therapeutic implications. Experimental studies have demonstrated that acute autonomic remodeling may play a crucial role in AF maintenance in the very early stages. The benefit of adding ablation of the autonomic ganglia to the standard pulmonary vein (PV) isolation procedure for patients with paroxysmal AF is supported by both experimental and clinical data. The interruption of axons from these hyperactive autonomic ganglia to the PV myocardial sleeves may be an important factor in the success of PV isolation procedures. The vagus nerve exerts an inhibitory control over the autonomic ganglia and attenuation or loss of this control may allow these ganglia to become hyperactive. Autonomic neuromodulation using low-level vagus nerve stimulation inhibits the activity of the autonomic ganglia and reverses acute electrical atrial remodeling during rapid atrial pacing and may provide an alternative non-ablative approach for the treatment of AF, especially in the early stages. This notion is supported by a preliminary human study. Further studies are warranted to confirm these findings.

Adjunct ablation strategies for persistent atrial fibrillation-beyond pulmonary vein isolation

Atrial fibrillation (AF) is the most common sustained arrhythmia. Recent guidelines recommend pulmonary vein isolation (PVI) as the main procedural endpoint to control recurrent AF in symptomatic patients resistant to antiarrhythmic drugs. The efficacy of such procedure is higher in paroxysmal AF while is still unsatisfactory in persistent and long-standing persistent AF. This review will summarize the state-of-the-art of AF ablation techniques in patients with persistent AF, discussing the evidence underlying different approaches with a particular focus on adjunctive ablation strategies beyond PVI including linear ablation, ablation of complex fractionated atrial electrograms (CFAE), ablation of ganglionated plexi, dominant frequency, rotors and other anatomical sites frequently involved in AF triggers.

The role of rotors in atrial fibrillation

Despite significant advances in our understanding of atrial fibrillation (AF) mechanisms in the last 15 years, ablation outcomes remain suboptimal. A potential reason is that many ablation techniques focus on anatomic, rather than patient-specific functional targets for ablation. Panoramic contact mapping, incorporating phase analysis, repolarization and conduction dynamics, and oscillations in AF rate, overcomes many prior difficulties with mapping AF. This approach provides evidence that the mechanisms sustaining human AF are deterministic, largely due to stable electrical rotors and focal sources in either atrium. Ablation of such sources (Focal Impulse and Rotor Modulation: FIRM ablation) has been shown to improve ablation outcome compared with conventional ablation alone; independent laboratories directly targeting stable rotors have shown similar results. Clinical trials examining the role of stand-alone FIRM ablation are in progress. Looking forward, translating insights from patient-specific mapping to evidence-based guidelines and clinical practice is the next challenge in improving patient outcomes in AF management.

Effect of catheter ablation and periprocedural anticoagulation regimen on the clinical course of migraine in atrial fibrillation patients with or without pre-existent migraine: results from a prospective study

BACKGROUND

We examined the influence of catheter ablation and periprocedural anticoagulation regimen on trajectory of migraine in atrial fibrillation patients with or without migraine history.

METHODS AND RESULTS

Forty patients with (group 1: 64 ± 8 years; men 78%) and 85 (group 2: 61 ± 10 years; men 73%) without migraine history undergoing atrial fibrillation-ablation were enrolled. Migraine status and quality of life were evaluated using standardized questionnaires. Diffusion magnetic resonance imaging of brain was performed for all at pre and 24 hours post procedure. Catheter ablation was performed with (88, 70%) or without (37, 30%) continuous warfarin treatment. Fifty-four patients (11 and 43 from groups 1 and 2, respectively) had subtherapeutic international normalized ratio on procedure day. At 17 ± 5 months follow-up, from group 1, 25 (63%) reported no migraine, 10 (25%) had < 1, and 3 (8%) had 2 to 3 monthly symptoms. Intensity of pain decreased from baseline 7 (Q1-Q3, 4-8) to 2 (0-4) scale points at follow-up (P < 0.001) and duration of headache from median 8 (Q1-Q3, 4-15) to 0.5 (Q1-Q3, 0-2) hours (P < 0.001). Two patients from group 1 reported increased migraine severity and 2 from group 2 had new-onset migraine. Follow-up diffusion magnetic resonance imaging revealed new infarcts in 9.6% (12/125) patients; of which 11 had subtherapeutic preprocedural international normalized ratio on or off continuous warfarin. Quality of life improved significantly in patients with successful ablation, being more pronounced in group 1.

CONCLUSIONS

In most patients, migraine symptoms improved substantially after catheter ablation. Interestingly, the only cases of new migraine and aggravation of pre-existent headache had subtherapeutic international normalized ratio during the procedure and new cerebral infarcts.

Device-Based Approaches to Modulate the Autonomic Nervous System and Cardiac Electrophysiology

Alterations in resting autonomic tone can be pathogenic in many cardiovascular disease states, such as heart failure and hypertension. Indeed, autonomic modulation by way of beta-blockade is a standard treatment of these conditions. There is a significant interest in developing non-pharmacological methods of autonomic modulation as well. For instance, clinical trials of vagal stimulation and spinal cord stimulation in the treatment of heart failure are currently underway, and renal denervation has been studied recently in the treatment of resistant hypertension. Notably, autonomic stimulation is also a potent modulator of cardiac electrophysiology. Manipulating the autonomic nervous system in studies designed to treat heart failure and hypertension have revealed that autonomic modulation may have a role in the treatment of common atrial and ventricular arrhythmias as well. Experimental data on vagal nerve and spinal cord stimulation suggest that each technique may reduce ventricular arrhythmias. Similarly, renal denervation may play a role in the treatment of atrial fibrillation, as well as in controlling refractory ventricular arrhythmias. In this review, we present the current experimental and clinical data on the effect of these therapeutic modalities on cardiac electrophysiology and their potential role in arrhythmia management.

The Role of Renal Sympathetic Denervation in Atrial Fibrillation

Endocardial catheter ablation is a widely used alternative for the treatment of atrial fibrillation (AF). Despite technical improvements, and increased understanding of mechanism, and acquired technical experience over many years, the results are not yet optimal. This results in an ongoing search for new therapeutic approaches. Because cardiac sympathetic drive is potentially responsible for triggering and sustaining AF, modulation of sympathetic tone has been proposed as a viable treatment objective. The early attempts to test this concept were limited by nature=highly intrusive techniques but new approaches and targets have been recently introduced. Specifically, renal nerve ablation has been introduced and the first attempts to employ this technique for treatment of cardiac arrhythmias give as a promise of new therapeutic avenues in near future. This review focuses on the possible role of renal denervation in treatment of atrial fibrillation, the contemporary evidence supporting this approach, and the ongoing trials to establish its therapeutic role.

Ethanol infusion in the vein of Marshall leads to parasympathetic denervation of the human left atrium: implications for atrial fibrillation

OBJECTIVES

This study sought to determine whether ethanol infusion in the vein of Marshall (VOM) can ablate intrinsic cardiac nerves (ICN).

BACKGROUND

ICN cluster around the left atrial epicardium and are implicated in the genesis of atrial fibrillation (AF).

METHODS

Patients undergoing catheter AF ablation underwent adjunctive ethanol injection in the VOM. A multipolar catheter was introduced in the VOM and used for high-frequency stimulation (HFS), either as HFS with P-wave synchronized (SynchHFS), 30 pulses, 100 Hz (n = 8) or as HFS with 3 to 10 s bursts (BurstHFS), 33 Hz (n = 72) at 25 mA for 1-ms duration. Atrioventricular (AV) nodal conduction slowing (asystole >2 s or R-R interval prolongation >50%) and AF inducibility were assessed before and after VOM ethanol infusion. Up to 4 1-ml infusions of 98% ethanol were delivered via an angioplasty balloon in the VOM.

RESULTS

SynchHFS induced AF in 8 of 8 patients. In 4 of 8 AF initiated spontaneously without VOM capture. No parasympathetic responses were elicited by SynchHFS. BurstHFS was performed in 32 patients undergoing de novo AF ablation (Group 1) and 40 patients undergoing repeat ablation (Group 2). Parasympathetic responses were found in all 32 Group 1 patients and in 75% of Group 2 patients. After VOM ethanol infusion, parasympathetic responses were abolished in all patients (both groups). There were no acute complications related to VOM ethanol infusion.

CONCLUSIONS

The VOM contains ICN that connect with the AV node and can trigger AF. Retrograde ethanol infusion in the VOM reliably eliminates local ICN responses. The VOM is a vascular route for ICN-targeting therapies.

Comparative Effectiveness of Wide Antral Versus Ostial Pulmonary Vein Isolation

Background—

For the past decade, electric pulmonary vein isolation (PVI) has become a procedure implemented worldwide for the treatment of atrial fibrillation. Currently, 2 main approaches are used for PVI: ostial isolation of the PVs and wide antral PVI. The aims of this systematic review are to evaluate the relative merits of each technique with a pooled comparative analysis of efficacy and complications.

Methods and Results—

Studies were identified by searching electronic databases for studies on ostial versus antral PVI. Information was extracted from each included trial. Odds ratio was the primary measure of treatment effect or side effects. The proportion of patients with recurrences of atrial fibrillation or other atrial tachyarrhythmias was evaluated at the end of the follow-up periods in 12 trials, including 1183 patients. The recurrence rate of total supraventricular arrhythmias was significantly lower in wide antral than in segmental PVI group (odds ratio, 0.42; 95% confidence interval, 0.32–0.56; P <0.00001). Atrial fibrillation recurrence was significantly lower in the wide antral group (odds ratio, 0.33; 95% confidence interval, 0.24–0.46; P <0,00001). A trend toward a higher incidence of left atrial tachycardia occurrence in the wide antral circumferential ablation group was detected, which did not reach statistical significance (odds ratio, 1.53; 95% confidence interval, 0.88–2.69; P =0.13).

Conclusions—

Our primary finding is that PVI performed with a wide antral approach is more effective than ostial PVI in achieving freedom from total atrial tachyarrhythmia recurrence at long-term follow-up.

Autonomic denervation added to pulmonary vein isolation for paroxysmal atrial fibrillation: a randomized clinical trial

OBJECTIVES

The aim of this study was to investigate whether the combination of conventional pulmonary vein isolation (PVI) by circumferential antral ablation with ganglionated plexi (GP) modification in a single ablation procedure, yields higher success rates than PVI or GP ablation alone, in patients with paroxysmal atrial fibrillation (PAF).

BACKGROUND

Conventional PVI transects the major left atrial GP, and it is possible that autonomic denervation by inadvertent GP ablation plays a central role in the efficacy of PVI.

METHODS

A total of 242 patients with symptomatic PAF were recruited and randomized as follows: 1) circumferential PVI (n = 78); 2) anatomic ablation of the main left atrial GP (n = 82); or 3) circumferential PVI followed by anatomic ablation of the main left atrial GP (n = 82). The primary endpoint was freedom from atrial fibrillation (AF) or other sustained atrial tachycardia (AT), verified by monthly visits, ambulatory electrocardiographic monitoring, and implantable loop recorders, during a 2-year follow-up period.

RESULTS

Freedom from AF or AT was achieved in 44 (56%), 39 (48%), and 61 (74%) patients in the PVI, GP, and PVI+GP groups, respectively (p = 0.004 by log-rank test). PVI+GP ablation strategy compared with PVI alone yielded a hazard ratio of 0.53 (95% confidence interval: 0.31 to 0.91; p = 0.022) for recurrence of AF or AT. Fluoroscopy duration was 16 ± 3 min, 20 ± 5 min, and 23 ± 5 min for PVI, GP, and PVI+GP groups, respectively (p < 0.001). Post-ablation atrial flutter did not differ between groups: 5.1% in PVI, 4.9% in GP, and 6.1% in PVI+GP. No serious adverse procedure-related events were encountered.

CONCLUSIONS

Addition of GP ablation to PVI confers a significantly higher success rate compared with either PVI or GP alone in patients with PAF.

Characterization of the left atrial neural network and its impact on autonomic modification procedures

BACKGROUND

Left atrial (LA) ganglionated plexi (GP) are part of the intrinsic cardiac autonomic nervous system and implicated in the pathogenesis of atrial fibrillation. High frequency stimulation is used to identify GP sites in humans. The effect of ablation on neural pathways connecting GPs in humans is unknown.

METHODS AND RESULTS

Thirty patients undergoing LA ablation with autonomic modification were recruited. In patients with persistent atrial fibrillation, endocardial continuous high frequency stimulation identified GP sites producing AV block. After right lower GP ablation (N=5), 2 of 15 sites remained positive, whereas after ablation of other GPs (N=5), leaving right lower GP intact, all 19 sites remained positive (right lower GP versus other GP, P<0.005), indicating that neural pathways between LAGPs and the AV node are via the right lower GP. In 20 patients with paroxysmal atrial fibrillation, synchronized high frequency stimulation identified sites initiating pulmonary vein (PV) ectopy. After PV isolation (N=8), no sites remained positive. After local GP ablation (N=9), 3 of 14 sites remained positive, suggesting neural connections to the PV were disrupted by both PV isolation and GP ablation. Heart rate variability indices reduced significantly after right upper GP ablation alone, suggesting that neural pathways from the LA to the SA node travel via the right upper GP.

CONCLUSIONS

We have demonstrated neural pathways connecting LA GPs with the PVs, AV node, and SA node. The effects of high frequency stimulation at GP sites can be prevented by ablating the GP site or the neural pathway. This further delineates the mechanism via which PV isolation prevents atrial fibrillation and highlights important caveats for autonomic modification end points.

Role of Stress in Cardiac Arrhythmias

Stress is a major trigger of cardiac arrhythmias; it exerts profound effects on electrophysiology of the cardiomyocytes and the cardiac rhythm. Psychological and physiological stressors impact the cardiovascular system through the autonomic nervous system (ANS). While stressors vary, properties of the stress response at the level of cardiovascular system (collectively referred to as the autonomic cardiovascular responses) are similar and can be studied independently from the properties of specific stressors. Here, we will review the clinical and experimental evidence linking common stressors and atrial arrhythmias. Specifically, we will describe the impact of psychological and circadian stressors on ANS activity and arrhythmogenesis. We will also review studies examining relationships between autonomic cardiovascular responses and cardiac arrhythmias in ambulatory and laboratory settings.

Blood pressure and autonomic responses to electrical stimulation of the renal arterial nerves before and after ablation of the renal artery

Radiofrequency (RF) catheter ablation of the renal artery is therapeutic in patients with drug-refractory essential hypertension. This study was designed to examine the role of the renal autonomic nerves and of RF application from inside the renal artery in the regulation of blood pressure (BP). An open irrigation catheter was inserted into either the left or right renal artery in 8 dogs. RF current (17 ± 2 watts) was delivered to one renal artery. Electrical autonomic nerve stimulation was applied to each renal artery before and after RF ablation. BP, heart rate, indices of heart rate variability, and serum catecholamines were analyzed. Before RF ablation, electrical autonomic nerve stimulation of either renal artery increased BP from 150 ± 16/92 ± 15 to 173 ± 21/105 ± 16 mm Hg. After RF ablation, BP increased similarly when the nonablated renal artery was electrically stimulated, although the rise in BP was attenuated when the ablated renal artery was stimulated. Serum catecholamines and sympathetic nerve indices of heart rate variability increased when electrical autonomic nerve stimulation was applied before RF ablation and to the nonablated renal artery after RF ablation, although it changed minimally when the ablated renal artery was stimulated, suggesting interconnectivity between afferent renal nerve stimulation and systemic sympathetic activity. Renal artery angiogram showed no apparent injury after RF ablation. In conclusion, electrical stimulation of the renal arterial autonomic nerves increases BP via an increase in central sympathetic nervous activity. This response might be used to determine the target ablation site and end point of renal artery RF ablation.