Interactive atrial neural network: Determining the connections between ganglionated plexi

Ganglionated Plexus Ablation Procedures to Treat Vasovagal Syncope

Vasovagal syncope (VVS) refers to a heterogeneous group of conditions whereby the cardiovascular reflexes normally controlling the circulation are interrupted irregularly in response to a trigger, resulting in vasodilation, bradycardia, or both. VVS affects one-third of the population at least once in their lifetime or by the age of 60, reduces the quality of life, and may cause disability affecting certain routines. It poses a considerable economic burden on society, and, despite its prevalence, there is currently no proven pharmacological treatment for preventing VVS. The novel procedure of ganglionated plexus (GP) ablation has emerged rapidly in the past two decades, and has been proven successful in treating syncope. Several parameters influence the success rate of GP ablation, including specific ablation sites, localization and surgical techniques, method of access, and the integration of other interventions. This review aims to provide an overview of the existing literature on the physiological aspects and clinical effectiveness of GP ablation in the treatment of VVS. Specifically, we explore the association between GPs and VVS and examine the impact of GP ablation procedures as reported in human clinical trials. Our objective is to shed light on the therapeutic significance of GP ablation in eliminating VVS and restoring normal sinus rhythm, particularly among young adults affected by this condition.

Bradyarrhythmia in a marathonist: Cardiac vagal denervation as alternative treatment

Although not routinely used, cardioneuroablation or modulation of the cardiac autonomic nervous system has been proposed as an alternative approach to treat young individuals with enhanced vagal tone and significant atrioventricular (AV) disturbances. We report the case of a 42-year-old athlete with prolonged ventricular pauses associated with sinus bradycardia and paroxysmal episodes of AV block (maximum of 6.6 s) due to enhanced vagal tone who was admitted to our hospital for pacemaker implantation. Cardiac magnetic resonance and stress test were normal. Although he was asymptomatic, safety concerns regarding possible neurological damage and sudden cardiac death were raised, and he accordingly underwent electrophysiological study (EPS) and cardiac autonomic denervation. Mapping and ablation were anatomically guided and radiofrequency pulses were delivered at empirical sites of ganglionated plexi. Modulation of the parasympathetic system was confirmed through changes in heart rate and AV nodal conduction properties associated with a negative cardiac response to atropine administration. After a follow-up of nine months, follow-up 24-hour Holter revealed an increase in mean heart rate and no AV disturbances, with rare non-significant ventricular pauses, suggesting that this technique may become a safe and efficient procedure in this group of patients.

A sudden increase in heart rate during ablation of the right superior pulmonary venous vestibule is correlated with pain-relief in patients undergoing atrial fibrillation ablation

BACKGROUND

A sudden increase in heart rate (HR) during ablation of the right superior pulmonary venous vestibule (RSPVV) is often detected in patients undergoing circumferential pulmonary vein isolation (CPVI). In our clinical practices, we observed that some patients had few complaints of pain during the procedures under conscious sedation.

AIM

We aimed to investigate whether there is a correlation between a sudden increase in HR during AF ablation of the RSPVV and pain relief under conscious sedation.

METHODS

We prospectively enrolled 161 consecutive paroxysmal AF patients who underwent the first ablation from July 1, 2018, to November 30, 2021. Patients were assigned to the R group when they had a sudden increase in HR during the ablation of the RSPVV, and the others were assigned to the NR group. Atrial effective refractory period and HR were measured before and after the procedure. Visual Analogue Scale (VAS) scores, vagal response (VR) during ablation, and the amount of fentanyl used were also documented.

RESULTS

Eighty-one patients were assigned to the R group, and the remaining 80 were assigned to the NR group. The post-ablation HR (86.3 ± 8.8 vs. 70.0 ± 9.4 b/min; p ≤ 0.001) was higher in the R group than in pre-ablation. Ten patients in the R group had VRs during CPVI, as well as 52 patients in the NR group. The VAS score [2.3 (1.3-3.4) vs. 6.0 (4.4-6.9); p ≤ 0.001)] and the amount of fentanyl used (107 ± 12 vs. 172 ± 26 ug; p ≤ 0.001) were significantly lower in the R group.

CONCLUSION

A sudden increase in HR during the ablation of the RSPVV was correlated with pain relief in patients undergoing AF ablation under conscious sedation.

Selection of patients with symptomatic vagal-induced sinus node dysfunction: Who will be the best candidate for cardioneuroablation?

Sinus node dysfunction is a multifaceted disorder with variable manifestations, the prevalence of which increases with age. In a specific group of patients, excessive vagal activity may be the sole cause for this condition. These patients are characterized as having recurrent daytime symptoms attributed to bradyarrhythmia, no evidence of organic sinus node lesions, cardiac vagal overactivation, and are non-elderly. For sinus node dysfunction patients, a permanent pacemaker implantation appears to be the ultimate solution, although it is not an etiological treatment. Cardioneuroablation is a promising emerging therapy that can fundamentally eliminate symptoms in a highly selective sub-set of sinus node dysfunction patients by cardiac vagal nerve denervation. Denervation with ablation for vagal-induced sinus node dysfunction can effectively improve sinus bradycardia and reduce syncope. To date, guidelines for selection of suitable candidates for cardioneuroablation remain lacking. The primary objective of this study was to distinguish the nature of abnormal sinus node function and to find methods for quantifying vagal tone. Clear selection criteria could help physicians in identification of patients with autonomic imbalance, thereby maximizing patient benefits and the success rate of cardioneuroablations.

Neuromodulation therapy for atrial fibrillation

Atrial fibrillation has a multifactorial pathophysiology influenced by cardiac autonomic innervation. Both sympathetic and parasympathetic influences are profibrillatory. Innovative therapies targeting the neurocardiac axis include catheter ablation or pharmacologic suppression of ganglionated plexi, renal sympathetic denervation, low-level vagal stimulation, and stellate ganglion blockade. To date, these therapies have variable efficacy. As our understanding of atrial fibrillation and the cardiac nervous system expands, our approach to therapeutic neuromodulation will continue evolving for the benefit of those with AF.

Calcium-Induced Autonomic Denervation in Patients With Post-Operative Atrial Fibrillation

BACKGROUND

Post-operative atrial fibrillation (POAF) is associated with worse long-term cardiovascular outcomes.

OBJECTIVES

This study hypothesized that injecting calcium chloride (CaCl₂) into the major atrial ganglionated plexi (GPs) during isolated coronary artery bypass grafting (CABG) can reduce the incidence of POAF by calcium-induced autonomic neurotoxicity.

METHODS

This proof-of-concept study randomized 200 patients undergoing isolated, off-pump CABG to CaCl₂ (n = 100) or sodium chloride (sham, n = 100) injection. Two milliliters of CaCl₂ (5%) or sodium chloride (0.9%) was injected into the 4 major atrial GPs during CABG. All patients received 7-day continuous telemetry and Holter monitoring. The primary outcome was incidence of POAF (≥30 s) in 7 days. Secondary outcomes included length of hospitalization, POAF burden, average ventricular rate during AF, plasma level of inflammatory markers, and actionable antiarrhythmic therapy to treat POAF.

RESULTS

The POAF incidence was reduced from 36% to 15% (hazard ratio: 0.366; 95% confidence interval: 0.211 to 0.635; p = 0.001). Length of hospitalization did not differ between the 2 groups. POAF burden (first 7 post-operative days), the use of amiodarone or esmolol, and the incidence of atrial couplets and nonsustained atrial tachyarrhythmias were significantly reduced in the CaCl₂ group. Heart rate variability data showed a decrease in both high-frequency and low-frequency power in the CaCl₂ group with a preserved low-frequency/high-frequency ratio, suggesting that the sympathetic/parasympathetic balance was not perturbed by CaCl₂ injection.

CONCLUSIONS

Injection of CaCl₂ into the 4 major atrial GPs reduced the POAF hazard by 63%. Inhibition of GP function by Ca-mediated neurotoxicity may underlie the therapeutic effect. (Calcium Autonomic Denervation Prevents Postoperative Atrial Fibrillation; ChiCTR1800019276).

Innervation and Neuronal Control of the Mammalian Sinoatrial Node a Comprehensive Atlas

[Figure: see text].

Atrial fibrillation and autonomic nervous system: A translational approach to guide therapeutic goals

The autonomic nervous system (ANS) is known to play an important role in the genesis and maintenance of atrial fibrillation (AF). Biomolecular and genetic mechanisms, anatomical knowledges with recent diagnostic techniques acquisitions, both invasive and non-invasive, have enabled greater therapeutic goals in patients affected by AF related to ANS imbalance. Catheter ablation of ganglionated plexi (GP) in the left and right atrium has been proposed in varied clinical conditions. Moreover interesting results arise from renal sympathetic denervation and vagal nerve stimulation. Despite all this, in the scenario of ANS modulation translational strategies we necessary must consider the treatment or correction of dynamic factors such as obesity, obstructive sleep apnea, lifestyle, food, and stress. Finally, new antiarrhythmic drugs, gene therapy and "ablatogenomic" could be represent exciting future therapeutic perspectives.

Recording Intrinsic Nerve Activity at the Sinoatrial Node in Normal Dogs With High-Density Mapping

BACKGROUND

It is known that autonomic nerve activity controls the sinus rate. However, the coupling between local nerve activity and electrical activation at the sinoatrial node (SAN) remains unclear. We hypothesized that we would be able to record nerve activity at the SAN to investigate if right stellate ganglion (RSG) activation can increase the local intrinsic nerve activity, accelerate sinus rate, and change the earliest activation sites.

METHODS

High-density mapping of the epicardial surface of the right atrium including the SAN was performed in 6 dogs during stimulation of the RSG and after RSG stellectomy. A radio transmitter was implanted into 3 additional dogs to record RSG and local nerve activity at the SAN.

RESULTS

Heart rate accelerated from 108±4 bpm at baseline to 125±7 bpm after RSG stimulation (P=0.001), and to 132±7 bpm after apamin injection (P<0.001). Both electrical RSG stimulation and apamin injection induced local nerve activity at the SAN with the average amplitudes of 3.60±0.72 and 3.86±0.56 μV, respectively. RSG stellectomy eliminated the local nerve activity and decreased the heart rate. In ambulatory dogs, local nerve activity at the SAN had a significantly higher average Pearson correlation to heart rate (0.72±0.02, P=0.001) than RSG nerve activity to HR (0.45±0.04, P=0.001).

CONCLUSIONS

Local intrinsic nerve activity can be recorded at the SAN. Short bursts of these local nerve activities are present before each atrial activation during heart rate acceleration induced by stimulation of the RSG.

The Intrinsic Cardiac Nervous System and Its Role in Cardiac Pacemaking and Conduction

The cardiac autonomic nervous system (CANS) plays a key role for the regulation of cardiac activity with its dysregulation being involved in various heart diseases, such as cardiac arrhythmias. The CANS comprises the extrinsic and intrinsic innervation of the heart. The intrinsic cardiac nervous system (ICNS) includes the network of the intracardiac ganglia and interconnecting neurons. The cardiac ganglia contribute to the tight modulation of cardiac electrophysiology, working as a local hub integrating the inputs of the extrinsic innervation and the ICNS. A better understanding of the role of the ICNS for the modulation of the cardiac conduction system will be crucial for targeted therapies of various arrhythmias. We describe the embryonic development, anatomy, and physiology of the ICNS. By correlating the topography of the intracardiac neurons with what is known regarding their biophysical and neurochemical properties, we outline their physiological role in the control of pacemaker activity of the sinoatrial and atrioventricular nodes. We conclude by highlighting cardiac disorders with a putative involvement of the ICNS and outline open questions that need to be addressed in order to better understand the physiology and pathophysiology of the ICNS.

Ganglionated Plexi Ablation for the Treatment of Atrial Fibrillation

Atrial fibrillation (AF) is the most common type of cardiac arrhythmia and is associated with significant morbidity and mortality. The autonomic nervous system (ANS) plays an important role in the initiation and development of AF, causing alterations in atrial structure and electrophysiological defects. The intrinsic ANS of the heart consists of multiple ganglionated plexi (GP), commonly nestled in epicardial fat pads. These GPs contain both parasympathetic and sympathetic afferent and efferent neuronal circuits that control the electrophysiological properties of the myocardium. Pulmonary vein isolation and other cardiac catheter ablation targets including GP ablation can disrupt the fibers connecting GPs or directly damage the GPs, mediating the benefits of the ablation procedure. Ablation of GPs has been evaluated over the past decade as an adjunctive procedure for the treatment of patients suffering from AF. The success rate of GP ablation is strongly associated with specific ablation sites, surgical techniques, localization techniques, method of access and the incorporation of additional interventions. In this review, we present the current data on the clinical utility of GP ablation and its significance in AF elimination and the restoration of normal sinus rhythm in humans.

The ectopy-triggering ganglionated plexuses in atrial fibrillation

BACKGROUND

Epicardial ganglionated plexuses (GP) have an important role in the pathogenesis of atrial fibrillation (AF). The relationship between anatomical, histological and functional effects of GP is not well known. We previously described atrioventricular (AV) dissociating GP (AVD-GP) locations. In this study, we hypothesised that ectopy triggering GP (ET-GP) are upstream triggers of atrial ectopy/AF and have different anatomical distribution to AVD-GP.

OBJECTIVES

We mapped and characterised ET-GP to understand their neural mechanism in AF and anatomical distribution in the left atrium (LA).

METHODS

26 patients with paroxysmal AF were recruited. All were paced in the LA with an ablation catheter. High frequency stimulation (HFS) was synchronised to each paced stimulus for delivery within the local atrial refractory period. HFS responses were tagged onto CARTO™ 3D LA geometry. All geometries were transformed onto one reference LA shell. A probability distribution atlas of ET-GP was created. This identified high/low ET-GP probability regions.

RESULTS

2302 sites were tested with HFS, identifying 579 (25%) ET-GP. 464 ET-GP were characterised, where 74 (16%) triggered ≥30s AF/AT. Median 97 (IQR 55) sites were tested, identifying 19 (20%) ET-GP per patient. >30% of ET-GP were in the roof, mid-anterior wall, around all PV ostia except in the right inferior PV (RIPV) in the posterior wall.

CONCLUSION

ET-GP can be identified by endocardial stimulation and their anatomical distribution, in contrast to AVD-GP, would be more likely to be affected by wide antral circumferential ablation. This may contribute to AF ablation outcomes.

Cardioneuroablation in the Management of Vasovagal Syncope, Sinus Node Dysfunction, and Functional Atrioventricular Block - Techniques

Cardioneuroablation is an emerging therapy to treat vasovagal syncope, functional atrioventricular block and sinus dysfunction. Currently, there are several effective approaches due to the complex modulation of autonomic nervous system. In this review, we describe techniques of this innovative therapy based on published literature and our experiences.

A novel strategy to treat vaso-vagal syncope: Cardiac neuromodulation by cryoballoon pulmonary vein isolation

Background

Clinical management of vaso-vagal syncope (VVS) remains challenging since no therapy has proven to completely prevent VVS recurrence.

Objective

The purpose of this study was to analyze the mid-term outcome of cryoballoon (CB) cardioneuroablation achieved by pulmonary vein isolation (PVI) in patients with VVS.

Methods

Patients who underwent CB cardioneuroablation in our centers between January 2014 to June 2018 were included. All patients had a history of VVS or pre-syncope despite therapeutic attempts with medical and/or pacing treatments. Patients were excluded in case of structural heart diseases, cerebrovascular diseases or suspected drug-related syncope. Both heart rate (HR) and atrio-ventricular (AV) interval were analyzed on the 12-lead electrocardiogram (ECG) the day before the procedure, the day after, and in the follow-up.

Results

In total, 26 patients (76.9% males, 37.5 ± 9.0 years old) were included. All patients underwent a successful procedure with the 28 mm second-generation Arctic Front Advance CB. No major complication occurred. At a mean follow-up of 20.1 ± 11.6 months the freedom from VVS or reflex pre-syncope was 83,7%, with 22 patients free from any clinical recurrence. Basal HR significantly increased the day after the procedure (57.2 bpm vs 78.3 bpm, p < 0.001), while at the final follow-up it stabilized at a value halfway between the 2 previous ones (69.8 bpm, p = 0.0086). The AV interval didn’t modify significantly after the procedure.

Conclusion

Endocardial autonomic denervation achieved by CB PVI appears to be an effective and safe treatment option for patients with refractory VVS and reflex pre-syncope.

Autonomic Nervous System Dysfunction: JACC Focus Seminar

Autonomic nervous system control of the heart is a dynamic process in both health and disease. A multilevel neural network is responsible for control of chronotropy, lusitropy, dromotropy, and inotropy. Intrinsic autonomic dysfunction arises from diseases that directly affect the autonomic nerves, such as diabetes mellitus and the syndromes of primary autonomic failure. Extrinsic autonomic dysfunction reflects the changes in autonomic function that are secondarily induced by cardiac or other disease. An array of tests interrogate various aspects of cardiac autonomic control in either resting conditions or with physiological perturbations from resting conditions. The prognostic significance of these assessments have been well established. Clinical usefulness has not been established, and the precise mechanistic link to mortality is less well established. Further efforts are required to develop optimal approaches to delineate cardiac autonomic dysfunction and its adverse effects to develop tools that can be used to guide clinical decision-making.

Vagal responses during cardioneuroablation on different ganglionated plexi: Is there any role of ablation strategy?

BACKGROUND

Cardioneuroablation has been used to treat vagally mediated bradyarrhythmias (VMB). The aim of this study is to assess vagal response (VR) characteristics during radiofrequency catheter ablation (RFCA) with different ganglionated plexus (GP) order.

METHODS

A total of 49 consecutive patients with VMB who underwent cardioneuroablation were enrolled. GPs were identified by electroanatomic-mapping-guided strategy. After all GP targets have been identified, patients were divided into 2 groups according to GP ablation strategy. In the left side first group, ablation order of GPs were left superior GP (LSGP), left inferior GP (LIGP), right superior GP (RSGP), and right inferior GP (RIGP). In the right side first group, ablation order was RSGP, RIGP, LSGP, and LIGP.

RESULTS

In the left side first group, LSGP was the most common GP site at which a VR was observed (36 of 40 cases, 90%). LIGP causes a VR in 9 of 40 (22.5%) cases. In the right side first group, VR was seen only 2 of 9 (22.2%) cases. Comparison of ablation strategy demonstrated a significant difference in VR during ablation on LSGP between groups. Despite, LSGP was the most common GP site at which a VR was observed both groups (90% in left side first group vs 11.1% in right side first group, p < 0.0001). In remaining GPs, VRs were not dependent on the ablation strategy and were not statistically different between groups.

CONCLUSION

The present study demonstrates that the characteristics of VR during RFCA might change according to ablation order of GPs.

Avoidance of Vagal Response During Circumferential Pulmonary Vein Isolation

Background:

Circumferential pulmonary vein isolation (CPVI) often cause unavoidable vagal reflexes during procedure due to the coincidental modification of ganglionated plexus which are located on pulmonary vein (PV) antrum. The right anterior ganglionated plexi (RAGP) which located at superoanterior area of right superior PV antrum is an essential station to regulate the cardiac autonomic nerve activities and is easily coincidentally ablated during CPVI. The aim of this study is to assess the effect of RAGP ablation on vagal response (VR) during CPVI.

Methods:

A total of 80 patients with paroxysmal atrial fibrillation who underwent the first time CPVI were prospectively enrolled and randomly assigned to 2 groups: group A (n=40), CPVI started with right PVs at RAGP site; group B (n=40): CPVI started with left PVs first, and the last ablation site is RAGP. Electrophysiological parameters include basal cycle length, A-H interval, H-V interval, sinus node recovery time, and atrioventricular node Wenckebach point were recorded before and after CPVI procedure.

Results:

During CPVI, the positive VR were only observed on 1 patient in group A and 25 patients in group B ( P <0.001). A total of 21 patients with positive VR in group B needed for temporary ventricular pacing during procedure, while the only patient with positive VR in group A did not need for temporary ventricular pacing ( P <0.001). Compared with baseline, basal cycle length, sinus node recovery time, and atrioventricular node Wenckebach point were decreased significantly after CPVI procedure in both groups (all P <0.05) and without differences between 2 groups.

Conclusions:

Circumferential PV isolation initiated from RAGP could effectively inhibit VR occurrence and significantly increase heart rate during procedure.

Step-by-Step Cardioneuroablation Approach in Two Patients with Functional Atrioventricular Block

Parasympathetic overactivity may cause functional atrioventricular block episodes and necessitate pacemaker implantation in symptomatic cases and those refractory to conventional therapies. In these patients, if it can be clearly demonstrated that there is no structural damage in the conduction system, elimination of the vagal activity based on radiofrequency catheter ablation of main ganglionated plexi around the heart, which is called as cardioneuroablation, might be a rational approach. In this review article, we try to discuss patient selection and procedural steps suitable for cardioneuroablation based on two patients with functional atrioventricular block.

Is Vagal Response During Left Atrial Ganglionated Plexi Stimulation a Normal Phenomenon?

Background:

Ganglionated plexi (GPs) play an important role in both the initiation and maintenance of atrial fibrillation (AF). GPs can be located by using continuous high-frequency stimulation (HFS) to elicit a vagal response, but whether the vagal response phenomenon is common to patients without AF is unknown.

Methods:

HFS of the left atrial GPs was performed in 42 patients (aged 58.0±10.2 years) undergoing ablation for AF and 21 patients (aged 53.2±12.8 years) undergoing ablation for a left-sided accessory pathway. The HFS (20 Hz, 25 mA, 10-ms pulse duration) was applied for 5 seconds at 3 sites within the presumed anatomic area of each of the 5 major left atrial GPs (for a total of 15 sites per patient). We defined vagal response to HFS as prolongation of the R-R interval by >50% in comparison to the mean pre-HFS R-R interval averaged over 10 beats and active-GP areas as areas in which a vagal response was elicited.

Results:

Overall, more active-GP areas were found in the AF group patients than in the non-AF group patients, and at all 5 major GPs, the maximum R-R interval during HFS was significantly prolonged in the AF patients. After multivariate adjustment, association was established between the total number of vagal response sites and the presence of AF.

Conclusions:

The significant increase in vagal responses elicited in patients with AF compared with responses in non-AF patients suggests that vagal responses to HFS reflect abnormally increased GP activity specific to AF substrates.

Micro-RNAs Are Related to Epicardial Adipose Tissue in Participants With Atrial Fibrillation: Data From the MiRhythm Study

Introduction: Epicardial adipose tissue (EAT) has been linked to incidence and recurrence of atrial fibrillation (AF), but the underlying mechanisms that mediate this association remain unclear. Circulating microRNAs (miRNAs) contribute to the regulation of gene expression in cardiovascular diseases, including AF. Thus, we sought to test the hypothesis that circulating miRNAs relate to burden of EAT.

Methods: We examined the plasma miRNA profiles of 91 participants from the miRhythm study, an ongoing study examining associations between miRNA and AF. We quantified plasma expression of 86 unique miRNAs commonly expressed in cardiomyocytes using quantitative reverse transcriptase polymerase chain reaction (qPCR). From computed tomography, we used validated methods to quantify the EAT area surrounding the left atrium (LA) and indexed it to body surface area (BSA) to calculate indexed LA EAT (iLAEAT). Participants were divided into tertiles of iLAEAT to identify associations with unique miRNAs. We performed logistic regression analyses adjusting for factors associated with AF to examine relations between iLAEAT and miRNA. We performed further bioinformatics analysis of miRNA predicted target genes to identify potential molecular pathways are regulated by the miRNAs.

Results: The mean age of the participants was 59 ± 9, 35% were women, and 97% were Caucasian. Participants in the highest tertile of iLAEAT were more likely to have hypertension, heart failure, and thick posterior walls. In regression analyses, we found that miRNAs 155-5p (p < 0.001) and 302a-3p (p < 0.001) were significantly associated with iLAEAT in patients with AF. The predicted targets of the miRNAs identified were implicated in the regulation of cardiac hypertrophy, adipogenesis, interleukin-8 (IL-8), and nerve growth factor (NGF) signaling.

Conclusion: miRNA as well as EAT have previously been linked to AF. Our finding that iLAEAT and miRNAs 155-5p and 302a-3p are associated suggest a possible direct link to between these entities in the development and maintenance of AF. Further research is needed to study causal relationships between these biomarkers.

Right anterior ganglionated plexus: The primary target of cardioneuroablation?

BACKGROUND

Catheter ablation of ganglionated plexus (GP) as cardioneuroablation in the left atrium (LA) has been used to treat vasovagal syncope (VVS).

OBJECTIVE

The purpose of this study was to assess the effects of ablation of GPs on heart rate and to observe the acute, short-term, and long-term effects after cardioneuroablation.

METHODS

A total of 115 consecutive patients with VVS who underwent cardioneuroablation were enrolled. GPs of the LA were identified by high-frequency stimulation and/or anatomic landmarks being targeted by radiofrequency catheter ablation.

RESULTS

During ablation of right anterior ganglionated plexus (RAGP), heart rate increased from 61.3 ± 12.2 bpm to 82.4 ± 14.7 bpm (P <.001), whereas during ablation of other GPs only vagal responses were observed. During follow-up of 21.4 ± 13.1 months (median 18 months), 106 participants (92.2%) had no recurrence of syncope or presyncope. Holter data showed that minimal heart rate significantly increased at all follow-up time points (all P<.05), and mean heart rate remained higher than baseline 12 months after ablation (P = .001).

CONCLUSION

Cardioneuroablation via GP ablation in the LA effectively inhibited the recurrence of VVS. Ablation of RAGP could increase heart rate immediately and for the long term. This unique phenomenon may provide a new potential approach for treatment of neural reflex syncope or bradyarrhythmias.

Sympathetic Nervous System Activation and Its Modulation: Role in Atrial Fibrillation

The autonomic nervous system (ANS) has a significant influence on the structural integrity and electrical conductivity of the atria. Aberrant activation of the sympathetic nervous system can induce heterogeneous changes with arrhythmogenic potential which can result in atrial tachycardia, atrial tachyarrhythmias and atrial fibrillation (AF). Methods to modulate autonomic activity primarily through reduction of sympathetic outflow reduce the incidence of spontaneous or induced atrial arrhythmias in animal models and humans, suggestive of the potential application of such strategies in the management of AF. In this review we focus on the relationship between the ANS, sympathetic overdrive and the pathophysiology of AF, and the potential of sympathetic neuromodulation in the management of AF. We conclude that sympathetic activity plays an important role in the initiation and maintenance of AF, and modulating ANS function is an important therapeutic approach to improve the management of AF in selected categories of patients. Potential therapeutic applications include pharmacological inhibition with central and peripheral sympatholytic agents and various device based approaches. While the role of the sympathetic nervous system has long been recognized, new developments in science and technology in this field promise exciting prospects for the future.

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.

Atrial Innervation Patterns of Intrinsic Cardiac Autonomic Nerves

BACKGROUND

Although ganglionated plexi (GPs) are important in the pathogenesis of arrhythmia, their patterns of atrial innervation have remained unclear. We investigated patterns of GP innervation to cardiac atria and the neuroanatomical interconnections among GPs in an animal model.

METHODS

Atrial innervation by GPs was evaluated in 10 mongrel dogs using a retrograde neuronal tracer (cholera toxin subunit B [CTB] conjugated with fluorescent dyes). In Experiment 1, CTB was injected into the atria. In Experiment 2, CTB was injected into the major GP, including the anterior right GP (ARGP), inferior right GP (IRGP), superior left GP (SLGP), and ligament of Marshall (LOM). After 7 days, the GPs were examined for the presence of tracer-positive neurons.

RESULTS

GPs in either right or left-side were innervating to both the same and opposite sides of the atrium. In quantitative analysis, right-sided GPs, especially ARGP, showed numerical predominance in atrial innervation. Based on the proportion of CTB-labeled ganglion in each GP, atrial innervation by GPs showed a tendency of laterality. In Experiment 2, CTB that was injected to a particular GP widely distributed in different GP. ARGP projected the largest number of innervating neurons to the IRGP, SLGP and LOM.

CONCLUSION

This study demonstrated that GPs project axons widely to both the same and opposite sides of atria. ARGP played a dominant role in atrial innervation. Furthermore, there were numerous neuroanatomical interconnections among GPs. These findings about neuronal innervation and interconnections of GPs could offer useful information for understanding intrinsic cardiac nervous system neuroanatomy.

Effects of Vagal Nerve Stimulation on Ganglionated Plexi Nerve Activity and Ventricular Rate in Ambulatory Dogs With Persistent Atrial Fibrillation

OBJECTIVES

This study was designed to test the hypothesis that low-level vagal nerve stimulation (VNS) reduces the ventricular rate (VR) during atrial fibrillation (AF) through the activation of the inferior vena cava (IVC)-inferior atrial ganglionated plexus nerve activity (IAGPNA).

BACKGROUND

Increased IVC-IAGPNA can suppress atrioventricular node conduction and slow VR in canine models of AF.

METHODS

Persistent AF was induced in 6 dogs and the IVC-IAGPNA, right vagal nerve activity, left vagal nerve activity, and an electrocardiogram were recorded. After persistent AF was documented, VNS was programed to 14 s "on" and 1.1 min "off." After 1 week, the VNS was reprogramed to 3 min off and stimulation continued for another week. Neural remodeling of the stellate ganglion (SG) was assessed with tyrosine hydroxylase staining and terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling staining.

RESULTS

Average IVC-IAGPNA was increased during both VNS 1.1 min off (8.20 ± 2.25 μV [95% confidence interval (CI): 6.33 to 9.53 μV]; p = 0.002) and 3 min off (7.96 ± 2.03 μV [95% CI: 6.30 to 9.27 μV]; p = 0.001) versus baseline (7.14 ± 2.20 μV [95% CI: 5.35 to 8.52 μV]). VR was reduced during both VNS 1.1 min off (123.29 ± 6.29 beats/min [95% CI: 116.69 to 129.89 beats/min]; p = 0.001) and 3 min off (120.01 ± 4.93 beats/min [95% CI: 114.84 to 125.18 beats/min]; p = 0.001) compared to baseline (142.04 ± 7.93 bpm [95% CI: 133.72 to 150.37]). Abnormal regions were observed in the left SG, but not in the right SG. Terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling-positive neurons were found in 22.2 ± 17.2% [95% CI: 0.9% to 43.5%] of left SG cells and 12.8 ± 8.4% [95% CI: 2.4% to 23.2%] of right SG cells.

CONCLUSIONS

Chronic low-level VNS increases IVC-IAGPNA and damages bilateral stellate ganglia. Both mechanisms could contribute to the underlying mechanism of VR control during AF.

Electrophysiological effects of nicotinic and electrical stimulation of intrinsic cardiac ganglia in the absence of extrinsic autonomic nerves in the rabbit heart

Background

The intrinsic cardiac nervous system is a rich network of cardiac nerves that converge to form distinct ganglia and extend across the heart and is capable of influencing cardiac function.

Objective

The goals of this study were to provide a complete picture of the neurotransmitter/neuromodulator profile of the rabbit intrinsic cardiac nervous system and to determine the influence of spatially divergent ganglia on cardiac electrophysiology.

Methods

Nicotinic or electrical stimulation was applied at discrete sites of the intrinsic cardiac nerve plexus in the Langendorff-perfused rabbit heart. Functional effects on sinus rate and atrioventricular conduction were measured. Immunohistochemistry for choline acetyltransferase (ChAT), tyrosine hydroxylase, and/or neuronal nitric oxide synthase (nNOS) was performed using whole mount preparations.

Results

Stimulation within all ganglia produced either bradycardia, tachycardia, or a biphasic brady-tachycardia. Electrical stimulation of the right atrial and right neuronal cluster regions produced the largest chronotropic responses. Significant prolongation of atrioventricular conduction was predominant at the pulmonary vein-caudal vein region. Neurons immunoreactive (IR) only for ChAT, tyrosine hydroxylase, or nNOS were consistently located within the limits of the hilum and at the roots of the right cranial and right pulmonary veins. ChAT-IR neurons were most abundant (1946 ± 668 neurons). Neurons IR only for nNOS were distributed within ganglia.

Conclusion

Stimulation of intrinsic ganglia, shown to be of phenotypic complexity but predominantly of cholinergic nature, indicates that clusters of neurons are capable of independent selective effects on cardiac electrophysiology, therefore providing a potential therapeutic target for the prevention and treatment of cardiac disease.

GCH1 attenuates cardiac autonomic nervous remodeling in canines with atrial-tachypacing via tetrahydrobiopterin pathway regulated by microRNA-206

BACKGROUND/AIMS

Cardiac autonomic nerve remodeling (ANR) is an important mechanism of atrial fibrillation (AF). GTP cyclohydrolase I, encoded by GCH1, is the rate-limiting enzyme in de novo synthesis of tetrahydrobiopterin (BH4), an essential cofactor for nitric oxide (NO) synthesis. Previous studies reported that increased BH4 and NO content negatively regulated nerve regeneration. This study investigated the effects of GCH1 on ANR via BH4 pathway, regulated by microRNA-206 (miR-206).

METHODS AND RESULTS

In canines, atrial tachypacing (A-TP), together with miR-206 overexpression, increased PGP9.5 level and inhibited GCH1 expression by quantitative real-time polymerase chain reaction and western blot analysis. GCH1 was validated to be a direct target of miR-206 by luciferase assays. Meanwhile, miR-206 overexpression by lentiviruses infection into right superior pulmonary vein fat pad decreased GCH1 expression to ∼40% and further reduced BH4 and NO content compared with the control canines. After infection of GCH1 overexpression lentiviruses for two weeks, atrial effective refractory period was increased compared with the control group (105.8 ± 1.537 ms vs 99.17 ± 2.007 ms, P < 0.05). Moreover, GCH1 overexpression attenuated canines' atrial PGP9.5 level to ∼56% of the controls. In myocardial cells, transfection of GCH1 overexpression lentiviruses also decreased PGP9.5 expression to 26% of the control group. In patients, plasma was collected and miR-206 expression was upregulated in AF patients (n = 18) than the controls (n = 12).

CONCLUSIONS

Our findings suggested that GCH1 downregulation exacerbated ANR by decreasing atrial BH4 and NO content modulated by miR-206 in A-TP canines. This indicates that GCH1 may prevent the initiation of AF through inhibiting ANR.

GAREM1 regulates the PR interval on electrocardiograms

PR interval is the period from the onset of P wave to the start of the QRS complex on electrocardiograms. A recent genomewide association study (GWAS) suggested that GAREM1 was linked to the PR interval on electrocardiograms. This study was designed to validate this correlation using additional subjects and examined the function of Garem1 in a mouse model. We analyzed the association of rs17744182, a variant in the GAREM1 locus, with the PR interval in 5646 subjects who were recruited from 2 Korean replication sets, Yangpyeong (n = 2471) and Yonsei (n = 3175), and noted a significant genomewide association by meta-analysis (P = 2.39 × 10^-8). To confirm the function of Garem1 in mice, Garem1 siRNA was injected into mouse tail veins to reduce the expression of Garem1. Garem1 transcript levels declined by 53% in the atrium of the heart (P = 0.029), and Garem1-siRNA injected mice experienced a significant decrease in PR interval (43.27 ms vs. 44.89 ms in control, P = 0.007). We analyzed the expression pattern of Garem1 in the heart by immunohistology and observed specific expression of Garem1 in intracardiac ganglia. Garem1 was expressed in most neurons of the ganglion, including cholinergic and adrenergic cells. We have provided evidence that GAREM1 is involved in the PR interval of ECGs. These findings increase our understanding of the regulatory signals of heart rhythm through intracardiac ganglia of the autonomic nervous system and can be used to guide the development of a therapeutic target for heart conditions, such as atrial fibrillation.

Increase of Autonomic Nerve Factors in Epicardial Ganglionated Plexi During Rapid Atrial Pacing Induced Acute Atrial Fibrillation

Background

The cardiac autonomic nervous system plays an essential role in epicardial ganglionated plexi (GP) regulation of atrial fibrillation onset and progression. To date, the activity of GP and the function of the cardiac autonomic nervous system are not well understood. The aim of this study was to determine alterations in epicardial GP cholinergic nerve, adrenergic nerve, and nerve growth factor expression using rapid atrial pacing to induce atrial fibrillation in canines.

Material/Methods

Nine healthy adult beagles were divided into two groups: the pacing experimental group (n=6) and the sham-operation control group (n=3). For the pacing group, high frequency pacing of the left atrial appendage was performed for eight hours. In the control group, electrodes were implanted without rapid atrial pacing. Immunocytochemistry was used to identify neurons positively expressing tyrosine hydroxylase, choline acetyl transferase, nerve growth factor and neurturin.

Results

After successfully establishing a rapid atrial pacing of the left atrial appendage induced atrial fibrillation model, we found that expression of choline acetyl transferase, tyrosine hydroxylase, nerve growth factor, and neurturin was significantly higher in the rapid atrial pacing group than the control group (p<0.05).

Conclusions

In our model, incremental excitability of both the adrenergic and cholinergic nerves led to frequent incidents of atrial fibrillation, which were possibly due to an imbalance of autonomic nerve factors in the epicardial GP during acute atrial fibrillation.

Neural substrate of posterior left atrium: A novel modulation for inducibility and remodeling of atrial fibrillation in canine

Background

The neural mechanism of posterior left atrium (PLA) for genesis of atrial fibrillation has not been completely elucidated. We sought to assess the contribution of PLA denervation on atrial fibrillation (AF) inducibility and atrial remodeling.

Methods and results

After left thoracotomy in anesthetized dogs (n = 32), electrode catheters were attached to the PLA, left atrial roof, left pulmonary vein and left atrial appendage. Experiment 1 (n = 16): Vagal stimulation (VS group, n = 8) led to more pronounced ERP shortening in PLA than in other sites (CTL:71±7 ms vs VS: 52±6 ms, P<0.05;). Compared with control group (CTL group, n = 8), atropine alone or with propranolol applied to PLA greatly inhibited VS-induced ERP shortening, ERP dispersion increase, and AF inducibility in the left atrium (P<0.05); but ERP was not significantly different between atropine alone and DB conditions (Atro:85±8 ms vs DB:90±9ms, P>0.05). In addition, domain frequency (DF) of VS-induced AF waveform was not affected by atropine alone, while selective double autonomic blockade at PLA significantly decreased DF at all sites (P<0.05). Experiment 2 (n = 16): In group 1 (n = 8), ERP was markedly shortened in the first 2 hours (11–19% decrease) and then stabilized; however, WOV was progressively widened throughout the 6 hours rapid atrial pacing (BS: 51±9ms vs 6th hour: 161±30ms, P<0.05). After drug application, ERP was increased in all sites of atria, the ERP dispersion was significantly decreased (Atro: 2.36±0.02 vs 6th hour: 5.09±0.07, P<0.05) and AF could be induced in only 1 of 8 dogs. In group 2 (n = 8), 6 hours rapid atrial pacing failed to shorten the ERP and increased ERP dispersion, and only 2 episodes of AF could be induced (WOV = 0).

Conclusion

Local denervation of PLA, as predominant atrial autonomic profile, greatly inhibits AF inducibility and atrial remodeling.

Atrial Ganglionated Plexus Modification: A Novel Approach to Treat Symptomatic Sinus Bradycardia

OBJECTIVES

This study sought to determine if anatomic atrial ganglionated plexus (GP) ablation leads to long-term sinus rate (SR) increase and improves quality of life in patients with symptomatic sinus bradycardia (SB).

BACKGROUND

Atrial GP ablation has been demonstrated to increase SR in our previous study. Atrial GP ablation may also be effective in treating patients with symptomatic SB.

METHODS

Sixty-two patients with symptomatic SB were recruited: Group A included patients <50 years of age (n = 40); Group B included patients ≥50 years of age (n = 22). All patients underwent anatomic ablation of the main atrial GP, and 24-h Holter monitoring and quality-of-life assessment were performed during 1 year of follow-up. Quality of life was accessed by the Medical Outcomes Study Short-Form 36 Health Survey.

RESULTS

Although SR markedly increased in all patients after GP ablation, the increase was significantly greater in patients <50 years of age than in patients ≥50 years of age (19.3 ± 9.9 beats/min vs. 10.8 ± 5.4 beats/min; p = 0.001). The right anterior GP and the GP at the junction of the aorta and superior vena cava made the greatest contributions to SR increase among all GP. The mean and minimal SR increased significantly after ablation and remained elevated for 12 months only in Group A patients. Although symptoms and quality of life improved in all patients, 5 of the 8 domains of the Medical Outcomes Study Short-Form 36 Health Survey did not show obvious improvements in patients of Group B at 12 months.

CONCLUSIONS

Anatomic atrial GP ablation effectively increased SR and improved quality of life in patients <50 years of age with symptomatic SB.

Neuro-atriomyodegenerative origin of atrial fibrillation and superimposed conventional risk factors: continued search to configure the genuine etiology of "eternal arrhythmia"

Atrial fibrillation (AF) is the most challenging rhythm disturbance worldwide. Arrhythmia and its behavior represent complex pathogenesis highly opposing to contemporary curative modalities. Increasing age of patients carries a certain level of risk for AF. Some underlying diseases in concordance with aging actually accelerate the occurrence of AF. Underestimated superimposed risk factors - aging plus any known risk factor or condition (hypertension, diabetes etc.) - elicit great interest and concern. In light of these concerns we offer an elaborated universal hypothesis in attempt to elucidate the genuine origin of AF substrate. Putative chronic toxicity - toxins and/or involution related pseudo-toxins potentially generate micro- and macro-structural changes in atrial myocardium thus inciting both intracellular damage (degeneration of myocites, apoptosis) and extracellular fibrotic proliferation (interstitial fibrosis, formation of matrices, degeneration of cells with fibrotic replacement). The co-products of related underlying diseases in cooperation with cellular senescence, endogenous overproduction of specific lipids/lipoproteins and other pro-atherosclerotic and/or inflammatory components generate a total atrial response - vascular/microvascular damage, intracellular and extracellular injuries. These organizational arrangements covering the entire atrial myocardium and perhaps ganglionated plexi/autonomic branches of the nervous system eventually cause clinical havoc - atrial overstretch, atrial adaptation/maladaptation, electromechanical dysfunction, arrhythmias, heart failure, etc. In essence, valvular heart disease potentially evokes similar changes "violating" thin atrial walls to obey the same scenario. Depicted atriomyodegenerative processes most likely represent the true nature of AF substrate development. Available clinical and morphological evidence potentially designates the atriomyodegenerative or plausible neuro-atriomyodegenerative origin of AF. Deductively fusion of reasons rather than purely heterogeneity is responsible for AF induction. Thus, the uniform approach and synoptic vision of clinical and pathohistological entity may offer an alternative or refreshed viewpoint in AF substrate formation.

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.

Novel Percutaneous Epicardial Autonomic Modulation in the Canine for Atrial Fibrillation: Results of an Efficacy and Safety Study

BACKGROUND

Endocardial ablation of atrial ganglionated plexi (GP) has been described for treatment of atrial fibrillation (AF). Our objective in this study was to develop percutaneous epicardial GP ablation in a canine model using novel energy sources and catheters.

METHODS

Phase 1: The efficacy of several modalities to ablate the GP was tested in an open chest canine model (n = 10). Phase 2: Percutaneous epicardial ablation of GP was done in six dogs using the most efficacious modality identified in phase 1 using two novel catheters.

RESULTS

Phase 1: Direct current (DC) in varying doses (blocking [7-12 μA], electroporation [300-500 μA], ablation [3,000-7,500 μA]), radiofrequency ablation (25-50 W), ultrasound (1.5 MHz), and alcohol (2-5 mL) injection were successful at 0/8, 4/12, 5/7, 3/8, 1/5, and 5/7 GP sites. DC (500-5,000 μA) along with alcohol irrigation was tested in phase 2. Phase 2: Percutaneous epicardial ablation of the right atrium, oblique sinus, vein of Marshall, and transverse sinus GP was successful in 5/6 dogs. One dog died of ventricular fibrillation during DC ablation at 5,000 μA. Programmed stimulation induced AF in six dogs, preablation and no atrial arrhythmia in three, flutter in one, and AF in one postablation. Heart rate, blood pressure, effective atrial refractory period, and local atrial electrogram amplitude did not change significantly postablation. Microscopic examination showed elimination of GP, and minimal injury to atrial myocardium.

CONCLUSION

Percutaneous epicardial ablation of GP using DC and novel catheters is safe and feasible and may be used as an adjunct to pulmonary vein isolation in the treatment of AF in order to minimize additional atrial myocardial ablation.

Atrial Fibrillation Ablation Strategy: "Ready Made" or "Tailored"?

Atrial fibrillation (AF) is the most common arrhythmia leading to hospital admissions. Catheter ablation has evolved as an effective treatment strategy; however, ablation strategies continue to evolve due to the complex and multifactorial nature of atrial fibrillation. A standardized and primarily anatomical approach may not be sufficient to eliminate all mechanisms of atrial fibrillation. A tailored ablation strategy can target specific triggers and drivers of atrial fibrillation; however, it is limited by the accuracy and sensitivity of the methods used in identifying specific mechanisms of atrial fibrillation.

The nervous heart

Many cardiac electrophysiological abnormalities are accompanied by autonomic nervous system dysfunction. Here, we review mechanisms by which the cardiac nervous system controls normal and abnormal excitability and may contribute to atrial and ventricular tachyarrhythmias. Moreover, we explore the potential antiarrhythmic and/or arrhythmogenic effects of modulating the autonomic nervous system by several strategies, including ganglionated plexi ablation, vagal and spinal cord stimulations, and renal sympathetic denervation as therapies for atrial and ventricular arrhythmias.

Treatment of Atrial and Ventricular Arrhythmias Through Autonomic Modulation

This paper reviews the contribution of autonomic nervous system (ANS) modulation in the treatment of arrhythmias. Both the atria and ventricles are innervated by an extensive network of nerve fibers of parasympathetic and sympathetic origin. Both the parasympathetic and sympathetic nervous system exert arrhythmogenic electrophysiological effects on atrial and pulmonary vein myocardium, while in the ventricle the sympathetic nervous system plays a more dominant role in arrhythmogenesis. Identification of ANS activity is possible with nuclear imaging. This technique may provide further insight in mechanisms and treatment targets. Additionally, the myocardial effects of the intrinsic ANS can be identified through stimulation of the ganglionic plexuses. These can be ablated for the treatment of atrial fibrillation. New (non-) invasive treatment options targeting the extrinsic cardiac ANS, such as low-level tragus stimulation and renal denervation, provide interesting future treatment possibilities both for atrial fibrillation and ventricular arrhythmias. However, the first randomized trials have yet to be performed. Future clinical studies on modifying the ANS may not only improve the outcome of ablation therapy but may also advance our understanding of the manner in which the ANS interacts with the myocardium to modify arrhythmogenic triggers and substrate.

Long-Term Effects of Atrial Ganglionated Plexi Ablation on Function and Structure of Sinoatrial and Atrioventricular Node in Canine

BACKGROUND

Long-term effects of ganglionated plexi (GP) ablation on sinoatrial node (SAN) and atrioventricular node (AVN) remain unclear. This study is to investigate the long-term effects of ablation of cardiac anterior right GP (ARGP) and inferior right GP (IRGP) on function and structure of SAN and AVN in canine.

METHODS

Thirty-two dogs were randomly divided into an operated group (n = 24) and sham-operated group (n = 8). ARGP and IRGP were ablated in operated group which was randomly divided into three subgroups according to the period of evaluation after operation (1 month, 6 months, 12 months). The functional and histological characteristics of SAN and AVN, as well as the expression of connexin (Cx) 43 and Cx 45 in SAN and AVN, were evaluated before and after ablation.

RESULTS

Resting heart rate was increased and AVN effective refractory period was prolonged and sinus node recovery time (SNRT) and corrected SNRT were shortened immediately after ablation. These changes were reverted to preablation level after 1 month. At 1 month, ventricular rate during atrial fibrillation was slowed, atria-His intervals were prolonged, and Cx43 and Cx45 expression in SAN and AVN were downregulated. At 6 months, all changes were reverted to preablation level. The histological characteristics of SAN and AVN did not change.

CONCLUSION

Ablation of ARGP and IRGP has short-term effects on function and structure of SAN and AVN rather than long-term effects, which suggests that ablation of ARGP and IRGP is safe. Atrioventricular conduction dysfunction after ablation may be related to downregulated Cx43 and Cx45 expression in AVN.

Is ganglionated plexi ablation during Maze IV procedure beneficial for postoperative long-term stable sinus rhythm?

BACKGROUND

We investigated the role of surgical ablation targeting the autonomous nervous system during a Cox-Maze IV procedure in the maintenance of sinus rhythm at long-term follow-up.

METHODS

The patient population consisted of 519 subjects with persistent or long-standing persistent atrial fibrillation (AF) undergoing radiofrequency Maze IV during open heart surgery between January 2006 and July 2013 at three institutions without (Group 1) or with (Group 2) ganglionated plexi (GP) ablation. Recurrence of atrial fibrillation off-antiarrhythmic drugs was the primary outcome. Predictors of AF recurrence were evaluated by means of competing risk regression. Median follow-up was 36.7 months.

RESULTS

The percentage of patients in normal sinus rhythm (NSR) off-antiarrhythmic drugs did not differ between groups (Group 1-75.5%, Group 2-67.8%, p = 0.08). Duration of AF ≥ 38 months (p = 0.01), left atrial diameter ≥ 54 mm (0.001), left atrial area ≥ 33 cm(2) (p = 0.005), absence of connecting lesions (p= 0.04), and absence of right atrial ablation (p < 0.001) were independently associated with high incidence of AF recurrence. In contrast the absence of GP ablation was not a significant factor (p = 0.12).

CONCLUSIONS

GP ablation did not prove to be beneficial for postoperative stable NSR. A complete left atrial lesion set and biatrial ablation are advisable for improving rhythm outcomes. Randomized controlled trials are necessary to confirm our findings.

Atrial autonomic denervation for the treatment of long-standing symptomatic sinus bradycardia in non-elderly patients

PURPOSE

Multiple lead and generator replacement and related complications often complicate the decision of pacemaker implantation in non-elderly patients with symptomatic bradycardia. This study sought to investigate the efficacy and safety of atrial autonomic denervation for treating the symptomatic long-standing sinus bradycardia (SB) in non-elderly patients.

METHODS AND RESULTS

Eleven non-elderly patients (mean age, 45.9 ± 10.9 years; eight men) with a long history of SB (106.2 ± 43.7 months; range, 60-189) were enrolled. Five atrial ganglionated plexies (GPs), identified by anatomic distribution and high-frequency stimulation, were targeted and ablated. The end point was elimination of the vagal response at ablation sites. The symptoms of SB and Holter were followed up at 3 days, 6, and 12 months and, thereafter, over a period of 18 months. Six patients were under 50 years old (group I) and 5 patients were between 50 and 60 years old (group II). There were 3.1 ± 0.7 GPs with positive vagal response and 11.3 ± 2.7 ablation sites in each patient. During the 18.4 ± 6.2 (range, 12-25) months of follow-up, all patients reported significant symptom improvement with a significant decrease of the SB-related symptoms score. The total heartbeats, mean, and minimum heart rate significantly increased that persisted for 12 months. Compared with patients in group II, those in group I had more increases in total heartbeats and mean heart rate (HR).

CONCLUSION

Atrial autonomic denervation increases sinus rate and improves symptoms in non-elderly patients with symptomatic long-standing SB, thus, potentially serving as an alternative to pacemaker implantation.