Ganglionated Plexi Research Articles

Recording plasticity in neuronal activity in the rodent intrinsic cardiac nervous system using calcium imaging techniques.

The intrinsic cardiac nervous system (ICNS) is composed of interconnected clusters of neurons called ganglionated plexi (GP) which play a major role in controlling heart rate and rhythm. The function of these neurons is particularly important due to their involvement in cardiac arrhythmias such as atrial fibrillation (AF), and previous work has shown that plasticity in GP neural networks could underpin aberrant activity patterns that drive AF. As research in this field increases, developing new techniques to visualize the complex interactions and plasticity in this GP network is essential. In this study we have developed a calcium imaging method enabling the simultaneous recording of plasticity in neuronal activity from multiple neurons in intact atrial GP networks. Calcium imaging was performed with Cal-520 AM labeling in aged spontaneously hypertensive rats (SHRs), which display both spontaneous and induced AF, and age-matched Wistar Kyoto (WKY) controls to determine the relationship between chronic hypertension, arrhythmia and GP calcium dynamics. Our data show that SHR GPs have significantly larger calcium responses to cholinergic stimulation compared to WKY controls, as determined by both higher amplitude and longer duration calcium responses. Responses were significantly but not fully blocked by hexamethonium, indicating multiple cholinergic receptor subtypes are involved in the calcium response. Given that SHRs are susceptible to cardiac arrhythmias, our data provide evidence for a potential link between arrhythmia and plasticity in calcium dynamics that occur not only in cardiomyocytes but also in the GP neurons of the heart.

Sinus node dysfunction and atrial fibrillation-Relationships, clinical phenotypes, new mechanisms, and treatment approaches.

Although the anatomical basis of the pathogenesis of sinus node dysfunction (SND) and atrial fibrillation (AF) is located primarily in the left and right atria, increasing evidence suggests a strong correlation between SND and AF, in terms of both clinical presentation and formation mechanisms. However, the exact mechanisms underlying this association are unclear. The relationship between SND and AF may not be causal, but is likely to involve common factors and mechanisms, including ion channel remodeling, gap junction abnormalities, structural remodeling, genetic mutations, neuromodulation abnormalities, the effects of adenosine on cardiomyocytes, oxidative stress, and viral infections. Ion channel remodeling manifests primarily as alterations in the "funny" current (If) and Ca2+ clock associated with cardiomyocyte autoregulation, and gap junction abnormalities are manifested primarily as decreased expression of connexins (Cxs) mediating electrical impulse propagation in cardiomyocytes. Structural remodeling refers primarily to fibrosis and cardiac amyloidosis (CA). Some genetic mutations can also cause arrhythmias, such as SCN5A, HCN4, EMD, and PITX2. The intrinsic cardiac autonomic nervous system (ICANS), a regulator of the heart's physiological functions, triggers arrhythmias.In addition, we discuss arrhythmias caused by viral infections, notably Coronavirus Disease 2019 (COVID-19). Similarly to upstream treatments for atrial cardiomyopathy such as alleviating CA, ganglionated plexus (GP) ablation acts on the common mechanisms between SND and AF, thus achieving a dual therapeutic effect.

Epicardial adipocytes in the pathogenesis of atrial fibrillation: An update on basic and translational studies.

Epicardial adipose tissue (EAT) is an endocrine organ containing a host of cell types and undoubtedly serving a multitude of important physiologic functions. Aging and obesity cause hypertrophy of EAT. There is great interest in the possible connection between EAT and cardiovascular disease, in particular, atrial fibrillation (AF). Increased EAT is independently associated with AF and adverse events after AF ablation (e.g., recurrence of AF, and stroke). In general, the amount of EAT correlates with BMI or visceral adiposity. Yet on a molecular level, there are similarities and differences between epicardial and abdominal visceral adipocytes. In comparison to subcutaneous adipose tissue, both depots are enriched in inflammatory cells and chemokines, even in normal conditions. On the other hand, in comparison to visceral fat, epicardial adipocytes have an increased rate of fatty acid release, decreased size, and increased vascularity. Several studies have described an association between fibrosis of EAT and fibrosis of the underlying atrial myocardium. Others have discovered paracrine factors released from EAT that could possibly mediate this association. In addition to the adjacent atrial cardiomyocytes, EAT contains a robust stromal-vascular fraction and surrounds the ganglionic plexi of the cardiac autonomic nervous system (cANS). The importance of the cANS in the pathogenesis of atrial fibrillation is well known, and it is quite likely that there is feedback between EAT and the cANS. This complex interplay may be crucial to the maintenance of normal sinus rhythm or the development of atrial fibrillation. The extent the adipocyte is a microcosm of metabolic health in the individual patient may determine which is the predominant rhythm.

Pathogenesis, clinical manifestations, diagnosis, and treatment progress of achalasia of cardia.

Achalasia cardia, type of esophageal dynamic disorder, is a relatively rare primary motor esophageal disease characterized by the functional loss of plexus ganglion cells in the distal esophagus and lower esophageal sphincter. Loss of function of the distal and lower esophageal sphincter ganglion cells is the main cause of achalasia cardia, and is more likely to occur in the elderly. Histological changes in the esophageal mucosa are considered pathogenic; however, studies have found that inflammation and genetic changes at the molecular level may also cause achalasia cardia, resulting in dysphagia, reflux, aspiration, retrosternal pain, and weight loss. Currently, the treatment options for achalasia focus on reducing the resting pressure of the lower esophageal sphincter, helping to empty the esophagus and relieve symptoms. Treatment measures include botulinum toxin injection, inflatable dilation, stent insertion, and surgical myotomy (open or laparoscopic). Surgical procedures are often subject to controversy owing to concerns about safety and effectiveness, particularly in older patients. Herein, we review clinical epidemiological and experimental data to determine the prevalence, pathogenesis, clinical presentation, diagnostic criteria, and treatment options for achalasia to support its clinical management.

Nicotinamide Riboside Improves Enteric Neuropathy in Streptozocin-Induced Diabetic Rats Through Myenteric Plexus Neuroprotection.

Diabetes Mellitus causes a systemic oxidative stress due in part to the hyperglycemia and the reactive oxygen species generated. Up to 75% of diabetic patients present with an autonomic neuropathy affecting the Enteric Nervous System. Deficits in the human population are chronic dysmotilities with either increased (i.e., constipation) or decreased (i.e., diarrhea) total gastrointestinal transit times. These are recapitulated in the streptozocin-induced diabetic rat, which is a model of Type I Diabetes Mellitus. Examine the effects that a precursor of nicotinamide adenosine dinucleotide (NAD), nicotinamide riboside (NR), had on the development of dysmotility in induced diabetic rats and if fecal microbiota transplant (FMT) could produce the same results. Utilizing a 6-week treatment paradigm, NR was administered intraperitoneally every 48h. Total gastrointestinal transit time was assessed weekly utilizing the carmine red method. Three weeks following hyperglycemic induction, FMT was performed between NR-treated animals and untreated animals. There is improvement in overall gastrointestinal transit time with the use of NR. 16S microbiome sequencing demonstrated decreased alpha and beta diversity in induced diabetic rats without change in animals receiving FMT. Improvements in myenteric plexus ganglia density in small and large intestines in diabetic animals treated with NR were seen. NR treatment led to functional improvement in total gastrointestinal transit time in induced diabetic animals. This was associated with neuroprotection in the myenteric plexuses of both small and large intestines of induced diabetic rats. This represents an important first step in showing NR's benefit as a treatment for diabetic enteric neuropathy. Streptozocin-induced diabetic rats have improved transit times and increased myenteric plexus ganglia density when treated with intraperitoneal nicotinamide riboside.

Ganglionic Plexus Ablation: A Step-by-step Guide for Electrophysiologists and Review of Modalities for Neuromodulation for the Management of Atrial Fibrillation.

As the most common sustained arrhythmia, AF is a complex clinical entity which remains a difficult condition to durably treat in the majority of patients. Over the past few decades, the management of AF has focused mainly on pulmonary vein triggers for its initiation and perpetuation. It is well known that the autonomic nervous system (ANS) has a significant role in the milieu predisposing to the triggers, perpetuators and substrate for AF. Neuromodulation of ANS - ganglionated plexus ablation, vein of Marshall ethanol infusion, transcutaneous tragal stimulation, renal nerve denervation, stellate ganglion block and baroreceptor stimulation - constitute an emerging therapeutic approach for AF. The purpose of this review is to summarise and critically appraise the currently available evidence for neuromodulation modalities in AF.

Immunohistochemical study of the sympathetic innervation of the colon in chronic slow-transit constipation

The purpose of this study is to determine the distribution and features of sympathetic innervation of the tissues of the human colon wall in chronic slow-transit constipation using immunohistochemical methods. Materials and methods. Immunohistochemical study of large intestine segments (colon and sigmoid colon) obtained as a result of surgical treatment of patients with chronic slow-transit constipation was carried out using neural markers (PGP 9.5 protein, tyrosine hydroxylase, synaptophysin). Results. It has been shown that the majority of postganglionic sympathetic nerve fibers are localized in the Auerbach and Meissner plexuses. Their terminal axons form pericellular synaptic apparatuses around cholinergic neurons. Another part of the sympathetic fibers is involved in the innervation of the muscular plate of the mucous membrane and the walls of the venous vessels of the submucosa; their terminal varicose axons can be seen on smooth muscle cells as distant synapses en passant. Significant features of sympathetic innervation disorders of the large intestine of the studied patients were established; morphological evidence for the reactive, dystrophic and degenerative changes in the sympathetic apparatuses in the ganglionic plexuses were found. The regularities of the absence of sympathetic innervation in two muscle layers (longitudinal and circular), as well as in the mucous membrane, were revealed. Sympathetic neurons were not found in the studied sections of the large intestine. Conclusion. It is assumed that the identified pathological changes in sympathetic innervation in chronic slow-transit constipation can serve as one of the main causes of disruption of normal bowel functions.

Cardioneuroablation for carotid sinus syndrome: a case series

Cardioinhibitory carotid sinus syndrome (CSS) is a neurally-mediated (reflex) syncope, secondary to excessive vagal response to carotid sinus pressure. A growing body of studies have shown that catheter ablation of ganglionated plexi (GPs) or cardioneuroablation (CNA) is effective in treating patients with vaso-vagal syncope (1). To date, no studies systematically evaluated CNA in patients with CSS.

A Histomorphometric Analysis of Interganglionic Distance in the Myenteric Plexus of the Entire Large Intestine of Aborted Human Foetuses: A Cross-sectional Study

Introduction: The Enteric Nervous System (ENS) contributes to the innervation of the gut and is considered the second brain in the gut. It is a part of the peripheral nervous system and the ganglionated plexus (GP) of enteric neurons, present in the layers of the digestive tract, is more complex than any other structure of the peripheral nervous system. The establishment of a valid standard method for quantitative analysis of the myenteric plexus has been a topic of debate among enteric neuropathologists and is essential for better characterisation of patients with gut dysmotility. Aim: To determine the histomorphometric analysis of the interganglion distance of the myenteric plexus in the entire large intestine of aborted human foetuses. Materials and Methods: A cross-sectional descriptive study was carried out in the Department of Anatomy at Pondicherry Institute of Medical Sciences, Pondicherry, India. The study duration was eight years and seven months, from October 2014 to May 2022. A total of 50 aborted human foetus samples were collected from Rajiv Gandhi Government Women and Children’s Hospital, Puducherry, India, from the Department of Obstetrics and Gynaecology. The age of the aborted human foetuses was determined based on Biparietal Diameter (BPD) and Crown Rump Length (CRL) and correlated with clinical history. The aborted human foetuses were assigned to two groups: group A (n=29), ≤20 Weeks of Gestation (WG), and group B (n=21), ≥20 WG. Nicotinamide Adenine Dinucleotide Phosphate (NADPH) diaphorase histochemistry, an enzyme histochemistry technique, was used to study the tissue preparations. Statistical significance was determined using Statistical Package for Social Sciences (SPSS) version 20.0, International Business Machines (IBM) corporation. The independent sample t-test was conducted for parametric analysis. Results: The interganglion distance was measured from the caecum (A1 segment) to the anal canal (A7 segment) in aborted foetuses of less than 20 WG. The mean values ranged from 78.86±38.09 μm to 126.94±23.87 μm in foetuses of less than 20 WG. The mean values ranged from 66.41±8.05 μm to 107.67±30.17 μm in aborted human foetuses of more than 20 WG. Conclusion: The anal canal showed a long interganglion distance. The average reference values were found to be helpful as a diagnostic tool for identifying disorders related to gut innervation and motility.

Development of neuromodulation for atrial fibrillation: a narrative review.

Atrial fibrillation (AF) is a prevalent clinical arrhythmia with a high incidence of disability and mortality. Autonomic nervous system (ANS) plays a crucial role in the onset and persistence of AF, and can lead to electrophysiological changes and alterations in atrial structure. Both animal models and clinical findings suggest that parasympathetic and sympathetic activity within the cardiac ANS could induce atrial remodeling and AF. Remodeling of the cardiac autonomic nerves is a significant structural basis for promoting AF. Given the challenges faced by conventional pharmacological and atrial ablation techniques in the treatment of AF, increasing attention has been paid to autonomic intervention strategies for AF. Current research has demonstrated that the frequency and severity of AF episodes can be significantly reduced by modulating the activity of ANS. ANS neuromodulation is expected to lead more effective and personalized treatment options for patients with AF. The objective of this review is to provide a broader perspective for future related studies by reviewing preclinical and clinical studies of neuromodulation methods for the treatment of AF, searching for relevant approaches to treat AF, as well as identifying the strengths and weaknesses demonstrated by current relevant studies, and providing researchers with a broader overview of the latest neurological treatments for AF. A narrative review was conducted on the literature on PubMed, WanFang data, and Google Scholar, including all relevant studies published until November 2023. In this review, we delve into the innervation of cardiac autonomic nerves, the role of the ANS in the development and maintenance of AF, and the current neuromodulation methods for AF treatment. These methods include stellate ganglion (SG) resection or ablation, vagus nerve stimulation (VNS), thoracic subcutaneous nerve stimulation (ScNS), renal denervation (RDN) therapy, ganglionated plexus (GP) ablation, and epicardial botulinum toxin or CaCl2 injection. More and more research suggests that neuromodulation methods for the treatment of AF have broad prospects. ANS plays a crucial role in AF development and maintenance through cardiac autonomic nerve remodeling. Modulating ANS activity can significantly reduce AF frequency and severity, offering more personalized treatment options. Current research on autonomic interventions for AF shows promise for more effective and personalized treatments.

Selective Modulation of the Cardiac Autonomic Nervous System: A New Therapeutic Strategy for Cardioinhibitory Vasovagal Syncope

Vasovagal syncope (VVS) is the most common type of syncope. The overall prognosis of VVS is usually benign, although the quality of life can be affected when syncope is recurrent and refractory to conventional therapy. Multiple treatment options exist for patients with recurrent VVS, although the effect is modest. In this focused review, we briefly discussed the plausible pathophysiological mechanisms of VVS. We used three case examples to update the current state of cardioneuroablation (CNA) in patients with recurrent cardioinhibitory response as a potential therapeutic option. This article includes review of studies and reports on CNA summarizing the principles of this therapeutic approach; various ways of mapping to localize the parasympathetic ganglionic plexi for ablation; description of technique of extra-cardiac vagal stimulation to confirm parasympathetic denervation of the heart as well as the end points and outcomes of the reported studies. Moreover, we reviewed the pros, cons, gaps, and future directions of this potential therapeutic option in treating patients with VVS.

A new systematization of histological analysis for the diagnosis of Hirschsprung's disease

BackgroundHirschsprung's Disease (HD) is characterized by intestinal sub-occlusion and the absence of enteric ganglion cells. A rectal biopsy examination is performed to confirm the diagnosis. In a recent study, we demonstrated that the analysis of 60 sections of rectal mucosa and submucosa stained by H&E may ensure a 90% diagnostic accuracy. Although the need to analyze so many sections makes the process of reading the slides more time-consuming, this encouraged us to study their distribution in the healthy rectal submucosa, to simplify the diagnosis. ObjectivesTo develop a method that facilitates HD diagnosis by studying the distribution of ganglion cells in the submucosal plexus. MethodsUsing the calretinin technique, we studied the distribution of plexuses in 60 fragments of rectal submucosa from 19 cadavers. After the study, the reading method created was used for diagnosis in 47 cases of suspected HD, using H&E staining. The accuracy was verified by comparing the results obtained with H&E to those obtained with the acetylcholinesterase technique, the golden standard in our laboratory. ResultsThe study of submucosal plexus distribution showed that just by examining the submucosal region every 20 µm, approximately, it is possible to locate a ganglionic plexus, and we have already been able to diagnose HD with 93% accuracy. ConclusionThe study of ganglion cell distribution enabled the creation of a simplified method for reading the slides. The method applied achieved good accuracy and it can be used as an alternative method in HD diagnosis.

764 CARDIONEUROABLATION OF VAGALLY MEDIATED BRADYARRHYTHMIA: A SINGLE-CENTER EXPERIENCE

Abstract Background Cardioneuroablation (CNA) is a novel catheter-ablation technique for the treatment of vagally-mediated bradyarrhythmia including vaso-vagal syncope (VVS), functional atrioventricular block (AVB) and sinus node dysfunction (SND). CNA aims to blunt the cardioinhibitory reflex by eliminating postganglionic parasympathetic neurons in the atrial wall and ganglionated plexi (GPs). Early-phase studies have shown promising results, but clinical evidence remains limited. Purpose We present our single-center experience with CNA in the setting of VVS, symptomatic functional AVB, and SND. Methods Baseline and procedural characteristics, procedure-related complications, and clinical outcomes were collected in patients who underwent CNA from December 2018 to July 2022. The procedural workflow included an electroanatomic mapping-guided ablation strategy, which combines the bi-atrial 3D mapping with endocardial atrial bipolar electrograms (EGM), specifically targeting high-amplitude fractionated EGM. Results A total of 14 CNA procedures were performed in our center. Ablation indication was mainly VVS (57%), followed by AVB (29%) and SND (14%). Syncope was the most common symptom in our cohort (71%, burden of 7 per person-lifetime). Patients were young (43±16 years) and without structural heart disease (LVEF 58±4 ml, LAD 31±7 mm). Procedures were performed under general anesthesia, mean procedure time was 102±42 min, with minimal fluoroscopy dose (2.7±1.8 Gy/cm2). We observed 1 instance of post-ablation pericarditis and 2 sinus tachycardia which required medical treatment; no major adverse events occurred. Heart rate increased after ablation in all the patients, with a mean RR interval shortening of 28% and no further increase after atropine administration. Two patients had a recurrence at a median follow-up of 251 days (IQR: 118-536), both cases were syncopal events without documentation at loop-recorder of sinus bradycardia or atrial bradyarrhythmia. Conclusions CNA may be an alternative to pacemaker implantation in young, highly symptomatic patients, refractory to conventional therapies and without structural heart disease. Ablation is reasonably safe in experts’ hands, especially if compared with the long-life risk of device-related complications. Further large-scale randomized studies are needed to support these findings.

In Silico Modelling to Assess the Electrical and Thermal Disturbance Provoked by a Metal Intracoronary Stent during Epicardial Pulsed Electric Field Ablation.

Background: Pulsed Electric Field (PEF) ablation has been recently proposed to ablate cardiac ganglionic plexi (GP) aimed to treat atrial fibrillation. The effect of metal intracoronary stents in the vicinity of the ablation electrode has not been yet assessed. Methods: A 2D numerical model was developed accounting for the different tissues involved in PEF ablation with an irrigated ablation device. A coronary artery (with and without a metal intracoronary stent) was considered near the ablation source (0.25 and 1 mm separation). The 1000 V/cm threshold was used to estimate the ‘PEF-zone’. Results: The presence of the coronary artery (with or without stent) distorts the E-field distribution, creating hot spots (higher E-field values) in the front and rear of the artery, and cold spots (lower E-field values) on the sides of the artery. The value of the E-field inside the coronary artery is very low (~200 V/cm), and almost zero with a metal stent. Despite this distortion, the PEF-zone contour is almost identical with and without artery/stent, remaining almost completely confined within the fat layer in any case. The mentioned hot spots of E-field translate into a moderate temperature increase (<48 °C) in the area between the artery and electrode. These thermal side effects are similar for pulse intervals of 10 and 100 μs. Conclusions: The presence of a metal intracoronary stent near the ablation device during PEF ablation simply ‘amplifies’ the E-field distortion already caused by the presence of the vessel. This distortion may involve moderate heating (<48 °C) in the tissue between the artery and ablation electrode without associated thermal damage.

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

BackgroundDuring 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). ObjectivesThis study sought to assess the impact of pulsed field ablation (PFA) on the GP in patients undergoing PVI. MethodsIn 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. ResultsBetween 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. ConclusionsPFA has minimal effect on GP. Unlike with thermal ablation, the mechanism by which PFA treats atrial fibrillation is mediated solely by durable PVI.

RNA-sequencing reveals molecular and regional differences in the esophageal mucosa of achalasia patients

Achalasia is an esophageal motility disorder characterized by the functional loss of myenteric plexus ganglion cells in the distal esophagus and lower esophageal sphincter. Histological changes have been reported in the esophageal mucosa of achalasia, suggesting its involvement in disease pathogenesis. Despite recent advances in diagnosis, our understanding of achalasia pathogenesis at the molecular level is very limited and gene expression profiling has not been performed. We performed bulk RNA-sequencing on esophageal mucosa from 14 achalasia and 8 healthy subjects. 65 differentially expressed genes (DEGs) were found in the distal esophageal mucosa of achalasia subjects and 120 DEGs were identified in proximal esophagus. Gene expression analysis identified genes common or exclusive to proximal and distal esophagus, highlighting regional differences in the disease. Enrichment of signaling pathways related to cytokine response and viral defense were observed. Increased infiltration of CD45+ intraepithelial leukocytes were seen in the mucosa of 38 achalasia patients compared to 12 controls. Novel insights into the molecular changes occurring in achalasia were generated in this transcriptomic study. Some gene changes observed in the mucosa of achalasia may be associated with esophagitis. Differences in DEGs between distal and proximal esophagus highlight the importance of better understanding regional differences in achalasia.

Pulsed Electric Field Ablation of Epicardial Autonomic Ganglia: Computer Analysis of Monopolar Electric Field across the Tissues Involved.

Pulsed Electric Field (PEF) ablation has been proposed as a non-thermal energy to treat atrial fibrillation (AF) by epicardial ablation of ganglionated plexi (GP), which are embedded within epicardial fat. Our objective was to study the distribution of the electric field through the involved tissues (fat, GPs, myocardium and blood) during epicardial PEF ablation. A two-dimensional model was built considering different tissue layers below the ablation device which consists of an irrigated electrode. The 1000 V/cm threshold was used to estimate the 'PEF-zone'. The PEF-zone was almost 100% circumscribed in the epicardial fat layer, with very little incidence in the myocardium. The presence of the saline on the epicardial fat causes the PEF-zone to spread laterally around the electrode from ~5 mm to ~15 mm, relatively independently of how embedded the electrode is in the saline layer. For a saline layer well spread over the tissue surface and an electrode fully embedded in the saline layer, the PEF-zone width decreases as the fat layer thickens: from ~15 mm for fat thickness of 1 and 2 mm, down to ~10 mm for fat thickness of 5 mm. The presence of a GP in the center of the fat layer hardly affects the size of the PEF-zone, but significantly alters the distribution of the electric field around the GP, resulting in progressively lower values than in the surrounding adipose tissue as the fat layer thickness increased. Our results suggest how some procedural (irrigation) and anatomical parameters (fat thicknesses and presence of GPs) could be relevant in terms of the size of the tissue area affected by pulsed field ablation.

Topographical organization and morphology of substance P (SP)-immunoreactive axons in the whole stomach of mice.

Nociceptive afferents innervate the stomach and send signals centrally to the brain and locally to stomach tissues. Nociceptive afferents can be detected with a variety of different markers. In particular, substance P (SP) is a neuropeptide and is one of the most commonly used markers for nociceptive nerves in the somatic and visceral organs. However, the topographical distribution and morphological structure of SP-immunoreactive (SP-IR) axons and terminals in the whole stomach have not yet been fully determined. In this study, we labeled SP-IR axons and terminals in flat mounts of the ventral and dorsal halves of the stomach of mice. Flat-mount stomachs, including the longitudinal and circular muscular layers and the myenteric ganglionic plexus, were processed with SP primary antibody followed by fluorescent secondary antibody and then scanned using confocal microscopy. We found that (1) SP-IR axons and terminals formed an extensive network of fibers in the muscular layers and within the ganglia of the myenteric plexus of the whole stomach. (2) Many axons that ran in parallel with the long axes of the longitudinal and circular muscles were also immunoreactive for the vesicular acetylcholine transporter (VAChT). (3) SP-IR axons formed very dense terminal varicosities encircling individual neurons in the myenteric plexus; many of these were VAChT immunoreactive. (4) The regional density of SP-IR axons and terminals in the muscle and myenteric plexus varied in the following order from high to low: antrum-pylorus, corpus, fundus, and cardia. (5) In only the longitudinal and circular muscles, the regional density of SP-IR axon innervation from high to low were: antrum-pylorus, corpus, cardia, and fundus. (6) The innervation patterns of SP-IR axons and terminals in the ventral and dorsal stomach were comparable. Collectively, our data provide for the first time a map of the distribution and morphology of SP-IR axons and terminals in the whole stomach with single-cell/axon/synapse resolution. This work will establish an anatomical foundation for functional mapping of the SP-IR axon innervation of the stomach and its pathological remodeling in gastrointestinal diseases.

Abstract 10683: Alternations in Autonomic Function During Pulmonary Vein Isolation Without Targeting Ganglionated Plexi Ablation in Patients With Atrial Fibrillation

Introduction: Abnormal autonomic innervation in the left atrium was reported to be related to developing/sustaining atrial fibrillation (AF). Autonomic denervation by radiofrequency catheter ablation (RFCA), evaluated by heart rate variability (HRV), is associated with a lower recurrence rate of AF. Ganglionated Plexi (GP) has been regarded as a target of autonomic denervation during the RFCA; however, the degree by which autonomic function is altered during the RFCA procedure remains unclear. Hypothesis:We tested the hypothesis that autonomic function is altered consistently during the ablation procedure without targeting GP. Method: Thirteen patients with paroxysmal AF who underwent pulmonary vein isolation (PVI) via RFCA were included (Age, 64.3 ± 1.9; Male/Female, 10/3). PVI was performed in the order prescribed (left superior, left inferior, right superior, and right inferior PV). HRV was assessed prior to, during each PV ablation, and post-ablation. Results: A vagal response (significant bradycardia) during the procedure was observed in three patients. The parameter of para-sympathetic nerve activity (para-SNA) (e.g., RMSSD, 38.7 ± 7.8 vs. 26.6 ± 6.0 ms, P &lt; 0.05), and total power of HRV (1861 ± 831 vs. 1105 ± 584 ms, P &lt; 0.05) were decreased by the procedure. While the balance of SNA to para-SNA (ratio of low to high frequency, LF/HF) was unchanged, which may indicate both SNA and para-SNA denervation. Using a linear mixed effect model, the effect of the “period” (i.e., pre, each PV, post) on the reduction in para-SNA parameter (HF) or total power of HRV was significant (both, P &lt; 0.05). The reduction was consistent in each PV, and post-hoc analysis (Bonferroni) showed significant differences only between baseline and post-RFCA in these parameters (P &lt; 0.05). Even in the patients without significant bradycardia response, the reduction in HRV parameter was significant in the linear mixed effect model (e.g., the effect of the “period” on RMSSD, P &lt; 0.05). Conclusion: We found that the PVI by RFA, without targeting GP, modified autonomic function, even in the patients who did not develop vagal responses. The HRV change was consistent during each PV isolation, which may suggest the non-necessity of GP ablation for autonomic modification by the ablation.

Abstract 14305: Long-Term Results of Left Atrial Ganglionated Plexi Ablation in Patients With Syncope and POTS

Background: Cardioneuroablation (CNA) of atrial ganglionated plexi (GP) using radiofrequency anergy has shown to be effective in treating refractory neurocardiogenic syncope (NS) during a short-term follow-up. However, there is no study of CNA in patients with postural orthostatic tachycardia syndrome (POTS) with syncope. Methods: Eight patients (mean age 39+9 years, male: 62%) with treatment-refractory (NS: 4, POTS: 4) syncope underwent CNA of all 4 GPs of the left atrium and followed for 35 + 10 months. Results: All patients were non-responders to lifestyle modification and multiple drug therapies including (fludrocortisone, midodrine, beta-blockers, clonidine and pyridostigmine). Syncope recurred only in 3 (37.5%) patients after a mean duration of 34.9 + 15 months. Syncope recurred in 2 of 4 (50%) patients with NS and in 1 of 4 (25%) patients with POTS. Conclusions: Contrary to prior publications, syncope recurs in 37.5% patients during long-term follow up after CAN in both POTS and NS patients.