An Acute Model for Atrial Fibrillation Arising from a Peripheral Atrial Site: Evidence for Primary and Secondary Triggers

Determinants of new wavefront locations in cholinergic atrial fibrillation

AIMS

Atrial fibrillation (AF) wavefront dynamics are complex and difficult to interpret, contributing to uncertainty about the mechanisms that maintain AF. We aimed to investigate the interplay between rotors, wavelets, and focal sources during fibrillation.

METHODS AND RESULTS

Arrhythmia wavefront dynamics were analysed for four optically mapped canine cholinergic AF preparations. A bilayer computer model was tuned to experimental preparations, and varied to have (i) fibrosis in both layers or the epicardium only, (ii) different spatial acetylcholine distributions, (iii) different intrinsic action potential duration between layers, and (iv) varied interlayer connectivity. Phase singularities (PSs) were identified and tracked over time to identify rotational drivers. New focal wavefronts were identified using phase contours. Phase singularity density and new wavefront locations were calculated during AF. There was a single dominant mechanism for sustaining AF in each of the preparations, either a rotational driver or repetitive new focal wavefronts. High-density PS sites existed preferentially around the pulmonary vein junctions. Three of the four preparations exhibited stable preferential sites of new wavefronts. Computational simulations predict that only a small number of connections are functionally important in sustaining AF, with new wavefront locations determined by the interplay between fibrosis distribution, acetylcholine concentration, and heterogeneity in repolarization within layers.

CONCLUSION

We were able to identify preferential sites of new wavefront initiation and rotational activity, in order to determine the mechanisms sustaining AF. Electrical measurements should be interpreted differently according to whether they are endocardial or epicardial recordings.

Acetylcholine-Atropine Interactions: Paradoxical Effects on Atrial Fibrillation Inducibility

Atropine (ATr) is well known as a cholinergic antagonist, however, at low concentrations ATr could paradoxically accentuate the parasympathetic actions of acetylcholine (ACh). In 22 pentobarbital anesthetized dogs, via a left and right thoracotomy, a leak-proof barrier was attached to isolate the atrial appendages (AAs) from the rest of the atria. In group 1 (Ach+ATr+Ach), ACh, 100 mM, was placed on the AA followed by the application of ATr, 2 mg/mL. The average atrial fibrillation (AF) duration was 17 ± 7 minutes. After ATr was applied to the AA and ACh again tested, the AF duration was markedly attenuated (2 ± 2 minutes, P < 0.05). In group 2 (ATr+Ach), ATr was initially applied to the AA followed by the application of ACh, 100 mM. There was no significant difference in AF duration (16 ± 4 minutes vs. 18 ± 2 minutes, P = NS). The inhibitory effect of ATr on induced HR reduction (electrical stimulation of the anterior right ganglionated plexi and vagal nerves) was similar between groups 1 and 2. These observations suggest that when ATr is initially administered it attaches to the allosteric site of the muscarinic ACh receptor (M2) leaving the orthosteric site free to be occupied by ACh. The M3 receptor that controls HR slowing does not show the same allosteric properties.

Long-Term Suppression of Atrial Fibrillation by Botulinum Toxin Injection Into Epicardial Fat Pads in Patients Undergoing Cardiac Surgery: One-Year Follow-Up of a Randomized Pilot Study

BACKGROUND

Animal models suggest that the neurotransmitter inhibitor, botulinum toxin, when injected into the epicardial fat pads can suppress atrial fibrillation inducibility. The aim of this prospective randomized double-blind study was to compare the efficacy and safety of botulinum toxin injection into epicardial fat pads for preventing atrial tachyarrhythmias.

METHODS AND RESULTS

Patients with history of paroxysmal atrial fibrillation and indication for coronary artery bypass graft surgery were randomized to botulinum toxin (Xeomin, Merz, Germany; 50 U/1 mL at each fat pad; n=30) or placebo (0.9% normal saline, 1 mL at each fat pad; n=30) injection into epicardial fat pads during surgery. Patients were followed for 1 year to assess maintenance of sinus rhythm using an implantable loop recorder. All patients in both groups had successful epicardial fat pad injections without complications. The incidence of early postoperative atrial fibrillation within 30 days after coronary artery bypass graft was 2 of 30 patients (7%) in the botulinum toxin group and 9 of 30 patients (30%) in the placebo group (P=0.024). Between 30 days and up to the 12-month follow-up examination, 7 of the 30 patients in the placebo group (27%) and none of the 30 patients in the botulinum toxin group (0%) had recurrent atrial fibrillation (P=0.002). There were no complications observed during the 1-year follow-up.

CONCLUSIONS

Botulinum toxin injection into epicardial fat pads during coronary artery bypass graft provided substantial atrial tachyarrhythmia suppression both early as well as during 1-year follow-up, without any serious adverse events.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01842529.

Spinal cord stimulation suppresses focal rapid firing-induced atrial fibrillation by inhibiting atrial ganglionated plexus activity

OBJECTIVE

This study was designed to demonstrate that spinal cord stimulation (SCS) could suppress high-frequency stimulation (HFS)-induced focal atrial fibrillation (AF) at atrial and pulmonary vein (PV) sites by inhibiting atrial ganglionated plexus (GP) activity.

METHODS

Multielectrode catheters were attached to atria and all PV sites. SCS was performed at the T1-T5 spinal region for 1 hour. At the baseline state and the end of 1 hour of SCS, 40 milliseconds of HFS was delivered 2 milliseconds after atrial pacing to determine the AF threshold at each site. One electrode was attached to the superior left GP so that HFS to this site induced sinus rate slowing. Microelectrodes inserted into the anterior right GP recorded neural firing.

RESULTS

SCS induced a significant increase in AF threshold at all sites (all P < 0.05). The sinus rate slowing response induced by superior left GP stimulation was blunted by SCS (17% ± 3.6% vs. 39% ± 3.8%, P < 0.05). The frequency (32 ± 4 vs. 87 ± 6 impulses per minute, P < 0.05) and amplitude (0.16 ± 0.02 vs. 0.42 ± 0.04 mv, P < 0.05) of the neural activity recorded from the anterior right GP were markedly inhibited by SCS.

CONCLUSIONS

SCS may prevent episodic AF caused by rapid PV and non-PV firing through modulating GP activity.

Recurrent intradialytic paroxysmal atrial fibrillation: hypotheses on onset mechanisms based on clinical data and computational analysis

Atrial fibrillation (AF) incidence is high in end-stage renal disease (ESRD) patients, and haemodialysis (HD) session may induce paroxysmal AF episodes. Structural atrium remodelling is common in ESRD patients, moreover, HD session induces rapid plasma electrolytes and blood volume changes, possibly favouring arrhythmia onset. Therefore, HD session represents a unique model to study in vivo the mechanisms potentially inducing paroxysmal AF episodes. Here, we present the case report of a patient in which HD regularly induced paroxysmal AF. In four consecutive sessions, heart rate variability analysis showed a progressive reduction of low/high frequency ratio before the AF onset, suggesting a relative increase in vagal activity. Moreover, all AF episodes were preceded by a great increase of supraventricular ectopic beats. We applied computational modelling of cardiac cellular electrophysiology to these clinical findings, using plasma electrolyte concentrations and heart rate to simulate patient conditions at the beginning of HD session (pre-HD) and right before the AF onset (pre-AF), in a human atrial action potential model. Simulation results provided evidence of a slower depolarization and a shortened refractory period in pre-AF vs. pre-HD, and these effects were enhanced when adding acetylcholine effect. Paroxysmal AF episodes are induced by the presence of a trigger that acts upon a favourable substrate on the background of autonomic nervous system changes and in the described case report all these three elements were present. Starting from these findings, here we review the possible mechanisms leading to intradialytic AF onset.

The Propensity for Inducing Atrial Fibrillation: A Comparative Study on Old versus Young Rabbits

It is well established that atrial fibrillation (AF) is far more common in elderly humans. Autonomic activation is thought to be an operative mechanism for AF propensity. The aim of the study was to investigate the impact of age on atrial tachyarrhythmia induction in a rabbit model. Six old (aged 4-6 years) and 9 young (aged 3-4 months) New Zealand white rabbits were subjected to a catheter-based electrophysiological study. Atrial tachyarrhythmia susceptibility was tested by burst pacing before and after infusion of increasing concentrations of acetylcholine. Both young and old rabbits were in normal sinus rhythm at the beginning of the infusion/burst pacing protocol. The old rabbits had faster heart rates and a marked increase in atrial tachyarrhythmias compared to the young rabbits. Nonsustained and sustained AF events were more frequent in the old rabbits. No significant fibrosis was observed in the atria of either young or old rabbits. In conclusion, the old rabbits have a greater propensity for induction of AF. The significantly faster heart rates in the old rabbits suggest that dominant sympathetic activity may play an important role in the propensity for AF in this group.

Experimental evaluation of the cardiac rhythm originating in myocardial sleeves of pulmonary veins using a monophasic action potential

Spontaneous depolarization similar to that from the sinus node was documented from the myocardial sleeves of pulmonary veins (PV) after isolation procedures. It was then hypothesized that sinus node-like tissue is present in the PVs of humans. Based on a number of features, the myocardium of myocardial sleeves (MS) is highly arrhythmogenic. Membrane potentials originating from MS are invariably recordable at the PVs ostia in patients with atrial fibrillation (AF) and delayed conduction around the PVs ostia may play a role in re-entry process responsible for the initiation and maintenance of AF. Diagnostic and therapeutic evidence of premature atrial beats induced in MS of PVs and resulting in launch of AF was detected by 3D electroanatomic method of monophasic action potential (MAP). MAP recording plays an important role in a direct view of human myocardial electrophysiology under both physiological and pathological conditions. Its crucial importance lies in the fact that it enables the study of the action potential of myocardial cell in vivo and, therefore, the study of the dynamic relation of this potential with all the organism variables. The knowledge of pathological MAPs from PV myocardial sleeves can help us to confirm a diagnosis when finding the similar action potential morphology. MAP can be also used to evaluate the therapeutic efficiency of vagal nerves suppression, radiofrequency ablation or other treatment procedures in PVs myocardial sleeves as well as for post-treatment following up.

The Role of the Atrial Neural Network In Atrial Fibrillation: The Metastatic Progression Hypothesis

With the advent of catheter ablation of atrial fibrillation (AF) there has been acceleration in our understanding of the mechanisms underlying the etiology of this common clinical arrhythmia. In this regard, the role of the intrinsic cardiac autonomic nervous system in the initiation and maintenance of AF began to receive attention in numerous experimental and clinical investigations. Up to now, the focus has been on the large ganglionated plexi (GP) which are located in the posterior left atrium mainly at the pulmonary vein-atrial junctions. As long term outcomes have been reported and single procedures have indicated diminished success rates particularly for persistent/long standing persistent AF, emphasis has begun to shift away from the pulmonary vein isolation (PVI) alone as well as GP ablation with or without PVI. An understanding of the atrial substrate represented by the extensions of the intrinsic cardiac autonomic system constituting the atrial neural network is beginning to evolve. In this review, the contribution of the intrinsic cardiac autonomic nervous system to the etiology of AF is addressed, particularly in regard to the greater prevalence of AF in the elderly. In addition, we emphasize the involvement of the atrial neural network in the "metastatic" progression of paroxysmal to persistent and long standing persistent forms of AF.

Inhibition of atrial fibrillation by low-level vagus nerve stimulation: the role of the nitric oxide signaling pathway

PURPOSE

We examined the role of the phosphatidylinositol-3 kinase (PI3K)/nitric oxide (NO) signaling pathway in low-level vagus nerve stimulation (LLVNS)-mediated inhibition of atrial fibrillation (AF).

METHODS

In 17 pentobarbital anesthetized dogs, bilateral thoracotomies allowed the attachment of electrode catheters to the superior and inferior pulmonary veins and atrial appendages. Rapid atrial pacing (RAP) was maintained for 6 h. Each hour, programmed stimulation was used to determine the window of vulnerability (WOV), a measure of AF inducibility, at all sites. During the last 3 h, RAP was overlapped with right LLVNS (50 % below that which slows the sinus rate). In group 1 (n = 7), LLVNS was the only intervention, whereas in groups 2 (n = 6) and 3 (n = 4), the NO synthase inhibitor N (G)-nitro-L-arginine methyl ester (L-NAME) and the PI3K inhibitor wortmannin, respectively, were injected in the right-sided ganglionated plexi (GP) during the last 3 h. The duration of acetylcholine-induced AF was determined at baseline and at 6 h. Voltage-sinus rate curves were constructed to assess GP function.

RESULTS

LLVNS significantly decreased the acetylcholine-induced AF duration by 8.2 ± 0.9 min (p < 0.0001). Both L-NAME and wortmannin abrogated this effect. The cumulative WOV (the sum of the individual WOVs) decreased toward baseline with LLVNS (p < 0.0001). L-NAME and wortmannin blunted this effect during the fifth (L-NAME only, p < 0.05) and the sixth hour (L-NAME and wortmannin, p < 0.05). LLVNS suppressed the ability of GP stimulation to slow the sinus rate, whereas L-NAME and wortmannin abolished this effect.

CONCLUSION

The anti-arrhythmic effects of LLVNS involve the PI3K/NO signaling pathway.

2012 HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for patient selection, procedural techniques, patient management and follow-up, definitions, endpoints, and research trial design

This is a report of the Heart Rhythm Society (HRS) Task Force on Catheter and Surgical Ablation of Atrial Fibrillation, developed in partnership with the European Heart Rhythm Association (EHRA), a registered branch of the European Society of Cardiology and the European Cardiac Arrhythmia Society (ECAS), and in collaboration with the American College of Cardiology (ACC), American Heart Association (AHA), the Asia Pacific Heart Rhythm Society (APHRS), and the Society of Thoracic Surgeons (STS). This is endorsed by the governing bodies of the ACC Foundation, the AHA, the ECAS, the EHRA, the STS, the APHRS, and the HRS.

The intrinsic autonomic nervous system in atrial fibrillation: a review

The procedure of catheter ablation for the treatment of drug resistant atrial fibrillation (AF) has evolved but still relies on lesion sets intended to isolate areas of focal firing, mainly the myocardial sleeves of the pulmonary veins (PVs), from the rest of the atria. However the success rates for this procedure have varied inversely with the type of AF. At best success rates have been 20 to 30% below that of other catheter ablation procedures for Wolff-Parkinson-White syndrome, atrioventricular junctional re-entrant tachycardia and atrial flutter. Basic and clinical evidence has emerged suggesting a critical role of the ganglionated plexi (GP) at the PV-atrial junctions in the initiation and maintenance of the focal form of AF. At present the highest success rates have been obtained with the combination of PV isolation and GP ablation both as catheter ablation or minimally invasive surgical procedures. Various lines of evidence from earlier and more recent reports provide that both neurally based and myocardially based forms of AF can separately dominate or coexist within the context of atrial remodeling. Future studies are focusing on non-pharmacological, non-ablative approaches for the prevention and treatment of AF in order to avoid the substantive complications of both these regimens.

Pharmacological prevention and termination of focal atrial fibrillation

AIMS

Patients undergo ablation for focal atrial fibrillation (AF) as a result of failure of anti-arrhythmic drugs. Our basic studies have implicated cholinergic and adrenergic neurotransmitter release as the underlying mechanism for focal AF. Therefore, we tested the efficacy of a combination of sodium channel-blocking agents with additional vagolytic properties and a β-blocker to terminate and prevent focal AF.

METHODS AND RESULTS

In 18 Na-pentobarbital-anaesthetized dogs, after a right or left thoracotomy, acetylcholine (Ach, 0.5 cc, 100 mM) was injected into a fat pad containing ganglionated plexi (GP) or applied on an atrial appendage (AA) to induce focal firing at the pulmonary veins (PVs) or AA, respectively. Disopyramide (2-4 mg/kg, n= 6) or quinidine (3-6 mg/kg, n= 12) combined with esmolol or propranolol (1 mg/kg, n= 13 and 5, respectively) were slowly injected to terminate (Group I, n= 12) or prevent (Group II, n= 6) Ach-induced sustained focal AF. In another four dogs, only the sodium channel-blocking agents with additional vagolytic properties or only the β-blocker was injected prior to or after the initiation of focal AF. At baseline, the mean duration of AF induced by Ach was 26 ± 4 min. Group I: After drugs, Ach-induced AF duration was 3 ± 1 min (P< 0.001). Group II: Prior to drugs, Ach-induced AF lasted for 19 ± 3 min. With the drug combination the duration of Ach-induced AF, decreased to 6 ± 1/min, P< 0.001. Either quinidine or propranolol alone did not change the duration of Ach-induced AF, mean 25 ± 10 min compared with Ach alone, 28 ± 16 min, P= 0.2.

CONCLUSIONS

Type IA (cholinergic antagonist) plus Type II (β-adrenergic antagonist) provides significant prevention and suppression of focal AF arising at PV and non-PV sites.

The role of ganglionated plexi in apnea-related atrial fibrillation

OBJECTIVES

This study was conducted to simulate sleep apnea-induced atrial fibrillation (AF) in an experimental model and to determine whether neural ablation will prevent AF.

BACKGROUND

An increasing number of clinical reports have associated sleep apnea and AF, and many possible mechanisms responsible for this relationship have been proposed.

METHODS

Thirty dogs anesthetized with Na-pentobarbital were ventilated by a positive pressure respirator. Protocol 1 (n = 14): After a right thoracotomy, atrial and pulmonary vein programmed pacing at 2x and 4x threshold determined the shortest atrial refractory period. Obstructive apnea was induced by turning off the respirator during end expiration for 2 min. During apnea, programmed pacing was performed with S1-S2 = 5 to 10 ms earlier than the atrial refractory period. Neural activity was monitored from the ganglionated plexi (GP) adjacent to the right pulmonary veins. Protocol 2 (n = 16): Electrical stimulation identified the GP at the right pulmonary artery (RPA). Programmed pacing was again instituted, below atrial refractory period, during 2 min of apnea. After radiofrequency ablation of the RPA GP, continuous programmed pacing was again repeated during 2 min of apnea. In 5 dogs, blood gases were determined at baseline and at 2 min of apnea.

RESULTS

Protocol 1: During apnea, S1-S2 induced AF within 85 +/- 38 s (9 of 10). In 1 case, AF occurred spontaneously at 1 min 36 s of apnea. Recorded GP neural activity progressively increased before AF onset. Systolic but not diastolic blood pressure rose significantly before AF (149 +/- 26 mm Hg to 193 +/- 38 mm Hg, p < 0.05). In 4 dogs, autonomic blockade prevented apnea-induced AF. Protocol 2: AF induced by pacing occurred in 8 of 11 dogs within the 2-min period of apnea, before neural ablation. After ablation, 0 of 6 showed AF during 2 min of apnea (p = 0.009).

CONCLUSIONS

This experimental model of apnea shows a reproducible incidence of AF. After neural ablation of the RPA GP or autonomic blockade, AF inducibility was significantly inhibited.

Low-Level Vagosympathetic Stimulation

Background— We used high-frequency stimulation delivered during the refractory period of the atrium and pulmonary veins (PVs) to induce focal firing and atrial fibrillation (AF). This study was designed to demonstrate that bilateral low-level vagosympathetic nerve stimulation (LL-VNS) could suppress high-frequency stimulation-induced focal AF at atrial and PV sites.

Methods and Results— In 23 dogs anesthetized with Na-pentobarbital, electrodes in the vagosympathetic trunks allowed LL-VNS at 1 V below that which slowed the sinus rate or atrioventricular conduction. Multielectrode catheters were fixed at the right and left superior and inferior PVs and both atrial appendages. LL-VNS continued for 3 hours. At the end of each hour, the high-frequency stimulation algorithm consisting of a 40-ms train of stimuli (200 Hz; stimulus duration, 0.1 to 1.0 ms) was delivered 2 ms after the atrial pacing stimulus during the refractory period at each PV and atrial appendages site. The lowest voltage of high-frequency stimulation that induced AF was defined as the AF threshold. Five dogs without LL-VNS served as sham controls. Six dogs underwent LL-VNS after transection of bilateral vagosympathetic trunks. LL-VNS induced a progressive increase in AF threshold at all PV and atrial appendages sites, particularly significant ( P <0.05) at the right superior PV, right inferior PV, left superior PV, and right atrial appendage. Bilateral vagosympathetic transection did not significantly alter the previous findings, and the 5 sham control dogs did not show changes in AF threshold at any site over a period of 3 hours.

Conclusions— LL-VNS may prevent episodic AF caused by rapid PV and non-PV firing.

The Autonomic Nervous System and Atrial Fibrillation:The Roles of Pulmonary Vein Isolation and Ganglionated Plexi Ablation

After the sequential successes of catheter ablation for the treatment of pre-excitation syndromes (WPW), junctional reentry (AVNRT) atrial flutter (AFL) and ventricular arrhythmias, clinical electrophysiologists have focused on the myocardial basis of atrial fibrillation (AF). Thus, the strategy for ablation of drug and cardioversion refractory AF was to isolate the myocardial connections from the focal firing pulmonary veins (PVs) in addition to altering the atrial substrate maintaining AF. However, the overall success rates have not achieved those of the other types of ablation procedures. In this review we have summarized the favorable aspects and drawbacks of pulmonary vein isolation (PVI). As for the role of the Intrinsic Cardiac Autonomic Nervous System (ICANS), both basic and clinical evidence has shown that ganglionated plexi (GP) stimulation promotes initiation and maintenance of AF, and that GP ablation reduces recurrence of AF following catheter or surgical ablation of these structures. Based on these findings, the GP Hyperactivity Hypothesis has been proposed to explain, at least in part, the mechanistic basis for the focal form of AF. For example, PV isolation may not always be necessary for elimination of AF, as in the early stages of paroxysmal AF. GP ablation alone, in these cases, may suffice for focal AF termination. In the persistent and long standing persistent forms the substrate for AF may be more extensive and therefore require GP ablation plus PV isolation and/or CFAE ablations. Clinical reports, both catheter based as well as minimally invasive surgical procedures, which include PVI plus GP ablation have shown relatively long-term success rates much closer to or equal to those achieved by myocardial ablation procedures in patients with WPW, AVNRT and AFL.

Calmodulin kinase II-mediated sarcoplasmic reticulum Ca2+ leak promotes atrial fibrillation in mice

A trial fibrillation (AF), the most common human cardiac arrhythmia, is associated with abnormal intracellular Ca2+ handling. Diastolic Ca2+ release from the sarcoplasmic reticulum via "leaky" ryanodine receptors (RyR2s) is hypothesized to contribute to arrhythmogenesis in AF, but the molecular mechanisms are incompletely understood. Here, we have shown that mice with a genetic gain-of-function defect in Ryr2 (which we termed Ryr2R176Q/+ mice) did not exhibit spontaneous AF but that rapid atrial pacing unmasked an increased vulnerability to AF in these mice compared with wild-type mice. Rapid atrial pacing resulted in increased Ca2+/calmodulin-dependent protein kinase II (CaMKII) phosphorylation of RyR2, while both pharmacologic and genetic inhibition of CaMKII prevented AF inducibility in Ryr2R176Q/+ mice. This result suggests that AF requires both an arrhythmogenic substrate (e.g., RyR2 mutation) and enhanced CaMKII activity. Increased CaMKII phosphorylation of RyR2 was observed in atrial biopsies from mice with atrial enlargement and spontaneous AF, goats with lone AF, and patients with chronic AF. Genetic inhibition of CaMKII phosphorylation of RyR2 in Ryr2S2814A knockin mice reduced AF inducibility in a vagotonic AF model. Together, these findings suggest that increased RyR2-dependent Ca2+ leakage due to enhanced CaMKII activity is an important downstream effect of CaMKII in individuals susceptible to AF induction.

Autonomic mechanism for initiation of rapid firing from atria and pulmonary veins: evidence by ablation of ganglionated plexi

AIMS

Previous studies showed that autonomic activation by high-frequency electrical stimulation (HFS) during myocardial refractoriness evokes rapid firing from pulmonary vein (PV) and atria, both in vitro and in vivo. This study sought to investigate the autonomic mechanism underlying the rapid firings at various sites by systematic ablation of multiple ganglionated plexi (GP).

METHODS AND RESULTS

In 43 mongrel dogs, rapid firing-mediated atrial fibrillation (AF) was induced by local HFS (200 Hz, impulse duration 0.1 ms, train duration 40 ms) to the PVs and atria during myocardial refractoriness. The main GP in the atrial fat pads or the ganglia along the ligament of Marshall (LOM) were then ablated. Ablation of the anterior right GP and inferior right GP significantly increased the AF threshold by HFS at the right atrium and PVs. The AF threshold at left atrium and PVs was significantly increased by ablation of the superior left GP and inferior left GP, and was further increased by ablation of the LOM. Ablation of left- or right-sided GP on the atria had a significant effect on contralateral PVs and atrium. Administration of esmolol (1 mg/kg) or atropine (1 mg) significantly increased AF threshold at all sites.

CONCLUSION

HFS applied to local atrial and PV sites initiated rapid firing via activation of the interactive autonomic network in the heart. GP in either left side or right side contributes to the rapid firings and AF originating from ipsolateral and contralateral PVs and atrium. Autonomic denervation suppresses or eliminates those rapid firings.