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

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.

Sex Differences in the Regional Analysis of Nonpulmonary Vein Foci and Epicardial Adipose Tissue in Patients With Atrial Fibrillation

BACKGROUND

The mechanism underlying the sex differences in atrial fibrillation (AF) recurrence following pulmonary vein (PV) isolation is not fully understood. We hypothesized that non-PV foci and epicardial adipose tissue (EAT) play a key role.Methods and Results: Data from 304 consecutive patients (75% males) who underwent contrast-enhanced computed tomography and catheter ablation of AF were reviewed. The EAT around the atrium was measured separately in 4 parts of the atrium. All patients underwent high-dose isoproterenol infusions to assess the non-PV foci. Significantly more non-PV foci and less EAT around the atrium were observed in female patients than in male patients. In males, those with non-PV foci on the left atrial (LA) anterior wall had significantly greater EAT for the same lesions than those without non-PV foci. During a median follow-up of 27 months, the predictors of AF recurrence after first catheter ablation were female sex, presence of non-PV foci, LA diameter, and septal EAT index. A sex-specific analysis revealed that LA diameter was a predictor only in males and that the presence of non-PV foci in the septal region was a strong predictor in males (hazard ratio [HR]: 2.24) and females (HR: 3.65).

CONCLUSIONS

Sex-specific differences were observed in non-PV foci sites and local EAT and in regard to the predictors of AF recurrence.

Severe coronary artery spasm during left atrial appendage closure plus catheter ablation for atrial fibrillation: case presentation

Background

Left atrial appendage closure (LAAC) combined with radiofrequency catheter ablation (RFCA) as a hybrid procedure is commonly performed to treat atrial fibrillation (AF). Although this treatment carries a low risk of coronary artery spasm (CAS), and has never been observed in LAAC procedure, caution still needed to be taken. We presented a case of CAS that occurred in an AF patient during the hybrid procedure.

Case presentation

The patient was a 65-year-old man with paroxysmal AF who developed CAS during RFCA and LAAC. In this case, LAAC was performed ahead of RFCA. After atrial septal puncture, the occluder was advanced into left atrium through delivery sheath, and successfully deployed in the LAA. After verifying the assessment of “PASS” criteria, we decided to release the device. However, before releasing the occluder in LAAC, the patient’s blood pressure (BP) fell to 70/45 mmHg with heart rate (HR) drop and ST-segment elevation in II, III, and aVF and reciprocal ST-segment depression in I and aVL. Isotonic sodium chloride load was administered. After 3 min, the BP and HR raised, and ST-segment returned to normal. The occluder was successfully released after the stable condition of the patient. Then, RFCA was sequentially performed. When isolating the right pulmonary veins, the patient’s BP and HR fell again with ST-segment elevation in inferior leads. Spontaneous ventricular tachycardia and fibrillation developed rapidly and defibrillation was performed immediately with success. Coronary angiography revealed the obstruction of the right coronary artery which disappeared completely after intracoronary nitroglycerin injection (1 mg). Under systemic diltiazem infusion, the RFCA procedure was accomplished. After the procedure, the patient recovered without any neurologic deficit, and CAS has never recurred with isosorbide mononitrate treatment during follow-up.

Conclusions

CAS is a rare complication associated with AF hybrid procedure. Attention should be paid to this rare but potentially life-threatening complication.

Location of Parasympathetic Innervation Regions From Electrograms to Guide Atrial Fibrillation Ablation Therapy: An in silico Modeling Study

The autonomic nervous system (ANS) plays an essential role in the generation and maintenance of cardiac arrhythmias. The cardiac ANS can be divided into its extrinsic and intrinsic components, with the latter being organized in an epicardial neural network of interconnecting axons and clusters of autonomic ganglia called ganglionated plexi (GPs). GP ablation has been associated with a decreased risk of atrial fibrillation (AF) recurrence, but the accurate location of GPs is required for ablation to be effective. Although GP stimulation triggers both sympathetic and parasympathetic ANS branches, a predominance of parasympathetic activity has been shown. This study aims was to develop a method to locate atrial parasympathetic innervation sites based on measurements from a grid of electrograms (EGMs). Electrophysiological models representative of non-AF, paroxysmal AF (PxAF), and persistent AF (PsAF) tissues were developed. Parasympathetic effects were modeled by increasing the concentration of the neurotransmitter acetylcholine (ACh) in randomly distributed circles across the tissue. Different circle sizes of ACh and fibrosis geometries were considered, accounting for both uniform diffuse and non-uniform diffuse fibrosis. Computational simulations were performed, from which unipolar EGMs were computed in a 16 × 1 6 electrode mesh. Different distances of the electrodes to the tissue (0.5, 1, and 2 mm) and noise levels with signal-to-noise ratio (SNR) values of 0, 5, 10, 15, and 20 dB were tested. The amplitude of the atrial EGM repolarization wave was found to be representative of the presence or absence of ACh release sites, with larger positive amplitudes indicating that the electrode was placed over an ACh region. Statistical analysis was performed to identify the optimal thresholds for the identification of ACh sites. In all non-AF, PxAF, and PsAF tissues, the repolarization amplitude rendered successful identification. The algorithm performed better in the absence of fibrosis or when fibrosis was uniformly diffuse, with a mean accuracy of 0.94 in contrast with a mean accuracy of 0.89 for non-uniform diffuse fibrotic cases. The algorithm was robust against noise and worked for the tested ranges of electrode-to-tissue distance. In conclusion, the results from this study support the feasibility to locate atrial parasympathetic innervation sites from the amplitude of repolarization wave.

The anatomical basis behind the neuromodulation effects associated with pulmonary vein isolation

The anatomical basis underlying the neuromodulation effects seen with pulmonary vein (PV) isolation (PVI) is not fully understood. Left atrial (LA) electro-anatomical maps of 38 patients who underwent catheter cardioneuroablation for vagally mediated bradycarrhythmias were studied. During the procedure, LA ganglionic plexi (GPs) were systematically identified and ablated. Design PVI lines were created on these maps by a blinded observer, and the degree of overlap between four GPs and individual PVs was assessed. Here, 1.7 ± 7 (35.5 ± 17.0%) of the total 31.6 ± 10 GP ablation sites per patient were found to overlap with the design PVI lines. The overlap was higher for the right-sided GPs, p < .001. The degree of GP-PV overlap varied: 1 PV in 5 (13.2%) patients, 2 PVs in 15 (39.2%), 3 PVs in 16 (42.1%), and all 4 PVs in 2 (5.3%). No patient had zero GP-PV overlap. A vagal response was most commonly observed during ablation at the left superior GP (89.5%), while a sympathetic response was observed most often during the right superior GP ablation (97.4%). Some degree of GP-PV antral overlap is the norm, and this is more pronounced for the right-sided PVs. There is significant individual variability in the degree of overlap which may explain why neuromodulation effects are not seen universally following PVI.

Hemodynamic Management of Patients with Ejection Fraction < 50% Undergoing Pulmonary Vein Ablation

There is no consensus regarding optimal methodology forblood pressure monitoring inpatients with a depressed ejection fraction undergoingcatheter ablationfor atrial fibrillation. Our goalswere to determine ifhemodynamicmanagementdifferences exist during radiofrequency ablation for atrial fibrillation in patients with and without an ejection fraction< 50%, and whether management was influenced by the utilization of invasive arterial blood pressure monitoring. This single-center trial retrospectively compared blood pressure management during catheterablation of atrial fibrillationin all patients with an ejection fraction< 50% over a 2-year span (n=44), and compared to an age-matched cohort with preserved ejection fraction ablated over the same span in time (n=44). Blood pressure was not significantly managed differently between the groups, and did not appear to be influenced by the use of invasive arterial blood pressure monitoring.Hemodynamic management is similar across the spectrum of ejection fraction, regardless of invasive arterial blood pressure monitoring, which challenges the need for invasive arterial blood pressure monitoringduringcatheter ablation ofatrial fibrillationin left ventricular systolic dysfunction.

Effect of obesity and epicardial fat/fatty infiltration on electrical and structural remodeling associated with atrial fibrillation in a novel canine model of obesity and atrial fibrillation: A comparative study

BACKGROUND

How obesity and epicardial fat influence atrial fibrillation (AF) is unknown.

METHODS

To investigate the effect of obesity/epicardial fat on the AF substrate, we divided 20 beagle dogs of normal weight into four groups (n = 5 each): one of the four groups (Obese-rapid atrial pacing [RAP] group) served as a novel canine model of obesity and AF. The other three groups comprised dogs fed a standard diet without RAP (Control group), dogs fed a high-fat diet without RAP (Obese group), or dogs fed a standard diet with RAP (RAP group). All underwent electrophysiology study, and hearts were excised for histopathologic and fibrosis-related gene expression analyses.

RESULTS

Left atrial (LA) pressure was significantly higher in the Obese group than in the Control, RAP, and Obese-RAP groups (23.4 ± 6.9 vs. 11.4 ± 2.1, 11.9 ± 6.4, and 13.5 ± 2.9 mmHg; p = .005). The effective refractory period of the inferior PV was significantly shorter in the RAP and Obese-RAP groups than in the Control group (p = .043). Short-duration AF was induced at greatest frequency in the Obese-RAP and Obese groups (p < .05). Epicardial fat/Fatty infiltration was greatest in the Obese-RAP group, and greater in the Obese and RAP groups than in the Control group. %interstitial fibrosis/fibrosis-related gene expression was significantly greater in the Obese-RAP and RAP groups (p < .05).

CONCLUSIONS

Vulnerability to AF was associated with increased LA pressure and increased epicardial fat/fatty infiltration in our Obese group, and with increased epicardial fat/fibrofatty infiltration in the RAP and Obese-RAP groups. These may explain the role of obesity/epicardial fat in the pathogenesis of AF.

Incidence and Characteristics of Coronary Artery Spasms Related to Atrial Fibrillation Ablation Procedures - Large-Scale Multicenter Analysis

BACKGROUND

Coronary artery spasms (CASs), which can cause angina attacks and sudden death, have been recently reported during catheter ablation. The aim of the present study was to report the incidence, characteristics, and prognosis of CASs related to atrial fibrillation (AF) ablation procedures.Methods and Results:The AF ablation records of 22,232 patients treated in 15 Japanese hospitals were reviewed. CASs associated with AF ablation occurred in 42 of 22,232 patients (0.19%). CASs occurred during ablation energy applications in 21 patients (50%). CASs also occurred before ablation in 9 patients (21%) and after ablation in 12 patients (29%). The initial change in the electrocardiogram was ST-segment elevation in the inferior leads in 33 patients (79%). Emergency coronary angiography revealed coronary artery stenosis and occlusions, which were relieved by nitrate administration. No air bubbles were observed. A comparison of the incidence of CASs during pulmonary vein isolation between the different ablation energy sources revealed a significantly higher incidence with cryoballoon ablation (11/3,288; 0.34%) than with radiofrequency catheter, hot balloon, or laser balloon ablation (8/18,596 [0.04%], 0/237 [0%], and 0/111 [0%], respectively; P<0.001). CASs most often occurred during ablation of the left superior pulmonary vein. All patients recovered without sequelae.

CONCLUSIONS

CASs related to AF ablation are rare, but should be considered as a dangerous complication that can occur anytime during the periprocedural period.

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.

Comparative effects of intensive ganglionated plexus ablation in treating paroxysmal atrial fibrillation and vasovagal syncope

BACKGROUND

Ganglionated plexus (GP) ablation is used to treat atrial fibrillation (AF) and vasovagal syncope (VVS). However, the comparative effects of GP ablation in treating paroxysmal atrial fibrillation (PAF) and VVS have not been well studied.

OBJECTIVE

The purpose of this study was to investigate the effects of intensive GP ablation on PAF and VVS.

METHODS

PAF and VVS patients were enrolled in this study. Pulmonary vein isolation (PVI) was performed in the PAF group, and additional ablation was performed at GP sites. Anatomic ablation of left atrial GPs was performed in the VVS group. The primary endpoint was freedom from AF or other sustained atrial tachycardia and syncope recurrence.

RESULTS

A total of 195 patients were enrolled: 146 patients with PAF, including eight patients with combined VVS (PAF group), and 49 patients with VVS (VVS group). Vasovagal response (VR) was achieved in 78 (53.4%) patients in the PAF group and 48 patients (98.0%) in the VVS group (P < .05). During the 17.8 ± 10.5 (range, 3-42) month follow-up, 126 (86.3%) patients were free of AF in the PAF group, and 45 (91.8%) patients in the VVS group had no syncope recurrence and significantly improved symptoms.

CONCLUSIONS

Anatomically guided intensive GP ablation showed efficient clinical outcomes for both groups of patients. Compared with PAF patients, VVS patients had more VR during ablation in the left atrium. Furthermore, VR during ablation indicated a better prognosis in PAF patients.

Evidence of structural and functional plasticity occurring within the intracardiac nervous system of spontaneously hypertensive rats

We have developed intracardiac neuron whole cell recording techniques in atrial preparations from control and spontaneous hypertensive rats. This has enabled the identification of significant synaptic plasticity in the intracardiac nervous system, including enhanced postsynaptic current frequency, increased synaptic terminal density, and altered postsynaptic receptors. This increased synaptic drive together with altered cardiac neuron electrophysiology could increase intracardiac nervous system excitability and contribute to the substrate for atrial arrhythmia in hypertensive heart disease.

Year in Review in Cardiac Electrophysiology

In the past year, there have been numerous advances in our understanding of arrhythmia mechanisms, diagnosis, and new therapies. We have seen advances in basic cardiac electrophysiology with data suggesting that secretoneurin may be a biomarker for patients at risk of ventricular arrhythmias, and we have learned of the potential role of an NPR-C (natriuretic peptide receptor-C) in atrial fibrosis and the role of an atrial specific 2-pore potassium channel TASK-1 as a therapeutic target for atrial fibrillation. We have seen studies demonstrating the role of sensory neurons in sleep apnea-related atrial fibrillation and the association between bariatric surgery and atrial fibrillation ablation outcomes. Artificial intelligence applied to electrocardiography has yielded estimates of age, sex, and overall health. We have seen new tools for collection of patient-centered outcomes following catheter ablation. There have been significant advances in the ability to identify ventricular tachycardia termination sites through high-density mapping of deceleration zones. We have learned that right ventricular dysfunction may be a predictor of survival benefit after implantable cardioverter-defibrillator implantation in patients with nonischemic cardiomyopathy. We have seen further insights into the role of His bundle pacing on improving outcomes. As our understanding of cardiac laminopathies advances, we may have new tools to predict arrhythmic event rates in gene carriers. Finally, we have seen numerous advances in the treatment of arrhythmias in patients with congenital heart disease.