Atrial autonomic innervation remodelling and atrial fibrillation inducibility after epicardial ganglionic plexi ablation

lncRNA-056298 Regulates GAP43 and Promotes Cardiac Intrinsic Autonomic Nerve Remodelling in a Canine Model of Atrial Fibrillation Induction after Ganglionated Plexus Ablation

BACKGROUND

Cardiac intrinsic autonomic nerve remodelling has been reported to play an important role in the recurrence of atrial fibrillation after radiofrequency ablation, which significantly affects the long-term efficacy of this procedure. lncRNAs have been shown to interact in the pathological processes underlying heart diseases. However, the roles and mechanisms of lncRNAs in cardiac intrinsic autonomic nerve remodelling during atrial fibrillation reduction after ganglionated plexus ablation remain unknown.

OBJECTIVE

The aim of this study was to investigate the mechanism by which lncRNA- 056298 modulates GAP43 to affect cardiac intrinsic autonomic nerve remodelling and facilitate the induction of atrial fibrillation after ganglionated plexus ablation.

METHODS

A canine model of right atrial ganglionated plexus ablation was established. The atrial electrophysiological characteristics and neural markers were detected before and after 6 months of ganglionated plexus ablation. High-throughput sequencing was used to screen differentially expressed lncRNAs in target atrial tissues, and lncRNA- 056298 was selected to further explore its effects and mechanisms on cardiac intrinsic autonomic nerve remodelling.

RESULTS

The induction rate of atrial fibrillation increased in dogs after ganglionated plexus ablation. Overexpression of lncRNA-056298 by lentivirus can shorten the atrial effective refractory period and increase the induction of atrial fibrillation. lncRNA- 056298 promoted cardiac intrinsic autonomic nerve remodelling via endogenous competition with cfa-miR-185 to induce transcription of its target gene GAP43, thereby affecting the induction of atrial fibrillation.

CONCLUSION

lncRNA-056298 regulates GAP43 by sponging miR-185, which affects cardiac intrinsic autonomic nerve remodelling and mediates atrial fibrillation induction after ganglionated plexus ablation.

Biomarker Periodic Repolarization Dynamics Indicates Enhanced Risk for Arrhythmias and Sudden Cardiac Death in Myocardial Infarction in Pigs

BACKGROUND

Periodic repolarization dynamics (PRD) is an electrocardiographic biomarker that captures repolarization instability in the low frequency spectrum and is believed to estimate the sympathetic effect on the ventricular myocardium. High PRD indicates an increased risk for postischemic sudden cardiac death (SCD). However, a direct link between PRD and proarrhythmogenic autonomic remodeling has not yet been shown.

METHODS AND RESULTS

We investigated autonomic remodeling in pigs with myocardial infarction (MI)-related ischemic heart failure induced by balloon occlusion of the left anterior descending artery (n=17) compared with pigs without MI (n=11). Thirty days after MI, pigs demonstrated enhanced sympathetic innervation in the infarct area, border zone, and remote left ventricle paralleled by altered expression of autonomic marker genes/proteins. PRD was enhanced 30 days after MI compared with baseline (pre-MI versus post-MI: 1.75±0.30 deg2 versus 3.29±0.79 deg2, P<0.05) reflecting pronounced autonomic alterations on the level of the ventricular myocardium. Pigs with MI-related ventricular fibrillation and SCD had significantly higher pre-MI PRD than pigs without tachyarrhythmias, suggesting a potential role for PRD as a predictive biomarker for ischemia-related arrhythmias (no ventricular fibrillation versus ventricular fibrillation: 1.50±0.39 deg2 versus 3.18±0.53 deg2 [P<0.05]; no SCD versus SCD: 1.67±0.32 deg2 versus 3.91±0.63 deg2 [P<0.01]).

CONCLUSIONS

We demonstrate that ischemic heart failure leads to significant proarrhythmogenic autonomic remodeling. The concomitant elevation of PRD levels in pigs with ischemic heart failure and pigs with MI-related ventricular fibrillation/SCD suggests PRD as a biomarker for autonomic remodeling and as a potential predictive biomarker for ventricular arrhythmias/survival in the context of MI.

Pinocembrin attenuates susceptibility to atrial fibrillation in rats with pulmonary arterial hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is a disease characterized by pulmonary vascular remodeling that triggers fibrosis and excessive myocardium apoptosis, ultimately facilitating atrial fibrillation (AF). In various rat models, Pinocembrin has anti-fibrotic and anti-apoptotic effects, reducing arrhythmia vulnerability. However, whether pinocembrin alleviates to AF in a PAH model remains unclear. The experiment aims to investigate how pinocembrin affects AF susceptibility in PAH rats and the possible mechanisms involved.

METHODS

The PAH model was induced by monocrotaline (MCT; i. p. 60 mg/kg). Concurrently, rats received pinocembrin (i.p.50 mg/kg) or saline. Hemodynamics parameters, electrocardiogram parameters, lung H.E. staining, atrial electrophysiological parameters, histology, Western blot, and TUNEL assay were detected.

RESULTS

Compared to the control rats, MCT-induced PAH rats possessed prominently enhancive mPAP (mean pulmonary artery pressure), pulmonary vascular remodeling, AF inducibility, HRV, right atrial myocardial fibrosis, apoptosis, atrial ERP, APD, and P-wave duration. Additionally, there were lowered protein levels of Cav1.2, Kv4.2, Kv4.3, and connexin 40 (CX40) in the MCT group in right atrial tissue. However, pinocembrin reversed the above pathologies and alleviated the activity of the Rho A/ROCKs signaling pathway, including the expression of Rho A, ROCK1, ROCK2, and its downstream MYPT-1, LIMK2, BCL-2, BAX, cleaved-caspase3 in right atrial and HL-1 cells.

CONCLUSION

Present data exhibited pinocembrin attenuated atrial electrical, ion-channel, and autonomic remodeling, diminished myocardial fibrosis and apoptosis levels, thereby reducing susceptibility to AF in the MCT-induced PAH rats. Furthermore, we found that pinocembrin exerted inhibitory action on the Rho A/ROCK signaling pathway, which may be potentially associated with its anti-AF effects.

Long-term outcomes of a time to isolation - based strategy for cryoballoon ablation compared to radiofrequency ablation in patients with symptomatic paroxysmal atrial fibrillation

BACKGROUND

Cryoballoon ablation (CBA) is one of the most commonly used technologies designed for pulmonary vein isolation (PVI) for paroxysmal atrial fibrillation (PAF), although the dosing of CBA remains controversial. We evaluated the long-term efficacy and safety of a novel individualized strategy of CBA compared to radiofrequency ablation (RFA) for patients with PAF.

METHODS

In this observational study, symptomatic patients with drug-refractory paroxysmal AF were prospectively consented and enrolled in four centers, being assigned either to the CBA or RFA arm for ablation. In the CBA group, we used a time to isolation (TTI) - based dosing protocol. The primary endpoint was the recurrence of atrial arrhythmia >30 s following a 90-day blanking period. The secondary endpoint was procedure-related complications and procedure parameters.

RESULTS

A total of 500 patients were recruited in either the CBA group (n = 247) or the RFA group (n = 253) between January 2017 and July 2018. After a median follow-up of 778 days, the atrial tachyarrhythmia-free survival was 71.7% in the CBA group and 67.0% in the RFA group. CBA and RFA displayed similar major or minor complication occurrence, while the former had a significantly shorter procedure duration (82.5 min vs. 141.1 min, p < .001) and left atrial dwell time (60.1 min vs. 109.9 min, p < .001) but longer fluoroscopy exposure (13.8 min vs. 8.1 min, p < .001).

CONCLUSION

Compared to RFA, our TTI-based CBA dosing protocol showed comparable efficacy and safety, with a significantly reduced procedure duration in patients with PAF.

The Role of α7nAChR-Mediated Cholinergic Anti-Inflammatory Pathway in Vagal Nerve Regulated Atrial Fibrillation

The aim was to investigate the role of the α7nAChR-mediated cholinergic anti-inflammatory pathway in vagal nerve regulated atrial fibrillation (AF).18 beagles (standard dogs for testing) were used in this study, and the effective refractory period (ERP) of atrium and pulmonary veins and AF inducibility were measured hourly during rapid atrial pacing at 800 beats/minute for 6 hours in all beagles. After cessation of 3 hours of RAP, the low-level vagal nerve stimulation (LL-VNS) group (n = 6) was given LL-VNS and injection of salinne (0.5 mL/GP) into four GPs, the methyllycaconitine (MLA, the antagonist of α7nAChR) group (n = 6) was given LL-VNS and injection of MLA into four GPs, and the Control group (n = 6) was given saline into four GPs and the right cervical vagal nerve was exposed without stimulation. Then, the levels of the tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), acetylcholine (ACh), STAT3, and NF-κB proteins were measured. During the first 3 hours of RAP, the ERPs gradually decreased while the dispersion of ERPs (dERPs) and AF inducibility gradually increased in all three groups. During the last 3 hours of 6 hours' RAP in this study, the ERPs in the LL-VNS group were higher, while the dERPs and AF inducibility were significantly lower when compared with the Control and MLA groups at the same time points. The levels of ACh in the serum and atrium in the LL-VNS and MLA groups were higher than in the Control group, and the levels of TNF-α and IL-6 were higher in the Control and MLA groups than in the LL-VNS group. The concentrations of STAT3 in RA and LA tissues were higher in the LL-VNS group while those of NF-κB were lower.In conclusion, the cholinergic anti-inflammatory pathway mediated by α7nACh plays an important role in low-level vagal nerve-regulated AF.

Nerve distribution in myocardium including the atrial and ventricular septa in late stage human fetuses

Few information had been reported on deep intracardiac nerves in the myocardium of late human fetuses such as nerves at the atrial-pulmonary vein junction and in the atrial and ventricular septa. We examined histological sections of the heart obtained from 12 human fetuses at 25–33 weeks. A high density of intracardiac nerves was evident around the mitral valve annulus in contrast to few nerves around the tricuspid annulus. To the crux at the atrioventricular sulcus, the degenerating left common cardinal vein brought abundant nerve bundles coming from cardiac nerves descending along the anterior aspect of the pulmonary trunk. Likewise, nerve bundles in the left atrial nerve fold came from cardiac nerves between the ascending aorta and pulmonary artery. Conversely, another nerves from the venous pole to the atrium seemed to be much limited in number. Moreover, the primary atrial septum contained much fewer nerves than the secondary septum. Therefore, nerve density in the atrial wall varied considerably between sites. As ventricular muscles were degenerated from the luminal side for sculpturing of papillary muscles and trabeculae, deep nerves became exposed to the ventricular endothelium. Likewise, as pectineal muscles were sculptured, nerves were exposed in the atrial endothelium. Consequently, a myocardial assembly or sculpture seemed to be associated with degeneration and reconstruction of early-developed nerves. A failure in reconstruction during further expansion of the left atrium might be connected with an individual variation in anatomical substrates of atrial fibrillation.

Angiotensin-(1-7) attenuates atrial tachycardia-induced sympathetic nerve remodeling

Introduction:

The effect of Angiotensin-(1–7) (Ang-(1–7)) on atrial autonomic remodeling is still unknown. We hypothesized that Ang-(1–7) could inhibit sympathetic nerve remodeling in a canine model of chronic atrial tachycardia.

Materials and methods:

Eighteen dogs were randomly assigned to sham group, pacing group and Ang-(1–7) group. Rapid atrial pacing was maintained for 14 days in the pacing and Ang-(1–7) groups. Ang-(1–7) was administered intravenously in the Ang-(1–7) group. The atrial effective refractory period and atrial fibrillation inducibility level were measured at baseline and under sympathetic nerve stimulation after 14 days of measurement. The atrial sympathetic nerves labeled with tyrosine hydroxylase were detected using immunohistochemistry and Western blotting, and tyrosine hydroxylase and nerve growth factor mRNA levels were measured by reverse transcription polymerase chain reaction.

Results:

Pacing shortened the atrial effective refractory period and increased the atrial fibrillation inducibility level at baseline and under sympathetic nerve stimulation. Ang-(1–7) treatment attenuated the shortening of the atrial effective refractory period and the increase in the atrial fibrillation inducibility level. Immunohistochemistry and Western blotting showed sympathetic nerve hyperinnervation in the pacing group, while Ang-(1–7) attenuated sympathetic nerve proliferation. Ang-(1–7) alleviated the pacing-induced increases in tyrosine hydroxylase and nerve growth factor mRNA expression levels.

Conclusion:

Ang-(1–7) can attenuate pacing-induced atrial sympathetic hyperinnervation.

Heart rate variability after radiofrequency ablation of epicardial ganglionated plexuses on the ovine left atrium

Background

Ganglionated plexuses (GP) are terminal parts of cardiac autonomous nervous system (ANS). Radiofrequency ablation (RFA) for atrial fibrillation (AF) possibly affects GP. Changes in heart rate variability (HRV) after RFA can reflect ANS modulation.

Methods

Epicardial RFA of GP on the left atrium (LA) was performed under the general anesthesia in 15 mature Romanov sheep. HRV was used to assess the alterations in autonomic regulation of the heart. A 24 − hour ECG monitoring was performed before the ablation, 2 days after it and at each of the 12 following months. Ablation sites were evaluated histologically.

Results

There was an instant change in HRV parameters after the ablation. A standard deviation of all intervals between normal QRS (SDNN), a square root of the mean of the squared differences between successive normal QRS intervals (RMSSD) along with HRV triangular index (TI), low frequency (LF) power and high frequency (HF) power decreased, while LF/HF ratio increased. Both the SDNN, LF power and the HF power changes persisted throughout the 12 − month follow − up. Significant decrease in RMSSD persisted only for 3 months, HRV TI for 6 months and increase in LF/HF ratio for 7 months of the follow − up. Afterwards these three parameters were not different from the preprocedural values.

Conclusions

Epicardial RFA of GP’s on the ovine left atrium has lasting effect on the main HRV parameters (SDNN, HF power and LF power). The normalization of RMSSD, HRV TI and LF/HF suggests that HRV after epicardial RFA of GPs on the left atrium might restore over time.

Long-Term Effects of Ganglionated Plexi Ablation on Electrophysiological Characteristics and Neuron Remodeling in Target Atrial Tissues in a Canine Model

BACKGROUND

The long-term effects of ganglionated plexi ablation on electrophysiological characteristics and neuron remodeling in target atrial tissues remain unclear.

METHODS AND RESULTS

Dogs in group 1 (control, n=8) were not subjected to ganglionated plexi ablation and observed for 1 month, and dogs in groups 2 to 4 (ablation groups, n=8 each) underwent ablation of the right-sided ganglionated plexi and observed for 1, 6, and 12 months, respectively. Atrial electrophysiological characteristics were examined before ablation, immediately and continuously after ablation. Target atrial tissues were subjected to immunohistochemical staining and Western blot analysis. Atrial effective refractory period was significantly prolonged immediately after ablation (P<0.001), and persisted for 1 month (P<0.05). Nerve densities decreased 1 month after ablation (P<0.001). These parameters reverted to preablation levels after 6 and 12 months. In the ablation groups, atrial fibrillation was induced in 5 of 8 dogs after 1 month and in all animals after 6 and 12 months. Atrial fibrillation was not observed in the control group and in the experimental groups immediately after ablation. Moreover, the expression of the growth-associated protein 43 was upregulated after ablation.

CONCLUSIONS

Ganglionated plexi ablation effectively prolonged atrial effective refractory period for a short period, but the long-term effects on atrial effective refractory period and the suppression of atrial fibrillation induction were not persistent. Targeted atrial neuron remodeling may be an important mechanism underlying the observed electrophysiological changes.

Effects of renal sympathetic denervation on the atrial electrophysiology in dogs with pacing-induced heart failure

BACKGROUND

Heart failure (HF) and atrial fibrillation (AF) are associated with sympathetic activation. Renal sympathetic denervation (RSD) can suppress AF vulnerability. The impact of RSD on atrial electrophysiology in experimental HF is unclear.

METHODS

Twenty-two beagles were randomized into control, HF, and HF + RSD groups. Control dogs were implanted cardiac pacemakers without pacing. Dogs in the HF group underwent right ventricular pacing for 3 weeks at 240 beats/min to induce HF. The dogs in the HF + RSD group received RSD and underwent the same HF-inducing procedure.

RESULTS

The P-wave dispersion was higher in HF dogs than in the control and HF + RSD dogs (19 ± 3.1 ms vs 13 ± 2.3 ms, 15 ± 2.9 ms, P = 0.04). Conduction time within the interatrium was significantly longer in the HF dogs than that in the control and HF + RSD dogs (39 ± 4 ms vs 31 ± 3 ms, 33 ± 4 ms; P = 0.03). Window of vulnerability (WOV) of AF was widened in the HF dogs than in the HF + RSD dogs (37 ± 5 ms vs 14 ± 3 ms; P < 0.01), while AF could not be induced (WOV = 0) in the control dogs during S1 S2 stimulation. The voltage in the threshold for AF inducibility was lower during ganglionated plexi stimulation in the HF dogs than in the control and HF + RSD dogs (1.8 ± 0.6 V vs 2.5 ± 0.6 V, 2.4 ± 0.4 V; P = 0.04).

CONCLUSIONS

RSD could reverse the atrial electrical remodeling and decrease AF inducibility in dogs with pacing-induced HF.

Mapping and ablation of autonomic ganglia in prevention of postoperative atrial fibrillation in coronary surgery: MAAPPAFS atrial fibrillation randomized controlled pilot study

BACKGROUND

Postoperative atrial fibrillation (POAF) remains common after coronary artery bypass grafting (CABG). Limited efforts to intervene on cardiac autonomic ganglionic plexi (AGP) during surgery show mixed results. In this pilot study, we evaluated the safety and feasibility of map-guided ablation of AGPs during isolated CABG in the prevention of POAF.

METHODS

In this pilot study, patients undergoing isolated CABG were randomized into an intervention group (mapping and ablation of AGP [AGP+] group), and a control group (no mapping and ablation [AGP-] group). Using high-frequency stimulation, active AGPs were identified and ablated intraoperatively using radiofrequency. Continuous rhythm monitoring, serum electrolytes, postoperative medications, and postoperative complications were recorded until discharge.

RESULTS

Randomization of 47 patients (24 AGP+ and 23 AGP-) resulted in similar baseline characteristics, past medical history, and preoperative medication use. The intervention added a median of 14 minutes to the operative time. The incidence of POAF, mean time in POAF, and median length of stay in hospital were: AGP+ 21% vs AGP- 30%; AGP+ 298 minutes vs AGP- 514 minutes; AGP+ 5 days vs AGP- 6 days; respectively). Postoperative complications, medication use, and daily serum electrolyte profiles were similar in both groups.

CONCLUSIONS

This pilot study demonstrated the safety and feasibility of mapping and ablation of AGP during CABG with minimal added operative time. Results further suggest a potentially clinically significant effect on POAF. A multicentre trial is warranted.

Effects of low-level autonomic stimulation on prevention of atrial fibrillation induced by acute electrical remodeling

Background. Rapid atrial pacing (RAP) can induce electrical and autonomic remodeling and facilitate atrial fibrillation (AF). Recent reports showed that low-level vagosympathetic nerve stimulation (LLVNS) can suppress AF, as an antiarrhythmic effect. We hypothesized that LLVNS can reverse substrate heterogeneity induced by RAP. Methods and Results. Mongrel dogs were divided into (LLVNS+RAP) and RAP groups. Electrode catheters were sutured to multiple atrial sites, and LLVNS was applied to cervical vagosympathetic trunks with voltage 50% below the threshold slowing sinus rate by ⩽30 msec. RAP induced a significant decrease in effective refractory period (ERP) and increase in the window of vulnerability at all sites, characterized by descending and elevated gradient differences towards the ganglionic plexi (GP) sites, respectively. The ERP dispersion was obviously enlarged by RAP and more significant when the ERP of GP-related sites was considered. Recovery time from AF was also prolonged significantly as a result of RAP. LLVNS could reverse all these changes induced by RAP and recover the heterogeneous substrate to baseline. Conclusions. LLVNS can reverse the electrical and autonomic remodeling and abolish the GP-central gradient differences induced by RAP, and thus it can recover the homogeneous substrate, which may be the underlying mechanism of its antiarrhythmic effect.