Catheter-based renal sympathetic denervation significantly inhibits atrial fibrillation induced by electrical stimulation of the left stellate ganglion and rapid atrial pacing

Possible organ-protective effects of renal denervation: insights from basic studies

Inappropriate sympathetic nervous activation is the body's response to biological stress and is thought to be involved in the development of various lifestyle-related diseases through an elevation in blood pressure. Experimental studies have shown that surgical renal denervation decreases blood pressure in hypertensive animals. Recently, minimally invasive catheter-based renal denervation has been clinically developed, which results in a reduction in blood pressure in patients with resistant hypertension. Accumulating evidence in basic studies has shown that renal denervation exerts beneficial effects on cardiovascular disease and chronic kidney disease. Interestingly, recent studies have also indicated that renal denervation improves glucose tolerance and inflammatory changes. In this review article, we summarize the evidence from animal studies to provide comprehensive insight into the organ-protective effects of renal denervation beyond changes in blood pressure.

Renal Denervation for Patients With Atrial Fibrillation

PURPOSE OF REVIEW

During the last decade, several case series and small reports have indicated that pulmonary vein isolation (PVI) in combination with renal denervation (RDN) may increase the rate of atrial fibrillation (AF) freedom in patients with hypertension. We aimed to provide a contemporary systematic overview on the techniques, and the efficacy/safety of RDN on AF recurrence, and the current landscape of ongoing investigation.

RECENT FINDINGS

The recent Evaluate Renal Denervation in Addition to Catheter Ablation to Eliminate Atrial Fibrillation (ERADICATE-AF) trial has demonstrated convincingly that among patients with paroxysmal AF and poorly controlled (but not "resistant") hypertension, RDN added to catheter ablation, compared with catheter ablation alone, significantly increased the likelihood of freedom from AF at 12 months. RDN has proven to be a unique, effective and safe interventional therapy for the management of AF. Future investigation will likely focus on confirming current findings; expanding the population of eligible patients (eg., non-hypertensives, well controlled hypertensives); determining long-term maintenance of effect and therapeutics.

Neuroscientific therapies for atrial fibrillation

The cardiac autonomic nervous system (ANS) plays an integral role in normal cardiac physiology as well as in disease states that cause cardiac arrhythmias. The cardiac ANS, comprised of a complex neural hierarchy in a nested series of interacting feedback loops, regulates atrial electrophysiology and is itself susceptible to remodelling by atrial rhythm. In light of the challenges of treating atrial fibrillation (AF) with conventional pharmacologic and myoablative techniques, increasingly interest has begun to focus on targeting the cardiac neuraxis for AF. Strong evidence from animal models and clinical patients demonstrates that parasympathetic and sympathetic activity within this neuraxis may trigger AF, and the ANS may either induce atrial remodelling or undergo remodelling itself to serve as a substrate for AF. Multiple nexus points within the cardiac neuraxis are therapeutic targets, and neuroablative and neuromodulatory therapies for AF include ganglionated plexus ablation, epicardial botulinum toxin injection, vagal nerve (tragus) stimulation, renal denervation, stellate ganglion block/resection, baroreceptor activation therapy, and spinal cord stimulation. Pre-clinical and clinical studies on these modalities have had promising results and are reviewed here.

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

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

SK4 calcium-activated potassium channels activated by sympathetic nerves enhances atrial fibrillation vulnerability in a canine model of acute stroke

Background

New-onset atrial fibrillation (AF) is common in patients with acute stroke (AS). Studies have shown that intermediate-conductance calcium-activated potassium channel channels (SK4) play an important role in cardiomyocyte automaticity. The aim of this study was to investigate the effects of SK4 on AF vulnerability in dogs with AS.

Experimental

Eighteen dogs were randomly divided into a control group, AS group and left stellate ganglion ablation (LSGA) group. In the control group, dogs received craniotomy without right middle cerebral artery occlusion (MCAO). AS dogs were established using a cerebral ischemic model with right MCAO. LSGA dogs underwent MCAO, and LSGA was performed.

Results

Three days later, the dispersion of the effective refractory period (dERP) and AF vulnerability in the AS group were significantly increased compared with those in the control group and LSGA group. However, no significant difference in dERP and AF vulnerability was found between the control group and the LSGA group. The SK4 inhibitor (TRAM-34) completely inhibited the inducibility of AF in AS dogs. SK4 expression and levels of noradrenaline (NE), β1-AR, p38 and c-Fos in the atrium were higher in the AS dogs than in the control group or LSGA group. However, no significant difference in SK4 expression or levels of NE, β1-AR, p38 and c-Fos in the left atrium was observed between the control group and LSGA group.

Conclusion

SK4 plays a key role in AF vulnerability in a canine model with AS. The effects of LSGA on AF vulnerability were associated with the p38 signaling pathways.

Synergy of pulmonary vein isolation and catheter renal denervation in atrial fibrillation complicated with uncontrolled hypertension: Mapping the renal sympathetic nerve and pulmonary vein (the pulmonary vein isolation plus renal denervation strategy)?

INTRODUCTION

Disturbance of sympathetic and vagal nervous system participates in the pathogenesis of hypertension and atrial fibrillation (AF). Renal denervation (RDN) can modulate autonomic nervous activity and reduce blood pressure (BP) in hypertensive patients. We aimed to evaluate the effect of RDN combined with pulmonary vein isolation (PVI) in patients with AF and hypertension.

METHODS

Clinical trials including randomized data comparing PVI plus RDN vs PVI alone were enrolled. Primary outcome was incidence of AF recurrence after procedure.

RESULTS

A total of 387 patients, of them 252 were randomized and were enrolled. Mean age was 57 ± 10 years, 71% were male, and mean left ventricular ejection fraction was 57.4% ± 6.9%. Follow-up for randomized data was 12 months. Overall comparison for primary outcome showed that PVI + RDN was associated with significantly lower AF recurrence as compared with PVI alone (35.8% vs 55.4%, P < 0.0001). This advantageous effect was consistently maintained among randomized patients (37.3% vs 61.9%, odds ratio = 0.37, P = 0.0001), and among patients with implanted devices for detection of AF recurrence (38.9% vs 61.6%, P = 0.007). Post-hoc sensitivity and regression analysis demonstrated very good stability of this primary result. Pooled Kaplan-Meier analysis further showed that PVI + RDN was associated with significantly higher freedom from AF recurrence as compared with PVI alone (log-rank test, P = 0.001). Besides, RDN resulted in significant BP reduction without additionally increasing the risk of adverse events.

CONCLUSIONS

RDN may provide synergetic effects with PVI to reduce the burden of AF and improve BP control in patients with AF and uncontrolled hypertension.

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

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

Atrial fibrillation reduction by renal sympathetic denervation: 12 months' results of the AFFORD study

Aim

The purpose of this pilot study was to assess whether renal sympathetic denervation (RDN) decreases atrial fibrillation (AF) burden in hypertensive patients with symptomatic AF at 6- and 12-month follow-up, as measured using an implantable cardiac monitor (ICM).

Methods and results

A total of 20 patients with symptomatic paroxysmal or persistent AF (EHRA ≥ II) and primary hypertension with a mean office systolic blood pressure (BP) of > 140 mmHg were enrolled. After enrolment, an ICM was implanted 3 months pre-RDN to monitor AF burden. Quality of life (QOL) was assessed using the Atrial Fibrillation Effect on QualiTy-of-life (AFEQT) questionnaire. Mean age was 64 ± 7 years and 55% were females. AF burden in min/day decreased from a median (IQR) of 1.39 (0–11) pre-RDN to 0.67 (0–31.6) at 6 months (p = 0.64) and to 0.94 (0–6.0) at 12 months (pre-RDN vs. 12 months; p = 0.03). QOL improved significantly at both 6 months (+ 11 ± 15 points, p = 0.006) and 12 months (+ 10 ± 19, p = 0.04) as compared to pre-RDN. Office BP decreased significantly at 12-month follow-up (− 20 ± 19/− 7 ± 10 mmHg), p < 0.01) as compared to pre-RDN. Ambulatory BP decreased − 7 ± 16/− 3 ± 9 mmHg (p > 0.05) at 12-month follow-up as compared to pre-RDN.

Conclusion

This pilot study suggests that RDN might be able to decrease AF burden in min/day as measured using an ICM, with a positive effect on QOL. Large-scale randomized trials are needed to prove the definite value of RDN in hypertensive patients with atrial fibrillation.

Electronic supplementary material

The online version of this article (10.1007/s00392-018-1391-3) contains supplementary material, which is available to authorized users.

Comparison between renal denervation and metoprolol on the susceptibility of ventricular arrhythmias in rats with myocardial infarction

Ventricular arrhythmias (VAs) are the leading cause of sudden cardiac death in patients with myocardial infarction (MI). We sought to compare effects of renal denervation (RDN) and metoprolol on VAs after MI. Fifty-four male Sprague-Dawley rats underwent ligation of left anterior descending coronary artery to induce MI, while 6 rats served as Control. Metoprolol was given 20 mg/kg/day for 5 weeks after MI surgery. RDN/Sham-RDN procedure was performed at 1 week after MI. At 5 weeks after MI, electrical programmed stimulation (EPS) was performed in all groups for evaluation of VAs. After EPS, heart and kidneys were harvested. Compared with MI group, RDN and metoprolol significantly decreased the incidence of VAs, and RDN is superior to metoprolol. Compared with metoprolol group, Masson staining showed that RDN significantly reduced the myocardial fibrosis. Both RDN and metoprolol decreased the protein expression of connexin43 (Cx43) compared with MI group, while only RDN lighted this decrease remarkably. Immunohistochemical staining of Tyrosine hydroxylase (TH) and growth associated protein 43 (GAP43) revealed that RDN and metoprolol had similar effect on reducing densities of sympathetic nerve in infarction border zone. According to this study, RDN is more effective in reducing VAs than metoprolol in ischemic cardiomyopathy model.

Modulation of renal sympathetic innervation: recent insights beyond blood pressure control

Renal afferent and efferent sympathetic nerves are involved in the regulation of blood pressure and have a pathophysiological role in hypertension. Additionally, several conditions that frequently coexist with hypertension, such as heart failure, obstructive sleep apnea, atrial fibrillation, renal dysfunction, and metabolic syndrome, demonstrate enhanced sympathetic activity. Renal denervation (RDN) is an approach to reduce renal and whole body sympathetic activation. Experimental models indicate that RDN has the potential to lower blood pressure and prevent cardio-renal remodeling in chronic diseases associated with enhanced sympathetic activation. Studies have shown that RDN can reduce blood pressure in drug-naïve hypertensive patients and in hypertensive patients under drug treatment. Beyond its effects on blood pressure, sympathetic modulation by RDN has been shown to have profound effects on cardiac electrophysiology and cardiac arrhythmogenesis. RDN can display anti-arrhythmic effects in a variety of animal models for atrial fibrillation and ventricular arrhythmias. The first non-randomized studies demonstrate that RDN may promote the maintenance of sinus rhythm following catheter ablation in patients with atrial fibrillation. Registry data point towards a beneficial effect of RDN to prevent ventricular arrhythmias in patients with heart failure and electrical storm. Further large randomized placebo-controlled trials are needed to confirm the antihypertensive and anti-arrhythmic effects of RDN. Here, we will review the current literature on anti-arrhythmic effects of RDN with the focus on atrial fibrillation and ventricular arrhythmias. We will discuss new insights from preclinical and clinical mechanistic studies and possible clinical implications of RDN.

Renal Denervation: Paradise Lost? Paradise Regained?

Renal denervation is a relatively recent concept whose initial promising results suffered a setback following the SYMPLICITY 3 trial, which did not show a significant blood pressure-lowering effect in comparison to sham. In this review article, we begin with the history including the physiological basis behind the concept of renal denervation. Furthermore, we review the literature in support of renal denervation, including the recently published SPYRAL HTN-OFF MED, which demonstrated significant blood pressure reduction in the absence of antihypertensive medication. We further touch upon the potential pitfalls and possible future directions of renal denervation.

Hypertension and Atrial Fibrillation: An Intimate Association of Epidemiology, Pathophysiology, and Outcomes

Atrial fibrillation (AF) is the most prevalent sustained arrhythmia found in clinical practice. AF rarely exists as a single entity but rather as part of a diverse clinical spectrum of cardiovascular diseases, related to structural and electrical remodeling within the left atrium, leading to AF onset, perpetuation, and progression. Due to the high overall prevalence within the AF population arterial hypertension plays a significant role in the pathogenesis of AF and its complications. Fibroblast proliferation, apoptosis of cardiomyocytes, gap junction remodeling, accumulation of collagen both in atrial and ventricular myocardium all accompany ageing-related structural remodeling with impact on electrical activity. The presence of hypertension also stimulates oxidative stress, systemic inflammation, rennin-angiotensin-aldosterone and sympathetic activation, which further drives the remodeling process in AF. Importantly, both hypertension and AF independently increase the risk of cardiovascular and cerebrovascular events, e.g., stroke and myocardial infarction. Given that both AF and hypertension often present with limited on patient wellbeing, treatment may be delayed resulting in development of complications as the first clinical manifestation of the disease. Antithrombotic prevention in AF combined with strict blood pressure control is of primary importance, since stroke risk and bleeding risk are both greater with underlying hypertension.

Impacts of Renal Sympathetic Activation on Atrial Fibrillation: The Potential Role of the Autonomic Cross Talk Between Kidney and Heart

Background

Recent studies have demonstrated that there is a high variability of renal sympathetic nerve density distribution from proximal to distal renal artery segments. The aim of our study was to investigate the roles of renal sympathetic nerve stimulation (RSS) on atrial fibrillation and cardiac autonomic nervous activity.

Methods and Results

Twenty‐eight dogs were randomly assigned to the proximal RSS group (P‐RSS, N=7), middle RSS group (M‐RSS, N=7), distal RSS group (D‐RSS, N=7), and the control group (sham RSS, N=7). RSS was performed using electrical stimulation on the bilateral renal arteries for 3 hours. Effective refractory period and the window of vulnerability were measured at atrial and pulmonary veins sites. Superior left ganglionated plexi (SLGP) and left stellate ganglion (LSG) function and neural activity were determined. C‐fos and nerve growth factor protein expression in the SLGP and LSG were examined. Only P‐RSS (1) caused pronounced blood pressure rises, induced a significant decrease in effective refractory period, and generated a marked increase in cumulative window of vulnerability and effective refractory period dispersion; (2) increased the frequency and amplitude of the neural activity in the SLGP and LSG; (3) increased SLGP and LSG function; and (4) upregulated the level of c‐fos and nerve growth factor expression in the SLGP and LSG.

Conclusions

This study demonstrated that renal sympathetic nerve activation induced by 3 hours of P‐RSS facilitated atrial fibrillation inducibility by upregulating cardiac autonomic nervous activity, suggesting a potential autonomic cross talk between kidney and heart.

Atrial Fibrillation: The Science behind Its Defiance

Atrial fibrillation (AF) is the most prevalent arrhythmia in the world, due both to its tenacious treatment resistance, and to the tremendous number of risk factors that set the stage for the atria to fibrillate. Cardiopulmonary, behavioral, and psychological risk factors generate electrical and structural alterations of the atria that promote reentry and wavebreak. These culminate in fibrillation once atrial ectopic beats set the arrhythmia process in motion. There is growing evidence that chronic stress can physically alter the emotion centers of the limbic system, changing their input to the hypothalamic-limbic-autonomic network that regulates autonomic outflow. This leads to imbalance of the parasympathetic and sympathetic nervous systems, most often in favor of sympathetic overactivation. Autonomic imbalance acts as a driving force behind the atrial ectopy and reentry that promote AF. Careful study of AF pathophysiology can illuminate the means that enable AF to elude both pharmacological control and surgical cure, by revealing ways in which antiarrhythmic drugs and surgical and ablation procedures may paradoxically promote fibrillation. Understanding AF pathophysiology can also help clarify the mechanisms by which emerging modalities aiming to correct autonomic imbalance, such as renal sympathetic denervation, may offer potential to better control this arrhythmia. Finally, growing evidence supports lifestyle modification approaches as adjuncts to improve AF control.

Renal sympathetic denervation for treatment of patients with atrial fibrillation: Reappraisal of the available evidence

Afferent renal sympathetic nerve signaling regulates central sympathetic outflow. In this regard, renal sympathetic denervation has emerged as a novel interventional strategy for treatment of patients with resistant hypertension. Despite the disappointing results of the Simplicity HTN-3 randomized controlled trial, promoters of renal denervation argue that the negative results were due to ineffective denervation technique and poor patient selection. Yet, long-term "pathologic" increase of efferent sympathetic nerve activity is observed in many chronic disease states characterized by sympathetic overactivity, such as arrhythmia, heart failure, insulin resistance, and chronic kidney disease. In this review, we highlight the contemporary evidence on the safety/efficacy of renal denervation in the treatment of patients with atrial fibrillation.

Renal sympathetic denervation in therapy resistant hypertension - pathophysiological aspects and predictors for treatment success

Many forms of human hypertension are associated with an increased systemic sympathetic activity. Especially the renal sympathetic nervous system has been found to play a prominent role in this context. Therefore, catheter-interventional renal sympathetic denervation (RDN) has been established as a treatment for patients suffering from therapy resistant hypertension in the past decade. The initial enthusiasm for this treatment was markedly dampened by the results of the Symplicity-HTN-3 trial, although the transferability of the results into clinical practice to date appears to be questionable. In contrast to the extensive use of RDN in treating hypertensive patients within or without clinical trial settings over the past years, its effects on the complex pathophysiological mechanisms underlying therapy resistant hypertension are only partly understood and are part of ongoing research. Effects of RDN have been described on many levels in human trials: From altered systemic sympathetic activity across cardiac and metabolic alterations down to changes in renal function. Most of these changes could sustainably change long-term morbidity and mortality of the treated patients, even if blood pressure remains unchanged. Furthermore, a number of promising predictors for a successful treatment with RDN have been identified recently and further trials are ongoing. This will certainly help to improve the preselection of potential candidates for RDN and thereby optimize treatment outcomes. This review summarizes important pathophysiologic effects of renal denervation and illustrates the currently known predictors for therapy success.

Efficacy and Safety of Renal Sympathetic Denervation on Dogs with Pressure Overload-Induced Heart Failure

BACKGROUND

In dogs with heart failure (HF) induced by overload pressure, the role of renal sympathetic denervation (RSD) on heart failure and in the renal artery is unclear. Therefore, we investigated the efficacy and safety of RSD in dogs with pressure overload-induced heart failure.

METHODS

Twenty mongrel dogs were divided into a sham-operated group, an HF group and an HF + RSD group. In the sham-operated group, the abdominal aorta was located but was not constricted, in the HF group, the abdominal aorta was constricted without RSD, and the HF+RSD group underwent RSD with constriction of the abdominal aorta after 10 weeks. Blood sampling assays, echocardiography, intravascular ultrasound (IVUS) measurement and histopathological examination were performed.

RESULTS

Renal sympathetic denervation caused a significant reduction in the levels of noradrenaline (166.62±6.84 vs. 183.48±13.66 pg/ml, P<0.05), plasma renin activity (1.93±0.12 vs. 2.10±0.13 ng/mlh, P<0.05) and B-type natriuretic peptide (71.14±3.86 vs. 83.15±5.73 pg/ml, P<0.05) at eight weeks after RSD in the HF+RSD group. Compared with the HF group at eight weeks, the left ventricular internal dimension at end-diastole and end-systole were lower and the left ventricular ejection fraction was higher (all P<0.05) at eight weeks after RSD in the HF+RSD group. Intravenous ultrasound images showed no changes in the renal artery lumen, and intimal hyperplasia and vascular lumen stenosis were not observed after RSD.

CONCLUSIONS

Renal sympathetic denervation could improve cardiac function in dogs with HF induced by pressure overload; RSD had no adverse influence on the renal artery.

The effects of renal denervation on resistant hypertension patients: a meta-analysis

We carried out this meta-analysis to assess the effects of renal denervation (RDN) on resistant hypertension patients. According to the collaborative review group search strategy, we searched MEDLINE (1996 to 2015.10); EBCO (1996 to 2015.10) and CNKI. A meta-analysis was carried out using RevMan 5.0. We identified 11 reports that fulfilled the inclusion criteria for our review. Controlled trials reporting systolic blood pressure (SBP), diastolic blood pressure in RDN, and control groups at the 6-month follow-up in patients with resistant hypertension were systematically reviewed. Pooled analysis of all 11 included studies showed significant reductions in SBP (weighted mean difference -13.9 mmHg, 95% confidence interval -21.17 to -6.63, P=0.00025, I=93%) and diastolic blood pressure (weighted mean difference -4.41 mmHg, 95% confidence interval -6.95 to -1.88, P=0.004, I=90%) compared with the control group at the 6-month follow-up. Six controlled trials reported specific values of ambulatory SBP that showed no significant difference between two groups. It has also been found that RDN has benefits in protecting cardiac and renal function compared with the control group without increasing adverse events. In conclusion, this meta-analysis shows that RDN is superior to the control group in lowering office blood pressure rather than ambulatory SBP, and might have other potential benefits to protect heart and renal function.

Treatment of Atrial and Ventricular Arrhythmias Through Autonomic Modulation

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

Renal sympathetic denervation suppresses atrial fibrillation induced by acute atrial ischemia/infarction through inhibition of cardiac sympathetic activity

OBJECTIVE

This study aims to explore the effects of renal sympathetic denervation (RSD) on atrial fibrillation (AF) inducibility and sympathetic activity induced by acute atrial ischemia/infarction.

METHODS

Acute ischemia/infarction was induced in 12 beagle dogs by ligating coronary arteries that supply the atria. Six dogs in the sham-RSD group did not undergo RSD, and six dogs without coronary artery ligation served as controls. AF induction rate, sympathetic discharge, catecholamine concentration and densities of tyrosine hydroxylase-positive nerves were measured.

RESULTS

Acute atrial ischemia/infarction resulted in a significant increase of AF induction rate, which was decreased by RSD compared to controls (P<0.05). The root-mean-square peak value, peak area and number of sympathetic discharges were significantly augmented by atrial ischemia relative to the baseline and control (P<0.05). The number of sympathetic discharges was significantly reduced in the RSD group, compared to the control and sham-RSD groups (P<0.05). Norepinephrine and epinephrine concentrations in the atria, ventricle and kidney were elevated by atrial ischemia/infarction, but were reduced by RSD (P<0.05).

CONCLUSIONS

Sympathetic hyperactivity was associated with pacing-induced AF after acute atrial ischemia/infarction. RSD has the potential to reduce the incidence of new-onset AF after acute atrial ischemia/infarction. The inhibition of cardiac sympathetic activity by RSD may be one of the major underlying mechanisms for the marked reduction of AF inducibility.

Effects of Intrinsic and Extrinsic Cardiac Nerves on Atrial Arrhythmia in Experimental Pulmonary Artery Hypertension

Atrial arrhythmia, which includes atrial fibrillation (AF) and atrial flutter (AFL), is common in patients with pulmonary arterial hypertension (PAH), who often have increased sympathetic nerve activity. Here, we tested the hypothesis that autonomic nerves play important roles in vulnerability to AF/AFL in PAH. The atrial effective refractory period and AF/AFL inducibility at baseline and after anterior right ganglionated plexi ablation were determined during left stellate ganglion stimulation or left renal sympathetic nerve stimulation in beagle dogs with or without PAH. Then, sympathetic nerve, β-adrenergic receptor densities and connexin 43 expression in atrial tissues were assessed. The sum of the window of vulnerability to AF/AFL was increased in the right atrium compared with the left atrium at baseline in the PAH dogs but not in the controls. The atrial effective refractory period dispersion was increased in the control dogs, but not in the PAH dogs, during left stellate ganglion stimulation. The voltage thresholds for inducing AF/AFL during anterior right ganglionated plexi stimulation were lower in the PAH dogs than in the controls. The AF/AFL inducibility was suppressed after ablation of the anterior right ganglionated plexi in the PAH dogs. The PAH dogs had higher sympathetic nerve and β1-adrenergic receptor densities, increased levels of nonphosphorylated connexin 43, and heterogeneous connexin 43 expression in the right atrium when compared with the control dogs. The anterior right ganglionated plexi play important roles in the induction of AF/AFL. AF/AFL induction was associated with right atrium substrate remodeling in dogs with PAH.

Renal denervation suppresses atrial fibrillation in a model of renal impairment

Background

A close association exists between renal impairment (RI) and atrial fibrillation (AF) occurrence. Increased activity of the sympathetic nervous system (SNS) may contribute to the development of AF associated with RI. Renal denervation (RDN) decreases central sympathetic activity.

Objective

The main objective of the study was to explore the effects of RDN on AF occurrence and its possible mechanisms in beagles with RI.

Methods

Unilateral RI was induced in beagles by embolization of small branches of the renal artery in the right kidney using gelatin sponge granules in Model (n = 6) and RDN group (n = 6). The Sham group (n = 6) underwent the same procedure, except for embolization. Then animals in RDN group underwent radiofrequency ablation of the renal sympathetic nerve. Cardiac electrophysiological parameters, blood pressure, left ventricular end-diastolic pressure, and AF inducibility were investigated. The activity of the SNS, renin-angiotensin-aldosterone system (RAAS), inflammation and atrial interstitial fibrosis were measured.

Results

Embolization of small branches of the renal artery in the right kidney led to ischemic RI. Heart rate, P wave duration and BP were increased by RI, which were prevented or attenuated by RDN. Atrial effective refractory period was shortened and AF inducibility was increased by RI, which were prevented by RDN. Antegrade Wenckebach point was shortened, atrial and ventricular rates during AF were increased by RI, which were attenuated or prevented by RDN. Levels of norepinephrine, renin and aldosterone in plasma, norepinephrine, angiotensin II, aldosterone, interleukin-6 and high sensitivity C-reactive protein in atrial tissue were elevated, and atrial interstitial fibrosis was enhanced by RI, which were attenuated by RDN.

Conclusions

RDN significantly reduced AF inducibility, prevented the atrial electrophysiological changes in a model of RI by combined reduction of sympathetic drive and RAAS activity, and inhibition of inflammation activity and fibrotic pathway in atrial tissue.

Renal denervation--hypes and hopes

Catheter-based renal denervation (RDN) is a novel invasive approach in the treatment of resistant hypertension. It is considered a minimally invasive and safe procedure which, as shown by initial experimental and clinical trials, is able not only to reduce blood pressure but also to modify its risk factors by modulation of autonomic nervous system. Recently published results of a randomized Symplicity HTN-3 trial, which failed to demonstrate RDN-induced reduction of blood pressure at six months, decreased the initial enthusiasm regarding RDN and raised a question about real efficacy of this procedure. Nevertheless, still there are some other conditions characterized by increased sympathetic tone such as heart failure, atrial fibrillation, or ventricular arrhythmias that may benefit from RDN. Furthermore, novel therapeutical approach toward RDN using adapted electrophysiological or new specially designed electrodes may improve effectiveness of RDN procedure.

Renal denervation

PURPOSE OF REVIEW

Renal denervation (RDN) has, within recent years, been suggested as a novel treatment option for patients with resistant hypertension. This review summarizes the current knowledge on this procedure as well as limitations and questions that remain to be answered.

RECENT FINDINGS

The Symplicity HTN-1 (2009) and HTN-2 (2010) studies re-introduced an old treatment approach for resistant hypertension and showed that catheter-based RDN was feasible and resulted in substantial blood pressure (BP) reductions. However, they also raised questions of durability of BP reduction, correct patient selection, anatomical and physiological effects of RDN as well as possible beneficial effects on other diseases with increased sympathetic activity. The long awaited Symplicity HTN-3 (2014) results illustrated that the RDN group and the sham-group had similar reductions in BP.

SUMMARY

Initial studies demonstrated that RDN in patients with resistant hypertension was both feasible and safe and indicated that RDN may lead to impressive reductions in BP. However, recent controlled studies question the BP lowering effect of RDN treatment. Large-scale registry data still supports the favorable BP reducing effect of RDN. We suggest that, in the near future, RDN should not be performed outside clinical studies. The degree of denervation between individual operators and between different catheters and techniques used should be clarified. The major challenge ahead is to identify which patients could benefit from RDN, to clarify the lack of an immediate procedural success parameter, and to establish further documentation of overall effect of treatment such as long-term cardiovascular morbidity and mortality.

Remodeling of stellate ganglion neurons after spatially targeted myocardial infarction: Neuropeptide and morphologic changes

BACKGROUND

Myocardial infarction (MI) induces remodeling in stellate ganglion neurons (SGNs).

OBJECTIVE

We investigated whether infarct site has any impact on the laterality of morphologic changes or neuropeptide expression in stellate ganglia.

METHODS

Yorkshire pigs underwent left circumflex coronary artery (LCX; n = 6) or right coronary artery (RCA; n = 6) occlusion to create left- and right-sided MI, respectively (control: n = 10). At 5 ± 1 weeks after MI, left and right stellate ganglia (LSG and RSG, respectively) were collected to determine neuronal size, as well as tyrosine hydroxylase (TH) and neuropeptide Y immunoreactivity.

RESULTS

Compared with control, LCX and RCA MIs increased mean neuronal size in the LSG (451 ± 25 vs 650 ± 34 vs 577 ± 55 μm(2), respectively; P = .0012) and RSG (433 ± 22 vs 646 ± 42 vs 530 ± 41 μm(2), respectively; P = .002). TH immunoreactivity was present in the majority of SGNs. Both LCX and RCA MIs were associated with significant decreases in the percentage of TH-negative SGNs, from 2.58% ± 0.2% in controls to 1.26% ± 0.3% and 0.7% ± 0.3% in animals with LCX and RCA MI, respectively, for LSG (P = .001) and from 3.02% ± 0.4% in controls to 1.36% ± 0.3% and 0.68% ± 0.2% in LCX and RCA MI, respectively, for RSG (P = .002). Both TH-negative and TH-positive neurons increased in size after LCX and RCA MI. Neuropeptide Y immunoreactivity was also increased significantly by LCX and RCA MI in both ganglia.

CONCLUSION

Left- and right-sided MIs equally induced morphologic and neurochemical changes in LSG and RSG neurons, independent of infarct site. These data indicate that afferent signals transduced after MI result in bilateral changes and provide a rationale for bilateral interventions targeting the sympathetic chain for arrhythmia modulation.

Reverse cardiac remodeling after renal denervation: Atrial electrophysiologic and structural changes associated with blood pressure lowering

BACKGROUND

Hypertension is the most common modifiable risk factor associated with atrial fibrillation.

OBJECTIVE

The purpose of this study was to determine the effects of blood pressure (BP) lowering after renal denervation on atrial electrophysiologic and structural remodeling in humans.

METHODS

Fourteen patients (mean age 64 ± 9 years, duration of hypertension 16 ± 11 years, on 5 ± 2 antihypertensive medications) with treatment-resistant hypertension underwent baseline 24-hour ambulatory BP monitoring, echocardiography, cardiac magnetic resonance imaging, and electrophysiologic study. Electrophysiologic study included measurements of P-wave duration, effective refractory periods, and conduction times. Electroanatomic mapping of the right atrium was completed using CARTO3 to determine local and regional conduction velocity and tissue voltage. Bilateral renal denervation was performed, and all measurements repeated after 6 months.

RESULTS

After renal denervation, mean 24-hour BP reduced from 152/84 mm Hg to 141/80 mm Hg at 6-month follow-up (P < .01). Global conduction velocity increased significantly (0.98 ± 0.13 m/s to 1.2 ± 0.16 m/s at 6 months, P < .01), conduction time shortened (32 ± 5 ms to 27 ± 6 ms, P < .01), and complex fractionated activity was reduced (37% ± 14% to 19% ± 12%, P = .02). Changes in conduction velocity correlated positively with changes in 24-hour mean systolic BP (R(2) = 0.55, P = .01). There was a significant reduction in left ventricular mass (139 ± 37 g to 120 ± 29 g, P < .01) and diffuse ventricular fibrosis (T1 partition coefficient 0.39 ± 0.07 to 0.31 ± 0.09, P = .01) on cardiac magnetic resonance imaging.

CONCLUSION

BP reduction after renal denervation is associated with improvements in regional and global atrial conduction and reductions in ventricular mass and fibrosis. Whether changes in electrical and structural remodeling are solely due to BP lowering or are due in part to intrinsic effects of renal denervation remains to be determined.

Renal sympathetic denervation for treatment of ventricular arrhythmias: a review on current experimental and clinical findings

Ventricular arrhythmias (VAs) remain the major cause of mortality and sudden cardiac death (SCD) in almost all forms of heart disease. Despite so many therapeutic advances, such as pharmacological therapies, catheter ablation, and arrhythmia surgery, management of VAs remains a great challenge for cardiologists. Evidence from histological studies and from direct nerve activity recordings have suggested that increased sympathetic nerve density and activity contribute to the generation of VAs and SCD. It is well known that renal sympathetic nerve (RSN), either afferent component or efferent component, plays an important role in modulation of central sympathetic activity. We have recently shown that RSN activation by electrical stimulation significantly increases cardiac and systemic sympathetic activity and promotes the incidence of acute ischemia-induced VAs, suggesting RSN has a role in the development of VAs. Initial experience of RSN denervation (RDN) in patients with resistant hypertension showed that this novel and minimally invasive device-based approach significantly reduced not only kidney but also whole-body norepinephrine spillover. In addition, experimental studies find that left stellate ganglion nerve activity is significantly decreased after RDN. Based on these observations, it is reasonable to conclude that RDN may be an effective therapy for the management of VAs. Indeed, RDN has provided a protection against VAs in both animal models and patients. In this article, we review the role of the RSN in the generation of VAs and SCD and the role of RDN as a potential treatment strategy for VAs and SCD.

Renal denervation decreases effective refractory period but not inducibility of ventricular fibrillation in a healthy porcine biomodel: a case control study

BACKGROUND

Ventricular arrhythmias play an important role in cardiovascular mortality especially in patients with impaired cardiac and autonomic function. The aim of this experimental study was to determine, if renal denervation (RDN) could decrease the inducibility of ventricular fibrillation (VF) in a healthy porcine biomodel.

METHODS

Controlled electrophysiological study was performed in 6 biomodels 40 days after RDN (RDN group) and in 6 healthy animals (control group). The inducibility of VF was tested by programmed ventricular stimulation from the apex of right ventricle (8 basal stimuli coupled with up to 4 extrastimuli) always three times in each biomodel using peripheral extracorporeal oxygenation for hemodynamic support. Further, basal heart rate (HR), PQ and QT intervals and effective refractory period of ventricles (ERP) were measured. Technical success of RDN was evaluated by histological examination.

RESULTS

According to histological findings, RDN procedure was successfully performed in all biomodels. Comparing the groups, basal HR was lower in RDN group: 79 (IQR 58; 88) vs. 93 (72; 95) beats per minute (p = 0.003); PQ interval was longer in RDN group: 145 (133; 153) vs. 115 (113; 120) ms (p < 0.0001) and QTc intervals were comparable: 402 (382; 422) ms in RDN vs. 386 (356; 437) ms in control group (p = 0.1). ERP was prolonged significantly in RDN group: 159 (150; 169) vs. 140 (133; 150) ms (p = 0.001), but VF inducibility was the same (18/18 vs. 18/18 attempts).

CONCLUSIONS

RDN decreased the influence of sympathetic nerve system on the heart conduction system in healthy porcine biomodel. However, the electrophysiological study was not associated with a decrease of VF inducibility after RDN.

Renal Denervation And Pulmonary Vein Isolation In Patients With Drug Resistant Hypertension And Symptomatic Atrial Fibrillation

Systemic hypertension is the most consistent modifiable risk factor for atrial fibrillation (AF) in adults with consistent data from both animal models and human studies suggesting a consistent pattern of autonomic imbalance underlying both conditions. Relative sympathetic nervous system activation is a demonstrably common attendant to the local mechanisms in pulmonary veins that sustain persistent or recurrent AF and may represent a new objective for adjunctive treatment. Established management of AF aims to achieve durable control through either pharmacologic or catheter-based interventions. The introduction of catheter-based renal denervation as a safe, alternate approach to target the sympathetic nervous system therapeutically represents a potential opportunity to treat the shared pathophysiological mechanisms with minimal additional treatment burden when added in this context. Preliminary investigations have demonstrated both proof-of-concept and the technical feasibility of combined renal denervation and AF ablation procedures with the suggestion of benefit in terms of freedom from AF recurrence. The available data is promising but absolute confirmation of efficacy remains unconfirmed in the absence of more definitive evidence. This paper reviews the role of autonomic imbalance in the initiation and maintenance of AF by summarizing the observations from both experimental models and clinical studies from the perspective of potential therapeutic overlap between catheter-based treatments.

Vagus nerve stimulation reverses ventricular electrophysiological changes induced by hypersympathetic nerve activity

NEW FINDINGS

What is the central question of this study? Previous studies have shown that hypersympathetic nerve activity results in ventricular electrophysiological changes and facilitates the occurrence of ventricular arrhythmias. Vagus nerve stimulation has shown therapeutic potential for myocardial infarction-induced ventricular arrhythmias. However, the actions of vagus nerve stimulation on hypersympathetic nerve activity-induced ventricular electrophysiological changes are still unknown. What is the main finding and its importance? We show that vagus nerve stimulation is able to reverse hypersympathetic nerve activity-induced ventricular electrophysiological changes and suppress the occurrence of ventricular fibrillation. These findings further suggest that vagus nerve stimulation may be an effective treatment option for ventricular arrhythmias, especially in patients with myocardial infarction or heart failure. Vagus nerve stimulation (VNS) has shown therapeutic potential for myocardial infarction-induced ventricular arrhythmias. This study aimed to investigate the effects of VNS on ventricular electrophysiological changes induced by hypersympathetic nerve activity. Seventeen open-chest dogs were subjected to left stellate ganglion stimulation (LSGS) for 4 h to simulate hypersympathetic tone. All animals were randomly assigned to the VNS group (n = 9) or the control group (n = 8). In the VNS group, VNS was performed at the voltage causing a 10% decrease in heart rate for hours 3-4 during 4 h of LSGS. During the first 2 h of LSGS, the ventricular effective refractory period (ERP) and action potential duration (APD) were both progressively and significantly decreased; the spatial dispersion of ERP, maximal slope of the restitution curve and pacing cycle length of APD alternans were all increased. With LSGS + VNS during the next 2 h, there was a significant return of all the altered electrophysiological parameters towards baseline levels. In the eight control dogs that received 4 h of LSGS without VNS, all the parameters changed progressively, but without any reversals. The ventricular fibrillation threshold was higher in the VNS group than in the control group (17.3 ± 3.4 versus 11.3 ± 3.8 V, P < 0.05). The present study demonstrated that VNS was able to reverse LSGS-induced ventricular electrophysiological changes and suppress the occurrence of ventricular fibrillation.

Establishment of a model of renal impairment with mild renal insufficiency associated with atrial fibrillation in canines

Background

Chronic kidney disease and occurrence of atrial fibrillation (AF) are closely related. No studies have examined whether renal impairment (RI) without severe renal dysfunction is associated with the occurrence of AF.

Methods

Unilateral RI with mild renal insufficiency was induced in beagles by embolization of small branches of the renal artery in the left kidney for 2 weeks using gelatin sponge granules in the model group (n = 5). The sham group (n = 5) underwent the same procedure, except for embolization. Parameters associated with RI and renal function were tested, cardiac electrophysiological parameters, blood pressure, left ventricular pressure, and AF vulnerability were investigated. The activity of the sympathetic nervous system, renin-angiotensin-aldosterone system, inflammation, and oxidative stress were measured. Histological studies associated with atrial interstitial fibrosis were performed.

Results

Embolization of small branches of the renal artery in the left kidney led to ischemic RI with mild renal insufficiency. The following changes occurred after embolization. Heart rate and P wave duration were increased. Blood pressure and left ventricular systolic pressure were elevated. The atrial effective refractory period and antegrade Wenckebach point were shortened. Episodes and duration of AF, as well as atrial and ventricular rate during AF were increased in the model group. Plasma levels of norepinephrine, renin, and aldosterone were increased, angiotensin II and aldosterone levels in atrial tissue were elevated, and atrial interstitial fibrosis was enhanced after 2 weeks of embolization in the model group.

Conclusions

We successfully established a model of RI with mild renal insufficiency in a large animal. We found that RI with mild renal insufficiency was associated with AF in this model.

Renal denervation: effects on atrial electrophysiology and arrhythmias

Atrial fibrillation (AF) is the most common sustained arrhythmia and is associated with significant morbidity and mortality. Currently, atrial endocardial catheter ablation, mainly targeting focal discharges in the pulmonary veins, is the most widely used interventional treatment of drug-refractory AF. Despite technical improvements, results are not yet optimal. There is ongoing search for alternative and/or complementary interventional targets. Conditions associated with increased sympathetic activation such as hypertension, heart failure and sleep apnea lead to structural, neural and electrophysiological changes in the atrium thereby contributing to the progression from paroxysmal to persistent AF and increasing recurrence rate of AF after PVI. Until now, interventional modulation of autonomic nervous system was limited by highly invasive techniques. Catheter-based renal denervation (RDN) was introduced as a minimally invasive approach to reduce renal and whole body sympathetic activation with accompanying blood pressure control and left-ventricular morphological and functional changes in resistant hypertension. This review focuses on the potential atrial antiarrhythmic and antiremodeling effects of RDN in AF patients with hypertension, heart failure, and sleep apnea and discusses the possible role of RDN in the treatment of AF.

The Role of Renal Sympathetic Denervation in Atrial Fibrillation

Endocardial catheter ablation is a widely used alternative for the treatment of atrial fibrillation (AF). Despite technical improvements, and increased understanding of mechanism, and acquired technical experience over many years, the results are not yet optimal. This results in an ongoing search for new therapeutic approaches. Because cardiac sympathetic drive is potentially responsible for triggering and sustaining AF, modulation of sympathetic tone has been proposed as a viable treatment objective. The early attempts to test this concept were limited by nature=highly intrusive techniques but new approaches and targets have been recently introduced. Specifically, renal nerve ablation has been introduced and the first attempts to employ this technique for treatment of cardiac arrhythmias give as a promise of new therapeutic avenues in near future. This review focuses on the possible role of renal denervation in treatment of atrial fibrillation, the contemporary evidence supporting this approach, and the ongoing trials to establish its therapeutic role.