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.

Effects and mechanism of renal denervation on ventricular arrhythmia after acute myocardial infarction in rats

BACKGROUND

Renal denervation (RDN) can reduce ventricular arrhythmia after acute myocardial infarction (AMI), but the mechanism is not clear. The purpose of this study is to study its mechanism.

METHODS

Thirty-two Sprague-Dawley rats were divided into four groups: control group, AMI group, RDN-1d + AMI group, RDN-2w + AMI group. The AMI model was established 1 day after RDN in the RDN-1d + AMI group and 2 weeks after RDN in the RDN-2w + AMI group. At the same time, 8 normal rats were subjected to AMI modelling (the AMI group). The control group consisted of 8 rats without RDN intervention or AMI modelling.

RESULTS

The study confirmed that RDN can reduce the occurrence of ventricular tachycardia in AMI rats, reduce renal sympathetic nerve discharge, and inhibit the activity of local sympathetic nerves and cell growth factor (NGF) protein expression in the heart after AMI. In addition, RDN decreased the expression of norepinephrine (NE) and glutamate in the hypothalamus,and NE in cerebrospinal fluid, and increased the expression level of γ aminobutyric acid (GABA) in the hypothalamus after AMI.

CONCLUSION

RDN can effectively reduce the occurrence of ventricular arrhythmia after AMI, and its main mechanism may be via the inhibition of central sympathetic nerve discharge.

Systematic review of renal denervation for the management of cardiac arrhythmias

Background

In the wake of the controversy surrounding the SYMPLICITY HTN-3 trial and data from subsequent trials, this review aims to perform an updated and more comprehensive review of the impact of renal sympathetic denervation on cardiac arrhythmias.

Methods and results

A systematic search was performed using the Medline, Scopus and Embase databases using the terms “Renal Denervation” AND “Arrhythmias or Atrial or Ventricular”, limited to Human and English language studies within the last 10 years. This search yielded 19 relevant studies (n = 6 randomised controlled trials, n = 13 non-randomised cohort studies) which comprised 783 patients. The studies show RSD is a safe procedure, not associated with increases in complications or mortality post-procedure. Importantly, there is no evidence RSD is associated with a deterioration in renal function, even in patients with chronic kidney disease. RSD with or without adjunctive pulmonary vein isolation (PVI) is associated with improvements in freedom from atrial fibrillation (AF), premature atrial complexes (PACs), ventricular arrhythmias and other echocardiographic parameters. Significant reductions in ambulatory and office blood pressure were also observed in the majority of studies.

Conclusion

This review provides evidence based on original research that ‘second generation’ RSD is safe and is associated with reductions in short-term blood pressure and AF burden. However, the authors cannot draw firm conclusions with regards to less prominent arrhythmia subtypes due to the paucity of evidence available. Large multi-centre RCTs investigating the role of RSD are necessary to comprehensively assess the efficacy of the procedure treating various arrhythmias.

Graphic abstract

Sympatho-adrenergic mechanisms in heart failure: new insights into pathophysiology

The sympathetic nervous system is activated in the setting of heart failure (HF) to compensate for hemodynamic instability. However, acute sympathetic surge or sustained high neuronal firing rates activates β-adrenergic receptor (βAR) signaling contributing to myocardial remodeling, dysfunction and electrical instability. Thus, sympatho-βAR activation is regarded as a hallmark of HF and forms pathophysiological basis for β-blocking therapy. Building upon earlier research findings, studies conducted in the recent decades have significantly advanced our understanding on the sympatho-adrenergic mechanism in HF, which forms the focus of this article. This review notes recent research progress regarding the roles of cardiac β2AR or α1AR in the failing heart, significance of β1AR-autoantibodies, and βAR signaling through G-protein independent signaling pathways. Sympatho-βAR regulation of immune cells or fibroblasts is specifically discussed. On the neuronal aspects, knowledge is assembled on the remodeling of sympathetic nerves of the failing heart, regulation by presynaptic α2AR of NE release, and findings on device-based neuromodulation of the sympathetic nervous system. The review ends with highlighting areas where significant knowledge gaps exist but hold promise for new breakthroughs.

Renal denervation for the treatment of ventricular arrhythmias: A systematic review and meta-analysis

INTRODUCTION

Ventricular arrhythmias (VAs) are a major cause of morbidity and mortality in patients with heart disease. Recent studies evaluated the effect of renal denervation (RDN) on the occurrence of VAs. We conducted a systematic review and meta-analysis to determine the efficacy and safety of this procedure.

METHODS AND RESULTS

A systematic search of the literature was performed to identify studies that evaluated the use of RDN for the management of VAs. Primary outcomes were reduction in the number of VAs and implantable cardioverter-defibrillator (ICD) therapies. Secondary outcomes were changes in blood pressure and renal function. Ten studies (152 patients) were included in the meta-analysis. RDN was associated with a reduction in the number of VAs, antitachycardia pacing, ICD shocks, and overall ICD therapies of 3.53 events/patient/month (95% confidence interval [CI] = -5.48 to -1.57), 2.86 events/patient/month (95% CI = -4.09 to -1.63), 2.04 events/patient/month (95% CI = -2.12 to -1.97), and 2.68 events/patient/month (95% CI = -3.58 to -1.78), respectively. Periprocedural adverse events occurred in 1.23% of patients and no significant changes were seen in blood pressure or renal function.

CONCLUSIONS

In patients with refractory VAs, RDN was associated with a reduction in the number of VAs and ICD therapies, and was shown to be a safe procedure.

Renal sympathetic denervation for the treatment of recurrent ventricular arrhythmias-ELECTRAM investigators

INTRODUCTION

Renal sympathetic denervation (RSDN) is an alternate management approach for refractory ventricular arrhythmias (VAs). We aimed to perform a systematic review of clinical outcomes on the impact of RSDN on refractory VA patients.

METHODS

A systematic search without language restriction, using PubMed, EMBASE, SCOPUS, Google Scholar, and ClinicalTrials.gov from inception to August 18, 2020, was performed for the studies that reported outcomes in patients who underwent RSDN for VA. The outcomes studied were-(1) recurrent VA; and (2) all-cause mortality.

RESULTS

Five studies (from 2014 to 2018) with a total of 51 VA patients met study inclusion criteria. The mean age was 61.92 ± 11.76 years, and 78.4% were men. The pooled incidence of short-term (3 months or less) and long-term (more than 3 months) VA recurrence was 63.85% (95% CI 16.75 to 99.32) and 10.52% (95% CI 0.14 to 28.75), respectively. When stratified by the number of VA episodes, there was a significant reduction in mean VA episodes (SMD -3.79, 95% CI -6.59 to -0.98, p < .01), ICD shocks (SMD -1.71, 95% CI -3.0 to -0.42, p < .01) and anti-tachycardia pacing (SMD -1.21, 95% CI -1.98 to -0.44, p < .01) following RSDN denervation. The pooled incidence of all-cause mortality after RSDN was 10.16% (95% CI 1.08 to 24.12). There were no major vascular complications, one minor vascular complication-small non-flow limiting renal artery dissection (no intervention needed).

CONCLUSION

RSDN appears to be a safe and effective treatment strategy in patients with prior failed antiarrhythmic drugs and catheter ablation for recurrent ventricular arrhythmia and electrical storm.

Renal Denervation for the Management of Refractory Ventricular Arrhythmias: A Systematic Review

OBJECTIVES

The authors performed a systematic review and meta-analysis to determine the efficacy of renal denervation (RDN) in patients with refractory ventricular arrhythmias (VA) or electrical storm (ES).

BACKGROUND

Although catheter ablation is efficacious for the treatment of structural heart disease ventricular tachycardia (VT), there are proportion of patients who have refractory VT despite multiple procedures. In this setting, novel adjunctive therapies such as renal denervation have been performed.

METHODS

A systematic review of published data was performed. Studies that evaluated patients undergoing RDN for VA or ES were included. Outcome measures of VA, sudden cardiac death, ES, or device therapy were required. Case reports, editorials, and conference presentations were excluded. Random effects meta-analysis was conducted to explore change or final mean values in the study outcomes.

RESULTS

A total of 328 articles were identified by the literature search. Seven studies met the eligibility criteria and were included in the systematic review, with a total of 121 pooled patients. The weighted mean age was 63.8 ± 13.1 years, ejection fraction 30.5 ± 10.3%, 76% were men, 99% were on a beta blocker, 79% were on amiodarone, 46% had previously undergone catheter ablation, and 8.3% had previously undergone cardiac sympathetic denervation. Meta-analysis demonstrated a significant effect of RDN in reducing implantable cardiac defibrillator therapies, with a standardized mean difference (SMD) of -3.11 (p < 0.001). RDN also reduced the number of VA episodes (SMD -2.13; p < 0.001), antitachycardia pacing episodes (SMD -2.82; p = 0.002), and shocks (SMD -2.82; p = 0.002).

CONCLUSIONS

RDN is an effective treatment for refractory VAs and ES, although randomized data are lacking.

Bepridil Inhibits Premature Ventricular Complexes Induced by Cardio-Sympathetic Nerve Stimulation in a Canine Experimental Model

Sympathetic nerve activity has arrhythmogenic potential for ventricular arrhythmias associated with structural heart diseases. However, a sufficient amount of beta-blockers occasionally cannot be prescribed in some patients.An experimental study was performed to clarify the therapeutic effects of bepridil, a multiple ionic current inhibitor that does not affect beta-adrenergic receptors, for premature beats occurring during enhanced sympathetic nerve activity. Cardio-sympathetic nerve activity was augmented via stellate-ganglion (SG) stimulation in a canine model (n = 8), and the arrhythmogenic potential and anti-arrhythmic effects of bepridil (2 and 4 mg/kg intravenously) were assessed. For safe use, vagal-stimulation-induced slow HR and programmed electrical stimulation were applied to evaluate possible pro-arrhythmic effects of the drug. Heart rate variability (HRV) indexes were used to estimate cardio-autonomic nerve activity.Either side of the SG-stimulation increased BP and HR. Premature beats were induced in 10/16 SG-stimulations and it was more frequent in left (8/8) rather than right stimulation (2/8). Following 2 mg/kg drug administration, premature beats were still inducible in 8/16 stimulations (7/8 in left and 1/8 in right), but burden of the premature beats decreased from 87.1 ± 46.8 to 62.1 ± 42.6 beats. After 4 mg/kg administration, premature beats were inducible in one SG-stimulation. Proarrhythmic effects were not observed in all experiments. Steady-state HRV indexes and percent increases in SG-stimulation-induced BP-elevation and HR-acceleration were similar among the 3 periods (before, 2 and 4 mg/kg of the drug).Bepridil may be an option for ventricular arrhythmias developed during enhanced cardio-sympathetic nerve activity with minimal effect on autonomic nerve responses.

Renal Denervation in Asia: Consensus Statement of the Asia Renal Denervation Consortium

The Asia Renal Denervation Consortium consensus conference of Asian physicians actively performing renal denervation (RDN) was recently convened to share up-to-date information and regional perspectives, with the goal of consensus on RDN in Asia. First- and second-generation trials of RDN have demonstrated the efficacy and safety of this treatment modality for lowering blood pressure in patients with resistant hypertension. Considering the ethnic differences of the hypertension profile and demographics of cardiovascular disease demonstrated in the SYMPLICITY HTN (Renal Denervation in Patients With Uncontrolled Hypertension)-Japan study and Global SYMPLICITY registry data from Korea and Taiwan, RDN might be an effective hypertension management strategy in Asia. Patient preference for device-based therapy should be considered as part of a shared patient-physician decision process. A practical population for RDN treatment could consist of Asian patients with uncontrolled essential hypertension, including resistant hypertension. Opportunities to refine the procedure, expand the therapy to other sympathetically mediated diseases, and explore the specific effects on nocturnal and morning hypertension offer a promising future for RDN. Based on available evidence, RDN should not be considered a therapy of last resort but as an initial therapy option that may be applied alone or as a complementary therapy to antihypertensive medication.

Renal denervation as adjunctive therapy to cardiac sympathetic denervation for ablation refractory ventricular tachycardia

BACKGROUND

Autonomic modulation is finding an increasing role in the treatment of ventricular arrhythmias. Renal denervation (RDN) has been described as a treatment modality for refractory ventricular tachycardia (VT) in case series.

OBJECTIVE

The purpose of this study was to evaluate RDN as an adjunctive therapy to cardiac sympathetic denervation (CSD) for ablation refractory VT.

METHODS

Patients who underwent RDN after radiofrequency ablation and CSD procedures at our center from 2012 to 2019 were evaluated.

RESULTS

Ten patients underwent RDN after CSD (9 bilateral and 1 left-sided only) with a median follow-up of 23 months. The mean age was 59.9 ± 10.4 years, and 9/10 (90%) were men. All had cardiomyopathy with a mean ejection fraction of 33% ± 11% (20% ischemic). Four (40%) underwent CSD during the same hospitalization as that for RDN. Patients who underwent RDN as adjunctive therapy to CSD had a decrease in all implantable cardioverter-defibrillator therapies (shocks + antitachycardia pacing [ATP]) from 29.5 ± 25.2 to 7.1 ± 10.1 comparing 6 months pre-RDN to 6 months post-RDN (P = .028). Implantable cardioverter-defibrillator shocks were significantly decreased from 7.0 ± 6.1 to 1.7 ± 2.5 comparing 6 months pre-RDN to 6 months post-RDN (P = .026). This benefit was driven by a decrease in therapies for 6 patients who had a staged procedure, not performed during the same hospitalization (28.5 ± 24.3 to 1.0 ± 1.2; P = .043).

CONCLUSION

RDN demonstrates the potential benefit when VT recurs after radiofrequency ablation and CSD. The benefit is seen in patients who undergo a staged procedure. The need for acute RDN after CSD portends a poor prognosis.

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.