Renal Denervation for the Treatment of Cardiovascular High Risk-Hypertension or Beyond?

Sympathetic Modulation in Cardiac Arrhythmias: Where We Stand and Where We Go

The nuance of autonomic cardiac control has been studied for more than 400 years, yet little is understood. This review aimed to provide a comprehensive overview of the current understanding, clinical implications, and ongoing studies of cardiac sympathetic modulation and its anti-ventricular arrhythmias' therapeutic potential. Molecular-level studies and clinical studies were reviewed to elucidate the gaps in knowledge and the possible future directions for these strategies to be translated into the clinical setting. Imbalanced sympathoexcitation and parasympathetic withdrawal destabilize cardiac electrophysiology and confer the development of ventricular arrhythmias. Therefore, the current strategy for rebalancing the autonomic system includes attenuating sympathoexcitation and increasing vagal tone. Multilevel targets of the cardiac neuraxis exist, and some have emerged as promising antiarrhythmic strategies. These interventions include pharmacological blockade, permanent cardiac sympathetic denervation, temporal cardiac sympathetic denervation, etc. The gold standard approach, however, has not been known. Although neuromodulatory strategies have been shown to be highly effective in several acute animal studies with very promising results, the individual and interspecies variation between human autonomic systems limits the progress in this young field. There is, however, still much room to refine the current neuromodulation therapy to meet the unmet need for life-threatening ventricular arrhythmias.

Hypertension management in patients with cardiovascular comorbidities

Arterial hypertension is a leading cause of death globally. Due to ageing, the rising incidence of obesity, and socioeconomic and environmental changes, its incidence increases worldwide. Hypertension commonly coexists with Type 2 diabetes, obesity, dyslipidaemia, sedentary lifestyle, and smoking leading to risk amplification. Blood pressure lowering by lifestyle modifications and antihypertensive drugs reduce cardiovascular (CV) morbidity and mortality. Guidelines recommend dual- and triple-combination therapies using renin–angiotensin system blockers, calcium channel blockers, and/or a diuretic. Comorbidities often complicate management. New drugs such as angiotensin receptor-neprilysin inhibitors, sodium–glucose cotransporter 2 inhibitors, glucagon-like peptide-1 receptor agonists, and non-steroidal mineralocorticoid receptor antagonists improve CV and renal outcomes. Catheter-based renal denervation could offer an alternative treatment option in comorbid hypertension associated with increased sympathetic nerve activity. This review summarises the latest clinical evidence for managing hypertension with CV comorbidities.

Impact of drug adherence on blood pressure response to alcohol-mediated renal denervation

PURPOSE

While poor drug adherence is frequent in patients with resistant hypertension, detailed analyses of the impact of drug adherence on the success of renal denervation are scarce. We report drug adherence at baseline, changes in drug adherence, and the influence of these parameters on blood pressure changes at 6 and 12 months in patients treated with alcohol-mediated renal denervation as part of the Peregrine study.

MATERIALS AND METHODS

Urinary detection of antihypertensive drugs was performed using high-performance liquid chromatography-tandem mass spectrometry. Full adherence, partial adherence, and complete non-adherence were defined as 0, 1, or ≥2 drugs not detected, respectively.

RESULTS

Renal denervation was performed in 45 patients with uncontrolled hypertension on ≥3 antihypertensive medications (62% men, age 55 ± 10 years). At baseline, the proportion of fully, partially, and non-adherent patients was 62% (n = 28), 16% (n = 7), and 22% (n = 10), respectively. At 6 months, adherence improved by 21% (n = 9), remained unchanged at 49% (n = 21), and worsened by 30% (n = 13). Mean 24-h systolic blood pressure decreased by 10 ± 13, 10 ± 4, and 14 ± 19 mmHg in fully, partially, and non-adherent patients (p = 0.77), and by 14 ± 14, 8 ± 11, and 14 ± 18 mmHg in patients who improved, maintained, or decreased adherence, respectively (p = 0.35). The results at 12 months were similar.

CONCLUSION

About 40% of patients with apparently treatment-resistant hypertension were not fully adherent at baseline, and adherence decreased further in 30%. Nevertheless, mean blood pressure changes after renal denervation were similar irrespective of drug adherence. Our results suggest that such patients may benefit from alcohol-mediated renal denervation, irrespective of drug adherence. These findings are hypothesis-generating and need to be confirmed in ongoing sham-controlled trials.

Renal denervation as a management strategy for hypertension: current evidence and recommendations

INTRODUCTION

The concept of targeting the renal sympathetic nerves therapeutically to lower blood pressure (BP) is based on their crucial role in regulating both renal and cardiovascular control. These effects are mainly mediated via three major mechanisms including alteration of renal blood flow, renin-release, and Na⁺ retention. Initial surgical approaches applying crude and unselected sympathectomy, while rendering significant BP lowering and cardiovascular event reducing properties, where plagued by side effects. More modern selective catheter-based denervation approaches selectively targeting the renal nerves have been shown to be safe and effective in reducing BP in various forms of hypertension and multiple comorbidities.

AREAS COVERED

This article covers the background relevant for the concept of renal denervation (RDN), the evidence obtained from relevant randomized controlled trials to substantiate the safety and efficacy of RDN, and recently published clinical recommendations.

EXPERT OPINION

Catheter-based RDN is safe and has now been shown in sham-controlled randomized clinical trials to result in clinically meaningful BP lowering in both drug naïve hypertensive patients and those on concomitant antihypertensive therapy. Real world data from a large global registry further supports the clinical utility of RDN. It now seems time to embed renal denervation into routine clinical care.

Aorticorenal ganglion as a novel target for renal neuromodulation

BACKGROUND

Clinical trials for renal artery (RA) ablation have shown limited efficacy.

OBJECTIVE

The purpose of this study was to investigate whether the aorticorenal ganglion (ARG) can be targeted for renal denervation.

METHODS

Twenty-eight pigs were studied under isoflurane or alpha-chloralose to examine hemodynamic responses and catecholamine release in response to RA or ARG stimulation. To assess the efficacy of ARG ablation, we randomized 16 pigs to either sham, RA, or ARG ablation, followed by occlusion of the left anterior descending coronary artery (LAD). Hemodynamic responses, cardiac electrophysiological parameters, and arrhythmias/sudden cardiac death were assessed following LAD occlusion. Absent hemodynamic responses to stimulation confirmed ARG or RA ablation. In vivo stellate ganglion neural activity was recorded to assess cardiac sympathetic signaling. Cadaveric dissections were performed to localize the ARG in humans for comparison to swine.

RESULTS

The ARG is a purely sympathetic ganglion with cholinergic inputs and pass-through sensory afferent fibers. Compared to RA stimulation, ARG stimulation yielded greater hemodynamic responses during alpha-chloralose anesthesia. However, neither site yielded significant responses under isoflurane. Radiofrequency ablation of the ARG eliminated responses to both RA and ARG stimulation, whereas RA ablation did not eliminate responses to ARG stimulation. Ablation of the ARG did not impact the kidneys or adrenal glands. Compared to control and RA ablation, ARG ablation was protective against ventricular arrhythmias and sudden death. Human and swine ARG are similarly located in the aorticorenal region.

CONCLUSION

Our findings indicate that the ARG may be a novel target for renal neuromodulation. Further studies are warranted to validate these findings.

Circular Radio-Frequency Electrode With MEMS Temperature Sensors for Laparoscopic Renal Sympathetic Denervation

OBJECTIVE

Laparoscopic renal denervation (LRDN) ablates sympathetic nerves on the outer wall of a renal artery to treat autonomic nervous system disorders such as hypertension and arrhythmia. Here, we developed a new circular radio frequency (RF) electrode for LRDN using micro-electro-mechanical systems (MEMS) technology.

METHODS

The electrode consists of a parallel bipolar MEMS electrode, two MEMS thermocouples, and a shape-memory alloy (SMA) substrate. The electrode is automatically wrapped and unwrapped under actuation controlled by the heat generated by RF energy on the electrode-tissue interface. The electrode was designed through a computational simulation analysis, and its actuation and temperature-sensing performance were tested in laboratory experiments and a porcine animal study.

RESULTS

In an in-vivo study of porcine renal arteries, the electrode could automatically wrap and unwrap around an artery during LRDN. The bipolar MEMS electrode required 13 V_rms for heat generation up to 60°C, while the two MEMS thermocouples reliably measured the temperature without noise signals (a temperature coefficient of 38.3 or 38.5 µV/°C and an accuracy of ±0.44 or ±0.49°C). As revealed in a histological analysis using hematoxylin and eosin staining and Masson's trichrome staining, the renal artery was intact after LRDN.

CONCLUSION

The circular RF electrode improves the safety of LRDN by reliably measuring the electrode temperature of the electrode during RDN and enhances the effectiveness of LRDN by reducing the complicated manipulations of the surgical instrument.

SIGNIFICANCE

The developed circular RF electrode will pave the way for LRDN treatment of autonomic nervous system disorders.

The Effects of Renal Nerve Denervation on Blood Pressure and Target Organs in Different Hypertensive Rat Models

Background

Hypertension contributes to the progression of cardiac remodeling and renal damage. In turn, renal sympathetic hyperactivation showed elevated sympathetic nervous system activity and led to blood pressure increase in certain patients. The purpose of this study was to observe the effect of renal nerve denervation on blood pressure and target organ changes in two hypertensive rat models.

Methods

Hypertensive rats were randomly divided into a renal denervation (RDN) group and sham operation group. Wistar–Kyoto (WKY) rats of the same age were set as the baseline control group. In the secondary hypertension model, SD rats were randomly divided into five groups. Blood pressure and bodyweight were measured every week until they were euthanized.

Results

The two rat models underwent RDN at key timepoints. At these timepoints, the hearts and kidneys were collected for norepinephrine and angiotensin II measurements and histological analysis.

Conclusion

RDN performed before development of hypertension showed a significant antihypertensive effect on the secondary hypertension model.

Device Therapy of Hypertension

In the past decade, efforts to improve blood pressure control have looked beyond conventional approaches of lifestyle modification and drug therapy to embrace interventional therapies. Based upon animal and human studies clearly demonstrating a key role for the sympathetic nervous system in the etiology of hypertension, the newer technologies that have emerged are predominantly aimed at neuromodulation of peripheral nervous system targets. These include renal denervation, baroreflex activation therapy, endovascular baroreflex amplification therapy, carotid body ablation, and pacemaker-mediated programmable hypertension control. Of these, renal denervation is the most mature, and with a recent series of proof-of-concept trials demonstrating the safety and efficacy of radiofrequency and more recently ultrasound-based renal denervation, this technology is poised to become available as a viable treatment option for hypertension in the foreseeable future. With regard to baroreflex activation therapy, endovascular baroreflex amplification, carotid body ablation, and programmable hypertension control, these are developing technologies for which more human data are required. Importantly, central nervous system control of the circulation remains a poorly understood yet vital component of the hypertension pathway and mandates further investigation. Technology to improve blood pressure control through deep brain stimulation of key cardiovascular control territories is, therefore, of interest. Furthermore, alternative nonsympathomodulatory intervention targeting the hemodynamics of the circulation may also be worth exploring for patients in whom sympathetic drive is less relevant to hypertension perpetuation. Herein, we review the aforementioned technologies with an emphasis on the preclinical data that underpin their rationale and the human evidence that supports their use.

The current status of renal denervation for the treatment of arterial hypertension

Despite the availability of safe and effective antihypertensive drugs, blood pressure (BP) control to guideline-recommended target values is poor. Several device-based therapies have been introduced to lower BP. The most extensively investigated approach is catheter-based renal sympathetic denervation (RDN), which aims to interrupt the activity of afferent and efferent renal sympathetic nerves by applying radiofrequency energy, ultrasound energy, or injection of alcohol in the perivascular space. The second generation of placebo-controlled trials have provided solid evidence for the BP-lowering efficacy of radiofrequency- and ultrasound-based RDN in patients with and without concomitant pharmacological therapy. In addition, the safety profile of RDN appears to be excellent in all registries and clinical trials. However, there remain unsolved issues to be addressed. This review summarizes the rationale as well as the current evidence and discusses open questions and possible future indications of catheter-based RDN.

Effects of renal denervation on kidney function and long-term outcomes: 3-year follow-up from the Global SYMPLICITY Registry

Aims

Several studies and registries have demonstrated sustained reductions in blood pressure (BP) after renal denervation (RDN). The long-term safety and efficacy after RDN in real-world patients with uncontrolled hypertension, however, remains unknown. The objective of this study was to assess the long-term safety and efficacy of RDN, including its effects on renal function.

Methods and results

The Global SYMPLICITY Registry is a prospective, open-label registry conducted at 196 active sites worldwide in hypertensive patients receiving RDN treatment. Among 2237 patients enrolled and treated with the SYMPLICITY Flex catheter, 1742 were eligible for follow-up at 3 years. Baseline office and 24-h ambulatory systolic BP (SBP) were 166 ± 25 and 154 ± 18 mmHg, respectively. SBP reduction after RDN was sustained over 3 years, including decreases in both office (−16.5 ± 28.6 mmHg, P < 0.001) and 24-h ambulatory SBP (−8.0 ± 20.0 mmHg; P < 0.001). Twenty-one percent of patients had a baseline estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m². Between baseline and 3 years, renal function declined by 7.1 mL/min/1.73 m² in patients without chronic kidney disease (CKD; eGFR ≥60 mL/min/1.73 m²; baseline eGFR 87 ± 17 mL/min/1.73 m²) and by 3.7 mL/min/1.73 m² in patients with CKD (eGFR <60 mL/min/1.73 m²; baseline eGFR 47 ± 11 mL/min/1.73 m²). No long-term safety concerns were observed following the RDN procedure.

Conclusion

Long-term data from the Global SYMPLICITY Registry representing the largest available cohort of hypertensive patients receiving RDN in a real-world clinical setting demonstrate both the safety and efficacy of the procedure with significant and sustained office and ambulatory BP reductions out to 3 years.

Evaluation of Transcatheter Alcohol-Mediated Perivascular Renal Denervation to Treat Resistant Hypertension

Catheter-based renal denervation (RDN) has been investigated for hypertension (HTN) treatment with variable success. One of the novel approaches to RDN is the delivery of micro-doses of dehydrated alcohol to the adventitial space of the renal artery to perform perivascular ablation of the sympathetic nerves. We sought to assess the safety and efficiency of transcatheter alcohol-mediated perivascular renal denervation in patients with resistant hypertension. Fifty adult patients who had been referred for resistant HTN were screened. To qualify for the study, the patients had to have a mean 24 h systolic pressure ≥ 135 mmHg based upon ambulatory blood pressure monitoring (ABPM) and acceptable renal artery anatomy confirmed by the contrast computer tomography (AngioCT) and nephrologist consultation. Ten patients were eligible for chemical RND. There were no safety issues throughout the 24 months of follow-ups. The mean decrease in the office BP (OBP) was significant during 24 months of follow-up (p < 0.01). The difference in the BP in the ABPM was statistically significant in the 1st, 3rd and 12th months (p < 0.01), whereas during the 3-month follow-up, a trend was observed. The modifications of anti-hypertension drugs throughout the follow-up period were minimal. This study has shown that transcatheter alcohol-mediated renal denervation in patients with resistant hypertension is feasible and safe. Nevertheless, it is a hypothesis-generating study.

The Current Status of Devices for the Treatment of Resistant Hypertension

Arterial hypertension is associated with increased cardiovascular morbidity and mortality. Although blood pressure-lowering therapies significantly reduce the risk of major cardiovascular events, blood pressure control remains unsatisfactorily low. Several device-based antihypertensive therapies have been investigated in patients with treatment-resistant hypertension and in patients unable or unwilling to adhere to antihypertensive medication. As the field of device-based therapies is subject to constant change, this review aims at providing an up-to-date overview of different device-based approaches for the treatment of hypertension. These approaches target the sympathetic nervous system (renal denervation, baroreflex amplification therapy, baroreflex activation therapy, and carotid body ablation) or alter mechanical arterial properties by creating an iliac arteriovenous fistula. Notably, the use of all of these treatment options is not recommended for the routine treatment of hypertension by current guidelines but should be investigated in the context of controlled clinical studies.

Looking back and thinking forwards - 15 years of cardiology and cardiovascular research

The first issue of Nature Reviews Cardiology was published in November 2004 under the name Nature Clinical Practice Cardiovascular Medicine. To celebrate our 15th anniversary in 2019, we invited six of our Advisory Board members to discuss what they considered the most important advances in their field of cardiovascular research or clinical practice in the past 15 years and what changes they envision for cardiovascular medicine in the next 15 years. Several practice-changing breakthroughs are described, including advances in procedural techniques to treat arrhythmias and hypertension and the development of novel therapeutic strategies to treat heart failure and pulmonary arterial hypertension, as well as those that target risk factors such as inflammation and elevated LDL-cholesterol levels. Furthermore, these key opinion leaders predict that machine learning technology and data derived from wearable devices will pave the way towards the coveted goal of personalized medicine.

Electrical stimulation-based renal nerve mapping exacerbates ventricular arrhythmias during acute myocardial ischaemia

OBJECTIVE

Blood pressure elevation in response to transient renal nerve stimulation (RNS) has been used to determine the ablation target and endpoint of renal denervation. This study aimed to evaluate the safety of transient RNS in canines with normal or ischaemic hearts.

METHODS

In ten normal (Group 1) and six healed myocardial infarction (HMI) (Group 2) canines, a large-tip catheter was inserted into the left or right renal artery to perform transient RNS. The left stellate ganglion neural activity (LSGNA) and ventricular electrophysiological parameters were measured at baseline and during transient RNS. In another 20 acute myocardial infarction (AMI) canines, RNS (Group 3, n = 10) or sham RNS (Group 4, n = 10) was intermittently (1 min ON and 4 min OFF) performed for 1 h following AMI induction. The LSGNA and AMI-induced ventricular arrhythmias were analysed.

RESULTS

In normal and HMI canines, although transient RNS significantly increased the LSGNA and facilitated the action potential duration (APD) alternans, it did not induce any ventricular arrhythmias and did not change the ventricular effective refractory period, APD or maximum slope of the APD restitution curve. In AMI canines, transient RNS significantly exacerbated LSG activation and promoted the incidence of ventricular arrhythmias.

CONCLUSION

Transient RNS did not increase the risk of ventricular arrhythmias in normal or HMI hearts, but it significantly promoted the occurrence of ventricular arrhythmias in AMI hearts. Therefore, electrical stimulation-based renal nerve mapping may be unsafe in AMI patients and in patients with a high risk for malignant ventricular arrhythmias.

New Approaches in the Management of Sudden Cardiac Death in Patients with Heart Failure-Targeting the Sympathetic Nervous System

Cardiovascular diseases (CVDs) have been considered the most predominant cause of death and one of the most critical public health issues worldwide. In the past two decades, cardiovascular (CV) mortality has declined in high-income countries owing to preventive measures that resulted in the reduced burden of coronary artery disease (CAD) and heart failure (HF). In spite of these promising results, CVDs are responsible for ~17 million deaths per year globally with ~25% of these attributable to sudden cardiac death (SCD). Pre-clinical data demonstrated that renal denervation (RDN) decreases sympathetic activation as evaluated by decreased renal catecholamine concentrations. RDN is successful in reducing ventricular arrhythmias (VAs) triggering and its outcome was not found inferior to metoprolol in rat myocardial infarction model. Registry clinical data also suggest an advantageous effect of RDN to prevent VAs in HF patients and electrical storm. An in-depth investigation of how RDN, a minimally invasive and safe method, reduces the burden of HF is urgently needed. Myocardial systolic dysfunction is correlated to neuro-hormonal overactivity as a compensatory mechanism to keep cardiac output in the face of declining cardiac function. Sympathetic nervous system (SNS) overactivity is supported by a rise in plasma noradrenaline (NA) and adrenaline levels, raised central sympathetic outflow, and increased organ-specific spillover of NA into plasma. Cardiac NA spillover in untreated HF individuals can reach ~50-fold higher levels compared to those of healthy individuals under maximal exercise conditions. Increased sympathetic outflow to the renal vascular bed can contribute to the anomalies of renal function commonly associated with HF and feed into a vicious cycle of elevated BP, the progression of renal disease and worsening HF. Increased sympathetic activity, amongst other factors, contribute to the progress of cardiac arrhythmias, which can lead to SCD due to sustained ventricular tachycardia. Targeted therapies to avoid these detrimental consequences comprise antiarrhythmic drugs, surgical resection, endocardial catheter ablation and use of the implantable electronic cardiac devices. Analogous NA agents have been reported for single photon-emission-computed-tomography (SPECT) scans usage, specially the 123I-metaiodobenzylguanidine (123I-MIBG). Currently, HF prognosis assessment has been improved by this tool. Nevertheless, this radiotracer is costly, which makes the use of this diagnostic method limited. Comparatively, positron-emission-tomography (PET) overshadows SPECT imaging, because of its increased spatial definition and broader reckonable methodologies. Numerous ANS radiotracers have been created for cardiac PET imaging. However, so far, [11C]-meta-hydroxyephedrine (HED) has been the most significant PET radiotracer used in the clinical scenario. Growing data has shown the usefulness of [11C]-HED in important clinical situations, such as predicting lethal arrhythmias, SCD, and all-cause of mortality in reduced ejection fraction HF patients. In this article, we discussed the role and relevance of novel tools targeting the SNS, such as the [11C]-HED PET cardiac imaging and RDN to manage patients under of SCD risk.

Relevance of Targeting the Distal Renal Artery and Branches with Radiofrequency Renal Denervation Approaches-A Secondary Analysis from a Hypertensive CKD Patient Cohort

We searched for an association between changes in blood pressure (BP) at 12 and 24 months after renal denervation (RDN) and the different patterns of ablation spots placement along the renal artery vasculature. We performed a post-hoc analysis of a 24-month follow-up evaluation of 30 patients who underwent RDN between 2011 and 2012 using our previous database. Patients who had (i) resistant hypertension, as meticulously described previously, and (ii) Chronic kidney disease (CKD) stages 2, 3 and 4. Correlations were assessed using the Pearson or Spearman correlation tests as appropriate. The mean change in systolic ambulatory BP monitoring (ABPM) compared to baseline was −19.4 ± 12.7 mmHg at the 12th (p < 0.0001) and −21.3 ± 14.1 mmHg at the 24th month (p < 0.0001). There was no correlation between the ABPM Systolic Blood Pressure (SBP)-lowering effect and the total number of ablated spots in renal arteries (17.7 ± 6.0) either at 12 (r = −0.3, p = 0.1542) or at 24 months (r = −0.2, p = 0.4009). However, correlations between systolic BP-lowering effect and the number of ablation spots performed in the distal segment and branches were significant at the 12 (r = −0.7, p < 0.0001) and 24 months (r = −0.8, p < 0.0001) follow-up. Our findings indicate a substantial correlation between the numbers of ablated sites in the distal segment and branches of renal arteries and the systolic BP-lowering effect in the long-term.

Serial changes in vessel walls of renal arteries after catheter-based renal artery denervation: insights from volumetric computed tomography analysis

Aim

Radiofrequency ablation of peri-arterial renal autonomic nerves has been studied as a potential therapeutic option for resistant hypertension. While recent clinical trials have reported its efficacy, there is paucity of data addressing the effects of the procedure on renal arteries, such as changes in vessel and lumen areas. Herein, the effect of atheroma burden on renal arteries after renal denervation was assessed using computed tomography (CT) imaging.

Materials and methods

Serial renal artery CT imaging was conducted in 38 patients from the EnligHTN™ I study, a prospective, multicenter study evaluating the efficacy of the EnligHTN multi-electrode radiofrequency ablation catheter in resistant hypertensive subjects. Cross-sectional images of renal arteries at 1 mm intervals were acquired using commercially available software (3mensio Structural Heart version 5.1). Vessel and lumen areas were manually traced in each image. Vessel wall volume (VWV) and percent vessel wall volume (P-VWV) were calculated. The measurements within the ablation (first 30 mm segments) and the non-ablation (subsequent 30 mm segment after the first bifurcation of renal arteries) zones were compared.

Results

On serial evaluation, greater increase in P-VWV and VWV was observed in the ablation zone (change in P-VWV, 6.7%±5.1% vs 3.6%±2.8%, P=0.001; change in VWV, 106.3±87.4 vs 23.0±18.2 mm³, P=0.001). Receiver-operating characteristic analysis demonstrated baseline P-VWV in the ablation zone >37.1% as an optimal cutoff value to predict its substantial progression after the procedure (area under the curve=0.88, sensitivity 89.8%, specificity 79.1%).

Conclusion

Change in vessel wall was greater within the segments receiving renal artery denervation. Baseline VWV predicted its substantial increase after the procedure. These observations suggest that atheroma burden within the renal arteries is a potential contributing factor to vascular changes after renal sympathetic denervation.

Sympathoadrenergic suppression improves heart function by upregulating the ratio of sRAGE/RAGE in hypertension with metabolic syndrome

Receptors-for-Advanced-Glycation-End-products (RAGE) activate pro-inflammatory programs mediated by carboxymethyllysine (CML) and high-mobility-group-box1 protein (HMGB1). The soluble isoform sRAGE neutralizes RAGE-ligands preventing cardiovascular complications in conditions associated with increased sympathetic activation like hypertension and diabetes. The effects of sympathetic modulation on RAGE/sRAGE-balance and end-organ damage in metabolic syndrome on top of hypertension remains unknown. We hypothesized that increased sympathoadrenergic activity might lead to an unfavourable RAGE/sRAGE regulation. Renal denervation (RDN) was used to modulate sympathetic activation in obese spontaneously hypertensive rats (SHRobRDN) versus sham-operated obese spontaneously hypertensive rats (SHRob), their hypertensive lean controls (SHR) and non-hypertensive controls. Cardiac fibrosis was assessed by histological analysis and sRAGE/RAGE and ligand levels by Western blotting. Levels of CML and HMGB1 were highest in SHRob and were significantly lowered by RDN in serum (-44% and -45%) and myocardium (-25% and -52%). Myocardial RAGE was increased in SHR (+72% versus controls) and in SHRob (+68% versus SHR) while sRAGE decreased (-50% in SHR versus controls and -51% in SHRob versus SHR). RDN reduced myocardial RAGE expression. (-20%) and increased sRAGE levels in heart (+80%) and serum (+180%) versus sham-operated SHRob. Myocardial fibrosis correlated inversely with myocardial sRAGE content (r = -0.79; p = .004; n = 10). Myocardial sRAGE shedding active A-Disintegrin-And-Metalloprotease-10 (ADAM-10) was decreased in SHR (-33% versus controls) and in SHRob (-54% versus SHR), and was restored after RDN (+129% versus SHRob). Serum ADAM-10 activity was also decreased in SHRob (-66% versus SHR) and restored after RDN (+150% versus SHRob). In vitro, isoproterenol induced a ß1-adrenergic receptor mediated increase of RAGE expression in splenocytes (+200%) and decreased sRAGE secretion of splenocytes and cardiac fibroblasts (-50% and -49%) by ß2-adrenergic receptor stimulation mediated suppression of ADAM-10 activity. In conclusion, sympathetic activity affects sRAGE/RAGE-balance, which can be suppressed through sympathetic modulation by RDN, preventing RAGE-induced cardiac damage in hypertension with metabolic syndrome.

Reduced blood pressure-lowering effect of catheter-based renal denervation in patients with isolated systolic hypertension: data from SYMPLICITY HTN-3 and the Global SYMPLICITY Registry

Aims

Catheter-based renal artery denervation (RDN) has been shown to lower blood pressure (BP) in certain patients with uncontrolled hypertension. Isolated systolic hypertension (ISH) (systolic BP [SBP] ≥140 mmHg and diastolic BP <90 mmHg), characterized by increased vascular stiffness, is the predominant hypertensive phenotype in elderly patients. This study compared baseline characteristics and SBP change at 6 months between patients with ISH and combined systolic–diastolic hypertension (CH).

Methods and results

This study pooled data from 1103 patients from SYMPLICITY HTN-3 and the Global SYMPLICITY Registry. A total of 429 patients had ISH, and 674 had CH. Patients with ISH were significantly older than those with CH (66 vs. 55 years), had more type 2 diabetes mellitus (52.9 vs. 34.6%), and a lower estimated glomerular filtration rate (71.8 vs. 78.6 mL/min/1.73 m²); all P < 0.001. At 6 months, the SBP drop for CH patients was −18.7 ± 23.7 mmHg compared with a reduction of −10.9 ± 21.7 mmHg for ISH patients −7.8 mmHg, 95% confidence interval, CI, −10.5, −5.1, P < 0.001). The change in 24-h SBP at 6 months was −8.8 ± 16.2 mmHg in patients with CH vs. −5.8 ± 15.4 mmHg in ISH (−3.0 mmHg, 95% CI −5.4, −0.6, P = 0.015). Presence of ISH at baseline but not age was associated with less pronounced BP changes following the procedure. The strongest predictor of office SBP reduction at 6 months was CH, followed by aldosterone antagonist use and non-use of vasodilators.

Conclusion

The reduction in BP among patients with ISH following RDN was less pronounced than the reduction in patients with CH.

Clinical.Trials.gov identifiers

NCT01534299 and NCT01418261.

Design and simulation of novel laparoscopic renal denervation system: a feasibility study

PURPOSE

In this study, we propose a novel laparoscopy-based renal denervation (RDN) system for treating patients with resistant hypertension. In this feasibility study, we investigated whether our proposed surgical instrument can ablate renal nerves from outside of the renal artery safely and effectively and can overcome the depth-related limitations of the previous catheter-based system with less damage to the arterial walls.

METHOD

We designed a looped bipolar electrosurgical instrument to be used with laparoscopy-based RDN system. The tip of instrument wraps around the renal artery and delivers the radio-frequency (RF) energy. We evaluated the thermal distribution via simulation study on a numerical model designed using histological data and validated the results by the in vitro study. Finally, to show the effectiveness of this system, we compared the performance of our system with that of catheter-based RDN system through simulations.

RESULTS

Simulation results were within the 95% confidence intervals of the in vitro experimental results. The validated results demonstrated that the proposed laparoscopy-based RDN system produces an effective thermal distribution for the removal of renal sympathetic nerves without damaging the arterial wall and addresses the depth limitation of catheter-based RDN system.

CONCLUSIONS

We developed a novel laparoscope-based electrosurgical RDN method for hypertension treatment. The feasibility of our system was confirmed through a simulation study as well as in vitro experiments. Our proposed method could be an effective treatment for resistant hypertension as well as central nervous system diseases.

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.

Catheter-based radio-frequency renal nerve denervation lowers blood pressure in obese hypertensive swine model

OBJECTIVES

Radio-frequency renal denervation (RDN) therapy is under investigation for the treatment of uncontrolled hypertension. Data in hypertensive, drug-naïve large animal models using RDN is limited.

METHODS

A cohort of Ossabaw swine (N = 9) was implanted with telemetry monitors, enrolled on a high calorie-feed regimen and randomly assigned to RDN. Blood pressure (BP) data were separated and analyzed according to the following epoch definitions: 24-h (h), most-active-h, light-h, and dark-h.

RESULTS

The mean weight increased by 45% from 86.5 ± 2.5 kg at telemetry implant (day 87) to 125.2 ± 4.5 kg at time of RDN therapy (day 227). Hypertension developed in all swine (24-h BP: 169.5/128.3 ± 5.8/5.1 mmHg pre-RDN). RDN resulted in significant reductions in noradrenaline kidney tissue concentration by 63%. Significant BP reductions were documented at 45 days post-RDN in all defined interday epochs, except for the dark-h period. The most pronounced SBP/DBP reduction was 12.4/11.2 mmHg (P < 0.05), observed during the most-active-h period. Animals continued to gain weight after the RDN procedure to the end of the study at 90 days (125.2 ± 4.5-138.5 ± 6.6 kg, P < 0.001). At 90 days post-RDN, the mean 24-h BP returned near pre-RDN baseline values. Given the strong relationship of BP to weight (R = 0.87, P < 0.001), group mean SBP/DBP was normalized by weight resulting in significant and continued reductions at both 45 and 90 days post-RDN across all intradaily epochs.

CONCLUSION

Catheter-based RDN, using a multielectrode system, resulted in a significant reduction in 24-h BP in this drug-naïve, hypertensive animal model.

Efficacy and safety of renal denervation for Chinese patients with resistant hypertension using a microirrigated catheter: study design and protocol for a prospective multicentre randomised controlled trial

INTRODUCTION

Available data show that approximately 8%-18% of patients with primary hypertension will develop resistant hypertension. In recent years, catheter-based renal denervation (RDN) has emerged as a potential treatment option for resistant hypertension. A number of observational studies and randomised controlled trials among non-Chinese patients have demonstrated its potential safety and efficacy.

METHODS AND ANALYSIS

This is a multicentre, randomised, open-label, parallel-group, active controlled trial that will investigate the efficacy and safety of a 5F saline-irrigated radiofrequency ablation (RFA) used for RDN in the treatment of Chinese patients with resistant hypertension. A total of 254 patients who have failed pharmacological therapy will be enrolled. Eligible subjects will be randomised in a 1:1 ratio to undergo RDN using the RFA plus antihypertensive medication or to receive treatment with antihypertensive medication alone. The primary outcome measure is the change in 24 hours average ambulatory systolic blood pressure from baseline to 3 months, comparing the RDN-plus-medication group with the medication-alone group. Important secondary endpoints include the change in office blood pressure from baseline to 6 months after randomisation. Safety endpoints such as changes in renal function will also be evaluated. The full analysis set, according to the intent-to-treat principle, will be established as the primary analysis population.

ETHICS AND DISSEMINATION

All participants will provide informed consent; the study protocol has been approved by the Independent Ethics Committee for each site. This study is designed to investigate the efficacy and safety of RDN using a 5F saline microirrigated RFA. Findings will be shared with participating hospitals, policymakers and the academic community to promote the clinical management of resistant hypertension in China.

TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT02900729; pre-results.

Renal denervation attenuates cardiac hypertrophy in spontaneously hypertensive rats via regulation of autophagy

It has been suggested that renal denervation (RD) may attenuate left ventricular (LV) hypertrophy. However, the role that autophagy serves in this process is currently unclear. In the present study, utilizing a model of hypertension-induced cardiac hypertrophy in spontaneous hypertensive rats, it was demonstrated that RD was significantly associated with a reduction in LV hypertrophy. Furthermore, a decrease in the myocardial mRNA of hypertrophy-associated genes was demonstrated in RD rats compared with sham controls. In addition, RD in hypertension-induced LV hypertrophy rats was associated with the attenuation of cellular autophagic response over activation at a physiological level. This was indicated by a reduction in the expression of Beclin-1, autophagy related 9A and microtubule-associated protein 1A/1B-light chain 3 II/I in RD rats to physiological levels that are observed in control rats. Furthermore, the number of autophagosomes was restored to physiological levels in the cardiomyocytes of RD rats. The results of the current study suggest that RD may attenuate LV hypertrophy via the regulation of autophagic responses.

Renal Denervation Reduces Pulmonary Vascular Remodeling and Right Ventricular Diastolic Stiffness in Experimental Pulmonary Hypertension

Neurohormonal overactivation plays an important role in pulmonary hypertension (PH). In this context, renal denervation, which aims to inhibit the neurohormonal systems, may be a promising adjunct therapy in PH. In this proof-of-concept study, we have demonstrated in 2 experimental models of PH that renal denervation delayed disease progression, reduced pulmonary vascular remodeling, lowered right ventricular afterload, and decreased right ventricular diastolic stiffness, most likely by suppression of the renin-angiotensin-aldosterone system.

Renal denervation in male rats with heart failure improves ventricular sympathetic nerve innervation and function

Heart failure is characterized by the loss of sympathetic innervation to the ventricles, contributing to impaired cardiac function and arrhythmogenesis. We hypothesized that renal denervation (RDx) would reverse this loss. Male Wistar rats underwent myocardial infarction (MI) or sham surgery and progressed into heart failure for 4 wk before receiving bilateral RDx or sham RDx. After additional 3 wk, left ventricular (LV) function was assessed, and ventricular sympathetic nerve fiber density was determined via histology. Post-MI heart failure rats displayed significant reductions in ventricular sympathetic innervation and tissue norepinephrine content (nerve fiber density in the LV of MI+sham RDx hearts was 0.31 ± 0.05% vs. 1.00 ± 0.10% in sham MI+sham RDx group, P < 0.05), and RDx significantly increased ventricular sympathetic innervation (0.76 ± 0.14%, P < 0.05) and tissue norepinephrine content. MI was associated with an increase in fibrosis of the noninfarcted ventricular myocardium, which was attenuated by RDx. RDx improved LV ejection fraction and end-systolic and -diastolic areas when compared with pre-RDx levels. This is the first study to show an interaction between renal nerve activity and cardiac sympathetic nerve innervation in heart failure. Our findings show denervating the renal nerves improves cardiac sympathetic innervation and function in the post-MI failing heart.

Renal Denervation Improves the Baroreflex and GABA System in Chronic Kidney Disease-induced Hypertension

Hypertensive rats with chronic kidney disease (CKD) exhibit enhanced gamma-aminobutyric acid (GABA)_B receptor function and regulation within the nucleus tractus solitarii (NTS). For CKD with hypertension, renal denervation (RD) interrupts the afferent renal sympathetic nerves, which are connecting to the NTS. The objective of the present study was to investigate how RD improves CKD-induced hypertension. Rats underwent 5/6 nephrectomy for 8 weeks, which induced CKD and hypertension. RD was induced by applying phenol to surround the renal artery in CKD. RD improved blood pressure (BP) by lowering sympathetic nerve activity and markedly restored the baroreflex response in CKD. The GABA_B receptor expression was increased in the NTS of CKD; moreover, the central GABA levels were reduced in the cerebrospinal fluid, and the peripheral GABA levels were increased in the serum. RD restored the glutamic acid decarboxylase activity in the NTS in CKD, similar to the effect observed for central treatment with baclofen, and the systemic administration of gabapentin reduced BP. RD slightly improved renal function and cardiac load in CKD. RD may improve CKD-induced hypertension by modulating the baroreflex response, improving GABA system dysfunction and preventing the development and reducing the severity of cardiorenal syndrome type 4 in CKD rats.

Renal Denervation for Chronic Heart Failure: Background and Pathophysiological Rationale

The activation of the sympathetic nervous system is associated with cardiovascular hospitalizations and death in heart failure. Renal denervation has been shown to effectively reduce sympathetic overdrive in certain patients with uncontrolled hypertension. Pilot trials investigating renal denervation as a potential treatment approach for heart failure were initiated. Heart failure comorbidities like obstructive sleep apnea, metabolic syndrome and arrhythmias could also be targets for renal denervation, because these occurrences are also mediated by the activation of the sympathetic nervous system. Therefore, renal denervation in heart failure is worthy of further investigation, although its effectiveness still has to be proven. Herein, we describe the pathophysiological rationale and the effect of renal denervation on surrogates of the heart failure syndrome.

Neurocardiology: Structure-Based Function

Cardiac control is mediated via a series of reflex control networks involving somata in the (i) intrinsic cardiac ganglia (heart), (ii) intrathoracic extracardiac ganglia (stellate, middle cervical), (iii) superior cervical ganglia, (iv) spinal cord, (v) brainstem, and (vi) higher centers. Each of these processing centers contains afferent, efferent, and local circuit neurons, which interact locally and in an interdependent fashion with the other levels to coordinate regional cardiac electrical and mechanical indices on a beat-to-beat basis. This control system is optimized to respond to normal physiological stressors (standing, exercise, and temperature); however, it can be catastrophically disrupted by pathological events such as myocardial ischemia. In fact, it is now recognized that autonomic dysregulation is central to the evolution of heart failure and arrhythmias. Autonomic regulation therapy is an emerging modality in the management of acute and chronic cardiac pathologies. Neuromodulation-based approaches that target select nexus points of this hierarchy for cardiac control offer unique opportunities to positively affect therapeutic outcomes via improved efficacy of cardiovascular reflex control. As such, understanding the anatomical and physiological basis for such control is necessary to implement effectively novel neuromodulation therapies. © 2016 American Physiological Society. Compr Physiol 6:1635-1653, 2016.

Renal denervation for treatment of ventricular arrhythmias: data from an International Multicenter Registry

INTRODUCTION

Ventricular arrhythmias (VAs) in patients with chronic heart failure (CHF) are sometimes refractory to antiarrhythmic drugs and cardiac ablation. This study aimed to investigate catheter-based renal sympathetic denervation (RDN) as antiarrhythmic strategy in refractory VA.

METHODS

These are the first data from a pooled analysis of 13 cases from five large international centers (age 59.2 ± 14.4 years, all male) with CHF (ejection fraction 25.8 ± 10.1 %, NYHA class 2.6 ± 1) presented with refractory VA who underwent RDN. Ventricular arrhythmias, ICD therapies, clinical status, and blood pressure (BP) were evaluated before and 1-12 months after RDN.

RESULTS

Within 4 weeks prior RDN, a median of 21 (interquartile range 10-30) ventricular tachycardia (VT) or fibrillation (VF) episodes occurred despite antiarrhythmic drugs and prior cardiac ablation. RDN was performed bilaterally with a total number of 12.5 ± 3.5 ablations and without peri-procedural complications. One and 3 months after RDN, VT/VF episodes were reduced to 2 (0-7) (p = 0.004) and 0 (p = 0.006), respectively. Four (31 %) and 11 (85 %) patients of these 13 patients were free from VA at 1 and 3 months. Although BP was low at baseline (116 ± 18/73 ± 13 mmHg), no significant changes of BP or NYHA class were observed after RDN. During follow-up, three patients died from non-rhythm-related causes.

CONCLUSIONS

In patients with CHF and refractory VA, RDN appears to be safe concerning peri-procedural complications and blood pressure changes, and is associated with a reduced arrhythmic burden.

Resistance to renal denervation therapy — Identification of underlying mechanisms by analysis of differential DNA methylation

Background

Factors causing resistance to renal denervation (RDN) for treatment of arterial hypertension are not known. In the current study, we sought to determine mechanisms involved in responsiveness to renal denervation therapy in patients with difficult-to-control and resistant hypertension.

Methods and results

We evaluated the differential CpG methylation of genes in blood samples isolated from patients of a recently described cohort of responders or non-responders to renal denervation using microarray technique and measured protein levels of identified downstream effectors in blood samples of these patients by ELISA.

Our analysis revealed up to 6103 methylation sites differing significantly between non-responders and responders to renal denervation therapy. Software based analysis showed several of these loci to be relevant for arterial hypertension and sympathetic nervous activity. Particularly, genes involved in glutamate synthesis, degradation and glutamate signaling pathways were differently methylated between both groups. For instance, genes for glutamate dehydrogenase 1 and 2 central to glutamate metabolism, genes for ionotropic (AMPA, NMDA) and metabotropic glutamate receptors as well as glutamate transporters revealed significant differences in methylation correlating with responsiveness to RDN. To underline their potential relevance for responsiveness to RDN, we measured plasma protein levels of norepinephrine, a downstream effector of the glutamate receptor pathway, which were significantly lower in non-responders to RDN.

Conclusions

The present study describes novel molecular targets potentially contributing to reduction of blood pressure after RDN in some patients. Identifying patients with a high responsiveness to RDN could contribute to an individualized therapy in drug resistant hypertension.