Effectiveness of renal denervation therapy for resistant hypertension: a systematic review and meta-analysis

The role of renal denervation in cardiology and beyond: An updated comprehensive review and future directives

Renal denervation (RDN) is a minimally invasive intervention performed by denervation of the nervous fibers in the renal plexus, which decreases sympathetic activity. These sympathetic nerves influence various physiological functions that regulate blood pressure (BP), including intravascular volume, electrolyte composition, and vascular tone. Although proven effective in some trials, controversial trials, such as the Controlled Trial of Renal Denervation for Resistant Hypertension (SYMPLICITY-HTN3), have demonstrated contradictory results for the effectiveness of RDN in resistant hypertension (HTN). In the treatment of HTN, individuals with primary HTN are expected to experience greater benefits compared to those with secondary HTN due to the diverse underlying causes of secondary HTN. Beyond its application for HTN, RDN has also found utility in addressing cardiac arrhythmias, such as atrial fibrillation, and managing cases of heart failure. Non-cardiogenic applications of RDN include reducing the intensity of obstructive sleep apnea (OSA), overcoming insulin resistance, and in chronic kidney disease (CKD) patients. This article aims to provide a comprehensive review of RDN and its uses in cardiology and beyond, along with providing future directions and perspectives.

The Implementation of Renal Denervation in the Management of Resistant Hypertension Despite Use of Multitherapy Antihypertensives at Maximally Tolerated Doses: A Contemporary Literature Review

Refractory hypertension is highly prevalent among the hypertensive population, and current clinical management has failed to provide optimal control for these individuals. This subtype of arterial hypertension is defined as a persistently elevated systolic blood pressure reading of 140 mmHg, or higher, despite multiple antihypertensive use at maximally tolerated dosing. These patients have an elevated risk of cardiovascular and renal complications, urging for the need of more effective therapeutic management. Renal sympathetic efferent nerves have been noted to play an important role in volume and blood pressure homeostasis. Before the implementation of oral antihypertensives, the use of surgical lumbar sympathectomy for the reduction of persistent hypertension was considered a life-saving approach. However, individuals were left with debilitating side effects, such as postural hypotension, syncope, and impotence. A new and minimally invasive technique has been proposed, where the kidneys undergo selective denervation in hopes of providing decreased cardiovascular morbidity and mortality for patients with resistant hypertension. Some studies demonstrated promising outcomes with a reduction in blood pressure, a decrease in medication reliance, and a potential long-lasting effect of the procedure with an overall improvement in cardiovascular health. Unfortunately, most of the available data was obtained from observational, uncontrolled studies with short-term follow-up, small sample sizes, and high variability in blood pressure measurement. Therefore, further evidence is needed to determine whether renal denervation provides long-term benefits for blood pressure control and improves outcomes for mortality and cardiovascular events in this patient population.

Multi-organ denervation: a novel approach to combat cardiometabolic disease

Cardiometabolic disorders are associated with a substantial loss in quality of life and pose a large burden on healthcare systems worldwide. Overactivation of the sympathetic nervous system has been shown to be a key player in several aspects relating to cardiometabolic disturbances. While diet- and exercise-induced approaches to help reduce weight remains the main strategy to combat metabolic disorders, this is often difficult to achieve. Current pharmacological approaches result in variable responses in different patient cohorts and long-term efficacy may be limited by medication side effects and non-adherence in the long term. There is a clear clinical need for complementary therapies to curb the burden of cardiometabolic disease. One such approach may include interventional sympathetic neuromodulation of organs relevant to cardiometabolic control. Data from sham-controlled clinical trials demonstrate the feasibility, safety and efficacy of catheter-based renal denervation. In analogy, denervation of the common hepatic artery is now feasible in humans and may prove to be similarly useful in modulating sympathetic overdrive directed towards the liver, pancreas and duodenum. Such a targeted multi-organ neuromodulation strategy may beneficially influence multiple aspects of the cardiometabolic disease continuum including blood pressure, glucose and lipid control.

Effect of Vitamin D Supplementation on the Regulation of Blood Pressure in Iranian Patients with Essential Hypertension: A Clinical Trial

BACKGROUND

Low serum vitamin D level is associated with both high blood pressure and incidence of primary hypertension. Experimental studies suggest that vitamin D supplements may reduce blood pressure.

OBJECTIVE

The aim of this study was to investigate whether vitamin D supplementation reduces systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) in Iranian patients with essential hypertension.

METHOD

A total of 173 patients with essential hypertension participated in this open-label clinical trial. SBP, DBP, and serum vitamin D levels were measured at baseline and at the end of the study. Vitamin D was administered at a dose of 50,000 IU/week, and 1000 IU/day in patients with serum vitamin D levels <20 ng/mL and 20-30 ng/mL, respectively, for 8 weeks.

RESULTS

Based on serum vitamin D levels, 45.1%, 17.3%, and 29.5% of patients were deficient, insufficient, and sufficient for vitamin D intake, respectively. Baseline serum levels of vitamin D were not correlated with SBP, DBP, and MAP at the beginning of the study (p = ns). Multiple logistic regression analysis revealed that the risk of vitamin D deficiency was 2.5-fold times higher in women than in men (p = 0.03). After 8 weeks of supplementation with vitamin D, mean SBP and MAP were significantly reduced by 5.5 ± 16.16 (p = 0.01) and 3.7 ± 9.24 (p = 0.004) mmHg, respectively. Neither sex nor age could significantly predict BP response to vitamin D supplementation.

CONCLUSION

Vitamin D supplementation may significantly reduce SBP and MAP but not DBP in patients with essential hypertension.

Renal denervation for resistant hypertension

BACKGROUND

Resistant hypertension is highly prevalent among the general hypertensive population and the clinical management of this condition remains problematic. Different approaches, including a more intensified antihypertensive therapy, lifestyle modifications or both, have largely failed to improve patients' outcomes and to reduce cardiovascular and renal risk. As renal sympathetic hyperactivity is a major driver of resistant hypertension, in the last decade renal sympathetic ablation (renal denervation) has been proposed as a possible therapeutic alternative to treat this condition.

OBJECTIVES

We sought to evaluate the short- and long-term effects of renal denervation in individuals with resistant hypertension on clinical end points, including fatal and non-fatal cardiovascular events, all-cause mortality, hospital admissions, quality of life, blood pressure control, left ventricular hypertrophy, cardiovascular and metabolic profile and kidney function, as well as the potential adverse events related to the procedure.

SEARCH METHODS

For this updated review, the Cochrane Hypertension Information Specialist searched the following databases for randomised controlled trials up to 3 November 2020: Cochrane Hypertension's Specialised Register, CENTRAL (2020, Issue 11), Ovid MEDLINE, and Ovid Embase. The World Health Organization International Clinical Trials Registry Platform (via CENTRAL) and the US National Institutes of Health Ongoing Trials Register ClinicalTrials.gov were searched for ongoing trials. We also contacted authors of relevant papers regarding further published and unpublished work. The searches had no language restrictions.

SELECTION CRITERIA

We considered randomised controlled trials (RCTs) that compared renal denervation to standard therapy or sham procedure to treat resistant hypertension, without language restriction.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed study risk of bias. We summarised treatment effects on available clinical outcomes and adverse events using random-effects meta-analyses. We assessed heterogeneity in estimated treatment effects using Chi² and I² statistics. We calculated summary treatment estimates as a mean difference (MD) or standardised mean difference (SMD) for continuous outcomes, and a risk ratio (RR) for dichotomous outcomes, together with their 95% confidence intervals (CI). Certainty of evidence has been assessed using the GRADE approach.

MAIN RESULTS

We found 15 eligible studies (1416 participants). In four studies, renal denervation was compared to sham procedure; in the remaining studies, renal denervation was tested against standard or intensified antihypertensive therapy. Most studies had unclear or high risk of bias for allocation concealment and blinding.  When compared to control, there was low-certainty evidence that renal denervation had little or no effect on the risk of myocardial infarction (4 studies, 742 participants; RR 1.31, 95% CI 0.45 to 3.84), ischaemic stroke (5 studies, 892 participants; RR 0.98, 95% CI 0.33 to 2.95), unstable angina (3 studies, 270 participants; RR 0.51, 95% CI 0.09 to 2.89) or hospitalisation (3 studies, 743 participants; RR 1.24, 95% CI 0.50 to 3.11). Based on moderate-certainty evidence, renal denervation may reduce 24-hour ambulatory blood pressure monitoring (ABPM) systolic BP (9 studies, 1045 participants; MD -5.29 mmHg, 95% CI -10.46 to -0.13), ABPM diastolic BP (8 studies, 1004 participants; MD -3.75 mmHg, 95% CI -7.10 to -0.39) and office diastolic BP (8 studies, 1049 participants; MD -4.61 mmHg, 95% CI -8.23 to -0.99). Conversely, this procedure had little or no effect on office systolic BP (10 studies, 1090 participants; MD -5.92 mmHg, 95% CI -12.94 to 1.10). Moderate-certainty evidence suggested that renal denervation may not reduce serum creatinine (5 studies, 721 participants, MD 0.03 mg/dL, 95% CI -0.06 to 0.13) and may not increase the estimated glomerular filtration rate (eGFR) or creatinine clearance (6 studies, 822 participants; MD -2.56 mL/min, 95% CI -7.53 to 2.42).  AUTHORS' CONCLUSIONS: In patients with resistant hypertension, there is low-certainty evidence that renal denervation does not improve major cardiovascular outomes and renal function. Conversely, moderate-certainty evidence exists that it may improve 24h ABPM and diastolic office-measured BP. Future trials measuring patient-centred instead of surrogate outcomes, with longer follow-up periods, larger sample size and more standardised procedural methods are necessary to clarify the utility of this procedure in this population.

Effect of Renal Denervation on Cardiac Function and Inflammatory Factors in Heart Failure After Myocardial Infarction

Supplemental Digital Content is Available in the Text.

Heart failure (HF) affects around 100 million people and is a staggering burden for health care system worldwide. Rapid and sustained activation of inflammatory response is an important feature of HF after myocardial infarction. Sympathetic overactivation is also an important factor in the occurrence and progression of HF. The beneficial effect of renal denervation (RDN) has been demonstrated in HF. In the current study, we hypothesized that RDN improves cardiac function in HF canine models due to acute myocardial infarction (AMI) and reduced inflammation might be involved. Twenty-four beagles were randomized into the control (n = 8), HF (n = 8), and HF + RDN group (n = 8). The HF model after AMI was established by embolization the anterior descending distal artery with anhydrous ethanol in the HF and HF + RDN group. Bilateral renal artery ablation was performed in the HF + RDN group. Cardiac function, serum creatine kinase, creatine kinase-MB and NT-Pro BNP level, and expression of inflammation-related proteins in myocardial were examined. Because the paraventricular nucleus of the hypothalamus might be involved in inflammation-induced central neural excitation in HF and plays an important role in regulating extracellular fluid volume and sympathetic activity, expression of inflammation-related proteins in hypothalamus was also examined. AMI and post-AMI HF model was created successfully. Compared with the HF group, dogs in the HF + RDN group showed better cardiac function 4 weeks after AMI: lower left ventricular end-diastolic pressure, left ventricular end-diastolic dimension, and left ventricular end-systolic dimension and higher LEVF and left ventricular systolic pressure (P < 0.05 for all) were observed in the HF + RDN group. In addition, dogs in the HF + RDN group had slightly less ventricular fibrosis. Interestingly, RDN had lower expression of inflammation-related proteins including interleukin-6, tumor necrosis factors-α, nuclear factor κB, and monocyte chemotactic protein 1 (P < 0.05 for all) in both myocardial tissue and hypothalamus. RDN can improve cardiac function in dogs with HF after myocardial infarction. Our results suggested that RDN might affect cytokine-induced central neural excitation in HF and later affect sympathetic activity. Our results suggested a potential beneficial mechanism of RDN independent of mechanism involving renal afferent and efferent sympathetic nerves.

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.

A Pilot Study of Perioperative External Circumferential Cryoablation of Human Renal Arteries for Sympathetic Denervation

Purpose

Cryoablation, which induces cellular death without extensive tissue damage, has been extensively used to denervate the myocardium. However, periadventitial external circumferential application of cryotherapy to denervate the renal artery sympathetic nerves has, to our knowledge, never been tested in humans. The main aim of this study was to examine the safety and potential effects of cryotherapy on ambulatory blood pressure levels and other outcomes that are indirectly related to sympathetic tone, including pulse-wave velocity, central pulse pressure, and glucose levels.

Materials and Methods

Five patients who underwent the denervation of the renal arteries during open surgery of the abdominal aortic aneurysm and four controls who did not undergo denervation during the surgery were enrolled. An argon-powered cryotherapy catheter (Cardioblate; Medtronic Inc., USA) was applied periadventitially to each renal artery in the five patients and then activated by infusion with liquid nitrogen for 1 minute.

Results

No cryoablation-related complications occurred in the five consecutive patients. Their ambulatory blood pressures 3 to 5 months after surgery did not demonstrate any general blood pressure-reducing effects, but two patients responded favorably with the reduction of antihypertensive medication and decreased 24-hour blood pressure. The patients’ mean HbA1C levels decreased from 5.9±0.78% to 5.6±0.71% (P=0.042).

Conclusion

This pilot study suggests that periadventitial cryoablation during open surgery can be used in the study of renal denervation in humans, as it had no complications in five patients in this study. The effectiveness of cryoablation for treating hypertension should be proven in a phase II clinical trial.

Effects of different ablation points of renal denervation on the efficacy of resistant hypertension

Objective

To explore the blood pressure response to different ablation points of renal denervation (RDN) in patients with resistant hypertension

Methods

A total of 42 cases with resistant hypertension treated by RDN in our center from 2013 to 2015 were retrospectively analyzed. The patients were divided into two groups according to the different ablation points of RDN: the standard treatment group (spiral ablation from near to proximal, with less than 8 points per artery) and the intensive treatment group (from near to far by spiral ablation, with at least 8 points per artery), with 21 patients in each group. The ablation parameters, including points, impedance, actual wattage, and actual temperature, were recorded intraoperatively. Renal angiography was performed again after RDN. Ambulatory blood pressure (ABP) images were taken for all patients at the baseline and 6 months after operation.

Results

The mean 24-h blood pressure of the standard treatment group was lower than that of the baseline (24-h systolic blood pressure decreased by 7.4 ± 10.6 mmHg and 24-h diastolic blood pressure decreased by 4.6  ± 6.1 mmHg), and the mean 24-h blood pressure decreased significantly from baseline to 6 months in the intensive treatment group (24–h systolic blood pressure decreased by 27.4 ±  11.4 mmHg, P < 0.0001; 24–h diastolic blood pressure decreased by 10.9 ±  9.6 mmHg, P = 0.005). There was a positive correlation between the decrease of systolic/diastolic 24-hour mean and the number of ablation points used in the procedure. The mean value of systolic and diastolic blood pressure was positively correlated with ablation points at 24-hour (R² = 0.777 and 0.633 respectively, P < 0.01). There were no adverse events in either group after the operation and during the follow-up.

Conclusions

RDN could significantly reduce BP in patients with resistant hypertension. Our study showed that the antihypertensive effect appeared to be positively correlated with the number of ablation points.

Impact of high blood pressure variability on the occurrence of acute type B aortic dissection

Background

Acute type B aortic dissection is a life-threatening medical emergency, and hypertension is believed to be an important predictor of aortic dissection; the impact of blood pressure variability on the onset and development of aortic dissection has attracted increasing attention.

Methods

A total of 120 acute type B aortic dissection patients and 57 hypertensive patients without aortic dissection were consecutively enrolled and retrospectively reviewed between January 2013 and November 2015. There were 60 acute type B aortic dissection patients in both high and low blood pressure variability groups.

Results

Blood pressure variability showed higher diagnostic value than hypertension in aortic dissection, and the best threshold of blood pressure variability is 5.71 mmHg. By performing multivariable logistic regression, we found that the history of hypertension was likely to be a risk factor of blood pressure variability (95% CI: 1.155–6.422, P = 0.022). Nine patients from high blood pressure variability group and two from low blood pressure variability group ( χ2 = 4.90, P = 0.027) received emergency surgery within 24 hours after admission. The presence of multiple tears (>2, 55.0% vs. 45.0%, P = 0.001), configuration of the false lumen (spiral false lumen) (50.0% vs. 21.7%, P = 0.001), the diameter of the false lumen (49.6 ± 15.0 mm vs. 37.6 ± 10.8 mm, P < 0.001), the false/true lumen ratio (1.53 ± 1.02 vs. 0.929 ± 0.733, P < 0.001), and the number of visceral arteries involved (1.75 ± 0.942 vs. 0.800 ± 0.927, P < 0.001) showed significant differences between high and low blood pressure variability groups. Nine (30%) patients from the high blood pressure variability group showed a maximum diameter of false lumen over 60 mm, while none was found in the low blood pressure variability group.

Conclusions

High blood pressure variability, the presence of multiple tears (>2), the configuration of false lumen, the diameter of the false lumen, false/true lumen ratio, and the number of visceral arteries involved were independent risk factors for acute type B aortic dissection.

Renal Inflammation in DOCA-Salt Hypertension

Recent reports indicate that, in addition to treating hypertension, renal denervation (RDN) also mitigates renal inflammation. However, because RDN decreases renal perfusion pressure, it is unclear whether these effects are because of the direct effects of RDN on inflammatory signaling or secondary to decreased arterial pressure (AP). Therefore, this study was conducted to elucidate the contribution of renal nerves to renal inflammation in the deoxycorticosterone (DOCA)-salt rat, a model in which RDN decreases AP and abolishes renal inflammation. In Experiment 1, we assessed the temporal changes in renal inflammation by measuring renal cytokines and AP in DOCA-salt rats. Uninephrectomized (1K) adult male Sprague Dawley rats that received surgical RDN or sham (Sham) were administered DOCA (100 mg, SC) and 0.9% saline for 21 days. AP was measured by radiotelemetry, and urinary cytokine excretion was measured repeatedly. In Experiment 2, the contribution of renal nerves in renal inflammation was assessed in a 2-kidney DOCA-salt rat to control for renal perfusion pressure. DOCA-salt treatment was administered after unilateral (U-)RDN. In Experiment 1, DOCA-salt-induced increases in AP and renal inflammation (assessed by urinary cytokines) were attenuated by RDN versus Sham. In Experiment 2, GRO/KC (growth-related oncogene/keratinocyte chemoattractant), MCP (monocyte chemoattractant protein)-1, and macrophage infiltration were lower in the denervated kidney versus the contralateral Sham kidney. No differences in T-cell infiltration were observed. Together, these data support the hypothesis that renal nerves mediate, in part, the development of renal inflammation in the DOCA-salt rat independent of hypertension. The mechanisms and cell-specificity mediating these effects require further investigation.

Renal denervation in patients with heart failure secondary to Chagas' disease: A pilot randomized controlled trial

INTRODUCTION

Chagas disease is one of the most relevant endemic parasitic diseases in Latin America, affecting approximately 6 million people. Overt Chagas heart disease is an ominous condition, occurring in 20-30% of infected individuals, which has besides the persistent myocarditis a peculiar intracardiac ganglionic neuronal depletion and dysautonomy. This study aims to evaluate the safety and feasibility of renal denervation for patients with advanced symptomatic Chagas cardiomyopathy.

METHODS

Open-label prospective pilot study that randomized patients with Chagas heart disease to either renal denervation or conservative treatment (2:1 ratio). The primary endpoint was the incidence of major adverse events at 9 months, defined as a composite of all-cause death, myocardial infarction, stroke, need for renal artery invasive treatment, or worsening renal function.

RESULTS

A total of 17 patients were allocated for renal denervation (n = 11) or conservative treatment (n = 6). Included patients had severe symptomatic heart disease, with markedly depressed left ventricular function (average ejection fraction 26.7 ± 4.9%). For patients randomized to renal denervation, the procedure was performed successfully and uneventfully. After 9 months, the primary endpoint occurred in 36.4% of patients in the renal denervation group and 50.0% in the control arm (p = .6). After 9 months, clinical, laboratory, functional, echocardiographic, and quality of life parameters were similar between groups.

CONCLUSIONS

This pilot study suggests that renal denervation is safe and feasible in patients with Chagas cardiomyopathy, warranting future studies to better evaluate the clinical efficacy of the interventional strategy in improving the prognosis of this high-risk population.

Catheter-Based Renal Denervation Attenuates Kidney Interstitial Fibrosis in a Canine Model of High-Fat Diet-Induced Hypertension

BACKGROUND/AIMS

Catheter-based renal denervation (RDN) has emerged as an innovative interventional approach for reducing blood pressure (BP), suppressing ventricular substrate remodeling, and attenuating heart failure, which suggests that it might reduce kidney fibrosis in a canine model of high-fat diet-induced hypertension. This study thus sought to assess whether RDN could reduce kidney fibrosis and halt the progression of renal impairment in a canine model of high-fat diet-induced hypertension.

METHODS

Thirty-two beagles were randomized into either the normal control group (normal diet, n = 10) or the hypertension group (high-fat diet, n = 22). After successful establishment of the model, the hypertension model group was randomized to either the RDN group (n = 9) or the sham-surgery group (n = 8). Renal artery angiography, BP, heart rate (HR), and blood and urine biochemistry results were assessed at 1, 3, and 6 months after surgery. Canines were sacrificed at 6 months after surgery. The extent of kidney interstitial fibrosis, transforming growth factor-beta 1, alpha-smooth muscle actin, connective tissue growth factor, and E-cadherin protein were measured.

RESULTS

The group fed a high-fat diet had significantly (p ˂ 0.05) increased body weight, BP, and HR and higher levels of urine albumin, serum noradrenaline (NE), and angiotensin II (AngII) than the control group. The sham-surgery group and RDN group also had higher levels than the control group (p ˂ 0.05). Compared with the sham-surgery group, the RDN group had lower BP, urine albumin, serum NE, and AngII and less fibrotic tissue (all p ˂ 0.05).

CONCLUSION

RDN reduced BP, slowed progression of albuminuria, and suppressed renal remodeling in a canine model of high-fat diet-induced hypertension.

Renal sympathetic denervation for treatment of hypertension: where are we now in 2019?

PURPOSE OF REVIEW

Although sound physiological principles and surgical precedent underpin renal denervation as a therapy for treatment resistant hypertension, and early clinical studies had produced encouraging results, the first sham-controlled study (SYMPLICITY HTN-3) failed to achieve its primary efficacy endpoint. Lessons learnt from this trial, and the knowledge derived from further animal and autopsy work, have been applied in three recently published sham-controlled trials.

RECENT FINDINGS

These trials - SPYRAL OFF-MED, RADIANCE SOLO and SPYRAL ON-MED - using newer technologies, demonstrate a 5-10 mmHg incremental reduction in ambulatory SBP from RDN against sham-control, in patients with mild-to-moderate hypertension taking 0-3 drugs.

SUMMARY

These results provide proof of principle of the blood pressure-lowering effect of renal denervation. We now require data on long-term safety and durability of the procedure. Research is needed to identify predictive markers of response as about one-third of individuals do not respond to renal denervation. Hard-outcome data would be welcome but might be difficult to acquire. Individuals with treatment resistance are obvious treatment candidates, but RDN may also potentially benefit those with medication nonadherence and/or intolerance and those unwilling to take pills.

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.

Targeted afferent renal denervation reduces arterial pressure but not renal inflammation in established DOCA-salt hypertension in the rat

Recent preclinical studies show renal denervation (RDNx) may be an effective treatment for hypertension; however, the mechanism remains unknown. We have recently reported total RDNx (TRDNx) and afferent-selective RDNx (ARDNx) similarly attenuated the development of deoxycorticosterone acetate (DOCA)-salt hypertension. Whereas TRDNx abolished renal inflammation, ARDNx had a minimal effect despite an identical antihypertensive effect. Although this study established that ARDNx attenuates the development of DOCA-salt hypertension, it is unknown whether this mechanism remains operative once hypertension is established. The current study tested the hypothesis that TRDNx and ARDNx would similarly decrease mean arterial pressure (MAP) in the DOCA-salt hypertensive rat, and only TRDNx would mitigate renal inflammation. After 21 days of DOCA-salt treatment, male Sprague-Dawley rats underwent TRDNx ( n = 16), ARDNx ( n = 16), or Sham ( n = 14) treatment and were monitored for 14 days. Compared with baseline, TRDNx and ARDNx decreased MAP similarly (TRDNx -14 ± 4 and ARDNx -15 ± 6 mmHg). After analysis of diurnal rhythm, rhythm-adjusted mean and amplitude of night/day cycle were also reduced in TRDNx and ARDNx groups compared with Sham. Notably, no change in renal inflammation, injury, or function was detected with either treatment. We conclude from these findings that: 1) RDNx mitigates established DOCA-salt hypertension; 2) the MAP responses to RDNx are primarily mediated by ablation of afferent renal nerves; and 3) renal nerves do not contribute to the maintenance of renal inflammation in DOCA-salt hypertension.

Role of afferent and efferent renal nerves in the development of AngII-salt hypertension in rats

Hypertension is the leading modifiable risk factor for death worldwide, yet the causes remain unclear and treatment remains suboptimal. Catheter-based renal denervation (RDNX) is a promising new treatment for resistant hypertension, but the mechanisms underlying its antihypertensive effect remain unclear. We recently found that RDNX attenuates deoxycorticosterone acetate-salt hypertension and that this is dependent on ablation of afferent renal nerves and is associated with decreased renal inflammation. To determine if this is common to other models of salt-sensitive hypertension, rats underwent complete RDNX (n = 8), selective ablation of afferent renal nerves (n = 8), or sham denervation (n = 8). Mean arterial pressure (MAP) and heart rate were measure by telemetry and rats were housed in metabolic cages for measurement of sodium and water balance. Rats were then subjected to angiotensin II (AngII)-salt hypertension (10 ng/kg/min, intravenous + 4% NaCl diet) for 2 weeks. At the end of the study, renal T-cell infiltration was quantified by flow cytometry. AngII resulted in an increase in MAP of ~50 mmHg in all three groups with no between group differences, and a transient bradycardia that was blunted by selective ablation of afferent renal nerves. Sodium and water balance were unaffected by AngII-salt treatment and similar between groups. Lastly, AngII infusion was not associated with T-cell infiltration into the kidneys, and T-cell counts were unaffected by the denervation procedures. These results suggest that AngII-salt hypertension in the rat is not associated with renal inflammation and that neither afferent nor efferent renal nerves contribute to this model.

Effects of Renal Denervation on Cardiac Structural and Functional Abnormalities in Patients with Resistant Hypertension or Diastolic Dysfunction

The aim of the present study is to systematically evaluate the impact of RDN on cardiac structure and function in patients with resistant hypertension (RH) or diastolic dysfunction. We retrieved Pubmed, Embase and Cocharane Library databases, from inception to April 1^st, 2016. Studies reporting left ventricular mass (LVMI) or left ventricular (LV) diastolic function (reflected by the ratio of mitral inflow velocity to annular relaxation velocity [E/e’]) responses to RDN were included. Two randomized controlled trials (RCTs), 3 controlled studies and 11 uncontrolled studies were finally identified. In observational studies, there was a reduction in LVMI, E/e’ and N-terminal pro B-type natriuretic peptide (BNP) at 6 months, compared with pre-RDN values. LV ejection fraction (LVEF) elevated at 6 months following RDN. In RCTs, however, no significant change in LVMI, E/e’, BNP, left atrial volume index or LVEF was observed at 12 months, compared with pharmaceutical therapy. In summary, both LV hypertrophy and cardiac function improved at 6 months after RDN. Nonetheless, current evidence failed to show that RDN was superior to intensive (optimal) drug therapy in improving cardiac remodeling and function.

Renal sympathetic denervation lowers arterial pressure in canines with obesity-induced hypertension by regulating GAD65 and AT1R expression in rostral ventrolateral medulla

To explore the roles of glutamate acid decarboxylase 65 (GAD65) and angiotensin II type 1 receptor (AT₁R) in the action of renal sympathetic denervation (RSD) on obesity-induced hypertension in canines. Thirty-two beagles were randomly divided into a hypertensive model (n = 22) and control (n = 10) groups. A hypertensive canine model was established by feeding a high-fat diet. Twenty hypertensive beagles were randomized equally to a sham-surgery and RSD-treated group receiving catheter-based radiofrequency RSD. Compared with the control group, the sham-surgery group exhibited significant increases in blood pressure, serum angiotensin II level, rostral ventrolateral medulla (RVLM) glutamate level, and AT₁R mRNA and protein expression and decreases in γ-amino acid butyric acid (γ-GABA) level and GAD65 mRNA and protein expression in the RVLM (all P < 0.05). Treatment with RSD significantly attenuated the above abnormal alterations (all P < 0.05). Linear correlation analysis revealed that angiotensin II level was positively correlated with glutamate level (r = 0.804) and inversely correlated with γ-GABA level (r = -0.765). GAD65 protein expression was positively correlated with γ-GABA level (r = 0.782). Catheter-based radiofrequency RSD can decrease blood pressure in obesity-induced hypertensive canines. The antihypertensive mechanism might be linked to upregulation of GAD65 and downregulation of AT₁R in the RVLM.

Procedural Reassessment of Radiofrequency Renal Denervation in Resistant Hypertensive Patients

INTRODUCTION

Recent anatomical and clinical studies have led to the hypothesis that in several cases of failure of response to renal denervation (RDN), the procedure has not been technically correct.

AIM

To perform procedural reassessment in patients with true resistant hypertension who underwent RDN.

METHODS

We retrospectively reassessed the procedural technique of RDN in 10 true resistant hypertensive patients, comparing the sites of renal ablations with the knowledge of animal and human post mortem evidences. Procedural ablation technique was assessed in terms of number of ablations for each renal artery and site of ablation (quadrant and distance from renal ostium) by using the radiologic images of each RDN and the number of radiofrequency ablation attempts documented in the reports of each denervation session.

RESULTS

10 patients were studied, 9 denervated with Simplicity monoelectrode catheter, 1 with multielectrode balloon technique. Responders to the procedure underwent more ablations and particularly at least a quadrant ablation in one of the kidney arteries, >2 ablations in Dorsal plus Ventral quadrants and in 67% of then >10 ablations were done in superior inferior and ventral quadrants.

CONCLUSION

This study confirms the importance of a well knowledge of renal artery anatomy and underlines the relevance of the choice of ablation sites in order to obtain a successful RDN procedure.

Renal vascular calcification and response to renal nerve denervation in resistant hypertension

Renal sympathetic nerve denervation (RDN) is accepted as a treatment option for patients with resistant hypertension. However, results on decline in ambulatory blood pressure (BP) measurement (ABPM) are conflicting. The high rate of nonresponders may be related to increased systemic vascular stiffness rather than sympathetic overdrive. A single center, prospective registry including 26 patients with treatment resistant hypertension who underwent RDN at the Isala Hospital in the Netherlands. Renal perivascular calcium scores were obtained from noncontrast computed tomography scans. Patients were divided into 3 groups based on their calcium scores (group I: low 0-50, group II: intermediate 50-1000, and group III: high >1000). The primary end point was change in 24-hour ABPM at 6 months follow-up post-RDN compared to baseline. Seven patients had low calcium scores (group I), 13 patients intermediate (group II), and 6 patients had high calcium scores (group III). The groups differed significantly at baseline in age and baseline diastolic 24-hour ABPM. At 6-month follow-up, no difference in 24-hour systolic ABPM response was observed between the 3 groups; a systolic ABPM decline of respectively -9 ± 12, -6 ± 12, -12 ± 10 mm Hg was found. Also the decline in diastolic ambulatory and office systolic and diastolic BP was not significantly different between the 3 groups at follow-up. Our preliminary data showed that the extent of renal perivascular calcification is not associated with the ABPM response to RDN in patients with resistant hypertension.

Blood Pressure Increase during Oxygen Supplementation in Chronic Kidney Disease Patients Is Mediated by Vasoconstriction Independent of Baroreflex Function

Renal hypoxia is thought to be an important pathophysiological factor in the progression of chronic kidney disease (CKD) and the associated hypertension. In a previous study among CKD patients, supplementation with 100% oxygen reduced sympathetic nerve activity (SNA) and lowered blood pressure (BP). We aimed to assess the underlying haemodynamic modulation and hypothesized a decreased systemic vascular resistance (SVR). To that end, 19 CKD patients were studied during 15-min intervals of increasing partial oxygen pressure (ppO₂) from room air (0.21 ATA) to 1.0 ATA and further up to 2.4 ATA, while continuously measuring finger arterial blood pressure (Finapres). Off-line, we derived indexes of SVR, cardiac output (CO) and baroreflex sensitivity from the continuous BP recordings (Modelflow). During oxygen supplementation, systolic, and diastolic BP both increased dose-dependently from 128 ± 24 and 72 ± 19 mmHg respectively at baseline to 141 ± 23 (p < 0.001) and 80 ± 21 mmHg (p < 0.001) at 1.0 ATA oxygen. Comparing baseline and 1.0 ATA oxygen, SVR increased from 1440 ± 546 to 1745 ± 710 dyn·s/cm⁵ (p = 0.009), heart rate decreased from 60 ± 8 to 58 ± 6 bpm (p < 0.001) and CO from 5.0 ± 1.3 to 4.6 ± 1.1 L/min (p = 0.02). Baroreflex sensitivity remained unchanged (13 ± 13 to 15 ± 12 ms/mmHg). These blood pressure effects were absent in a negative control group of eight young healthy subjects. We conclude that oxygen supplementation in CKD patients causes a non-baroreflex mediated increased in SVR and blood pressure.

Effects and Mechanisms of Radiofrequency Ablation of Renal Sympathetic Nerve on Anti-Hypertension in Canine

Background

Radiofrequency ablation of renal sympathetic nerve (RDN) shows effective BP reduction in hypertensive patients while the specific mechanisms remain unclear.

Objective

We hypothesized that abnormal levels of norepinephrine (NE) and changes in NE-related enzymes and angiotensinconverting enzyme 2 (ACE2), angiotensin (Ang)-(1-7) and Mas receptor mediate the anti-hypertensive effects of RDN.

Methods

Mean values of systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP) were assessed at baseline and follow-up. Plasma and renal norepinephrine (NE) concentrations were determined using highperformance liquid chromatography with electrochemical detection, and levels of NE-related enzyme and ACE2-Ang(1-7)- Mas were measured using real time PCR, Western blot and immunohistochemistry or Elisa in a hypertensive canine model fed with high-fat diet and treated with RDN. The parameters were also determined in a sham group treated with renal arteriography and a control group fed with normal diet.

Results

RDN decreased SBP, DBP, MAP, plasma and renal NE. Compared with the sham group, renal tyrosine hydroxylase (TH) expression was lower and renalase expression was higher in the RDN group. Compared with the control group, renal TH and catechol-o-methyl transferase (COMT) were higher and renalase was lower in the sham group. Moreover, renal ACE2, Ang-(1-7) and Mas levels of the RDN group were higher than those of the sham group, which were lower than those of the control group.

Conclusion

RDN shows anti-hypertensive effect with reduced NE and activation of ACE2-Ang(1-7)-Mas, indicating that it may contribute to the anti-hypertensive effect of RDN.

Renal denervation for resistant hypertension

BACKGROUND

Resistant hypertension is highly prevalent among the general hypertensive population and the clinical management of this condition remains problematic. Different approaches, including a more intensified antihypertensive therapy, lifestyle modifications, or both, have largely failed to improve patients' outcomes and to reduce cardiovascular and renal risk. As renal sympathetic hyperactivity is a major driver of resistant hypertension, renal sympathetic ablation (renal denervation) has been recently proposed as a possible therapeutic alternative to treat this condition.

OBJECTIVES

We sought to evaluate the short- and long-term effects of renal denervation in individuals with resistant hypertension on clinical end points, including fatal and non-fatal cardiovascular events, all-cause mortality, hospital admissions, quality of life, blood pressure control, left ventricular hypertrophy, cardiovascular and metabolic profile, and kidney function, as well as the potential adverse events related to the procedure.

SEARCH METHODS

We searched the following databases to 17 February 2016 using relevant search terms: the Cochrane Hypertension Group Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and ClinicalTrials.gov SELECTION CRITERIA: We considered randomised controlled trials (RCTs) that compared renal denervation to standard therapy or sham procedure to treat resistant hypertension, without language restriction.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed study risks of bias. We summarised treatment effects on available clinical outcomes and adverse events using random-effects meta-analyses. We assessed heterogeneity in estimated treatment effects using Chi² and I² statistics. We calculated summary treatment estimates as a mean difference (MD) or standardised mean difference (SMD) for continuous outcomes, and a risk ratio (RR) for dichotomous outcomes, together with their 95% confidence intervals (CI).

MAIN RESULTS

We found 12 eligible studies (1149 participants). In four studies, renal denervation was compared to sham procedure; one study compared a proximal ablation to a complete renal artery denervation; in the remaining, renal denervation was tested against standard or intensified antihypertensive therapy.None of the included trials was designed to look at hard clinical end points as primary outcomes.When compared to control, there was low quality evidence that renal denervation did not reduce the risk of myocardial infarction (4 studies, 742 participants; RR 1.31, 95% CI 0.45 to 3.84), ischaemic stroke (4 studies, 823 participants; RR 1.15, 95% CI 0.36 to 3.72), or unstable angina (2 studies, 201 participants; RR 0.63, 95% CI 0.08 to 5.06), and moderate quality evidence that it had no effect on 24-hour ambulatory blood pressure monitoring (ABPM) systolic BP (5 studies, 797 participants; MD 0.28 mmHg, 95% CI -3.74 to 4.29), diastolic BP (4 studies, 756 participants; MD 0.93 mmHg, 95% CI -4.50 to 6.36), office measured systolic BP (6 studies, 886 participants; MD -4.08 mmHg, 95% CI -15.26 to 7.11), or diastolic BP (5 studies, 845 participants; MD -1.30 mmHg, 95% CI -7.30 to 4.69). Furthermore, low quality evidence suggested that this procedure produced no effect on either serum creatinine (3 studies, 736 participants, MD 0.01 mg/dL; 95% CI -0.12 to 0.14), estimated glomerular filtration rate (eGFR), or creatinine clearance (4 studies, 837 participants; MD -2.09 mL/min, 95% CI -8.12 to 3.95). Based on low-quality evidence, renal denervation significantly increased bradycardia episodes compared to control (3 studies, 220 participants; RR 6.63, 95% CI 1.19 to 36.84), while the risk of other adverse events was comparable or not assessable.Data were sparse or absent for all cause mortality, hospitalisation, fatal cardiovascular events, quality of life, atrial fibrillation episodes, left ventricular hypertrophy, sleep apnoea severity, need for renal replacement therapy, and metabolic profile.The quality of the evidence was low for cardiovascular outcomes and adverse events and moderate for lack of effect on blood pressure and renal function.

AUTHORS' CONCLUSIONS

In patients with resistant hypertension, there is low quality evidence that renal denervation does not change major cardiovascular events, and renal function. There was moderate quality evidence that it does not change blood pressure and and low quality evidence that it caused an increaseof bradycardia episodes. Future trials measuring patient-centred instead of surrogate outcomes, with longer follow-up periods, larger sample size and more standardized procedural methods are necessary to clarify the utility of this procedure in this population.

Metabolic syndrome and the hepatorenal reflex

Insufficient hepatic O₂ in animal and human studies has been shown to elicit a hepatorenal reflex in response to increased hepatic adenosine, resulting in the stimulation of renal as well as muscle sympathetic nerve activity and activating the renin angiotensin system. Low hepatic ATP, hyperuricemia, and hepatic lipid accumulation reported in metabolic syndrome (MetS) patients may reflect insufficient hepatic O₂ delivery, potentially accounting for the sympathetic overdrive associated with MetS. This theoretical concept is supported by experimental results in animals fed a high fructose diet to induce MetS. Hepatic fructose metabolism rapidly consumes ATP resulting in increased adenosine production and hyperuricemia as well as elevated renin release and sympathetic activity. This review makes the case for the hepatorenal reflex causing sympathetic overdrive and metabolic syndrome in response to exaggerated splanchnic oxygen consumption from excessive eating. This is strongly reinforced by the fact that MetS is cured in a matter of days in a significant percentage of patients by diet, bariatric surgery, or endoluminal sleeve, all of which would decrease splanchnic oxygen demand by limiting nutrient contact with the mucosa and reducing the nutrient load due to loss of appetite or dietary restriction.

Renal Denervation

Sympathetic nervous system over-activity is closely linked with elevation of systemic blood pressure. Both animal and human studies suggest renal sympathetic nerves play an important role in this respect. Historically, modulation of sympathetic activity has been used to treat hypertension. More recently, catheter based renal sympathetic denervation was introduced for the management of treatment resistant hypertension. Sound physiological principles and surgical precedent underpin renal denervation as a therapy for treatment of resistant hypertension. Encouraging results of early studies led to a widespread adoption of the procedure for management of this condition. Subsequently a sham controlled randomised controlled study failed to confirm the benefit of renal denervation leading to a halt in its use in most countries in the world. However, critical analysis of the sham-controlled study indicates a number of flaws. A number of lessons have been learnt from this and other studies which need to be applied in future trials to ascertain the actual role of renal denervation in the management of treatment resistant hypertension before further implementation. This chapter deals with all these issues in detail.

Resting Afferent Renal Nerve Discharge and Renal Inflammation: Elucidating the Role of Afferent and Efferent Renal Nerves in Deoxycorticosterone Acetate Salt Hypertension

Renal sympathetic denervation (RDNx) has emerged as a novel therapy for hypertension; however, the therapeutic mechanisms remain unclear. Efferent renal sympathetic nerve activity has recently been implicated in trafficking renal inflammatory immune cells and inflammatory chemokine and cytokine release. Several of these inflammatory mediators are known to activate or sensitize afferent nerves. This study aimed to elucidate the roles of efferent and afferent renal nerves in renal inflammation and hypertension in the deoxycorticosterone acetate (DOCA) salt rat model. Uninephrectomized male Sprague-Dawley rats (275-300 g) underwent afferent-selective RDNx (n=10), total RDNx (n=10), or Sham (n=10) and were instrumented for the measurement of mean arterial pressure and heart rate by radiotelemetry. Rats received 100-mg DOCA (SC) and 0.9% saline for 21 days. Resting afferent renal nerve activity in DOCA and vehicle animals was measured after the treatment protocol. Renal tissue inflammation was assessed by renal cytokine content and T-cell infiltration and activation. Resting afferent renal nerve activity, expressed as a percent of peak afferent nerve activity, was substantially increased in DOCA than in vehicle (35.8±4.4 versus 15.3±2.8 %Amax). The DOCA-Sham hypertension (132±12 mm Hg) was attenuated by ≈50% in both total RDNx (111±8 mm Hg) and afferent-selective RDNx (117±5 mm Hg) groups. Renal inflammation induced by DOCA salt was attenuated by total RDNx and unaffected by afferent-selective RDNx. These data suggest that afferent renal nerve activity may mediate the hypertensive response to DOCA salt, but inflammation may be mediated primarily by efferent renal sympathetic nerve activity. Also, resting afferent renal nerve activity is elevated in DOCA salt rats, which may highlight a crucial neural mechanism in the development and maintenance of hypertension.

Metabolic syndrome and the hepatorenal reflex

Insufficient hepatic O₂ in animal and human studies has been shown to elicit a hepatorenal reflex in response to increased hepatic adenosine, resulting in stimulation of renal as well as muscle sympathetic nerve activity and activating the renin angiotensin system. Low hepatic ATP, hyperuricemia, and hepatic lipid accumulation reported in metabolic syndrome (MetS) patients may reflect insufficient hepatic O₂ delivery, potentially accounting for the sympathetic overdrive associated with MetS. This theoretical concept is supported by experimental results in animals fed a high fructose diet to induce MetS. Hepatic fructose metabolism rapidly consumes ATP resulting in increased adenosine production and hyperuricemia as well as elevated renin release and sympathetic activity. This review makes the case for the hepatorenal reflex causing sympathetic overdrive and metabolic syndrome in response to exaggerated splanchnic oxygen consumption from excessive eating. This is strongly reinforced by the fact that MetS is cured in a matter of days in a significant percentage of patients by diet, bariatric surgery, or endoluminal sleeve, all of which would decrease splanchnic oxygen demand by limiting nutrient contact with the mucosa and reducing the nutrient load due to the loss of appetite or dietary restriction.

Renal Nerve Stimulation–Induced Blood Pressure Changes Predict Ambulatory Blood Pressure Response After Renal Denervation

Blood pressure (BP) response to renal denervation (RDN) is highly variable and its effectiveness debated. A procedural end point for RDN may improve consistency of response. The objective of the current analysis was to look for the association between renal nerve stimulation (RNS)–induced BP increase before and after RDN and changes in ambulatory BP monitoring (ABPM) after RDN. Fourteen patients with drug-resistant hypertension referred for RDN were included. RNS was performed under general anesthesia at 4 sites in the right and left renal arteries, both before and immediately after RDN. RNS-induced BP changes were monitored and correlated to changes in ambulatory BP at a follow-up of 3 to 6 months after RDN. RNS resulted in a systolic BP increase of 50±27 mm Hg before RDN and systolic BP increase of 13±16 mm Hg after RDN ( P <0.001). Average systolic ABPM was 153±11 mm Hg before RDN and decreased to 137±10 mm Hg at 3- to 6-month follow-up ( P =0.003). Changes in RNS-induced BP increase before versus immediately after RDN and changes in ABPM before versus 3 to 6 months after RDN were correlated, both for systolic BP ( R =0.77, P =0.001) and diastolic BP ( R =0.79, P =0.001). RNS-induced maximum BP increase before RDN had a correlation of R =0.61 ( P =0.020) for systolic and R =0.71 ( P =0.004) for diastolic ABPM changes. RNS-induced BP changes before versus after RDN were correlated with changes in 24-hour ABPM 3 to 6 months after RDN. RNS should be tested as an acute end point to assess the efficacy of RDN and predict BP response to RDN.

Renal denervation, adjusted drugs, or combined therapy for resistant hypertension: A meta-regression

The objective of this study is to systematically evaluate the efficacy of renal denervation (RD), adjusted drugs, or combined therapy for resistant hypertension (RH) through a systematic review and meta-analysis of controlled studies.Publications were comprehensively searched. Studies that investigated the effects of RD and/or adjusted drugs in lowering blood pressure (BP) were included. After quality assessment and data extraction, subgroup analyzes were first performed according to blinding method. Meta-regression and inverted funnel plots were also conducted.A total of 13 studies containing 1604 RH patients were included. Compared with control, the meta-analysis showed that RD significantly reduced office-based BP and ambulatory BP in 6 months in the unblinded studies, while no significant difference was found in the blinded studies. Meta-regression demonstrated the significant influence of blinding method on BP reduction, and further analysis revealed a significant BP reduction compared with baseline even in the control arm of blinded studies. RD had similar effects compared with adjusted drugs, and combined therapy seemed to further reduce the level of BP.The efficacy of RD was different between blinded and unblinded studies, and our data revealed a significant BP-lowering effect in the control arm of blinded studies, which was helpful to explain this finding. Furthermore, RD seemed to be equivalent to adjusted drugs, and also we suggested a potential advantage of combined therapy of RD and adjusted drugs compared with monotherapy for RH. However, more studies are warranted to better address the issue.

Interventional therapy for hypertension: Back on track again?

Treatment-resistant hypertension, or resistant hypertension, is defined as blood pressure that remains above target despite concurrent use of at least three antihypertensive agents from different classes at optimal doses, one of which should be a diuretic. Important considerations in the diagnosis of treatment-resistant hypertension include the exclusion of pseudoresistance and the evaluation of potential secondary causes of hypertension and of concomitant conditions that maintain high blood pressure. The ability to diagnose true treatment-resistant hypertension is important for selection of patients who may be appropriately treated with an invasive therapy. Currently, there are three interventional approaches to treat resistant hypertension, namely: (1) reduction of the activity of the sympathetic nervous system by renal nerve ablation, (2) stimulation of baroreceptors and (3) creation of a peripheral arterial venous anastomosis. This review focuses on the rationale behind these invasive approaches and the clinical results.

Persistent Increase in Blood Pressure After Renal Nerve Stimulation in Accessory Renal Arteries After Sympathetic Renal Denervation

Blood pressure response to renal denervation is highly variable, and the proportion of responders is disappointing. This may be partly because of accessory renal arteries too small for denervation, causing incomplete ablation. Renal nerve stimulation before and after renal denervation is a promising approach to assess completeness of renal denervation and may predict blood pressure response to renal denervation. The objective of the current study was to assess renal nerve stimulation–induced blood pressure increase before and after renal sympathetic denervation in main and accessory renal arteries of anaesthetized patients with drug-resistant hypertension. The study included 21 patients. Nine patients had at least 1 accessory renal artery in which renal denervation was not feasible. Renal nerve stimulation was performed in the main arteries of all patients and in accessory renal arteries of 6 of 9 patients with accessory arteries, both before and after renal sympathetic denervation. Renal nerve stimulation before renal denervation elicited a substantial increase in systolic blood pressure, both in main (25.6±2.9 mm Hg; P <0.001) and accessory (24.3±7.4 mm Hg; P =0.047) renal arteries. After renal denervation, renal nerve stimulation–induced systolic blood pressure increase was blunted in the main renal arteries (Δ systolic blood pressure, 8.6±3.7 mm Hg; P =0.020), but not in the nondenervated renal accessory renal arteries (Δ systolic blood pressure, 27.1±7.6 mm Hg; P =0.917). This residual source of renal sympathetic tone may result in persistent hypertension after ablation and partly account for the large response variability.

Multimodality Intra-Arterial Imaging Assessment of the Vascular Trauma Induced by Balloon-Based and Nonballoon-Based Renal Denervation Systems

BACKGROUND

Renal denervation is a new treatment considered for several possible indications. As new systems are introduced, the incidence of acute renal artery wall injury with relation to the denervation method is unknown. We investigated the acute repercussion of renal denervation on the renal arteries of patients treated with balloon-based and nonballoon-based denervation systems by quantitative angiography, intravascular ultrasound, and optical coherence tomography (OCT).

METHODS AND RESULTS

Twenty-five patients (50 renal arteries) underwent bilateral renal denervation with 5 different systems, 3 of which balloon-based (Paradise [n=5], Oneshot [n=6], and Vessix V2 [n=5)]) and 2 nonballoon-based (Symplicity [n=6] and EnligHTN [n=3]). Analysis included quantitative angiography and morphometric intravascular ultrasound measurements pre and post procedure and assessment of vascular trauma (dissection, edema, or thrombus) by OCT after denervation. A significant reduction in lumen size by quantitative angiography and intravascular ultrasound was observed in nonballoon denervation but not in balloon denervation. By postdenervation OCT, dissection was seen in 14 arteries (32.6%). The percentage of frames with dissection was higher in balloon-based denervation catheters. Thrombus and edema were detected in 35 (81.4%) and 32 (74.4%) arteries, respectively. In arteries treated with balloon-based denervation that had dissection by OCT, the balloon/artery ratio was higher (1.24 [1.17-1.32] versus 1.10 [1.04-1.18]; P<0.01).

CONCLUSIONS

A varying extent of vascular injury was observed after renal denervation in all systems; however, different patterns were identified in balloon-based and in nonballoon-based denervation systems. In balloon denervation, the presence of dissections by OCT was associated with a higher balloon/artery ratio.

The effect of renal denervation on resistant hypertension: Meta-analysis of randomized controlled clinical trials

BACKGROUND

This meta-analysis was conducted to evaluate the efficiency of renal denervation (RDN) on resistant hypertension.

METHODS

PubMed, EMBASE, and the Cochrane Central database were searched for eligible randomized controlled clinical trials (RCTs). Changes from the baseline of the office blood pressure and the 24-h ambulatory blood pressure were extracted.

RESULTS

Nine RCTs were included. RDN reduced the mean systolic blood pressure (SBP) and diastolic blood pressure (DBP) by -8.23 mm Hg (95%CI: -16.86, 0.39) and -3.77 mm Hg (95%CI: -7.21, -0.32), respectively, compared with the control. In the population with a baseline SBP more than 170 mm Hg, the RDN reduced SBP by -17.77 mm Hg (95%CI: -33.73, -1.82) and DBP by -7.51 mm Hg (95%CI: -12.58, -2.44). In the subgroup with no medication adjustment, the RDN reduced SBP by -15.56 mm Hg (95%CI: -26.33, -4.80) and DBP by -6.89 mm Hg (95%CI: -9.99, -3.79). The proportion of patients with SBP decrease of 10 mm Hg or more and the controlled office BP were not different between two groups. RDN reduced 24-h mean SBP and DBP by -3.34 mm Hg (95%CI: -5.30, -1.38) and -1.56 mm Hg (95%CI: -2.71, -0.41), respectively. The SBPs in the subgroups with higher baseline SBP and with no medication adjustment were significantly decreased after the HTN-3 was omitted.

CONCLUSION

Radiofrequency RDN in a randomized manner did not have superiority compared with medical treatment at 6-month follow-up in general population. Current evidence provides insufficient evidence to support the use of such RDN strategy in the treatment of resistant hypertension. The result could not be used to extrapolate other strategies' effect.

Renal denervation with a percutaneous bipolar radiofrequency balloon catheter in patients with resistant hypertension: 6-month results from the REDUCE-HTN clinical study

AIMS

To evaluate the safety and efficacy of the balloon-based bipolar Vessix Renal Denervation System in treating patients with resistant hypertension.

METHODS AND RESULTS

In this prospective, multicentre, single-arm study, 146 patients (age 58.6±10.5 years; 61% men) with office systolic blood pressure (BP) ≥160 mmHg despite ≥3 antihypertensive medications at maximally tolerated doses were treated with the Vessix System. Efficacy endpoints were reductions in office and 24-hour ambulatory systolic and diastolic BPs at six months. Acute and long-term safety, with a focus on the renal artery and estimated glomerular filtration rate (eGFR), were assessed. Baseline office and ambulatory BPs were 182.4±18.4/100.2±14.0 mmHg and 153.0±15.1/87.5±13.2 mmHg, respectively. No acute renal artery injury requiring intervention or serious periprocedural cardiovascular events occurred. At six months, office BP was reduced by 24.7±22.1/10.3±12.7 mmHg (p<0.0001) and ambulatory BP was reduced by 8.4±14.4/5.9±9.1 mmHg (N=69; p<0.0001). Twenty-six patients (18%) achieved an office systolic BP <140 mmHg. One patient had renal artery stenosis which required stenting. Mean eGFR remained stable.

CONCLUSIONS

Renal artery denervation with the Vessix System reduced both office and ambulatory BP at six months in patients with resistant hypertension. Renal artery safety and renal function results are favourable.

Differential role of afferent and efferent renal nerves in the maintenance of early- and late-phase Dahl S hypertension

Clinical data suggest that renal denervation (RDNX) may be an effective treatment for human hypertension; however, it is unclear whether this therapeutic effect is due to ablation of afferent or efferent renal nerves. We have previously shown that RDNX lowers arterial pressure in hypertensive Dahl salt-sensitive (S) rats to a similar degree observed in clinical trials. In addition, we have recently developed a method for selective ablation of afferent renal nerves (renal-CAP). In the present study, we tested the hypothesis that the antihypertensive effect of RDNX in the Dahl S rat is due to ablation of afferent renal nerves by comparing the effect of complete RDNX to renal-CAP during two phases of hypertension in the Dahl S rat. In the early phase, rats underwent treatment after 3 wk of high-NaCl feeding when mean arterial pressure (MAP) was ∼ 140 mmHg. In the late phase, rats underwent treatment after 9 wk of high NaCl feeding, when MAP was ∼ 170 mmHg. RDNX reduced MAP ∼ 10 mmHg compared with sham surgery in both the early and late phase, whereas renal-CAP had no antihypertensive effect. These results suggest that, in the Dahl S rat, the antihypertensive effect of RDNX is not dependent on pretreatment arterial pressure, nor is it due to ablation of afferent renal nerves.

Comparison of Saline-Irrigated Catheter vs. Temperature-Controlled Catheter for Renal Denervation in a Canine Model

BACKGROUND

The effectiveness of catheter-based renal denervation (RDN) remains controversial. Although the reasons for this have not yet been elucidated, ineffective denervation appears to be an important factor. The present study aimed to investigate the difference in RDN between a saline-irrigated catheter (SIC) and a temperature-controlled catheter (TCC).

METHODS

Dogs (n = 6) from the Kunming province in Chinese were ablated; the SIC was introduced into the right renal artery, while the TCC was introduced into the left renal artery. After 6 months, histopathology and renal angiography were performed, and the change in neural density was evaluated using morphometric software. The average values of heart rate (HR), blood pressure (BP), and catecholamine metabolites were assessed at baseline and follow-up.

RESULTS

Histopathology showed nerve demyelination and denaturation, as well as interstitial hyperplasia, although these changes were more pronounced when the SIC was used. The change in neural density was greater and ablation was deeper when the SIC was used. Intimal hyperplasia was greater when the TCC was used, whereas medial hyperplasia was greater when the SIC was used. A trend toward a decrease in HR, BP, metanephrine, and normetanephrine between baseline and follow-up was observed.

CONCLUSIONS

Our findings suggest that SIC ablation results in more extensive neural degeneration, deeper penetration, and less extensive intimal hyperplasia than TCC ablation for RDN.