Catheter-based renal denervation is no simple matter: lessons to be learned from our anatomy?

Renal denervation for hypertension

Innovative therapies for hypertension are desperately needed given the rising prevalence and falling rates of control of hypertension despite an abundance of available medical therapies. Procedural interventions lower blood pressure without depending on adherence to medications, and endovascular renal denervation (RDN) is the interventional procedure with the best evidence base for the treatment of hypertension. After nearly two decades of study, with major refinements to devices, technique and trial design, two different systems for RDN received approval from the FDA in late 2023 for the treatment of hypertension. These decisions were based on a portfolio of sham-controlled clinical trials demonstrating efficacy and safety of both radiofrequency and ultrasound RDN in treating patients across the spectrum of hypertension, including patients with mild disease taking no or one medication as well as those with moderate and truly resistant hypertension. In this Review, we begin by summarizing the background and scope of the global problem of hypertension control and explore the evolution and mechanism of RDN. We then detail early studies and randomized clinical trials demonstrating the efficacy and safety of RDN procedures, review international statements, and provide practical guidance on patient selection and implementation of RDN, including the crucial aspects of building a hypertension team and of involving patients in shared decision-making.

Controversies in Hypertension IV: Renal Denervation

Renal denervation is not a cure for hypertension. Although more recent sham-controlled trials were positive, a significant minority of patients in each trial were unresponsive. The optimal patient or patients need to be defined. Combined systolic/diastolic hypertension appears more responsive than isolated systolic hypertension. It remains uncertain whether patients with comorbidities associated with higher adrenergic tone should be targeted, including obesity, diabetes, sleep apnea, and chronic kidney disease. No biomarker can adequately predict response. A key to a successful response is the adequacy of denervation, which currently cannot be assessed in real time. It is uncertain what is the optimal denervation methodology: radiofrequency, ultrasound, or ethanol injection. Radiofrequency requires targeting the distal main renal artery plus major branches and accessory arteries. Although denervation appears to be safe, conclusive data on quality of life, improved target organ damage, and reduced cardiovascular events/mortality are required before denervation can be generally recommended.

Patient-Level Pooled Analysis of Ultrasound Renal Denervation in the Sham-Controlled RADIANCE II, RADIANCE-HTN SOLO, and RADIANCE-HTN TRIO Trials

Importance

Ultrasound renal denervation (uRDN) was shown to lower blood pressure (BP) in patients with uncontrolled hypertension (HTN). Establishing the magnitude and consistency of the uRDN effect across the HTN spectrum is clinically important.

Objective

To characterize the effectiveness and safety of uRDN vs a sham procedure from individual patient-level pooled data across uRDN trials including either patients with mild to moderate HTN on a background of no medications or with HTN resistant to standardized triple-combination therapy.

Data Sources

A Study of the ReCor Medical Paradise System in Clinical Hypertension (RADIANCE-HTN SOLO and TRIO) and A Study of the ReCor Medical Paradise System in Stage II Hypertension (RADIANCE II) trials.

Study Selection

Trials with similar designs, standardized operational implementation (medication standardization and blinding of both patients and physicians to treatment assignment), and follow-up.

Data Extraction and Synthesis

Pooled analysis using individual patient-level data using linear regression models to compare uRDN with sham across the trials.

Main Outcomes and Measures

The primary outcome was baseline-adjusted change in 2-month daytime ambulatory systolic BP (dASBP) between groups.

Results

A total of 506 patients were randomized in the 3 studies (uRDN, 293; sham, 213; mean [SD] age, 54.1 [9.3]; 354 male [70.0%]). After a 1-month medication stabilization period, dASBP was similar between the groups (mean [SD], uRDN, 150.3 [9.2] mm Hg; sham, 150.8 [10.5] mm Hg). At 2 months, dASBP decreased by 8.5 mm Hg to mean (SD) 141.8 (13.8) mm Hg among patients treated with uRDN and by 2.9 mm Hg to 147.9 (14.6) mm Hg among patients treated with a sham procedure (mean difference, -5.9; 95% CI, -8.1 to -3.8 mm Hg; P < .001 in favor of uRDN). BP decreases from baseline with uRDN vs sham were consistent across trials and across BP parameters (office SBP: -10.4 mm Hg vs -3.4 mm Hg; mean difference, -6.4 mm Hg; 95% CI, -9.1 to -3.6 mm Hg; home SBP: -8.4 mm Hg vs -1.4 mm Hg; mean difference, -6.8 mm Hg; 95% CI, -8.7 to -4.9 mm Hg, respectively). The BP reductions with uRDN vs sham were consistent across prespecified subgroups. Independent predictors of a larger BP response to uRDN were higher baseline BP and heart rate and the presence of orthostatic hypertension. No differences in early safety end points were observed between groups.

Conclusions and Relevance

Results of this patient-level pooled analysis suggest that BP reductions with uRDN were consistent across HTN severity in sham-controlled trials designed with a 2-month primary end point to standardize medications across randomized groups.

Trial Registration

ClinicalTrials.gov Identifier: NCT02649426 and NCT03614260.

Morphometric analysis of the human common hepatic artery reveals a rich and accessible target for sympathetic liver denervation

This study quantified the distribution of nerves and adjacent anatomies surrounding human common hepatic artery (CHA) as guidance for catheter based denervation. CHA collected from cadaveric human donors (n = 20) were histologically evaluated and periarterial dimensions and distributions of nerves, lymph nodes, pancreas and blood vessels quantified by digital morphometry. Nerve abundance decreased significantly with distance from the aortic ostium (P < 0.0001) and was higher in the Superior/Inferior compared to the Anterior/Posterior quadrants (P = 0.014). In each locational group, nerves were absent from the artery wall, and starting 0.5–1.0 mm from the lumen exhibited a first order dependence on radial distance, fully defined by the median distance. Median subject-averaged nerve distance to the lumen was 2.75 mm, ranging from 2.1–3.1 mm in different arterial segments and quadrants and 2.0–3.5 mm in individuals. Inter-individual variance was high, with certain individuals exhibiting 50th and 75th nerve distances of, respectively, 3.5 and 6.5 mm The pancreas rarely approached within 4 mm of the lumen proximally and 2.5 mm more distally. The data indicate that the CHA is a rich and accessible target for sympathetic denervation regardless of sex and diabetes, with efficacy and safety most optimally balanced proximally.

Correlation between Renal Artery Anatomy and Hypertension: A Retrospective Analysis of 3000 Patients

Objective

To assess the correlation between renal artery anatomy and blood pressure in Undiagnosed Hypertension and Diagnosed Hypertension.

Methods

The renal artery CT scanning imaging data and laboratory data of 3000 inpatients and outpatients were collected retrospectively in 4 centers of China. Morphometric parameters were assessed using the quantitative vascular analysis (unit: mM).

Results

687 cases (23.2%) had accessory renal arteries unilaterally, and 216 cases (7.3%) had bilateral accessory renal arteries, including left kidney 825 (27.9%) and right kidney 798 (27.0%). The presence of accessory renal arteries and renal artery branches was higher in the diagnosed hypertension group as compared with the undiagnosed hypertension group (MARB, pp < 0.001; ARA, p < 0.001; others, p < 0.001). Consequently, multivariate regression analysis showed that age (OR = 2.519 (95% CI: 0.990–6.411, p < 0.001)), dyslipidemia (OR = 1.187 (95% CI: 0.960–1.454, p = 0.007)), renal hilum Outside the main renal artery branch (MRAB) (OR = 2.069 (95% CI: 1.614–2.524, p = 0.002)), and accessory renal artery (ARA) (OR = 2.071 (95% CI: 1.614–2.634, p = 0.001)) were risk factors of hypertension. In addition, higher renin activity was associated with ARA patients (2.19 ± 2.91 vs. 1.75 ± 2.85, p < 0.001).

Conclusions

When comparing renal arteries side by side, the anatomical length of the renal arteries is significantly different. In addition, the prevalence of accessory renal arteries and renal artery branches is higher in the hypertension group. The auxiliary renal artery and the main renal artery branch outside the renal portal are independent factors of hypertension. Renal sympathetic nerve activity is affected by renin activity and is related to the accessory renal artery.

Effectiveness of radiofrequency renal denervation in diseases with increased sympathetic nervous system activity

The article discusses the role of sympathetic nervous system hyperactivity in the pathogenesis of various pathologies (hypertension, heart failure, atrial fibrillation, metabolic syndrome, diabetes and systemic inflammatory response syndrome). On the example of large randomized clinical trials using catheter-based radiofrequency ablation, the antihypertensive effect in patients with uncontrolled hypertension has been proven. The first experimental and clinical studies on the effectiveness of renal denervation in reducing the activity of inflammatory markers, the incidence of atrial fibrillation and ventricular arrhythmia episodes, and improving the left ventricular contractility. The first clinical results of the favorable effect of renal denervation on carbohydrate metabolism (insulin resistance and glycemic level) in patients with metabolic syndrome and diabetes have been studied in detail.

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.

Combined renal and common hepatic artery denervation as a novel approach to reduce cardiometabolic risk: technical approach, feasibility and safety in a pre-clinical model

Background

Cardiovascular and metabolic regulation is governed by neurohumoral signalling in relevant organs such as kidney, liver, pancreas, duodenum, adipose tissue, and skeletal muscle. Combined targeting of relevant neural outflows may provide a unique therapeutic opportunity for cardiometabolic disease.

Objectives

We aimed to investigate the feasibility, safety, and performance of a novel device-based approach for multi-organ denervation in a swine model over 30 and 90 days of follow-up.

Methods

Five Yorkshire cross pigs underwent combined percutaneous denervation in the renal arteries and the common hepatic artery (CHA) with the iRF Denervation System. Control animals (n = 3) were also studied. Specific energy doses were administered in the renal arteries and CHA. Blood was collected at 30 and 90 days. All animals had a pre-terminal procedure angiography. Tissue samples were collected for norepinephrine (NEPI) bioanalysis. Histopathological evaluation of collateral structures and tissues near the treatment sites was performed to assess treatment safety.

Results

All animals entered and exited the study in good health. No stenosis or vessel abnormalities were present. No significant changes in serum chemistry occurred. NEPI concentrations were significantly reduced in the liver (− 88%, p = 0.005), kidneys (− 78%, p < 0.001), pancreas (− 78%, p = 0.018) and duodenum (− 95%, p = 0.028) following multi-organ denervation treatment compared to control animals. Histologic findings were consistent with favourable tissue responses at 90 days follow-up.

Conclusions

Significant and sustained denervation of the treated organs was achieved at 90 days without major safety events. Our findings demonstrate the feasibility of multi-organ denervation using a novel iRF Denervation System in a single procedure.

Interventional Approaches for Loin Pain Hematuria Syndrome and Kidney-Related Pain Syndromes

PURPOSE OF REVIEW

Loin pain hematuria syndrome (LPHS) frequently presents with severe chronic pain that poses a clinical challenge. Current treatment approaches are mostly empirical and include a wide range of therapeutic strategies such as physical therapy, local and systemic analgesia, interventional and surgical approaches usually flanked by psycho-behavioral therapy, and other strategies. LPHS often impacts negatively on quality of life particularly in patients who are refractory to treatment.

RECENT FINDINGS

With recent advances in catheter-based treatment approaches and better understanding of the pathophysiology of LPHS, intraluminal renal denervation (RDN) has been proposed as a valuable treatment option for kidney-related pain syndromes. The present review provides a brief overview of the clinical challenges associated with LPHS, highlights recent insights into its underlying mechanisms, and summarizes currently available data on the use of RDN in the context of LPHS and kidney-related pain syndromes. Renal denervation via various approaches including surgical and catheter-based techniques has shown promise in alleviating kidney-related pain syndromes. Randomized controlled trials are now required to better define its role in the management of these conditions.

Efficacy and safety of renal denervation for the management of arterial hypertension: A systematic review and meta-analysis of randomized, sham-controlled, catheter-based trials

Despite the availability of a numerous antihypertensive agents, hypertension treatment and control rates remain low in many countries. The role of the sympathetic nervous system has long been recognized, but recent sham control renal denervation studies demonstrated conflicting results. In this reviewe paper, the authors performed a systematic review and meta-analysis to examine outcomes of sham-controlled studies utilizing new technologies and procedures. Six published randomized, sham-controlled studies were included in this meta-analysis. Of those, three trials used the first-generation radiofrequency renal denervation device and technique and the other three used second-generation devices and techniques. In total, 981 patients with hypertension were randomized in all 6 trials to undergo renal denervation (n = 585) or sham procedure (n = 396). Overall, renal denervation resulted in a decrease of 24-hours systolic ambulatory blood pressure (ABP) by 3.62 mm Hg (95% CI: -5.28--1.96; I2  = 0%), compared to sham procedure (GRADE: low). Renal denervation also reduced daytime systolic ABP by 5.51 mm Hg (95% CI: -7.79--3.23; I2  = 0%), compared to sham procedure but not nighttime systolic ABP. Office systolic blood pressure was reduced by 5.47 mm Hg (95% CI -8.10--2.84; I2  = 0%), compared to sham control. Further analysis demonstrated that second-generation devices were effective in reducing blood pressure, whereas the first-generation devices were not. These results indicate that effective renal denervation can result in significant and clinically meaningful blood pressure reduction. The second-generation devices provide better renal nerve ablation.

New data, new studies, new hopes for renal denervation in patients with uncontrolled hypertension

Background

following the publication of SYMPLICITY HTN-3 the field of renal of denervation was put on hold. Although SYMPLICITY HTN-3 was well-designed and sham-controlled trial it failed to show any meaningful reduction in office or 24 h ambulatory blood pressure. The procedure was however safe and allowed research to continue. Although several pitfalls of the study have been pointed out, incomplete renal denervation was also implicated. Since then, a great deal of basic and clinical research took place and will be briefly commented on in this article.

Methods and results

Before and after SYMPLICITY-HTN-3, numerous uncontrolled, single or unblinded studies have shown substantial office BP reduction ranging from -7.7 to -32 mmHg and ambulatory BP ranging from -2.2 to 10.2 mmHg. Average weighted office systolic BP reduction was -20.8 mmHg and weighted average 24 h ambulatory BPM reduction was -7.8 mmHg. National and international registries have shown similar BP reductions, but results remained unconvincing due to lack of reliable sham controls. In recent years, 5 well-designed sham - controlled studies (beyond, SYMPLICITY-HTN-3) have been published. Of those studies two were single center and three were multicenter international studies. Four studies used single tip or multi-electrode, radiofrequency catheters and one used focused ultrasound. The three multicenter studies reported positive-placebo subtracted results and established BP reductions measured both in the office and by ambulatory monitoring. No serious adverse events were reported.

Conclusions

It can therefore be concluded that the latest sham controlled studies established efficacy and safety of renal denervation.

Procedural and anatomical predictors of renal denervation efficacy using two radiofrequency renal denervation catheters in a porcine model

Introduction:

Several renal denervation (RDN) systems are currently under investigation for treatment of hypertension by ablation of renal sympathetic nerves. The procedural efficacy of devices, however, is variable and incompletely understood. This study aimed at investigating procedural and anatomical predictors of RDN efficacy by comparing two radiofrequency catheter systems in a porcine model.

Methods:

Domestic swine were assigned into two treatment groups (n = 10) and one sham group (n = 3). Bilateral RDN in main and in branch segments of renal arteries was performed using two different multielectrode catheter systems [Symplicity Spyral (SPY) and IberisBloom (IBB)]. After 7 days, measurement of norepinephrine (NEPI) tissue concentrations and histological analyses have been performed.

Results:

Renal NEPI tissue concentration following RDN was significantly reduced when compared with Sham (SPY: −95 ± 3% vs. Sham, P < 0.001; IBB: −88 ± 11% vs. Sham, P < 0.001). Histological evaluation showed comparable lesion depth and lesion area (lesion depth: SPY-main 6.26 ± 1.62 mm vs. SPY-branch 3.49 ± 1.11 mm; IBB-main 5.93 ± 1.88 mm vs. IBB-branch: 3.26 ± 1.26 mm, P < 0.001; lesion area: SPY-main 43.5 ± 29.5 mm² vs. SYP-branch 45.0 ± 38.0 mm²; IBB-main 52.3 ± 34.8 mm² vs. IBB-branch 44.0 ± 42.6 mm², P = 0.77; intergroup SPY vs. IBB, P = 0.73). Histological investigations documented a significant correlation between number of ablations per millimeter length of renal artery and reduction in NEPI tissue concentration.

Conclusion:

The two devices under investigation demonstrated similar histopathological lesion characteristics and similar reduction of renal NEPI levels. An increase in number of ablations per millmeter length of renal artery resulted in improved efficacy and reduced variability in treatment effects.

Renal artery anatomy assessed by quantitative analysis of selective renal angiography in 1,000 patients with hypertension

AIMS

With increasing attention to renovascular causes and targets for hypertension there arises a critical need for more detailed knowledge of renal arterial anatomy. However, a standardised nomenclature is lacking. The present study sought to develop a standardised nomenclature for renal anatomy considering the complexity and variation of the renal arterial tree and to assess the applicability of the nomenclature.

METHODS AND RESULTS

One thousand hypertensive patients underwent invasive selective renal artery angiography in nine centres. Further, renovasography was performed in 249 healthy swine as a surrogate for normotensive anatomy. Anatomical parameters were assessed by quantitative vascular analysis. Patients' mean blood pressure was 168/90±26/17 mmHg. The right main renal artery was longer than the left (41±15 mm vs. 35±13 mm, p<0.001), but the left had a greater diameter (5.4±1.2 vs. 5.2±1.2 mm, p<0.001). Accessory renal arteries and renal artery disease were documented in 22% and 9% of the patients, respectively. Other than exhibiting a longer left main renal artery in uncontrolled hypertensives (+2.7 mm, p=0.034) there was no anatomical difference between patients with controlled and uncontrolled hypertension. Main renal artery mean diameter was smaller in patients with impaired kidney function (GFR <90 ml/min, left -0.5 mm, right -0.4 mm, both p<0.001).

CONCLUSIONS

Renal arterial anatomy differs between sides but shows no difference between patients with and without blood pressure control. Impaired GFR was associated with small main renal artery diameter.

Procedural and Anatomical Determinants of Multielectrode Renal Denervation Efficacy

Radiofrequency renal denervation is under investigation for treatment of hypertension with variable success. We developed preclinical models to examine the dependence of ablation biomarkers on renal denervation treatment parameters and anatomic variables. One hundred twenty-nine porcine renal arteries were denervated with an irrigated radiofrequency catheter with multiple helically arrayed electrodes. Nerve effects and ablation geometries at 7 days were characterized histomorphometrically and correlated with associated renal norepinephrine levels. Norepinephrine exhibited a threshold dependence on the percentage of affected nerves across the range of treatment durations (30-60 s) and power set points (6-20 W). For 15 W/30 s treatments, norepinephrine reduction and percentage of affected nerves tracked with number of electrode treatments, confirming additive effects of helically staggered ablations. Threshold effects were only attained when ≥4 electrodes were powered. Histomorphometry and computational modeling both illustrated that radiofrequency treatments directed at large neighboring veins resulted in subaverage ablation areas and, therefore, contributed suboptimally to efficacy. Account for measured nerve distribution patterns and the annular geometry of the artery revealed that, regardless of treatment variables, total ablation area and circumferential coverage were the prime determinants of renal denervation efficacy, with increased efficacy at smaller diameters.

Renal Denervation: Is It Ready for Prime Time?

PURPOSE OF REVIEW

Interventional cardiology and in particular the field of renal denervation is subject to constant change. This review provides an up to date overview of renal denervation trials and an outlook on what to expect in the future.

RECENT FINDINGS

After the sham-controlled SYMPLICITY HTN-3 trial dampened the euphoria following early renal denervation trials, the recently published results of the sham-controlled SPYRAL HTN and RADIANCE HTN trials provided proof-of-principle for the blood pressure-lowering efficacy of renal denervation. However, these studies underline the major issue of patients' non-adherence to antihypertensive medication as well as the need for reliable patient- and procedure-related predictors of response. The second generation of sham-controlled renal denervation trials provided proof of principle for the blood pressure-lowering efficacy of RDN. However, larger trials have to assess long-term safety and efficacy.

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.

Safety and performance of diagnostic electrical mapping of renal nerves in hypertensive patients

AIMS

The aim of this study was to evaluate the safety and performance of renal nerve stimulation (RNS) for diagnostic mapping of the renal nerves.

METHODS AND RESULTS

In this first-in-man study, twenty hypertensive patients underwent RNS using the ConfidenHT system. Bilateral stimulations were performed at three to four sites per artery at 2 and 4 mA. The primary endpoint was change in systolic blood pressure (SBP). Mean office blood pressure was 156/89 mmHg. No periprocedural adverse events occurred. Stimulation with 2 mA resulted in a maximum change of 8.3±6.3 mmHg in SBP (based on 119 stimulations; p<0.001), while stimulating with 4 mA resulted in a maximum change of 10.1±7.8 mmHg (based on 61 stimulations; p<0.001). The mean change in SBP did not vary between mid, distal or branch sites when stimulating at 2 mA but was significantly higher at ostial (23±14 mmHg) than at non-ostial locations (9±7 mmHg) when stimulating at 4 mA (p=0.003).

CONCLUSIONS

RNS can be performed safely and effectively along the renal artery and results in a large variation in temporary BP changes per patient and per anatomic location. RNS might help in optimising treatment effect and selecting potential responders to renal sympathetic denervation.

Safety of catheter-based radiofrequency renal denervation on branch renal arteries in a porcine model

OBJECTIVES

We aimed to investigate the safety of radiofrequency (RF)-renal denervation (RDN) on branch renal arteries (RAs) in a porcine model.

BACKGROUND

The efficacy of RF-RDN was enhanced by treatment of the branch RA, in addition to the main RA. However, there are concerns regarding the safety of RF-RDN on branch RA because of their smaller diameter and proximity to the kidney.

METHODS

RF was delivered to 24 RA from 12 swine. A total of 8 RA from 4 swine were untreated. Treated RA were examined by angiography and histopathology at 7, 30, and 90 days. Serum creatinine concentration, biophysical parameters during RF delivery, and renal norepinephrine concentration were also assessed.

RESULTS

Angiography revealed minimal late lumen loss and diameter stenosis in the main and branch RA at any time point. There was no change in serum creatinine after RF-RDN. Histopathologically, no augmentation of medial damage or neointimal formation was found in branch RA compared with main RA. No or minimal damage to surrounding tissues including the kidneys, ureters, lymph nodes, and muscles was observed at any time point in both the main and branch RA. Equivalent electrode temperature in the main and branch RA was achieved by automatic adjustment of output power by the generator. The renal norepinephrine concentration was significantly lower in the treated group compared with the untreated group.

CONCLUSIONS

RF-RDN on branch RA was safe in a porcine model, with stenosis-free healing of treated arteries and negligible kidney damage at 7, 30, and 90 days.

Modulation of Sympathetic Overactivity to Treat Resistant Hypertension

PURPOSE OF REVIEW

To review the role and evidence for sympathetic overactivity in resistant hypertension and review the therapies that have been studied to modulate the sympathetic nervous system to treat resistant hypertension, with a focus on non-pharmacologic therapies such as renal denervation, baroreflex activation therapy, and carotid body ablation.

RECENT FINDINGS

Based on the two best current techniques available for assessing sympathetic nerve activity, resistant hypertension is characterized by increased sympathetic nerve activity. Several device therapies, including renal denervation baroreflex activation therapy and carotid body ablation, have been developed as non-pharmacologic means of reducing blood pressure in resistant hypertension. With respect to renal denervation, the technologies for renal denervation have evolved since the unfavorable results from the HTN-3 study, and the revised technologies are being actively studied. Data from the first phase of the SPYRAL HTN Clinical Trial Program have been published. Results from the SPYRAL HTN-OFF MED trial suggest that ablating renal nerves can reduce blood pressure in patients with untreated mild-to-moderate hypertension. The SPYRAL HTN-ON MED trial demonstrated the safety and efficacy of catheter-based renal denervation in patients with uncontrolled hypertension on antihypertensive treatment. Interestingly, there was a high rate of medication non-adherence among patients with hypertension in this study. One attractive alternative to radiofrequency ablation is the use of ultrasound for renal denervation. Proof of concept data for the Paradise endovascular ultrasound renal denervation system was recently published in the RADIANCE-HTN SOLO trial. The results of this trial indicate that, among patients with mild to moderate hypertension on no medications, renal denervation with the Paradise system results in a greater reduction in both SBP and DBP at 2months compared with a sham procedure. Overall reductions were similar in magnitude to those noted in the SPYRAL HTN-OFF MED study. With respect to carotid body ablation, there is an ongoing proof of concept study that is investigating the safety and feasibility of ultrasound-based endovascular carotid body ablation in 30 subjects with treatment-resistant hypertension outside of the USA. The sympathetic nervous system is an important contributor to resistant hypertension. Modulation of sympathetic overactivity should be an important goal of treatment. Innovative therapies using non-pharmacologic means to suppress the sympathetic nervous system are actively being studied to treat resistant hypertension.

Renal Sympathetic Denervation in Patients with Resistant Hypertension: A Feasibility Study

Background/Aims

We assessed the feasibility of renal sympathetic denervation (RDN) treatment in patients with resistant hypertension using the Iberis® RDN system. This study was a prospective, multicenter, single-arm feasibility registry.

Methods

We collected data from patients who underwent RDN treatment using the Iberis system. From November 2014 to February 2016, 16 patients from 6 centers in Europe were enrolled in this registry.

Results

Consistent reductions in the 24-h systolic blood pressure (SBP) and diastolic blood pressure were obtained. At any follow-up point, more than 70% of the patients were responders. The change in the 24-h SBP at 1 month was strongly correlated with that at 12 months.

Conclusion

The Iberis system is safe and effective in patients for the treatment of resistant hypertension. Furthermore, our results suggest that we can estimate the effect of RDN in the long term at the 1-month follow-up point using the 24-h SBP.

Electrical stimulation of renal nerves for modulating urine glucose excretion in rats

BACKGROUND

The role of the kidney in glucose homeostasis has gained global interest. Kidneys are innervated by renal nerves, and renal denervation animal models have shown improved glucose regulation. We hypothesized that stimulation of renal nerves at kilohertz frequencies, which can block propagation of action potentials, would increase urine glucose excretion. Conversely, we hypothesized that low frequency stimulation, which has been shown to increase renal nerve activity, would decrease urine glucose excretion.

METHODS

We performed non-survival experiments on male rats under thiobutabarbital anesthesia. A cuff electrode was placed around the left renal artery, encircling the renal nerves. Ureters were cannulated bilaterally to obtain urine samples from each kidney independently for comparison. Renal nerves were stimulated at kilohertz frequencies (1-50 kHz) or low frequencies (2-5 Hz), with intravenous administration of a glucose bolus shortly into the 25-40-min stimulation period. Urine samples were collected at 5-10-min intervals, and colorimetric assays were used to quantify glucose excretion and concentration between stimulated and non-stimulated kidneys. A Kruskal-Wallis test was performed across all stimulation frequencies (α = 0.05), followed by a post-hoc Wilcoxon rank sum test with Bonferroni correction (α = 0.005).

RESULTS

For kilohertz frequency trials, the stimulated kidney yielded a higher average total urine glucose excretion at 33 kHz (+ 24.5%; n = 9) than 1 kHz (- 5.9%; n = 6) and 50 kHz (+ 2.3%; n = 14). In low frequency stimulation trials, 5 Hz stimulation led to a lower average total urine glucose excretion (- 40.4%; n = 6) than 2 Hz (- 27.2%; n = 5). The average total urine glucose excretion between 33 kHz and 5 Hz was statistically significant (p < 0.005). Similar outcomes were observed for urine flow rate, which may suggest an associated response. No trends or statistical significance were observed for urine glucose concentrations.

CONCLUSION

To our knowledge, this is the first study to investigate electrical stimulation of renal nerves to modulate urine glucose excretion. Our experimental results show that stimulation of renal nerves may modulate urine glucose excretion, however, this response may be associated with urine flow rate. Future work is needed to examine the underlying mechanisms and identify approaches for enhancing regulation of glucose excretion.

Anatomical and procedural determinants of ambulatory blood pressure lowering following catheter-based renal denervation using radiofrequency

BACKGROUND/PURPOSE

Catheter-based renal sympathetic denervation (RDN) has been introduced to lower blood pressure (BP) and sympathetic activity in patients with uncontrolled hypertension with at best equivocal results. It has been postulated that anatomic and procedural elements introduce unaccounted variability and yet little is known of the impact of renal anatomy and procedural parameters on BP response to RDN.

METHODS/MATERIALS

Anatomical parameters such as length and diameter were analyzed by quantitative vascular analysis and the prevalence of accessory renal arteries and renal artery disease were documented in 150 patients with resistant hypertension undergoing bilateral RDN using a mono-electrode radiofrequency catheter (Symplicity Flex, Medtronic).

RESULTS

Accessory renal arteries and renal artery disease were present in 56 (37%) and 14 patients (9%), respectively. At 6-months, 24 h-ambulatory BP was reduced by 11/6 mm Hg (p < 0.001 for both). Change of systolic blood pressure (SBP) was not related to the presence of accessory renal arteries (p = 0.543) or renal artery disease (p = 0.598). Patients with at least one main renal artery diameter ≤ 4 mm had a more pronounced reduction of 24 h-ambulatory SBP compared to patients where both arteries were >4 mm (-19 vs. -10 mmHg; p = 0.038). Neither the length of the renal artery nor the number of RF ablations influenced 24 h-ambulatory BP reduction at 6 months.

CONCLUSIONS

24 h-ambulatory BP lowering was most pronounced in patients with smaller renal artery diameter but not related to renal artery length, accessory arteries or renal artery disease. Further, there was no dose-response relationship observed with increasing number of ablations.

CONDENSED ABSTRACT

Because little is known of the impact of renal anatomy and procedural parameters on blood pressure (BP) response to renal denervation (RDN), anatomical and procedural data were analyzed in 150 patients undergoing bilateral RDN. BP lowering was most pronounced in patients with smaller renal artery diameter but not related to renal artery length, the presence of renal artery disease or accessory renal arteries. Further, there was no dose-response relationship observed with increasing number of ablations.

Successful Use of Renal Denervation in Patients With Loin Pain Hematuria Syndrome-The Regina Loin Pain Hematuria Syndrome Study

Introduction

Loin pain hematuria syndrome (LPHS) is characterized by severe unilateral or bilateral loin pain that suggests a renal origin but occurs in the absence of identifiable or relevant urinary tract disease. Hematuria can either be microscopic or macroscopic, but the renal abnormalities responsible for the hematuria are unexplained. Debilitating pain refractory to conventional pain medications is the main cause of morbidity.

Methods

We conducted a single-arm, single-center study. Twelve patients between the ages of 21 and 62 years (11 female, 1 male) with LPHS underwent endovascular ablation of the renal nerves between July 2015 and November 2016, using the Vessix renal denervation system. The primary objective was to achieve 30% reduction in self-reported pain with the McGill Pain Questionnaire (MPQ) at 6 months. The secondary objectives were to measure changes in disability (Oswestry Disability Index [ODI]), mood (Geriatric Depression Scale [GDS]), and quality of life (EuroQol-5D [EQ-5D] and the MOS 36-Item Short Form Survey [SF-36]) scores from baseline to 6 months postprocedure.

Results

Ten of 12 patients at 3 months and 11 of 12 patients at 6 months reported a >30% reduction in pain based on the MPQ at 3 and 6 months. We found consistent improvements in MPQ, ODI, GDS, EQ-5D, and SF-36 scores from baseline to 6 months postprocedure.

Conclusion

We conclude that renal denervation is associated with a considerable improvement in pain, disability, quality of life, and mood. Our results suggest that percutaneous catheter−based delivery of radiofrequency energy is a safe, rapid treatment option that should be considered in all patients with LPHS.

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.

Renal denervation by CT-guided periarterial injection of hyperosmolar saline, vincristine, paclitaxel and guanethidine in a pig model

AIMS

The aim of the study was to evaluate the feasibility, safety and efficacy of renal sympathetic denervation with CT-guided periarterial injection of potentially neurolytic agents in pigs.

METHODS AND RESULTS

Unilateral injection of formulations containing either 5M hyperosmolar saline, vincristine, paclitaxel or guanethidine around the renal artery was performed in 24 normotensive pigs with six animals per group. Needle placement and injections were performed under CT fluoroscopy guidance. Blood pressure measurements and CT scans were performed immediately before and after the intervention and four weeks after treatment. After euthanasia, norepinephrine (NE) concentrations of both kidneys were determined. The renal arteries and surrounding tissue were examined histologically to evaluate nerve fibre degeneration. Procedures were technically successful with good periarterial distribution of the injectant in all but one pig in the guanethidine group. No major adverse events or post-interventional complications occurred. In the vincristine group, NE concentrations of the renal parenchyma were lower on the treated side in all pigs with a mean decrease of 53% (38%-62%, p<0.01) compared to the contralateral control. Correspondingly, histological examination revealed neural degeneration in all animals treated with vincristine. In the other groups, no significant drop of NE values, or histological signs of nerve fibre degeneration were found.

CONCLUSIONS

CT-guided periarterial injection of the different substances was feasible and safe. Renal sympathetic denervation was achieved with vincristine. In contrast, hyperosmolar saline, paclitaxel and guanethidine do not seem to be appropriate for renal denervation in a pig model at the dosage used.

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.

Resistant Hypertension and Renal Nerve Denervation

Patients with resistant hypertension are a subgroup of the hypertensive population that are at even greater risk of cardiovascular outcomes. Therapeutic options for these patients are limited to antihypertensive medications. However, renal denervation (RDN) is a novel nonpharmacologic intervention that involves a catheter-based ablation of the sympathetic nerves within the renal artery wall. The procedure initially showed promise with remarkable blood pressure reductions until the pivotal SYMPLICITY HTN-3 trial failed to demonstrate superiority of RDN over control. This trial was notable for a substantial placebo effect and an attenuated response to RDN. These findings, which contradicted those of prior studies, have raised numerous questions, including whether adequate RDN occurred in those patients. Further research is planned to resolve some of these questions and to clarify the role of RDN in treating patients with resistant hypertension.

Anatomical and procedural determinants of catheter-based renal denervation

BACKGROUND/PURPOSE

Catheter-based renal sympathetic denervation (RDN) can reduce blood pressure (BP) and sympathetic activity in certain patients with uncontrolled hypertension. Less is known about the impact of renal anatomy and procedural parameters on subsequent BP response.

METHODS/MATERIALS

A total of 564 patients with resistant hypertension underwent bilateral RDN in 9 centers in Europe and Australia using a mono-electrode radiofrequency catheter (Symplicity Flex, Medtronic). Anatomical criteria such as prevalence of accessory renal arteries (ARA), presence of renal artery disease (RAD), length, and diameter were analyzed blinded to patient's characteristics.

RESULTS

ARA was present in 171 patients (30%), and RAD was documented in 71 patients (13%). On average 11±2.7 complete 120-s ablations were performed, equally distributed on both sides. After 6months, BP was reduced by 19/8mmHg (p<0.001 for both). Change of systolic blood pressure (SBP) was not related to the presence of ARA (-18 vs. -20mmHg; p=NS) or RAD (-16 vs. -20mmHg; p=NS). Patients with a bilateral diameter≤4mm had a more pronounced reduction of SBP compared to patients with a unilateral diameter≤4mm or a bilateral diameter>4mm (-29 vs. -26 vs. -17mmHg; p<0.001). Neither the length of the renal artery nor the number of RF ablations influenced BP reduction after 6months.

CONCLUSIONS

The diameter of renal arteries correlated with SBP change after RDN at 6-month follow-up. Change of SBP was not related to the lengths of the renal artery, presence of ARA, RAD, or the number of RF ablations delivered by a mono-electrode catheter.

Externally Delivered Focused Ultrasound for Renal Denervation

OBJECTIVES

The aim of this study was to assess clinical safety and efficacy outcomes of renal denervation executed by an externally delivered, completely noninvasive focused therapeutic ultrasound device.

BACKGROUND

Renal denervation has emerged as a potential treatment approach for resistant hypertension.

METHODS

Sixty-nine subjects received renal denervation with externally delivered focused ultrasound via the Kona Medical Surround Sound System. This approach was investigated across 3 consecutive studies to optimize targeting, tracking, and dosing. In the third study, treatments were performed in a completely noninvasive way using duplex ultrasound image guidance to target the therapy. Short- and long-term safety and efficacy were evaluated through use of clinical assessments, magnetic resonance imaging scans prior to and 3 and 24 weeks after renal denervation, and, in cases in which a targeting catheter was used to facilitate targeting, fluoroscopic angiography with contrast.

RESULTS

All patients tolerated renal denervation using externally delivered focused ultrasound. Office blood pressure (BP) decreased by 24.6 ± 27.6/9.0 ± 15.0 mm Hg (from baseline BP of 180.0 ± 18.5/97.7 ± 13.7 mm Hg) in 69 patients after 6 months and 23.8 ± 24.1/10.3 ± 13.1 mm Hg in 64 patients with complete 1-year follow-up. The response rate (BP decrease >10 mm Hg) was 75% after 6 months and 77% after 1 year. The most common adverse event was post-treatment back pain, which was reported in 32 of 69 patients and resolved within 72 h in most cases. No intervention-related adverse events involving motor or sensory deficits were reported. Renal function was not altered, and vascular safety was established by magnetic resonance imaging (all patients), fluoroscopic angiography (n = 48), and optical coherence tomography (n = 5).

CONCLUSIONS

Using externally delivered focused ultrasound and noninvasive duplex ultrasound, image-guided targeting was associated with substantial BP reduction without any major safety signals. Further randomized, sham-controlled trials will be needed to validate this unique approach.

Catheter-based Renal Artery Denervation for Resistant Hypertension: Promise Unfulfilled or Unsettled?

Resistant hypertension affects approximately 10-15 % of the hypertensive population and is associated with an increased occurrence of adverse cardiovascular outcomes. Recently, renal denervation (RDN) has emerged as a novel, non-pharmacologic therapy for resistant hypertension that is designed to ablate the sympathetic nerves distributed around the renal arteries, thus diminishing sympathetic nervous system activity and its influence on hypertension. RDN appeared to have a powerful BP-lowering effect in early clinical trials. However, a pivotal follow-up trial, SYMPLICITY HTN-3, showed no additional benefit of the therapy when compared with a sham procedure. Various aspects of the trial have been examined to explain this inconsistency, including a potent placebo effect and uncertainty about whether RDN actually occurred. Further research is needed to clarify the role of RDN in the management of resistant hypertension.

Controversies Surrounding Renal Denervation: Lessons Learned From Real-World Experience in Two United Kingdom Centers

Renal denervation (RDN) is a therapy that targets treatment-resistant hypertension (TRH). The Renal Denervation in Patients With Uncontrolled Hypertension (Symplicity) HTN-1 and Symplicity HTN-2 trials reported response rates of >80%; however, sham-controlled Symplicity HTN-3 failed to reach its primary blood pressure (BP) outcome. The authors address the current controversies surrounding RDN, illustrated with real-world data from two centers in the United Kingdom. In this cohort, 52% of patients responded to RDN, with a 13±32 mm Hg reduction in office systolic BP (SBP) at 6 months (n=29, P=.03). Baseline office SBP and number of ablations correlated with office SBP reduction (R=-0.47, P=.01; R=-0.56, P=.002). RDN appears to be an effective treatment for some patients with TRH; however, individual responses are highly variable. Selecting patients for RDN is challenging, with only 10% (33 of 321) of the screened patients eligible for the study. Medication alterations and nonadherence confound outcomes. Adequate ablation is critical and should impact future catheter design/training. Markers of procedural success and improved patient selection parameters remain key research aims.

Impact of Lesion Placement on Efficacy and Safety of Catheter-Based Radiofrequency Renal Denervation

BACKGROUND

Insufficient procedural efficacy has been proposed to explain nonresponse to renal denervation (RDN).

OBJECTIVES

The aim of this study was to examine the impact of different patterns of lesion placements on the efficacy and consistency of catheter-based radiofrequency RDN in pigs.

METHODS

The impact of increasing number of lesions versus location of RDN was investigated in a porcine model (Group 1; n = 51). The effect of treating the main artery, the branches, and the 2 combined was compared in Group 2 (n = 48). The durability of response and safety of combined treatment of the main artery plus branches was examined in Group 3 (n = 16). Renal norepinephrine (NE) tissue content and renal cortical axon density were assessed.

RESULTS

Increasing the number of RF lesions (4, 8, and 12) in the main renal artery was not sufficient to yield a clear dose-response relationship on NE content and axon density. In contrast, targeted treatment of the renal artery branches or distal segment of the main renal artery resulted in markedly less variability of response and significantly greater reduction of both NE and axon density than conventional treatment of only the main renal artery. Combination treatment (main artery plus branches) produced the greatest change in renal NE and axon density with the least heterogeneity. The changes were durable through 28 days post-treatment.

CONCLUSIONS

These data provide the rationale for investigation of an optimized approach for RDN in future clinical studies. This may have profound implications for the clinical application of RDN, as this approach may not only achieve greater reductions in sympathetic activity but also reduce treatment effect variability.

Resistant hypertension: what the cardiologist needs to know

Treatment-resistant hypertension (TRH) affects between 3 and 30% of hypertensive patients, and its presence is associated with increased cardiovascular morbidity and mortality. Until recently, the interest on these patients has been limited, because providing care for them is difficult and often frustrating. However, the arrival of new treatment options [i.e. catheter-based renal denervation (RDN) and baroreceptor stimulation] has revitalized the interest in this topic. The very promising results of the initial uncontrolled studies on the blood pressure (BP)-lowering effect of RDN in TRH seemed to suggest that this intervention might represent an easy solution for a complex problem. However, subsequently, data from controlled studies have tempered the enthusiasm of the medical community (and the industry). Conversely, these new studies emphasized some seminal aspects on this topic: (i) the key role of 24 h ambulatory BP and arterial stiffness measurement to identify 'true' resistant patients; (ii) the high prevalence of secondary hypertension among this population; and (iii) the difficulty to identify those patients who may profit from device-based interventions. Accordingly, for those patients with documented TRH, the guidelines suggest to refer them to a hypertension specialist/centre in order to perform adequate work-up and treatment strategies. The aim of this review is to provide guidance for the cardiologist on how to identify patients with TRH and elucidate the prevailing underlying pathophysiological mechanism(s), to define a strategy for the identification of patients with TRH who may benefit from device-based interventions and discuss results and limitations of these interventions, and finally to briefly summarize the different drug-based treatment strategies.

Frequency of renal artery stenosis after renal denervation in patients with resistant arterial hypertension

Catheter-based ablation of nerves in the adventitia of renal arteries (renal artery denervation [RAD]) using radiofrequency energy can reduce blood pressure (BP) in patients with resistant arterial hypertension (RAH). Occurrence of renal artery stenosis after RAD is still an important concern. We systematically investigated the renal artery anatomy using magnetic resonance imaging (MRI) or computed tomography (CT) angiography in a consecutive series of patients 6 months after RAD. Patients with RAH were treated by RAD after exclusion of secondary causes of hypertension. RAH was defined by a mean systolic office BP >160 mm Hg. Renal artery imaging was performed 6 months after RAD by MRI angiography. In case of any contraindication for MRI, a CT angiography was performed. The primary end point was the incidence of significant renal artery stenosis (≥70% lumen diameter reduction). RAD was performed in 76 patients, and evaluation of renal artery anatomy by MRI (n = 66; 87%) or CT angiography (n = 10; 13%) was performed in all patients 6 months after RAD. We found no renal artery stenosis but 2 cases of new nonsignificant stenosis (50% TO 69% lumen diameter reduction). In responders, mean systolic office BP reduction was -30 mm Hg (p <0.001) and mean systolic 24-hour BP reduction was -18 mm Hg (p <0.001). In conclusion, the incidence of significant renal artery stenosis 6 months after RAD seems to be very low. However, late-onset development of nonsignificant renal artery narrowing cannot be excluded in some patients and should be anticipated in the case of RAH relapse or worsening of renal function after successful RAD.