Renal denervation: symply trapped by complexity?

Radio frequency-based renal denervation: a story of simplicity?

Radio frequency-based renal denervation is a safe and effective way of lowering blood pressure, a common condition associated with high cardiovascular risk. Several catheters have been developed to administer energy to the renal arteries and their side branches, thereby modulating sympathetic renal activity. The Symplicity Flex™ and Symplicity Spyral™ are first- and second-generation devices, respectively, for radio frequency-based renal denervation. There is a continuous need to further improve and adjust interventional antihypertensive therapies. Several randomized controlled trials have been conducted to investigate the safety and efficacy of these catheters and most were able to show radio frequency-based renal denervation to be feasible, safe and effective in lowering blood pressure in hypertensive patients with and without concomitant antihypertensive medication. Herein, the authors discuss the pathophysiologic concepts of renal denervation and its procedural approaches, report catheter designs, summarize clinical trials outcomes and, finally, discuss real-world evidence.

Effectiveness of renal denervation in the treatment of hypertension: a literature review

BACKGROUND

Catheter-based renal denervation has been studied as a potential therapeutic option to reduce high blood pressure (BP). Preclinical studies in some experimental models have demonstrated an antihypertensive effect of renal denervation but reports from clinical trials have been mixed METHODS: We performed a literature search using combinations of the key terms 'Cardiovascular diseases, Clinical trial, Pre-clinical trials, Resistant hypertension, Renal denervation, Ablation technique, Radiofrequency ablation, Ultrasound ablation, RADIANCE SOLO, SYMPLICITY HTN, SYPRAL HTN'. The databases searched were PubMed and OVID Medline.

RESULTS

The initial SYMPLICITY HTN-1 AND HTN-2 clinical trials reported significant decreases in office BP but results from the more robustly designed SYMPLICITY HTN-3 trial, which included sham controls and ambulatory BP monitoring, showed no significant antihypertensive effect. Interest in the use of renal denervation in hypertension was once again sparked by favourable results from the SPYRAL HTN-OFF Med trial CONCLUSION: We provide a thorough, critical analysis of key preclinical and clinical studies investigating the efficacy of catheter-based renal denervation as a treatment for hypertension and highlight future areas for research to allow better translation into clinical practice.

Advances in the Treatment Strategies in Hypertension: Present and Future

Hypertension is the most frequent chronic and non-communicable disease all over the world, with about 1.5 billion affected individuals worldwide. Its impact is currently growing, particularly in low-income countries. Even in high-income countries, hypertension remains largely underdiagnosed and undertreated, with consequent low rates of blood pressure (BP) control. Notwithstanding the large number of clinical observational studies and randomized trials over the past four decades, it is sad to note that in the last few years there has been an impressive paucity of innovative studies. Research focused on BP mechanisms and novel antihypertensive drugs is slowing dramatically. The present review discusses some advances in the management of hypertensive patients, and could play a clinical role in the years to come. First, digital/health technology is expected to be increasingly used, although some crucial points remain (development of non-intrusive and clinically validated devices for ambulatory BP measurement, robust storing systems enabling rapid analysis of accrued data, physician-patient interactions, etc.). Second, several areas should be better outlined with regard to BP diagnosis and treatment targets. Third, from a therapeutic standpoint, existing antihypertensive drugs, which are generally effective and well tolerated, should be better used by exploiting available and novel free and fixed combinations. In particular, spironolactone and other mineral-corticoid receptor antagonists should be used more frequently to improve BP control. In particular, some drugs initially developed for conditions different from hypertension including heart failure and diabetes have demonstrated to lower BP significantly and should therefore be considered. Finally, renal artery denervation is another procedure that has proven effective in the management of hypertension.

Successful treatment of refractory hypertension with bilateral nephrectomy in a patient with chronic kidney disease stage 3

We present a case of life-threatening refractory hypertension (rHTN) in a patient with stage 3b chronic kidney disease that was unresponsive to open surgical renal denervation (RDN) but responded to bilateral nephrectomy (BLN). Both RDN and BLN reduce the increased sympathetic activation in rHTN. However, RDN has yet to show reductions in blood pressure adequate for the average patient with rHTN, and BLN has thus far been reserved for patients with preexisting end-stage kidney disease (ESKD). Our case suggests that there are patients with rHTN that warrant consideration of BLN prior to developing ESKD.

Blood pressure lowering with alcohol-mediated renal denervation using the Peregrine infusion Catheter is independent of injection site location

OBJECTIVES

The current analysis utilized core laboratory angiographic data from a prospective, single-arm, open-label, multi-center feasibility study to ascertain whether the location of alcohol infusion within main renal arteries during renal denervation (RDN) had an impact on the BP-lowering effect at 6 months.

BACKGROUND

The influence of the location of alcohol infusion during RDN, within the main renal artery (proximal, middle, or distal), on the magnitude of the blood pressure (BP) lowering is unstudied.

METHODS

The Peregrine Catheter was used to perform alcohol-mediated RDN with an infusion of 0.6 mL of alcohol per artery as the neurolytic agent in 90 main arteries and four accessory arteries of 45 patients with hypertension.

RESULTS

No relationship between the site of alcohol infusion and change from baseline in both office systolic and 24-hour systolic ambulatory BP (ABP) at 6 months was observed. When analyzed at the artery level, the least squares (LS) mean changes ± SEM from baseline to 6 months post-procedure in 24-hour systolic ABP when analyzed by renal arterial location were -11.9 ± 2.4 mmHg (distal), -10 ± 1.6 mmHg (middle), and -10.6 ± 1.3 mmHg (proximal) (all p < 0.0001 for change from baseline within groups). The results were similar for office systolic BP. There was no difference between treated locations (proximal is reference).

CONCLUSION

In this post-hoc analysis, the location of alcohol infusion within the main renal artery using the Peregrine system, with alcohol as the neurolytic agent for chemical RDN, did not affect the magnitude of BP changes at 6 months.

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.

[New opportunities of renal denervation]

Radiofrequency renal artery denervation (RND) was introduced as a method of interventional treatment of resistant hypertension almost ten years ago. The first studies demonstrated the effectiveness of this procedure. This has led to growing interest in this area and the rapid development of the method. However, the results of the first randomized trial of SYMPLICITY HTN-3 questioned the role of RND in the treatment of resistant hypertension, this fact conducted to the decrease in the recommendation class and level of evidence in the Guidelines of the European Society of Cardiology and the European Society of Hypertension in 2018. To date, the medical community is actively discussing the results of recently published trials such as SPYRAL HTN-OFF MED, SPYRAL HTN-ON MED, RADIANCE-HTN SOLO and RADIOSOUND-HTN.

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 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.

Anatomic Conformation of Renal Sympathetic Nerve Fibers in Living Human Tissues

Renal denervation using radiofrequency catheter ablation is known to eliminate the renal sympathetic nerve and to lower blood pressure in patients with resistant hypertension. We sought to investigate the detailed anatomic conformation of the peri-renal arterial sympathetic nerve fibers with living human specimens. Peri-renal arterial tissue was harvested from patients undergoing elective radical or simple nephrectomy. Digital images of each section from the distal arterial bifurcation to the proximal margin were obtained and analyzed after immunohistochemical staining with anti-tyrosine hydroxylase antibodies. A total of 3,075 nerve fibers were identified from 84 sections of peri-renal arterial tissue from 28 patients (mean age 62.5 ± 10.2 years, male 68%). Overall, 16% of nerve fibers were located at distances greater than 3 mm from the endoluminal surface of the renal artery. The median distance from the arterial lumen to the nerve fibers of the proximal, middle, and distal renal arterial segments was 1.51 mm, 1.48 mm, and 1.52 mm, respectively. The median diameter of the nerve fibers was 65 μm, and there was no significant difference between the segments. A substantial proportion of the sympathetic nerve fibers were located deeper in the peri-arterial soft tissue than in the lesion depth created by the conventional catheter-based renal sympathetic denervation system.

Renal Innervation in Resistant Hypertension: A Review of Pathophysiology and Renal Denervation as Potential Treatment

Background

Advances in treatment and increased awareness have improved the prognosis for many patients with hypertension (HTN). Resistant hypertension (RH) refers to a subset of hypertensive individuals who fail to achieve a desired blood pressure (BP) despite concurrent use of 3 different classes antihypertensive agents, one being a diuretic, and proper lifestyle changes. The prevalence and prognosis of RH are unclear owing to its heterogeneous etiologies, risk factors, and secondary comorbidities. Previous research has provided evidence that increased renal sympathetic nerve activity (RSNA) within the renal artery contributes to RH development. Renal denervation (RDN) is a procedure that attempts to ameliorate the effects of heightened RSNA via ablation renal sympathetic fibers. BP reductions associated with RDN may be attributed to decreased norepinephrine spillover, restoration of natriuresis, increasing renal blood flow, and lowering plasma renin activity. Early clinical trials perpetuated positive results, and enthusiasm grew exponentially. However, recent clinical trials have called into question RDN's efficacy. Numerous limitations must be addressed to discern the true effectiveness of RDN as a therapeutic option for RH.

Objective

We aimed to review the current understanding of RH, the anatomy of renal arteries, physiology of RH on renal arteries, anatomical pathways of the sympathetic involved in RH, RDN as a treatment option, and all relevant clinical trials treating RH with RDN.

Methods

We piloted a MEDLINE^® database search of literature extending from 1980 to 2017, with emphasis on the previous five years, combining keywords such as “resistant hypertension” and 
“renal denervation.”

Conclusion

A plethora of information is available regarding heightened RSNA leading to RH. RDN as a possible treatment option has shown a range of results. Reconciling RDN's true efficacy requires future trials to increased sites of nerve ablation, standardized protocol, increased anatomical understanding per individual basis, stricter guidelines regarding study design, increased operator experience, and integrating the use of a multielectrode catheter.

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

Aims

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

Methods and results

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

Conclusion

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

Clinical.Trials.gov identifiers

NCT01534299 and NCT01418261.

Renal sympathetic denervation restores aortic distensibility in patients with resistant hypertension: data from a multi-center trial

Renal sympathetic denervation (RDN) is under investigation as a treatment option in patients with resistant hypertension (RH). Determinants of arterial compliance may, however, help to predict the BP response to therapy. Aortic distensibility (AD) is a well-established parameter of aortic stiffness and can reliably be obtained by CMR. This analysis sought to investigate the effects of RDN on AD and to assess the predictive value of pre-treatment AD for BP changes. We analyzed data of 65 patients with RH included in a multicenter trial. RDN was performed in all participants. A standardized CMR protocol was utilized at baseline and at 6-month follow-up. AD was determined as the change in cross-sectional aortic area per unit change in BP. Office BP decreased significantly from 173/92 ± 24/16 mmHg at baseline to 151/85 ± 24/17 mmHg (p < 0.001) 6 months after RDN. Maximum aortic areas increased from 604.7 ± 157.7 to 621.1 ± 157.3 mm² (p = 0.011). AD improved significantly by 33% from 1.52 ± 0.82 to 2.02 ± 0.93 × 10⁻³ mmHg⁻¹ (p < 0.001). Increase of AD at follow-up was significantly more pronounced in younger patients (p = 0.005) and responders to RDN (p = 0.002). Patients with high-baseline AD were significantly younger (61.4 ± 10.1 vs. 67.1 ± 8.4 years, p = 0.022). However, there was no significant correlation of baseline AD to response to RDN. AD is improved after RDN across all age groups. Importantly, these improvements appear to be unrelated to observed BP changes, suggesting that RDN may have direct effects on the central vasculature.

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.

Renal Denervation: Paradise Lost? Paradise Regained?

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

Effect of applied energy in renal sympathetic denervation with magnetic resonance guided focused ultrasound in a porcine model

Background

Past catheter-based and focused ultrasound renal denervation studies have indicated that procedure efficacy is related to the number of ablations performed or the amount of energy used for the ablation. This study extends those prior results and investigates energy level effects on the efficacy of MR guided focused ultrasound renal denervation performed in a porcine model.

Methods

Twenty-four normotensive pigs underwent unilateral denervation at three intensity levels. The applied intensity level was retrospectively de-rated to account for variability in animal size. Efficacy was assessed through evaluating the norepinephrine present in the kidney medulla and through histological analysis. The treatment was performed under MRI guidance including pre- and post-procedure T1-weighted and quantitative T1 and T2 imaging. During treatment, the temperature in the near field of the ultrasound beam was monitored in real time with MR temperature imaging. Energy delivery in the regions surrounding the renal artery was independently confirmed through an invasive fiberoptic temperature probe placed in the right renal artery.

Results

Animals that underwent denervation at a de-rated acoustic intensity of greater than 1.2 kW/cm² had a significantly lower norepinephrine concentration in the kidney indicating successful denervation. Images obtained during the treatment indicated no tissue changes in the kidneys as a function of the procedure but there were significant T1 changes present in the right lumbar muscles, although only one animal had indication of muscle damage at the time of necropsy.

Conclusions

While MR guided focused ultrasound renal denervation was found to be safe and effective in this normotensive animal model, the results indicated the need to incorporate patient-specific details in the treatment planning of MRgFUS renal denervation procedure.

Anti-Inflammatory Effects and Prediction of Blood Pressure Response by Baseline Inflammatory State in Catheter-Based Renal Denervation

This retrospective analysis aimed to examine off-target effects on inflammatory and renal function parameters in n=78 subsequent patients treated with renal denervation (RDN) for resistant hypertension. Ambulatory and office blood pressure (ABP/OBP), serum creatinine, glomerular filtration rate (GFR), cystatin C, C-reactive protein (CRP), interleukin-6 (IL-6), and white blood cell count (WBC) were assessed before, 6 and 12 months after RDN. ABP was significantly reduced by -8.2/-3.8 mm Hg (P=.002/.021) at 1 year after RDN, while an initial OBP reduction was not sustained during follow-up. IL-6 levels significantly decreased by -0.5 pg/mL (P=.042) and by -1.7 pg/mL (P<.001) at 6 and 12 months, baseline IL-6 levels possibly predicting ABP response to RDN (r=-0.295; P=.020). Concurrently, leukocyte count was reduced by -0.5 × 103 /μL (P=.017) and -0.8 × 103 /μL (P<.001), respectively. Serum creatinine and GFR remained unchanged, but we observed a significant increase in cystatin C by 0.04 mg/L (P=.026) and 0.14 mg/L (P<.001) at 6 and 12 months after the intervention.

Adherence to Antihypertensive Treatment and the Blood Pressure–Lowering Effects of Renal Denervation in the Renal Denervation for Hypertension (DENERHTN) Trial

Background:

The DENERHTN trial (Renal Denervation for Hypertension) confirmed the blood pressure–lowering efficacy of renal denervation added to a standardized stepped-care antihypertensive treatment for resistant hypertension at 6 months. We report the influence of adherence to antihypertensive treatment on blood pressure control.

Methods:

One hundred six patients with hypertension resistant to 4 weeks of treatment with indapamide 1.5 mg/d, ramipril 10 mg/d (or irbesartan 300 mg/d), and amlodipine 10 mg/d were randomly assigned to renal denervation plus standardized stepped-care antihypertensive treatment, or the same antihypertensive treatment alone. For standardized stepped-care antihypertensive treatment, spironolactone 25 mg/d, bisoprolol 10 mg/d, prazosin 5 mg/d, and rilmenidine 1 mg/d were sequentially added at monthly visits if home blood pressure was ≥135/85 mm Hg after randomization. We assessed adherence to antihypertensive treatment at 6 months by drug screening in urine/plasma samples from 85 patients.

Results:

The numbers of fully adherent (20/40 versus 21/45), partially nonadherent (13/40 versus 20/45), or completely nonadherent patients (7/40 versus 4/45) to antihypertensive treatment were not different in the renal denervation and the control groups, respectively ( P =0.3605). The difference in the change in daytime ambulatory systolic blood pressure from baseline to 6 months between the 2 groups was –6.7 mm Hg ( P =0.0461) in fully adherent and –7.8 mm Hg ( P =0.0996) in nonadherent (partially nonadherent plus completely nonadherent) patients. The between-patient variability of daytime ambulatory systolic blood pressure was greater for nonadherent than for fully adherent patients.

Conclusions:

In the DENERHTN trial, the prevalence of nonadherence to antihypertensive drugs at 6 months was high (≈50%) but not different in the renal denervation and control groups. Regardless of adherence to treatment, renal denervation plus standardized stepped-care antihypertensive treatment resulted in a greater decrease in blood pressure than standardized stepped-care antihypertensive treatment alone.

Clinical Trial Registration:

URL: http://www.clinicaltrials.gov . Unique identifier: NCT01570777.

Clinical neurocardiology defining the value of neuroscience-based cardiovascular therapeutics

The autonomic nervous system regulates all aspects of normal cardiac function, and is recognized to play a critical role in the pathophysiology of many cardiovascular diseases. As such, the value of neuroscience-based cardiovascular therapeutics is increasingly evident. This White Paper reviews the current state of understanding of human cardiac neuroanatomy, neurophysiology, pathophysiology in specific disease conditions, autonomic testing, risk stratification, and neuromodulatory strategies to mitigate the progression of cardiovascular diseases.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

The rise, fall, and possible resurrection of renal denervation

Renal denervation has a chequered history. Dramatic reductions in blood pressure after denervation of the renal arteries were observed in early trials, but later trials in which denervation was tested against a sham procedure produced neutral results. Although a sound pathophysiological basis exists for interruption of the renal sympathetic nervous system as a treatment for hypertension, trial data to date are insufficient to support renal denervation as an established clinical therapy. In this Perspectives article, we summarize the currently available trial data, device development, and trials in progress, and provide recommendations for future trial design.

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.

Reductions of left ventricular mass and atrial size following renal denervation: a meta-analysis

BACKGROUND

Renal denervation (RDN), a novel therapy for resistant hypertension, has been shown to have an effect on cardiac remodeling in several small studies. We aimed to pool currently available data to assess the effects of RDN on left ventricular hypertrophy (LVH) and left atrial (LA) enlargement.

METHODS AND RESULTS

Two investigators independently searched PubMed, EMBASE and Cochrane Library Central Register of Controlled Trials database for studies reporting change in left ventricular mass index (LVMI) or LA size before and after RDN. Twelve publications met our pre-defined inclusion criteria. Echocardiographic data showed that RDN markedly reduced both LVMI [weighted mean difference (WMD) = -15.77 g/m(2); 95 % confidence interval (CI) -22.51 to -9.02 g/m(2)] and LA diameter [WMD = -2.48 mm; 95 % CI -4.12 to -0.83 mm] after 6 months. Data from cardiac magnetic resonance also showed a significant reduction in LVMI [WMD = -5.43 g/m(2), 95 % CI -10.01 to -0.35 g/m(2)) at 6 months. Changes in LVH and LA size at 12 months were more pronounced than those at 6 months. Meta-regression analysis failed to demonstrate a significant relationship between RDN-induced LVMI reduction and BP lowering at 6 months.

CONCLUSIONS

RDN led to significant regressions of both LVH and LA enlargement at 6 months, which were sustained at least up to 12 months.

Renal denervation: Not as easy as it looks

Renal sympathetic denervation with intravascular radiofrequency catheters in hypertensive patients is less effective than anticipated, owing to radio frequency energy being applied to a part of the renal artery where the nerves are at the greatest distance from the aortic lumen and to distortion of energy distribution and temperature gradients by regional tissue anatomical variations (Tzafriri et al., this issue).

Renal artery sympathetic denervation: observations from the UK experience

Background

Renal denervation (RDN) may lower blood pressure (BP); however, it is unclear whether medication changes may be confounding results. Furthermore, limited data exist on pattern of ambulatory blood pressure (ABP) response—particularly in those prescribed aldosterone antagonists at the time of RDN.

Methods

We examined all patients treated with RDN for treatment-resistant hypertension in 18 UK centres.

Results

Results from 253 patients treated with five technologies are shown. Pre-procedural mean office BP (OBP) was 185/102 mmHg (SD 26/19; n = 253) and mean daytime ABP was 170/98 mmHg (SD 22/16; n = 186). Median number of antihypertensive drugs was 5.0: 96 % ACEi/ARB; 86 % thiazide/loop diuretic and 55 % aldosterone antagonist. OBP, available in 90 % at 11 months follow-up, was 163/93 mmHg (reduction of 22/9 mmHg). ABP, available in 70 % at 8.5 months follow-up, was 158/91 mmHg (fall of 12/7 mmHg). Mean drug changes post RDN were: 0.36 drugs added, 0.91 withdrawn. Dose changes appeared neutral. Quartile analysis by starting ABP showed mean reductions in systolic ABP after RDN of: 0.4; 6.5; 14.5 and 22.1 mmHg, respectively (p < 0.001 for trend). Use of aldosterone antagonist did not predict response (p > 0.2).

Conclusion

In 253 patients treated with RDN, office BP fell by 22/9 mmHg. Ambulatory BP fell by 12/7 mmHg, though little response was seen in the lowermost quartile of starting blood pressure. Fall in BP was not explained by medication changes and aldosterone antagonist use did not affect response.

Electronic supplementary material

The online version of this article (doi:10.1007/s00392-015-0959-4) contains supplementary material, which is available to authorized users.

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.

Atrial Remodeling Following Catheter-Based Renal Denervation Occurs in a Blood Pressure- and Heart Rate-Independent Manner

OBJECTIVES

This study sought to investigate left atrial (LA) remodeling in relation to blood pressure (BP) and heart rate (HR) after renal sympathetic denervation (RDN).

BACKGROUND

In addition to reducing BP and HR in certain patients with hypertension, RDN can decrease left ventricular (LV) mass and ameliorate LV diastolic dysfunction.

METHODS

Before and 6 months after RDN, BP, HR, LV mass, left atrial volume index (LAVI), diastolic function (echocardiography), and premature atrial contractions (PAC) (Holter electrocardiogram) were assessed in 66 patients with resistant hypertension.

RESULTS

RDN reduced office BP by 21.6 ± 3.0/10.1 ± 2.0 mm Hg (p < 0.001), and HR by 8.0 ± 1.3 beats/min (p < 0.001). At baseline, LA size correlated with LV mass, diastolic function, and pro-brain natriuretic peptide, but not with BP or HR. Six months after RDN, LAVI was reduced by 4.0 ± 0.7 ml/kg/m(2) (p < 0.001). LA size decrease was stronger when LAVI at baseline was higher. In contrast, the decrease in LAVI was not dependent on LV mass or diastolic function (E/E' or E/A) at baseline. Furthermore, LAVI decreased without relation to decrease in systolic BP or HR. Additionally, occurrence of PAC (median of >153 PAC/24 h) was reduced (to 68 PAC/24 h) by RDN, independently of changes in LA size.

CONCLUSIONS

In patients with resistant hypertension, LA volume and occurrence of PAC decreased 6 months after RDN. This decrease was independent of BP and HR at baseline or the reduction in BP and HR reached by renal denervation. These data suggest that there is a direct, partly BP-independent effect of RDN on cardiac remodeling and occurrence of premature atrial contractions.