Catheter-based renal denervation for resistant hypertension: Twenty-four month results of the EnligHTN I first-in-human study using a multi-electrode ablation system

Patient-Specific Factors Predicting Renal Denervation Response in Patients With Hypertension: A Systematic Review and Meta-Analysis

BACKGROUND

The accurate selection of patients likely to respond to renal denervation (RDN) is crucial for optimizing treatment outcomes in patients with hypertension. This systematic review was designed to evaluate patient-specific factors predicting the RDN response.

METHODS AND RESULTS

We focused on individuals with hypertension who underwent RDN. Patients were categorized based on their baseline characteristics. The primary outcome was blood pressure (BP) reduction after RDN. Both randomized controlled trials and nonrandomized studies were included. We assessed the risk of bias using corresponding tools and further employed the Grading of Recommendations Assessment, Development, and Evaluation approach to assess the overall quality of evidence. A total of 50 studies were ultimately included in this systematic review, among which 17 studies were for meta-analysis. Higher baseline heart rate and lower pulse wave velocity were shown to be associated with significant antihypertensive efficacy of RDN on 24-hour systolic BP reduction (weighted mean difference, -4.05 [95% CI, -7.33 to -0.77]; weighted mean difference, -7.20 [95% CI, -9.79 to -4.62], respectively). In addition, based on qualitative analysis, higher baseline BP, orthostatic hypertension, impaired baroreflex sensitivity, and several biomarkers are also reported to be associated with significant BP reduction after RDN.

CONCLUSIONS

In patients with hypertension treated with the RDN, higher heart rate, and lower pulse wave velocity were associated with significant BP reduction after RDN. Other factors, including higher baseline BP, hypertensive patients with orthostatic hypertension, BP variability, impaired cardiac baroreflex sensitivity, and some biomarkers are also reported to be associated with a better BP response to RDN.

Renal denervation for the treatment of hypertension and kidney disease

PURPOSE OF REVIEW

Hypertension is a condition characterized by increased sympathetic activity and the autonomic nervous system. Resistant hypertension, a condition with a prevalence of 10% to 20% in the general hypertensive population, is more likely to experience poor outcomes and adverse cardiovascular events. Renal sympathetic denervation (RDN), a minimally invasive, catheter-based percutaneous intervention, has been considered for treating this condition. Clinical trials have used various catheters, such as the Symplicity Spyral catheter, Vessix Renal Denervation system, and Paradise endovascular ultrasound renal denervation system.

RECENT FINDINGS

After the first randomized clinical trials examining the effectiveness and safety of RDN for lowering blood pressure in hypertensive patients, new clinical trials have used various catheters based on radiofrequency, such as the Spyral catheter, Vessix Renal Denervation system, or based on radiofrequency as the Paradise endovascular ultrasound renal denervation system. Positive results on this trials have shown that endovascular RDN (radiofrequency energy or high focused ultrasound energy) could be considered as a treatment option for uncontrolled resistant hypertension.

SUMMARY

Therefore, endovascular RDN (radiofrequency energy or high focused ultrasound energy) could be considered as a treatment option for uncontrolled resistant hypertension, which can be considered as an alternative to increasing medication. Nevertheless more data are needed, mainly in cardiovascular outcomes. RDN should be performed in experienced and specialized centers with a multidisciplinary team, and the benefits and risks of RDN should be addressed in a shared-decision-making process.

New Drugs and Interventional Strategies for the Management of Hypertension

Essential hypertension is an important cause of cardiovascular morbidity and mortality worldwide with significant clinical and economic implications. The field of antihypertensive treatment already numbers numerous agents and classes of drugs. However, patients are still developing uncontrolled hypertension. Hence there is a continuous need for novel agents with good tolerability. Advances in this field are focusing both on pharmacotherapy, with the developments in traditional and non-traditional targets, as well as interventional techniques such as renal denervation and baroreflex activation therapy. It is likely that future strategies may involve a tailored approach to the individual patient, with genetic modulation playing a key role.

Recent advances in managing primary hypertension

Hypertension remains a leading risk factor for cardiovascular mortality and morbidity globally despite the availability of effective and well-tolerated antihypertensive medications. Accumulating evidence suggests a more aggressive blood pressure regulation aimed at lower targets, particularly for selected patient groups. Our concepts of the optimal method for blood pressure measurement have radically changed, maintaining appropriate standard office measurements for initial assessment but relying on out-of-office measurement to better guide our decisions. Thorough risk stratification provides guidance in decision making; however, an individualized approach is highly recommended to prevent overtreatment. Undertreatment, on the other hand, remains a major concern and is mainly attributed to poor adherence and resistant or difficult-to-control forms of the disease. This review aims to present modern perspectives, novel treatment options, including innovative technological applications and developing interventional and pharmaceutical therapies, and the major concerns emerging from several years of research and epidemiological observations related to hypertension management.

Animal model evaluation of a novel renal denervation system for future laparoscopic treatment of resistant hypertension

Purpose

Although percutaneous catheter-based ablation of renal sympathetic nerve fibers has been used in the treatment of patients with resistant hypertension, a recent phase III study did not confirm its efficacy. In this study, we developed a novel laparoscopic renal denervation system and evaluated its safety and initial feasibility using an animal model.

Materials and Methods

A novel surgical instrument that uses a smart algorithm with temperature-monitoring feedback was developed. We used 4 male pigs (6 weeks old, weighing approximately 45 kg each) to evaluate the safety and efficacy of the laparoscopic renal denervation system. We performed immunohistochemical staining analysis after renal denervation using various tip temperatures and over various durations through an open approach.

Results

When the temperature of the outer wall of the renal artery was maintained at 90℃ for 180 seconds, the artery was completely denervated without damaging its inner layer, as evaluated using Masson's trichrome staining. When the temperature ranged from 70℃ to 90℃ and the duration ranged from 90 to 420 seconds, partial or complete denervation without significant vessel injury was confirmed with anti- growth-associated protein 43 and anti-S100 staining.

Conclusions

This animal study confirmed the safety and feasibility of the novel laparoscopic renal denervation system. A safe and effective protocol was developed with ablation at a constant tissue temperature of 70℃ to 90℃ within 180 seconds. However, further developments are necessary before its clinical use.

The safety of renal denervation as assessed by optical coherence tomography: pre- and post-procedure comparison with multi-electrode ablation catheter in animal experiment

OBJECTIVE

To prove the effectiveness and safety of multi-electrode ablation catheter in renal denervation (RDN) by optical coherence tomography (OCT).

METHODS

Sixteen renal arteries were enrolled from 8 pigs. Angiography and OCT were performed to analyze the morphological changes before RDN and at 1-month follow-up. Blood pressure and creatinine were measured to prove the effectiveness and safety of the catheter.

RESULTS

One renal artery was excluded because of the small diameter. Fifteen renal arteries successfully underwent renal denervation and OCT. Mean blood pressure was significantly reduced at 1 month after RDN (122.40 ± 3.54 mmHg vs. 106.50 ± 2.06 mmHg, n = 8, P < .001). Creatinine follow-up after 1 month showed no significant change (45.37 ± 7.44 vs. 65.87 ± 49.20 μmol/L, n = 8, P = 0.275). The minimal lumen diameter showed that the renal artery immediately narrowed after the procedure (7.17 ± 0.60 mm vs. 5.93 ± 0.97 mm, n = 15, P < .001). Vasospasm, vascular wall edemas, and thrombus formations all showed significant changes after the procedure except renal artery dissection (0% vs. 21.4%, P = 0.067) under the OCT. Adverse event as renal artery occluded showed no significant difference (0% vs. 6.7%, P > .05). OCT results showed no significant difference in vasospasm, dissections, wall edemas, and thrombus formations (P > .05) at 1 month after the procedure.

CONCLUSION

This multi-electrode ablation catheter could cause minor injury to renal artery instantly after RDN, but it is found to be safe in the animal model at 1-month follow-up.

Evaluation of later morphologic alterations in renal artery wall and renal nerves in response to catheter-based renal denervation in sheep: comparison of the single-point and multiple-point ablation catheters

This study evaluated the subacute morphologic alterations in renal artery wall and renal nerves in response to catheter-based renal denervation (RDN) in sheep and also compared the efficiency of single-point and multiple-point ablation catheters. Effect of each ablation catheter approved for the clinical use (Symplicity Flex(TM), Medtronic, Inc., or EnligHTN(TM), St. Jude Medical, INC.) was compared to intact contralateral renal artery in 12 sheep by histopathology and immunohistochemistry evaluation after a 10-day period post-RDN procedure. The safety was verified by extensive evaluation of kidney morphology. Vascular wall lesions and nerve injuries were more pronounced in those animals treated with multi-point EnligHTN catheter when compared with animals treated with single-point Symplicity Flex catheter. However, neither RDN procedure led to complete renal nerve ablation. Both systems, tested in the present study, provided only incomplete renal nerve ablation in sheep. Moreover, no appreciable progression of the nerve disintegration in subacute phase post-RDN procedure was observed. This study further supports the notion that the effectiveness remains fully dependent on anatomical inter-individual variability of the sympathetic nerve plexus accompanying the renal artery. Therefore, new systems providing deeper penetrance to targeted perivascular structure would be more efficient.

Comparison of two different radiofrequency ablation systems for renal artery denervation: Evaluation of short-term and long-term follow up

Objectives

To assess the clinical efficacy of renal artery denervation (RAD) in our center and to compare the efficacy of two different radiofrequency (RF) systems.

Background

Several systems are available for RF renal denervation. Whether there is a difference in clinical efficacy among various systems remains unknown.

Methods

Renal artery denervation was performed on 43 patients with resistant hypertension using either the single electrode Symplicity Flex (n = 20) or the multi‐electrode EnligHTN system (n = 23). Median post‐procedural follow‐up was 32.93 months. The primary outcome was post‐procedural change in office blood pressure (BP) within 1 year (short‐term follow‐up). Secondary outcomes were change in office BP between 1 and 4 years (long‐term follow‐up) and the difference in office BP reduction between the two systems at each follow‐up period.

Results

For the total cohort, mean baseline office BP (systolic/diastolic) was 174/94 mmHg. At follow‐up, mean changes in office BP from baseline were −19.70/−11.86 mmHg (P < 0.001) and −21.90/−13.94 mmHg (P < 0.001) for short‐term and long‐term follow‐up, respectively. The differences in office BP reduction between Symplicity and EnligHTN groups were 8.96/1.23 mmHg (P = 0.42 for systolic BP, P = 0.83 for diastolic BP) and 9.56/7.68 mmHg (P = 0.14 for systolic BP, P = 0.07 for diastolic BP) for short‐term and long‐term follow‐up, respectively.

Conclusions

In our cohort, there was a clinically significant office BP reduction after RAD, which persisted up to 4 years. No significant difference in office BP reduction between the two systems was found.

Renal Denervation by Transaortic Periarterial Ethanol Injection: An Experimental Study in Porcines

AIMS

To evaluate the feasibility, safety and efficacy of renal sympathetic denervation via endoluminal transaortic periarterial ethanol injection.

METHODS AND RESULTS

In 11 normotensive pigs transaortic puncture was performed with a 90-cm 21G needle with subsequent unilateral ethanol injection to the periarterial space. Needle placement was achieved using a 7F steerable sheath fluoroscopically positioned slightly above the renal artery origin. Blood pressure measurements and abdominal CT scans were performed immediately pre- and postintervention and 4 weeks later. After euthanasia norepinephrine concentration of both kidneys (RTNEC) was determined and renal arteries and surrounding tissues histologically examined to assess induced nerve fibre degeneration.

RESULTS

All but one procedure were technically successful. One major complication with accidental ethanol injection into the renal artery and subsequent infarction occurred. One pig died from no intervention-related cardiac arrest. The 4-week follow-up was uneventful in the remaining 10 animals. RTNEC was significantly lower on the treated side in eight of ten pigs (mean decrease 36.6%) with correlating histopathological signs of nerve degeneration.

CONCLUSIONS

Renal sympathicolysis by transaortic periarterial ethanol injection was feasible and effective in a porcine model. This approach may be an alternative to catheter-based RFA or other methods of renal denervation.

Cardiovascular morbidity of severe resistant hypertension among treated uncontrolled hypertensives: a 4-year follow-up study

Data regarding the prognosis of resistant hypertension (RHTN) with respect to its severity is limited. We investigated the cardiovascular risk of severe RHTN in a prospective observational study. A cohort of 1700 hypertensive patient with treated uncontrolled HTN was followed for a mean period of 3.6 ± 1.8 years. At baseline, standard clinical and laboratory workup was performed, including testing for secondary causes of RHT where applicable. Three groups were identified depending on presence of RHTN (office-based uncontrolled HTN under at least three drugs including a diuretic) and levels of office systolic blood pressure (BP): 1187 patients (70%) without RHTN, 313 (18%) with not-severe RHTN (systolic BP < 160 mmHg) and 200 (12%) with severe RHTN (systolic BP ≥ 160 mmHg). Endpoint of interest was cardiovascular morbidity set as the composite of coronary heart disease and stroke. During follow-up, incidence rates of cardiovascular events per 1000 person-years were 7.1 cases in the non-RHTN group, 12.4 cases in the not-severe RHTN group and 18 cases in the severe RHTN group. Unadjusted analysis showed that compared to uncontrolled patients without RHTN, patients with not-severe RHTN exhibited a similar risk but patients with severe RHTN had a significantly higher risk, by 2.5 times (CI: 1.28-4.73, p = 0.007). Even after multivariate adjustment for established risk factors including BP levels and isolated systolic HTN, severe RHTN remained as an independent predictor of the cardiovascular outcome (OR: 2.30, CI: 1.00-5.29, p = 0.05). In conclusion, among treated yet uncontrolled hypertensive patients, severe RHTN exhibits a significantly higher cardiovascular risk indicating the need for prompt management.

High screen failure rate in patients with resistant hypertension: Findings from SYMPLICITY HTN-3

BACKGROUND

The SYMPLICITY HTN-3 trial, which randomized subjects to renal denervation (RDN) or sham control, was designed to evaluate the efficacy and safety of RDN for the treatment of resistant hypertension. Outcomes were previously reported. This retrospective analysis evaluated reasons for screen failure (SF) for randomization in the trial.

METHODS

SYMPLICITY HTN-3 enrolled subjects with office systolic blood pressure (SBP) ≥160 mmHg on stable and maximal doses of ≥3 antihypertensive medication classes. Blood pressure was measured during screening visit (SV) 1 and SV2 a minimum of 2 weeks later to ensure resistant hypertension and to exclude white-coat hypertension. We analyzed baseline characteristics and reasons for SF at each SV and changes in BP between SVs.

RESULTS

Among 1,415 patients screened, 880 (62%) did not meet criteria for randomization. Compared with randomized patients, those in the SF cohort were more likely to be older (58.7 vs. 57.4 years, P=.029), current smokers (14.5% vs. 10.7%, P=.041), and prescribed fewer antihypertensive medications (4.7 vs. 5.1, P<.001). The predominant reason for SF at SV2 was office SBP <160 mmHg despite office SBP ≥160 mmHg at SV1.

CONCLUSION

Screening patients with resistant hypertension on maximal doses of ≥3 antihypertensive drugs led to a high SF rate. Screen failures were most common at SV1 and were due to failing the office SBP entry criteria. Not meeting ambulatory SBP criteria at SV2 was a secondary reason for SF, often due to white-coat hypertension; thus, 24-hour ambulatory monitoring is important to validate resistant hypertension.

Endovascular ultrasound for renal sympathetic denervation in patients with therapy-resistant hypertension not responding to radiofrequency renal sympathetic denervation

AIMS

Recent studies have reported a considerable number of non-responders after renal sympathetic de-nervation (RSD) with radiofrequency technology. Here we report our results of repeat RSD using ultrasound in these patients.

METHODS AND RESULTS

A cohort study was performed in patients who underwent ultrasound RSD after non-response to RSD with radiofrequency. Non-response was defined as mean daytime systolic blood pressure ≥140 mmHg and/or a reduction of ≤10 mmHg in ambulatory blood pressure measurement (ABPM) ≥6 months after radiofrequency denervation. ABPM was recorded at baseline, post radiofrequency RSD as well as at three and six months post ultrasound RSD. A total of 24 non-responders underwent retreatment with the ultrasound device at a mean 15.3±8.2 months after radiofrequency RSD. Ultrasound RSD was performed successfully in all patients without severe adverse events. Mean daytime systolic blood pressure changed from 161.7±14.6 mmHg at baseline to 158.5±9.5 mmHg post radiofrequency RSD and to 150.5±10.4 mmHg and 151.6±11.0 mmHg at three and six months, respectively, post ultrasound RSD (p<0.01 with repeated measures analysis of variance). The main results of post hoc testing were as follows: baseline versus post radiofrequency RSD, p=0.83; baseline versus three months post ultrasound RSD, p=0.01; and baseline versus six months post ultrasound RSD, p=0.04.

CONCLUSIONS

Ultrasound RSD appears to be safe and an effective therapeutic approach in patients not responding to previous RSD with radiofrequency technology.

Early morphologic alterations in renal artery wall and renal nerves in response to catheter-based renal denervation procedure in sheep: difference between single-point and multiple-point ablation catheters

Renal sympathetic hyperactivity is critically involved in hypertension pathophysiology; renal denervation (RDN) presents a novel strategy for treatment of resistant hypertension cases. This study assessed effects of two RDN systems to detect acute intravascular, vascular and peri-vascular changes in the renal artery, and renal nerve alterations, in the sheep. The procedures using a single-point or multi-point ablation catheters, Symplicity Flex(TM), Medtronic versus EnligHTN(TM), St. Jude Medical were compared; the intact contralateral kidneys served as controls. Histopathological and immunohistochemical assessments were performed 48 h after RDN procedures; the kidney and suprarenal gland morphology was also evaluated. Special staining methods were applied for histologic analysis, to adequately score the injury of renal artery and adjacent renal nerves. These were more pronounced in the animals treated with the multi-point compared with the single-point catheter. However, neither RDN procedure led to complete renal nerve ablation. Forty-eight hours after the procedure no significant changes in plasma and renal tissue catecholamines were detected. The morphologic changes elicited by application of both RDN systems appeared to be dependent on individual anatomical variability of renal nerves in the sheep. Similar variability in humans may limit the therapeutic effectiveness of RDN procedures used 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.

Renal Artery Vasodilation May Be An Indicator of Successful Sympathetic Nerve Damage During Renal Denervation Procedure

Autonomic nervous system plays a crucial role in maintaining and regulating vessel tension. Renal denervation (RDN) may induce renal artery vasodilation by damaging renal sympathetic fibers. We conducted this animal study to evaluate whether renal artery vasodilation could be a direct indicator of successful RDN. Twenty-eight Chinese Kunming dogs were randomly assigned into three groups and underwent RDN utilizing temperature-controlled catheter (group A, n = 11) or saline-irrigated catheter (group B, n = 11) or sham procedure (group C, n = 6). Renal angiography, blood pressure (BP) and renal artery vasodilation measurements were performed at baseline, 30-minute, 1-month, and 3-month after interventions. Plasma norepinephrine concentrations were tested at baseline and 3-month after intervention. Results showed that, in addition to significant BP reduction, RDN induced significant renal artery vasodilation. Correlation analyses showed that the induced renal artery vasodilation positively correlated with SBP reduction and plasma norepinephrine reduction over 3 months after ablation. Post hoc analyses showed that saline-irrigated catheter was superior to TC catheter in renal artery vasodilation, especially for the acute dilatation of renal artery at 30-minute after RDN. In conclusion, renal artery vasodilation, induced by RDN, may be a possible indicator of successful renal nerve damage and a predictor of blood pressure response to RDN.

Renal sympathetic denervation in therapy resistant hypertension - pathophysiological aspects and predictors for treatment success

Many forms of human hypertension are associated with an increased systemic sympathetic activity. Especially the renal sympathetic nervous system has been found to play a prominent role in this context. Therefore, catheter-interventional renal sympathetic denervation (RDN) has been established as a treatment for patients suffering from therapy resistant hypertension in the past decade. The initial enthusiasm for this treatment was markedly dampened by the results of the Symplicity-HTN-3 trial, although the transferability of the results into clinical practice to date appears to be questionable. In contrast to the extensive use of RDN in treating hypertensive patients within or without clinical trial settings over the past years, its effects on the complex pathophysiological mechanisms underlying therapy resistant hypertension are only partly understood and are part of ongoing research. Effects of RDN have been described on many levels in human trials: From altered systemic sympathetic activity across cardiac and metabolic alterations down to changes in renal function. Most of these changes could sustainably change long-term morbidity and mortality of the treated patients, even if blood pressure remains unchanged. Furthermore, a number of promising predictors for a successful treatment with RDN have been identified recently and further trials are ongoing. This will certainly help to improve the preselection of potential candidates for RDN and thereby optimize treatment outcomes. This review summarizes important pathophysiologic effects of renal denervation and illustrates the currently known predictors for therapy success.

Chronic Kidney Disease As a Potential Indication for Renal Denervation

Renal denervation is being used as a blood pressure lowering therapy for patients with apparent treatment resistant hypertension. However, this population does not represent a distinct disease condition in which benefit is predictable. In fact, the wide range in effectiveness of renal denervation could be a consequence of this heterogeneous pathogenesis of hypertension. Since renal denervation aims at disrupting sympathetic nerves surrounding the renal arteries, it seems obvious to focus on patients with increased afferent and/or efferent renal sympathetic nerve activity. In this review will be argued, from both a pathophysiological and a clinical point of view, that chronic kidney disease is particularly suited to renal denervation.

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.