Expert consensus: Renal denervation for the treatment of hypertension. Diagn Interv Imaging. 2012;93:386-394. [PMID: 22560124 DOI: 10.1016/j.diii.2012.03.013]

Neuromodulation Therapy in Heart Failure: Combined Use of Drugs and Devices

Heart failure (HF) is the fastest-growing cardiovascular disease globally. The autonomic nervous system plays an important role in the regulation and homeostasis of cardiac function but, once there is HF, it takes on a detrimental role in cardiac function that makes it a rational target. In this review, we cover the remodeling of the autonomic nervous system in HF and the latest treatments available targeting it.

Renal Denervation: A Novel Therapy at the Crossroads of Imaging, Intervention, and Innovation

Hypertension (HTN) is one of the most significant medical problems affecting society today. The estimated 76 million Americans with hypertension represent a significant public health problem, contributing to cardiac, vascular, renal, and neurovascular morbidity and mortality. HTN is the most common indication for lifelong pharmacologic treatment, mainly because of the incontrovertible reductions in cardiovascular events with blood pressure (BP) reduction and control. However, despite the availability and potency of multiple different antihypertensive drugs, up to half of American patients have BPs above the recommended target. Given the overwhelming evidence of both the cost to society of HTN and the benefits that are accrued from improved BP control, alternatives or adjuncts to current management options have been sought to aid in treatment of these patients. Over the past few years, a device-based approach involving modulation of the autonomic nervous system, termed renal denervation, has evolved to meet this challenge. With early trials showing startlingly good results, with few side effects, multiple devices were fast-tracked to clinical trials and hence to the market. However, larger trials have shone an unfavorable light on the field, with concerns about the short- and long-term effectiveness, diverting attention back to operational and procedural details. Despite this, image-guided manipulation of the sympathetic nervous system to treat HTN remains a fertile area of laboratory and clinical research.

[Post-denervation renal artery stenosis - a matter of concern?]

Renal denervation, an invasive technique indicated in resistant hypertension patients insufficiently controlled by antihypertensive drugs, has a good safety profile. However, an increasing number of post-denervation renal artery stenosis cases has recently been reported. We describe the case of a 49-year-old woman with resistant hypertension who was referred to our university hypertension center for renal sympathetic denervation. Her daily treatment included six antihypertensive drugs. CT angiography prior to denervation showed no renal artery stenosis or vessel wall lesions. A standard renal denervation procedure using the St Jude protocol was performed. After an initial improvement in blood pressure profile, she presented with a blood pressure impairment at 3 months after renal denervation leading to the diagnosis of a severe right renal artery stenosis.

[New invasive therapies for management of resistant hypertension]

The failure of pharmacological approaches to treat resistant hypertension has stimulated interest in invasive device-based treatments. New catheter systems using radiofrequency or ultrasound energy have been developed, allowing a percutaneous endovascular approach to renal denervation for patients with resistant hypertension. To date, this technique has been evaluated only in a few open-label trials including small numbers and the available evidence suggests a favorable blood pressure-lowering effect in the short-term and a low incidence of immediate complications. All studies published to date have several limitations due to their open-label design. Carotid baroreceptor stimulation requires surgical implantation of electrodes connected to a stimulator. Preliminary results show a positive effect on blood pressure with a complication rate similar to the implantation of a pacemaker. In this context, there are arguments against an uncontrolled use of these procedures in routine practice: an unknown benefit/risk ratio, a variable blood pressure response, absence of cost-effectiveness evaluation. The indications of these procedures should follow the 2013 European Society of Hypertension guidelines. A strict follow-up of patients remains necessary at best by including them in clinical trials or international registries.

MR-guided high-focused ultrasound for renal sympathetic denervation-a feasibility study in pigs

Background

Renal sympathetic denervation has recently gained clinical relevance for the treatment of therapy-resistant hypertension. Denervation is currently mainly performed using catheter-based transarterial radiofrequency ablation of periarterial sympathetic nerve fibers. Since this approach has numerous limitations, we conducted a study to evaluate the feasibility, safety, and efficacy of magnetic resonance-guided high-focused ultrasound (MRgHiFUS) for renal sympathetic denervation in pigs as an alternative to catheter-based ablation.

Methods

Renal periarterial MRgHiFUS was performed under general anesthesia in ten pigs. Blood pressure measurements and magnetic resonance imaging (MRI) of the kidneys, renal arteries, and surrounding structures were obtained immediately before and after the interventions and after 4 weeks. Histological examinations of periarterial tissues and determination of renal norepinephrine (NE) concentration were performed to assess treatment efficacy.

Results and discussion

In each pig, 9.8 ± 2.6 sonications with a mean energy deposition of 2,670 ± 486 J were performed. The procedure was well tolerated by all pigs. No major complications occurred. MRgHiFUS induced periarterial edema in three pigs, but only one pig showed corresponding histological changes. The NE level of the treated kidney was lower in five pigs (-8% to -38%) compared to the untreated side. Overall, there was no significant difference between the NE values of both kidneys in any of the treated pigs. Postinterventional MRI indicated absorption of ultrasound energy at the transverse process and fascia.

Conclusion

MRgHiFUS had some thermal periarterial effects but failed to induce renal denervation. Insufficient energy deposition is most likely attributable to a small acoustic window with beam path impediment in the porcine model. Since HiFUS treatment in humans is expected to be easier to perform due to better access to renal sympathetic nerves, further studies of this method are desirable to investigate the potential of MRgHiFUS as an alternative for patients not suitable for catheter-based renal sympathicolysis.

Novel treatment approaches in hypertensive type 2 diabetic patients

Type 2 diabetes mellitus (T2DM) and hypertension represent two common conditions worldwide. Their frequent association with cardiovascular diseases makes management of hypertensive patients with T2DM an important clinical priority. Carvedilol and renal denervation are two promising choices to reduce plasma glucose levels and blood pressure in hypertensive patients with T2DM to reduce future complications and improve clinical outcomes and prognosis. Pathophysiological mechanisms of both options are under investigation, but one of the most accepted is an attenuation in sympathetic nervous system activity which lowers blood pressure and improves insulin sensitivity. Choice of these therapeutic approaches should be individualized based on specific characteristics of each patient. Further investigations are needed to determine when to consider their use in clinical practice.

Resistant hypertension: is renal denervation the current treatment of choice?

BACKGROUND

Resistant hypertension is simply defined as failure to control blood pressure <140/90 mmHg in an adherent non-diabetic patient with normal kidney function despite the use of optimal doses of three antihypertensive agents, including a diuretic. Also, control of blood pressure in any adherent patient with more than four antihypertensive agents defines resistant hypertension. In a patient with diabetes or chronic kidney disease, the goal blood pressure is <130/80 mmHg. One of the most important pathophysiological mechanisms of resistant hypertension is overactivity of the sympathetic nervous system (SNS). In selected patients with resistant hypertension, renal denervation has been shown to control blood pressure by suppressing SNS overactivity.

SUMMARY

This review summarizes the results of the studies of renal denervation for resistant hypertension and suggests the use of this procedure in several other conditions that are associated with SNS overactivity.

KEY MESSAGE

Renal denervation seems to control blood pressure in patients with resistant hypertension.

Renal denervation in the treatment of hypertension

Despite advances in nonpharmacologic and pharmacologic therapy, blood pressure control rates in hypertension are low. About 10 % of patients with hypertension fulfill the criteria of therapy resistance, which is defined as noncontrolled blood pressure despite treatment with ≥3 antihypertensive drugs of different classes, including a diuretic, at optimal or maximal tolerated doses. Although the pathogenesis of resistant hypertension is multifactorial, an interaction between renal afferent and efferent sympathetic nerves and the central nervous system plays a key role, leading to increased renal and central sympathetic activity. Catheter-based renal sympathetic denervation (RDN) is a novel therapeutic technique for the treatment of resistant hypertension. Clinical trials of RDN have shown a significant and sustained reduction of blood pressure as well as renal and central sympathetic activity. In clinical practice, appropriate patient selection is crucial to ensure successful and safe treatment. Beyond hypertension, RDN was associated with reduction of heart rate, regression of left ventricular mass, and improvements in glucose metabolism and severity of sleep apnea. Further studies addressing open questions in the treatment of resistant hypertension and evaluating potential new indications such as metabolic syndrome or heart failure (RE-ADAPT-HF) are necessary to prove effectiveness and safety of RDN in these patients. By modulating sympathetic activity, RDN has the potential to provide benefit in a variety of diseases, but these concepts have to be evaluated in well-designed prospective controlled clinical trials.

Renal denervation in treatment-resistant hypertension: the need for restraint and more and better evidence

The Symplicity studies suggest that intravascular renal sympathetic nervous denervation improves blood pressure in patients with resistant hypertension, thus potentially opening a market for devices to be used when conventional drug therapy fails to restore blood pressure control. However, the size and durability of the antihypertensive, renal and sympatholytic effects of renal denervation, the long-term safety, improvement of quality of life, the possibility to relax antihypertensive drug treatment, the cost-effectiveness, and long-term hard cardiovascular-renal outcomes still remain to be firmly established. Most ongoing studies are small, industry-driven and purely observational with objectives to test new catheters and source of energy for renal nerve ablation or to search for ancillary benefits and new indications of the technique. The most urgent need, that is adequately powered randomized clinical trials testing renal denervation versus usual medical therapy delivered according to the state-of-the-art are under-represented and seldom funded by industry. The authors make a plea for a coordinated research effort in Europe. With this objective, they established collaboration with leading European experts and started the European Network for Coordinating Research on Renal Denervation. In the meantime, renal denervation should remain the ultima ratio in adherent and truly resistant patients with severe hypertension, confirmed by ambulatory monitoring, in whom secondary hypertension has been excluded and in whom all other efforts to reduce blood pressure have failed.

Renal denervation for treating resistant hypertension: current evidence and future insights from a global perspective

Adequate blood pressure control represents an important goal for all physicians due to the complications of hypertension which reduce patients' quality of life. A new interventional strategy to reduce blood pressure has been developed for patients with resistant hypertension. Catheter-based renal denervation has demonstrated excellent results in recent investigations associated with few side effects. With the growing diffusion of this technique worldwide, some medical societies have published consensus statements to guide physicians how to best apply this procedure. Questions remain to be answered such as the long-term durability of renal denervation, the efficacy in patients with other sympathetically mediated diseases, and whether renal denervation would benefit patients with stage 1 hypertension.

[Endovascular renal nerve ablation as a treatment for resistant hypertension]

Radiofrequency-induced renal ablation is a non-pharmacologic therapeutic approach for the treatment of essential resistant hypertension, with a stable blood pressure lowering effect. However, data from published studies cannot conclude yet on the long-term efficacy and safety of the procedure. Therefore, the various techniques of renal nerve ablation (radiofrequency, cryoablation, ultrasounds) need further evaluation in clinical research trials. According to recent national and international recommendations, renal ablation should be reserved for patients with essential resistant hypertension.

Blood pressure changes after renal denervation at 10 European expert centers

We did a subject-level meta-analysis of the changes (Δ) in blood pressure (BP) observed 3 and 6 months after renal denervation (RDN) at 10 European centers. Recruited patients (n=109; 46.8% women; mean age 58.2 years) had essential hypertension confirmed by ambulatory BP. From baseline to 6 months, treatment score declined slightly from 4.7 to 4.4 drugs per day. Systolic/diastolic BP fell by 17.6/7.1 mm Hg for office BP, and by 5.9/3.5, 6.2/3.4, and 4.4/2.5 mm Hg for 24-h, daytime and nighttime BP (P⩽0.03 for all). In 47 patients with 3- and 6-month ambulatory measurements, systolic BP did not change between these two time points (P⩾0.08). Normalization was a systolic BP of <140 mm Hg on office measurement or <130 mm Hg on 24-h monitoring and improvement was a fall of ⩾10 mm Hg, irrespective of measurement technique. For office BP, at 6 months, normalization, improvement or no decrease occurred in 22.9, 59.6 and 22.9% of patients, respectively; for 24-h BP, these proportions were 14.7, 31.2 and 34.9%, respectively. Higher baseline BP predicted greater BP fall at follow-up; higher baseline serum creatinine was associated with lower probability of improvement of 24-h BP (odds ratio for 20-μmol l⁻¹ increase, 0.60; P=0.05) and higher probability of experiencing no BP decrease (OR, 1.66; P=0.01). In conclusion, BP responses to RDN include regression-to-the-mean and remain to be consolidated in randomized trials based on ambulatory BP monitoring. For now, RDN should remain the last resort in patients in whom all other ways to control BP failed, and it must be cautiously used in patients with renal impairment.

Renal sympathetic denervation: applications in hypertension and beyond

Renal afferent and efferent sympathetic nerves are involved in the regulation of blood pressure and have a pathophysiological role in hypertension. Renal sympathetic denervation is a novel therapeutic technique for the treatment of patients with resistant hypertension. Clinical trials of renal sympathetic denervation have shown significant reductions in blood pressure in these patients. Renal sympathetic denervation also reduces heart rate, which is a surrogate marker of cardiovascular risk. Conditions that are comorbid with hypertension, such as heart failure and myocardial hypertrophy, obstructive sleep apnoea, atrial fibrillation, renal dysfunction, and metabolic syndrome are closely associated with enhanced sympathetic activity. In experimental models and case-control studies, renal denervation has had beneficial effects on these conditions. Renal denervation could become a commonly used procedure to treat resistant hypertension and chronic diseases associated with enhanced sympathetic activation. Current work is focused on refining the techniques and interventional devices to provide safe and effective renal sympathetic denervation. Controlled studies in patients with mild-to-moderate, nonresistant hypertension and comorbid conditions such as heart failure, diabetes mellitus, sleep apnoea, and arrhythmias are needed to investigate the capability of renal sympathetic denervation to improve cardiovascular outcomes.

Renal sympathetic denervation for treatment of resistant hypertension: a systematic review

Catheter-based renal sympathetic denervation (RSD) is a novel technique that is being investigated as treatment for resistant hypertension. To systematically evaluate the existing literature on the safety and efficacy of RSD in persons with resistant hypertension, online searches of Medline and the Cochrane Library Database (up to June 2012) were performed. Randomized controlled trials, observational studies, and conference proceedings published in English language were included. Nineteen studies (N=683 persons) were included. Follow-up duration ranged from 1 to 24 months. All studies reported significant reductions in systolic and diastolic pressures. Maximal reduction of blood pressure ranged from 18 mm Hg to 36 mm Hg (systolic) and 9 mm Hg to 15 mm Hg (diastolic). Sustained benefit of blood pressure reduction at 12 months was seen in 5 studies. No worsening of renal function was reported and there were few procedure-related adverse events such as pseudoaneurysm formation, hypotension, and bradycardia. Data from short-term studies suggest that RSD is a safe and effective therapeutic option in carefully selected patients with resistant hypertension. Long-term studies with large patient populations are needed to study whether this benefit is sustained with a demonstrable difference in cardiovascular disease event rates.

Renal denervation for treatment-resistant hypertension

Hypertension is a major public health concern that is increasing in prevalence. Lifestyle and pharmacological management are not always sufficient to control blood pressure and treatment-resistant hypertension is a recognized clinical challenge. Renal sympathetic denervation (RSD) represents a new frontier in the treatment of resistant hypertension.

RESULTS

from the Symplicity HTN-1 and HTN-2 trials have demonstrated evidence that suggests RSD can safely reduce blood pressure in patients with this condition. More research is needed to verify these data, clarify unanswered questions and assess future applications of RSD. This review provides a detailed overview on the history of hypertension, treatment-resistant hypertension, the rationale behind RSD, current evidence and potential future applications of RSD. An overview of current and upcoming RSD devices is also included.

[Frequency of hypertension resistant to treatment and indication for renal denervation]

OBJECTIVE

To evaluate in hypertensive patients followed in a specialized hypertension unit, the prevalence of subjects uncontrolled despite triple therapy including a diuretic. The aim is to estimate the percentage of hypertensive patients with an indication to renal denervation.

METHOD

From a database of computerized medical records of a unit specialized in hypertension, it was extracted 144 consecutive cases of subjects treated and followed for at least 1year and having had a home pressure monitoring (HPM) on treatment, and if necessary a work-up for a secondary hypertension. The blood pressure (BP) was evaluated in office by automated method (after 2 and 8minutes) and with HPM (average of three measurements in the morning and evening for three consecutive days).

RESULTS

The population has the following characteristics: age 62 with 26% over 70years, treated dyslipidemia (39%), treated diabetes (11%), adrenal hypertension treated medically (14%), severe renal failure (3%). The means of treatment are: a monotherapy (33%), bitherapy (35%), triple therapy (17%), quadritherapy (7%), pentatherapy or more (1%), spironolactone (45%), thiazide diuretics (49%). The uncontrolled hypertension was observed in 26% if the BP is evaluated with HPM, in 52% if the BP is evaluated at the office after 2minutes of rest and 7% if the BP is evaluated after 8minutes of rest (P<0.01). In patients treated with at least a tritherapy in association with a diuretic, an uncontrolled hypertension was observed in 5% if the BP is evaluated with HPM. Failure to control for the SBP is the cause of 80% of resistant hypertension.

CONCLUSION

The frequency of resistant hypertension is 5% of hypertensive patients followed in a specialized hypertension unit when guidelines are applied in the case of uncontrolled hypertension. These results indicate that the indication for renal denervation affects only a small percentage of patients treated for hypertension.