Catheter-based renal denervation for resistant hypertension: rationale and design of the SYMPLICITY HTN-3 Trial

Renal sympathetic denervation: hypertension therapy and beyond

Hypertension is one of the most important treatable causes of mortality and morbidity in the world, but despite the wide availability of pharamacological therapy, blood pressure is poorly controlled in many patients. Renal sympathetic denervation (RSD) is a novel therapeutic option whereby the renal sympathetic nerves, which lie within and around the wall of the renal arteries, are ablated using a catheter placed within the arterial lumen. The Symplicity HTN-2 trial has shown that RSD reduces blood pressure to a clinically relevant degree; this finding has resulted in an explosion in interest in the procedure and RSD has the potential to become a standard therapy for many hypertensive patients. Many new devices are in development that will simplify the procedure, and several novel indications for RSD are currently being investigated in clinical trials.

Catheter-based renal denervation for treatment of resistant hypertension

Hypertension is a common disease associated with important cardiovascular complications. Persistent blood pressure of 140/90 or higher despite combined use of a reninangiotensin system blocker, calcium channel blocker and a diuretic at highest tolerated doses constitutes resistant hypertension. Excess sympathetic activity plays an important pathogenic role in resistant hypertension in addition to contributing to the development of metabolic problems, in particular diabetes. Reduction of renal sympathetic activity by percutaneous catheter-based radiofrequency ablation via the renal arteries has been shown in several studies to decrease blood pressure in patients with resistant hypertension, and importantly is largely free of significant complications. However, longer term follow-up is required to confirm both long-term safety and efficacy.

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

OBJECTIVES

This study sought to determine the current effectiveness and safety of sympathetic renal denervation (RDN) for resistant hypertension.

BACKGROUND

RDN is a novel approach that has been evaluated in multiple small studies.

METHODS

We performed a systematic review and meta-analysis of published studies evaluating the effect of RDN in patients with resistant hypertension. Studies were stratified according to controlled versus uncontrolled design and analyzed using random-effects meta-analysis models.

RESULTS

We identified 2 randomized controlled trials, 1 observational study with a control group, and 9 observational studies without a control group. In controlled studies, there was a reduction in mean systolic and diastolic blood pressure (BP) at 6 months of -28.9 mm Hg (95% confidence interval [CI]: -37.2 to -20.6 mm Hg) and -11.0 mm Hg (95% CI: -16.4 to -5.7 mm Hg), respectively, compared with medically treated patients (for both, p < 0.0001). In uncontrolled studies, there was a reduction in mean systolic and diastolic BP at 6 months of -25.0 mm Hg (95% CI: -29.9 to -20.1 mm Hg) and -10.0 mm Hg (95% CI: -12.5 to -7.5 mm Hg), respectively, compared with pre-RDN values (for both, p < 0.00001). There was no difference in the effect of RDN according to the 5 catheters employed. Reported procedural complications included 1 renal artery dissection and 4 femoral pseudoaneurysms.

CONCLUSIONS

RDN resulted in a substantial reduction in mean BP at 6 months in patients with resistant hypertension. The decrease in BP was similar irrespective of study design and type of catheter employed. Large randomized controlled trials with long-term follow-up are needed to confirm the sustained efficacy and safety of RDN.

Renal sympathetic denervation in resistant hypertension

Resistant hypertension remains a major clinical problem despite the available multidrug therapy. Over the next decades, its incidence will likely increase given that it is strongly associated with older age and obesity. Resistant hypertension patients have an increased cardiovascular risk, thus effective antihypertensive treatment will provide substantial health benefits. The crosstalk between sympathetic nervous system and kidneys plays a crucial role in hypertension. It influences several pathophysiological mechanisms such as the central sympathetic tone, the sodium balance and the systemic neurohumoral activation. In fact, studies using several animal models demonstrated that the renal denervation prevented and attenuated hypertension in multiple species. Large reductions in blood pressure were also observed in malignant hypertension patients submitted to sympathectomy surgeries. However, these approaches had an unacceptably high rates of periprocedural complications and disabling adverse events. Recently, an innovative non-pharmacological therapy that modulates sympathetic activation has been successfully developed. Renal sympathetic percutaneous denervation is an endovascular procedure that uses radiofrequency energy to destroy the autonomic renal nerves running inside the adventitia of renal arteries. This method represents a promising new approach to the strategy of inhibiting the sympathetic nervous system. The aim of this review is to examine the background knowledge that resulted in the development of this hypertension treatment and to critically appraise the available clinical evidence.

Renal sympathetic denervation for treatment of drug-resistant hypertension: one-year results from the Symplicity HTN-2 randomized, controlled trial

BACKGROUND

Renal sympathetic nerve activation contributes to the pathogenesis of hypertension. Symplicity HTN-2, a multicenter, randomized trial, demonstrated that catheter-based renal denervation produced significant blood pressure lowering in treatment-resistant patients at 6 months after the procedure compared with control, medication-only patients. Longer-term follow-up, including 6-month crossover results, is now presented.

METHODS AND RESULTS

Eligible patients were on ≥3 antihypertensive drugs and had a baseline systolic blood pressure ≥160 mm Hg (≥150 mm Hg for type 2 diabetics). After the 6-month primary end point was met, renal denervation in control patients was permitted. One-year results on patients randomized to immediate renal denervation (n=47) and 6-month postprocedure results for crossover patients are presented. At 12 months after the procedure, the mean fall in office systolic blood pressure in the initial renal denervation group (-28.1 mm Hg; 95% confidence interval, -35.4 to -20.7; P<0.001) was similar to the 6-month fall (-31.7 mm Hg; 95% confidence interval, -38.3 to -25.0; P=0.16 versus 6-month change). The mean systolic blood pressure of the crossover group 6 months after the procedure was significantly lowered (from 190.0±19.6 to 166.3±24.7 mm Hg; change, -23.7±27.5; P<0.001). In the crossover group, there was 1 renal artery dissection during guide catheter insertion, before denervation, corrected by renal artery stenting, and 1 hypotensive episode, which resolved with medication adjustment.

CONCLUSIONS

Control patients who crossed over to renal denervation with the Symplicity system had a significant drop in blood pressure similar to that observed in patients receiving immediate denervation. Renal denervation provides safe and sustained reduction of blood pressure to 1 year.

Renal denervation in cardiometabolic disease: concepts, achievements and perspectives

AIMS

Growing evidence suggests that renal denervation may reduce elevated blood pressure values in resistant hypertension. More recently a number of studies have assessed the effects of the intervention on the dysmetabolic disarray (i.e. insulin resistance, glucose intolerance, and diabetes mellitus) frequently detectable in resistant hypertensive patients. The present viewpoint article critically examines the results obtained so far in this area.

DATA SYNTHESIS

The results of the studies performed so far provide evidence that ablation of efferent and afferent sympathetic renal nerves improves glucose metabolism, reducing the incidence of glucose intolerance, fasting hyperglycemia and diabetic state in resistant hypertensive patients. The results, however, cannot be regarded as conclusive, taking into account that limitations in the experimental design of the studies published so far, as well as the frequent lack of specific subgroups data analysis, prevent to draw conclusive information on this issue.

CONCLUSIONS

Although promising, the favorable results of renal denervation on the metabolic disarray frequently detectable in resistant hypertension require to be confirmed in large scale, randomized studies which are currently ongoing.

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.

Resistant hypertension: a frequent and ominous finding among hypertensive patients with atherothrombosis

AIMS

The effect of resistant hypertension on outcomes in patients with atherothrombotic disease is currently unknown. Accordingly, we sought to determine the prevalence and outcomes of resistant hypertension in stable hypertensive outpatients with subclinical or established atherothombotic disease enrolled in the international Reduction of Atherothrombosis for Continued Health (REACH) registry.

METHODS AND RESULTS

Resistant hypertension was defined as a blood pressure ≥140/90 mmHg at baseline (≥130/80 mmHg if diabetes/renal insufficiency) with the use of ≥3 antihypertensive medications, including a diuretic. The primary outcome was a composite of cardiovascular death, myocardial infarction, or stroke at 4 years. A total of 53 530 hypertensive patients were included. The prevalence of resistant hypertension was 12.7%; 6.2% on 3 antihypertensive agents, 4.6% on 4 agents, and 1.9% on ≥5 agents (mean: 4.7 ± 0.8). In addition to a diuretic, these patients were being treated mostly with ACE-inhibitors/angiotensin receptor blockers (90.1%), beta-blockers (67.0%), and calcium channel blockers (50.8%). Patients with resistant hypertension had a higher risk of the primary endpoint on multivariable analysis [hazard ratio (HR) 1.11, 95% confidence interval (CI) 1.02-1.20; P = 0.017], including an increased non-fatal stroke risk (HR: 1.26; 95% CI: 1.10-1.45; P = 0.0008). Hospitalizations due to congestive heart failure were higher (P < 0.0001). Patients on ≥5 agents had a higher adjusted risk for the primary endpoint when compared with those on ≤3 agents (P = 0.03).

CONCLUSION

The presence of resistant hypertension identifies a subgroup of patients with hypertension and atherothrombosis who are at heightened risk for adverse long-term outcomes.

Renal denervation: a potential new treatment for severe hypertension

Hypertension is a leading cause of cardiovascular morbidity and mortality. Drug-resistant hypertension remains common despite the availability of several classes of effective antihypertensive agents. Sympathetic hyperactivity has long been recognized as a major contributor to resistant hypertension, but radical sympathectomy was abandoned several decades ago due to its significant side effects. The newly developed, minimally invasive, catheter-based renal sympathetic denervation procedure has been shown in recent trials to produce impressive blood pressure reductions and a favorable safety profile in drug-resistant hypertension. Although the long-term efficacy and safety of renal denervation remains to be determined, emerging data suggest that the benefits of renal denervation may extend beyond blood pressure control.

Current status of renal denervation in resistant hypertension

Resistant hypertension is a frequent form of arterial hypertension that, with the exception of malignant hypertension, constitutes the most dangerous stage of arterial hypertension. Recently we have improved the detection, diagnosis, and therapy of resistant hypertensives. The technique of renal denervation with a catheter has improved the control of blood pressure in such patients. The technique is simple, safe, and available data indicates that it is effective. More data and longer follow-up of patients are required to promote wide acceptance of this new technique.

[Treatment resistant hypertension. Value of a new treatment concept]

Sympathetic overexpression can be found in a majority of hypertensive patients. Resistant arterial hypertension requires a targeted diagnostic procedure in order to exclude secondary causes of hypertension which can be treated specifically with established therapies. If secondary reasons are not identified, the antihypertensive medication is already optimal and lifestyle changes have been realized, but still the goal of antihypertensive therapy cannot be achieved, alternative invasive therapy strategies such as renal sympathetic denervation and baroreflex activation have been developed to achieve blood pressure control. These therapies are restricted to specialized centers which treat well-defined patients with therapy-resistant hypertension. Little long-term data concerning safety and efficacy are available for the two strategies. However, they should preferably be used as an ultima-ratio and add-on pathway to conservative procedures when established medication fails to achieve blood pressure control. To date, the effectiveness of the interventional antihypertensive therapies has only been shown on patients with systolic blood pressure over 160 mmHg and a mean oral medication of five drugs.

Renal denervation therapies for refractory hypertension

The treatment of severe hypertension by the surgical obliteration of the renal sympathetic nerves was proposed almost 80 years ago. This approach, although highly effective in reducing blood pressure was associated with a significant amount of side effects and it was rapidly replaced by better tolerated medical therapy. The rapid progress in catheter based technologies occurring within the last 20 years facilitated the development of the first radio frequency renal artery denervation catheter. At the present time, several small trials have demonstrated the safety and efficacy of this approach among patients with refractory hypertension. Besides its effect on reducing blood pressure, other pleiotropic effects (ie, improving glycemia in diabetic patients) have been proposed. In this review, we discuss the anatomical and physiological rationale for this therapy, provide an update on the latest clinical data available and describe additional emerging technologies in this field.