[Expert consensus statement on interventional renal sympathetic denervation for hypertension treatment]

[Therapy-resistant hypertension]

BACKGROUND

Therapy-resistant hypertension is commonly encountered in daily practice. It is present when the therapeutic goal is not achieved after trying at least three antihypertensives from different groups with adequate doses and including a diuretic. Between 10 and 20% of patients are affected and their prognosis is poor. Thus, intensive strategies are required to achieve normotension.

DIAGNOSIS

An exact diagnosis is essential. Pseudoresistance needs to be excluded in addition to secondary hypertension and sleep apnea syndrome. The most common cause of pseudoresistance is incorrect blood pressure measurement, false estimation of the real blood pressure level, lack of compliance, unhealthy lifestyle, and drug interactions. Therapeutic resistance should not be diagnosed without 24 h ambulatory blood pressure measurement. This significantly reduces the total number of "resistant" patients.

THERAPY

Successful control of blood pressure is achieved in the majority of patients by taking advantage of all possible therapy options. Treatment with 4-6 antihypertensive drugs is justified because of the improvement of cardiovascular prognosis. However, prerequisite is the absence of undesirable side effects which is the most important condition for adequate and reliable patient compliance. Only in the case of failure of the above therapy options can invasive procedures--renal denervation and baroreflex activation therapy--be applied as they are still experimental. Successful management of patients with resistant hypertension is only possible with intensive and time-consuming physician-patient relationships.

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.

Association of vitamin D status and blood pressure response after renal denervation

BACKGROUND

Vitamin D deficiency is associated with hypertension; however, it is unclear whether vitamin D influences therapeutic blood pressure reduction. Renal sympathetic denervation (RDN) reduces blood pressure in resistant hypertension. We hypothesized that vitamin D might influence blood pressure response to RDN.

METHODS

Vitamin D was measured in 101 patients with resistant hypertension undergoing RDN. The associations between vitamin D status and systolic blood pressure (SBP) reduction 6 months after RDN were analyzed.

RESULTS

Mean office SBP at baseline was 171.5 ± 2 mmHg. After RDN, mean office SBP was reduced by 28.4 ± 2.3 mmHg (p = 0.007). 85 patients (84.2 %) had SBP reductions >10 mmHg (responders). Vitamin D concentrations were lower in non-responders as compared to responders (9.9 ± 4.5 vs. 13.7 ± 7.4 ng/ml, p = 0.008). Non-responders (n = 16, 15.8 %), more often had a vitamin D concentration below the median as compared to responders (81 vs. 46 %, p = 0.013). The percentage of patients with normal vitamin D concentrations increased with increasing tertiles of SBP reduction (p for trend = 0.020). In patients with vitamin D concentrations below the median, SBP reduction was lower as compared to patients with a vitamin D concentration above the median (23.5 ± 3.2 vs. 33.7 ± 3.2 mmHg, p = 0.026). Baseline vitamin D concentrations correlated with SBP reduction (r = 0.202, p = 0.043).

CONCLUSIONS

In patients with resistant hypertension, low vitamin D concentrations were associated with a decreased SBP response and a higher rate of non-response.

Treating resistant hypertension: role of renal denervation

Arterial hypertension is the most prevalent risk factor associated with increased cardiovascular morbidity and mortality. Although pharmacological treatment is generally well tolerated, 5%–20% of patients with hypertension are resistant to medical therapy, which is defined as blood pressure above goal (>140/90 mmHg in general; >130–139/80–85 mmHg in patients with diabetes mellitus; >130/80 mmHg in patients with chronic kidney disease) despite treatment with ≥3 antihypertensive drugs of different classes, including a diuretic, at optimal doses. These patients are at significantly higher risk for cardiovascular events, in particular stroke, myocardial infarction, and heart failure, as compared with patients with nonresistant hypertension. The etiology of resistant hypertension is multifactorial and a number of risk factors have been identified. In addition, resistant hypertension might be due to secondary causes such as primary aldosteronism, chronic kidney disease, renal artery stenosis, or obstructive sleep apnea. To identify patients with resistant hypertension, the following must be excluded: pseudo-resistance, which might be due to nonadherence to medical treatment; white-coat effect; and inaccurate measurement technique. Activation of the sympathetic nervous system contributes to the development and maintenance of hypertension by increasing renal renin release, decreasing renal blood flow, and enhancing tubular sodium retention. Catheter-based renal denervation (RDN) is a novel technique specifically targeting renal sympathetic nerves. Clinical trials have demonstrated that RDN significantly reduces blood pressure in patients with resistant hypertension. Experimental studies and small clinical studies indicate that RDN might also have beneficial effects in other diseases and comorbidities, characterized by increased sympathetic activity, such as left ventricular hypertrophy, heart failure, metabolic syndrome and hyperinsulinemia, atrial fibrillation, obstructive sleep apnea, and chronic kidney disease. Further controlled studies are required to investigate the role of RDN beyond blood pressure control.

Renal sympathetic denervation as antihypertensive therapy--a reappraisal of first results

Renal sympathetic denervation (RSD) has previously been discussed in this journal. Since then, it has become a common procedure in many countries to use RSD to treat patients with putatively resistant hypertension. In Germany alone, RSD is now routinely used to treat resistant hypertension at the expense of the health-care system. The Germans have established a national registry to systematically and continuously follow up hypertensive patients who have undergone RSD. However, there are concerns because the registry is voluntary and physicians practicing the procedure may not have the accrual of new knowledge regarding the utility of RSD as their primary professional aim. Since the previous editorial on renal denervation, new results have been published. Therefore, it is appropriate to re-evaluate RSD.

[Heart and kidneys. Renal denervation as therapy for hypertension]

Arterial hypertension is a major cardiovascular risk factor with a high prevalence in western industrial countries and the proportion of patients with blood pressure at target values remains low. Patients with therapy-resistant hypertension, defined as failure to achieve target blood pressure despite a triple antihypertensive drug regimen including a diuretic, are at very high risk which supports the need for greater efforts towards improving hypertension outcomes in this population. Secondary causes of hypertension are often found in patients with resistant hypertension. Activation of the sympathetic nervous system has been identified as a main contributor to the development and progression of high blood pressure. Catheter-based renal denervation offers a new interventional treatment option resulting in a significant long-term reduction in blood pressure (> 36 months) and increased blood pressure control (up to 40% of the treated population). The basis for successful treatment is an appropriate patient selection, including life-style modification, exclusion of pseudoresistance, termination of substances increasing blood pressure and an optimized drug treatment. Further clinical studies are warranted and ongoing to determine the role of renal denervation in antihypertensive treatment.

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.

Ambulatory blood pressure changes after renal sympathetic denervation in patients with resistant hypertension

BACKGROUND

Catheter-based renal sympathetic denervation (RDN) reduces office blood pressure (BP) in patients with resistant hypertension according to office BP. Less is known about the effect of RDN on 24-hour BP measured by ambulatory BP monitoring and correlates of response in individuals with true or pseudoresistant hypertension.

METHODS AND RESULTS

A total of 346 uncontrolled hypertensive patients, separated according to daytime ambulatory BP monitoring into 303 with true resistant (office systolic BP [SBP] 172.2±22 mm Hg; 24-hour SBP 154±16.2 mm Hg) and 43 with pseudoresistant hypertension (office SBP 161.2±20.3 mm Hg; 24-hour SBP 121.1±19.6 mm Hg), from 10 centers were studied. At 3, 6, and 12 months follow-up, office SBP was reduced by 21.5/23.7/27.3 mm Hg, office diastolic BP by 8.9/9.5/11.7 mm Hg, and pulse pressure by 13.4/14.2/14.9 mm Hg (n=245/236/90; P for all <0.001), respectively. In patients with true treatment resistance there was a significant reduction with RDN in 24-hour SBP (-10.1/-10.2/-11.7 mm Hg, P<0.001), diastolic BP (-4.8/-4.9/-7.4 mm Hg, P<0.001), maximum SBP (-11.7/-10.0/-6.1 mm Hg, P<0.001) and minimum SBP (-6.0/-9.4/-13.1 mm Hg, P<0.001) at 3, 6, and 12 months, respectively. There was no effect on ambulatory BP monitoring in pseudoresistant patients, whereas office BP was reduced to a similar extent. RDN was equally effective in reducing BP in different subgroups of patients. Office SBP at baseline was the only independent correlate of BP response.

CONCLUSIONS

RDN reduced office BP and improved relevant aspects of ambulatory BP monitoring, commonly linked to high cardiovascular risk, in patients with true-treatment resistant hypertension, whereas it only affected office BP in pseudoresistant hypertension.

[Renal denervation. Current developments]

METHODICAL INNOVATION: Renal denervation is a catheter-based, endovascular procedure for the treatment of drug-resistant hypertension. The aim of the therapy is to lower the blood pressure < 140/90 mmHg.

PERFORMANCE

Even after successful minimally invasive therapy patients usually continue to take three or more antihypertensive drugs. Currently there is no evidence that renal denervation is a good option for the treatment of well-controlled hypertension in order to dispense with antihypertensive drugs. In carefully selected patients the mean reduction in systolic and diastolic blood pressure after renal denervation is 25-30 mmHg and 10-15 mmHg, respectively.

ACHIEVEMENTS

Procedure-related or device-related complications are rare. Ablation catheters from different manufactures differ greatly in handling properties; however, up to now there is no evidence for relevant differences in safety and efficacy between the devices available.

[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.

[Non-pharmacological and pharmacological treatment of arterial hypertension: current situation]

A permanent and successful treatment of high blood pressure is based on a combination of non-pharmacological treatment measures and pharmacological therapy. The most proven non-pharmacological measures are physical and sports activities, weight reduction, dietary adaption and reduction of salt intake as well as nicotine abstinence and moderate alcohol consumption. A blood pressure reducing effect of evidence grade A was demonstrated for these 4 pillars of non-pharmacological therapy in studies. For pharmacological treatment five main substance groups are available: thiazide diuretics, ACE inhibitors, AT1 blockers, calcium channel blockers and beta blockers. A very good blood pressure reducing effect with an advantageous side effect profile has been proven for all substances. The initial high blood pressure therapy can be carried out with monotherapy but therapy with several antihypertensives is often necessary for the very varied combination of compounds which are available in a meaningful combination and dosage of effective ingredients. For the treatment of comorbid hypertensive patients recommendations are available for an individualized pharmacological treatment corresponding to the specific cardiovascular risk and comorbidity. High blood pressure therapy must be continuously carried out over many years. For permanent success of the therapy good compliance is indispensible which can be encouraged by integration in the therapy and should be regularly controlled.

[Renal denervation: current state and future perspectives]

Hypertension is a well-known risk factor for major cardiovascular events. Despite advances in medical therapy, sufficient treatment of hypertension remains unsatisfying in a substantial number of patients and is therefore one of the main challenges in modern medicine. In Germany 5-15 % of patients with hypertension suffer from resistant hypertension with elevated blood pressure despite the use of at least three antihypertensive drugs. Additionally patients often suffer from side effects. In patients with resistant hypertension the important role of the sympathetic nervous system with increased sympathetic activity is well known. In the past surgical sympathectomy with extended removal of sympathetic ganglia was performed to reduce blood pressure in patients with malignant hypertension. The positive effect of this highly invasive procedure on blood pressure led to the development of new strategies for the treatment of uncontrolled hypertension. One of the novel procedures includes catheter-based renal sympathetic denervation. The most common system is the radiofrequency ablation catheter (Symplicity®, Medtronic, Minneapolis, USA) which ablates the nerve fibers in the adventitia of the renal arteries by using high-frequency energy. As the results of the Symplicity trials (HTN-1 and HTN-2) showed significant reduction of systolic and diastolic blood pressure after renal denervation there is growing interest in this novel procedure. Moreover, by reducing the sympathetic activity after renal denervation early results indicate a positive impact on glucose metabolism, sleep apnea syndrome, as well as heart and renal failure. These effects led to the development of many different devices for renal denervation; however, trials with a higher number of patients and longer follow-up need to confirm these initially promising results and the value of newer devices. Until then renal denervation should not be regarded as standard therapy for arterial hypertension or an alternative to medical antihypertensive treatment and should be reserved for selected patients with resistant hypertension and specialized medical centres.