The biophysics of renal sympathetic denervation using radiofrequency energy

[Renal sympathetic denervation can significantly reduce blood pressure and improve arterial stiffness in hypertensive beagles]

OBJECTIVE

To investigate the effect of renal sympathetic denervation (RDN) on blood pressure and arterial stiffness in hypertensive beagles and explore the underlying mechanism.

METHODS

Sixteen beagles were randomly divided into RDN group (n=8, fed with a high-salt high-fat diet to establish models of hypertension and treated with RDN), sham-operated group (n=4, fed with a high-salt high-fat diet to induce hypertension but only examined with renal arteriography) and control group (n=4, fed with formula dog food). The changes in blood pressure, arterial stiffness, endothelial function, and sympathetic activity were compared among the 3 groups and correlation analysis was performed.

RESULTS

All the animal models of hypertension were established successfully in the beagles. At 3 months after the RDN, the changes in systolic blood pressure (SBP) differed significantly among the 3 groups (P=0.006), and the reduction in SBP was significantly greater in RDN group than in the other two groups (P < 0.05). The variations of diastolic blood pressure (DBP) also differed significantly among the 3 groups (P=0.016), and DBP reduction was more obvious in RDN group than in the control group (P=0.007), but similar to that in the sham-operated group (P=0.052). The changes of resistance index (RI) after the procedure were significantly different among the 3 groups (P=0.043), and the RDN group showed a greater reduction of RI than the control group (P=0.032) and sham group (P=0.043). Serum levels of eNOS, NO and Ang Ⅱ did not differ significantly among the groups either before or after RDN (P>0.05), but serum NE level was significantly higher in RDN group than in the control groupafter successful modeling (P=0.014), but similar to that in the sham group (P=0.560). Compared with the sham operation, RDN in the hypertensive beagles resulted in a significantly greater decrease of serum NE level (P=0.032) to almost the control level (P= 0.080). The changes of RI following RDN were significantly correlated with the changes of SBP, DBP and serum levels of NO and NE (P < 0.05).

CONCLUSION

RDN can significantly reduce blood pressure and improve arterial stiffness in hypertensive beagles possibly by reducing sympathetic activity and blood pressure and promoting NO synthesis.

Comparison of ablation characteristics of three different radiofrequency applicators in renal sympathetic denervation

OBJECTIVE

Renal sympathetic denervation (RDN) is an alternative treatment for resistant hypertension (RH). This study aims to compare ablation effects using three radiofrequency applicators (i.e., balloon-based four electrodes, spiral and monopolar devices).

METHODS

An idealized three-dimensional model of the renal artery was established using COMSOL Multiphysics to mimic radiofrequency ablation (RFA). Radiofrequency (RF) energy was delivered to the tissue at the same simulation settings, i.e., 4, 6, and 8 W for 60 s, using the three abovementioned RF applicators. The temperature distribution in the tissue was calculated using the coupled electrical-thermal-fluid finite element method. Lesion borders were defined using 50 °C isotherms. The maximum lesion depth, width, area, and circumferential coverage rate were compared among the three applicators at a blood flow of 0.4 m/s. Monopolar RF ablations in a renal artery phantom model were performed to validate the reliability of the simulation method.

RESULTS

The balloon-based system yields greater lesion depths and widths compared with spiral and monopolar denervation under the same power. The range of maximum lesion depth is 1.58-3.11 mm for balloon-based RDN, 0.90-1.81 mm for spiral RDN and 1.12-2.38 mm for monopolar RDN, at a power of 4-8 W. The corresponding ranges of maximum lesion width are 2.22-5.73, 1.48-3.54, and 1.93-5.31 mm, respectively, and the circumferential coverage rates of the renal artery are 41.43%-91.99%, 31.71%-66.23%, and 9.55%-23.06%, respectively. The average velocity after balloon-based, spiral, and monopolar RDN increases by 3, 5, and 1 cm/s, respectively. The validation of the computer model offered prediction errors are <5% in terms of temperature at different locations (i.e., 2, 4, and 8 mm).

CONCLUSIONS

In terms of lesion size, balloon-based RDN appears to be the best option for the treatment of RH. However, the change in flow velocity in the arterial flow field suggests that its hemodynamic changes must be prioritized for investigating its safety. Although spiral catheter ablation yields the smallest lesion size and a significant change in flow velocity in the flow field, its coverage rate is larger than that of monopolar RDN; compared with balloon-based RDN, it did not obstruct most of the blood flow.

Evaluating the thermal performance of a balloon-based renal sympathetic denervation system with array electrodes: a finite element study

Renal denervation transmits radiofrequency (RF) energy through an electrode to treat resistant hypertension (RH), applying ablation in the renal artery. Several experimental studies have shown that this treatment has been used effectively to treat RH. The aim of this paper is to investigate the effect of ablation parameters (i.e., electrode length, applied voltage, ablation time, and blood flow) on the temperature distribution using a balloon-based array electrodes system. A simplified three-dimensional model including four electrodes and a balloon was established. The balloon diameter was 3 mm and placed in a 5 mm diameter renal artery for forming intra-arterial occlusion. Four electrodes were mounted on the balloon and distributed in the same plane to mimic circumferential RF ablation. Computer simulations were conducted to investigate the thermal performances of the device by setting different electrode configurations, treatment protocols, and physiological factors. The thermal performances including the thermal distribution, maximum lesion depth, length, and area were analyzed. The lesion shape of the array RF electrodes was approximately a sphere with a 100% circumference coverage rate of the renal artery. The lesion depth and length increase with each factor except for blood velocity. Increasing the electrode length from 2 to 4 mm or 2 to 6 mm, the lesion depth increases by 1.15 mm and 0.54 mm at 60 s. The corresponding lesion length increases by 2.65 mm and 2.34 mm, respectively. The range of effective lesion depth is 1.90-4.90 mm, at a voltage of 15-30 V. But the peak temperature at the arterial outer wall exceeded 100 °C when the voltage is above 25 V. In tissue, the degree of thermal injury in the 2 mm area reached 100%, but in blood was not more than 5%. There was no significant difference at different flow conditions because the difference value in lesion depth was not exceeded 0.5 mm. The results showed that the balloon-based four electrodes system is expected to overcome the difficulty of incomplete ablation. In clinical application, 2 mm-electrode is recommended to avoid long wall damage as much as possible and control the voltage below 25 V. This treatment has little thermal injury on the blood, which means it may avoid coagulation formation. Moreover, the application of this device does not need to consider the difference in individual blood velocity.

Accurate Depth of Radiofrequency-Induced Lesions in Renal Sympathetic Denervation Based on a Fine Histological Sectioning Approach in a Porcine Model

Background—

Ablation lesion depth caused by radiofrequency-based renal denervation (RDN) was limited to <4 mm in previous animal studies, suggesting that radiofrequency-RDN cannot ablate a substantial percentage of renal sympathetic nerves. We aimed to define the true lesion depth achieved with radiofrequency-RDN using a fine sectioning method and to investigate biophysical parameters that could predict lesion depth.

Methods and Results—

Radiofrequency was delivered to 87 sites in 14 renal arteries from 9 farm pigs at various ablation settings: 2, 4, 6, and 9 W for 60 seconds and 6 W for 120 seconds. Electric impedance and electrode temperature were recorded during ablation. At 7 days, 2470 histological sections were obtained from the treated arteries. Maximum lesion depth increased at 2 to 6 W, peaking at 6.53 (95% confidence interval, 4.27–8.78) mm under the 6 W/60 s condition. It was not augmented by greater power (9 W) or longer duration (120 seconds). There were statistically significant tendencies at 6 and 9 W, with higher injury scores in the media, nerves, arterioles, and fat. Maximum lesion depth was positively correlated with impedance reduction and peak electrode temperature (Pearson correlation coefficients were 0.59 and 0.53, respectively).

Conclusions—

Lesion depth was 6.5 mm for radiofrequency-RDN at 6 W/60 s. The impedance reduction and peak electrode temperature during ablation were closely associated with lesion depth. Hence, these biophysical parameters could provide prompt feedback during radiofrequency-RDN procedures in the clinical setting.

Safety of catheter-based radiofrequency renal denervation on branch renal arteries in a porcine model

OBJECTIVES

We aimed to investigate the safety of radiofrequency (RF)-renal denervation (RDN) on branch renal arteries (RAs) in a porcine model.

BACKGROUND

The efficacy of RF-RDN was enhanced by treatment of the branch RA, in addition to the main RA. However, there are concerns regarding the safety of RF-RDN on branch RA because of their smaller diameter and proximity to the kidney.

METHODS

RF was delivered to 24 RA from 12 swine. A total of 8 RA from 4 swine were untreated. Treated RA were examined by angiography and histopathology at 7, 30, and 90 days. Serum creatinine concentration, biophysical parameters during RF delivery, and renal norepinephrine concentration were also assessed.

RESULTS

Angiography revealed minimal late lumen loss and diameter stenosis in the main and branch RA at any time point. There was no change in serum creatinine after RF-RDN. Histopathologically, no augmentation of medial damage or neointimal formation was found in branch RA compared with main RA. No or minimal damage to surrounding tissues including the kidneys, ureters, lymph nodes, and muscles was observed at any time point in both the main and branch RA. Equivalent electrode temperature in the main and branch RA was achieved by automatic adjustment of output power by the generator. The renal norepinephrine concentration was significantly lower in the treated group compared with the untreated group.

CONCLUSIONS

RF-RDN on branch RA was safe in a porcine model, with stenosis-free healing of treated arteries and negligible kidney damage at 7, 30, and 90 days.

Percutaneous renal artery denervation in patients with chronic systolic heart failure: A randomized controlled trial

BACKGROUND

Renal denervation (RDN) is as an effective treatment for heart failure (HF), but its effects on cardiac function of patients with HF are not well documented. Here, the aim was to investigate RDN's effect on patients with chronic systolic HF, by conducting a single-center, prospective, randomized, and controlled study.

METHODS

Sixty patients with chronic systolic HF were randomly assigned to the RDN or control groups, receiving percutaneous catheter-based RDN with radiofrequency ablation and drug treatment, respectively. All patients performed a 6-minute walk test, echocardiography, blood pressure measurement, and biochemical test, at both baseline and in a 6-month follow up.

RESULTS

Over 6-month follow up, patients in RDN group showed a decrease in N-terminal pro-B-type natriuretic peptide (440.1 ± 226.5 pg/mL vs. 790.8 ± 287.0 pg/mL, p < 0.001, Cohen's d = 1.14), an increase in left ventricular ejection fraction (39.1 ± 7.3% vs. 35.6 ± 3.3%, p = 0.017, Cohen's d = 0.61), improved New York Heart Association class assessment (p = 0.01, Cohen's d = 0.66), and decreased blood pressures (p < 0.001, Cohen's d = 0.91), without reporting hypotension and syncope amaurosis. No significant between-group difference was observed for glomerular filtration rate and heart rate.

CONCLUSIONS

Renal denervation which effectively and safely improves patient's cardiac function as well as exercise tolerance, could be considered as an effective treatment for chronic systolic HF.

Renal Nerve Stimulation as Procedural End Point for Renal Sympathetic Denervation

PURPOSE OF REVIEW

Renal sympathetic denervation (RDN) as treatment option for hypertension has a strong rationale; however, variable effects on blood pressure (BP) have been reported ranging from non-response to marked reductions in BP. The absence of a procedural end point for RDN is one of the potential factors associated with the variable response. Studies have suggested the use of renal nerve stimulation (RNS) to adequately address this issue. This review aims to provide an overview of the clinical and experimental data available regarding the effects of RNS in the setting of RDN.

RECENT FINDINGS

Animal studies have shown that high-frequency electrical stimulation of the sympathetic nerves in the adventitia of the renal arteries elicits an increase in BP and leads to an increased norepinephrine spillover as a marker of increased sympathetic activity and these effects of stimulation were attenuated or blunted after RDN. In a human feasibility study using RNS both before and after RDN, similar BP responses were observed. Moreover, in patients with resistant hypertension, RNS-induced changes in BP appeared to be correlated with 24-h BP response after RDN. These data suggest that RNS is a useful tool to identify renal sympathetic nerve fibers in patients with treatment-resistant hypertension undergoing RDN, and to predict the likely effectiveness of RDN treatments. In acute procedural settings both in animal and human models, RNS elicits increase in BP and HR before RDN and these effects are blunted after RDN. Up to now, there is preliminary evidence that the RNS-induced BP changes predict 24-h ABPM outcome at follow-up in patients with resistant hypertension. Of note, studies are small sized and results of large trials comparing conventional RDN to RNS-guided RDN are warranted.

The autonomic nervous system as a therapeutic target in heart failure: a scientific position statement from the Translational Research Committee of the Heart Failure Association of the European Society of Cardiology

Despite improvements in medical therapy and device-based treatment, heart failure (HF) continues to impose enormous burdens on patients and health care systems worldwide. Alterations in autonomic nervous system (ANS) activity contribute to cardiac disease progression, and the recent development of invasive techniques and electrical stimulation devices has opened new avenues for specific targeting of the sympathetic and parasympathetic branches of the ANS. The Heart Failure Association of the European Society of Cardiology recently organized an expert workshop which brought together clinicians, trialists and basic scientists to discuss the ANS as a therapeutic target in HF. The questions addressed were: (i) What are the abnormalities of ANS in HF patients? (ii) What methods are available to measure autonomic dysfunction? (iii) What therapeutic interventions are available to target the ANS in patients with HF, and what are their specific strengths and weaknesses? (iv) What have we learned from previous ANS trials? (v) How should we proceed in the future?

Renal vascular calcification and response to renal nerve denervation in resistant hypertension

Renal sympathetic nerve denervation (RDN) is accepted as a treatment option for patients with resistant hypertension. However, results on decline in ambulatory blood pressure (BP) measurement (ABPM) are conflicting. The high rate of nonresponders may be related to increased systemic vascular stiffness rather than sympathetic overdrive. A single center, prospective registry including 26 patients with treatment resistant hypertension who underwent RDN at the Isala Hospital in the Netherlands. Renal perivascular calcium scores were obtained from noncontrast computed tomography scans. Patients were divided into 3 groups based on their calcium scores (group I: low 0-50, group II: intermediate 50-1000, and group III: high >1000). The primary end point was change in 24-hour ABPM at 6 months follow-up post-RDN compared to baseline. Seven patients had low calcium scores (group I), 13 patients intermediate (group II), and 6 patients had high calcium scores (group III). The groups differed significantly at baseline in age and baseline diastolic 24-hour ABPM. At 6-month follow-up, no difference in 24-hour systolic ABPM response was observed between the 3 groups; a systolic ABPM decline of respectively -9 ± 12, -6 ± 12, -12 ± 10 mm Hg was found. Also the decline in diastolic ambulatory and office systolic and diastolic BP was not significantly different between the 3 groups at follow-up. Our preliminary data showed that the extent of renal perivascular calcification is not associated with the ABPM response to RDN in patients with resistant hypertension.

What we need to know about renal nerve ablation for treatment of hypertension and other states of sympathetic overactivity

Renal nerves are key players in the regulation of kidney function and blood pressure control. Targeting the neurogenic mechanisms underlying hypertension and cardiac and renal disease has been attempted by means of surgical and pharmacologic approaches and most recently by catheter-based interventions aimed at disrupting renal sympathetic nerve traffic. The recent developments in the area and the relevant questions that need to be addressed to advance the field further are briefly reviewed in this article.

Renal denervation in heart failure with preserved ejection fraction (RDT-PEF): a randomized controlled trial

AIM

Heart failure with preserved ejection fraction (HFpEF) is associated with increased sympathetic nervous system (SNS) tone. Attenuating the SNS with renal denervation (RDT) might be helpful and there are no data currently in humans with HFpEF.

METHODS AND RESULTS

In this single-centre, randomized, open-controlled study we included 25 patients with HFpEF [preserved left ventricular (LV) ejection fraction, left atrial (LA) dilatation or LV hypertrophy and raised B-type natriuretic peptide (BNP) or echocardiographic assessment of filling pressures]. Patients were randomized (2:1) to RDT with the Symplicity™ catheter or continuing medical therapy. The primary success criterion was not met in that there were no differences between groups at 12 months for Minnesota Living with Heart Failure Questionnaire score, peak oxygen uptake (VO2 ) on exercise, BNP, E/e', LA volume index or LV mass index. A greater proportion of patients improved at 3 months in the RDT group with respect to VO2 peak (56% vs. 13%, P = 0.025) and E/e' (31% vs. 13%, P = 0.04). Change in estimated glomerular filtration rate was comparable between groups. Two patients required plain balloon angioplasty during the RDT procedure to treat renal artery wall oedema.

CONCLUSION

This study was terminated early because of difficulties in recruitment and was underpowered to detect whether RD improved the endpoints of quality of life, exercise function, biomarkers, and left heart remodelling. The procedure was safe in patients with HFpEF, although two patients did require intraprocedure renal artery dilatation.

Renal denervation therapy for hypertension: pathways for moving development forward

This scientific statement provides a summary of presentations and discussions at a cardiovascular Think Tank co-sponsored by the American Society of Hypertension (ASH), the United States Food and Drug Administration (FDA), and the National Heart, Lung, and Blood Institute (NHLBI) held in North Bethesda, Maryland, on June 26, 2014. Studies of device therapies for the treatment of hypertension are requested by regulators to evaluate their safety and efficacy during their development programs. Think Tank participants thought that important considerations in undertaking such studies were: (1) Preclinical assessment: how likely it is that both efficacy and safety data indicating benefit in humans will be obtained, and/or whether a plausible mechanism of action for efficacy can be identified; (2) Early human trial(s): the ability to determine that the device has an acceptable benefit-to-risk balance for its use in the intended patient population and without the influence of drug therapy during a short-term follow-up period; and (3) Pivotal Phase III trial(s): the ability to prove the effectiveness of the device in a broad population in which the trial can be made as non-confounded as possible while still allowing for the determination for benefits when added to antihypertensive therapies.

Renal denervation for the management of resistant hypertension

Renal sympathetic denervation (RSD) as a therapy for patients with resistant hypertension has attracted great interest. The majority of studies in this field have demonstrated impressive reductions in blood pressure (BP). However, these trials were not randomized or sham-controlled and hence, the findings may have been overinflated due to trial biases. SYMPLICITY HTN-3 was the first randomized controlled trial to use a blinded sham-control and ambulatory BP monitoring. A surprise to many was that this study was neutral. Possible reasons for this neutrality include the fact that RSD may not be effective at lowering BP in man, RSD was not performed adequately due to limited operator experience, patients’ adherence with their anti-hypertensive drugs may have changed during the trial period, and perhaps the intervention only works in certain subgroups that are yet to be identified. Future studies seeking to demonstrate efficacy of RSD should be designed as randomized blinded sham-controlled trials. The efficacy of RSD is in doubt, but many feel that its safety has been established through the thousands of patients in whom the procedure has been performed. Over 90% of these data, however, are for the Symplicity™ system and rarely extend beyond 12 months of follow-up. Long-term safety cannot be assumed with RSD and nor should it be assumed that if one catheter system is safe then all are. We hope that in the near future, with the benefit of well-designed clinical trials, the role of renal denervation in the management of hypertension will be established.

Neuropeptide Y as an indicator of successful alterations in sympathetic nervous activity after renal sympathetic denervation

BACKGROUND

Renal sympathetic denervation (RSD) represents a safe and effective treatment option for certain patients with resistant hypertension and has been shown to decrease sympathetic activity. Neuropeptide Y (NPY) is a neurotransmitter that is co-released with norepinephrine and is up-regulated during increased sympathetic activity. The aim of the present study was to examine the effect of RSD on NPY and to analyze the association between changes in NPY levels and blood pressure reduction after RSD.

METHODS

A total of 150 consecutive patients (age 64.9 ± 10.2 years) from three clinical centers undergoing RSD were included in this study. Response to RSD was defined as an office systolic blood pressure (SBP) reduction of >10 mmHg 6 months after RSD. Venous blood samples for measurement of NPY were collected prior to and 6 months after RSD.

RESULTS

BP and NPY levels were significantly reduced by 23/9 mmHg (p = 0.001/0.001) and 0.24 mg/dL (p < 0.01) 6 months after RSD. There was a significant correlation between baseline SBP- and RSD-related systolic BP reduction (r = -0.43; p < 0.001) and between serum NPY baseline values and NPY level changes (r = -0.52; p < 0.001) at the 6-month follow-up. The BP response to RSD (>10 mmHg) was associated with a significantly greater reduction in NPY level when compared with BP non-responders (p = 0.001).

CONCLUSION

This study demonstrates an effect of RSD on serum NPY levels, a specific marker for sympathetic activity. The association between RSD-related changes in SBP and NPY levels provides further evidence of the effect of RSD on the sympathetic nervous system.

Retinal microperfusion after renal denervation in treatment-resistant hypertensive patients

BACKGROUND

High pulsatile pressure and flow in the arteries causes microvascular damage, and hence increased cardio-, and cerebrovascular complications. With advanced stages of hypertensive disease, an exaggerated pulsatile retinal capillary flow (RCF) has been shown, but data about interventional effect are missing.

METHODS

Fifty-one patients with true treatment-resistant hypertension (TRH) underwent renal denervation (RDN) using the Symplicity Flex(™) catheter and were followed for 12 months. RCF was assessed non-invasively using Scanning laser Doppler flowmetry (SLDF) before, 6 (6 M), and 12 (12 M) months after RDN. RCF was measured in systole and diastole and pulsed RCF (difference of RCF in systole minus diastole) was calculated. In addition, flicker light-induced vasodilation (representing vasodilatory capacity) was assessed.

RESULTS

Systolic and diastolic office blood pressure (BP) as well as 24-h ABPM decreased significantly 6 M and 12 M after RDN, compared to baseline values (all p < 0.001). There was a significant reduction of pulsed RCF 6 M (231 ± 81 versus 208 ± 68 AU, p = 0.046) and 12 M (194 ± 72 AU, p = 0.001) after RDN, whereas the mean RCF was unchanged. Moreover, there was a significant increase of flicker light-induced vasodilation after RDN (p = 0.043).

CONCLUSION

In hypertensive patients with TRH, we observed a decrease of pulsed RCF 6 M and 12 M after RDN and an increase of vasodilatory capacity, in parallel to decreases in BP and heart rate. The reduction of pulsed RCF after RDN implies a decrease of shear stress on the vascular wall by the pulsed blood flow. This and the increment of vasodilatory capacity suggest an improvement of retinal (and potentially cerebral) microcirculation.

Renal denervation

PURPOSE OF REVIEW

Renal denervation (RDN) has, within recent years, been suggested as a novel treatment option for patients with resistant hypertension. This review summarizes the current knowledge on this procedure as well as limitations and questions that remain to be answered.

RECENT FINDINGS

The Symplicity HTN-1 (2009) and HTN-2 (2010) studies re-introduced an old treatment approach for resistant hypertension and showed that catheter-based RDN was feasible and resulted in substantial blood pressure (BP) reductions. However, they also raised questions of durability of BP reduction, correct patient selection, anatomical and physiological effects of RDN as well as possible beneficial effects on other diseases with increased sympathetic activity. The long awaited Symplicity HTN-3 (2014) results illustrated that the RDN group and the sham-group had similar reductions in BP.

SUMMARY

Initial studies demonstrated that RDN in patients with resistant hypertension was both feasible and safe and indicated that RDN may lead to impressive reductions in BP. However, recent controlled studies question the BP lowering effect of RDN treatment. Large-scale registry data still supports the favorable BP reducing effect of RDN. We suggest that, in the near future, RDN should not be performed outside clinical studies. The degree of denervation between individual operators and between different catheters and techniques used should be clarified. The major challenge ahead is to identify which patients could benefit from RDN, to clarify the lack of an immediate procedural success parameter, and to establish further documentation of overall effect of treatment such as long-term cardiovascular morbidity and mortality.

Beneficial effects of renal sympathetic denervation on cardiovascular inflammation and remodeling in essential hypertension

BACKGROUND

Renal sympathetic denervation (RSD) represents a potential treatment option for certain patients with resistant arterial hypertension (HT). HT is associated with chronic vascular inflammation and remodeling, contributing to progressive vascular damage, and atherosclerosis. The present study aimed to evaluate the influence of RSD on cardiovascular inflammation and remodeling by determining serum levels of interleukin-6 (IL-6), high-sensitive C-reactive protein (hsCRP), matrix metalloproteinases (MMP), and tissue inhibitor of metalloproteinases (TIMP).

METHODS

A total of 60 consecutive patients (age 67.9 ± 9.6 years) undergoing RSD were included. A therapeutic response was defined as an office systolic blood pressure (SBP) reduction of >10 mmHg 6 months after RSD. Venous serum samples for measurement of hsCRP, IL-6, MMP-2, MMP-9, and TIMP-1 were collected prior to and 6 months after RSD.

RESULTS

A significant reduction in office SBP of 26.4 mmHg [SBPbaseline 169.3 mmHg (SD 11.3), p < 0.001] was documented 6 months after RSD. The serum levels of hsCRP (p < 0.001) and the pro-inflammatory cytokine IL-6 (p < 0.001) were significantly decreased compared to baseline values. The levels of MMP-9 (p = 0.024) and MMP-2 (p < 0.01) were significantly increased compared to baseline values.

CONCLUSION

In addition to the effective blood pressure reduction in response to RSD, this study demonstrates a positive effect of RSD on biomarkers reflecting vascular inflammation and remodeling. These results suggest a possible prognostic benefit of RSD in high-risk patients for endothelial dysfunction and cardiovascular remodeling as well as end-organ damage.

Interventional management in hypertension: where do we stand?

PURPOSE OF REVIEW

Device-based interventions to lower drug-resistant hypertension have made the management of this disorder more complicated. In this review, we will focus on developments in this approach to blood pressure care which have appeared over the last year in a published or abstract form.

RECENT FINDINGS

Much of the recent literature in this area is characterized by very large office systolic blood pressure reductions, on the order of 25 mmHg at 6 months after intervention. However, the largest and the most rigorously conducted trial of renal denervation failed to meet its efficacy endpoint. We will review some speculations on why that may have occurred.

SUMMARY

There is little guidance for the management of drug-resistant hypertension in existing guidelines due largely to an absence of clinical trials with hard cardiovascular outcomes; thus, most of the literature relies on short-term (generally less than 1 year) studies that are oriented toward efficacy (i.e., blood pressure reduction per se). With the failure of the Symplicity HTN3 trial to meet its efficacy endpoint, the entire field of renal denervation is under careful scrutiny. From this reviewer's perspective, this finding seems to be more of a speed-bump than a 'road closed' sign for renal denervation, a prompt to reconsider the adequacy of denervation techniques and an encouragement to continue the search for robust predictors of clinical response.

SYMPLICITY HTN 3: The death knell for renal denervation in hypertension?

Resistant hypertension is, by definition, a challenge to most physicians treating hypertension. Renal sympathetic denervation has shown promising early results in treating this condition. The SYMPLICITY HTN-3 is the most recent trial to report the effects of this technique on resistant hypertension. This review discusses this study and its surprising neutral results before ending with an overview of key lessons learned.