Persistent Increase in Blood Pressure After Renal Nerve Stimulation in Accessory Renal Arteries After Sympathetic Renal Denervation

Effect of Accessory Renal Arteries on Essential Hypertension and Related Mechanisms

BACKGROUND

This case-control study aimed to determine whether there were differences between patients with essential hypertension with accessory renal arteries (ARAs) and those without ARAs.

METHODS AND RESULTS

The enrolled patients with essential hypertension were divided into the ARA group (n=200) and control group without ARAs (n=238). After propensity matching, 394 patients (197 in each of the 2 groups), were included. The 24-hour BP (4.33/2.43 mm Hg) and daytime BP (4.48/2.61 mm Hg) of patients in the ARA group were significantly higher than those of the control group (P<0.05). The flow-mediated dilation was lower in the ARA group (5.98±2.70 versus 5.18±2.66; P<0.05). In correlation analysis, the horizontal plasma aldosterone concentration had the highest correlation with 24-hour, daytime, and nighttime systolic BP (r=0.263, 0.247, and 0.243, respectively; P<0.05) and diastolic BP (r=0.325, 0.298, and 0.317, respectively; P<0.05). As for multivariate regression analysis, plasma aldosterone concentration was a significant risk factor for elevated 24-hour, daytime, and nighttime systolic BP (β=0.249 [95% CI, 0.150-0.349], 0.228 [95% CI, 0.128-0.329], and 0.282 [95% CI, 0.187-0.377], respectively; P<0.05) and elevated diastolic BP (β=0.289 [95% CI, 0.192-0.385], 0.256 [95% CI, 0.158-0.353], and 0.335 [95% CI, 0.243-0.427], respectively; P<0.05). Direct renin concentration was also a risk factor for 24-hour and daytime BPs, whereas heart rate was a risk factor correlated with 24-hour, daytime, and nighttime diastolic BP (all P<0.05). For the mixed-effects model for repeated measures, the results were similar to results of the multivariate regression analysis (all P<0.05).

CONCLUSIONS

ARAs could contribute a higher BP of patients with essential hypertension and might promote the development of essential hypertension. The mechanism might be related to overactivation of the renin-angiotensin-aldosterone system and sympathetic nervous system.

Advances in Renal Denervation in the Treatment of Hypertension

Hypertension significantly increases the risk of cardiovascular events and it is associated with high rates of disability and mortality. Hypertension is a common cause of cardiovascular and cerebrovascular accidents, which severely affect patients’ quality of life and lifespan. Current treatment strategies for hypertension are based primarily on medication and lifestyle interventions. The renal sympathetic nervous system plays an important role in the pathogenesis of hypertension, and catheter-based renal denervation (RDN) has provided a new concept for the treatment of hypertension. In recent years, studies on RDN have been performed worldwide. This article reviews the latest preclinical research and clinical evidence for RDN.

Renal Sympathetic Denervation for Hypertension

Arterial hypertension is the most prevalent global modifiable risk factor for cardiovascular morbidity and mortality. Despite the availability of numerous pharmacologic treatments, many patients do not achieve guideline-recommended blood pressure targets. Therefore, renal sympathetic denervation (RDN), a process in which catheter-directed techniques are used to ablate portions of the renal artery to reduce sympathetic activity, has been extensively investigated as a complementary and nonpharmacologic approach for the treatment of arterial hypertension. This review seeks to discuss the pathophysiological rationale of this strategy, to survey its history and development, and to highlight the current clinical evidence and possible future directions of its employment. In sum, RDN has demonstrated itself to be a safe and well-tolerated endovascular intervention that can reliably contribute to improved blood pressure control and, perhaps ultimately, significant cardiovascular prognosis.

The role of renal nerve stimulation in percutaneous renal denervation for hypertension: A mini-review

Recent trials have demonstrated the efficacy and safety of percutaneous renal sympathetic denervation (RDN) for blood pressure (BP)-lowering in patients with uncontrolled hypertension. Nevertheless, major challenges exist, such as the wide variation of BP-lowering responses following RDN (from strong response to no response) and lack of feasible and reproducible peri-procedural predictors for patient response. Both animal and human studies have demonstrated different patterns of BP responses following renal nerve stimulation (RNS), possibly related to varied regional proportions of sympathetic and parasympathetic nerve tissues along the renal arteries. Animal studies of RNS have shown that rapid electrical stimulation of the renal arteries caused renal artery vasoconstriction and increased norepinephrine secretion with a concomitant increase in BP, and the responses were attenuated after RDN. Moreover, selective RDN at sites with strong RNS-induced BP increases led to a more efficient BP-lowering effect. In human, when RNS was performed before and after RDN, blunted changes in RNS-induced BP responses were noted after RDN. The systolic BP response induced by RNS before RDN and blunted systolic BP response to RNS after RDN, at the site with maximal RNS-induced systolic BP response before RDN, both correlated with the 24-h ambulatory BP reductions 3-12 months following RDN. In summary, RNS-induced BP changes, before and after RDN, could be used to assess the immediate effect of RDN and predict BP reductions months following RDN. More comprehensive, large-scale and long term trials are needed to verify these findings.

Present Evidence of Determinants to Predict the Efficacy of Renal Denervation

Sympathetic overactivation is one of the main contributors to development and progress of hypertension. Renal denervation (RDN) has been evidenced by series of clinical trials for its efficacy and safety to treat overactivated sympathetic nervous system induced diseases. However, the results were inconsistent and not all patients benefited from RDN. Appropriate patient selection and intraoperative factors to improve the efficacy of RDN need to be solved urgently. Over the decade, research studies on the correlations between indicators and the antihypertensive effects have been conducted and made a fairly well progress. Herein, we comprehensively reviewed the research studies on how to make RDN more predictable or improve the efficacy of RDN and summarized these potential indicators or devices which might be applied in clinical settings.

Optimal Strategy for HIFU-Based Renal Sympathetic Denervation in Canines

Background: The association between the treatment efficacy and safety of high-intensity focused ultrasound (HIFU)-based renal sympathetic denervation (RDN) and the acoustic energy dose applied has not been fully studied and may provide important understanding of the mechanism that led to failure of the WAVE IV trial. The objective of this study was to externally deliver different HIFU doses to canines for RDN treatment and to investigate the optimal energy dose for HIFU-based RDN.

Methods: Thirty canines were divided into five RDN groups according to dose of acoustic energy applied, and a sham control group that consisted of four canines was used for comparisons. All animals in the RDN groups underwent the RDN procedure with different acoustic energy doses, while in the sham control group, renal arteries were harvested without being subjected to acoustic energy delivery and were imaged using color Doppler flow imaging (CDFI). Blood pressure (BP) was recorded, and blood samples were collected before the RDN procedure and at 28 days after the RDN procedure. Histological examinations and measurement of renal tissue norepinephrine concentration were performed in all retrieved samples.

Results: Suppression of BP was significant in the 300 W (15.17/8.33 ± 1.47/1.21 mmHg), 250 W (14.67/9.33 ± 1.21/1.37 mmHg), and 200 W (13.17/9.17 ± 2.32/1.84 mmHg) groups. Semiquantitative histological assessment of periarterial nerves around the kidney revealed that target nerves in the 300 W (9.77 ± 0.63), 250 W (9.42 ± 0.67), and 200 W (9.58 ± 0.54) groups had the highest nerve injury scores, followed by the 150 W group (5.29 ± 0.62). Furthermore, decreased renal tissue norepinephrine concentration, together with decreased expression of tyrosine hydroxylase in the 300, 250, and 200 W groups demonstrated effective sympathetic depression following sufficient acoustic energy deposition. However, the renal artery injury score in the 300 W group (0.93 ± 0.13) was significantly higher than in the other groups (p < 0.001).

Conclusion: This study provides evidence that RDN effectiveness is based on the energy dose delivered and that 200–250 W is effective and safe in normal-sized canines.

Circular Radio-Frequency Electrode With MEMS Temperature Sensors for Laparoscopic Renal Sympathetic Denervation

OBJECTIVE

Laparoscopic renal denervation (LRDN) ablates sympathetic nerves on the outer wall of a renal artery to treat autonomic nervous system disorders such as hypertension and arrhythmia. Here, we developed a new circular radio frequency (RF) electrode for LRDN using micro-electro-mechanical systems (MEMS) technology.

METHODS

The electrode consists of a parallel bipolar MEMS electrode, two MEMS thermocouples, and a shape-memory alloy (SMA) substrate. The electrode is automatically wrapped and unwrapped under actuation controlled by the heat generated by RF energy on the electrode-tissue interface. The electrode was designed through a computational simulation analysis, and its actuation and temperature-sensing performance were tested in laboratory experiments and a porcine animal study.

RESULTS

In an in-vivo study of porcine renal arteries, the electrode could automatically wrap and unwrap around an artery during LRDN. The bipolar MEMS electrode required 13 V_rms for heat generation up to 60°C, while the two MEMS thermocouples reliably measured the temperature without noise signals (a temperature coefficient of 38.3 or 38.5 µV/°C and an accuracy of ±0.44 or ±0.49°C). As revealed in a histological analysis using hematoxylin and eosin staining and Masson's trichrome staining, the renal artery was intact after LRDN.

CONCLUSION

The circular RF electrode improves the safety of LRDN by reliably measuring the electrode temperature of the electrode during RDN and enhances the effectiveness of LRDN by reducing the complicated manipulations of the surgical instrument.

SIGNIFICANCE

The developed circular RF electrode will pave the way for LRDN treatment of autonomic nervous system disorders.

Device Therapy of Hypertension

In the past decade, efforts to improve blood pressure control have looked beyond conventional approaches of lifestyle modification and drug therapy to embrace interventional therapies. Based upon animal and human studies clearly demonstrating a key role for the sympathetic nervous system in the etiology of hypertension, the newer technologies that have emerged are predominantly aimed at neuromodulation of peripheral nervous system targets. These include renal denervation, baroreflex activation therapy, endovascular baroreflex amplification therapy, carotid body ablation, and pacemaker-mediated programmable hypertension control. Of these, renal denervation is the most mature, and with a recent series of proof-of-concept trials demonstrating the safety and efficacy of radiofrequency and more recently ultrasound-based renal denervation, this technology is poised to become available as a viable treatment option for hypertension in the foreseeable future. With regard to baroreflex activation therapy, endovascular baroreflex amplification, carotid body ablation, and programmable hypertension control, these are developing technologies for which more human data are required. Importantly, central nervous system control of the circulation remains a poorly understood yet vital component of the hypertension pathway and mandates further investigation. Technology to improve blood pressure control through deep brain stimulation of key cardiovascular control territories is, therefore, of interest. Furthermore, alternative nonsympathomodulatory intervention targeting the hemodynamics of the circulation may also be worth exploring for patients in whom sympathetic drive is less relevant to hypertension perpetuation. Herein, we review the aforementioned technologies with an emphasis on the preclinical data that underpin their rationale and the human evidence that supports their use.

Laparoscopic Ablation System for Complete Circumferential Renal Sympathetic Denervation

GOAL

The catheter-based renal denervation (RDN) showed promising results for patients in lowering BP, but there were also many non-responders. One of the possible reasons was the incomplete neural ablation due to the ablation of renal nerves at random sites resulting in asymmetric innervation patterns along the renal artery.

METHODS

We developed a laparoscopic ablation system that is optimized for complete RDN regardless of renal arterial innervation and size. To demonstrate its effectiveness, we evaluated the system using computational simulation and 28-day survival model using pigs.

RESULTS

The ablations were focused around the tunica externa, and the ablation patterns could be predicted numerically during RDN treatment. In the animal study, the mean reduction of systolic BP and diastolic BP in the bilateral main renal arteries was 22.8 mmHg and 14.4 mmHg (P<0.001), respectively. The respond to immunostaining targeting tyrosine hydroxylase was significantly reduced at treatment site (108.2 ± 7.5 (control) vs. 63.4 ± 8.7 (treatment), P<0.001), and an increased degree of sympathetic signals interruption to kidneys was associated with the efficacy of RDN.

CONCLUSION

The laparoscopic ablation system achieved complete circumferential RDN at the treatment site and could numerically predict the ablation patterns.

SIGNIFICANCE

These findings clearly suggest that the proposed system can significantly improve the RDN effectiveness by reducing the variation to the percentage of injured nerves and open up a new opportunity to treat uncontrolled hypertension.

Comprehensive Assessment of Human Accessory Renal Artery Periarterial Renal Sympathetic Nerve Distribution

OBJECTIVES

The aim of this study was to understand the anatomy of periarterial nerve distribution in human accessory renal arteries (ARAs).

BACKGROUND

Renal denervation is a promising technique for blood pressure control. Despite the high prevalence of ARAs, the anatomic distribution of periarterial nerves around ARAs remains unknown.

METHODS

Kidneys with surrounding tissues were collected from human autopsy subjects, and histological evaluation was performed using morphometric software. An ARA was defined as an artery arising from the aorta above or below the dominant renal artery (DRA) or an artery that bifurcated within 20 mm of the takeoff of the DRA from the aorta. The DRA was defined as an artery that perfused >50% of the kidney.

RESULTS

A total of 7,287 nerves from 14 ARAs and 9 DRAs were evaluated. The number of nerves was smaller in the ARA than DRA (median: 30 [interquartile range: 17.5 to 48.5] vs. 49 [interquartile range: 36 to 76]; p < 0.0001). In both ARAs and DRAs, the distance from the arterial lumen to nerve was shortest in the distal, followed by the middle and proximal segments. On the basis of the post-mortem angiography, ARAs were divided into large (≥3 mm diameter) and small (<3 mm) groups. The number of nerves was greatest in the DRA, followed by the large and small ARA groups (53 [41 to 97], 38 [25 to 53], and 24.5 [10.5 to 36.3], respectively; p = 0.001).

CONCLUSIONS

ARAs showed a smaller number of nerves than DRAs, but these results were dependent on the size of the ARA. Ablation, especially in large ARAs, may allow more complete denervation with the potential to further reduce blood pressure.

Quantitative analysis of renal arterial variations affecting the eligibility of catheter-based renal denervation using multi-detector computed tomography angiography

Catheter-based renal denervation (RDN) was introduced to treat resistant hypertension. However, the reduction in blood pressure after the RDN was modest. Catheter-based RDN was performed only at main renal arteries, except for accessory and branch arteries due to the diameter being too small for the catheter to approach. Here, we retrospectively analyzed the anatomy of diverse renal arteries via 64-channel multi-detector computed tomography angiograms of 314 consecutive donors who underwent living donor nephrectomy from January 2012 to July 2017. Occurrence rates of one or more accessory renal arteries in donors were 25.3% and 19.4% on the left and right sides, respectively. Early branching rates before 25 mm from the aorta to the right and left renal arteries were 13.7% and 10.5%, respectively. Overall, 63.1% and 78.3% of donors had no accessory artery bilaterally and no branched renal artery, respectively. As a result, 47.1% had only main renal arteries without an accessory artery and early-branching artery. Approximately half of the donors had multiple small renal arteries bilaterally, for which catheter-based denervation may not be suitable. Thus, preoperative computed tomography angiography requires careful attention to patient selection, and there is a need for improved methods for denervation at various renal arteries.

Laparoscopic Renal Denervation System for Treating Resistant Hypertension: Overcoming Limitations of Catheter-Based Approaches

GOAL

In a pivotal clinical trial, the percutaneous catheter-based renal denervation system developed to treat resistant hypertension did not show effectiveness in reducing blood pressure because of its fundamental limitation to ablate deeper nerves present around the renal artery.

METHODS

We propose a new renal denervation strategy called laparoscopicdenervation system (LDS) based-on laparoscopy procedure to ablate the renal nerves completely but inhibit the thermal arterial damage.The system has flexible electrodes to bend around the arterial wall to ablate nervesThe simulation study using validated in-silico models evaluated the heat distributionon the outer arterial wall,and an acute animal study (swine model) was conducted to demonstrate the feasibility of LDS in vivo.

RESULTS

The simulation studyconfirmedthat LDS could localize the heat distributionbetween the electrode and the outer arterial wall. In the animal study, we could maximize nerve denervation by the localizing ablation energy within the renal nerves and achieve nerve denaturationand decrease in neural density by 20.78% (P < 0.001), while maintaining a constant tip temperature of 65 °C for the duration of 70 s treatment. The study confirmed intact lumen artery through histological analysis and acute reduction in systolic blood pressure by 9.55 mmHg (p < 0.001) Conclusion: The LDS presented here has potential to effectively and safely ablate the renal nerves, independent of anatomical variation and nerve distribution, to control hypertension in real clinical conditions.

SIGNIFICANCE

LDS approach is innovative, inventive, and presents a novel technique totreat hypertension.

Renal Denervation in Asia: Consensus Statement of the Asia Renal Denervation Consortium

The Asia Renal Denervation Consortium consensus conference of Asian physicians actively performing renal denervation (RDN) was recently convened to share up-to-date information and regional perspectives, with the goal of consensus on RDN in Asia. First- and second-generation trials of RDN have demonstrated the efficacy and safety of this treatment modality for lowering blood pressure in patients with resistant hypertension. Considering the ethnic differences of the hypertension profile and demographics of cardiovascular disease demonstrated in the SYMPLICITY HTN (Renal Denervation in Patients With Uncontrolled Hypertension)-Japan study and Global SYMPLICITY registry data from Korea and Taiwan, RDN might be an effective hypertension management strategy in Asia. Patient preference for device-based therapy should be considered as part of a shared patient-physician decision process. A practical population for RDN treatment could consist of Asian patients with uncontrolled essential hypertension, including resistant hypertension. Opportunities to refine the procedure, expand the therapy to other sympathetically mediated diseases, and explore the specific effects on nocturnal and morning hypertension offer a promising future for RDN. Based on available evidence, RDN should not be considered a therapy of last resort but as an initial therapy option that may be applied alone or as a complementary therapy to antihypertensive medication.

Selective Renal Denervation Guided by Renal Nerve Stimulation in Canine

Renal nerve stimulation (RNS) can result in substantial blood pressure (BP) elevation, and the change was significantly blunted when repeated stimulation after ablation. However, whether RNS could provide a meaningful renal nerve mapping for identification of optimal ablation targets in renal denervation (RDN) is not fully clear. Here, we compared the antihypertensive effects of selective RDN guided by two different BP responses to RNS and explored the nerve innervations at these sites in Kunming dogs. Our data indicated that ablation at strong-response sites showed a more systolic BP-lowering effect than at weak-response sites ( P =0.002), as well as lower levels of tyrosine hydroxylase and norepinephrine in kidney and a greater reduction in plasma norepinephrine ( P =0.004 for tyrosine hydroxylase, P =0.002 for both renal and plasma norepinephrine). Strong-response sites showed a greater total area and mean number of renal nerves than weak-response sites ( P =0.012 for total area and P <0.001 for mean number). Systolic BP-elevation response to RNS before RDN and blunted systolic BP-elevation to RNS after RDN were correlated with systolic BP changes at 4 weeks follow-up ( R =0.649; P =0.012 and R =0.643; P =0.013). Changes of plasma norepinephrine and renal norepinephrine levels at 4 weeks were also correlated with systolic BP changes at 4 weeks ( R =0.837, P <0.001 and R =0.927, P <0.001). These data suggest that selective RDN at sites with strong BP-elevation response to RNS could lead to a more efficient RDN. RNS is an effective method to identify the nerve-enriched area during RDN procedure and improve the efficacy of RDN.

Electrical stimulation-based renal nerve mapping exacerbates ventricular arrhythmias during acute myocardial ischaemia

OBJECTIVE

Blood pressure elevation in response to transient renal nerve stimulation (RNS) has been used to determine the ablation target and endpoint of renal denervation. This study aimed to evaluate the safety of transient RNS in canines with normal or ischaemic hearts.

METHODS

In ten normal (Group 1) and six healed myocardial infarction (HMI) (Group 2) canines, a large-tip catheter was inserted into the left or right renal artery to perform transient RNS. The left stellate ganglion neural activity (LSGNA) and ventricular electrophysiological parameters were measured at baseline and during transient RNS. In another 20 acute myocardial infarction (AMI) canines, RNS (Group 3, n = 10) or sham RNS (Group 4, n = 10) was intermittently (1 min ON and 4 min OFF) performed for 1 h following AMI induction. The LSGNA and AMI-induced ventricular arrhythmias were analysed.

RESULTS

In normal and HMI canines, although transient RNS significantly increased the LSGNA and facilitated the action potential duration (APD) alternans, it did not induce any ventricular arrhythmias and did not change the ventricular effective refractory period, APD or maximum slope of the APD restitution curve. In AMI canines, transient RNS significantly exacerbated LSG activation and promoted the incidence of ventricular arrhythmias.

CONCLUSION

Transient RNS did not increase the risk of ventricular arrhythmias in normal or HMI hearts, but it significantly promoted the occurrence of ventricular arrhythmias in AMI hearts. Therefore, electrical stimulation-based renal nerve mapping may be unsafe in AMI patients and in patients with a high risk for malignant ventricular arrhythmias.

Is renal denervation still a treatment option in cardiovascular disease?

The role of renal sympathetic denervation (RDN) has been the topic of ongoing debate ever since the impressive initial results. The rationale of RDN is strong and supported by non-clinical studies, which lies in uncoupling the autonomic nervous crosstalk between the kidneys and the central nervous system. Since we know that cardiovascular diseases, such as hypertension, atrial, ventricular arrhythmias and heart failure (HF) are related to sympathetic (over)activity, modulation of the renal nerve activity appears to be a reasonable and attractive therapeutic target in these patients. This review will focus on the existing evidence and potential future perspectives for RDN as treatment option in cardiovascular disease.

Phase II randomized sham-controlled study of renal denervation for individuals with uncontrolled hypertension - WAVE IV

OBJECTIVES

The aim of this double-blind, randomized, sham-controlled study was to verify the blood pressure (BP)-lowering efficacy of externally delivered focused ultrasound for renal denervation (RDN).

BACKGROUND

Nonrandomized, first proof-of-concept study and experimental evidence suggested that noninvasive techniques of RDN emerged as an alternative approach of RDN to invasive technologies.

METHODS

WAVE IV, an international, randomized (1 : 1) sham-controlled, double-blind prospective clinical study, was prematurely stopped. Patients were enrolled if office BP was at least 160 mmHg and 24-h ambulatory BP was at least 135 mmHg, while taking three or more antihypertensive medications. The treatment consisted of bilateral RDN using therapeutic levels of ultrasound energy and the sham consisted of bilateral application of diagnostic levels of ultrasound energy.

RESULTS

In the 81 treated patients neither changes in office BP at 12 and 24 weeks, nor changes in 24-h ambulatory BP at 24-week follow-up visit differed between the two groups significantly. Of note, no safety signal was observed. Adherence analysis disclosed full adherence in 77% at baseline and 82% at 6 months' follow-up visit. Post hoc analysis revealed that stricter criteria for stabilization of BP at baseline were associated with a numerically greater change in 24-h ambulatory BP in the RDN group than in the sham group.

CONCLUSION

Our data did not prove that antihypertensive efficacy of the externally delivered focused ultrasound for RDN was greater than the sham effect. Stabilization of BP at baseline was identified as an important determinant of BP changes.

Selective vs. Global Renal Denervation: a Case for Less Is More

PURPOSE OF REVIEW

Review the renal nerve anatomy and physiology basics and explore the concept of global vs. selective renal denervation (RDN) to uncover some of the fundamental limitations of non-targeted renal nerve ablation and the potential superiority of selective RDN.

RECENT FINDINGS

Recent trials testing the efficacy of RDN showed mixed results. Initial investigations targeted global RDN as a therapeutic goal. The repeat observation of heterogeneous response to RDN including non-responders with lack of a BP reduction, or even more unsettling, BP elevations after RDN has raised concern for the detrimental effects of unselective global RDN. Subsequent studies have suggested the presence of a heterogeneous fiber population and the potential utility of renal nerve stimulation to identify sympatho-stimulatory fibers or "hot spots." The recognition that RDN can produce heterogeneous afferent sympathetic effects both change therapeutic goals and revitalize the potential of therapeutic RDN to provide significant clinical benefits. Renal nerve stimulation has emerged as potential tool to identify sympatho-stimulatory fibers, avoid sympatho-inhibitory fibers, and thus guide selective RDN.

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.

Treatment of atrial fibrillation in patients with enhanced sympathetic tone by pulmonary vein isolation or pulmonary vein isolation and renal artery denervation: clinical background and study design : The ASAF trial: ablation of sympathetic atrial fibrillation

BACKGROUND

Hypertension is an important, modifiable risk factor for the development of atrial fibrillation (AF). Even after pulmonary vein isolation (PVI), 20-40% experience recurrent AF. Animal studies have shown that renal denervation (RDN) reduces AF inducibility. One clinical study with important limitations suggested that RDN additional to PVI could reduce recurrent AF.

OBJECTIVE

The goal of this multicenter randomized controlled study is to investigate whether RDN added to PVI reduces AF recurrence.

METHODS

The main end point is the time until first AF recurrence according to EHRA guidelines after a blanking period of 3 months. Assuming a 12-month accrual period and 12 months of follow-up, a power of 0.80, a two-sided alpha of 0.05 and an expected drop-out of 10% per group, 69 patients per group are required. We plan to randomize a total of 138 hypertensive patients with AF and signs of sympathetic overdrive in a 1:1 fashion. Patients should use at least two antihypertensive drugs. Sympathetic overdrive includes obesity, exercise-induced excessive blood pressure (BP) increase, significant white coat hypertension, hospital admission or fever induced AF, tachycardia induced AF and diabetes mellitus. The interventional group will undergo PVI + RDN and the control group will undergo PVI.

RESULTS

Patients will have follow-up for 1 year, and continuous loop monitoring is advocated.

CONCLUSION

This randomized, controlled study will elucidate if RDN on top of PVI reduces AF recurrence.

Predictive factors for successful renal denervation: should we use them in clinical trials?

Renal denervation (RDN) is facing various challenges to its initial claimed value in hypertension treatment. Major concerns are the choice of the patients and the technical efficacy of the RDN. Different factors have been described as predicting the capacity of RDN to decrease blood pressure. These factors are related to the patients, the procedure and the tools to confirm successful neural ablation. Their use in future trials should help to improve RDN trials understanding and outcomes. This review summarizes the different predictive factors available and their potential benefits in patient selection and in procedure guidance.

Renal sympathetic denervation for treatment of patients with atrial fibrillation: Reappraisal of the available evidence

Afferent renal sympathetic nerve signaling regulates central sympathetic outflow. In this regard, renal sympathetic denervation has emerged as a novel interventional strategy for treatment of patients with resistant hypertension. Despite the disappointing results of the Simplicity HTN-3 randomized controlled trial, promoters of renal denervation argue that the negative results were due to ineffective denervation technique and poor patient selection. Yet, long-term "pathologic" increase of efferent sympathetic nerve activity is observed in many chronic disease states characterized by sympathetic overactivity, such as arrhythmia, heart failure, insulin resistance, and chronic kidney disease. In this review, we highlight the contemporary evidence on the safety/efficacy of renal denervation in the treatment of patients with atrial fibrillation.