The Potential Role of Catheter-Based Renal Sympathetic Denervation in Chronic and End-Stage Kidney Disease

Renal Denervation in End-Stage Renal Disease: Current Evidence and Perspectives

In patients with end-stage renal disease (ESRD) undergoing haemodialysis, hypertension is of common detection and frequently inadequately controlled. Multiple pathophysiological mechanisms are involved in the development and progression of the ESRD-related high blood pressure state, which has been implicated in the increased cardiovascular risk reported in this hypertensive clinical phenotype. Renal sympathetic efferent and afferent nerves play a relevant role in the development and progression of elevated blood pressure values in patients with ESRD, often leading to resistant hypertension. Catheter-based bilateral renal nerves ablation has been shown to exert blood pressure lowering effects in resistant hypertensive patients with normal kidney function. Promising data on the procedure in ESRD patients with resistant hypertension have been reported in small scale pilot studies. Denervation of the native non-functioning kidney's neural excitatory influences on central sympathetic drive could reduce the elevated cardiovascular morbidity and mortality seen in ESRD patients. The present review article will focus on the promising results obtained with renal denervation in patients with ESRD, its mechanisms of action and future perspectives in these high risk patients.

Catheter-Based Renal Denervation Therapy: Evolution of Evidence and Future Directions

Motivated by the persistence of uncontrolled blood pressure and its public health impact, the development and evaluation of device-based therapies for hypertension has advanced at an accelerated pace to complement pharmaceutical and lifestyle intervention strategies. Countering widespread interest from early studies, the lack of demonstrable efficacy for renal denervation (RDN) in a large, sham-controlled randomized trial motivated revision of trial design and conduct to account for confounding variables of procedural technique, medication variability, and selection of both patients and end points. Now amidst varied trial design and methods, several sham-controlled, randomized trials have demonstrated clinically meaningful reductions in blood pressure with RDN. With this momentum, additional studies are underway to position RDN as a potential part of standard therapy for the world's leading cause of death and disability. In parallel, further studies will address unresolved issues including durability of blood pressure lowering and reduction in antihypertensive medications, late-term safety, and impact on clinical outcomes. Identifying predictors of treatment effect and surveys of patient-reported outcomes and treatment preferences are also evolving areas of investigation. Aside from confirmatory studies of safety and effectiveness, these additional studies will further inform patient selection, expand experience with RDN in broader populations with hypertension, and provide guidance to how RDN may be incorporated into treatment pathways.

Renal Deafferentation Prevents Progression of Hypertension and Changes to Sympathetic Reflexes in a Rabbit Model of Chronic Kidney Disease

[Figure: see text].

Blunted natriuretic response to saline loading in sheep with hypertensive kidney disease following radiofrequency catheter-based renal denervation

Renal sympathetic nerves contribute to renal excretory function during volume expansion. We hypothesized that intact renal innervation is required for excretion of a fluid/electrolyte load in hypertensive chronic kidney disease (CKD) and normotensive healthy settings. Blood pressure, kidney hemodynamic and excretory response to 180 min of isotonic saline loading (0.13 ml/kg/min) were examined in female normotensive (control) and hypertensive CKD sheep at 2 and 11 months after sham (control-intact, CKD-intact) or radiofrequency catheter-based RDN (control-RDN, CKD-RDN) procedure. Basal blood pressure was ~ 7 to 9 mmHg lower at 2, and 11 months in CKD-RDN compared with CKD-intact sheep. Saline loading did not alter glomerular filtration rate in any group. At 2 months, in response to saline loading, total urine and sodium excretion were ~ 40 to 50% less, in control-RDN and CKD-RDN than intact groups. At 11 months, the natriuretic and diuretic response to saline loading were similar between control-intact, control-RDN and CKD-intact groups but sodium excretion was ~ 42% less in CKD-RDN compared with CKD-intact at this time-point. These findings indicate that chronic withdrawal of basal renal sympathetic activity impairs fluid/electrolyte excretion during volume expansion. Clinically, a reduced ability to excrete a saline load following RDN may contribute to disturbances in body fluid balance in hypertensive CKD.

Efficacy and safety of renal denervation for hypertension in patients with chronic kidney disease: a meta-analysis

BACKGROUND

Renal denervation (RDN) is a new treatment for hypertension in patients with chronic kidney disease (CKD), but its efficacy is still debated. This meta-analysis aimed to evaluate the efficacy and safety of RDN for hypertension in patients with CKD.

METHODS

PubMed, Web of Science, EMBASE, and Ovid databases were searched for relevant studies published. We performed both fixed- and random-effects meta-analyses of the changes in blood pressure, estimated glomerular filtration rate (eGFR), and urinary albumin-to-creatinine ratio (UACR) after RDN.

RESULTS

The meta-analysis included 238 patients from 11 single-center, non-randomized, uncontrolled studies. Office blood pressure and 24-hour ambulatory blood pressure (24 h-ABP) showed a significant reduction 1 month after RDN (p < 0.05). This decrease of 24 h-ABP persisted for 24 months after RDN showed difference systolic blood pressure (p < 0.001) and diastolic blood pressure (p = 0.001). The 24 h-ABP exhibited a similar trend in the subgroup analysis. eGFR measurements obtained at each time point of analysis after RDN were not significantly different from those obtained before (p > 0.05). UACR levels were significantly reduced at 3 months and 6 months after RDN (p < 0.001). After RDN, the heart rate showed no significant changes (p > 0.05), and few major complications were encountered.

CONCLUSIONS

The meta-analysis showed that RDN may be effective and safe for treating CKD patients with hypertension. Well-designed randomized controlled trials of RDN are urgently needed to confirm the safety and reproducibility of RDN and to assess its impact on clinical outcomes.

Mechanism of Radix Astragali and Radix Salviae Miltiorrhizae Ameliorates Hypertensive Renal Damage

Hypertensive-induced renal damage (HRD) is an important public health and socioeconomic problem worldwide. The herb pair Radix Astragali- (RA-) Radix Salviae Miltiorrhizae (RS) is a common prescribed herbal formula for the treatment of HRD. However, the underlying mechanisms are unclear. The purpose of our study is to explore the mechanism of combination of Radix Astragali (RA) and Radix Salviae Miltiorrhizae (RS) ameliorating HRD by regulation of the renal sympathetic nerve. Thirty 24-week-old spontaneously hypertensive rats (SHRs) as the experimental group were randomly divided into the RA group, the RS group, the RA+RS group, the valsartan group, and the SHR group and six age-matched Wistar Kyoto rats (WKY) as the control group. After 4 weeks of corresponding drug administration, venipuncture was done to collect blood and prepare serum for analysis. A color Doppler ultrasound diagnostic instrument was used to observe renal hemodynamics. Enzyme-linked immunosorbent assay was used to detect norepinephrine (NE), epinephrine (E), angiotensin II (Ang II), and B-type brain natriuretic peptide (BNP). Simultaneously, the kidneys were removed immediately and observed under a transmission electron microscope to observe the ultrastructural changes. And the concentration of transforming growth factor-β1 (TGF-β1), angiotensin type 1 receptor (AT1), and nitric oxide (NO) was detected by immunohistochemistry. Our results showed that renal ultrasonography of rats showed no significant difference in renal size among groups. The RA+RS group had obviously decreased vascular resistance index. The levels of NE, E, BNP, Ang II, AT1, and TGF-β1 were decreased (P < 0.05), and the density of NO was increased. Pathological damage of the kidney was alleviated. In conclusion, the results of the present study suggested sympathetic overexpression in the pathogenesis of HRD. The combination of RA and RS may inhibit the hyperexcitability of sympathetic nerves and maintain the normal physiological structure and function of kidney tissue and has a protective effect on the cardiovascular system.

Function of Renal Nerves in Kidney Physiology and Pathophysiology

Renal sympathetic (efferent) nerves play an important role in the regulation of renal function, including glomerular filtration, sodium reabsorption, and renin release. The kidney is also innervated by sensory (afferent) nerves that relay information to the brain to modulate sympathetic outflow. Hypertension and other cardiometabolic diseases are linked to overactivity of renal sympathetic and sensory nerves, but our mechanistic understanding of these relationships is limited. Clinical trials of catheter-based renal nerve ablation to treat hypertension have yielded promising results. Therefore, a greater understanding of how renal nerves control the kidney under physiological and pathophysiological conditions is needed. In this review, we provide an overview of the current knowledge of the anatomy of efferent and afferent renal nerves and their functions in normal and pathophysiological conditions. We also suggest further avenues of research for development of novel therapies targeting the renal nerves.

Norepinephrine turnover in the left ventricle of subtotally nephrectomized rats

Increased activity of the sympathetic nervous system (SNS) has been proposed as a risk factor for increased cardiovascular mortality in patients with chronic kidney disease (CKD). Information on the activity of cardiac sympathetic innervation is non-homogeneous and incomplete. The aim of our study was to evaluate the tonic effect of SNS on heart rate, norepinephrine turnover and direct and indirect effects of norepinephrine in left ventricles of subtotally nephrectomized rats (SNX) in comparison with sham-operated animals (SHAM). Renal failure was verified by measuring serum creatinine and urea levels. SNX rats developed increased heart rates and blood pressure (BP). The increase in heart rate was not caused by sympathetic overactivity as the negative chronotropic effect of metipranolol did not differ between the SNX and SHAM animals. The positive inotropic effects of norepinephrine and tyramine on papillary muscle were not significantly different. Norepinephrine turnover was measured after the administration of tyrosine hydroxylase inhibitor, pargyline, tyramine, desipramine, and KCl induced depolarization. The absolute amount of released norepinephrine was comparable in both groups despite a significantly decreased norepinephrine concentration in the cardiac tissue of the SNX rats. We conclude that CKD associated with renal denervation in rats led to adaptive changes characterized by an increased reuptake and intracellular norepinephrine turnover which maintained normal reactivity of the heart to sympathetic stimulation.

QardioArm Upper Arm Blood Pressure Monitor Against Omron M3 Upper Arm Blood Pressure Monitor in Patients With Chronic Kidney Disease: A Validation Study According to the European Society of Hypertension International Protocol Revision 2010

Background

Hypertension is considered as a main risk factor for chronic kidney disease development and progression. Thus, the control and evaluation of this disease with new software and devices are especially important in patients who suffer from chronic kidney disease.

Objective

This study aimed to validate the QardioArm mobile device, which is used for blood pressure (BP) self-measurement in patients who suffer from chronic kidney disease, by following the European Society of Hypertension International Protocol 2 (ESH-IP2) guidelines.

Methods

A validation study was carried out by following the ESH-IP2 guidelines. A sample of 33 patients with chronic kidney disease self-measured their BP by using the QardioArm and Omron M3 Intellisense devices. Heart rate (HR), diastolic BP, and systolic BP were measured.

Results

The QardioArm fulfilled the ESH-IP2 validation criteria in patients who suffered from chronic kidney disease.

Conclusions

Thus, this study is considered as the first validation using a wireless upper arm oscillometric device connected to an app to measure BP and HR meeting the ESH-IP2 requirements in patients who suffer from chronic kidney disease. New validation studies following the ESH-IP2 guidelines should be carried out using different BP devices in patients with specific diseases.

Central Blood Pressure and Pulse Wave Velocity Changes Post Renal Denervation in Patients With Stages 3 and 4 Chronic Kidney Disease: The Regina RDN Study

Background:

Central aortic blood pressures and arterial stiffness are better indicators of cardiovascular outcomes than brachial blood pressures. However, their response to renal denervation (RDN) in patients with Stage 3 and Stage 4 chronic kidney disease (CKD) has not yet been examined.

Objective:

To evaluate the impact of RDN on central blood pressures (CBP), brachial (office and ambulatory) blood pressures, arterial stiffness, glomerular filtration rate (GFR), 24-hour urine protein, and selective cardiac parameters observed on echocardiograms.

Design:

Single-center, single-arm with pre-/post-RDN follow-up.

Setting:

Patients were recruited from the multidisciplinary CKD clinic, Regina General Hospital, Canada.

Patients:

About 25 consecutive patients with Stage 3 or Stage 4 CKD and resistant hypertension, with no radiological or laboratory evidence of secondary causes of hypertension.

Measurements:

The key measurements were CBP, pulse wave velocity, ambulatory 24-hour blood pressure, office blood pressures on BP Tru, GFR, 24-hour urine protein and sodium, dose and number of blood pressure medication and doses.

Methods:

The primary outcome measure was the change in CBP from baseline to 6 months post-RDN. Secondary outcome measures included changes in CBP, office blood pressure, 24-hour ambulatory pressures, pulse wave velocity, kidney function (eGFR and 24-hour protein excretion), and the change in the number and dose of medications during the 2-year follow-up period. The primary outcome and the secondary outcomes were evaluated using a Friedman’s analysis of variance (ANOVA) and Wilcoxon signed-rank test for changes from post RDN procedure. Bonferroni correction was used to adjust P values for multiple testing. A two-sided alpha of .05 was used.

Results:

Median central blood pressures (mm Hg) were 127/75 at baseline versus 118/70 at 6 months and 118/67 at 24 months (P = .13). Median office blood pressures (mm Hg) were 148/76 at baseline versus 135/75 at 6 months and 133/75 at 24 months (P ≤ .001). Median ambulatory 24-hour day (mm Hg) was 148/64 at baseline and 146/68 at 6 months and 152/67 at 24 months (P = .60). Median pulse wave velocity (m/s) at baseline was 13.8 at baseline versus 13.3 m/s at 6 months and 12.3 at 12 months’ time (P = .62). Estimated glomerular filtration rate (mL/min/1.73m²) at baseline was 37, at 6 months was 36 and 34 at 24 months (P = .33).

Limitations:

Single-center study, with no sham arm.

Conclusions:

Our study demonstrates that there was a significant improvement in office blood pressures from baseline to 6 months, maintained to 24 months. There was a numerical improvement in central pressures, and pulse wave velocity at 6 and 24 months, with no sustained changes noted in 24-hour blood pressure. Kidney function remained at or near baseline throughout the 24 months of observation.

Trial registration:

ClinicalTrials.gov (NCT01832233).

The Impact on Central Blood Pressure and Arterial Stiffness Post Renal Denervation in Patients With Stage 3 and 4 Chronic Kidney Disease: The Prairie Renal Denervation Study

Background:

Central aortic blood pressures and arterial stiffness are better indicators of cardiovascular outcomes than brachial blood pressures. However, their response to renal denervation (RDN) in patients with stage 3 and stage 4 chronic kidney disease (CKD) has not yet been examined.

Objective:

To evaluate the impact of RDN on central blood pressures, brachial (office and ambulatory) blood pressures, arterial stiffness, glomerular filtration rate (GFR), 24-hour urine protein, and selective cardiac parameters observed on echocardiograms.

Design:

Single-center, single-arm with pre-RDN/post-RDN follow-up.

Setting:

Patients are being recruited from the multidisciplinary CKD clinic.

Patients:

Fifty consecutive patients with stage 3 or stage 4 CKD and resistant hypertension, with no radiological or laboratory evidence of secondary causes of hypertension.

Measurements:

The key measurements are central blood pressures, pulse wave velocity, ambulatory 24-hour blood pressure, office blood pressures on BP Tru, GFR, 24-hour urine protein and sodium, blood pressure medication, and doses.

Methods:

For our primary outcome, we will compare changes in central blood pressures from baseline to 6 months post RDN using a paired t test or Mann-Whitney U test. Secondary outcomes will examine changes in central blood pressures from baseline to 3, 12, 18, and 24 months post RDN as well as changes in office pressures, GFR, 24-hour urine protein and sodium, and medications at all time points using mixed-model analyses of variance or Friedman test. Multiple regression may be used to control for potential covariates.

Limitations:

Single-center study, with no sham arm.

Conclusions:

Aortic blood pressure, rather than brachial blood pressure, optimally reflects the load placed on the left ventricle. Aortic blood pressure is also better associated with cardiovascular outcomes. If our study shows a preferential decrease in central blood pressures and improvements in cardiac parameters on echocardiograms post RDN, this may influence the way in which blood pressures are managed in clinics and offices.

Trial Registration:

ClinicalTrials.gov (NCT01832233)

Chronic kidney disease impairs renal nerve and haemodynamic reflex responses to vagal afferent input through a central mechanism

We investigated age- and sex-related changes in reflex renal sympathetic nerve activity (RSNA) and haemodynamic responses to vagal afferent stimulation in a rodent model of chronic kidney disease (CKD). Using anaesthetised juvenile (7-8weeks) and adult (12-13weeks) Lewis Polycystic Kidney (LPK) and Lewis control rats of either sex (n=63 total), reflex changes in RSNA, heart rate (HR) and mean arterial pressure (MAP) to vagal afferent stimulation (5-s train, 4.0V, 2.0-ms pulses, 1-16Hz) were measured. In all groups, stimulation of the vagal afferents below 16Hz produced frequency-dependent reductions in RSNA, HR and MAP, while a 16Hz stimulus produced an initial sympathoinhibition followed by sympathoexcitation. In juvenile LPK versus age-matched Lewis, sympathoinhibition was reduced when responses were expressed as % baseline (P<0.05), but not as microvolts, while bradycardic responses were greater. Reflex depressor responses were greater (P=0.015) only in juvenile female LPK. In adult LPK, reflex sympathoinhibition (%) was blunted (P<0.05), and an age-related decline apparent (when expressed as microvolts). Reflex reductions in HR and MAP were only diminished (P<0.05) in adult female LPK versus age-matched Lewis. Peak reflex sympathoexcitation at 16Hz did not differ between groups; however, area under the curve values were greater in the LPK versus Lewis (overall, 9±1 versus 19±3μVs, P<0.05) irrespective of age, suggestive of enhanced sympathoexcitatory drive in the LPK. Our data demonstrates a progressive deficit in the central processing of vagal afferent input and a differential sex influence on reflex regulation of autonomic function and blood pressure homeostasis in CKD.

Chronic Kidney Disease As a Potential Indication for Renal Denervation

Renal denervation is being used as a blood pressure lowering therapy for patients with apparent treatment resistant hypertension. However, this population does not represent a distinct disease condition in which benefit is predictable. In fact, the wide range in effectiveness of renal denervation could be a consequence of this heterogeneous pathogenesis of hypertension. Since renal denervation aims at disrupting sympathetic nerves surrounding the renal arteries, it seems obvious to focus on patients with increased afferent and/or efferent renal sympathetic nerve activity. In this review will be argued, from both a pathophysiological and a clinical point of view, that chronic kidney disease is particularly suited to renal denervation.