Sympathetic activation secondary to chronic kidney disease: therapeutic target for renal denervation?

The feasibility, efficacy, and safety of RDN procedure using CO2 angiography through radial artery in severe chronic kidney disease patients

The recent evidence regarding the effectiveness of renal denervation (RDN) in blood pressure control is becoming increasingly substantial. However, many studies have excluded populations with severely impaired kidney function, even though these individuals have a higher prevalence of hypertension compared to the general population, and controlling their blood pressure is more challenging. The effectiveness and safety of RDN in patients with severe chronic kidney disease (CKD) lack strong evidence support. Concerns about worsening kidney function still exist, particularly in patients with CKD stage 5. We conducted an observational study involving 10 patients who were using at least 3 different antihypertensive medications and had an estimated glomerular filtration rate (eGFR) < 45 mL/min/1.73 m2 but had not undergone dialysis. For these patients, we performed RDN via the radial artery approach, with the assistance of carbon dioxide (CO2) angiography. Utilizing this approach, the systolic 24-hour ambulatory blood pressure monitoring did not exhibit a significant decrease at 3 months; however, a significant reduction was observed at 6 months after RDN. We also minimized contrast agent usage, observed no kidney function decline 3 months post-RDN, and experienced no vascular-related complications. Using the radial artery approach and CO2 angiography assistance for RDN may be an effective and safe blood pressure control method for patients with severe kidney impairment.

Does Renal Denervation a Reasonable Treatment Option in Hemodialysis-Dependent Patient with Resistant Hypertension? A Narrative Review

PURPOSE OF REVIEW

This narrative review aims to assess the pathophysiology, diagnosis, and treatment of resistant hypertension (RH) in end-stage kidney disease (ESKD) patients on dialysis, with a specific focus on the effect of renal denervation (RDN) on short-term and long-term blood pressure (BP) control. Additionally, we share our experience with the use of RDN in an amyloidotic patient undergoing hemodialysis with RH.

RECENT FINDINGS

High BP, an important modifiable cardiovascular risk factor, is often observed in patients in ESKD, despite the administration of multiple antihypertensive medications. However, in clinical practice, it remains challenging to identify RH patients on dialysis treatment because of the absence of specific definition for RH in this context. Moreover, the use of invasive approaches, such as RDN, to treat RH is limited by the exclusion of patients with reduced renal function (eGFR < 45 mL/min/1.73 m3) in the clinical trials. Nevertheless, recent studies have reported encouraging results regarding the effectiveness of RDN in stage 3 and 4 chronic kidney disease (CKD) and ESKD patients on dialysis, with reductions in BP of nearly up to 10 mmhg. Although multiple underlying pathophysiological mechanisms contribute to RH, the overactivation of the sympathetic nervous system in ESKD patients on dialysis plays a crucial role. The diagnosis of RH requires both confirmation of adherence to antihypertensive therapy and the presence of uncontrolled BP values by ambulatory BP monitoring or home BP monitoring. Treatment involves a combination of nonpharmacological approaches (such as dry weight reduction, sodium restriction, dialysate sodium concentration reduction, and exercise) and pharmacological treatments. A promising approach for managing of RH is based on catheter-based RDN, through radiofrequency, ultrasound, or alcohol infusion, directly targeting on sympathetic overactivity.

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.

Autonomic cardiovascular alterations as therapeutic targets in chronic kidney disease

Purpose

The present paper will review the impact of different therapeutic interventions on the autonomic dysfunction characterizing chronic renal failure.

Methods

We reviewed the results of the studies carried out in the last few years examining the effects of standard pharmacologic treatment, hemodialysis, kidney transplantation, renal nerve ablation and carotid baroreceptor stimulation on parasympathetic and sympathetic control of the cardiovascular system in patients with renal failure.

Results

Drugs acting on the renin–angiotensin system as well as central sympatholytic agents have been documented to improve autonomic cardiovascular control. This has also been shown for hemodialysis, although with more heterogeneous results related to the type of dialytic procedure adopted. Kidney transplantation, in contrast, particularly when performed together with the surgical removal of the native diseased kidneys, has been shown to cause profound sympathoinhibitory effects. Finally, a small amount of promising data are available on the potential favorable autonomic effects (particularly the sympathetic ones) of renal nerve ablation and carotid baroreceptor stimulation in chronic kidney disease.

Conclusions

Further studies are needed to clarify several aspects of the autonomic responses to therapeutic interventions in chronic renal disease. These include (1) the potential to normalize sympathetic activity in uremic patients by the various therapeutic approaches and (2) the definition of the degree of sympathetic deactivation to be achieved during treatment.

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.

Reduced Renal Mass, Salt-Sensitive Hypertension Is Resistant to Renal Denervation

Aim: Activation of the sympathetic nervous system is common in resistant hypertension (RHT) and also in chronic kidney disease (CKD), a prevalent condition among resistant hypertensives. However, renal nerve ablation lowers blood pressure (BP) only in some patients with RHT. The influence of loss of nephrons per se on the antihypertensive response to renal denervation (RDNx) is unclear and was the focus of this study.

Methods: Systemic hemodynamics and sympathetically mediated low frequency oscillations of systolic BP were determined continuously from telemetrically acquired BP recordings in rats before and after surgical excision of ∼80% of renal mass and subsequent RDNx.

Results: After reduction of renal mass, rats fed a high salt (HS) diet showed sustained increases in mean arterial pressure (108 ± 3 mmHg to 128 ± 2 mmHg) and suppression of estimated sympathetic activity (∼15%), responses that did not occur with HS before renal ablation. After denervation of the remnant kidney, arterial pressure fell (to 104 ± 4 mmHg), estimated sympathetic activity and heart rate (HR) increased concomitantly, but these changes gradually returned to pre-denervation levels over 2 weeks of follow up. Subsequently, sympathoinhibition with clonidine did not alter arterial pressure while significantly suppressing estimated sympathetic activity and HR.

Conclusion: These results indicate that RDNx does not chronically lower arterial pressure in this model of salt-sensitive hypertension associated with substantial nephron loss, but without ischemia and increased sympathetic activity, thus providing further insight into conditions likely to impact the antihypertensive response to renal-specific sympathoinhibition in subjects with CKD.

Acute, repetitive and chronic Takotsubo syndrome in patients with chronic kidney disease: Sympathetic reno-cardial syndrome

Heart failure and cardiovascular death are common in patients with chronic kidney disease (CKD) and extremely prevalent in patients undergoing dialysis. It has been shown that the excess of cardiovascular mortality in this patient population is not fully accounted for by the traditional cardiovascular risk factors. Substantial evidence exists for the presence of sympathetic over-activity in patients with dialytic and non-dialytic CKD. Several studies have also been reported on reversible segmental left ventricular wall motion abnormality consistent with myocardial stunning in association with dialysis especially hemodialysis. In the literature, the most acceptable underpinning hypothesis for the myocardial stunning in CKD is "demand myocardial ischemia". However, the occurrence of cardiac sympathetic over-activation-disruption and repeated reversible myocardial stunning in patients with CKD can be compared to that occurring in acute Takotsubo syndrome where local cardiac sympathetic disruption may cause acute regional circumferential pattern of myocardial stunning. In this manuscript, converging evidences suggestive for the fact that acute, repetitive, and chronic TS may be one of the important causes of cardiac morbidity including myocardial stunning and heart failure and mortality in patients with CKD are provided.

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.

Connecting heart failure with preserved ejection fraction and renal dysfunction: the role of endothelial dysfunction and inflammation

Renal dysfunction in heart failure with preserved ejection fraction (HFpEF) is common and is associated with increased mortality. Impaired renal function is also a risk factor for developing HFpEF. A new paradigm for HFpEF, proposing a sequence of events leading to myocardial remodelling and dysfunction in HFpEF, was recently introduced, involving inflammatory, microvascular, and cardiac components. The kidney might play a key role in this systemic process. Renal impairment causes metabolic and systemic derangements in circulating factors, causing an activated systemic inflammatory state and endothelial dysfunction, which may lead to cardiomyocyte stiffening, hypertrophy, and interstitial fibrosis via cross-talk between the endothelium and cardiomyocyte compartments. Here, we review the role of endothelial dysfunction and inflammation to explain the link between renal dysfunction and HFpEF, which allows for identification of new early risk markers, prognostic factors, and unique targets for intervention.

Fibroblast growth factor 23 and sudden versus non-sudden cardiac death: the Cardiovascular Health Study

BACKGROUND

Elevated fibroblast growth factor 23 (FGF-23) concentrations are associated with greater risk of cardiovascular events and mortality, especially among people with chronic kidney disease (CKD). Because individuals with CKD are at an increased risk of sudden cardiac death (SCD), we sought to understand whether FGF-23 level is a stronger risk factor for SCD versus non-SCD.

STUDY DESIGN

Cohort study.

SETTING & PARTICIPANTS

3,244 participants 65 years or older in the community-based Cardiovascular Health Study.

PREDICTOR

Plasma FGF-23 concentrations.

OUTCOMES

We assessed SCD and non-SCD in these analyses. SCD was adjudicated rigorously and was defined as a sudden pulseless condition of cardiac origin in a previously stable person occurring out of hospital or in the emergency department.

MEASUREMENTS

We estimated associations of baseline FGF-23 concentrations with SCD and non-SCD using Cox proportional hazards models after adjustment for demographics, cardiovascular risk factors, comorbid conditions, and kidney function. We also tested whether associations differed by CKD status.

RESULTS

During a median follow-up of 8.1 years, there were 118 adjudicated SCD and 570 non-SCD events. After multivariable adjustment for demographics, cardiovascular risk factors, comorbid conditions, and parameters of kidney function, higher FGF-23 concentrations were an independent risk factor for non-SCD (HR [per doubling], 1.17; 95% CI, 1.06-1.30). However, elevated FGF-23 concentrations were not associated independently with SCD (HR [per doubling], 1.07; 95% CI, 0.85-1.35). In stratified analysis by CKD status (36.5% of cohort), doubling of FGF-23 concentrations was associated independently with non-SCD (adjusted HR, 1.26; 95% CI, 1.10-1.45). A similar magnitude of association was observed between FGF-23 level and SCD in the CKD subgroup; however, it was not significant (HR, 1.20; 95% CI, 0.89-1.62).

LIMITATIONS

Limited power to detect moderate-sized effects between FGF-23 level and SCD in both the primary and stratified analyses.

CONCLUSIONS

In this population-based study, FGF-23 level elevations were associated independently with non-SCD. Among individuals with CKD, the associations between FGF-23 level and SCD and non-SCD were similar.

Renal denervation of the native kidneys for drug-resistant hypertension after kidney transplantation

There is a strong rationale for renal denervation (RDN) of the native kidneys in kidney transplant recipients with treatment-resistant hypertension. We present a patient with a stable graft function, who underwent RDN for posttransplant therapy-resistant hypertension (24-h ambulatory blood pressure measurement (ABPM) 143/89 mmHg, while compliantly using five different antihypertensive agents). After RDN, BP measurements and orthostatic complaints required withdrawal of two antihypertensive agents and halving a third. At 6 months, ABPM was 134/84 mmHg and allograft function remained unchanged. This case calls for designing well-designed prospective studies on RDN in kidney transplant recipients.