Renal sympathetic denervation: a novel intervention for resistant hypertension, insulin resistance, and sleep apnea

Endovascular Denervation for the Improvement of Limb Ischemia in Patients with Peripheral Artery Disease: A Randomized Clinical Trial

BACKGROUND

To evaluate the safety and efficacy of endovascular denervation (EDN) as an adjunct to percutaneous vascular intervention (PVI) for peripheral artery disease (PAD).

METHODS

From August 2019 to April 2021, 38 eligible patients with PAD enrolled in this study were randomly and equally assigned into 2 groups: the PVI group and the PVI + EDN group treated with EDN at the iliac and femoral arteries before PVI. The primary endpoint was the improvement in the ankle brachial index at 6 months after the procedure. The secondary endpoints were transcutaneous oxygen pressure (TcPO2), Rutherford category, numerical rating scale score, and safety.

RESULTS

The technical success rates of PVI and EDN were 100%, and no device-related or procedure-related major adverse events occurred in either group. Compared with PVI alone, PVI + EDN demonstrated a significant improvement in limb hemodynamics at 6 months (Δ ankle brachial index 0.44 ± 0.31 vs. 0.24 ± 0.15, P = 0.018). Microcirculatory perfusion of PAD was significantly better at 6 months in the PVI + EDN group (ΔTcPO2, 15.68 ± 16.72 vs. 4.95 ± 13.43, P = 0.036). The Rutherford category was significantly improved in the PVI + EDN group in comparison with the PVI group at the 3-month follow-up (100.00% vs. 68.42%, P = 0.02). The decrease in the numerical rating scale score in the PVI + EDN group was greater than that in the PVI group at 1 week following the procedure (3 [2-5] vs. 4 [4-6], P = 0.022).

CONCLUSIONS

In this single-center pilot analysis of a heterogeneous cohort of patients with PAD, PVI with EDN demonstrated a significant improvement in limb ischemia at 6 months compared with PVI alone.

Renal Innervation in Resistant Hypertension: A Review of Pathophysiology and Renal Denervation as Potential Treatment

Background

Advances in treatment and increased awareness have improved the prognosis for many patients with hypertension (HTN). Resistant hypertension (RH) refers to a subset of hypertensive individuals who fail to achieve a desired blood pressure (BP) despite concurrent use of 3 different classes antihypertensive agents, one being a diuretic, and proper lifestyle changes. The prevalence and prognosis of RH are unclear owing to its heterogeneous etiologies, risk factors, and secondary comorbidities. Previous research has provided evidence that increased renal sympathetic nerve activity (RSNA) within the renal artery contributes to RH development. Renal denervation (RDN) is a procedure that attempts to ameliorate the effects of heightened RSNA via ablation renal sympathetic fibers. BP reductions associated with RDN may be attributed to decreased norepinephrine spillover, restoration of natriuresis, increasing renal blood flow, and lowering plasma renin activity. Early clinical trials perpetuated positive results, and enthusiasm grew exponentially. However, recent clinical trials have called into question RDN's efficacy. Numerous limitations must be addressed to discern the true effectiveness of RDN as a therapeutic option for RH.

Objective

We aimed to review the current understanding of RH, the anatomy of renal arteries, physiology of RH on renal arteries, anatomical pathways of the sympathetic involved in RH, RDN as a treatment option, and all relevant clinical trials treating RH with RDN.

Methods

We piloted a MEDLINE^® database search of literature extending from 1980 to 2017, with emphasis on the previous five years, combining keywords such as “resistant hypertension” and 
“renal denervation.”

Conclusion

A plethora of information is available regarding heightened RSNA leading to RH. RDN as a possible treatment option has shown a range of results. Reconciling RDN's true efficacy requires future trials to increased sites of nerve ablation, standardized protocol, increased anatomical understanding per individual basis, stricter guidelines regarding study design, increased operator experience, and integrating the use of a multielectrode catheter.

Effect of Peripheral Artery Sympathetic Denervation on Muscle Microperfusion and Macroperfusion in an Animal Peripheral Artery Disease Model Using Contrast-Enhanced Ultrasound and Doppler Flow Measurement

PURPOSE

To determine the effects of catheter-based peripheral sympathetic denervation (CPSD) on peripheral artery sympathetic tone and peripheral microperfusion (PMP).

MATERIALS AND METHODS

The effects of bilateral CPSD in common iliac arteries on PMP of the biceps femoris were determined in pigs using contrast-enhanced ultrasound, and mean transit time (mTT) and wash-in rate (WiR) were calculated during steady-state infusion of INN-sulfur-hexafluoride. Measurements were performed bilaterally at rest and during infusion of adenosine 70 μg/kg/min after unilateral moderate left external iliac artery stenosis.

RESULTS

Before CPSD, PMP decreased significantly (P < .05) under adenosine stress compared with resting conditions, with right mTT of 7.5 seconds ± 3.6 versus 16.9 seconds ± 11.9 and WiR of 63.1 arbitrary units (AU) ± 49.0 versus 25.0 AU ± 17.5 and left mTT of 29.2 seconds ± 18.0 versus 56.3 seconds ± 38.7 and WiR of 13.6 AU ± 8.4 versus 6.0 AU ± 4.1. After CPSD, PMP did not differ significantly (P > .05) between conditions of adenosine stress and rest, with right mTT of 19.9 seconds ± 24.7 versus 23.2 seconds ± 21.0 and WiR of 16.2 AU ± 25.0 versus 20.5 AU ± 19.7 and left mTT of 23.3 seconds ± 23.1 versus 25.8 seconds ± 21.7 and WiR of 12.5 AU ± 6.2 versus 20.0 AU ± 12.1.

CONCLUSIONS

CPSD reduced peripheral artery sympathetic tone and may be an alternative to surgical or computed tomography-guided sympathectomy for the treatment of end-stage peripheral artery disease and Raynaud phenomenon.

Renal sympathetic denervation in the treatment of resistant hypertension

Arterial hypertension (HTN) is a major health problem worldwide. Treatment-resistant hypertension (trHTN) is defined as the failure to achieve target blood pressure despite the concomitant use of maximally tolerated doses of three different antihypertensive medications, including a diuretic. trHTN is associated with considerable morbidity and mortality. Renal sympathetic denervation (RDn) is available and implemented abroad as a strategy for the treatment of trHTN and is currently under clinical investigation in the United States. Selective renal sympathectomy via an endovascular approach effectively decreases renal sympathetic nerve hyperactivity leading to a decrease in blood pressure. The Symplicity catheter, currently under investigation in the United States, is a 6-French compatible system advanced under fluoroscopic guidance via percutaneous access of the common femoral artery to the distal lumen of each of the main renal arteries. Radiofrequency (RF) energy is then applied to the endoluminal surface of the renal arteries via an electrode located at the tip of the catheter. Two clinical trials (Symplicity HTN 1 and Symplicity HTN 2) have shown the efficacy of RDn with a post-procedure decline of 27/17 mmHg at 12 months and 32/12 mmHg at 6 months, respectively, with few minor adverse events. Symplicity HTN-3 study is a, multi-center, prospective, single-blind, randomized, controlled study currently under way and will provide further insights about the safety and efficacy of renal denervation in patients with trHTN.

Renal denervation: a new treatment option in resistant arterial hypertension

Hypertension is one of the most prevalent cardiovascular risk factors. Despite this high prevalence and a broad availability of effective pharmaceutical agents, a significant proportion of patients do not reach treatment goals. Partly this can be explained by secondary causes of hypertension or non-compliance of patients. Nevertheless, a subgroup of patients can be diagnosed with 'resistant hypertension'. Activation of the sympathetic nervous system is known to be an important factor in the development and progression of systemic hypertension. In this context, a percutaneous, catheter-based approach has been developed using radiofrequency energy to disrupt renal sympathetic nerves. The first studies have shown this technique to be safe, illustrated by a lack of vascular or renal injury. More importantly, catheter-based renal nerve ablation resulted in a significant reduction in blood pressure on top of traditional medical therapy. Additional to the encouraging effects shown on hypertension, a positive influence of this intervention in other conditions, characterised by sympathetic overactivation, may be expected. Though this technique seems promising, further studies are needed to address long-term safety and efficacy of renal denervation in hypertension and other disease states.

Percutaneous revascularization for ischemic nephropathy: the past, present, and future

Occlusion of the renal arteries can threaten the viability of the kidney when severe, in addition to accelerating hypertension and circulatory congestion. Renal artery stenting procedures have evolved from a treatment mainly for renovascular hypertension to a maneuver capable of recovering threatened renal function in patients with “ischemic nephropathy” and improving management of congestive heart failure. Improved catheter design and techniques have reduced, but not eliminated hazards associated with renovascular stenting. Expanded use of endovascular stent grafts to treat abdominal aortic aneurysms has introduced a new indication for renal artery stenting to protect the renal circulation when grafts cross the origins of the renal arteries. Although controversial, prospective randomized trials to evaluate the added benefit of revascularization to current medical therapy for atherosclerotic renal artery stenosis until now have failed to identify major benefits regarding either renal function or blood pressure control. These studies have been limited by selection bias and have been harshly criticized. While studies of tissue oxygenation using blood oxygen level dependent (BOLD) MR establish that kidneys can adapt to reduced blood flow to some degree, more severe occlusive disease leads to cortical hypoxia associated with microvascular rarefication, inflammatory injury and fibrosis. Current research is directed toward identifying pathways of irreversible kidney injury due to vascular occlusion and to increase the potential for renal repair after restoring renal artery patency. The role of nephrologists likely will focus upon recognizing the limits of renal adaptation to vascular disease and identifying kidneys truly at risk for ischemic injury at a time point when renal revascularization can still be of benefit to recovering kidney function.

Renal denervation for treatment-resistant hypertension

Hypertension is a major public health concern that is increasing in prevalence. Lifestyle and pharmacological management are not always sufficient to control blood pressure and treatment-resistant hypertension is a recognized clinical challenge. Renal sympathetic denervation (RSD) represents a new frontier in the treatment of resistant hypertension.

RESULTS

from the Symplicity HTN-1 and HTN-2 trials have demonstrated evidence that suggests RSD can safely reduce blood pressure in patients with this condition. More research is needed to verify these data, clarify unanswered questions and assess future applications of RSD. This review provides a detailed overview on the history of hypertension, treatment-resistant hypertension, the rationale behind RSD, current evidence and potential future applications of RSD. An overview of current and upcoming RSD devices is also included.

Overview of resistant hypertension: A glimpse of the cardiologist's current standpoint

Hypertension is a major risk factor for cardiovascular disease, resulting in increased incidence of cerebrovascular events, ischaemic heart disease, heart failure, and renal impairment. Thus, it is one of the most important preventable causes of premature morbidity and mortality. Despite current knowledge on the management of hypertension and the availability of several effective antihypertensive medications, uncontrolled hypertension remains a common and challenging clinical problem. Resistant hypertension is a complex condition with multiple contributing factors and overlapping comorbidities. Although there is limited hard evidence regarding resistant hypertension, our understanding of this condition has improved recently. This article will present an overview of resistant hypertension and highlight recent publications about this topic.

Renal Sympathetic Denervation for Treatment of Hypertension

OPINION STATEMENT: Sympathetic nervous system activation of the heart, kidney and peripheral vasculature increases cardiac output, fluid retention and vascular resistance and plays an important role in acute and chronic BP elevation. Renal sympathetic denervation via a percutaneous radiofrequency catheter based approach is a safe and effective procedure that lowers BP in patients with resistant hypertension. Exploratory studies in patients with resistant hypertension and a variety of comorbidities, including insulin resistance/metabolic syndrome, obstructive sleep apnea and the polycystic ovary syndrome, have shown benefit of renal denervation in attenuating the severity of the comorbid conditions, as well as reducing BP. However, more studies are needed to further address the long term effects of renal denervation and its safety and effectiveness in other disease states such as congestive heart failure.