Sympathectomy for hypertension; follow-up of 212 patients

Rethinking Resistant Hypertension

Resistant hypertension is common and known to be a risk factor for cardiovascular events, including stroke, myocardial infarction, heart failure, and cardiovascular mortality, as well as adverse renal events, including chronic kidney disease and end-stage kidney disease. This review will discuss the definition of resistant hypertension as well as the most recent evidence regarding its diagnosis, evaluation, and management. The issue of medication non-adherence and its association with apparent treatment-resistant hypertension will be addressed. Non-pharmacological interventions for the treatment of resistant hypertension will be reviewed. Particular emphasis will be placed on pharmacological interventions, highlighting the role of mineralocorticoid receptor antagonists and sodium-glucose cotransporter-2 inhibitors and device therapy, including renal denervation, baroreceptor activation or modulation, and central arteriovenous fistula creation.

Successful treatment of refractory hypertension with bilateral nephrectomy in a patient with chronic kidney disease stage 3

We present a case of life-threatening refractory hypertension (rHTN) in a patient with stage 3b chronic kidney disease that was unresponsive to open surgical renal denervation (RDN) but responded to bilateral nephrectomy (BLN). Both RDN and BLN reduce the increased sympathetic activation in rHTN. However, RDN has yet to show reductions in blood pressure adequate for the average patient with rHTN, and BLN has thus far been reserved for patients with preexisting end-stage kidney disease (ESKD). Our case suggests that there are patients with rHTN that warrant consideration of BLN prior to developing ESKD.

Rodent models of hypertension

Elevated blood pressure (BP), or hypertension, is the main risk factor for cardiovascular disease. As a multifactorial and systemic disease that involves multiple organs and systems, hypertension remains a challenging disease to study. Models of hypertension are invaluable to support the discovery of the specific genetic, cellular and molecular mechanisms underlying essential hypertension, as well as to test new possible treatments to lower BP. Rodent models have proven to be an invaluable tool for advancing the field. In this review, we discuss the strengths and weaknesses of rodent models of hypertension through a systems approach. We highlight the ways how target organs and systems including the kidneys, vasculature, the sympathetic nervous system (SNS), immune system and the gut microbiota influence BP in each rodent model. We also discuss often overlooked hypertensive conditions such as pulmonary hypertension and hypertensive-pregnancy disorders, providing an important resource for researchers.

Developing a Computational Model of Renal Nerves and Surgical System for Laparoscopic Renal Denervation

The sympathetic nervous system was known to play an important role in resistant hypertension. Surgical sympathectomy for renal sympathetic nerve removal were performed since the 1930s. Although effective, it had many serious side effects and complications due to non-selective property. Recently, catheter based RDN system using radiofrequency (RF) ablation was developed and considered promising, however, it failed in sham controlled trial. Therefore, there are needs for safe and effective RDN strategies considering the anatomical structure of the renal arteries and sympathetic nerves. In this paper, we propose a novel surgical instruments for laparoscopic renal denervation (RDN) to treat of resistant hypertension through a 3D realistic model using nephrectomy tissues. Laparoscopic RDN is a new surgical approach to remove renal sympathetic nerves.

Design and simulation of novel laparoscopic renal denervation system: a feasibility study

PURPOSE

In this study, we propose a novel laparoscopy-based renal denervation (RDN) system for treating patients with resistant hypertension. In this feasibility study, we investigated whether our proposed surgical instrument can ablate renal nerves from outside of the renal artery safely and effectively and can overcome the depth-related limitations of the previous catheter-based system with less damage to the arterial walls.

METHOD

We designed a looped bipolar electrosurgical instrument to be used with laparoscopy-based RDN system. The tip of instrument wraps around the renal artery and delivers the radio-frequency (RF) energy. We evaluated the thermal distribution via simulation study on a numerical model designed using histological data and validated the results by the in vitro study. Finally, to show the effectiveness of this system, we compared the performance of our system with that of catheter-based RDN system through simulations.

RESULTS

Simulation results were within the 95% confidence intervals of the in vitro experimental results. The validated results demonstrated that the proposed laparoscopy-based RDN system produces an effective thermal distribution for the removal of renal sympathetic nerves without damaging the arterial wall and addresses the depth limitation of catheter-based RDN system.

CONCLUSIONS

We developed a novel laparoscope-based electrosurgical RDN method for hypertension treatment. The feasibility of our system was confirmed through a simulation study as well as in vitro experiments. Our proposed method could be an effective treatment for resistant hypertension as well as central nervous system diseases.

Reduction of Blood Pressure Following After Renal Artery Adventitia Stripping During Total Nephroureterectomy: Potential Effect of Renal Sympathetic Denervation

Case series

Patients: Male, 85 • Male, 89

Final Diagnosis: Essential hypertension

Symptoms: High blood pressure

Medication: Anti-hypertensive agents

Clinical Procedure: Operation

Specialty: Cardiology and Hypertension

Catheter-Based Renal Denervation for Resistant Hypertension: Will It Ever Be Ready for "Prime Time"?

The year 2014 was a turning point for the field of renal denervation (RDN) and its potential use to treat resistant hypertension. Tremendous enthusiasm shifted to sober reflection on the efficacy of a technology once touted as the cure to resistant hypertension. The following review highlights 2 major questions: First, does catheter-based RDN lower blood pressure and, second, will RDN using catheter-directed therapy for the treatment of resistant hypertension ever become more than an investigational technology.

Renal denervation for human hypertension: is there a future?

The sympathetic nervous system plays a permissive, if not primary causal role in the genesis and maintenance of human essential hypertension. Excessive sympathetic nervous system activity in man is most apparent in early forms of hypertension (prehypertension and white-coat type). Renal nerves are of particular interest because of their roles in modulating the activity of the renin-angiotensin system and renal sodium excretion. Renal denervation substantially ameliorates the development of hypertension in animal models such as renovascular, spontaneously hypertensive, and steroid-induced hypertension in rats and aortic coarctation in dogs. In man, catheter ablation of renal nerves has been undertaken in the late phases of hypertension; in a rigorously controlled trial in resistant hypertension (SYMPLICITY HTN-3), renal denervation did not reduce blood pressure over the long term. Is this because renal denervation is more appropriate to prevent than treat late-stage hypertension? Are there anatomical or technical barriers yet to be overcome in the procedure? These and other issues are addressed by two experts in this issue of the controversies series: Deepak L. Bhatt and Murray Epstein.

The rise, fall, and possible resurrection of renal denervation

Renal denervation has a chequered history. Dramatic reductions in blood pressure after denervation of the renal arteries were observed in early trials, but later trials in which denervation was tested against a sham procedure produced neutral results. Although a sound pathophysiological basis exists for interruption of the renal sympathetic nervous system as a treatment for hypertension, trial data to date are insufficient to support renal denervation as an established clinical therapy. In this Perspectives article, we summarize the currently available trial data, device development, and trials in progress, and provide recommendations for future trial design.

Renal Sympathetic Denervation by CT-Guided Ethanol Injection: A Phase II Pilot Trial of a Novel Technique

OBJECTIVES

CT-guided ethanol-mediated renal sympathetic denervation in treatment of therapy-resistant hypertension was performed to assess patient safety and collect preliminary data on treatment efficacy.

MATERIALS AND METHODS

Eleven patients with therapy-resistant hypertension (blood pressure of >160 mmHg despite three different antihypertensive drugs including a diuretic) and following screening for secondary causes were enrolled in a phase II single arm open label pilot trial of CT-guided neurolysis of sympathetic renal innervation. Primary endpoint was safety, and secondary endpoint was a decrease of the mean office as well as 24-h systolic blood pressure in follow-up. Follow-up visits at 4 weeks, 3, and 6 months included 24-h blood pressure assessments, office blood pressure, laboratory values, as well as full clinical and quality of life assessments.

RESULTS

No toxicities ≥3° occurred. Three patients exhibited worsened kidney function in follow-up analyses. When accounting all patients, office systolic blood pressure decreased significantly at all follow-up visits (maximal mean decrease -41.2 mmHg at 3 months). The mean 24-h systolic blood pressure values decreased significantly at 3 months, but not at 6 months (mean: -9.7 and -6.3 mmHg, respectively). Exclusion of five patients who had failed catheter-based endovascular denervation and/or were incompliant for antihypertensive drug intake revealed a more pronounced decrease of 24-h systolic blood pressure (mean: -18.3 and -15.2 mmHg at 3 and 6 months, p = 0.03 and 0.06).

CONCLUSION

CT-guided sympathetic denervation proved to be safe and applicable under various anatomical conditions with more renal arteries and such of small diameter.

Renal denervation for resistant hypertension and beyond

Despite the availability of more than 125 approved antihypertensive medications, 36 million (48%) of 75 million people with hypertension, including 16 million treated with antihypertensive medications in the United States, do not achieve guideline blood pressure goals known to reduce cardiovascular morbidity and mortality and progression of kidney disease; 3% to 6% of these 75 million hypertensive individuals are estimated to have resistant hypertension. A major contributing factor for poor blood pressure control, besides inadequate diuretic therapy, is failure of antihypertensive agents to inhibit the sympathetic nervous system effectively. Consequently, alternative device-driven approaches have been developed. Recent technical advances targeting renal sympathetic nerves, that is, renal denervation therapy, are the focus of more invasive therapies to treat resistant hypertension. Encouraging results from the SYMPLICITY HTN-2 trial, regarding efficacy and safety of renal denervation therapy, were countered by disappointing efficacy results of SYMPLICITY HTN-3. Reasons for these divergent results and the future of the field are discussed.

Renal denervation: potential indications and review of trial data

Renal sympathetic denervation is a novel, endovascular treatment with potential utility in resistant hypertension. First pioneered in humans in 2010, conflicting data exist regarding the efficacy of this treatment. This article will review the evidence to date, the scientific rationale for sympathetic denervation as a treatment for hypertension and consider other possible conditions where the therapy may be of benefit.

Renal sympathetic denervation for the treatment of refractory hypertension

Resistant hypertension poses significant health concerns. There are strong demands for new and safe therapies to control resistant hypertension while addressing its common causes, specifically poor compliance to lifelong polypharmacy, lifestyle modifications, and physician inertia. The sympathetic nervous system plays a significant pathophysiological role in hypertension. Surgical sympathectomy for blood pressure reduction is an old but extremely efficacious therapeutic concept, now abandoned with the dawn of a safer contemporary pharmacology era. Recently, clinical studies have revealed promising results for safe and sustained blood pressure reduction with percutaneous renal sympathetic denervation. This is a novel, minimally invasive, device-based therapy, specifically targeting and ablating the renal artery nerves with radiofrequency waves without permanent implantation. There are also reported additional benefits in related comorbidities, such as impaired glucose metabolism, renal impairment, left ventricular hypertrophy, heart failure, and others. This review focuses on how selective renal sympathetic denervation works, its present and potential therapeutic indications, and its future directions.

Sympathetic neural regulation of blood pressure: influences of sex and aging

Sex and age have important influences on sympathetic neural control of blood pressure in humans. Young women are relatively protected against risk of hypertension due to greater peripheral vasodilator influences compared with young men and older people. This protective effect is lost at menopause. Older men and women have higher sympathetic nerve activity and tighter coupling between SNA and blood pressure, contributing to the increased risk of hypertension with aging.

Renal denervation: current implications and future perspectives

SNS (sympathetic nervous system) activation is a common feature of arterial hypertension and has been demonstrated to contribute to the development and progression of the hypertensive state. Persuasive evidence suggests a strong association between SNS overactivity and variety of disease states, including chronic renal failure, insulin resistance, congestive heart failure, sleep apnoea, ventricular arrhythmias and others. Although sympatholytic agents are available to target SNS overactivity pharmacologically, they are not widely used in clinical practice, leaving the SNS unopposed in many patients. The recent introduction of catheter-based renal denervation as an alternative approach to target the SNS therapeutically has been demonstrated to result in a clinically relevant blood pressure reduction in patients with resistant hypertension, presumably through its effects on both efferent and afferent renal nerve traffic. Available data on this interventional procedure demonstrate a favourable vascular and renal safety profile. Preliminary data obtained primarily from small and mostly uncontrolled studies in related disease states often characterized by overactivity of the SNS are promising, but require confirmation in appropriately designed clinical trials. In the present paper, we briefly review the physiology of the renal nerves and their role in hypertension and other relevant disease states, summarize the data currently available from clinical studies pertaining to the safety and efficacy of renal denervation in resistant hypertension, discuss potential future implications and the available data supporting such a role for renal denervation, and describe some of the newer devices currently under investigation to achieve improved blood pressure control via renal denervation.

Achieving renal denervation: catheter-based and surgical management for neural ablation in the management of hypertension

Hypertension refractory to conventional management with medication remains a significant cause of cardiovascular morbidity and mortality. Alternative strategies are warranted in this subgroup of patients. The target of these strategies centers around sympathetic neural activity, which is thought to play a key role in hypertension. We will review the historic and current approaches toward altering sympathetic neural activity, specifically discussing surgical sympathectomy, catheter-based renal denervation strategies, and baroreflex activation therapy.

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.

Disorders of blood pressure regulation-role of catecholamine biosynthesis, release, and metabolism

Catecholamines (epinephrine and norepinephrine) are synthesised and produced by the adrenal medulla and postganglionic nerve fibres of the sympathetic nervous system. It is known that essential hypertension has a significant neurogenic component, with the rise in blood pressure mediated at least in part by overactivity of the sympathetic nervous system. Moreover, novel therapeutic strategies aimed at reducing sympathetic activity show promise in the treatment of hypertension. This article reviews recent advances within this rapidly changing field, particularly focusing on the role of genetic polymorphisms within key catecholamine biosynthetic enzymes, cofactors, and storage molecules. In addition, mechanisms linking the sympathetic nervous system and other adverse cardiovascular states (obesity, insulin resistance, dyslipidaemia) are discussed, along with speculation as to how recent scientific advances may lead to the emergence of novel antihypertensive treatments.