Renal sympathetic denervation for resistant hypertension: where do we stand after more than a decade

Advances on the Experimental Research in Resistant Hypertension

PURPOSE OF REVIEW

Resistant Hypertension (RH) poses a significant public health challenge, contributing to increased mortality, cardiovascular events and organ damage. Both clinical and experimental research are striving for higher standards in a translational manner to integrate new findings and confirm hypotheses. Considering that many are the aspects of RH that are still under investigation, this review aims to shed light on the advances made in experimental research concerning RH. It seeks to underscore the pivotal role of experimental studies in shaping clinical practices and also explore future perspectives.

RECENT FINDINGS

It is important to emphasize the significance of experimental models, primarily for advancing our understanding: experimental models have greatly contributed to our comprehension of the underlying mechanisms in RH, including factors like sympathetic activation, endothelial dysfunction and structural vessel abnormalities. Secondly, for assessing treatment approaches: animal models have also played a crucial role in evaluating the potential effectiveness of diverse treatment approaches for RH. These encompass both pharmacological options, involving combinations of established drugs or novel pharmaceuticals, and non-pharmacological alternatives, which include surgical procedures like renal denervation, medical devices like baroreceptor stimulators, and lifestyle modifications. The most lacking component in translational research is the fact that there is no well-established animal model that perfectly replicates RH. Consequently, alternative strategies, including the combination of models, must be considered. What remains clear is that the development of animal models closely mimicking RH holds the promise of providing valuable insights into the essential mechanisms and responses necessary to combat or slow the global progression of RH.

Investigations of Laser-Assisted Renal Denervation for Treatment of Resistant Hypertension

BACKGROUND AND OBJECTIVES

Renal denervation (RDN) is an emerging surgical treatment for resistant hypertension. However, the current RDN using radiofrequency can cause undesirable thermal damage to the medial and luminal layers due to direct contact between the arterial lumen and energy source. The aim of this study is to evaluate the feasibility of the new laser-assisted RDN by exploring the potential treatment conditions.

METHODS

For ex vivo testing, six different treatment conditions (10 and 20 W applied for delivery of 300, 450, and 600 J) were tested on the porcine liver and renal artery (RA) by using a continuous wave 1064 nm laser wavelength. The ablated area in the liver tissue was measured to estimate the extent of the coagulated area. Histological evaluation was performed on the treated RA tissues to confirm the extent of thermal nerve damage.

RESULTS

The ablated depth, length, and area in the liver tissue increased with laser power and total energy. According to the histological results, 20 W groups yielded more significant damage to the RA nerves than 10 W groups at the total energy of 300 J (0.0 ± 0.0 mm for 10 W vs. 2.9 ± 1.0 mm for 20 W), 450 J (1.9 ± 0.6 mm for 10 W vs. 6.8 ± 1.5 mm for 20 W), and 600 J (2.9 ± 0.4 mm for 10 W vs. 7.3 ± 0.8 mm for 20 W). The treated RA exhibited insignificant medial injury in depth (medial thinning ≤ 25%), and no difference in the medial thinning was found among the six groups (p = 0.4).

CONCLUSION

The current study demonstrated that the 1064 nm laser at 20 W with delivery of 450 J could effectively damage the RA nerves with no or minimal injury to the surrounding tissue. The proposed laser-assisted RDN may enhance physiological effects with insignificant complications in in vivo situations. Further in vivo studies will be conducted to validate the current findings by evaluating the extent of blood pressure reduction and norepinephrine changes after the laser-assisted RDN on a large animal model.

Impact of Obstructive Sleep Apnea and Sympathetic Nervous System on Cardiac Health: A Comprehensive Review

A prevalent condition linked to an elevated risk of cardiovascular disease is sleep apnea. This review examines the connections between cardiac risk, the sympathetic nervous system, and sleep apnea. The increased risk of hypertension, arrhythmias, myocardial infarction, and heart failure was highlighted in the pathophysiology of sleep apnea and its effect on sympathetic activation. It is also important to consider potential processes such as oxidative stress, inflammation, endothelial dysfunction, and autonomic imbalance that may relate sleep apnea-induced sympathetic activation to cardiac risk. With implications for creating innovative diagnostic and treatment approaches to lessen the cardiovascular effects of sleep apnea, the goal of this investigation is to improve the understanding of the intricate link between sympathetic activity, cardiac risk, and sleep apnea. This study aimed to clarify the complex relationship between cardiovascular health and sleep apnea by synthesizing the available research and highlighting the crucial role played by the sympathetic nervous system in moderating this relationship. Our thorough investigation may have important therapeutic ramifications that will direct the creation of focused therapies to enhance cardiovascular outcomes in sleep apnea sufferers.

Laser renal denervation: A comprehensive evaluation of microstructural renal artery lesions

Renal artery denervation (RDN) has been proposed for resistant arterial hypertension. Beyond conventional radiofrequency (RF) ablation, there are emerging RDN technologies, including laser catheter ablation. We aimed at evaluamting the local effects of laser ablation on the renal artery and perivascular nerve injury in comparison with radiofrequency ablation. Thirteen pigs (mean weight 36.7 ± 4.7 kg, age 3 months) were divided into three groups: (1) laser ablation in normotensive pigs (LA; n = 3), (2) bipolar RF ablation in normotensive pigs (RF; n = 7), and (3) a sham group (SHAM; n = 3). Transcatheter laser and RF ablations were performed under general anesthesia. After euthanasia, pathology and immunohistochemical studies were performed. Artery wall and perivascular nerve lesions were found in the LA and RF groups. A lower rate of intimal microdissections was evaluated after laser ablation when compared with RF ablation (0 vs. 1.5 [1;2.75] per artery; p < .05). There was a numerical prevalence of nerves with tyrosine hydroxylase expression loss after laser RDN when compared with RF ablation (16.7 [4; 18] vs. 9.1 [0;18] per specimen). Laser ablation is noninferior to RF ablation regarding perivascular nerve injury and is associated with less intimal layer damage.

Denervation or stimulation? Role of sympatho-vagal imbalance in HFpEF with hypertension

Heart failure (HF) in the elderly is an increasingly large and complex problem in modern society. Notably, the cause of HF with preserved ejection fraction (HFpEF) is multifactorial and its pathophysiology is not fully understood. Among these, hypertension has emerged as a pivotal factor in the pathophysiology and therapeutic targets of HFpEF. Neuronal elements distributed throughout the cardiac autonomic nervous system, from the level of the central autonomic network including the insular cortex to the intrinsic cardiac nervous system, regulate the human cardiovascular system. Specifically, increased sympathetic nervous system activity due to sympatho-vagal imbalance is suggested to be associated the relationship between hypertension and HFpEF. While several new pharmacological therapies, such as sodium-glucose cotransporter 2 inhibitors, have been shown to be effective in HFpEF, neuromodulatory therapies of renal denervation and vagus nerve stimulation (VNS) have received recent attention. The current review explores the pathophysiology of the brain-heart axis that underlies the relationship between hypertension and HFpEF and the rationale for therapeutic neuromodulation of HFpEF by non-invasive transcutaneous VNS.

Effect of Renal Denervation on the Plasma Adiponectin Concentration in Patients with Resistant Hypertension

(1) Introduction: Adiponectin is synthetized by white adipose tissue and has anti-diabetic, anti-atherosclerotic, anti-thrombotic, anti-inflammatory, and cardioprotective properties. In patients with arterial hypertension, plasma concentration of adiponectin is lower than in healthy subjects. Renal denervation, i.e., percutaneous ablation of fibers from the sympathetic nervous system located in the wall of the renal arteries by radio frequency waves, is a method of resistant arterial hypertension treatment. (2) The aim of this single center, interventional, clinical study was to assess the effect of renal denervation on the plasma adiponectin concentration in patients with resistant arterial hypertension. (3) Materials and methods: 28 patients (13 women, 15 men) aged 54.4 ± 9.2 years with resistant hypertension who underwent renal denervation using Simplicity catheters (Medtronic, Inc., Northridge, CA, USA) were enrolled in the study. Plasma adiponectin concentration was determined using the Human Adiponectin ELISA Kit (Otsuka Pharmaceutical Co, Tokyo, Japan) before the renal denervation and 6 and 12 months after this procedure. (4) Results: Blood pressure (BP) values before renal denervation and 6 and 12 months after this procedure were as follows: systolic BP 190.4 ± 24.5, 160.8 ± 14.5, 155.7 ± 17.9 mmHg (p < 0.001) and diastolic BP 111.7 ± 18.9, 88.9 ± 8.3, 91.2 + 10.2 mmHg (p < 0.001), respectively. Body mass index (BMI) before renal denervation, 6 and 12 months after this procedure were 31.5 ± 4.2, 30.5 ± 4.4, 30.2 ± 4.0 kg/m2, (p = 0.057), respectively. Plasma adiponectin concentration before the renal denervation and 6 and 12 months after this procedure were 4.79 (3.95; 9.49), 7.58 (5.04; 9.51), 6.62 (4.57; 11.65) [µg/mL] (p = 0.007), respectively. (5) Conclusions: Plasma adiponectin concentration increases significantly after successful renal denervation in patients with resistant hypertension. Higher plasma adiponectin concentration may participate—beyond blood pressure reduction—in the cardiovascular benefits related to successful renal denervation; however’ clinical consequences of these results need further investigations.

Renal Denervation Influences Angiotensin II Types 1 and 2 Receptors

The sympathetic and renin-angiotensin systems (RAS) are two critical regulatory systems in the kidney which affect renal hemodynamics and function. These two systems interact with each other so that angiotensin II (Ang II) has the presynaptic effect on the norepinephrine secretion. Another aspect of this interaction is that the sympathetic nervous system affects the function and expression of local RAS receptors, mainly Ang II receptors. Therefore, in many pathological conditions associated with an increased renal sympathetic tone, these receptors' expression changes and renal denervation can normalize these changes and improve the diseases. It seems that the renal sympathectomy can alter Ang II receptors expression and the distribution of RAS receptors in the kidneys, which influence renal functions.

2022 Malaysian Working Group Consensus Statement on Renal Denervation for management of arterial hypertension

Hypertension is highly prevalent and a major contributor to cardiovascular mortality and morbidity. In spite of the availability of efficacious, safe and affordable anti-hypertensive drugs, hypertension remains poorly controlled in the majority of hypertensive patients. Various reasons including non-adherence to the anti-hypertensive drugs, account for the poor control. Resistant hypertension is also one of the reasons for poor control of blood pressure (BP). The sympathetic nervous system (SNS) has long been recognized as one of the determinants in the pathophysiology of a raised BP. Overactivity of the SNS is a contributor to sustained arterial hypertension. Renal denervation (RDN) is increasingly recognized as a safe and effective adjunctive therapy to control BP with or without pharmacotherapy. Hence for patients who remain uncontrolled despite all efforts, renal denervation (RDN) is a novel treatment that can potentially improve BP control, hence reducing the major adverse cardiovascular events (MACE). More recent randomized, sham control trials of RDN have shown that RDN produces a sustained lowering of BP. To date, this lowering of BP through RDN is maintained for at least 3 years. Furthermore, this procedure has been found to be safe. Hence this consensus summarises the science behind RDN and the available clinical data to support the use of this therapy. It is hoped that this consensus will offer guidance on the importance of identifying patients who will benefit most from this therapy. A multidisciplinary team approach in the management of the patient undergoing RDN is recommended.

Insights into the Mechanisms of Fetal Growth Restriction-Induced Programming of Hypertension

In recent decades, both clinical and animal studies have shown that fetal growth restriction (FGR), caused by exposure to adverse uterine environments, is a risk factor for hypertension as well as for a variety of adult diseases. This observation has shaped and informed the now widely accepted theory of developmental origins of health and disease (DOHaD). There is a plethora of evidence supporting the association of FGR with increased risk of adult hypertension; however, the underlying mechanisms responsible for this correlation remain unclear. This review aims to explain the current advances in the field of fetal programming of hypertension and a brief narration of the underlying mechanisms that may link FGR to increased risk of adult hypertension. We explain the theory of DOHaD and then provide evidence from both clinical and basic science research which support the theory of fetal programming of adult hypertension. In addition, we have explored the underlying mechanisms that may link FGR to an increased risk of adult hypertension. These mechanisms include epigenetic changes, metabolic disorders, vascular dysfunction, neurohormonal impairment, and alterations in renal physiology and function. We further describe sex differences seen in the developmental origins of hypertension and provide insights into the opportunities and challenges present in this field.

Renal Denervation – a Modern Option for Treating Resistant Hypertension

Hypertension is one of the main cardiovascular risk factors, and it remains an important health problem, demonstrating an increasing incidence despite new treatment methods. Numerous risk factors that can lead to the development of difficult-to-treat or resistant hypertension have been described in the literature in recent years. In this type of hypertension, an important role is played by the sympathetic nervous system. Especially in these cases, with a sympathetic overactivation, renal denervation has proven its efficacy and safety in lowering blood pressure. In this brief clinical update, we present the results of the main studies regarding the efficacy and safety of the renal denervation technique used in the treatment of resistant hypertension.