Multimodality Intra-Arterial Imaging Assessment of the Vascular Trauma Induced by Balloon-Based and Nonballoon-Based Renal Denervation Systems

Renal Denervation in the Treatment of Resistant Hypertension and Difficult-to-Control Hypertension - Consensus Document of the Croatian Hypertension League - Croatian Society of Hypertension, Croatian Cardiac Society, Croatian Endovascular Initiative, Croatian Society for Diabetes and Metabolic Diseases, Croatian Renal Association, and Croatian Society of Family Physicians of the Croatian Medical Association

Renal denervation (RDN) as a method of treating arterial hypertension (AH) was introduced in Croatia in 2012. A multidisciplinary team and a network of hospitals that diagnose and treat patients with severe forms of AH were established, and a very strict diagnostic-treatment algorithm was prepared. At monthly meetings patients with truly resistant hypertension who were candidates for RDN were discussed. According to the 2021 ESH position statement and 2023 ESH guidelines, RDN is considered an alternative and additional, not a competitive method of treating patients with various forms of AH which must be performed by following a structured procedure and the patient's preference should be considered. In view of the changes in the global scientific community, the Croatian Hypertension League brings this consensus document on RDN conducted with radiofrequency-based catheter, the only currently available method in Croatia. In this document, exclusion and inclusion criteria are shown, as well as three groups of patients in whom RDN could be considered. The new diagnostic-treatment algorithm is prepared and follow-up procedure is explained. In Croatia, RDN is reimbursed by the national insurance company, thus pharmacoeconomic analyses is also shown. Criteria required by an individual centre to be approved of RDN are listed, and plans for prospective research on RDN in Croatia, including the Croatian registry for RDN, are discussed.

The safety of renal denervation as assessed by optical coherence tomography: pre- and post-procedure comparison with multi-electrode ablation catheter in animal experiment

OBJECTIVE

To prove the effectiveness and safety of multi-electrode ablation catheter in renal denervation (RDN) by optical coherence tomography (OCT).

METHODS

Sixteen renal arteries were enrolled from 8 pigs. Angiography and OCT were performed to analyze the morphological changes before RDN and at 1-month follow-up. Blood pressure and creatinine were measured to prove the effectiveness and safety of the catheter.

RESULTS

One renal artery was excluded because of the small diameter. Fifteen renal arteries successfully underwent renal denervation and OCT. Mean blood pressure was significantly reduced at 1 month after RDN (122.40 ± 3.54 mmHg vs. 106.50 ± 2.06 mmHg, n = 8, P < .001). Creatinine follow-up after 1 month showed no significant change (45.37 ± 7.44 vs. 65.87 ± 49.20 μmol/L, n = 8, P = 0.275). The minimal lumen diameter showed that the renal artery immediately narrowed after the procedure (7.17 ± 0.60 mm vs. 5.93 ± 0.97 mm, n = 15, P < .001). Vasospasm, vascular wall edemas, and thrombus formations all showed significant changes after the procedure except renal artery dissection (0% vs. 21.4%, P = 0.067) under the OCT. Adverse event as renal artery occluded showed no significant difference (0% vs. 6.7%, P > .05). OCT results showed no significant difference in vasospasm, dissections, wall edemas, and thrombus formations (P > .05) at 1 month after the procedure.

CONCLUSION

This multi-electrode ablation catheter could cause minor injury to renal artery instantly after RDN, but it is found to be safe in the animal model at 1-month follow-up.

Acute changes in histopathology and intravascular imaging after catheter-based renal denervation in a porcine model

OBJECTIVES

We first aimed to identify the histopathological changes occurring immediately after renal denervation (RDN) with radiofrequency energy, and then to assess the feasibility of determining procedural success using currently available clinical intravascular imaging techniques.

BACKGROUND

Catheter-based RDN has been used as an alternative therapy for hypertension. However, no practical endpoint to determine procedural success during treatment has been established.

METHODS

A total of 39 ablation lesions were induced in vivo in eight porcine renal arteries and a total of 15 ablation lesions were induced ex vivo in five excised porcine renal arteries with a radiofrequency delivery device. Acute histological changes and appearance on intravascular imaging of the lesions were investigated with light microscopy, transmission electron microscopy, intravascular ultrasound (IVUS), and optical frequency domain imaging (OFDI).

RESULTS

Marked changes were noted in media, adventitia, and perirenal-arterial nerves immediately after in vivo ablation. Changes visualized on IVUS were characterized by focal adventitial thickening comprising a relatively echogenic layer around a heterogeneously hypoechoic interior region, and on OFDI as disappearance of the external elastic membrane signals with high scattering of signals in the surface layer. The changes after ex vivo ablation were histopathologically identical to those from in vivo ablation. There were statistically significant positive correlations in measured dimensions (area, depth, width, and diameter) of ablation lesions between histopathology and IVUS/OFDI findings (Pearson correlation coefficients = 0.69-0.77).

CONCLUSIONS

These findings suggest that observation of treated renal arteries by IVUS or OFDI immediately after RDN improves the success rate of RDN.

Device-based Therapy for Hypertension

Hypertension continues to be a major contributor to global morbidity and mortality, fuelled by an abundance of patients with uncontrolled blood pressure despite the multitude of pharmacological options available. This may occur as a consequence of true resistant hypertension, through an inability to tolerate current pharmacological therapies, or non-adherence to antihypertensive medication. In recent years, there has been a rapid expansion of device-based therapies proposed as novel non-pharmacological approaches to treating resistant hypertension. In this review, we discuss seven novel devices—renal nerve denervation, baroreflex activation therapy, carotid body ablation, central iliac arteriovenous anastomosis, deep brain stimulation, median nerve stimulation, and vagal nerve stimulation. We highlight how the devices differ, the varying degrees of evidence available to date and upcoming trials. This review also considers the possible factors that may enable appropriate device selection for different hypertension phenotypes.

Interventional procedures and future drug therapy for hypertension

Hypertension management poses a major challenge to clinicians globally once non-drug (lifestyle) measures have failed to control blood pressure (BP). Although drug treatment strategies to lower BP are well described, poor control rates of hypertension, even in the first world, suggest that more needs to be done to surmount the problem. A major issue is non-adherence to antihypertensive drugs, which is caused in part by drug intolerance due to side effects. More effective antihypertensive drugs are therefore required which have excellent tolerability and safety profiles in addition to being efficacious. For those patients who either do not tolerate or wish to take medication for hypertension or in whom BP control is not attained despite multiple antihypertensives, a novel class of interventional procedures to manage hypertension has emerged. While most of these target various aspects of the sympathetic nervous system regulation of BP, an additional procedure is now available, which addresses mechanical aspects of the circulation. Most of these new devices are supported by early and encouraging evidence for both safety and efficacy, although it is clear that more rigorous randomized controlled trial data will be essential before any of the technologies can be adopted as a standard of care.

Renal denervation for the management of resistant hypertension

Renal sympathetic denervation (RSD) as a therapy for patients with resistant hypertension has attracted great interest. The majority of studies in this field have demonstrated impressive reductions in blood pressure (BP). However, these trials were not randomized or sham-controlled and hence, the findings may have been overinflated due to trial biases. SYMPLICITY HTN-3 was the first randomized controlled trial to use a blinded sham-control and ambulatory BP monitoring. A surprise to many was that this study was neutral. Possible reasons for this neutrality include the fact that RSD may not be effective at lowering BP in man, RSD was not performed adequately due to limited operator experience, patients’ adherence with their anti-hypertensive drugs may have changed during the trial period, and perhaps the intervention only works in certain subgroups that are yet to be identified. Future studies seeking to demonstrate efficacy of RSD should be designed as randomized blinded sham-controlled trials. The efficacy of RSD is in doubt, but many feel that its safety has been established through the thousands of patients in whom the procedure has been performed. Over 90% of these data, however, are for the Symplicity™ system and rarely extend beyond 12 months of follow-up. Long-term safety cannot be assumed with RSD and nor should it be assumed that if one catheter system is safe then all are. We hope that in the near future, with the benefit of well-designed clinical trials, the role of renal denervation in the management of hypertension will be established.