Renal Denervation After SYMPLICITY HTN-3: Where Do We Go?

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

Despite the current availability of safe and efficient drugs for treating hypertension, a substantial number of patients are drug-resistant hypertensives. Aiming this condition, a relatively new approach named catheter-based renal denervation was developed. We have now a clinically relevant time window to review the efficacy of renal denervation for treating this form of hypertension. This short review addresses the physiological contribution of renal sympathetic nerves for blood pressure control and discusses the pros and cons of renal denervation procedure for the treatment of resistant hypertension.

Safety and Efficacy of a New Renal Denervation Catheter in Hypertensive Patients in the Absent of Antihypertensive Medications: A Pilot Study

Aim

The aim of present study was to determine the safety and efficacy of a new renal artery denervation system for treatment of hypertensive patients.

Methods

Hypertensive patients with mean office systolic blood pressure ≥150mmHg and ≤180mmHg or an average of 24-hour ambulatory systolic blood pressure ≥145mmHg and ≤170mmHg after stopping hypertensive medications for 2 weeks or more were enrolled to undergo renal denervation (RDN) using a new RDN system. Changes in office blood pressure and mean 24-hour ambulatory blood pressure and safety were assessed after 6 months.

Results

Fifteen patients underwent RDN and followed up for 6 months. At the 6-month follow-up, office systolic blood pressure decreased 11.5±9.9mmHg (P<0.01) and office diastolic blood pressure decreased 6.9±4.8mmHg (P<0.01); mean 24-hour ambulatory systolic blood pressure decreased 7.5±7.7mmHg (P<0.05) and mean 24-hour diastolic blood pressure decreased 3.3±4.7mmHg (P>0.05) compared to baseline values. There were no serious RDN-related adverse events during follow-up.

Conclusion

Our results demonstrate that the new RDN system is safe and could significantly reduce blood pressure in hypertensive patients in the absence of antihypertensive medications. This trial is registered with ChiCTR1800017815.

Renal perivascular adipose tissue: Form and function

Renal sympathetic activity affects blood pressure in part by increasing renovascular resistance via release of norepinephrine (NE) from sympathetic nerves onto renal arteries. Here we test the idea that adipose tissue adjacent to renal blood vessels, i.e. renal perivascular adipose tissue (RPVAT), contains a pool of NE which can be released to alter renal vascular function. RPVAT was obtained from around the main renal artery/vein of the male Sprague Dawley rats. Thoracic aortic PVAT and mesenteric PVAT also were studied as brown-like and white fat comparators respectively. RPVAT was identified as a mix of white and brown adipocytes, because of expression of both brown-like (e.g. uncoupling protein 1) and white adipogenic genes. All PVATs contained NE (ng/g tissue, RPVAT:524 ± 68, TAPVAT:740 ± 16, MPVAT:96 ± 24). NE was visualized specifically in RPVAT adipocytes by immunohistochemistry. The presence of RPVAT (+RPVAT) did not alter the response of isolated renal arteries to NE compared to responses of arteries without RPVAT (-RPVAT). By contrast, the maximum contraction to the sympathomimetic tyramine was ~2× greater in the renal artery +PVAT versus -PVAT. Tyramine-induced contraction in +RPVAT renal arteries was reduced by the α₁-adrenoceptor antagonist prazosin and the NE transporter inhibitor nisoxetine. These results suggest that tyramine caused release of NE from RPVAT. Renal denervation significantly (>50%) reduced NE content of RPVAT but did not modify tyramine-induced contraction of +RPVAT renal arteries. Collectively, these data support the existence of a releasable pool of NE in RPVAT that is independent of renal sympathetic innervation and has the potential to change renal arterial function.

Spironolactone versus sympathetic renal denervation to treat true resistant hypertension: results from the DENERVHTA study - a randomized controlled trial

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Objective:

Both renal denervation (RDN) and spironolactone have been proposed for the treatment of resistant hypertension. However, they have not been compared in a randomized clinical trial. We aimed to compare the efficacy of spironolactone versus RDN in patients with resistant hypertension.

Methods:

A total of 24 patients with office SBP at least 150 mmHg and 24-h SBP at least 140 mmHg despite receiving at least three full-dose antihypertensive drugs, one a diuretic, but without aldosterone antagonists, were randomized to receive RDN or spironolactone (50 mg) as add-on therapy. Primary endpoint was change in 24-h SBP at 6 months. Comparisons between treatment groups were performed using generalized linear models adjusted by age, sex, and baseline values.

Results:

Spironolactone was more effective than RDN in reducing 24-h SBP and 24-h DBP: mean baseline-adjusted differences between the two groups were −17.9 mmHg (95%CI −30.9 to −4.9); P = 0.010 and −6.6 mmHg (95%CI −12.9 to −0.3); P = 0.041, for 24-h SBP and 24-h DBP, respectively. As regards changes in office blood pressure, mean baseline-adjusted differences between the two groups were −12.1 mmHg (95%CI −29.1 to 5.1); P = 0.158 and of −5.3 mmHg (95%CI −16.3 to 5.8); P = 0.332, for office SBP and office DBP, respectively. Otherwise, the decrease of estimated glomerular filtration rate was greater in the spironolactone group; mean baseline-adjusted difference between the two groups was −10.7 ml/min per 1.73 m² (95%CI −20.1 to −1.4); P = 0.027.

Conclusion:

We conclude that spironolactone is more effective than RDN to reduce 24-h SBP and 24-h DBP in patients with resistant hypertension. Therefore, spironolactone should be the fourth antihypertensive drug to prescribe if deemed well tolerated’ in all patients with resistant hypertension before considering RDN.

Pathophysiology and Potential Non-Pharmacologic Treatments of Obesity or Kidney Disease Associated Refractory Hypertension

PURPOSE OF REVIEW

The review assesses the role of non-pharmacologic therapy for obesity and chronic kidney disease (CKD) associated refractory hypertension (rf HTN).

RECENT FINDINGS

Hypertensive patients with markedly heightened sympathetic nervous system (SNS) activity are prone to develop refractory hypertension (rfHTN). Patients with obesity and chronic kidney disease (CKD)-associated HTN have particularly heightened SNS activity and are at high risk of rfHTN. The role of bariatric surgery is increasingly recognized in treatment of obesity. Current evidence advocates for a greater role of bariatric surgery in the management of obesity-associated HTN. In contrast, renal denervation does not appear have a role in the management of obesity or CKD-associated HTN. The role of baroreflex activation as adjunctive anti-hypertensive therapy remains to be defined.

Renal Denervation vs. Spironolactone in Resistant Hypertension: Effects on Circadian Patterns and Blood Pressure Variability

BACKGROUND

Sympathetic renal denervation (SRD) has been proposed as a therapeutic alternative for patients with resistant hypertension not controlled on pharmacological therapy. Two studies have suggested an effect of SRD in reducing short-term blood pressure variability (BPV). However, this has not been addressed in a randomized comparative trial. We aimed to compare the effects of spironolactone and SRD on circadian BP and BPV.

METHODS

This is a post-hoc analysis of a randomized trial in 24 true resistant hypertensive patients (15 men, 9 women; mean age 64 years) comparing 50mg of spironolactone (n = 13) vs. SRD (n = 11) on 24-hour BP. We report here the comparative effects on daytime (8 am-10 pm) and nighttime (0 am-6 am) BP, night-to-day ratios and BP and heart rate variabilities (SD and coefficient of variation of 24-hour, day and night, as well as weighted SD and average real variability (ARV)).

RESULTS

Spironolactone was more effective than SRD in reducing daytime systolic (P = 0.006), daytime diastolic (P = 0.006), and nighttime systolic (P = 0.050) BP. No differences were observed in the night-to-day ratios. In contrast, SRD-reduced diastolic BPV (24 hours, daytime, nighttime, weighted, and ARV; all P < 0.05) with respect to spironolactone, without significant differences in systolic BPV.

CONCLUSION

Spironolactone is more effective than SRD in reducing ambulatory BP. However, BPV is significantly more reduced with SRD. This effect could be important in terms of potential prevention beyond BP reduction and deserves further investigation.

[Criteria for selecting patients with resistant hypertension for a renal sympathetic denervation]

AIM

to define and develop a procedure that can select patients with resistant hypertension (RH) for a renal sympathetic denervation (RSD) procedure, by being orienting to the specific initial values of β-adrenoreactivity (β-AR) and systolic blood pressure (SBP).

SUBJECTS AND METHODS

The analysis included 23 RH patients receiving the maximally tolerable doses of 4 antihypertensive drugs. The investigations involving BP control and a Russian spectrophotometric procedure for determining β-AR in terms of the change in the osmoresistance of erythrocyte membranes (EM) were performed at baseline and 4 and 24 weeks. RSD was carried out using endovascular radiofrequency ablation of the renal arteries. The therapy was not changed during the observation.

RESULTS

If SBP was >170 mm Hg and β-AR of EM >40 conditional units (CUs) at baseline, ΔSBP was 17.68±3.24 mm Hg and the efficiency of RSD was 100%. When SBP was <170 mm Hg and β-AR of EM <40 CUs at baseline, ΔSBP was 0.97±4.21 mm Hg (p>0.05) and the efficiency of RSD was low.

CONCLUSION

The overall estimate of baseline SBP and β-AR of EM in patients with RH could determine the expediency of the RSD procedure in order to lower BP. The proposed procedure can optimize the selection of patients and enhance the efficiency of RSD in the treatment of RH.

Renal Denervation vs Pharmacotherapy for Resistant Hypertension: A Meta-Analysis

The effect of renal denervation (RD) for resistant hypertension remains controversial because of the conflicting results of finished and ongoing studies. The authors performed a meta-analysis of case-control studies to identify whether renal sympathetic denervation or pharmacotherapy (PHAR) was more effective for resistant hypertension. A systematic Internet database search of relevant papers written in English was performed. A total of nine studies met the inclusion criteria, with a total of 1096 patients. When comparing the RD group with the PHAR group, there was a significant decrease in systolic blood pressure (SBP) (weighted mean difference, -12.81 mm Hg; 95% confidence interval [CI], -22.77 mm Hg to -2.85 mm Hg; P=.01) and diastolic blood pressure (DBP) (weighted mean difference, -5.56; 95% CI, -8.15 mm Hg to -2.97 mm Hg; P<.0001). This pooled analysis shows that for patients with resistant hypertension, RD is more effective in reducing SBP and DBP than PHAR. RD may be more effective in special subgroups of patients, which needs to be identified in future investigations.

Initial Experience with Renal Denervation for the Treatment of Resistant Hypertension - The Utility of Novel Anesthetics and Metaiodobenzylguanidine Scintigraphy (MIBG)

Background:

The Symplicity-HTN 3 trial failed to show significant difference in blood pressure (BP) lowering between patients undergoing catheter-based renal denervation (RDN) and the sham-procedure arm of the study. However, there is still optimism about the role of RDN in the treatment of resistant hypertension, because identification of patients with increased sympathetic activity thus being good RDN responders, improvements in the RDN procedure and new technology RDN catheters are all expected to lead to better RDN results. We present our initial experience with RDN for the treatment of resistant hypertension, and the utility of novel anesthetics and cardiac ¹²³I-metaiodobenzylguanidine scintigraphy (¹²³I-MIBG).

Methods and Results:

Seven patients with resistant hypertension underwent RDN and were followed up for 6 months. MIBG was performed before RDN, in order to estimate sympathetic activity and predict the response to RDN. All patients were sedated with dexmedetomidine and remifentanil during RDN. All patients tolerated the procedure well, were hemodynamically stable and their peri-procedural pain was effectively controlled. A median of 7.6 ± 2.1 and 6 ± 1.4 ablations were delivered in the right and left renal artery respectively, making an average of 6.8 burns per artery. No peri-procedural or late complications - adverse events (local or systematic) occurred. At 6 months, mean reduction in office BP was -26.0/-16.3 mmHg (p=0.004/p=0.02), while mean reduction in ambulatory BP was -12.3/-9.2 mmHg (p=0.118/p=0.045). One patient (14.3%) was a non-responder. None of the cardiac ¹²³I-MIBG imaging indexes(early and late heart-to-mediastinum (H/M) count density ratio, washout rate (WR) of the tracer from the myocardium) were different between responders and non-responders.

Conclusion:

Patients with resistant hypertension who underwent RDN in our department had a significant reduction in BP 6 months after the intervention. ¹²³I-MIBG was not useful in predicting RDN response. Dexmedetomidine and remifentanil provided sufficient patient comfort during the procedure, allowing an adequate number of ablations per renal artery to be performed, and this could probably lead to improved RDN results.

Renal denervation for the treatment of resistant hypertension: review and clinical perspective

When introduced clinically 6 years ago, renal denervation was thought to be the solution for all patients whose blood pressure could not be controlled by medication. The initial two studies, SYMPLICITY HTN-1 and HTN-2, demonstrated great magnitudes of blood pressure reduction within 6 mo of the procedure and were based on a number of assumptions that may not have been true, including strict adherence to medication and absence of white-coat hypertension. The SYMPLICITY HTN-3 trial controlled for all possible factors believed to influence the outcome, including the addition of a sham arm, and ultimately proved the demise of the initial overly optimistic expectations. This trial yielded a much lower blood pressure reduction compared with the previous SYMPLICITY trials. Since its publication in 2014, there have been many analyses to try and understand what accounted for the differences. Of all the variables examined that could influence blood pressure outcomes, the extent of the denervation procedure was determined to be inadequate. Beyond this, the physiological mechanisms that account for the heterogeneous fall in arterial pressure following renal denervation remain unclear, and experimental studies indicate dependence on more than simply reduced renal sympathetic activity. These and other related issues are discussed in this paper. Our perspective is that renal denervation works if done properly and used in the appropriate patient population. New studies with new approaches and catheters and appropriate controls will be starting later this year to reassess the efficacy and safety of renal denervation in humans.