Renal denervation is performed by inserting a catheter with four electrodes into the renal arteries via the femoral approach. Once the device is in place, the catheter emits a heat of between 40 and 50 degrees to cancel out small nerves that are in the renal artery. In this way, the kidney creates a smaller amount of the hormones that increase the tension.
The intervention is performed on both kidneys. The procedure is carried out under a local anaesthetic and takes around an hour. You may need to stay in hospital overnight following the procedure but should be able to return to your daily activities afterwards. The main risk of renal denervation is dissection of the renal artery, but this can be treated with a stent. Other risks include bruising and bleeding. Renal denervation does not appear to cause any damage to renal function.
Renal denervation. Abstract Arterial hypertension is a common and an increasing health care problem. Introduction Arterial hypertension is one of the most important and prevalent risk factors for cardiovascular diseases. Methods and Results 2. Figure 1. Role of sympathetic activation in blood pressure regulation. Figure 2. Figure 3. So-called notches in the renal artery after successful RDT. These notches disappear over time. References J. View at: Google Scholar M.
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Renal denervation RDN is a catheter-based ablation procedure designed to treat resistant hypertension RH. The objective of our study is to determine the effect of RDN on blood pressure and renal function in patients with RH in comparison to medical therapy alone.
We calculated a weighted standardized mean difference of blood pressure and renal outcomes between RDN and control groups using random effects models. Our search yielded studies of which we included 15 studies for the final analysis. Only 5 studies were double-blinded RCT with sham control. Our meta-analysis of 15 RCTs showed no significant benefit of RDN on blood pressure control in patients with resistant hypertension. Resistant hypertension RH is defined as blood pressure that remains above guideline-directed goal despite the concurrent use of at least three antihypertensive agents of different classes, one of which is a diuretic 1.
The prevalence of RH based on recent studies is ranging from as low as A study by Dougherty et al. When hypertension remains uncontrolled with lifestyle changes and antihypertensive medications, renal denervation has been a proposed intervention to aid in the treatment of RH since it was first used a decade ago 5.
Since then, there have been numerous studies and randomized control trials to evaluate the effectiveness of this procedure in treating RH with variable results.
One of the most recent meta-analysis w by Fadl Elmula et al. Our search yielded studies. After exclusion of duplicates, studies remained of which we included 15 studies for the final analysis Fig. Of the included studies, only 5 were double blinded randomized control trials with sham control 7 , 8 , 11 , 12 , 13 , while the remaining 10 trials were open-label clinical trials with a control group treated with optimal medical therapy 9 , 10 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , Only 11 studies reported a change in estimated glomerular filtration rate eGFR between baseline and 6 months post-randomization in the treatment and control groups.
The baseline characteristics of the included studies are included in Table 1. Baseline characteristics of study participants of the included studies are reported in the Supplementary Tables S1 and S2. The overall quality of the included randomized control trials was high based on the Jadad scale except for the study by Warchol-Celinska et al. The results are summarized in Fig. However, the subgroup of sham control studies had a low degree of heterogeneity, which likely contributed to the statistical significance achieved in this subgroup.
This suggests that the lower prevalence of coronary artery disease and sham control study design contributed to the lack of difference noted between both groups. Adjusted standardized mean difference in office diastolic blood pressure after renal denervation. Meta regression analysis showed that none of the tested covariates influenced the change in eGFR reported by the studies Supplementary Table S5.
Adjusted standardized mean difference in estimated glomerular filtration rate after renal denervation. The funnel plot for the meta-analysis showed significant asymmetry suggesting publication bias. However, the trim-and-fill method showed no need for adjusting the effect size for the meta-analysis. Our meta-analysis of high-quality randomized control trials Table S3 shows no significant benefit of RDN over medical therapy in reducing blood pressure in patients with RH.
Sham controlled randomized control trials have a semi-blinded design which is aimed to negate patient and physician-related confounders on the results as described previously in the literature 22 , 23 , A Sham procedure typically involves an invasive procedure performed in the patients randomized to the control group.
However, perfect blinding is infrequently achieved. However, the newer trials 8 , 9 , 10 have shown a trend towards improved blood pressure control with renal denervation in comparison to medical therapy alone.
Significant heterogeneity was observed when all the included studies were analyzed together. The differences in blood pressure changes could in part be explained by differences in study design, type of control group and type of RDN procedure performed.
It is widely believed that the experience of an operator plays a major role in the success of the procedure. In the initial trials, patients were enrolled from centers with very low operator volume which probably affected the success of the procedure.
However over a period of time, since the first trial Symplicity HTN 2 16 was performed in , operators have become more proficient with the procedure leading to better outcomes. This also explains the heterogeneity of the results among the trials. Most trials included in our analysis showed an improvement in blood pressure in the control group during the course of the trial.
This could be attributed to the following reasons 1 Placebo effect in patients who underwent sham controlled procedures. However it has several limitations including 1 presence of single electrode leading to longer ablation time, 2 presence of unipolar electrode makes a selection of ablation site challenging and 3 inability to ablate deep renal sympathetic nerve due to low radiofrequency power of the catheter limiting the penetration depth.
They are multi-electrode catheters containing 4 electrodes and can simultaneously ablate 4 locations at the same time. The use of multiple catheter systems could potentially contribute to the heterogeneity noted in our analysis. The renal denervation procedure using RF ablation performed in this trial targeted branch vessels beyond the proximal main renal artery which was unique.
Animal studies have shown a greater reduction in renal norepinephrine levels with RF ablation if the distal extra-renal artery branches were targeted This hypothesis was further tested by Petrov et al.
The study showed that significantly higher reduction in ambulatory blood pressure with US ablation compared to conventional RF ablation of main renal arteries. However, no difference in blood pressure reduction was noted between patients who underwent US ablation compared to patients who underwent RF ablation of main and side branches of renal arteries. This further explains the degree of heterogeneity noted in our analysis. A predominant confounder in randomized control trials evaluating the efficacy of a novel therapy is the medication adherence among study participants.
In this instance, if the medication adherence significantly improves after the patient undergoes renal denervation; the true effect of the procedure would be difficult to estimate.
The remaining 11 studies assessed medication adherence using compliance diary or validated questionnaires. Accurate assessment of medication non-adherence is difficult given the invasive nature of the tests and incorporation into routine practice remains a challenge given the tests are cost-intensive. We have also shown that patients who underwent RDN had no significant changes in renal function eGFR compared to the medical therapy group at 6 months post-renal denervation, supporting the safety profile of the procedure.
Our findings are consistent with prior published studies 6 , The positive results noted in the newer trials did not affect the overall result of the meta-analysis. The meta-analysis reported here combines data across studies in order to estimate treatment effects with more precision than is possible in a single study. Limitations include incorporating studies with different control arms and designs to increase the study population and maximizing the likelihood of estimating a treatment effect.
However, the results of the subgroup analyses would be considered more meaningful given the lower heterogeneity. This specifically applies to the pooled analysis of 5 studies which showed a modest improvement in 24 systolic blood pressures with renal denervation. Publication bias might account for some of the effects we observed. Smaller trials are, in general, analyzed with less methodological rigor than larger studies, and an asymmetrical funnel plot suggests that selective reporting may have led to an overestimation of effect sizes in small trials.
The lack of individual participant level data for meta-analysis and subgroup analysis is a limitation of our study. Given the nature of meta-analysis, the inherent weakness of the individual studies will be inherited in our study.
The variability of expertise among all the physicians performing renal denervation could potentially affect the outcome of the procedure, thereby the overall outcome of the individual trials.
The search was restricted to publications in English and the final search was performed till from Jan to June Supplementary data. The initial search was performed by two reviewers PA; JS , and studies were selected for inclusion by mutual consensus. In case of disagreement, a third reviewer RA resolved disagreements through discussion to achieve a consensus. Once the studies were selected for inclusion, the data were screened to meet the inclusion criteria and thereafter the following data points were extracted: number of anti-hypertensive medications, class of anti-hypertensive medications used, eGFR, average office or ambulatory systolic and diastolic blood pressure at baseline and 6 months following the intervention.
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