Renal sympathetic denervation in Sweden: a report from the Swedish registry for renal denervation.

W e have read the observational study entitled ‘Renal sympathetic denervation in Sweden: a report from the Swedish registry for renal denervation’ by Völz et al [1] in the Journal of Hypertension. We want to congratulate the authors for this successful report, and make some comments and contributions. The authors of the study showed that renal denervation (RDN) was associated with a sustained reduction in office and ambulatory blood pressure (BP) in patients with resistant hypertension through 36 months. However, unlike other reports, the BP reduction was larger and the adverse event rates were lower. First, we would like to know more details about the patients that have had cardiovascular events during the follow-up duration, including the rate of myocardial infarction, unstable angina, revascularization procedures, as well as the cardiovascular, and all-cause mortalities. Given that it is a very high-risk population, in which the effects of RDN are being investigated, it is of utmost importance to obtain specific clinical outcomes and not only the reasons for hospitalizations. Second, we would like to know more details about the ablation procedures, including which renal arteries (main vs. side branches, their size, etc.) and how many vessels have been ablated. There have been some descriptions about the association between the extension of the ablation and the degree of BP reduction achieved. This information could explain the larger reduction in BP observed in this report. Furthermore, looking at Figure 4 in the original article [1] that shows the rate of non-responders; we believe that providing the baseline characteristics in a comparative table showing responders vs. nonresponders would help in selecting patients that are more likely to benefit from this procedure. Moreover, as the positive impact of RDN in clinical registries is well established, it would be important for readers to see results on possible positive impact of RDN beyond BP control, including target organ damage such as left ventricular hypertrophy and microalbuminuria, which would argue strongly in favor of the benefit of RDN in this population. Finally, as has been demonstrated in this article, RDN is a very safe procedure and most of the complications come from vascular access, as this is currently being performed mainly through femoral access in patients with very high BP levels and obesity, both of which are predictors of femoral access complications. Therefore, we believe that future RDN procedures may be performed through radial access. We would like to recognize the contribution of the authors in providing real-world data. We will be awaiting the results of ongoing randomized controlled trials for the practice to be changed.