Safety and long-term effects of renal denervation: Rationale and design of the Dutch registry

BACKGROUND

Percutaneous renal denervation (RDN) has recently been introduced as a treatment for therapy-resistant hypertension. Also, it has been suggested that RDN may be beneficial for other conditions characterised by increased sympathetic nerve activity. There are still many uncertainties with regard to efficacy, safety, predictors for success and long-term effects. To answer these important questions, we initiated a Dutch RDN registry aiming to collect data from all RDN procedures performed in the Netherlands.

METHODS

The Dutch RDN registry is an ongoing investigator-initiated, prospective, multicentre cohort study. Twenty-six Dutch hospitals agreed to participate in this registry. All patients who undergo RDN, regardless of the clinical indication or device that is used, will be included. Data are currently being collected on eligibility and screening, treatment and follow-up.

RESULTS

Procedures have been performed since August 2010. At present, data from 306 patients have been entered into the database. The main indication for RDN was hypertension (n = 302, 99%). Patients had a mean office blood pressure of 177/100 (±29/16) mmHg with a median use of three (range 0-8) blood pressure lowering drugs. Mean 24-hour blood pressure before RDN was 157/93 (±18/13) mmHg. RDN was performed with different devices, with the Simplicity™ catheter currently used most frequently.

CONCLUSION

Here we report on the rationale and design of the Dutch RDN registry. Enrolment in this investigator-initiated study is ongoing. We present baseline characteristics of the first 306 participants.

Cinacalcet for secondary hyperparathyroidism: from improved mineral levels to improved mortality?

Secondary hyperparathyroidism is an almost inevitable complication of advanced kidney failure. The introduction of the calcimimetic cinacalcet for the treatment of secondary hyperparathyroidism in patients on dialysis was based on its ability to reduce elevated levels of parathyroid hormone (PTH). Subsequent clinical studies confirmed the beneficial effects of cinacalcet on biochemical parameters reflecting mineral disturbances and bone disease. In this review we summarise the impact of cinacalcet on biochemical, intermediate and clinical outcomes. We also present previously unpublished mineral metabolism data from 144 Dutch dialysis patients treated with cinacalcet who participated in the pan-European ECHO observational study. Although secondary hyperparathyroidism tended to be more severe in our Dutch cohort, compared with the entire ECHO cohort, cinacalcet was nevertheless effective in reducing PTH in these patients. Two recent clinical studies evaluated, respectively, the efficacy of cinacalcet in improving the intermediate endpoint of cardiovascular calcifications (ADVANCE trial), and its impact on clinical outcomes, including all-cause mortality and cardiovascular events (EVOLVE trial). The ADVANCE trial provided evidence that cinacalcet may indeed improve calcification in both large arteries and cardiac valves. The EVOLVE trial, however, did not meet its clinical primary endpoint (time to all-cause mortality, myocardial infarction, hospitalisation for unstable angina, heart failure or a peripheral vascular event), although secondary and sensitivity analysis suggested a beneficial effect. The clinical implications of these important studies are also addressed in this review.

The relative importance of cyclosporine exposure in heart, kidney or liver transplant recipients on maintenance therapy

We investigated the relationship between cyclosporine exposure and the presence of cyclosporine-related side effects and assessed the advantage of the cyclosporine concentration 2 h post-dose (C(2)) over pre-dose concentration (C(0)) monitoring. Cyclosporine area-under-the-concentration-time curves were measured during the absorption phase (AUC(0-4 h)) in 49 liver, 28 heart and 26 kidney transplant recipients (time since transplantation >6 years) with or without cyclosporine-related side effects on maintenance therapy. The cyclosporine C(0) correlated well with AUC(0-4) (r=0.77), whereas C(2) levels correlated strongly with AUC(0-4) (r=0.92). Although we observed a trend towards higher CsA concentrations in transplant recipients with side effects than in patients without CsA toxicity, the large majority of those differences were not statistically significant. Thus, as cyclosporine exposure was not clearly related to the presence of side effects, and C(0) correlated fairly with AUC(0-4), the advantage of monitoring cyclosporine treatment using C(2) rather than C(0), may be limited for patients on cyclosporine maintenance therapy.

The use of cyclosporine in renal transplantation

The introduction of cyclosporine (CsA) into clinical practice resulted in a dramatic reduction in the incidence and severity of acute rejection. As a result, short-term and medium-term kidney allograft survival increased greatly. However, the long-term patient and graft survival have not improved to a similar degree. This can partly be attributed to the side effects of CsA and partly to the fact that the use of CsA has not led to a reduced incidence of chronic allograft nephropathy. Thus, there has been a continuing search for strategies that minimize CsA toxicity but maintain adequate immunosuppression. This has resulted in the development of the CsA microemulsion formulation and improved methods for therapeutic drug monitoring. With the introduction of newer immunosuppressive drugs, early CsA withdrawal and CsA-free immunosuppressive therapy have become feasible. However, CsA weaning or complete avoidance is associated with a slightly higher risk of acute rejection, and the long-term efficacy and safety of such strategies remain to be established. Therefore, it is to be expected that in the near future CsA will remain part of the standard immunosuppressive regimen in many transplant centers.

Unusual presentation of herpes virus infections in renal transplant recipients exposed to high mycophenolic acid plasma concentrations

Viral infections constitute an important problem for transplant recipients and their physicians. Often the balance between adequate and over-immunosuppression is hard to find and therapeutic drug monitoring might be a welcome adjunct in the management of transplant patients. We report four renal transplant recipients with extra-ordinary presentations of viral disease who were all treated with mycophenolate mofetil and in whom high mycophenolic acid (MPA) trough levels were found. High MPA levels may reflect over-immunosuppression resulting in infectious complications.