A new renal stent in the denervation era

Since Angioplasty and Stenting for Renal Artery Lesions (ASTRAL) trial was published [1], the medical therapy of atherosclerotic renal artery stenosis (RAS) has gained more impact in the management of resistant hypertension. It is unclear whether revascularization by means of stent is advantageous over optimal medical therapy. Moreover, in recent years, renal denervation has been introduced into the management of resistant hypertension worldwide [2], enthusiasm of interventionist’s interest shifted toward renal artery denervation. Either renal artery stenting or renal denervation, endpoints of intervention include blood pressure, kidney function, and mortality. Only difference is atherosclerotic renal artery stenosis (ARAS) has the significant stenosis in the renal artery. Bersin et al. [3] reported a prospective, multicenter single arm trial by using The Formula Balloon-Expandable Renal Stent. The primary endpoint was 9-month primary patency, on a per-stented artery basis. Patency was defined by duplex ultrasound as within-stent peak systolic velocity PSV> 225 cm/sec and/or a renal aortic ratio< 3.5. This study showed that the 9-month primary patency rate was 91.7%. Mean systolic blood pressure was significantly decreased at follow-up from 150 6 21 mm Hg at baseline to 141 6 21 mm Hg at 9 months (P1⁄4 0.003). No change in the number of antihypertensive medications per patient as compared to preintervention. But this data lacks the data of the significant stenosis. Before renal artery stenting is initiated, it is important to identify hemodynamically relevant RAS. Therefore, hemodynamic information must be obtained before patients were on the catheter table. For this purpose, Doppler ultrasound plays a central role in the diagnosis of hemodynamicaly significant RAS. Even though, they are using renal duplex finding to determine primary patency during follow up, there is no preintervention Doppler data. In this study, ostial renal artery lesions with a stenosis> 70% by visual angiographic assessment were made. But, what we have learned from ASTRAL trial, nonsignificant RAS lesions should not be treated. Therefore, not on visual assessment, either hemodymic or on site quantitative angiography should be made. Lack of preinterventional Doppler indices and/or tranlesion pressure gradient, we might make the similar mistake that was done by ASTRAL trial. This study showed the efficacy for blood pressure decrease by renal artery stenting, but blood pressure is characterized by array of spontaneous variation. That is blood pressure values vary markedly within a 24-h period. To judge the efficacy of blood pressure reduction, so called out of hospital blood pressure measurement is also important. To evaluate blood pressure lowering effect is not easy task compared to renal function, but in the year of 2013, out of hospital blood pressure evaluation is needed to conclude the impact to hypertension. This study met the objective performance goals of safety for new renal artery bare metal stents. And Duplex ultrasound-defined restenosis rate at 9 months showed objective performance goals [4]. But in the era of renal denervation, we are still not certain this stent gives the impact on hypertension in patients with atherosclerotic RAS. To clarify this uncertainty, high quality blood pressure evaluation is needed.