Stenting for atherosclerotic renal-artery stenosis: a blind alley?

Renal-artery stenosis, a common disease among persons older than 65 years,may result in hypertension, ischemic nephropathy, and multiple long-term complications [1]. Early studies [2] suggested that renal-artery angioplasty or stentingmay result in significant reductions in systolic blood pressure. However, the Cardiovascular Outcomes in Renal Atherosclerotic Lesions (CORAL) trial [3] recently presented a definitive test of the usefulness of renal-artery stents for moderately severe renalartery stenosis and made a conclusion that renal-artery stenting is no better than medical therapy alone in preventing clinical events. It seems that stenting for renal-artery stenosis after years of its clinical use hits a blind alley. However, pathophysiological changes after stenting include not only improvement in the diameter of the stenotic renal artery but also the tissues of and around the artery, particularly the sympathetic nerve fibers which lie in the adventitia of the renal artery (Fig.1). A recent research [4] demonstrated that balloon angioplasty can reduce the number of sympathetic nerve fibers of the renal artery. So this may be more than just a theoretical consideration. Renal-artery stenosis is characterized not onlybyactivationof the renin–angiotensin system, but also byheightened sympathetic drive [5] which contributes to the pathophysiology of numerous chronic cardiovascular diseases such as essential hypertension, heart failure, chronic kidney disease, diabetes and so on. Nowadays percutaneous catheter-based renal denervation (RDN) is emerging as a new, effective and safe approach to achieve sustained blood pressure reduction in patients with resistant hypertension which can decrease sympathetic activity by interrupting the afferent and efferent renal sympathetic nervous fibers located in the adventitia of the renal arteries by delivery of radiofrequency energy. Herein, we hypothesize that RDN on patients with prior renal stents may enhance the damages of renal sympathetic nervous fibers and reduce the sympathetic activities to a much lower level. However, renal-artery stenosis and prior renal stents are considered a contraindication in routine clinical practice of RDN due to technological unavailability and a worry of deterioration of stenosis. Nevertheless, one case report [6] explored and demonstrated the feasibility and potential effectiveness of the combination of RDN and renal stenting. What's more, a recent small animal study [7] proved that vascular brachytherapy which has been approved for the treatment of in-stent restenosis can also cause renal sympathetic nerve fibrosis while avoiding significant damage to the renal artery. All theseexplorationsmaybreak new ground of therapy with renal-artery stenosis.