Stenting atherosclerotic renal arteries: Time to be less aggressive
ABSTRACTPercutaneous intervention has become very popular for treating atherosclerotic renal artery stenosis, as the use of stents has boosted the rate of technical success and as more cases are being discovered incidentally during angiography of the coronary or other arteries. Yet randomized trials indicate that the procedure does little in terms of controlling blood pressure and may actually harm as many patients as it helps in terms of renal function. Needed are better ways to predict which patients will benefit and better ways to prevent adverse effects such as atheroembolism.
KEY POINTS
- Two large randomized trials of intervention vs medical therapy showed negative results for intervention. A third trial is under way.
- Intervention is not recommended if renal function has remained stable over the past 6 to 12 months and if hypertension can be controlled medically.
- The best evidence supporting intervention is for bilateral stenosis with “flash” pulmonary edema, but the evidence is from retrospective studies.
- Stenosis by itself, even if bilateral, is not an indication for renal artery stenting.
RISK OF ATHEROEMBOLISM
While renal stenting yields improved technical success in the treatment of renal artery stenosis, it carries with it an increasingly common risk to kidney function: atheroembolism as the stent crushes the plaque against the vessel wall. This may lead to obstruction of the renal microvasculature, increasing the risk of irreversible damage to renal function.
Atheroembolic kidney disease can manifest as progressive renal failure occurring over weeks to months, commonly misdiagnosed as permanent damage from contrast nephropathy.55
Embolic protection devices, inserted downstream of the lesion before stenting to catch any debris that may break loose, have been developed to help address this problem.
Holden et al 57 prospectively studied 63 patients with renal artery stenosis and deteriorating renal function (undefined) who underwent stenting with an embolic protection device. At 6 months after the intervention, renal function had either improved or stabilized in 97% of patients, suggesting that many of the deleterious effects of stenting on renal function are related to atheroembolism.
The Prospective Randomized Study Comparing Renal Artery Stenting With or Without Distal Protection (RESIST) trial, in which renal dysfunction was mild and the GFR was not declining (average estimated GFR 59.3 mL/min), found contrary results.57 In a two-by-two factorial study, patients were randomized to undergo stenting alone, stenting with the antiplatelet agent abciximab (ReoPro), stenting with an embolic protection device, or stenting with both abciximab and an embolic protection device. Interestingly, renal function declined in the first three groups, but remained stable in the group that received both abciximab and an embolic protection device.
ANTIPLATELET THERAPY AFTER RENAL STENTING: HOW LONG?
We have no data on the optimal duration of antiplatelet therapy after renal stenting, and guidelines from professional societies do not comment on it.58 As a result, practice patterns vary significantly among practitioners.
While in-stent restenosis rates are acceptably low after renal stenting, the risks and side effects of antiplatelet therapy often lead to arbitrary withdrawal of these drugs. The effect on stent patency is yet to be determined.
FUTURE DEVELOPMENTS
Results of STAR and ASTRAL confirm the growing suspicion that the surge seen in the last decade in renal artery stenting should be coming to an end. We await results either from CORAL or possibly a post hoc analysis of ASTRAL that might identify potential high-risk groups that will benefit from renal intervention. And as embolic protection devices become more agile and suitable to different renal lesions, there remains the possibility that, due to lower rates of unidentified atheroembolic kidney disease, CORAL may demonstrate improved renal outcomes after stenting. If not, the search for the best means to predict who should have renal intervention will continue.
We know through experience that stenting does provide great benefits for some patients with renal artery stenosis. Furthermore, the clinical problem is too intriguing, and too profitable, to die altogether.
