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Stenting atherosclerotic renal arteries: Time to be less aggressive

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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.


 

References

Author’s note: Atherosclerosis accounts for about 90% of cases of renal artery stenosis in people over age 40. 1 Fibromuscular dysplasia, the other major cause, is a separate topic; in this paper “renal artery stenosis” refers to atherosclerotic disease only.

Renal artery stenosis is very common, and the number of angioplasty-stenting procedures performed every year is on the rise. Yet there is no overwhelming evidence that intervention yields clinical benefits—ie, better blood pressure control or renal function— than does medical therapy.

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Earlier randomized controlled trials comparing angioplasty without stents and medical management showed no impressive difference in blood pressure. 2,3 The data on renal function were even more questionable, with some studies suggesting that, with stenting, the chance of worsening renal function is equal to that of improvement. 4

Two large randomized trials comparing renal intervention with medical therapy failed to show any benefit of intervention. 5–7 A third study is under way. 8

It is time to strongly reconsider the current aggressive approach to revascularization of stenotic renal arteries and take a more coordinated, critical approach.

RENAL INTERVENTIONS ON THE RISE

Renal angioplasty began replacing surgical revascularization in the 1990s, as this less-invasive procedure became more readily available and was shown to have similar clinical outcomes. 9 In the last decade, stent placement during angioplasty has become standard, improving the rates of technical success.

As these procedures have become easier to perform and their radiographic outcomes have become more consistent, interventionalists have become more likely, if they see stenosis in a renal artery, to intervene and insert a stent, regardless of proven benefit. In addition, interventionalists from at least three different specialties now compete for these procedures, often by looking at the renal arteries during angiography of other vascular beds (the “drive-by”).

As a result, the number of renal interventions has been rising. Medicare received 21,660 claims for renal artery interventions (surgery or angioplasty) in 2000, compared with 13,380 in 1996—an increase of 62%. However, the number of surgeries actually decreased by 45% during this time, while the number of percutaneous procedures increased by 240%. The number of endovascular claims for renal artery stenosis by cardiologists alone rose 390%. 10 Since then, the reports on intervention have been mixed, with one report citing a continued increase in 2005 to 35,000 claims, 11 and another suggesting a decrease back to 1997 levels. 12

HOW COMMON IS RENAL ARTERY STENOSIS?

The prevalence of renal artery stenosis depends on the definition used and the population screened. It is more common in older patients who have risk factors for other vascular diseases than in the general population.

Renal Doppler ultrasonography can detect stenosis only if the artery is narrowed by more than 60%. Hansen et al 13 used ultrasonography to screen 870 people over age 65 and found a lesion (a narrowing of more than 60%) in 6.8%.

Angiography (direct, computed tomographic, or magnetic resonance) can detect less-severe stenosis. Thus, most angiographic studies define renal artery stenosis as a narrowing of more than 50%, and severe disease as a narrowing of more than 70%. Many experts believe that unilateral stenosis needs to be more than 70% to pose a risk to the kidney. 14,15

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