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Renal Artery Stenosis: When Is Revascularization Warranted?

Renal Artery Stenosis: When Is Revascularization Warranted?

Q: My patient is a 66-year-old man with long-standing hypertension and atherosclerotic heart disease. During a recent coronary arteriogram, the cardiologist performed renal artery screening, which revealed a left renal artery stenosis. Renal artery angioplasty and stenting were recommended. Is this appropriate?

A: I believe that your concern is justified. Your patient is typical of the vast majority (more than 85%1) of patients referred for revascularization today. These patients usually have generalized atherosclerosis (including renal artery stenosis with preexisting hypertension) and generalized vascular disease (including coronary disease); in addition, they often have other associated metabolic problems, such as diabetes, dyslipidemia, and exogenous obesity.

Increase in renal artery angioplasty and stenting. In recent years it has become common for cardiologists to screen for renal artery disease during coronary angiographic procedures. Renal artery stenting is often performed in patients who have only mild or moderate renal artery stenosis—and in some cases no measurable gradient across the area of stenosis. Between 1996 and 2000, the use of percutaneous procedures to treat atherosclerotic renal artery disease increased by more than 60% in Medicare beneficiaries alone.2 With the exception of a few specific scenarios, the available data do not provide clear justification for this increase.1

Risks of endovascular procedures. Optimal management of atherosclerotic renal artery stenosis remains a matter of great controversy despite a large and growing number of clinical reports as well as uncontrolled clinical trials and a few controlled trials; the results of neither the controlled nor uncontrolled trials provide evidence of clear benefit from endovascular stenting procedures. Moreover, the complications associated with endovascular procedures performed on renal arteries can be significant. It has been estimated that 8% to 10% of patients may experience severe complications, including hemorrhage, vessel dissection, kidney perforation, or vessel thrombosis.

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Any instrumentation of the abdominal aorta or renal artery poses the risk of atheroembolism, which may occur during any phase of the procedure. Rarely, the results of peripheral or renal artery embolism can be devastating. Recent studies of protection devices placed distal to the stent to limit the risk of embolic debris during these procedures have had mixed results.

Management of risk factors for atherosclerosis. Atherosclerotic renal artery stenosis is one manifestation of generalized atherosclerosis in older patients, and it is not known whether it contributes to hypertension or renal insufficiency in this population. In these older patients, multiple risk factor control is critical. If hypertension is present, it should be treated aggressively; often, 2 or 3 medications will be required to achieve blood pressure control. Low-dose aspirin can be appropriate, and certainly statins can be beneficial in patients with dyslipidemia. In addition, there is evidence to support the beneficial vascular effects of statins in these older patients. 3,4 Obviously, it is important to encourage patients who are obese to lose weight and to increase daily exercise. Patients with type 2 diabetes should receive aggressive treatment to achieve glucose control.

Recommended imaging studies. In patients whose hypertension is controlled and who have normal or stable renal function, there should be no urgency to pursue diagnostic studies for renal artery stenosis. When evaluation is indicated, I recommend MRI and/or CT angiography. Both technologies provide excellent imaging of the renal arteries, although their use can be associated with complications. Duplex imaging of the renal arteries is also available but the results are highly techniciandependent.

Indications for endovascular procedures. The presence of a lesion is not necessarily an indication for an intervention. The only clear indications for intervention in a patient with renal artery stenosis are:
•Refractory hypertension.
•Progression of renal dysfunction because of large vessel disease.
•Recurrent episodes of congestive heart failure (flash pulmonary edema).

A number of carefully controlled clinical trials that compare vascular renal artery interventions with aggressive medical therapy are currently under way.5-7 Hopefully, the results of these will help clarify the risks and benefits of intervention in this growing elderly patient population.

References

REFERENCES:
1. Textor SC. Renovascular hypertension in 2007: where are we now? Curr Cardiol Rep. 2007;9:453-461.
2. Murphy TP, Soares G, Kim M. Increase in utilization of percutaneous renal artery interventions by medicare beneficiaries, 1996-2000. AJR. 2004;183:561-568.
3. Nicholls SJ, Tuzcu EM, Sipahi I, et al. Statins, high-density lipoprotein cholesterol, and regression of coronary atherosclerosis. JAMA. 2007;297:499-508.
4. Collins R, Armitage J, Parish S, et al; Heart Protection Study Collaborative Group. MRC/BHF Heart Protection Study of cholesterol-lowering with simvastatin in 5963 people with diabetes: a randomised placebo-controlled trial. Lancet. 2003;361:2005-2016.
5. Cooper CJ, Murphy TP, Matsumoto A, et al. Stent revascularization for the prevention of cardiovascular and renal events among patients with renal artery stenosis and systolic hypertension: rationale and design of the CORAL trial. Am Heart J. 2006;152:59-66.
6. Mistry S, Ives N, Harding J, et al. Angioplasty and stent for renal artery lesions (ASTRAL trial): rationale, methods and results so far. J Hum Hypertens. 2007;21: 511-515.
7. Scarpioni R, Michieletti E, Cristinelli L, et al. Atherosclerotic renovascular disease: medical therapy versus medical therapy plus renal artery stenting in preventing renal failure progression: the rationale and study design of a prospective, multicenter and randomized trial (NITER). J Nephrol. 2005;18:423-428.

 
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