Cardiovascular Impact of Atherosclerotic Renovascular Disease

Renal artery stenosis is commonly atherosclerotic in origin, and its incidence increases with age. Decreased renal perfusion causes renal ischemia, which activates the renin-angiotensin-aldosterone system and increases a variety of inflammatory and pro-fibrotic cytokines. This results in the development of hypertension and a decline in renal function. Unfortunately the finding of renal artery stenosis does not always imply the presence of renal ischemia. Several randomized controlled trials have failed to demonstrate any benefit to renal artery revascularization over medical treatment with antihypertensive and lipid-lowering medications in regard to either blood pressure control or renal outcomes. All these trials have been faulted for including low-risk subjects who would not be expected to benefit from revascularization. It is clear that the majority of patients with renal artery stenosis can be treated with medical therapy alone. The question is how to identify those patients who would benefit from revascularization. High-risk patients include those with resistant hypertension, unexplained worsening renal function, asymmetric renal size, and recurrent episodes of flash pulmonary edema. Those individuals should be evaluated by noninvasive imaging techniques. If a greater than 70% stenosis is found, renal arteriography should be performed. It is important to recognize, however, that even if a greater than 70% stenosis is confirmed on arteriography, this does not necessarily indicate the presence of renal ischemia. Several newer methodologies including blood-oxygen-level-dependent MRI, dynamic contrast-enhanced MRI, and renal frame count have, in small studies, been shown to correlate with the presence of renal ischemia. Unfortunately, whether such techniques will actually be able to identify those patients who will benefit from revascularization will have to be demonstrated in larger trials. Until then the clinician will need to use his/her best judgment in the treatment of this disorder.