Does stenting of severe renal artery stenosis improve outomes compared with medical therapy alone?
TRIALS OF STENTING VS MEDICAL THERAPY ALONE
Technical improvements have led to more widespread use of diagnostic and interventional endovascular tools for renal artery revascularization. Studies over the past 10 years examined the impact of stenting in patients with uncontrolled hypertension.
The STAR trial
In the Stent Placement and Blood Pressure and Lipid-lowering for the Prevention of Progression of Renal Dysfunction Caused by Atherosclerotic Ostial Stenosis of the Renal Artery (STAR) trial,9 patients with creatinine clearance less than 80 mL/min/1.73 m2, renal artery stenosis greater than 50%, and well-controlled blood pressure were randomized to either renal artery stenting plus medical therapy or medical therapy alone. The authors concluded that stenting had no effect on the progression of renal dysfunction but led to a small number of significant, procedure-related complications. The study was criticized for including patients with mild stenosis (< 50% stenosis) and for being underpowered for the primary end point.
The ASTRAL study
The Angioplasty and Stenting for Renal Artery Lesions (ASTRAL) study10 was a similar comparison with similar results, showing no benefit from stenting with respect to renal function, systolic blood pressure control, cardiovascular events, or death.
HERCULES
The Herculink Elite Cobalt Chromium Renal Stent Trial to Demonstrate Efficacy and Safety (HERCULES)12 was a prospective multicenter study of the effects of renal artery stenting in 202 patients with significant renal artery stenosis and uncontrolled hypertension. It showed a reduction in systolic blood pressure from baseline (P < .0001). However, follow-up was only 9 months, which was insufficient to show a significant effect on long-term cardiovascular and cerebrovascular outcomes.
The CORAL trial
The Cardiovascular Outcomes in Renal Atherosclerotic Lesions (CORAL) trial13 used more stringent definitions and longer follow-up. It randomized 947 patients to either stenting plus medical therapy or medical therapy alone. Patients had atherosclerotic renal artery stenosis, defined as stenosis of at least 80% or stenosis of 60% to 80% with a gradient of at least 20 mm Hg in the systolic pressure), and either systolic hypertension while taking two or more antihypertensive drugs or stage 3 or higher chronic kidney disease (glomerular filtration rate < 60 mL/min/1.73 m2 as calculated by the Modification of Diet in Renal Disease formula).
Participants were followed for 43 months to detect the occurrence of adverse cardiovascular and renal events. There was no significant difference in primary outcome between stenting plus drug therapy and drug therapy alone (35.1% and 35.8%, respectively; P = .58). However, stenting plus drug therapy was associated with modestly lower systolic pressures compared with drug therapy alone (−2.3 mm Hg, 95% confidence interval −4.4 to −0.2 mm Hg, P = .03).13 This study provided strong evidence that renal artery stenting offers no significant benefit to patients with moderately severe atherosclerotic renal artery stenosis, and that stenting may actually pose an unnecessary risk.
COMPLICATIONS OF RENAL ARTERY STENTING
Complications of renal artery stenting are a limiting factor compared with drug therapy alone, especially since the procedure offers no significant benefit in outcome. Procedural complication rates of 10% to 15% have been reported.9,10,12 The CORAL trial reported arterial dissection in 2.2%, branch-vessel occlusion in 1.2%, and distal embolization in 1.2% of patients undergoing stenting.13 Other reported complications have included stent misplacement requiring an additional stent, access-vessel damage, stent embolization, renal artery thrombosis or occlusion, and death.10,12
