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ASTRAL: No significant or sustained clinical benefit for kidney function with revascularization
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Revascularization was not associated with a significant improvement in kidney function in patients with atherosclerotic renovascular disease.
Researchers for the ASTRAL trial enrolled 806 patients with atherosclerotic renovascular disease in the study and randomly assigned them to undergo revascularization with medical therapy (n=403) or to receive medical therapy alone (n=403). The primary outcome measure was renal function as measured by the reciprocal of the serum creatinine level. They followed patients to five years.
Revascularization was attempted in 335 of the 403 patients (83%) and was deemed a technical success in 317 of the 335 patients (95%). The overall mean slope of the reciprocal of the serum creatinine concentration was –0.07×10–3 L/mcmol per year in the revascularization group vs. –0.13×10–3 L/mcmol per year in the medical therapy alone group (P=.06). The mean reciprocal of the creatinine level during the five years of follow-up was 0.09×10–3 L/mcmol higher in the revascularization group vs. the medical therapy group (95% CI, –0.02 to 0.20; P=.10). In a per protocol analysis, the researchers reported no difference in the primary outcome between the 317 patients who underwent revascularization and the 379 patients who received medical therapy only. There were no differences in mean systolic BP reduction between the study groups (P=.63), and a greater reduction in mean diastolic BP was reported in the medical therapy group (P=.03). There were also no significant differences between study groups for renal and CV events or for mortality.
“We found no evidence of a worthwhile clinical benefit in the initial years after revascularization in patients with atherosclerotic renal-artery stenosis,” the researchers wrote in the study. “The upper confidence limits for a benefit from revascularization with respect to renal function were below levels that would be considered clinically relevant.”
Wheatley K. N Engl J Med. 2009;361:1953-1962.
There are two important things to note for this study. The first is the lack of severe lesions in the patient population and the fact that the medical therapy group did much better than they would have, where historically you would have expected to see a certain number of patients who had renal failure. That did not happen in this trial because the lesions were milder than they had projected.
They also randomized 403 patients to the interventional group. Of those 403 patients, only 83% actually got the stent. They then analyzed the trial by intention-to-treat rather than by treatment received. They do not say why the 17% of patients who did not get stents did not receive them. That weakens the interventional side because if you count the 17% that never got a stent as having gotten a stent, it is hard to claim any benefit there.
I would be comfortable telling a group of doctors that there is no point in putting a stent in anybody without a severe blockage. That is essentially what this trial says, and on this we agree. If you read the summary, however, it almost sounds like you should never put a stent in a patient to save their kidneys. That is not what this trial measured. These results suggested that one should never put a stent in a patient with very mild blockage to save their kidneys, and I would agree with that. I would not agree that one should never put a stent in a patient to save their kidneys if the patient has a 99% blockage.
It is important these results be put in perspective. If primary care doctors and internal medicine doctors are hearing that stents are not good for renal failure, then they will have a more difficult time being able to discriminate the patients who really could benefit vs. those who may not. Mild lesions should not be treated with stenting, and that is the message that needs to be emphasized here. At the same time, physicians need to understand that there is still a role for interventional therapy in patients with the most critical blockages.
– Christopher J. White, MD
Chairman, Department of Cardiology
Ochsner Clinic, New Orleans