ASTRAL Finds No Benefit of Revascularization Over Medical Therapy Alone for Renal-Artery Stenosis

Reed Miller

November 11, 2009

November 11, 2009 (Birmingham, United Kingdom) — The Angiography and Stenting for Renal Artery Lesions (ASTRAL) trial found "substantial risk but no evidence of worthwhile clinical benefit" from percutaneous revascularization of renal arteries with atherosclerotic disease, according to trial authors Dr Keith Wheatley (University of Birmingham, UK) and colleagues [1].

"Since endovascular interventions are associated with substantial morbidity, inconvenience, and cost, with little apparent benefit, the widespread use of such procedures outside of clinical trials can now be questioned," Wheatley et al conclude. "A related implication is that there seems to be little value in screening asymptomatic patients who have atherosclerosis and chronic renal disease or hypertension for evidence of renovascular disease."

According to the five-year follow-up results, published in the November 12, 2009 issue of the New England Journal of Medicine, ASTRAL found a statistically insignificant (p=0.06) difference in renal-function level favoring percutaneous revascularization vs medical therapy alone and no statistically significant differences in absolute serum creatinine at any point in the 60 months of follow-up. Systolic blood pressure, renal events, major cardiovascular events, and death were similar for both groups.

Revascularization was linked to serious complications, including two deaths and three amputations, in 23 patients. There were 238 cardiovascular events in 141 patient in the revascularization group and 244 events in 145 patients in the medical-therapy group. There were 103 deaths in the revascularization group and 106 in the medical-therapy group.

The 57-site study randomized 806 patients with atherosclerotic renovascular disease either to optimal medical therapy plus percutaneous revascularization or optimal medical therapy alone. The primary end point was renal function, as measured by the reciprocal of the serum creatinine level, which has a linear relationship with the rate of creatinine clearance, a key measure of renal impairment. Patients randomized to revascularization were treated with angioplasty alone or with a stent, as determined by the local practitioner. Renal-protection devices were not used. The medical therapy for both groups was determined by local protocols and typically included statins, antiplatelet agents, and blood-pressure–control therapy.

Who Should Be Revascularized?

Previous nonrandomized studies suggested that revascularization improves renal function in approximately 25% of patients with atherosclerotic renovascular disease. ASTRAL also showed improvement in about a quarter of the revascularization patients, but there were no statistically significant differences in creatinine level between the revascularization and the control groups, "which shows how benefits that could erroneously be ascribed to revascularization in an uncontrolled study may actually be due to chance fluctuations or effective medical therapy."

The authors acknowledge a limitation of the study population. Patients were enrolled in the trial only if their own physician felt uncertain whether revascularization would provide benefit. "The principle of equipoise requires such uncertainty for the ethical conduct of the trial. However, this enrollment criterion leaves unresolved the question of whether some patients with renovascular disease who did not meet the eligibility criteria might have benefited from revascularization."

Wheatley et al write that despite the absence of clinical evidence, the consensus among physicians is that certain patients with severe renal-artery stenosis, such as those with acute kidney injury or "flash" pulmonary edema, should be revascularized. So these patients were unlikely have been referred for consideration in ASTRAL. "The trial population was nonetheless intended to be representative of patients undergoing revascularization in clinical practice."

Commenting on ASTRAL, Dr William Boden (Buffalo General Hospital, Buffalo, NY) told heartwire that "critics will attempt to portray this as an unrepresentative group among those currently undergoing renal-artery stenting. Usually, in our randomized trials, we tend to enroll lower-risk patients, but in this study, because they were not considered patients who might benefit from stenting, they actually may be sicker. In general, one would expect sicker patients to benefit more from revascularization than low-risk patients."

Boden believes a much larger trial, designed and powered for clinical end-point reduction, should be conducted to clarify which patients may benefit from renal revascularization. The study should compare intervention vs optimal medical therapy in renal-artery-stenosis patients whose doctors believe they could benefit from revascularization.

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