Tuesday, January 6, 2009

Renal Revascularization: The Astral Trial

One of the important studies released at Renal Week 2008 was the ASTRAL Trial (Angioplasty and STent for Renal Artery Lesions). This is the largest trial ever done on renal angioplasty. This seems like one my constant battles with cardiologists. I get a consult a month regarding whether patients should get a renal agioplasty done. I am almost always fighting against this based on prior information which showed marginal improvements in blood pressure control with the therapy and no change in the level of kidney function. However this data was questionable due to a high cross-over rate (i.e. 22 of the 28 patients initially randomized to drug therapy alone underwent angioplasty after 3 months).
This shows that the 806 patients randomized to ASTRAL dwarves all of the previous work on the subject. (source)

ASTRAL was billed as the definitive study to determine if angioplasty and stent preserved renal function, improved blood pressure, prevented hospitalizations, or reduced CV mortality. Patients were followed for 27 months. The enrolled cohort is representative of that are typical candidates for renal revascularization. Here are the graphs from the Investigator Newsletter:


The bulk of patients had moderately severe renal disease. It is important that they did not select patients too late in the disease where revascularization may be too late to save the kidney. Similarly you wouldn't wat to intervene too early where the splay between the groups may take longer than 27 months to materialize.

The average GFR was 40 mL/min.

Of note: if you just looked at patients with an initial GFR<25, size="4">Length

The fact that the affected kidney size was pretty good goes against the potential criticism that they were revascularizing too late after permanent infarction and scarring has ocured.

Most of the patients had severe stenosis, a high grade that if found during a diagnostic angiogram would be followed by an intervention.

  • 93% of interventions included use of a stent.
  • The mean stenosis was 76%

At follow-up, no difference in creatinine, blood pressure, time to first renal event, or mortality (p = ns for all outcomes)

The authors emphasized that there was no benefit for the entire cohort but they feel that the therapy is likely helpful for some subset of the population. I agree, like every nephrologist, I have seen patients have dramatic improvements in renal function following angioplasty for RAS. With the immense ASTRAL database it will be exciting to see if the authors can tease out which subgroups benefit from this technology.

Despite having seen multiple patients benefit from renal artery angioplasty I have remained a skeptic of the technology. Part of this comes from the older flawed and small trials and partly due to the ineffectiveness of cardiac angioplasty to help patients except in regards to reducing angina (a condition that doesn't have a renal analog) or in patients having an active infarct.
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