Tag: renal artery stenosis

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Renal stents for preservation of renal function with atherosclerotic renal artery stenosis

The annals has an article this week on renal stents and again they fail.

Stent Placement in Patients With Atherosclerotic Renal Artery Stenosis and Impaired Renal Function

They randomized 140 patients with GFR <>50% stenosis (CT angio, MRA or digital subtraction angiography) with in 1 cm of the origin of the renal artery. They also excluded patients with uncontrolled blood pressure (>140/90) this was done because if patients randomized to medical management developed uncontrollable blood pressure they could cross over and receive a stent.

The end point was a persistant 20% reduction of GFR by Cockcroft-Gault for more than a month.

Results: No significant difference between the two treatment strategies.

The Kaplan-Meier curves confirm this. The top graph is the primary outcome and the bottom graph is primary outcome plus death:
Renal angioplasty resulted a variety of complications:

Two patients in the stent group died of procedure-related causes within 30 days after stent placement. In 1 of the patients, embolization of a perforated renal artery was required; the patient subsequently developed pulmonary edema and needed mechanical ventilation, and died of a massive ischemic stroke 3 days later. The second patient had perforation of a renal artery branch; the artery was embolized, but despite re-intervention, the patient went into hypovolemic shock and experienced the acute respiratory distress syndrome, and died of multiorgan failure after 1 week.

The most common complications after stent placement were minor and mainly consisted of hematoma at the puncture site (11 patients [17%]). In 1 of these patients, secondary infection in the groin required surgical reconstruction. The patient thereafter developed end-stage renal failure, pulmonary edema, and heart failure and died 6 months after the procedure. In 2 other patients, stent placement was complicated by false aneurysm of the femoral artery. Injury to the kidney or renal artery occurred in 5 patients; however, this was never associated with loss of renal function and additional intervention was never required.

One patient in the stent group who had repeated angiography required permanent dialysis after cholesterol embolism.

So another negative trial of renal artery revascularization. We are still waiting for the publication of ASTRAL, a much larger and more definitive trial. CORAL is another trial which is ongoing and will shed further light on this subject.

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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:

GFR

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.

Stenosis
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%

Results:
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.