The Cardiovascular Outcomes in Renal Atherosclerotic Lesions (CORAL) trial likely will provide the first definitive evidence on the benefits of renal stenting, according to Julio Palmaz, MD, University of Texas.

"The most important thing today is deciding whether intervention is truly worthwhile, based on comparing it with medical management," Palmaz explained at an April 1 session of the 2005 Society of Interventional Radiology (SIR) meeting in New Orleans. Palmaz is credited for inventing the first commercialized stent in the l980's.

The three previous studies comparing renal intervention and medical therapy have been compromised by "design problems" and biases, according to Palmaz. "The CORAL trial probably will answer the questions that we have [and] be enormously important - supportive or not of intervention."

Initiated in April 2004, NIH-funded CORAL is a multicenter, randomized trial comparing optimal medical therapy with medical therapy plus renal artery stenting in patients with renovascular hypertension.

The study will enroll 1,080 patients across roughly 100 clinical sites. Unlike previous trials that have used blood pressure as a surrogate endpoint, CORAL will track event-free survival from cardiovascular and renal adverse events.

Hypertension is a common byproduct of renal artery stenosis. It can lead to renal dysfunction and development of left ventricular hypertrophy, culminating in adverse clinical events and, ultimately, death.

"What is the level of evidence on survival in cardiovascular risk-reduction after renal artery stenting?" Timothy Murphy, MD, Rhode Island Hospital, asked rhetorically. "There is none. And that is the whole purpose of the CORAL study; we're trying to accumulate that data."

The trial also should elucidate the prevalence of restenosis with renal stenting. "Are we getting any better? That's hard to say," Chet Rees, MD, Baylor University observed.

In a 1999 angiographic study, the restenosis rate up until that point was about 23%. Current stents yield a restenosis rate of roughly 20% at one year. Whether such figures represent a significant improvement in restenosis is undetermined, Rees says.

The ambiguity is compounded by the difficulty of detecting restenosis, "made more difficult by lack of a powerful non-invasive imaging modality," he said.

"Reports of long-term clinical results [to date] give no real information about patency rates, and such information can only be gleaned from well-controlled studies that carefully apply reliable imaging studies to the study population," Rees argued.

Although the clinical efficacy of the procedure remains in question, the annual volumes of renal artery angioplasty and stent placement increased 140% in 2000 compared with 1996, according to Murphy.

Meanwhile, "the potential risks of renal artery interventions, especially cholesterol embolization," have been "under-recognized and under-reported," Thomas Sos, MD, New York Presbyterian, asserts in a 2005 SIR supplement.

He goes on to propose that "the serious potential complications do not justify the treatment of incidentally-discovered, mild-to-moderate asymptomatic and not fully evaluated renal artery stenosis."

Drug-eluting stent technology, which has demonstrated success in coronary vessels, may represent a promising innovation within the renal intervention segment, as well, Rees suggests. While results from the 2003 GREAT trial comparing bare-metal stents to drug-eluting stents seem to favor the latter, Rees contends that a larger study is needed to further demonstrate the benefit.

CORAL will use J&J/Cordis' AngioGuard distal protection device. Currently, no marketed distal protection system is indicated for the capture of emboli during renal intervention.

Both Boston Scientific's FilterWire and Medtronic's GuardWire are approved for use in saphenous vein bypass grafts. Abbott expects to launch its Emboshield system by June for carotid stenting. Guidant's Rx Accunet is the only distal protection device currently approved for that indication, but AngioGuard is primed for debut after receiving an approvable letter in August (¹ [A#01300360001], p. 3).

CORAL Renal Trial To Show Risks, Benefits Of Stenting Over Drugs

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