Renal in-stent restenosis challenges interventionalists

The 16% to 40% rate of renal artery in-stent restenosis represents a significant therapeutic dilemma. While several interventional treatments are in use, a consensus on the best technique remains undefined.

Repeat balloon angioplasty is the veteran treatment for renal artery in-stent restenosis (ISR). Studies of cutting balloon angioplasty date back to 2001, and Munneke et al concluded it was better than conventional balloon angioplasty (J Vasc Interv Radiol 2002;13: 327-331).

Brachytherapy for ISR has moved from the heart to the kidneys. The studies there are few but promising, according to Dr. Christopher D. Jahraus, a radiation oncologist at the University of Kentucky (J Invas Cardiol 2004;16:224-228).

Dr. Thomas Albrecht and colleagues at Charite University in Berlin had previously shown that an intra-arterial injection of Paclitaxel dissolved in a contrast medium inhibited in-stent restenosis in the internal iliac and popliteal arteries of pigs. At last year's RSNA meeting, they reported that Paclitaxel-coated balloon-expandable stents have a similar effect. The researchers concluded that this approach might be suitable in various vascular territories in humans.

Gene therapy may also play a role. Dr. Xiaoming Yang and colleagues at Johns Hopkins University reported at the same RSNA meeting that intravascular MR/radiofrequency heating offers the potential to enhance gene therapy of in-stent restenosis. The investigators found that femoral/iliac arteries of pigs treated with a vascular endothelial growth factor (VEGF) fared better than untreated arteries. And within the VEGF group, those treated with MR/RF heating showed less in-stent restenosis than those not heated.

Another cardiac treatment mi-grating south is excimer laser renal angioplasty (ELRA). This technique, which shoots bursts of ultraviolet light, shows promise but needs long-term outcomes data, said Dr. David E. Allie, director of cardiothoracic and endovascular surgery at the Cardiovascular Institute of the South in Lafayette, LA.

Allie and colleagues performed ELRA in 44 patients with more than 60% renal artery ISR. He reported the study at the 2005 Society of Interventional Radiology meeting in April. The group recorded a 97% technical success rate. Patients' arterial pressure gradients dropped, on average, from 30 mm Hg to 4 mm Hg. In-stent restenosis decreased from a mean 78% to 10%. Four patients developed ISR at six months, but they remained restenosis-free for the next six months after repeat ELRA without stenting.

Early in the trial, nearly 14% of patients required a new stent inside an existing one, a procedure known as a stent sandwich. As interventionalists gained experience with ELRA, the stent sandwich rate dropped to less than 10%, Allie said.

It may be years before interventionalists agree on a definitive treatment for renal artery ISR. Some researchers have said the answer will be something entirely new rather than a tweaking of procedures that don't really work.