Cath Lab Digest

Stenting of the renal artery is now the procedure of choice in treating obstructive atherosclerotic renal artery disease. Unfortunately, restenosis remains the Achilles’ tendon of this percutaneous therapy, and ranges from 15–25%.¹ Several predictors of restenosis following stenting of the renal arteries have been suggested, including small vessel size^1,2 (typically < 4.5 mm), length of stented segment,² time to evaluate for restenosis,^1,3 smoking,¹ the use of gold-coated stents³ and bilateral renal artery disease.³ Although treating restenosis with repeat balloon angioplasty might offer some improved secondary patency rate, the overall recurrence rate remains high.⁴ Ongoing studies to evaluate drug-eluting stents (DES) in the renal arteries might offer a novel way to address this issue; however, at present this therapy in the peripheral vasculature remains experimental and not available for clinical use. Also, most treated renal vessels are larger than the coronary arteries (> 4 mm), and therefore the application of currently existing coronary DES to the renal arteries is limited and its efficacy remains unclear.

Brachytherapy in the renal arteries might offer an effective treatment to restenosis in the renal vasculature. Early data suggest that it is safe and effective,^5,6 but studies have been small and non-randomized. The study by Kuchulakanti et al. adds another small observational series of brachytherapy cases to treat in-stent restenosis following stenting of the renal arteries. The data again is favorable, but given the small number of patients and the non-randomized design of this study, further validation will be needed before widespread application. Unfortunately, intravascular brachytherapy availability is now a problem, as industry has essentially given up on this technology to focus their research efforts on DES. Therefore, a randomized study of brachtherapy in the renal arteries is less likely to happen, and the application of this technology will remain limited, if even available.

It should be noted that in the study by Waksman et al. larger vessel sizes of > 5 mm were targeted for treatment. Restenosis in smaller vessels (< 4.5 mm) is substantially higher and might reach up to 40% on long-term follow up.¹ The applicability of brachytherapy in these small vessels is unknown. Currently, it is more tempting to treat these vessels with coronary DES, particularly because radial strength would not be a limiting issue following a previous treatment with a biliary stent in the same vessel. The effectiveness of this off-label approach to coronary DES is still unclear.

Restenosis in the renal vessels also appears to continue beyond the traditional period of 6 months that was seen in the coronaries. In fact, we have shown that restenosis can be demonstrated up to 22 months on follow-up, and therefore, we believe that long-term follow-up of renal arteries is essential to evaluate the durability of any new therapy.

An interesting approach to the use of intravascular brachytherapy in the study of Kuchulakanti et al. is the application of radiation prior to angioplasty, a reverse approach to its application in the coronaries. This technique appears to be effective in this small series with the use of a gamma source, but might also be effective with a beta source by overcoming the inability of beta particles to reach the lesion in larger vessels following angioplasty. Brachytherapy using a beta source is the only one currently available in the United States, and possibly for only a short period of time. Unfortunately, despite the encouraging results of this pilot study, brachytherapy is now considered a part of the interventional history books as a once-great idea that has been overshadowed by DES.