Drug-Eluting Stents for the Superficial Femoral Artery Need More Study

By Sharon Worcester

BOSTON -- Drug-eluting stents haven't yet proven as effective for superficial femoral artery disease as they have for coronary artery disease, but the jury is still out on their potential, Dr. Michael R. Jaff said at a symposium sponsored by the American Heart Association.

"Restenosis has been nicely described and understood all the way down to the cellular level in the coronary arteries, and we believe that there are some similarities, although it's not identical, in the superficial femoral artery," said Dr. Jaff, medical director, the vascular diagnostic lab at Massachusetts General Hospital, Boston.

Although data offer support for this--the SIROCCO trial, for example, showed a nonsignificant trend toward lower rates of restenosis with drug-eluting vs. bare metal stents in the early posttreatment period--there is a great deal of study left to be done, he said.

Drug-eluting stents offer a solution to restenosis, preventing remodeling at the time of stent placement and soon after, and later preventing the development of neointimal proliferation and hyperplasia. Further, they provide targeted drug delivery, presumably with negligible systemic exposure, Dr. Jaff said.

But many challenges remain to be addressed when it comes to the use of drug-eluting stents in the superficial femoral artery, such as mechanical issues associated with the location of the superficial femoral artery. And many questions remain to be answered, such as which drugs are best to use with stents.

To date, the best available data are from studies looking at stents coated with sirolimus or its analogues, and with paclitaxel.

Both have shown promise. But the most recently reported data on sirolimus from SIROCCO showed at the 24-month follow-up there was no difference in restenosis rates compared with bare metal stents. This suggests that any early benefit may be lost over time. Paclitaxel is currently being studied in the DESTINY trial, a large-scale study that aims to enroll 1,000 patients.

Important areas for study regarding "the moving target" of drug-eluting stents for superior femoral artery disease include the identification of optimal drugs and drug concentrations for preventing restenosis in this location, the evaluation of the use of "topcoats" over the drug applied to stents to allow optimal drug delivery, and the analysis of the pharmacokinetics of stents, including interactions between the metal, the drugs, and any topcoat used.

Stent fractures are also a concern and require additional study regarding the potential of drugs themselves to increase fracture risk, and whether the multiple mechanical forces on this artery are too overbearing for long-term use of metal stents, Dr. Jaff said.

When asked to comment on this article, Dr. Mark D. Morasch, associate professor of surgery, Northwestern University Feinberg School of Medicine, stated: "Clearly hemodynamics differ between the coronary and the infrainguinal lower-extremity circulations. The atherosclerotic lesions that need treatment in the SFA are also more heterogeneous than those in the coronary arteries.

"These issues make it more difficult to study the effects of drug delivery in these vessels. Larger randomized trials may be necessary to determine whether the costs associated with drug-eluting stents will be worth it in the long run."