Drug-eluting stents for peripheral artery disease

Drug-eluting stents have significantly decreased the complication rate of coronary artery disease treatment.[1] They have also added significantly to health care costs.[1] Now stents with a drug coating are being tested in patients with peripheral artery disease (PAD).

The self expanding, flexible, nitinol (nickel titanium) Zilver®PTX™ stent is the size of a crayon.

Photo courtesy of Cook Inc.

What is peripheral artery disease?

PAD is similar to coronary artery disease in that fatty deposits build up in the arteries and block blood flow to the legs and feet. Reduced blood flow in the femoropopliteal artery, the major artery in the thigh, can cause leg pain with exercise (intermittent claudication) and can lead to skin ulcers, gangrene and amputation.

An estimated 4% of Canadians older than 40 have PAD; this number increases to 20% in people older than 75.[2]

Treatment

PAD is treated with regular exercise and medication to control risk factors.[2] However, at least 25% of patients require angioplasty treatment, where a balloon-tipped catheter is inserted through a small incision in the groin to enlarge the narrowed artery.[3]

Unfortunately, a frequent consequence of angioplasty is restenosis (re-narrowing) of the artery that has been opened.

Stents

Angioplasty can be combined with a stent, which is a wire mesh "scaffold" that remains in the artery to keep it propped open. Stent use for obstructive femoropopliteal artery disease is controversial. Several studies[2] have shown that long-term results with stent implantation are no better than angioplasty alone. Stents are currently recommended only when angioplasty results are suboptimal.[2]

Recently, two new drug-coated stents have been developed. These release small amounts of medication intended to help prevent tissue scarring, which can cause restenosis at the stent site. Not yet approved in any country, early data on their clinical use are emerging.

Sirolimus-coated stents for PAD

Cordis Corporation has reported the results of two small trials with their sirolimus-coated S.M.A.R.T.® Nitinol Self-expanding Stent. In the first trial enrolling 36 patients, the only statistically significant difference at six months was that patients who received sirolimus-coated stents had a larger femoral artery diameter compared with those who received uncoated stents. The restenosis rate at the stent site was lower in the sirolimus-eluting stent group; however it was not statistically significant, possibly due to the small sample size.[4]

A second trial with 57 patients found no statistically significant differences in six-month artery diameter or restenosis rates between patients with sirolimus-coated stents and those with uncoated stents.[5]

Paclitaxel-coated stents for PAD

The Zilver PTX, a paclitaxel-coated stent manufactured by Cook Incorporated, is now being evaluated in an international multi-centre clinical trial.[6]

Cost

The costs of the Zilver PTX and the sirolimus-eluting S.M.A.R.T. nitinol stents are unknown. It is also unknown if the cost of using drug-coated stents would offset additional costs of performing repeat procedures to treat restenosis.

References

[1] Mittmann N, et al. Economic evaluation of drug eluting stents [Technology report no 53]. Ottawa: Canadian Coordinating Office for Health Technology Assessment; 2005. Available: https://www.ccohta.ca/publications/pdf/272_drug_eluting_stents_tr_e.pdf.

[2] 2005 Canadian Cardiovascular Society Consensus Conference: peripheral arterial disease. Ottawa: Canadian Cardiovascular Society; 2005. Available: http://www.ccs.ca/download/draft_full_document_3_.pdf.

[3] Weinberger J, et al. Am J Ther 2005;12(2):186-91.

[4] Duda SH, et al. Circulation 2002; 106(12):1505-9.

[5] Duda SH, et al. J Vasc Interv Radiol 2005; 16(3):331-8.

[6] Cook to begin first international trial of a paclitaxel-eluting stent for peripheral artery disease [news release]. Angioplasty.org; 2005 May 3. Available: http://www.ptca.org/pr_cook/20050504.html.