Stenting evolves as treatment option for lesions in peripheral circulation

Percutaneous transluminal angioplasty is one of the most important tools for addressing disease in the arterial wall alone or in combination with in situ perfusion. Choosing the best method of treatment for patients with peripheral vascular disease is difficult, however, because findings comparing PTA with stents have been variable, and evidence of the utility of stent-grafts and drug-eluting stents is just emerging, according to speakers at an ECR state-of-the-art symposium on advances in peripheral arterial stenting.

Endovascular therapy involving PTA is considered the treatment of choice for single stenoses less than 3 cm in diameter in the iliac vessels. PTA is commonly performed on longer, single stenoses ranging in size from 3 to 10 cm, as well as on two stenoses and unilateral central iliac arterial occlusion, although no randomized clinical studies have demonstrated its effectiveness in such cases. In general, stenting is indicated for treating lesions in the iliac vessels when the degree of residual stenosis exceeds 30%, the mean pressure gradient is greater than 10 mm Hg, flow-obstructing disease or chronic occlusion is present, or reocclusion has occurred after PTA, said Prof. Dr. Johannes Lammer from Vienna.

A meta-analysis of studies assessing patency rates after PTA and stenting in the iliac vessels has revealed conflicting results, however. In a study of 228 patients, the difference in two-year patency rates following stenting and PTA was statistically significant; stenting achieved a 95% patency rate at two years compared with only 65% for PTA. But there was no significant difference in patency rates between primary PTA and stenting in a study of 297 patients; 71% of patients who underwent stenting and 70% of PTA patients had patent vessels after two years.

Patency rates were improved in patients who were switched to stenting after PTA failed. Iliac vessels were patent at one year in 92% of patients who underwent stenting after PTA failure, compared with 84% who had only PTA. According to Lammer, stenting improves treatment success when balloon angioplasty is unsuccessful, and endovascular therapy can achieve high rates of vessel patency: 80% to 90% at one year, and 65% to 75% at three to five years.

In the femoropopliteal vessels, endovascular treatment is considered for a single stenosis between 3 cm and 10 cm, a heavily calcified stenosis, or multiple stenoses, each of which measures less than 3 cm. Whether treated with PTA or stenting, patients with stenosis and claudication achieved similar patency rates, according to a meta-analysis published in 2001 as well as a randomized study. Stents have produced more favorable results in patients with severe disease. Patency rates were 60% for PTA and 74% for stents in patients with critical limb ischemia. Patency rates were 47% for PTA and 73% for stents in patients with occlusion.

Although evidence supporting the use of stent-grafts and drug-eluting stents is limited, some initial findings are encouraging. One-year patency rates were 91% in the iliac vessels and 79% in the femoropopliteal circulation in one study of the Hemobahn stent-graft. In the only study conducted to date in the peripheral vessels, the Sirolimus-eluting stent was more effective than the SMART stent in maintaining a minimal luminal diameter and a mean in-stent diameter. At six months, the minimal luminal diameter was 3.98 mm and the mean in-stent diameter was 5.02 mm in patients who received a Sirolimus-eluting stent compared with a mean luminal diameter of 3.49 mm and in-stent diameter of 4.58 mm in patients who had a base SMART stent. Interestingly, the restenosis rate was zero in the Sirolimus group and only 11.6% in the base SMART group.

"The 0% restenosis rate with the Sirolimus-eluting stent is very promising. The base SMART stent performed impressively well in the six-month and graft restenosis rates. We have never seen such a low restenosis rate with stenting," Lammer said.

According to a study conducted by Prof. Dr. Christoph Zollikofer from Kantonsspital Winterthur, Switzerland, there is no need to cover the full treated lesion with a stent in the peripheral blood vessels. When placed over the site of the most severe residual obstruction, a single stent between 10 mm and 17 mm appears to be sufficient. The study included 68 patients, 51 with claudication and 17 with critical ischemia, who had 68 lesions in the peripheral vasculature. The results demonstrated surprisingly good primary and secondary patency rates: 76% at one year and 69% at two years.