Infrapopliteal Stenting

Early data and experiences with a promising option for preventing amputation.

By Thomas Rand, MD
 

In 1998, endovascular treatment of the infrapopliteal arteries was still cited as the "forgotten region."1 Percutaneous transluminal angioplasty (PTA) has been increasingly and successfully applied since then, with promising results.2,3 Stenting of the infrapopliteal arteries, however, was restricted for a long time to case reports or anecdotal references. With the current development of new stent designs with promising features, much interest has been given to the question of how these stents will perform in infrapopliteal arteries.

The background of these considerations is easy to understand. Based on the TransAtlantic Inter-Society Consensus (TASC) document, patients with critical limb ischemia (CLI) (Fontaine class III and IV corresponding to Rutherford-Becker category 4 to 6), are defined as having a clinical status in which ulceration, gangrene, or rest pain of the lower limbs are caused by peripheral arterial occlusive disease. It is anticipated that in this patient population, a major amputation will also be required within 6 months to a year in the absence of significant hemodynamic improvement.

An increasing amount of diabetic patients with a high incidence of vascular disease are presenting with CLI, which can significantly limit their quality of life (QOL).4 Amputation does not only constitute a personal tragedy, it is also associated with a high economic cost in lost wages, disability, and the potential need for nursing home care. The use of a more aggressive approach to infrapopliteal disease with PTA and possibly stenting may permit a lower level of amputation and improved QOL.

THE ROLE OF STENTS
It has become obvious that a unique approach is needed for lower-limb arteries, and that stents must be developed with properties that fit the special demands of lower-limb arteries. The stents used in initial investigations had already been proven effective in arteries of similar sizes (ie, in the coronary arteries).

Siablis et al compared sirolimus-eluting stents (Cypher, Cordis Corporation, a Johnson & Johnson company, Miami, FL) versus bare-metal stents for bailout after suboptimal infrapopliteal angioplasty for CLI.5 Six-month primary patency was achieved in 68.1% of lesions treated with bare-metal stents versus 92% of lesions treated with the drug-eluting stents. No cases of stent deformation or fracture were reported. The proportion of patients who did not have rest pain at 6 months was 81.5% in those treated with bare-metal stents and 92.3% in patients treated with the Cypher stent. No major amputations were observed in either group and increasing arterial flow permitted a lower level of amputation in many patients. The 6-month minor amputation rates were 17.2% and 3.4%, respectively.

In this study, stents were employed only in a bailout setting in case of suboptimal angioplasty or severe dissection; the lesions treated were short (mean length, 1.3-1.4 cm). The short-term effect of sirolimus-eluting stents has been demonstrated in the SIROCCO I study, but it was not obvious in longer time period observations (SIROCCO II).6,7

Scheinert et al presented data from a randomized study comparing PTA of infrapopliteal lesions versus drug-eluting stents (DESs) and found significantly better results in the DES group, with a patency rate of 84% in the stent group versus 53% in the PTA group at 6 to 12 months (Figure 1).8

Apart from drug-eluting stents and bioabsorbable stents, which will be reported separately in this issue of Endovascular Today, there are published data about stent application below the knee.9 In a randomized, prospective study, we investigated the patency of passive coated stents in infrapopliteal arteries. The Carbostent (Sorin Biomedica, Modena, Italy), has a carbon coating designed to prevent thrombus formation. The device has already been used in coronary applications, where it revealed a 6-month restenosis rate of 11%.10 The design of the Carbostent is based on a thin (0.5 nm) carbon film with a polycrystalline structure. The Carbostent is balloon-expandable with a small crossing profile, which permits delivery through a long, 4-F system using a .014-inch guidewire. It is a tubular stainless stent with multicellular architecture. Two sides of the cell have the configuration of omega links.

In our study, interventional therapy was performed on 95 lesions in 59 patients, which were treated by either PTA (53 lesions) or stent application (42 lesions). From this cohort, a follow-up evaluation was performed in 31 patients with 57 lesions (32 PTA, 25 stenting) at 6 months (conventional and/or CT angiography). The median lesion length was 2.4 cm (range, 0.5-3 cm). This pilot study was done to provide basic data for the planning of a larger multicenter trial (Figures 2 through 4).

The criteria for inclusion were (1) patients with chronic CLI in the stage III and IV Fontaine classification, (2) patients with isolated stenosis >70% or occlusion of the tibial arteries, (3) patients with up to three lesions, and (4) lesions that were up to 3 cm with a cumulative lesion length of <9 cm, including the tibial-peroneal trunk, anterior and posterior tibial arteries, or the peroneal artery.

The 6-month cumulative patency probability was 83.7% for stent application and 61.1% for PTA using 70% as critical restenosis. The results were statistically significant (P=.02). For a threshold of 50% (subcritical restenosis), the corresponding data were 79.7% for stent application and 45.6% for PTA (P=.2), respectively, in both cohorts. The data from this randomized pilot study demonstrate that the 6-month follow-up patency rates are higher with stents that are less than 3 cm long. With regard to limb salvage, one minor amputation was performed in a patient who had undergone PTA, and one minor and one major amputation were performed in patients who underwent stent placement. One limitation of the study was the relatively high number of patients lost to follow-up: two patients died, one patient underwent major heart surgery and could not be followed, and 15% were lost to follow-up.

Our ongoing multicenter study will provide more reliable results with regard to the amputation rates and to the potential impact of the Carbostent for patients with CLI in the infrapopliteal distribution.

CONCLUSION
This first randomized series investigating the use of stents below the knee shows early promising results in patients with CLI. In this series, the use of stents was shown to be superior to PTA alone, but one major question has not been answered: Will stents have an influence on the amputation rate? To obtain relevant data for this question, it will be necessary to investigate a larger number of patients. Therefore, an international multicenter randomized study is underway, which answers several questions, including outcomes in CLI.

We are now at a point at which we know that we can successfully treat lower-limb lesions in CLI using an endovascular approach. Our primary target patient population is diabetic patients, and our main goal should be to prevent or lower the level of amputation. However, the effectiveness of the interventional treatment itself is not the only component that requires our attention; there is evidence that many amputations are performed without having evaluated all possible options.11 Therefore, we must start at the very beginning and work to improve the quality of the diagnostic evaluations that are performed, as well as expanding the knowledge of available treatment options among referring physicians.

Health care costs will also likely be reduced as a result of decreasing the number of amputations being performed, a trend that will result from the availability of endovascular alternatives. Finally, we should be aware of how dramatically the QOL in patients with CLI will be improved if we can prevent or lower the level of amputation in order to preserve their ability to ambulate, and ultimately, their QOL.

Thomas Rand, MD, is Professor of Radiology, Department of Clinical Angiography and Interventional Therapy, University of Vienna, Austria. He is a paid consultant to Sorin. Dr. Rand may be reached at +43 1 40400 5802; thomas.rand@meduniwien.ac.at.

 

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About Endovascular Today

Endovascular Today is a publication dedicated to bringing you comprehensive coverage of all the latest technology, techniques, and developments in the endovascular field. Our Editorial Advisory Board is composed of the top endovascular specialists, including interventional cardiologists, interventional radiologists, vascular surgeons, neurologists, and vascular medicine practitioners, and our publication is read by an audience of more than 22,000 members of the endovascular community.