It's All in the PROBIO: 12-month Results of the Nitinol Astron Stent in Iliac Artery Lesions 

Multiple stents are currently on the market for use in treating iliac atherosclerotic occlusions, but the optimal system remains to be determined. Burket et al. present the results of a prospective registry evaluating the safety and efficacy of the Astron stent (Biotronik; Bulach, Switzerland), a new amorphous silicon carbide (PROBIO)-coated nitinol self-expanding stent, in treatment of iliac occlusive disease. The PROBIO coating reduces metal ion release, which decreases stent thrombogenicity and promotes endothelialization. 161 patients underwent stent placement at 30 sites, of whom 145 patients completed 12-month study follow-up. The patient demographics and comorbidities as well as iliac lesion characteristics were comparable with other similar stent studies. The primary endpoint, a composite major adverse event (MAE) rate, including 30-day all-cause mortality, 12-month target lesion revascularization (TLR) rate, and 12-month index limb amputation, demonstrated a MAE rate of 2.1%, which was well within the performance goal of 15% (determined based on results of prior similar stent studies). The secondary outcomes included primary patency rate at 12-months (89.8%), freedom from target vessel revascularization (97.9%), freedom from bypass or amputation at 12-months (100%), and acute and 30-day technical success rates (95% for both metrics). ABI increased by a mean of 0.23 (p<0.001) and 6-minute walk increased by a mean of 158 feet (p<0.001) after stenting. Technical adverse events occurred in four cases, including uneven stent expansion (n=2), stent misplacement (n=1), and failure to deliver the stent at the intended site (n=1).

Commentary

The results of this prospective registry demonstrated promising efficacy and a favorable safety profile for the Astron stent in treating iliac occlusive disease. Although the 12-month composite MAE of 2.1% was similar to the range of results seen in other stent models (2.2-7.5%), direct comparisons were hampered by heterogeneity in MAE score definition between studies, and additional studies (ideally prospective randomized controlled trials with standardized endpoints) are necessary to elucidate the optimal stent device for iliac occlusive disease. Given known durability of iliac stenting and previous studies with freedom of 92% at 48 month2, long term outcomes beyond 12-months will also be important to determine durability of this stent, and may provide additional clarification on the potential real-world benefits of silicon carbide-coating versus non-silicon carbide coating for iliac arterial stenting. In the discussion, the authors referred to the CLEVER trial, which demonstrated similar efficacy between supervised exercise and stenting, a finding which raises fundamental questions regarding the risk and benefit ratio of endovascular intervention in these patients. These results are an important consideration for future iliac occlusive disease study designs, which may need to not only compare outcomes between multiple stent models, but also against supervised exercise testing, to best define the optimal treatment paradigm.

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1. Burket MW, Brodmann M, Metzger C, Tan K, Jaff MR. Twelve-Month Results of the Nitinol Astron Stent in Iliac Artery Lesions. J Vasc Interv Radiol 2016; 27: 1650-1656.

2. Sabri SS, et al. Outcomes of covered kissing stent placement compared with bare metal stent placement in the treatment of atherosclerotic occlusive disease at the aortic bifurcation. J Vasc Interv Radiol 2010; 21: 995-1003.

Post Authors:
Jeffrey Forris Beecham Chick, MD, MPH, DABR
Assistant Professor of Vascular and Interventional Radiology
Vice Quality Assurance and Safety Officer
University of Michigan Health Systems

James X. Chen, MD
Resident in Radiology
Hospital of the University of Pennsylvania