Absorbable Metal Stent Update
Encouraging data have led to new trial designs for this exciting potential treatment.
Recently, there has been increased interest in determining the feasibility of using biodegradable (absorbable) stents as a means to combat vessel recoil. The basic working principle of an absorbable stent is to mechanically prevent early vascular recoil in the short-term, to lose its rigid structure after the threat of recoil is eliminated in the mid-term, and to be completely absorbed in the long-term (Figure 1).
On August 10, 2005, Biotronik GmbH & Co. (Berlin, Germany) announced the completion of recruitment for the PROGRESS-AMS (Clinical Performance and Angiographic Results of Coronary Stenting With Absorbable Metal Stents) Study. According to the company, PROGRESS-AMS is a prospective, multicenter, consecutive, nonrandomized investigation of a total of 63 patients in eight international clinical sites, designed to evaluate the safety and efficacy of Biotronik’s Absorbable Metal Stent (AMS) system in the treatment of a single de novo lesion in a native coronary artery. The primary endpoint, defined as the combined clinical endpoint of cardiac death, nonfatal myocardial infarction, or ischemia-driven target lesion revascularization, will be measured at 4 months after stent placement. The results of this study will be used to assess the clinical possibilities of the AMS technology for future regulatory approval and market introduction.
On July 13, Biotronik announced the successful initiation of the AMS-INSIGHT 1 (BioAbsorbable Metal Stent Investigation in Chronic Limb Ischemia Treatment) Study to investigate the AMS for treatment of chronic limb ischemia. The AMS-INSIGHT 1 Study is a prospective, multicenter, randomized clinical trial aimed at assessing the safety and performance of the company’s AMS for the treatment of infrapopliteal lesions in patients with chronic limb ischemia. Patients treated with AMS will be compared with the results of a patient group treated with PTA alone. In total, 115 patients are planned for recruitment in 11 European centers with a follow-up planned at 1, 6, and 12 months. On June 30, 2005, Marc Bosiers, MD, Co-Principal Investigator of the study, successfully implanted a 3.5-mm-diameter stent with a 15-mm length in a patient.
The AMS-INSIGHT 1 Study has been initiated because of the results of an earlier, smaller experience that evaluated the 12-month results with use of the AMS. In the earlier experience, the investigators studied 20 patients (10 men; age range, 59 to 96 years; mean age, 76 years) who had below-the-knee critical limb ischemia (Rutherford Class IV to V) and who were undergoing angioplasty for high-grade (80% to 100%) atherosclerotic lesions in the proximal two thirds of one or more of the infrapopliteal arteries (Table 1). The mean length of the treated lesions was 11 mm (range, 2-20 mm), with an average reference vessel diameter of 2.7 mm (range, 2.5-3 mm) and a mean stenosis of 84% (range, 75-95%) (Table 2).
Procedural success was defined as angiographic success without serious adverse events before the arterial sheath was removed; primary clinical patency was defined as the absence of in-stent occlusion without the need for reintervention. The primary endpoints were primary and secondary patency rates and limb salvage rates.
The 1-year results reported by the investigators included a primary patency rate of 73.3%, a secondary patency rate of approximately 78%, and a limb salvage rate of almost 95%. Only one patient had an amputation above the knee.
Biotronik Vascular Intervention will enter the US market in 2006. Endovascular Today will provide ongoing coverage.