A Biodegradable Poly‐l‐lactic Acid Coronary Stent in the Porcine Coronary Artery

Abstract

Although biocompatibility of biodegradable stents is controversial, stents made of high molecular weight poly‐l‐lactic acid (PLLA) are thought to be the most promising. We investigated the biocompatibility of PLLA stents histologically and angiographically in porcine coronary arteries. The Igaki‐Tamai stent is made of PLLA monofilaments (molecular mass 183 kD) with a zigzag helical coil design. Fourteen PLLA stents in 6 pigs and 9 Palmaz‐Schatz half stents in 9 pigs were implanted in 15 normocholesterolemic pigs. Stents were mounted on a delivery catheter, and were implanted percutaneously into coronary arteries. Coronary angiography was performed before and immediately after stenting, at 2 and 6 weeks in five PLLA pigs and nine Palmaz‐Schatz pigs. Histological studies were performed in PLLA pigs: 2 pigs at 2 weeks, 3 pigs at 6 weeks, and 1 pig at 16 weeks with hematoxylin‐eosin and elastica van Giesons stains. All PLLA stents were successfully delivered. No stent thrombosis was detected in either group. There were no significant differences in minimal lumen diameter (MLD) or percent diameter stenosis between the PLLA and Palmaz‐Schatz stent groups immediately after implantation, or at 2 or 6 weeks after implantation. Histological studies at 2, 6, and 16 weeks revealed no inflammation and minimal neointimal coverage on the PLLA stent struts. The PLLA stent maintained its structure for up to 16 weeks. These results suggest sufficient biocompatibility and strength of PLLA biodegradable stents in porcine coronary arteries. Clinical trial is now underway to validate the safety and usefulness of PLLA stents in humans.

A New Wave in Treatment of Vascular Occlusive Disease: Biodegradable Stents—Clinical Experience and Scientific Principles

“…Coil stents generally exhibit a greater width between struts than tubular stents, which allows for greater flexibility at the expense of radial strength. An increased strut width may also allow for vascular prolapse into the lumen (80). Consequently, coil stents have been shown to induce greater rates of restenosis than their tubular counterparts manufactured from the same material (81,82).…”

Biodegradable Stents: Biomechanical Modeling Challenges and Opportunities

“…It is a balloon-expandable stent accompanied with a mild application of heat to help set the deployed geometry. After encouraging animal results, 69 human coronary implantations (the first biodegradable stent deployed in humans) followed and showed promising initial results at 1 year (obviously, compared with the standards prior to the drug elution stents era): 10.5% restenosis and 6.7% target lesion revascularization in a total of 30 lesions. 72 The long-term safety profile of the Igaki-Tamai stent is backed with an event-free survival of 82% at 4 years but unfortunately, the device has not been commercially successful due in part to concerns over the necessity of heat-setting.…”

Current status of research and application in vascular stents

“…The Igaki-Tamai TM stent (Igaki Medical Planning Company, Kyoto, Japan) is the first BDS which was developed by Tamai et al [49] in 1999. The total stent is comprised of PLLA and a zig-zag helical coil design with straight bridges.…”