A biodegradable poly-l-lactic acid coronary stent in the porcine coronary artery

Although biocompatibility of biodegradable stents is controversial, stents made of high molecular weight poly-l-lactic acid (PLLA) are thought to be t he most promising. We investigated the biocompatibility of PLLA stents hist ologically and angiographically in porcine coronary arteries. The Igaki-Tam ai stent is made of PLLA monofilaments (molecular mass 183 kD) with a zigza g helical coil design. Fourteen PLLA stents in 6 pigs and 9 Palmaz-Schatz h alf stents in 9 pigs were implanted in 15 normocholesterolemic pigs. Stents were mounted on a delivery catheter, and were implanted percutaneously int o coronary arteries. Coronary angiography was performed before and immediat ely after stenting, at 2 and 6 weeks in five PLLA pigs and nine Palmaz-Scha tz pigs. Histological studies were performed in PLLA pigs: 2 pigs at 2 week s, 3 pigs at 6 weeks, and 1 pig at 16 weeks with hematoxylin-eosin and elas tica van Giesons stains. All PLLA stents were successfully delivered. No st ent thrombosis was detected in either group. There were no significant diff erences in minimal lumen diameter (MLD) or percent diameter stenosis betwee n the PLLA and Palmaz-Schatz stent groups immediately after implantation, o r at 2 or 6 weeks after implantation. Histological studies at 2, 6 and 16 w eeks revealed no inflammation and minimal neointimal coverage on the PLLA s tent struts. The PLLA stent maintained its structure for up to 16 weeks. Th ese results suggest sufficient biocompatibility and strength of PLLA biodeg radable stents in porcine coronary arteries. Clinical trial is now underway to validate the safety and usefulness of PLLA stents in humans.