Experimental Evaluation of a New Single Wire Tantalum Coil Coronary Stent (Wiktor-iª).

To improve scaffolding properties, a new more densely woven Wiktor stent, the Wiktor-iª stent, was developed. Although the metal coverage remains still low compared to other stents, increased metal/vessel area raises the concern of increased thrombogenicity and neointimal hyperplasia. In this study we evaluated the Wiktor-i stent in a porcine peripheral and coronary model and compared the thrombogenicity and neointimal hyperplasia with the Wiktor-GX coronary stent. In a first study, a Wiktor-i and a Wiktor-GX coronary stent were implanted symmetrically in a preselected side branch of the right and left iliac artery of 10 healthy pigs. Quantitative vessel analysis showed comparable data before, immediately after and at follow-up. Hyperplasia measured by morphometry was also comparable in both groups (Wiktor-GX: 1.43 mm2 vs. Wiktor-i: 1.17 mm2, NS). Also, area stenosis was very similar (Wiktor-GX: 32% vs. Wiktor-i: 29%, NS). In a second study, 20 Wiktor (Wiktor-i: n=10, Wiktor-GX: n=10) coronary stents were implanted in the right coronary artery of 20 healthy pigs. Quantitative coronary analysis before, immediately after and at follow-up was comparable in both stents. The hyperplasia measured morphometrically was also comparable in both stents. (Wiktor-GX: 1.51 +/- 0.47 mm2 vs. Wiktor-i: 1.46 +/- 0.66 mm2, NS). Also the area stenosis was not significantly different (Wiktor-GX: 31% vs. Wiktor-i: 35%). In conclusion, this study shows that the increased metal/vessel area of the Wiktor-i stent does not result in an increased neointimal hyperplasia. Both stents show to be very biocompatible when implanted in porcine coronary and peripheral vessels.

Stent Deployment Pressure Defines the Stent/Vessel Wall Relationship and has Important Implications for Early and Late Outcome.

OBJECTIVE: This study evaluates the effect of stent deployment pressure on stent deployment, coronary vessel injury, subacute reclosure and foreign body reaction in a porcine coronary model. METHODS: Stainless steel coil stents were deployed in the right coronary artery of 30 pigs either using a deployment pressure of 4 atm (group I), 8 atm (group II), or 14 atm (group III). Serial quantitative angiographic studies together with morphometric analysis of the stented vessels were performed. RESULTS: Three pigs died within 48 hours due to subacute thrombosis (group I: n = 1, group II: n = 0, group III: n = 2). Another 4 stents were found occluded at day 7 (group I: n = 3, group II: n = 0, group III: n = 1). Imperfect stent alignment was found in 8 coronary arteries (group I: n = 7, group II: n = 1, group III: n = 0). Deep protrusion of stent filaments was found in 7 coronary arteries (group I: n = 0, group II: n = 1, group III: n = 6). Area stenosis at 6 weeks of the patent vessels was as follows: 75.7 +/- 15.2% in group I, 31.8 +/- 12.3% in group II, and 66.9 +/- 21.4% in group III, p < 0.001). CONCLUSION: In a porcine coronary model, stent deployment pressure resulting in an optimal alignment and a minimal coronary vessel injury leads to minimal neointimal hyperplasia.

Intravascular Low Power Red Laser Light as an Adjunct to Coronary Stent Implantation Evaluated in a Porcine Coronary Model.

BACKGROUND: It is believed that restenosis following coronary interventions is the result of endothelial denudation that leads to thrombus formation, vascular remodeling, and smooth muscle cell proliferation. We previously demonstrated that low power red laser light (LPRLL) irradiation enhances endothelial cell growth in vitro and in vivo and reduces restenosis in a small animal model. The present study investigated the effectiveness of intravascular LPRLL therapy in the reduction of restenosis following stenting in a porcine model. METHODS AND RESULTS: Stents were placed in the right coronary artery of domestic cross-bred pigs. After stent deployment, an additional inflation was performed with the laser-balloon. In group I (n = 18) no LPRLL was used; group II (n = 10) received LPRLL dosage of 10 mW for 1 minute; group III (n = 10) received LPRLL dosage of 34 mW for 1 minute. Quantitative coronary analysis of the stented vessel was performed before, immediately after stenting, and at 6 weeks. The pigs were sacrificed and histologic and planimetric analysis conducted. At 6 weeks, minimal luminal stent diameter was significantly narrower in the control group compared to the higher dose group (p < 0.05), late loss correlated inversely proportional to the dose used (r = 0.9; p < 0.03), these results were confirmed by morphometric analysis. Neointimal area was also significantly decreased in the higher dose group. CONCLUSIONS: Intravascular LPRLL contributes to reduction of angiographic restenosis and hyperplastic reaction in this animal model and seems to be dose dependent.

Experimental Evaluation of a New Tubular Coronary Stent (V-Flexª).

The safety, efficacy, angiographic and histological effects of a new 316 L, SS seamless stainless steel tubular stent (V-Flexª, Global Therapeutics, Broomfield, Colorado) was evaluated in a porcine coronary and peripheral artery model. Implantation in the right coronary artery was successful in all 16 pigs. Eight pigs were angiographically controlled after 6 weeks and then sacrificed for morphometric analysis. All stented coronary vessels were widely patent at this moment and morphometric analysis showed only a mild fibromuscular neointimal hyperplasia resulting in a neointimal hyperplasia of 1.15 +/- 0.38 mm2. The remaining 8 pigs were controlled and sacrificed at 12 weeks. At that time, all stented vessels were patent and neointimal hyperplasia was 1.22 +/- 0.34 mm2. Comparison with the Palmaz-Schatzª coronary stent (Cordis, Miami, Florida) in a porcine peripheral artery model demonstrated significantly less neointimal hyperplasia at 6 weeks (1.11 +/- 0.73 vs. 2.40 +/- 0.36, p = 0.001) and at 12 weeks (1.53 +/- 0.42 vs. 2.47 +/- 0.63, p = 0.003) for the V-Flex stent. In conclusion, V-Flex coronary stent implantation in a porcine coronary and peripheral arteries results in a high procedural success rate without subacute thrombotic occlusions, despite no further anticoagulation nor antiplatelet therapy. Six and 12 week histopathological and morphometric evaluation demonstrated only a mild fibromuscular neointimal hyperplasia. Comparison with the Palmaz-Schatz coronary stent in a peripheral artery model showed significantly less neointimal hyperplasia in the V-Flex stent.

Experimental Evaluation of a New Single Wire Stainless Steel Fishscale Coronary Stent (Freedomª).

Recent randomized clinical trials revealed a significant reduction in angiographic restenosis rates when adjunctive stenting was performed after conventional coronary balloon angioplasty. Current approved coronary stents are however hampered by their rigidity, limiting their trackability in tortuous vessels and furthermore, needing high pressure deployment for optimal vessel apposition. New coronary stents are currently under development, using more biocompatible metal alloys and/or designs which better align to the vessel wall at moderate deployment pressures. We evaluated the safety, efficacy, angiographic and histological effect of a new stainless steel fishscale designed stent (Freedomª, Global Therapeutics, Co., USA) in a porcine coronary and peripheral artery model. Implantation in the right coronary artery was successful in all 20 pigs. Control angiograms at 6 weeks follow-up demonstrated patent vessels and morphologic evaluation showed only a mild fibromuscular neointimal response resulting in an area stenosis of 28.7 +/- 0.18% and a mean neointimal hyperplasia of 0.18 +/- 0.25 mm. Comparison with the Palmaz-Schatzª coronary stent in a porcine peripheral artery model demonstrated similar quantitative angiographic and morphologic vessel analysis results. Also the morphometric data were comparable. Area stenosis: Palmaz-Schatz: 37 +/- 0.24%, Freedom: 21 +/- 0.14%, p = 0.07. Mean neointimal hyperplasia: Palmaz-Schatz: 0.33 +/- 0.24 mm, Freedom: 0.18 +/- 0.08 mm, p = 0.08. CONCLUSION: Freedom coronary stent implantation in a porcine model resulted in a high procedural success without subacute thrombotic occlusions, despite no further anticoagulation nor antiplatelet therapy. Six weeks histopathological and morphometric evaluation demonstrated only a mild fibromuscular neointimal hyperplasia.