Uncoated Stents Research Articles

Local gene transfer of phVEGF-2 plasmid by gene-eluting stents: an alternative strategy for inhibition of restenosis.

Drug-eluting stents represent a useful strategy for the prevention of restenosis using various antiproliferative drugs. These strategies share the liability of impairing endothelial recovery, thereby altering the natural biology of the vessel wall and increasing the associated risk of stent thrombosis. Accordingly, we tested the hypothesis that local delivery via gene-eluting stent of naked plasmid DNA encoding for human vascular endothelial growth factor (VEGF)-2 could achieve similar reductions in neointima formation while accelerating, rather than inhibiting, reendothelialization. phVEGF 2-plasmid (100 or 200 microg per stent)-coated BiodivYsio phosphorylcholine polymer stents versus uncoated stents were deployed in a randomized, blinded fashion in iliac arteries of 40 normocholesterolemic and 16 hypercholesterolemic rabbits. Reendothelialization was nearly complete in the VEGF stent group after 10 days and was significantly greater than in control stents (98.7+/-1% versus 79.0+/-6%, P<0.01). At 3 months, intravascular ultrasound analysis revealed that lumen cross-sectional area (4.2+/-0.4 versus 2.27+/-0.3 mm(2), P<0.001) was significantly greater and percent cross-sectional narrowing was significantly lower (23.4+/-6 versus 51.2+/-10, P<0.001) in VEGF stents compared with control stents implanted in hypercholesterolemic rabbits. Transgene expression was detectable in the vessel wall along with improved functional recovery of stented segments, resulting in a 2.4-fold increase in NO production. Acceleration of reendothelialization via VEGF-2 gene-eluting stents provides an alternative treatment strategy for the prevention of restenosis. VEGF-2 gene-eluting stents may be considered as a stand-alone or combination therapy.

Combination of paclitaxel and nitric oxide as a novel treatment for the reduction of restenosis.

The combination of a nitric oxide (NO) donor and a paclitaxel-NO donor conjugate coated on a vascular stent was tested in a rabbit iliac artery model of stenosis as a potential therapy for restenosis. Paclitaxel was conjugated with a NO donor at the 7-position to give compound 7. An adamantane-based NO donor 14 was synthesized and combined with 7 to provide a burst of NO in the first few critical hours following injury to the vessel wall. Both 7 and 14 demonstrated antiproliferative activity (IC(50) = 20 nM and 15 microM, respectively) and antiplatelet activity (IC(50) = 10 and 1 microM, respectively). Stents were coated with a layer of a polymer containing test compounds. The total amount of NO eluted from the stents after a 6 h implantation in the rabbit iliac artery was 35%, 95%, and 69% of the original content for the stents coated with 7, 14, and the combination of 7 and 14, respectively. The antistenotic activity of 7 and 14 was determined in a 28-day rabbit model with two control groups (uncoated stents and polymer-coated stents) and two study groups (paclitaxel-coated stents and stents coated with the combination of 7 and 14). Polymer-coated stents caused inflammation and increased stenosis by 39% when compared to the uncoated stents. The stents coated with 7 plus 14 were as good as the uncoated stents, 41% better than the polymer-coated stents and 34% better than the paclitaxel-coated stents. These data indicate a beneficial effect of adding NO to an antiproliferative agent (paclitaxel) and suggest a potential therapeutic combination for the treatment of stenotic vessel disease.

Drug eluting stents in the infrainguinal circulation

The short-term efficacy of drug-eluting stents has been validated in the coronary circulation, particularly with the drugs rapamycin and paclitaxel. The physical environment of the infrainguinal arteries is very different from the coronary circulation. Self-expanding stents are necessary in the femoropopliteal segment, which is subject to recurrent external forces. These include flexion at the knee, compression within the adductor hiatus, rotation and longitudinal compression. Thus, the properties required of a drug coating is likely be very different from those used in coronary arteries. This would appear to be borne out by SIROCCO, the only published study to date evaluating drug-eluting stents in the noncoronary circulation. SIROCCO began as a prospective randomized 36 patient trial comparing rapamycin coated to uncoated self-expanding SMART stents in the femoropopliteal segment. The first phase of SIROCCO demonstrated reduction of intimal hyperplasia by rapamycin. However, the study is being repeated to optimize the rate of drug elution, and multiple stent fractures seen in the first phase of the study necessitated modification of stent design. Considerable further study of drug eluting stents will be required in each vascular bed to determine the ideal stent/drug combination, and to establish clinical efficacy.

1139-58 A randomized study comparing a titanium-nitride-oxide coated with an uncoated stent for coronary revascularization

1139-58 A randomized study comparing a titanium-nitride-oxide coated with an uncoated stent for coronary revascularization

Comparison of diamond-like carbon-coated stents versus uncoated stainless steel stents in coronary artery disease

Stainless steel (SS) and carbon-coated (CC) stents were randomly compared in 347 patients (520 lesions). No differences were observed in in-hospital major adverse cardiac events: 2.8% in the CC group and 4.5% in the SS group (p = 0.286). The 6-month follow-up showed similar rates of binary restenosis (31.8% in the CC group vs 35.9% in the SS group; p = 0.448) and of cumulative major adverse cardiac events (30.5% in the CC group vs 32.7% in the SS group; p = 0.675). In unselected patients and lesions, carbon coating does not provide significant improvements over SS stents with the same design.

Spotlight on the Sirolimus-Eluting Stent in Coronary Artery Disease1

The sirolimus-eluting stent (CYPHER™) is a metal stent coated with 140 μg/cm2 of sirolimus blended with synthetic polymers. After stent implantation, sirolimus is slowly released causing localized cytostatic inhibition of proliferation of vascular smooth muscle cells in the peri-stent arterial wall over a period of about 1 month. Only minimal amounts of sirolimus enter the bloodstream and these appear to be insufficient to be of clinical relevance. In clinical trials that evaluated single de novo lesions and in-stent restenosis in patients with coronary artery disease, the sirolimus-eluting stent was associated with minimal neointimal hyperplasia. In four randomized trials in de novo lesions, sirolimus eluting stents produced a significantly lower incidence of major adverse cardiac events (MACE) than that observed in patients with uncoated stents, during periods of up to 2 years (p < 0.05 for all comparisons). The lower incidence of MACE was mostly due to a reduced requirement for repeat target vessel revascularization. At angiographic follow-up at periods of up to 8 months, late luminal loss was significantly smaller in the sirolimus-eluting stent groups than in the uncoated-stent groups (p < 0.001 in all studies). The sirolimus-eluting stent was well tolerated in clinical trials of up to 3 years’ follow-up. Because minimal blood levels of sirolimus are achieved, systemic adverse effects appear to be avoided. To date, there has been no evidence of any potential adverse effects resulting from the polymer coating or local drug toxicity. As yet, there is no evidence of an increased risk of subacute or late thrombosis, or aneurysm formation with the sirolimus-eluting stent compared with the uncoated stent. Long-term follow-up is needed to fully assess these theoretical concerns. Cost-effectiveness analyses over 12 months demonstrated a cost advantage for the sirolimus-eluting stent compared with an uncoated stent because of a reduced requirement for repeat target vessel revascularizations. Conclusion: Initial clinical trials with the sirolimus-eluting stent in patients with de novo coronary lesions have shown a significantly reduced incidence of MACE and of restenosis compared with a standard stent. Efficacy appears to be maintained throughout follow-up periods of up to 2 years in randomized trials, and to date, systemic or local adverse effects have been avoided. If efficacy and tolerability are consistently demonstrated over the long term, the sirolimus-eluting stent will be a major advance in the control of in-stent restenosis.

Efficacy of the Za Self-Expandable Metal Stent for Palliation of Malignant Biliary Obstruction

The efficacy and safety of the uncoated self-expandable Za metal stent for palliation of malignant distal biliary obstruction was prospectively analyzed. Twenty-one patients with unresectable malignant tumors involving mid to distal common bile duct who presented with obstructive jaundice underwent endoscopic implantation of an uncoated self-expandable metal stent. Technical success with stent placement, adverse events, patient survival, duration of stent patency, and device performance were analyzed. Endoscopic biliary stenting was successful in all patients. No adverse events were encountered. The mean follow-up period of the 21 patients was 128 days (range, 3-263): 14 died of progressive disease at mean of 81 days (range, 3-210), 3 remain alive (at days 239, 250, and 263), and 4 were lost to follow-up (at days 90, 91, 92, and 116). The mean duration of stent patency was 249 days. Tumor ingrowth was observed in one patient (5%). Minor technical problems were encountered in 3 patients: 1 proximal deployment, 1 distal deployment, and difficulty associated with the delivery system in 1. The Za-metal stent provided effective palliation for patients with inoperable malignant biliary tumors. Although minor technical problems were encountered with stent deployment, the overall stent patency, efficacy, and safety profile appear satisfactory.

Paclitaxel-Eluting Stents

In the past few years, drug-eluting stents have emerged as one of the most promising technologies in the field of interventional cardiology. Loaded with antiproliferative and anti-inflammatory agents, these stents have the potential to reduce post-stent-implantation restenosis significantly. In particular, sirolimus- and paclitaxel-eluting stents (PES) have been shown to be remarkably effective and are now available commercially in many countries.However, several PES systems have been under clinical investigation and produced different outcomes because of differences in their stent platforms, their total drug load, and their drug delivery and release concepts. The multicenter studies ASPECT (Asian Paclitaxel-Eluting Stent Clinical Trial), ELUTES (European evaLUation of PacliTaxel-Eluting Stent), and DELIVER (the RX Achieve drug-eluting coronary stent system in the treatment of patients with de novo native coronary lesions) I and II have been conducted to evaluate a PES system with direct impregnation of the agent onto the stent surface without using any further coatings. ASPECT and ELUTES revealed a clear dose response with descending binary restenosis rates for ascending drug dosages. However, statistically significant reductions of neointimal proliferation were only observed in the high-dose groups. DELIVER I, a study including 1043 patients, demonstrated the safety of the directly paclitaxel-coated RX Achieve stent, but the late loss reduction did not translate into a sufficient reduction of the clinical endpoints. The TAXUS program has been conducted to explore safety and efficacy of the TAXUS polymer-based, PES system, which delivers polymer-controlled low-dose paclitaxel, in contrast to the stents with direct impregnation. TAXUS I, a randomized trial with 61 patients, revealed the first evidence of the potential of this concept with remarkable results in safety and reduction of in-stent restenosis. In a larger patient population, the following TAXUS II trial demonstrated the safety and superior performance of the TAXUS-slow and TAXUS-moderate release stents over uncoated control stents for the reduction of restenosis up to 12 months after implantation. TAXUS IV, the pivotal US multicenter study including 1314 patients, underlined the efficacy of this stent in a wide range of complex patient and lesion subsets, including small vessels, long lesions, and diabetes mellitus. The ongoing TAXUS V and VI trials are designed to show whether this benefit will be reproducible in even more complex lesion subsets. Beside these randomized studies, several 'real-world' registries have recently been started to evaluate the performance of the TAXUS stent in daily clinical practice. Programs like these are vital to sufficiently monitor patients who have received a drug-eluting stent, particularly because of the controversy regarding long-term effects.

Biologic response to polymer-coated stents: in vitro analysis and results in an iliac artery sheep model.

To evaluate biologic response to poly(hydroxymethyl-p-xylylene-co-p-xylylene) (PHPX)-coated stents in vitro and in vivo in sheep. Physical stability, hemocompatibility, and cytotoxicity of the coating were first assessed in vitro. Thirty-six self-expanding nitinol (Memotherm), 24 stainless steel balloon-mounted (Palmaz), and 12 self-expanding nitinol (ZA) stents were coated with PHPX by using chemical vapor deposition polymerization. Seventy-two coated and 72 uncoated stents were placed into iliac arteries of 36 sheep. Sheep were classified into three groups of 12 animals each. In each group, six sheep were killed after 1 month; six, after 6 months. In each sheep, two uncoated stents were placed into one limb; two coated stents of the same type, into the opposite limb. In groups 1 and 2, Palmaz and Memotherm stents were used; in group 3, Memotherm and ZA stents were used. In groups 1 and 3, arteries were healthy. In group 2, arteries were pretreated with a Fogarty maneuver. Stent patency was measured with intravascular ultrasonography (US) and histologic analysis. Cellular response to coated and uncoated stents was assessed. Measurements were compared (Wilcoxon test). In vitro, PHPX coating was stable; hemocompatibility and cytotoxicity were similar to those of stainless steel. In vivo, patency of coated and uncoated Palmaz and ZA stents was not different (P >.05). Patency of coated and uncoated Memotherm stents did not differ in four of six follow-up subgroups, but it was significantly reduced in group 2 after 6 months (intravascular US, P =.03; histologic analysis, P =.01) and in group 3 after 1 month (histologic analysis, P =.01). Histologically, the cellular response to coated and uncoated stents was not different (P >.05). PHPX coating had good physical stability and biocompatibility in vitro and in vivo. Performance of coated and uncoated Palmaz and ZA stents was similar. Patency of Memotherm stents was similar in four of six follow-up subgroups. Materials effects did not result in severely enhanced neointimal hyperplasia.

Effect of stent coating alone on in vitro vascular smooth muscle cell proliferation and apoptosis.

Synthetic polymers, like methacrylate (MA) compounds, have been clinically introduced as inert coatings to locally deliver drugs that inhibit restenosis after stent. The aim of the present study was to evaluate the effects of MA coating alone on vascular smooth muscle cell (VSMC) growth in vitro. Stainless steel stents were coated with MA at the following doses: 0.3, 1.5, and 3 ml. Uncoated/bare metal stents were used as controls. VSMCs were cultured in dishes, and a MA-coated stent or an uncoated bare metal stent was gently added to each well. VSMC proliferation was assessed by bromodeoxyuridine (BrdU) incorporation. Apoptosis was analyzed by three distinct approaches: 1) annexin V/propidium iodide fluorescence detection; 2) DNA laddering; and 3) caspase-3 activation and PARP cleavage. MA-coated stents induced a significant decrease of BrdU incorporation compared with uncoated stents at both the low and high concentrations. In VSMCs incubated with MA-coated stents, annexin V/propidium iodide fluorescence detection showed a significant increase in apoptotic cells, which was corroborated by the typical DNA laddering. Apoptosis of VSMCs after incubation with MA-coated stents was characterized by caspase-3 activation and PARP cleavage. The MA-coated stent induced VSMC growth arrest by inducing apoptosis in a dose-dependent manner. Thus MA is not an inert platform for eluting drugs because it is biologically active per se. This effect should be taken in account when evaluating an association of this coating with antiproliferative agents for in-stent restenosis prevention.

Carotid stenting using heparin-coated balloon-expandable stent reduces intimal hyperplasia in a baboon model

Purpose. This study evaluates the effect of heparin-coated balloon-expandable stents on intimal hyperplasia following carotid artery stenting in a baboon model. Materials and methods. Balloon-expandable (Palmaz-Schatz) stents were placed in bilateral common carotid arteries in 26 male baboons (mean weight: 11.3 kg). In each animal, a heparin-coated (HC) carotid stent was placed on one side, whereas the contralateral carotid artery received an uncoated stent that served as a control. The carotid stents were harvested at 30 days ( n = 13) and 90 days ( n = 13). Arteriography was performed to assess the carotid patency, and intravascular ultrasound was used to determine neointimal and luminal areas. Histological, morphometric analysis, and scanning electron microscopy were performed in the stented carotid arteries. Results. One animal was excluded in each of the 1-month and 3-month groups because of premature death. Ten control (83%) and 11 HC stents (92%) remained patent in the 30-day group. In contrast, 10 control (83%) and 10 HC stents (83%) remained patent in the 90-day group. Morphometric analysis of the 30-day group showed the HC-stented carotid arteries had larger luminal areas (13%, P < 0.05), less neointimal areas (38%, P < 0.05), less neointimal/media ratios (53%, P < 0.05), and equivalent medial areas (NS) when compared with the control group. Morphometric analysis of the 90-day data showed the HC-stented carotid arteries had less neointimal areas (38%, P < 0.05) and less neointimal/media ratios (48%, P < 0.05), whereas the luminal areas and medial areas remained equivalent (NS) when compared with the control group. Conclusions. Carotid stenting using heparin-coated stents reduces early intimal hyperplasia in a baboon model. This approach may represent a useful strategy for improving luminal patency in endovascular carotid intervention.

New frontiers in cardiology: drug-eluting stents: Part II.

In this second part of the article, we will complete the review of drug-eluting stent technologies (Table 1) and discuss methodological and technical aspects of drug-eluting stents. View this table: TABLE 1. Drug-Eluting Stent Platforms Under Investigation ### Biological Agents (Continued) #### (1) Stents Eluting Antiproliferative Agents A number of antineoplastic medications have been considered for the prevention of restenosis. Paclitaxel and its derivatives have been the most investigated compounds of this group. ##### (a) Paclitaxel-Eluting Stents Paclitaxel (Taxol; Bristol-Myers Squibb) is a microtubule-stabilizing agent with potent antitumor activity.1 Many different platforms that use polymer coating or surface modifications to adhere paclitaxel onto the stents have been utilized over the past 2 years. ###### Preclinical Data Unlike other antimitotic agents, paclitaxel shifts the cytoskeleton equilibrium toward assembly, leading to reduced vascular cell proliferation, migration, and signal transduction.2 Paclitaxel is highly lipophilic, resulting in a rapid cellular uptake and a long-lasting effect in the cell.3 NIR stents (Boston Scientific Corp) coated with poly(lactide-co-Σ-caprolactone) copolymer and paclitaxel (200 μg/stent) were placed in porcine coronary arteries. Paclitaxel-eluting stents showed a marked reduction in neointimal and medial cell proliferation at all time points (7, 28, 56, and 180 days).4 However, arteries treated with paclitaxel showed incomplete healing, late persistence of a large number of macrophages, and fibrin deposition. Similar findings were observed with a stent platform coated with cross-linked biodegradable polymer (chondroitin sulfate and gelatin) and 42.0, 20.2, 8.6, or 1.5 μg of paclitaxel in rabbit iliac arteries.5 These studies indicate the need for a more controlled drug release of paclitaxel due to the narrow toxic-therapeutic window and high hydrophobic character of this compound. ###### Clinical Data: De Novo Lesions The QuaDS drug-eluting stent (Quanam Medical Corp) was the first drug-eluting stent implanted in human coronary arteries. This slotted tube stent has 50% of its surface area covered by multiple nonbiodegradable polyacrylate sleeves that release 7-hexanoyltaxol (called QP2 or taxane). Approximately 800 μg of the …

Heparin-coated Balloon-expandable Stent Reduces Intimal Hyperplasia in the Iliac Artery in Baboons

To examine the effect of heparin-coated balloon-expandable iliac stent placement on intimal hyperplasia in a baboon model. Balloon-expandable (Palmaz-Schatz) stents were placed in bilateral common iliac arteries in 20 male baboons (mean weight: 8.8 kg). In each animal, a heparin-coated iliac stent was placed on one side and the contralateral iliac artery received an uncoated stent that served as a control. The iliac artery stents were harvested at 30 days (n = 10) and 90 days (n = 10). Arteriography was performed to assess iliac patency and intravascular ultrasonography was used to determine neointimal and luminal areas. Histologic and morphometric analysis and scanning electron microscopy were performed in the stent-implanted iliac arteries. One animal was excluded in the 30-day group because of premature death. In the remaining nine surviving animals, seven control stents (78%) and nine heparin-coated stents (100%) remained patent. Morphometric analysis showed that the iliac arteries with heparin-coated stents had larger luminal areas (17%, P <.05), less neointimal area (26%, P <.05), lower neointima-to-media ratios (32%, P <.05), and equivalent medial areas (P =.92) compared to the control group at 30 days. In contrast, all control and heparin-coated stents were patent (100%) in the 90-day group. In that group, the heparin-coated stent group had less neointimal area (28%, P <.05), lower neointima-to-media ratios (42%, P <.05), and equivalent medial area (P =.92) and luminal area (P =.07) compared to the control group. The data demonstrate that heparin-coated balloon-expandable stents reduce intimal hyperplasia after iliac artery stent placement. This approach may represent a useful strategy for prolonging luminal patency after iliac stent placement.

In vivo model of intracranial stent implantation: a pilot study to examine the histological response of cerebral vessels after randomized implantation of heparin-coated and uncoated endoluminal stents in a blinded fashion.

No animal model currently exists for the examination of time-dependent histological changes occurring in intracranial vessels after endoluminal stent placement. The authors' goal was to develop a reproducible in vivo model of stent implantation in intracranial vessels in dogs that was capable of demonstrating stent-related vascular changes after the implantation of coated and uncoated devices. The authors implanted heparin-coated or uncoated stents in the basilar arteries (BAs) of 11 mongrel dogs. In a 12th animal, one coated stent was implanted in the BA and a second uncoated one was implanted in the distalanterior spinal artery. All the devices were oversized to induce intimal injury. Surviving animals were observed for 12 weeks, after which they underwent repeated angiography before planned death and removal of the brain. Histological studies and computer-assisted morphometric analyses were conducted on stent-treated and untreated sections of the BAs to assess the percentage of stenosis, neointimal proliferation, vessel injury, and inflammation. Perforating vessels partially covered by stent struts ("jailing") were studied for evidence of stenosis or occlusion. The pathologist, interventionists, histopathologist, histopathology technicians, and radiologist were blinded to the stent type. Seven stents (three uncoated and four coated) were removed from the six animals that were observed during the follow-up period. The mean neointimal proliferation was 0.42 mm2 in the group treated with uncoated stents and 0.18 mm2 in the group treated with heparin-coated devices (p = 0.04). Neointimal thickness was significantly increased in the group with uncoated stents (p = 0.04). The mean percentage of occlusion was less (12%) in the group with heparin-coated stents, compared with 22% in the group with uncoated devices (p = 0.07). When comparing results between the heparin-coated and uncoated devices implanted in the five animals that received a single stent only, greater differences (indicating a benefit from heparin-coated stents) were observed in neointimal area (p = 0.009), neointima/media ratio (p = 0.001), neointimal thickness (p = 0.002), and percentage of occlusion (p = 0.009). All brainstem perforating vessels covered by stent struts remained patent. This in vivo intracranial stent model was developed to assess proliferative and inflammatory responses to endoluminal stent implantation in the cerebrovasculature. The results indicate that a lower percentage of occlusion occurs 12 weeks after implantation of heparin-coated compared with uncoated stents.

Randomized intravascular ultrasound comparison between patients that underwent amorphous hydrogenated silicon-carbide coated stent deployment versus uncoated stents

Randomized intravascular ultrasound comparison between patients that underwent amorphous hydrogenated silicon-carbide coated stent deployment versus uncoated stents

The sirolimus-eluting stent: a review of its use in the treatment of coronary artery disease.

The sirolimus-eluting stent (CYPHER( trade mark )) is a metal stent coated with 140 micro g/cm(2) of sirolimus blended with synthetic polymers. After stent implantation, sirolimus is slowly released causing localized cytostatic inhibition of proliferation of vascular smooth muscle cells in the peri-stent arterial wall over a period of about 1 month. Only minimal amounts of sirolimus enter the bloodstream and these appear to be insufficient to be of clinical relevance. In clinical trials that evaluated single de novo lesions and in-stent restenosis in patients with coronary artery disease, the sirolimus-eluting stent was associated with minimal neointimal hyperplasia. In four randomized trials in de novo lesions, sirolimus eluting stents produced a significantly lower incidence of major adverse cardiac events (MACE) than that observed in patients with uncoated stents, during periods of up to 2 years (p < 0.05 for all comparisons). The lower incidence of MACE was mostly due to a reduced requirement for repeat target vessel revascularization. At angiographic follow-up at periods of up to 8 months, late luminal loss was significantly smaller in the sirolimus-eluting stent groups than in the uncoated-stent groups (p < 0.001 in all studies). The sirolimus-eluting stent was well tolerated in clinical trials of up to 3 years' follow-up. Because minimal blood levels of sirolimus are achieved, systemic adverse effects appear to be avoided. To date, there has been no evidence of any potential adverse effects resulting from the polymer coating or local drug toxicity. As yet, there is no evidence of an increased risk of subacute or late thrombosis, or aneurysm formation with the sirolimus-eluting stent compared with the uncoated stent. Long-term follow-up is needed to fully assess these theoretical concerns. Cost-effectiveness analyses over 12 months demonstrated a cost advantage for the sirolimus-eluting stent compared with an uncoated stent because of a reduced requirement for repeat target vessel revascularizations. Initial clinical trials with the sirolimus-eluting stent in patients with de novo coronary lesions have shown a significantly reduced incidence of MACE and of restenosis compared with a standard stent. Efficacy appears to be maintained throughout follow-up periods of up to 2 years in randomized trials, and to date, systemic or local adverse effects have been avoided. If efficacy and tolerability are consistently demonstrated over the long term, the sirolimus-eluting stent will be a major advance in the control of in-stent restenosis.

Sirolimus-eluting stents for the treatment of obstructive superficial femoral artery disease

Background— Stent implantation for obstructive femoropopliteal artery disease has been associated with poor long-term outcomes. This study evaluated the effectiveness of shape memory alloy recoverable technology (SMART) nitinol self-expanding stents coated with a polymer impregnated with sirolimus (rapamycin) versus uncoated SMART stents in superficial femoral artery obstructions. Methods and Results— Thirty-six patients were recruited for this double-blind, randomized, prospective trial. All patients had chronic limb ischemia and femoral artery occlusions (57%) or stenoses (average lesion length, 85±57 mm). Patients were eligible for randomization after successful guidewire passage across the lesion. Eighteen patients received sirolimus-eluting SMART stents and 18 patients received uncoated SMART stents. The primary end point of the study was the in-stent mean percent diameter stenosis, as measured by quantitative angiography at 6 months. The in-stent mean percent diameter stenosis was 22.6% in the sirol...

Bioavailability of EVA-Coated Metallic Stents Implanted in the Rabbit Iliac Artery

Background and Objectives:Coronary artery stenting actually shows a high efficacy in the treatment of coronary heart disease, but has the major limitation of restenosis. The ethylene-vinyl acetate copolymer (EVA), a biocompatible nondegradable copolymer, has been employed as a rate-controlling membrane in several drug delivery systems. Herein, the feasibility of an EVA-coated coronary stent was evaluated as a possible route for localized drug delivery. Materials and Methods:A total of 15 rabbits were employed in this study. An uncoated stent was implanted into the non-diseased iliac artery in six rabbits, and an EVA-coated stent into a further nine. On the 30th day following the stent implantations, stented segments of the iliac arteries were removed for histological processing and morphometric analysis. Results:The mean neointimal area of the uncoated and coated groups were 1.009 and 1.011 mm (p=0.56), respectively. No inflammatory cells were found in coated group. There were no apparent differences between the two groups. Conclusion:The results from this study have demonstrated that an EVA-coated coronary stent might be an appropriate method for the controlled-release of a drug. (Korean Circulation J 2003;33 (7):614-619)

Fate of side branches after coronary arterial sirolimus-eluting stent implantation

The sirolimus-eluting stent (SES) is emerging as a potential solution for the prevention of restenosis. Although the outcome of side branches after stenting with an uncoated metal stent (UMS) has been reported, the fate of side branches after SES implantation is unknown. Furthermore, the absence of spontaneous recanalization of occluded side branches following intracoronary brachytherapy has been previously described and has been related to a delayed healing process. We assessed the procedural and 6-month follow-up angiograms of 238 patients enrolled in the RAVEL study, a double-blind controlled trial of the SES versus the UMS. Any side branch seen on the preprocedure angiogram and subsequently covered by the stent was evaluated. The side branch Thrombolysis In Myocardial Infarction (TIMI) flow grade was assessed at baseline and at follow-up by 2 observers. One hundred twenty-eight patients with ≥1 side branches were identified (63 patients in the SES group with 118 side branches, 65 patients in the UMS group with 124 side branches). Side branch occlusion occurred after stenting in 12 branches (10%) in the SES group and in 9 branches (7%) in the UMS group (p = NS). Of these occluded branches, spontaneous recanalization was observed in 11 branches (92%) in the SES group and in 6 branches (67%) in the UMS group at follow-up angiography (p = NS). Thus, the fate of side branches after SES implantation is favorable and at least as good as after UMS implantation.

Heparin coating reduces encrustation of ureteral stents: a preliminary report

The present study evaluated the inhibition of ureteral stent encrustation by heparin coating. In contrast to uncoated polyurethane stents, heparin coated ureteral stents did not show any organic (biofilms) or anorganic (crystals) deposits after being in situ for up to 6 weeks and effectively inhibited the encrustation process.