Modern Stents Research Articles

Longitudinal compression: a “new” complication with modern coronary stent platforms – time to think beyond deliverability?

Longitudinal compression: a “new” complication with modern coronary stent platforms – time to think beyond deliverability?

Endoskopische Palliation bei Ösophagus- und Bronchialkarzinomen

Luminal obstruction from tumor growth can in relation to bronchial carcinoma lead to airway and/or esophageal obstruction in breathlessness or swallowing difficulties respectively. Self-expanding stents have become an established method of restoring luminal patency in both the esophagus and central airways, leading to significant symptomatic improvement. Due to anatomical constraints particularly in processes around the tracheal carina, stent implantation within the bronchial system often poses greater difficulty than within the esophagus. Technical difficulties do however arise in the esophagus, specifically in relation to stenotic high-cervical tumors, as well as distal stenosis. In this regard, advances in stent development have resulted in significantly improved outcomes with modern stents. In high-cervical esophageal tumors as well as locally invasive tumors with evidence of tracheobronchial fistulae a shared interdisciplinary care between the gastroenterology and pulmonary teams is necessary for a satisfactory outcome.

The role of stents in the treatment of congenital heart disease: Current status and future perspectives

Intravascular or intracardiac stenoses occur in many forms of congenital heart disease (CHD). Therefore, the implantation of stents has become an accepted interventional procedure for stenotic lesions in pediatric cardiology. Furthermore, stents are know to be used to exclude vessel aneurysm or to ensure patency of existing or newly created intracardiac communications. With the further refinement of the first generation of devices, a variety of “modern” stents with different design characteristics have evolved. Despite the tremendous technical improvement over the last 20 years, the “ideal stent” has not yet been developed. Therefore, the pediatric interventionalist has to decide which stent is suitable for each lesion. On this basis, currently available stents are discussed in regard to their advantages and disadvantages for common application in CHD. New concepts and designs developed to overcome some of the existing problems, like the failure of adaptation to somatic growth, are presented. Thus, in the future, biodegradable or growth stents might replace the currently used generation of stents. This might truly lead to widening indications for the use of stents in the treatment of CHD.

Abstract 2553: Novel Cobalt-Chromium Ultra-Thin Strut Stent: Feasibility, Vascular Compatibility, and Safety Evaluation in Porcine Coronary Arteries

Stent-strut thickness is related to in-stent restenosis. Therefore, modern bare-metal stents (BMS) with lower strut thickness are in development. We sought to evaluate a new ‘third-generation’ BMS comprising an ultra-thin-strut, cobalt-chromium platform with fixed geometry and uniform cell sizes, in a clinically relevant animal model. 36 BMS of two types were implanted in pig coronaries using quantitative coronary angiography (QCA) to optimize stent apposition: a commercially available cobalt alloy thin-strut stent (91μm) as control (n=18), and an ultra-thin-strut (65μm) cobalt-chromium stent (Protea CoCr; n=18). Animals underwent angiographic restudy and termination 1-wk and 1-mo post-implant for coronary artery histology. In addition, 12 overlapping Protea CoCr stents were analyzed at 1-mo. All stents deployed without difficulties. Thin neointima and mild inflammation was seen in both groups at 1-wk. For 1-mo, QCA % diameter stenosis was significantly less for Protea CoCr (2±5% vs. 17±16%, p=0.032). By histomorphometry, intima thickness (0.11±0.05mm vs. 0.23±0.11mm, p=0.003) and % area stenosis (19±1% vs. 32±11%, respectively, p=0.004) were also significantly lower for Protea CoCr. The strut injury score was low and similar between the two groups. QCA % stenosis; intima thickness; and % area stenosis of overlapping Protea CoCr were 3±3%, 0.13±0.02mm, and 22±4%, respectively. Stable fibrocellular neointimal incorporation of all stents including overlapped Protea CoCr, with complete endothelialization and minimal inflammation, was seen at one month. Protea CoCr showed favorable arterial response with significant reduction of neointima formation compared to a commercial cobalt alloy BMS, one month post implant in pig coronary arteries. This ultra-thin-strut stent platform therefore appears to be a suitable and attractive alternative to current BMS. Combining the lower levels of neointima formation, fixed geometry, and uniform cell size, the Protea CoCr may be a preferred platform for next-generation drug-eluting stents.

Update of carotid stent trials

As is the case in many vascular territories, endovascular treatment of extracranial carotid artery disease is becoming a rival alternative to surgery. Results of carotid artery stenting (CAS) are improving with the introduction of embolic protection devices, improved technology, and increasing operator experience. Multiple clinical studies have shown results in favor of CAS as opposed to carotid endarterectomy (CEA) in patients considered at high risk for surgery. Current ongoing trials are examining both treatment options in low and intermediate risk patients in prospective randomized protocols. With the recent FDA approval of carotid stent systems, we are entering a new era in the treatment of carotid artery disease. An update of modern carotid stent studies, as well as stent versus surgery studies in the current era is needed.

Safety of Early Cardiac Magnetic Resonance Imaging in Acute Myocardial Infarction Patients With Stents

In general, magnetic resonance imaging is contraindicated when the patient has a ferromagnetic prosthesis or implant. With coronary stents, there is a theoretical concern that use of magnetic resonance imaging shortly after implantation will dislodge the stent, thereby increasing the risk of thrombosis. However, the risk may be overestimated because modern coronary stents are not ferromagnetic or are only weakly so. The objective of this study was to determine whether carrying out cardiac magnetic resonance imaging shortly after stent implantation is a safe procedure in acute myocardial infarction patients. We carried out a retrospective study of 407 patients with ST-elevation acute myocardial infarction who were treated by stent implantation. Cardiac magnetic resonance imaging was performed in the first 14 (11) days after stent implantation in 86 of these 407 patients (group 1); it was not performed in the 321 patients in group 2. The occurrence of an adverse event, such as death, reinfarction, or revascularization, either in hospital or after 6 or 12 months was recorded. Three patients experienced subacute stent thrombosis, all in group 2. No statistically significant difference in any other variable was found. The combined rate of death, reinfarction, revascularization, or rehospitalization at 12 months was 14% in group 1 and 16% in group 2 (P=.7). Carrying out cardiac magnetic resonance imaging shortly after stent implantation in acute myocardial infarction patients appears to be a safe procedure.

Impact of Carbon Coating on the Restenosis Rate After Stenting of Atherosclerotic Renal Artery Stenosis

To investigate the impact of carbofilm coating and low-profile rapid exchange stent devices on the restenosis rate after stent-angioplasty of atherosclerotic renal artery stenosis (RAS). During a 2-year period (7/2002-7/2004), 143 consecutive patients with 179 primary ostial atherosclerotic RAS>or=70% diameter stenosis were treated with stents selected at the discretion of the operator. Eighteen patients (32 lesions) treated with 9 different types of stents were excluded from the analysis, leaving 125 patients (69 men; mean age 67 years, range 42 to 90) with 147 lesions who received either a Radix carbofilm-coated stent in 78 (53%) lesions (68 [54%] patients) or a Palmaz Genesis bare stainless steel stent in 69 (47%) lesions (57 [46%] patients). The target vessel diameter ranged from 5 to 7 mm. Baseline characteristics were similar in both groups except the mean stent diameter, which was larger in the bare stent cohort (6.4+/-0.7 versus 5.9+/-0.5 mm, p<0.001). Primary success was 100% in both groups; the initial mean diameter stenosis was reduced from 79%+/-14% and 80%+/-14% in the coated versus bare stent groups to 3+/-5% and 2+/-6%, respectively. After a mean follow-up of 22+/-5 months, the restenosis rate was 6.4% for the coated stent and 5.8% for the bare stent (p=0.87). For the entire cohort, restenosis rates varied significantly (p<0.05) according to stent diameter: 19% (5/26) for 5 mm, 4% (3/81) for 6 mm, and 2.5% (1/40) for 7 mm. In a binary logistic regression analysis including carbofilm coating, stent diameter, gender, diabetes, smoking status, and body mass index, stent diameter was the only independent predictor of restenosis (odds ratio 0.12, 95% CI 0.03 to 0.48 [p=0.003] for a 1-mm increase in vessel diameter). Using modern low-profile stent devices, carbofilm coating does not significantly reduce the restenosis rate compared to a bare metal stent. With contemporary stent devices, the restenosis rate has been decreasing compared to earlier reports in the literature.

Technology Insight: novel ureteral stent materials and designs

Ureteral stents are an important tool for aiding upper urinary tract drainage, but can cause significant patient morbidity. Common problems include stent-induced pain, hematuria, dysuria, infection, and encrustation. From a urologist's perspective, stents must be easy to maneuver in the urinary tract, radiopaque, and affordable. Since the development of the modern day stent in 1978, stents have evolved to include softer biomaterials that are more resistant to encrustation and infection. An ideal biomaterial is one that is not affected by its environment and does not elicit reactive changes in surrounding tissues. To date, the ideal biomaterial or stent does not exist. This review discusses developments that address the issues of infection, biofilm formation, encrustation, and patient comfort. Stent materials including polyurethane, silicone, biodegradable substances and new combination polymers are reviewed, in addition to novel stent coatings such as heparin, hydrogel, and silver nitrate. Ureteral stent technologies currently lag behind vascular stents, particularly drug-eluting stents, but new developments will continue to improve these essential urological tools.

Single vs multivessel treatment during primary angioplasty: results of the multicentre randomised HEpacoat™ for cuLPrit or multivessel stenting for Acute Myocardial Infarction (HELP AMI) Study

Prospective randomized, multicentre study. Recanalisation of the culprit lesion is the main goal of primary angioplasty for acute myocardial infarction. With the exception of cardiogenic shock, staged procedures are performed in the presence of multivessel disease. The study hypothesis is that with modern non-thrombogenic stents (heparin coated) complete revascularization with multivessel treatment can be safely achieved during the primary angioplasty procedure with a lower need of subsequent revascularization procedures and at a lower cost. PRIMARY: 12-month incidence of repeat revascularization (any revascularization, infarct related artery as well as non-infarct-related artery). SECONDARY: (1) in hospital repeat revascularization, reinfarction and death; (2) total hospital cost (including a 12 months follow-up period). 69 patients with ST elevation Acute Myocardial Infarction (AMI), <12 hours after symptoms onset, undergoing primary angioplasty, with documented multivessel disease and both culprit lesion and 1 to 3 other lesions suitable for stent implantation. Unbalanced randomization between culprit lesion treatment only (n = 17) and complete multivessel treatment (n = 52, with 71 additional lesions treated). The two groups were well balanced in terms of clinical characteristics, number of diseased vessels and angiographic characteristics of the culprit lesion. In the complete multivessel treatment group 2.36 +/- 0.64 lesions per patient were treated using 2.73 +/- 0.78 heparin coated stents (1.00 lesions and 1.29 +/- 0.61 stents in the culprit treatment group, both p < 0.001). The duration of the procedure increased from 53 +/- 21 min (culprit treatment group) to 69 +/- 32 min (p = 0.032) and the amount of contrast used from 242 +/- 102 ml (culprit treatment group) to 341 +/- 163 ml (multivessel complete treatment), p = 0.025. A similar low incidence of in-hospital major adverse cardiac events was observed in the 2 groups (0 and 3.8% in culprit and multivessel treatment groups, p = 0.164). The increase in the incidence of new revascularisation in the culprit treatment group at 12 month follow-up was not significant (35 vs 17%, p = 0.247) but was sufficient to compensate the initial higher in-hospital cost, with a similar 12 month hospital cost in the 2 groups (Euro 22,330 +/- Euro 13,653 vs Euro 20,382 +/- Euro 11,671, p = 0.231). Multivessel treatment during primary PTCA was safe in this controlled trial. However, when only the culprit lesion was initially treated, the need for subsequent clinically driven revascularization remained low and no clinical or economical advantages were obtainable with a more aggressive initial approach. In clinical practice, a staged approach to multivessel treatment during primary angioplasty avoids to treat unnecessarily non clinically relevant lesions.

Platelet responses and coagulation activation on polylactide and heparin-polycaprolactone-L-lactide-coated polylactide stent struts.

Despite modern stent technology and effective antiplatelet therapy, metallic stents carry the risk of (sub)acute thrombosis. Our aim was to examine short-term differences in platelet deposition and coagulation activation between biodegradable polylactide (PLA), heparin-polycaprolactone-L-lactide-coated polylactide (hepa-P(CL95/L-LA5)-PLA), and stainless steel (SS) stent struts. Gel-filtered platelets (GFP) and platelet-rich plasma (PRP) were labeled with 10 nM (3)H-serotonin. Platelet deposition was measured after incubation of the stent struts in human serum albumin-coated wells at 37 degrees C in either GFP or PRP. Platelet morphology was studied by scanning electron microscopy (SEM). For coagulation activation, the stent struts were incubated in either PRP or platelet-poor plasma (PPP), anticoagulated with D-phenylalanyl-L-prolyl-L-arginine chloromethyl ketone (PPACK), followed by measurement of fibrinogen, thrombin time (TT), prothrombin fragment 1+2 (F1+2), and thrombin-antithrombin complex (TAT). SS showed adherence of larger amounts of GFPs than did PLA at a platelet density of 300 x 10(6)/mL (p < 0.05). Furthermore, representative SEM studies showed more platelet spreading on SS than on PLA stent struts. Between PLA and SS, coagulation activity did not differ at any assessment. Based on prolonged TT values in plasma, the heparin coating strongly inhibited coagulation (p < 0.05). The values of soluble TAT and F1+2 for PLA were similar to those of controls, i.e., to incubated suspensions without a stent strut. In conclusion, when compared with stainless steel, both PLA and hepa-P(CL95/L-LA5)-PLA appear hemocompatible as intravascular stent materials.

Percutaneous treatment for carotid stenosis

Stroke is the leading cause of serious long-term disability in the United States. A substantial portion of strokes are caused by atherosclerotic carotid artery disease. The conventional risk factors for coronary atherosclerosis are also responsible for carotid atherosclerosis. Carotid stenosis is encountered in medical practice in either symptomatic or asymptomatic states. In symptomatic patients, medical management with antiplatelet agents does not provide adequate protection against stroke. Carotid endarterectomy can help reduce the risk of a subsequent stroke. Asymptomatic patients with severe carotid stenosis can also benefit from surgical intervention if endarterectomy can be performed at a low operative risk. In recent years, percutaneous carotid stenting using self-expanding stents has become popular for the treatment of carotid stenosis. Although this initial experience has been reported from a high-risk patient population, the results are encouraging, with acceptable periprocedural stroke rates. Moreover, emboli protection devices, modern adjuvant pharmacotherapy, and modern self-expanding stents were not utilized in these studies. With rapidly expanding technology and advances in interventional pharmacology, improvement of clinical outcome is likely. Table 3 summarizes current recommendations for carotid stenting based on a panel of cardiologists, radiologists, and vascular surgeons. At this stage, randomized trials to compare endarterectomy with carotid stenting are underway. Cautious optimism is necessary until the optimal equipment, emboli protection devices, and adjuvant pharmacotherapies are fully investigated. Until then, carotid stenting should be restricted to high-risk candidates for carotid endarterectomy, including patients with severe cardiac comorbidities, previous neck surgeries or radiation, restenosis after endarterectomy, or other technical contraindications for surgery.

Angiography-guided routine coronary stent implantation results in suboptimal dilatation.

The resistance of the atherosclerotic lesion counteracts the expansion of the stent, resulting in suboptimal stent expansion. Intravascular ultrasound provides more precise information on stent expansion than coronary angiography but adds cost and time to the percutaneous transluminal coronary angiography procedure. The aim of this study was to evaluate the need for intravascular ultrasound at routine angiography-guided high pressure stent implantation by comparing stent expansion with predefined intracoronary ultrasound criteria for optimal stent implantation. In 32 patients, 48 stents (35 NIR, 12 AVE, and 1 Cordis) were implanted in A, B, and C stenoses using a high-pressure inflation technique until an optimal result was achieved according to angiography. Stent expansion was then evaluated by intravascular ultrasound as minimal lumen diameter, minimal lumen area, proximal and distal stent area, and a minimal lumen area symmetry index. These variables were then compared with the nominal stent size in vitro. Finally the stents were also evaluated with respect to the MUSIC criteria, ie, strict criteria regarding symmetry, apposition, and vessel geometry according to intravascular ultrasound after stent expansion. Forty-five stents could be completely analyzed. The mean balloon inflation pressure was 12.8 (range, 10-17) atm. The nominal stent size was not achieved in any patient. Minimal lumen diameter attained 77% and minimal lumen area 78% of expected nominal values (p<0.0001), distal stent area 88% (p < 0.001), and proximal stent area 92% (ns). Application of the MUSIC criteria showed that almost all stents (96%) had good stent apposition and symmetry index. Optimal proximal stent entrance was found in 70%. Optimal minimal lumen area in comparison to the reference areas was present in 41%. This lead to fulfilling of all MUSIC criteria in 47% of the stents. If nominal stent size had been achieved, symmetry index and apposition would have been fulfilled in all cases and optimal minimal lumen area increased to 75%. Acceptable proximal entrance however would have decreased to 55% and the fulfillment of all MUSIC criteria would increase only to 52%. In routine angiography-guided stent implantation in stenoses with a wide range of severities using modern stents and high pressure inflation technique to reach a visually optimal result, the nominal stent size was never achieved mainly due to residual intrastent stenosis. If nominal stent size had been achieved, the results would have improved only marginally and would still be suboptimal in almost half of the stents. These results highlight the shortcoming of angiography and the need for intravascular ultrasound in choosing correct stent size.

Stenting in small coronary arteries (SISCA) trial: A randomized comparison between balloon angioplasty and the heparin-coated beStent

OBJECTIVESThe purpose of this study was to assess the clinical and angiographic benefits of elective stenting in coronary arteries with a reference diameter of 2.1 to 3.0 mm, as compared with traditional percutaneous transluminal coronary angioplasty (PTCA).BACKGROUNDThe problems related to small-vessel stenting might be overcome using modern stents designed for small vessels, combined with effective antiplatelet therapy.METHODSIn five centers, 145 patients with stable or unstable angina were randomly assigned to elective stenting treatment with the heparin (Hepamed)-coated beStent or PTCA. Control angiography was performed after six months. The primary end point was the minimal lumen diameter (MLD) at follow-up. Secondary end points were the restenosis rate, event-free survival and angina status.RESULTSAt follow-up, there was a trend toward a larger MLD in the stent group (1.69 ± 0.52 mm vs. 1.57 ± 0.44 mm, p = 0.096). Event-free survival at follow-up was significantly higher in the stent group: 90.5% vs. 76.1% (p = 0.016). The restenosis rate was low in both groups (9.7% and 18.8% in the stent and PTCA groups, respectively; p = 0.15). Analyzed as treated, both the MLD and restenosis rate were significantly improved in patients who had stents as compared with PTCA.CONCLUSIONSIn small coronary arteries, both PTCA and elective stenting are associated with good clinical and angiographic outcomes after six months. Compared with PTCA, elective treatment with the heparin-coated beStent improves the clinical outcome; however, there was only a nonsignificant trend toward angiographic improvement.

Clinical and quantitative coronary angiographic predictors of coronary restenosis: A comparative analysis from the balloon-to-stent era

OBJECTIVESWe sought to assess whether coronary stents have modified the predictive value of demographic, clinical and quantitative coronary angiographic (QCA) predictors of coronary restenosis.BACKGROUNDA systematic analysis in a large cohort of registries and randomized trials of the percutaneous transluminal coronary angioplasty (PTCA) and stent era has never been performed.METHODSA total of 9,120 treated lesions in 8,156 patients included in nine randomized trials and 10 registries, with baseline, post-procedural and six-month follow-up QCA analyses, were included in this study. Predictors of restenosis were identified with univariate and multivariate logistic regression analyses. Interaction terms were introduced in the regression equation to evaluate whether the predictors of restenosis were common to both eras or specific for either one of the revascularization techniques.RESULTSThe restenosis rate was 35% after PTCA and 19% after angioplasty with additional stenting. In the univariate analysis, favorable predictors were previous coronary artery bypass graft surgery (CABG), stent use, stent length and a large pre-procedural minimal lumen diameter (pre-MLD); unfavorable predictors were weight, body mass index, diabetes mellitus, multi-vessel disease, lesion length and a high residual post-procedural diameter stenosis (post-DS). Predictors specific for the PTCA population were a large post-procedural MLD (post-MLD) as favorable and a severe pre-procedural DS (pre-DS) as unfavorable. Favorable predictors specific for the stent population were a large post-MLD and a large pre-procedural reference diameter (pre-RD). In the multivariate analysis, the best model included the following favorable predictors: stent use, a large post-MLD, previous CABG and the interaction term between stent use and a large post-MLD; unfavorable predictors were lesion length and diabetes mellitus.CONCLUSIONSThere are no major differences in demographic and clinical predictors of coronary restenosis between PTCA and stent populations. In the modern (stent) era, a severe pre-DS is no longer an unfavorable predictor of restenosis. Still important, but more so in the stent population, is a large post-MLD (optimal result). Finally, a larger pre-RD became a favorable predictor with the advent of stenting.

Urinary Tuberculosis: From Demolition to Reconstruction

Tuberculosis is increasing in Italy and even today is still a progressive fatal illness if not treated quickly. Drug therapy still plays an important role, while endoscopy and surgery offer further therapeutic possibilities compared to the past, with excellent results regarding the most feared complication - cicatricial stenosis. Simple ureteral endoscopic dilation with catheters has given way to the insertion of modern well-tolerated in-dwelling stents that can be used even with upper calyceal stenoses. Reconstructive bladder surgery, making new orthotopic-bladders, is a valid method for treating retracted bladders. The authors report their experience in treating TBC complications in 45 patients and in particular one paradigmatic case of urinary tuberculosis with serious stenosis involving the complete urinary system between the pelvis and the distal urethra. Urethroplasty and new orthotopic ileal bladder allowed the patient, who previously had an external deviation, to micturate naturally again.

Modern stent for nose surgery.

Modern stent for nose surgery.