Comparison of early and late results of a Carbofilm-coated stent versus a pure high-grade stainless steel stent (the Carbostent-Trial)

Unravelling Surface Modification Strategies for Preventing Medical Device-Induced Thrombosis

The use of biomaterials in implanted medical devices remains hampered by platelet adhesion and blood coagulation. Thrombus formation is a prevalent cause of failure of these blood-contacting devices. Although systemic anticoagulant can be used to support materials and devices with poor blood compatibility, its negative effects such as an increased chance of bleeding, make materials with superior hemocompatibility extremely attractive, especially for long-term applications. This review examines blood-surface interactions, the pathogenesis of clotting on blood-contacting medical devices, popular surface modification techniques, mechanisms of action of anticoagulant coatings, and discusses future directions in biomaterial research for preventing thrombosis. In addition, this paper comprehensively reviews several novel methods that either entirely prevent interaction between material surfaces and blood components or regulate the reaction of the coagulation cascade, thrombocytes, and leukocytes.

Carbon-Coated Stent and the Role of the Kallikrein-Kinin System in Peripheral Angioplasty

OBJECTIVE

The purpose of this study was to investigate the clinical evolution of patients treated with carbon-coated stent, as well as its patency and the inflammatory response triggered by this process through the quantification of serum elements of the kallikrein-kinin system (KKS).

METHODS

This was a single-center prospective study with 27 patients with peripheral artery disease (PAD) who required percutaneous transluminal angioplasty and stenting of the iliacofemoropopliteal segment using carbon-coated stent grafts (carbostents). The blood concentrations of the total and kininogen fractions were evaluated using immunoenzymatic methods. Plasma kallikrein levels were assessed by the colorimetric method and tissue kallikrein levels were evaluated by the spectrophotometric method. The activity of kininase II was measured by -fluorometric analysis.

RESULTS

Of the 27 patients who completed the 6 months of the study (11 iliac territory, 16 femoropopliteal territory), only one experienced restenosis (3.7%) (femoropopliteal segment) and no patient had occlusion (96.3% of patency). In 1 year, four patients were lost to follow-up and all 23 patients evaluated maintained stent patency, except for the patient who had restenosis throughout the first 6 months. We report complete (100%) member salvage in 12 months of follow-up. The activity levels of high- and low-molecular-weight kininogens decreased significantly over time (before vs. 24 h, p < 0.01; before vs. 6 months, p < 0.001, and before vs. 24 h, p < 0.01; before vs. 6 months, p < 0.001; 24 h vs. 6 months, p < 0.001, respectively). Patients also had significantly lower levels of plasma and tissue kallikrein (before vs. 24 h, p < 0.001; before vs. 6 months, p < 0.001, and before vs. 24 h, p < 0.01; before vs. 6 months, p < 0.05, respectively). There was a significant increase in the enzymatic activity of kininase II at 24 h and after 6 months compared to the pre-treatment control (p < 0.001).

CONCLUSION

Our early experience shows that the use of carbon-coated stents in PAD appears to be safe, with low rates of early restenosis (3.7% in the first 6 months and 5% in the 12 months of follow-up). We concluded that KKS was involved in the inflammatory response caused by the placement of carbon-coated stents.

Anti-fouling strategies for central venous catheters

Central venous catheters (CVCs) are ubiquitous in the healthcare industry and carry two common complications, catheter related infections and occlusion, particularly by thrombus. Catheter-related bloodstream infections (CRBSI) are an important cause of nosocomial infections that increase patient morbidity, mortality, and hospital cost. Innovative design strategies for intravenous catheters can help reduce these preventable infections. Antimicrobial coatings can play a major role in preventing disease. These coatings can be divided into two major categories: drug eluting and non-drug eluting. Much of these catheter designs are targeted at preventing the formation of microbial biofilms that make treatment of CRBSI nearly impossible without removal of the intravenous device. Exciting developments in catheter impregnation with antibiotics as well as nanoscale surface design promise innovative changes in the way that physicians manage intravenous catheters. Occlusion of a catheter renders the catheter unusable and is often treated by tissue plasminogen activator administration or replacement of the line. Prevention of this complication requires a thorough understanding of the mechanisms of platelet aggregation, signaling and cross-linking. This article will look at the advances in biomaterial design specifically drug eluting, non-drug eluting, lubricious coatings and micropatterning as well as some of the characteristics of each as they relate to CVCs.

Medical device-induced thrombosis: what causes it and how can we prevent it?

Blood-contacting medical devices, such as vascular grafts, stents, heart valves, and catheters, are often used to treat cardiovascular diseases. Thrombus formation is a common cause of failure of these devices. This study (i) examines the interface between devices and blood, (ii) reviews the pathogenesis of clotting on blood-contacting medical devices, (iii) describes contemporary methods to prevent thrombosis on blood-contacting medical devices, (iv) explains why some anticoagulants are better than others for prevention of thrombosis on medical devices, and (v) identifies future directions in biomaterial research for prevention of thrombosis on blood-contacting medical devices.

Carbon-coated stents in patients with acute coronary syndromes

BACKGROUND

For patients with ST elevation myocardial infarction (STEMI) or non-ST elevation myocardial infarction (NSTEMI), rapid restoration of coronary blood flow is the primary therapeutic goal. Because of the acute nature of this clinical presentation, bleeding risks may not be adequately evaluated, limiting the use of drug-eluting stents, since premature discontinuation of antiplatelet therapy strongly predicts stent thrombosis. We evaluated angiographic and clinical results of non-drug-eluting carbon-coated stents.

METHODS

In this prospective observational study, angiographic and clinical 6-mo results of a carbon-coated stent for treatment of acute lesions in native coronary arteries were evaluated. Angiographic main outcome measures included in-stent late loss and binary restenosis rate. Major adverse cardiac events (MACEs) were defined as any death, Q-wave myocardial infarction (MI), and target lesion revascularization.

RESULTS

We included 320 patients with STEMI (n = 205) or NSTEMI (n = 115) with 360 lesions. Reference vessel diameter was 2.93 +/- 0.53 mm and stented length 22.7 +/- 13.8 mm. Angiographic follow-up was available in 220 of 360 lesions (61%). In-stent late loss was 0.69 +/- 0.75 mm, with a binary restenosis rate of 19.1%. For the total segment late loss was 0.74 +/- 0.77 mm and binary restenosis rate 21.4%. Clinical follow-up for 97.4% of discharged patients was available. Hierarchical MACEs were death in 14 patients (4.4%), Q-wave MI in 3 patients (0.9%), and target lesion revascularization in 39 patients (12.2%).

CONCLUSION

In this prospective, observational study, the use of a carbon-coated stent for treatment of lesions in patients with STEMI or NSTEMI was associated with a low late loss, translating into a low binary angiographic restenosis rate within a 6-mo follow-up.

Current Strategies in Cardiovascular Biomaterial Functionalization

Prevention of the coagulation cascade and platelet activation is the foremost demand for biomaterials in contact with blood. In this review we describe the underlying mechanisms of these processes and offer the current state of antithrombotic strategies. We give an overview of methods to prevent protein and platelet adhesion, as well as techniques to immobilize biochemically active molecules on biomaterial surfaces. Finally, recent strategies in biofunctionalization by endothelial cell seeding as well as their possible clinical applications are discussed.

Risk factors for in-stent restenosis after vertebral ostium stenting

PURPOSE

To determine whether vascular risk factors, underlying vessel diameter, and/or the type of stent affect restenosis rates for vertebral ostium stents.

METHODS

A single-center retrospective analysis was conducted of 44 patients (31 men; mean age 61 years, range 32-81) who underwent stenting of 48 ostial lesions in the vertebral arteries between 1999 and 2005. Only patients who underwent angiographic follow-up were included in the analysis. Cox regression analysis was utilized for risk factor association with binary restenosis (> or =50% versus <50%). Stent types and stent categories were compared for differences in binary restenosis rates and lumen gain at follow-up angiography.

RESULTS

Twenty-three (48%) of 48 lesions had > or =50% stenosis at a mean follow-up of 7.7 months. Cigarette smoking was associated with higher binary restenosis rates (p=0.025), while hypertension, diabetes, hyperlipidemia, history of neck radiation, and known coronary artery and/or peripheral vascular disease were not. Reduced binary restenosis rates and improved lumen gain were seen in cobalt chromium balloon-expandable stents compared to non-cobalt chromium stents (p=0.002 and p=0.002, respectively), stainless steel balloon-expandable stents (p=0.005 and p=0.005), and the S670 stent (p=0.069 and p=0.069). The size of stent used was not associated with risk of restenosis (p=0.756).

CONCLUSIONS

Cobalt chromium stents were associated with reduced restenosis, while smoking was associated with increased restenosis risk.

Does Carbofilm Coating Affect In-Stent Intimal Proliferation? A Randomized Trial Comparing Rx Multi-Link Penta and Tecnic Carbostent? Stents: SIROCCO Trial

OBJECTIVES

To compare the volume of in-stent neointimal proliferation, assessed by intravascular ultrasound (IVUS), at 6-month follow-up after implantation of a coronary Carbofilm-coated stent (Tecnic Carbostent, Sorin Biomedica Cardio, Saluggia, Italy) versus a conventional 316 L stent (Rx Multi-Link Penta, Abbott Laboratories, Abbott Park, IL).

BACKGROUND

Many trials suggest that stent characteristics and coating could be important determinants of restenosis.

METHODS

From October 2004 to May 2005, 63 patients were randomized to Tecnic (T, n = 30) or Penta (P, n = 33). The primary end-point was in-stent volume of neointimal hyperplasia (NIH) measured by IVUS at 6 months. The secondary end-points included binary restenosis, minimal luminal diameter (MLD), target lesion revascularization, and major adverse cardiac events.

RESULTS

There were no significant differences between T and P as to mean age, male gender, clinical status, complexity of the lesion, lesion length, reference vessel diameter before percutaneous coronary intervention (PCI), MLD pre-PCI, and stent-to-artery ratio. However, MLD poststenting was greater in P group than T group (2.81 +/- 0.45 mm vs. 2.49 +/- 0.33 mm, P < 0.002). At 6 months, angiographic late lumen loss (0.61 +/- 0.51 mm vs. 0.92 +/- 0.61 mm, P < 0.043), in-stent obstruction (25.86 +/- 16.48% vs. 38.33 +/- 19.56%, P = 0.021), and in-stent late loss volume (31.62 +/- 29.75 mm(3) vs. 57.28 +/- 37.16 mm(3), P = 0.016) were significantly lower in T group than in P group.

CONCLUSION

Penta stent appears to offer a better deployment and a larger MLD post-PCI than Carbofilm-coated stent. However, a thicker NIH was observed on Penta stent at 6-month follow-up, when compared to Tecnic.

Novel thromboresistant materials

The development of a clinically durable small-diameter vascular graft as well as permanently implantable biosensors and artificial organ systems that interface with blood, including the artificial heart, kidney, liver, and lung, remain limited by surface-induced thrombotic responses. Recent breakthroughs in materials science, along with a growing understanding of the molecular events that underlay thrombosis, has led to the design and clinical evaluation of a variety of biologically active coatings that inhibit components of the coagulation pathway and platelet responses by surface immobilization or controlled release of bioactive agents. This report reviews recent progress in generating synthetic thromboresistant surfaces that inhibit (1) protein and cell adsorption, (2) thrombin and fibrin formation, and (3) platelet activation and aggregation.

Subgroup analyses in therapeutic cardiovascular clinical trials: are most of them misleading?

BACKGROUND

Treatment decisions in clinical cardiology are directed by results from randomized clinical trials (RCTs). We studied the appropriateness of the use and interpretation of subgroup analysis in current therapeutic cardiovascular RCTs.

METHODS

We reviewed main reports of phase 3 cardiovascular RCTs with at least 100 patients, published in 2002 and 2004, and from major journals (Circulation, J Am Coll Cardiol, Am Heart J, Am J Cardiol, N Engl J Med, Lancet, JAMA, BMJ, Ann Intern Med). Information on subgroups included prespecification, number, interaction test use, significant subgroups found, and emphasis on findings. We examined appropriateness of reporting and differences according to sample size, overall trial result, and CONSORT adoption.

RESULTS

We selected 63 RCTs, with a median of 496 (range 100-15,245) patients. Thirty-nine RCTs were reported with subgroup analyses and 26 with > 5 subgroups. No trial was specifically powered to detect subgroup effects, and only 14 RCTs were reported with fully prespecified subgroups. Only 11 RCTs were reported with interaction tests. Furthermore, 21 RCTs were reported with claims of significant subgroups and 15 with equal or more emphasis to subgroups than to the overall results. Subgroup analyses in large RCTs (> 500 patients) were reported more often than in small ones (24/30 vs 15/33, P = .005). No differences were found according to overall result (positive/negative) or CONSORT adoption.

CONCLUSIONS

Subgroup analyses in recent cardiovascular RCTs were reported with several shortcomings, including a lack of prespecification and testing of a large number of subgroups without the use of the statistically appropriate test for interaction. Reporting of subgroup analysis needs to be substantially improved because emphasis on these secondary results may mislead treatment decisions.

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

PURPOSE

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).

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

Does a Carbon Ion-Implanted Surface Reduce the Restenosis Rate of Coronary Stents?

BACKGROUND

Neointimal hyperplasia and resulting restenosis limit the long-term success of coronary stenting. Heavy metal ions induce an inflammatory and allergic reaction, and result in in-stent restenosis. However, a carbon ion-implanted surface might prevent heavy metal ions from diffusing into surrounding tissue.

METHODS

140 lesions in 140 patients with coronary lesions underwent implantation of carbon-implanted surface stents (Arthos(inert) stent group, n=70) or control stents (Arthos stent group, n=70). The primary end point was the in-stent restenosis and the secondary end point was the value of hs-CRP at 48 h and 6 months after coronary stenting. Clinical and angiographic follow-ups were performed at 6 months.

RESULTS

The rate of in-stent restenosis was lower in the Arthos(inert) stent group (15.9%, 10/63) than in the Arthos stent group (20.9%, 13/62), but there were no significant differences between both groups (p=0.56). The value of hs-CRP at 48 h was lower in the Arthos(inert) stent group (13.9+/-13.4 mg/dl) than in the Arthos stent group (24.5+/-26.0 mg/dl) with significant differences (p=0.04). However, the differences between two groups were not statistically significant at 6 months (p=0.76).

CONCLUSIONS

As compared with a standard coronary stent, a carbon ion-implanted stent shows no considerable benefit for the prevention of in-stent restenosis within the range of this study. Despite all the limitations of this study, a positive effect of a carbon ion-implanted stent in reducing inflammatory reaction after coronary revascularization seems likely.

Prospective randomized comparison of early and late results of a carbonized stent versus a high-grade stainless steel stent of identical design: the PREVENT Trial [corrected]

BACKGROUND

Restenosis after coronary interventions with stent implantation is still the main obstacle of interventional cardiology. The aim of this study was to compare a carbonized and high-grade stainless steel stent of identical design with regard to early and late adverse events.

METHODS

In this prospective randomized trial the carbonized MAC stent (amg GmbH, Raesfeld-Erle, Germany) was compared with the stainless steel MAC stent of identical design. Primary end point was diameter stenosis at follow-up; secondary end points were angiographic parameters, rate of restenosis, and major cardiac adverse events (MACE; myocardial infarction, reintervention, and death).

RESULTS

Between August 1999 and June 2002, 396 patients were randomized in 2 centers of Germany. Diameter stenosis at follow-up (38.6% +/- 23.4% vs 39.1% +/- 22.2%, P = .49) as primary end point, relative late lumen loss (26.8% +/- 23.7% vs 27.7% +/- 22.3%, P = .26), absolute late lumen loss (0.92 +/- 0.71 vs 0.92 +/- 0.66 mm, P = .58), net gain (1.4 +/- 0.8 vs 1.4 +/- 0.8 mm, P = .96), as well as restenosis rates (18.0% vs 19.0%, P = .81) and MACE (13.5% vs 12.2%, P = .71) were not significantly different between the carbonized and the pure stainless steel study arm, respectively.

CONCLUSION

The hypothesis of superiority of the carbonized stent over a stainless steel stent of identical design with regard to restenosis and MACE could not be proved. Inactive coating of stents seems to have no advantage over pure stainless steel stents, which was also demonstrated in other trials. The future probably lies in active coating of stents with drugs that reduce the neointimal proliferation process.