Heparin-coated Palmaz-Schatz stents in human coronary arteries. Early outcome of the Benestent-II Pilot Study

Genotype-Guided P2Y12 Inhibitor Monotherapy Within 7 Days of Percutaneous Coronary Intervention in High Bleeding Risk Patients: The CHAMP Trial - A Pilot Study and Safety Assessment

OBJECTIVE

To test the feasibility and safety of genotype guidance in the selection of P2Y12 monotherapy within 1 week of percutaneous coronary interventions (PCIs) among patients with high bleeding risk (HBR).

PATIENT AND METHODS

The study was a single-center, open-label, pilot trial. Patients (n=100) with HBR (as defined by an academic research consortium) after successful PCI received dual antiplatelet therapy with clopidogrel and aspirin. Following availability of cytochrome P450 2C19 (CYP2C19) genotype results (mean, 2.9 days), aspirin was discontinued. Normal, rapid, or ultrarapid CYP2C19 metabolizers continued clopidogrel monotherapy for 90 days whereas loss-of-function allele carriers switched to prasugrel or ticagrelor monotherapy. The primary safety endpoints were a composite of post-dismissal cardiac death/spontaneous myocardial infarction less than 30 days or stent thrombosis <90 days of discharge. The subjects also underwent post-dismissal assessment for BARC (Bleeding Academic Research Consortium) type 3 or 5 bleeding, all-cause death, any MI, and/or repeat revascularization up to 90 days.

RESULTS

There were 98 patients with complete data (median age, 76.5 years, 36% women; 49% acute coronary syndrome). Sixty-nine (70.4%) were normal, rapid, or ultrarapid metabolizers and continued clopidogrel monotherapy, and 29 (29.6%) were intermediate CYP2C19 metabolizers and received monotherapy with prasugrel (n=21) or ticagrelor (n=8). The mean duration of dual antiplatelet therapy was 5.1 days. During 90-day follow-up, no patient died, there was one possible stent thrombosis, and three patients on clopidogrel had Bleeding Academic Research Consortium type 3 bleeding events.

CONCLUSION

Genotype-guided P2Y12 inhibitor monotherapy within a week of PCI is feasible and likely safe in patients with HBR (CHAMP [Clopidogrel With High Bleeding Risk and Adverse Events With Monotherapy in Patients Undergoing Percutaneous Coronary Interventions]; NCT05223335).

Drug Delivery Opportunities in Esophageal Cancer: Current Treatments and Future Prospects

With one of the highest mortality rates of all malignancies, the 5-year survival rate for esophageal cancer is under 20%. Depending on the stage and extent of the disease, the current standard of care treatment paradigm includes chemotherapy or chemoradiotherapy followed by surgical esophagogastrectomy, with consideration for adjuvant immunotherapy for residual disease. This regimen has high morbidity, due to anatomic changes inherent in surgery, the acuity of surgical complications, and off-target effects of systemic chemotherapy and immunotherapy. We begin with a review of current treatments, then discuss new and emerging targets for therapies and advanced drug delivery systems. Recent and ongoing preclinical and early clinical studies are evaluating traditional tumor targets (e.g., human epidermal growth factor receptor 2), as well as promising new targets such as Yes-associated protein 1 or mammalian target of rapamycin to develop new treatments for this disease. Due the function and location of the esophagus, opportunities also exist to pair these treatments with a drug delivery strategy to increase tumor targeting, bioavailability, and intratumor concentrations, with the two most common delivery platforms being stents and nanoparticles. Finally, early results with antibody drug conjugates and chimeric antigenic receptor T cells show promise as upcoming therapies. This review discusses these innovations in therapeutics and drug delivery in the context of their successes and failures, with the goal of identifying those solutions that demonstrate the most promise to shift the paradigm in treating this deadly disease.

Bioinspired chitosan based functionalization of biomedical implant surfaces for enhanced hemocompatibility, antioxidation and anticoagulation potential: an in silico and in vitro study

Endowing implanted biomaterials with better hemocompatibility, anticoagulation, antioxidant and antiplatelet adhesion is necessary because of their potential to trigger activation of multiple reactive mechanisms including coagulation cascade and potentially causing serious adverse clinical events like late thrombosis. Active ingredients from natural sources including Foeniculum vulgare, Angelica sinensis, and Cinnamomum verum have the ability to inhibit the coagulation cascade and thrombus formation around biomedical implants. These properties are of interest for the development of a novel drug for biomedical implants to potentially solve the current blood clotting and coagulation problems which lead to stent thrombosis. The objective of this study was to incorporate different anticoagulants from natural sources into a degradable matrix of chitosan with varying concentrations ranging from 5% to 15% and a composite containing all three drugs. The presence of anticoagulant constituents was identified using GC-MS. Subsequently, all the compositions were characterized principally by using Fourier transform infrared spectroscopy and scanning electron microscopy while the drug release profile was determined using UV-spectrometry for a 30 days immersion period. The results indicated an initial burst release which was subsequently followed by the sustained release pattern. Compared to heparin loaded chitosan, DPPH and hemolysis tests revealed better blood compatibility of natural drug loaded films. Moreover, the anticoagulation activity of natural drugs was equivalent to the heparin loaded film; however, through docking, the mechanism of inhibition of the coagulation cascade of the novel drug was found to be through blocking the extrinsic pathway. The study suggested that the proposed drug composite expresses an optimum composition which may be a practicable and appropriate candidate for biomedical implant coatings.

Self-anticoagulant sponge for whole blood auto-transfusion and its mechanism of coagulation factor inactivation

Clinical use of intraoperative auto-transfusion requires the removal of platelets and plasma proteins due to pump-based suction and water-soluble anticoagulant administration, which causes dilutional coagulopathy. Herein, we develop a carboxylated and sulfonated heparin-mimetic polymer-modified sponge with spontaneous blood adsorption and instantaneous anticoagulation. We find that intrinsic coagulation factors, especially XI, are inactivated by adsorption to the sponge surface, while inactivation of thrombin in the sponge-treated plasma effectively inhibits the common coagulation pathway. We show whole blood auto-transfusion in trauma-induced hemorrhage, benefiting from the multiple inhibitory effects of the sponge on coagulation enzymes and calcium depletion. We demonstrate that the transfusion of collected blood favors faster recovery of hemostasis compared to traditional heparinized blood in a rabbit model. Our work not only develops a safe and convenient approach for whole blood auto-transfusion, but also provides the mechanism of action of self-anticoagulant heparin-mimetic polymer-modified surfaces.

The biofunctionalization of titanium nanotube with chitosan/genipin heparin hydrogel and the controlled release of IL-4 for anti-coagulation and anti-thrombus through accelerating endothelialization

The valve replacement is the main treatment of heart valve disease. However, thrombus formation following valve replacement has always been a major clinical drawback. Accelerating the endothelialization of cardiac valve prosthesis is the main approach to reduce thrombus. In the current study, a titanium nanotube was biofunctionalized with a chitosan/genipin heparin hydrogel and the controlled release of interleukin-4 (IL-4), and its regulation of macrophages was investigated to see if it could influence endothelial cells to eventually accelerate endothelialization. TNT60 (titanium dioxide nanotubes, 60 V) with nanoarray was obtained by anodic oxidation of 60 V, and IL-4 was loaded into the nanotube by vacuum drying. The hydrogel (chitosan : genipin = 4 : 1) was applied to the surface of the nanotubes following drying, and the heparin drops were placed on the hydrogel surface with chitosan as the polycation and heparin as the polyanion. A TNT/IL-4/G (G = gel, chitosan/genipin heparin) delivery system was prepared. Our results demonstrated that the biofunctionalization of titanium nanotube with chitosan/genipin heparin hydrogel and the controlled release of IL-4 had a significant regulatory effect on macrophage M2 polarization, reducing the inflammatory factor release and higher secretion of VEGF (vascular endothelial growth factor), which can accelerate the endothelialization of the implant.

Hybrid myocardial revascularization

Background

In patients with advanced coronary artery disease (CAD), coronary artery bypass grafting (CABG) is associated with improved long-term outcomes while percutaneous coronary intervention (PCI) is associated with lower periprocedural complications. A new approach has emerged in the last decade that attempts to reap the benefits of bypass surgery and stenting while minimizing the shortcomings of each approach, hybrid myocardial revascularization (HMR).Three strategies for timing of the hybrid revascularization exists, each with their own inherent advantages and shortcomings: (1) CABG followed by PCI, (2) PCI followed by CABG, or (3) simultaneous CABG + PCI in a hybrid suite.

Studies

The results of the first randomized control trial comparing HMR (CABG first) and standard CABG, POL-MIDES (Prospective Randomized PilOt Study EvaLuating the Safety and Efficacy of Hybrid Revascularization in MultIvessel Coronary Artery DisEaSe), show HMR was feasible for 93.9% of patients whereas conversion to standard CABG was required for 6.1%. At 1 year, both groups had similar all-cause mortality (CABG 2.9% vs. HMR 2%) and major adverse clinical event (MACE)-free survival rates (CABG 92.2% vs. HMR 89.8%). Results of observational and comparative studies show that minimally invasive HMR procedures in patients with multivessel CAD carry minimal perioperative mortality risk and low morbidity and do not increase the risk of postoperative bleeding. The advantage they offer in comparison to classical surgical revascularization is indeed faster rehabilitation and patient's return to normal life.

Conclusion

Hybrid myocardial revascularization has been developed as a promising technique for the treatment of high-risk patients with CAD. Hybrid revascularization using minimally invasive surgical techniques combined with PCI offers to a part of patients an advantage of optimal revascularization of the most important artery of the heart, together with adequate myocardial revascularization in a relatively delicate way. Indeed, to patients with high operative risk of standard surgery, it offers an alternative which should be considered carefully.

Heparin Bonded Hemodialysis e-PTFE Grafts Result in 20% Clot Free Survival Benefit

Luminal surface heparin bonded hemodialysis e-PTFE grafts (N=83) with prolonged bioactivity retention (CBAS® technology) were compared to 67 control e-PTFE grafts using Kaplan-Meier survival curve estimates. Log-rank tests were used for statistical comparisons between groups. Heparin bonded graft recipients were on average 3.5 years older (NS), and had upper arm grafts in 66% vs. 43% (p=0.003) compared to controls. There was no clot-free survival (CFS) difference between groups for upper arm vs. forearm placed grafts (p=0.792). Patient mortality at one year was 15%, with no group difference. The overall combined clot-free survival for all 150 e-PTFE grafts was 69% at 12 months. At 6 and 12 months, CFS for the heparin bonded graft group was 88% and 78%, which is significantly higher than that of 69% and 58% for the control group, respectively, (p=0.007). It is concluded that heparin binding technology to artificial surfaces has evolved to a clinically powerful technique for the hemodialysis patient resulting in a 20% improved primary graft patency of about 80% at one year.

Introduction of Nature's Complexity in Engineered Blood-compatible Biomaterials

Biomaterials with excellent blood-compatibility are needed for applications in vascular replacement therapies, such as vascular grafts, heart valves and stents, and in extracorporeal devices such as hemodialysis machines and blood-storage bags. The modification of materials that are being used for blood-contacting devices has advanced from passive surface modifications to the design of more complex, smart biomaterials that respond to relevant stimuli from blood to counteract coagulation. Logically, the main source of inspiration for the design of new biomaterials has been the endogenous endothelium. Endothelial regulation of hemostasis is complex and involves a delicate interplay of structural components and feedback mechanisms. Thus, challenges to develop new strategies for blood-compatible biomaterials now lie in incorporating true feedback controlled mechanisms that can regulate blood compatibility in a dynamic way. Here, supramolecular material systems are highlighted as they provide a promising platform to introduce dynamic reciprocity, due to their inherent dynamic nature.

Antiplatelet Agents in Cardiovascular and Cerebrovascular Diseases

Aspirin has become a widely accepted platelet function inhibitor and is used to prevent arterial occlusions in coronary cerebral and peripheral vascular disease. The results of clinical studies with aspirin in the area of peripheral arterial occlusive disease are critically reviewed. Two thienopyridine compounds, ticlopidine and clopidogrel, have been effectively used in the prevention of myocardial infarction and stroke in several clinical trials, especially in the recently published CAPRIE-trial. Potent new platelet function inhibitors recently were developed. Intravenous treatment with abciximab, a new platelet membrane glycoprotein IIb/IIIa-inhibitor, effectively prevented coronary reocclusions in patients with high-risk coronary events. A series of promising new oral IIb/IIIa- inhibitors have been developed and may become effective drugs in the prevention of reocclusions in patients with periph eral vascular disease and in coronary or cerebral vascular dis ease. Key Words: Antiplatelet agents—Aspirin—Peripheral arterial disease—Ticlopidine—Clopidogrel—GPIIb/IIIa inhibitor.

Silicon Carbide-Coated Stents: Clinical Experience in Coronary Lesions with Increased Thrombotic Risk

Purpose:

To report the results of a prospective, nonrandomized, multicenter study of a semiconductor-coated stent in coronary lesions at high risk for stent thrombosis.

Methods:

A balloon-expandable tantalum stent was coated with silicon carbide to enhance thromboresistance (Tensum). Patients were enrolled in an observational study that compared coronary stenting with the Tensum stent in patients at low risk for stent thrombosis against those with factors predisposing to local thrombosis (acute myocardial infarction, small vessel diameter, recanalized chronic total occlusion, saphenous vein bypass grafts, and coronary allograft vascular disease).

Results:

In 294 patients with 364 coronary lesions, 111 patients with 142 lesions were assigned to the high-risk group. Overall, 406 Tensum stents were implanted (94% procedural success) using antiplatelet medication only after the procedure. The stent thrombosis rate (2.7% overall) in the high-risk group (3.6%) was not significantly different from that of the low-risk patients (2.1%).

Conclusions:

Silicon carbide coating on coronary stents may inhibit acute/subacute stent thrombosis even in patients at high risk. Randomized trials are underway for further evaluation of this promising coated stent.

The History of Coronary Stenting

The history of coronary angioplasty began with the groundbreaking work of Andreas Grüntzig, who was the first to use balloon-expandable catheters for the treatment of flow-limiting atherosclerotic coronary artery lesions. Thereafter, early investigators tested self-expanding springs as a solution to abrupt closure and restenosis seen with balloon angioplasty but these devices suffered from difficult delivery and a high complication rate. Julio Palmaz and Richard Schatz introduced the first balloon-expandable stent as a mechanical support to improve vessel patency. Their pioneering work launched a new era in the treatment of coronary artery disease.

Hemodynamic Performance and Thrombogenic Properties of a Superhydrophobic Bileaflet Mechanical Heart Valve

In this study, we explore how blood-material interactions and hemodynamics are impacted by rendering a clinical quality 25 mm St. Jude Medical Bileaflet mechanical heart valve (BMHV) superhydrophobic (SH) with the aim of reducing thrombo-embolic complications associated with BMHVs. Basic cell adhesion is evaluated to assess blood-material interactions, while hemodynamic performance is analyzed with and without the SH coating. Results show that a SH coating with a receding contact angle (CA) of 160° strikingly eliminates platelet and leukocyte adhesion to the surface. Alternatively, many platelets attach to and activate on pyrolytic carbon (receding CA = 47), the base material for BMHVs. We further show that the performance index increases by 2.5% for coated valve relative to an uncoated valve, with a maximum possible improved performance of 5%. Both valves exhibit instantaneous shear stress below 10 N/m² and Reynolds Shear Stress below 100 N/m². Therefore, a SH BMHV has the potential to relax the requirement for antiplatelet and anticoagulant drug regimens typically required for patients receiving MHVs by minimizing blood-material interactions, while having a minimal impact on hemodynamics. We show for the first time that SH-coated surfaces may be a promising direction to minimize thrombotic complications in complex devices such as heart valves.

Antiplatelet Therapy in Percutaneous Coronary Intervention

Platelets play a key role in mediating stent thrombosis, which is the major cause of ischemic events immediately after percutaneous coronary intervention (PCI). Antiplatelet therapy is therefore the cornerstone of antithrombotic therapy after PCI. However, the use of antiplatelet agents increases bleeding risk, with more potent antiplatelet agents further increasing bleeding risk. In the past 5 years, potent and fast-acting P2Y12 inhibitors have augmented the antiplatelet armamentarium available to interventional cardiologists. This article reviews the preclinical and clinical data surrounding these new agents, and discusses the significant questions and controversies that still exist regarding the optimal antiplatelet strategy.

Layer-by-layer self-assembled thin films of chitin fibers and heparin with anti-thrombus characteristics

Layer-by-layer assembled films of chitin nanofibers and heparin with anti-thrombus characteristics.

Preclinical evaluation of the thrombogenicity and endothelialization of bare metal and surface-coated neurovascular stents

BACKGROUND AND PURPOSE

Stent-assisted coiling is routinely used for the endovascular treatment of complex or wide-neck intracranial aneurysms. However, in-stent thrombosis, thromboembolic events, and ischemic complications remain a major concern associated with stent implants. Therefore, a novel low-profile neurovascular stent with a bare metal surface was investigated with regard to thrombogenicity and endothelialization and compared with the same stent coated with albumin or heparin.

MATERIALS AND METHODS

The bare metal and heparin- or albumin-coated stents were loaded in heparin-coated tubing, which was then filled with heparinized human blood (n = 5) and circulated at 150 mL/min and 37°C for 60 minutes. Before and after circulation, measurement of various inflammation and coagulation markers and scanning electron microscopy were performed. Endothelialization of the stents was investigated in an in vitro model including human umbilical vascular endothelial cells.

RESULTS

Our results showed that platelet loss and platelet activation and activation of the coagulation cascade, which are induced by the bare metal stents, were significantly reduced by heparin or albumin coating. Adverse effects on erythrocytes, leukocytes, and the complement cascade were not induced by the bare metal or coated stents. Moreover, the bare metal and albumin-coated stents showed good endothelialization properties.

CONCLUSIONS

Albumin and heparin coatings clearly improve the thrombogenicity of the stents and thus may represent fundamental progress in the treatment of intracranial aneurysms. Moreover, preclinical evaluation of neurovascular stents under physiologic conditions supports and accelerates the development of more biocompatible neurovascular stents.

Biofunctionalized anti-corrosive silane coatings for magnesium alloys

Biodegradable magnesium alloys are advantageous in various implant applications, as they reduce the risks associated with permanent metallic implants. However, a rapid corrosion rate is usually a hindrance in biomedical applications. Here we report a facile two step procedure to introduce multifunctional, anti-corrosive coatings on Mg alloys, such as AZ31. The first step involves treating the NaOH-activated Mg with bistriethoxysilylethane to immobilize a layer of densely crosslinked silane coating with good corrosion resistance; the second step is to impart amine functionality to the surface by treating the modified Mg with 3-amino-propyltrimethoxysilane. We characterized the two-layer anticorrosive coating of Mg alloy AZ31 by Fourier transform infrared spectroscopy, static contact angle measurement and optical profilometry, potentiodynamic polarization and AC impedance measurements. Furthermore, heparin was covalently conjugated onto the silane-treated AZ31 to render the coating haemocompatible, as demonstrated by reduced platelet adhesion on the heparinized surface. The method reported here is also applicable to the preparation of other types of biofunctional, anti-corrosive coatings and thus of significant interest in biodegradable implant applications.

First-in-man evaluation of the MOMO cobalt-chromium carbon-coated stent

AIMS

Bare metal stents continue to be used for the interventional treatment of coronary artery disease. We report the clinical and angiographic results of a multicentre, single-arm evaluation of safety and feasibility of the MOMO stent (Japan Stent Technology Co., Ltd, Okayama Research Park Incubation Centre, Okayama, Japan).

METHODS AND RESULTS

The MOMO stent is a novel thin-strut cobalt-chromium carbon-coated stent for the treatment of de novo coronary artery disease (CAD). In this prospective, non-randomised, single-arm study, 40 patients (stable and unstable angina) with single-vessel CAD were recruited into the study from three centres. Patients with lesions ≤15 mm in length and with a target vessel diameter of ≥3 mm were eligible. Angiographic follow-up was performed at six months. Quantitative coronary angiography (QCA) was used to measure acute gain and late luminal loss (LLL). Intravascular ultrasound (IVUS) was performed in 15 consecutive patients from two centres to assess the degree of neointimal proliferation within the stented segment at six-month follow-up. The MOMO stent performed well without any procedural complications with an acute procedure and technical success rate of 100%. Repeat revascularisation was performed in six patients (15%) during the six-month follow-up. Ischaemia-driven revascularisation was documented in three patients (7.5%). No myocardial infarction, stent thrombosis or cardiac death was observed. One non-cardiac death was reported secondary to lung cancer. Binary restenosis was 12.5% (n=5), and the LLL was 0.54±0.3 mm.

CONCLUSIONS

This first-in-man experience demonstrates proof of concept of the safety and feasibility of the MOMO cobalt-chromium carbon-coated stent for patients with single focal de novo lesions presenting with stable and unstable CAD.

Novel stents for the prevention of restenosis

Since the introduction of Interventional Cardiology in 1976, there has been rapid expansion both in its clinical application and the tools of the trade. This growth was accelerated with the introduction of the intra-coronary stent in 1987. The demonstration that stents may reduce the incidence of restenosis after percutaneous coronary revascularization has further stimulated the search for the perfect endovascular prosthesis. By creating a hybrid stent, incorporating natural coatings and local drug delivery in the design, it is hoped that the complications associated with stent thrombosis and restenosis can be eradicated. (Trends Cardiovasc Med 1997;7:245-249). © 1997, Elsevier Science Inc.

Impact of metabolic syndrome on re-stenosis development: role of drug-eluting stents

Metabolic syndrome (MetS) is defined as a cluster of numerous cardiovascular risk factors, which encompasses obesity, dyslipidaemia, insulin resistance and hypertension. Patients with MetS are more prone to developing cardiovascular events than other patients. To date, several approaches such as physical exercise, dietary control and invasive and non-invasive therapeutic interventions for dyslipidaemia, hypertension and insulin resistance have been used to manage MetS. However, there is a progressive elevation in the incidence of fatal and non-fatal cardiovascular events due to the increased prevalence of obesity and diabetes. Percutaneous coronary intervention has emerged over the last few years as an effective revascularisation strategy for those with coronary artery disease, in parallel with the development of effective anti-platelet medications and newer drug-eluting stents. In recent years, considerable research efforts have been undertaken to elucidate the pathophysiology of re-stenosis and develop strategies to prevent re-stenosis following percutaneous transluminal coronary angioplasty and stent implantation. Although the rate of stent re-stenosis and target-lesion revascularisation has been reduced, there is little information in the literature on the outcome of MetS in the pathophysiology of re-stenosis. In this review article, we summarise the recent development and progress on re-stenosis and the role of drug-eluting stents, particularly in MetS.

Arterial pharmacokinetics of red wine polyphenols: implications for novel endovascular therapies targeting restenosis

Drug-eluting stents (DESs) are endovascular devices that provide controlled release of compounds to interfere with restenosis, an adverse outcome of angioplasty characterized by thickening of the arterial wall. Accumulating evidence suggests that arterial pharmacokinetics determine the biological effect and potential toxicity of stent-based therapeutics. The aim of this study was to examine how drug polarity, drug load, and protein binding influence release from a polymer film and distribution within arterial tissue. The transport and safety profile of resveratrol (RESV) and quercetin (QUER), two red wine polyphenols known to interfere with events in the pathogenesis of restenosis, were compared with paclitaxel (Taxol), a lipophilic drug used in DES. In bovine arteries, RESV showed considerable protein binding and arterial kinetics that were found to mimick Taxol. In contrast, the less lipophilic QUER showed limited tissue distribution. Measured diffusivity of RESV and QUER was coupled with a novel computational method for assessment of biphasic drug release kinetics and arterial drug retention profiles. Modeling revealed that drugs associated with high- and low-protein-binding affinity result in markedly distinct arterial drug profiles. These data underscore the importance of arterial partitioning and propagation of drug within arterial tissue in the rational design of DES coatings.

IVUS-Guided Stent Implantation to Improve Outcome: A Promise Waiting to be Fulfilled

The use of intravascular ultrasound (IVUS) to improve acute angiographic results was already shown in the prestent era. Various studies demonstrated the efficacy of IVUS in balloon sizing and estimating the extent of positive remodeling. With the introduction of drug-eluting stents (DES) the rate of restenosis has been significantly reduced but a new concern, the risk of stent thrombosis, has emerged. The association of stent underexpansion with stent thrombosis was observed for bare metal stents (BMS) and DES. Until now, the criteria for IVUS optimization used in different studies have relied on distal reference or on mean reference vessel for stent or postdilatation balloon sizing. Furthermore, an important recent innovation not available in previous studies is the use of noncompliant balloons to perform high pressure post-dilatation. Universal and easily applicable IVUS criteria for optimization of stent implantation as well as randomized studies on IVUS-guided DES implantation are necessary to minimize stent malapposition and underexpansion, which in turn can positively influence the rates of stent restenosis and thrombosis.

Comparison of in vivo eccentricity and symmetry indices between metallic stents and bioresorbable vascular scaffolds: insights from the ABSORB and SPIRIT trials

OBJECTIVE

To compare the geometrical parameters of a bioresorbable vascular scaffold (BVS) with a standard metallic stent.

BACKGROUND

The introduction of polymeric bioresorbable materials in the design of novel coronary scaffolds may affect some geometrical parameters, such as eccentricity and symmetry indices, previously introduced as IVUS criteria for optimal metallic stent deployment.

METHODS

From ABSORB Cohort A, ABSORB Cohort B, SPIRIT I, and SPIRIT II, all patients implanted with BVS 1.0, BVS 1.1, or XIENCE V, respectively and intravascular ultrasound analyses post-implantation were selected. The eccentricity index was calculated frame by frame and expressed as an average per device (minimum diameter/maximum diameter). The symmetry index of the device was reported as ([maximum diameter - minimum diameter]/maximum diameter). Six months major adverse cardiac events (MACE) were analyzed.

RESULTS

A total of 242 patients were selected (BVS 1.0: n = 28, BVS 1.1: n = 94, XIENCE V: n = 120). The BVS exhibited a significantly lower eccentricity index (BVS 1.0: 0.83 ± 0.09; BVS 1.1: 0.85 ± 0.08; XIENCE V: 0.90 ± 0.06; P < 0.01) and a significantly higher symmetry index (BVS 1.0: 0.30 ± 0.07; BVS 1.1: 0.31 ± 0.06, XIENCE V 0.26 ± 0.07; P < 0.01) as compared to the XIENCE V. An inverse correlation was found between the symmetry and eccentricity indices for both (BVS r = -0.69, P < 0.01; XIENCE V r = -0.61, P < 0.01). No differences in MACE were detected between the groups according to their geometrical parameters.

CONCLUSIONS

The introduction of a new polymeric material in the design of BVS resulted in a lower eccentricity index and a higher symmetry index as compared to metallic stents, without detectable impact in MACE, at 6 months.

The New Era of Cardiac Surgery Hybrid Therapy for Cardiovascular Disease

Surgical therapy for cardiovascular disease carries excellent long-term outcomes but it is relatively invasive. With the development of new devices and techniques, modern cardiovascular surgery is trending toward less invasive approaches, especially for patients at high risk for traditional open heart surgery. A hybrid strategy combines traditional surgical treatments performed in the operating room with treatments traditionally available only in the catheterization laboratory with the goal of offering patients the best available therapy for any set of cardiovascular diseases. Examples of hybrid procedures include hybrid coronary artery bypass grafting, hybrid valve surgery and percutaneous coronary intervention, hybrid endocardial and epicardial atrial fibrillation procedures, and hybrid coronary artery bypass grafting/carotid artery stenting. This multi-disciplinary approach requires strong collaboration between cardiac surgeons, vascular surgeons, and interventional cardiologists to obtain optimal patient outcomes.

Reduced incidence of clinical restenosis with newer generation stents, stent oversizing, and high-pressure deployment: single-operator experience

BACKGROUND

Over the last 4 years, several newer generation stents have become available, promising to change the scenery of coronary angioplasty (PTCA) with its attendant restenosis rate.

HYPOTHESIS

The aim of this study was to review prospectively the results of a single operator adopting a uniform approach with approximately 0.5 mm stent oversizing and high-pressure (> or = 12-16 bar) deployment and compare them with conventional PTCA in a series of 244 consecutive patients.

METHODS

The study included 203 men and 41 women, aged 59 +/- 11 years, who presented with stable angina and/or positive exercise testing (n = 75), unstable angina (n = 161), or acute myocardial infarction (n = 8). Dilated vessels included the left anterior descending artery (n = 139), the right coronary artery (n = 86), the left circumflex artery (n = 47), the ramus branch (n = 4), or venous grafts (n = 2). Stents were implanted for dissection, suboptimal PTCA result, and electively. Two groups were compared: 83 patients who underwent balloon PTCA alone and 161 patients who also received stent(s).

RESULTS

The two groups had similar demographics, age (58 +/- 10 vs. 59 +/- 11 years), initial vessel stenosis (92 +/- 7 vs. 93 +/- 6%), and left ventricular ejection fraction (51 +/- 9 vs. 51 +/- 8%). Procedural success was also similar (97.6 vs. 99.4%), but as expected the residual stenosis was much lower in the stent group (< or = 0 vs. 17%). The following stents were employed: J & J (n = 1), NIR (n = 117), ACS (n = 59), AVE (n = 9), Inflow GoldFlex (n = 9), Crossflex (n = 5), Wictor (n = 1), Jostent (n = 16), R stent (n = 9), Seaquence (n = 2) and Wallstent (n = 1). Single stents were used in 118 patients, two stents in 31 patients, three in 6 patients, and four in 6 patients. There was one in-hospital death at 3 days unrelated to the procedure. There were no events of subacute stent thrombosis; all patients in the stent group received combined therapy with aspirin and ticlopidine, the latter for 1 month. During 18 +/- 14 months, the clinical restenosis rate was significantly lower in the stent group (6.9%) than in the PTCA group (28.4%) (p = 0.001).

CONCLUSION

In a series of 244 consecutive patients, newer generation stents and a consistent approach of stent oversizing and high-pressure stent deployment by a single operator resulted in high procedural success (99%), lack of stent thrombosis (0%), and a very low clinical restenosis rate (7%).

Prediction of Functional Outcome in Stunned Myocardium after Myocardial Infarction using BMIPP and Tetrofosmin Imaging

The predictive value of combined 123iodine-labelled 15-( p-iodophenyl)-3 R,S-methyl pentadecanoic acid imaging (123I-BMIPP) and early technetium-99m (99mTc)-tetrofosmin imaging was compared with combined 123I-BMIPP and delayed 99mTc-tetrofosmin or 123I-BMIPP and thallium-201 (201Tl) imaging for functional outcome of stunned myocardium after acute myocardial infarction (AMI) in 37 patients with AMI. All patients underwent successful percutaneous coronary intervention with/without stenting within 24 h of symptoms. Resting 201Tl, 99mTc-tetrofosmin and 123I-BMIPP imaging were performed within 10 days of hospital admission; 99mTc-tetrofosmin imaging was also performed 6 months later. Segments were mismatched when the 123I-BMIPP score was greater than the 99mTc-tetrofosmin or 201Tl scores, and were matched when all scores were the same. Left ventricular function was estimated using wall motion score. Sensitivity and regional wall motion were significantly better in mismatching 99mTc-tetrofosmin-early/123I-BMIPP segments than mismatching 201Tl/123I-BMIPP or 99mTc-tetrofosmin-delayed/123I-BMIPP segments. It is concluded that mismatching of 123I-BMIPP and early 99mTc-tetrofosmin uptake can predict improvement in wall motion of stunned myocardium better than the other two imaging combinations.

Cell adhesion and proliferation are reduced on stainless steel coated with polysaccharide-based polymeric formulations

Hydromer's polymeric formulations F200 and F202 were evaluated after application to a synthetic substrate for effects on cell adhesion and proliferation. A significant reduction in cell adhesion was observed when cells grown on medical-grade stainless steel coated with these polymers were stained and examined under a fluorescence microscope. This reduction in cell adhesion/proliferation was confirmed when cells were isolated and analyzed by the MTS cell proliferation assay. The rate of growth of cells on F200- and F202-coated stainless steel monitored over a period of 7 days was significantly less than that observed on uncoated stainless steel, suggesting that the rate of growth of cells was reduced. The adhesion/proliferation of human umbilical vein endothelial cells (HUVEC) to coated substrates was also decreased significantly, indicating that the reduction in cell adhesion/proliferation is not restricted to only fibroblasts. Additional studies have indicated that the adhesion/proliferation of murine fibroblasts and human endothelial cells to stainless coated with a modified formulation exhibiting a high degree of lubricity was also significantly reduced. This lubricious formulation was also observed to be effective in reducing platelet adhesion, data supporting the view that lubricity also contributes to a reduction in cell and platelet adhesion. The application of these polymeric coatings on devices designed for medical implantation may not only prevent thrombus formation but may also retard the process of restenosis.

Critical overview of Nitinol surfaces and their modifications for medical applications

Nitinol, a group of nearly equiatomic shape memory and superelastic NiTi alloys, is being extensively explored for medical applications. Release of Ni in the human body, a potential problem with Nitinol implant devices, has stimulated a great deal of research on its surface modifications and coatings. In order to use any of the developed surfaces in implant designs, it is important to understand whether they really have advantages over bare Nitinol. This paper overviews the current situation, discusses the advantages and disadvantages of new surfaces as well as the limitations of the studies performed. It presents a comprehensive analysis of surface topography, chemistry, corrosion behavior, nickel release and biological responses to Nitinol surfaces modified mechanically or using such methods as etching in acids and alkaline solutions, electropolishing, heat and ion beam treatments, boiling in water and autoclaving, conventional and ion plasma implantations, laser melting and bioactive coating deposition. The analysis demonstrates that the presently developed surfaces vary in thickness from a few nanometers to micrometers, and that they can effectively prevent Ni release if the surface integrity is maintained under strain and if no Ni-enriched sub-layers are present. Whether it is appropriate to use various low temperature pre-treatment protocols (< or = 160 degrees C) developed originally for pure titanium for Nitinol surface modifications and coatings is also discussed. The importance of selection of original Nitinol surfaces with regard to the performance of coatings and comparative performance of controls in the studies is emphasized. Considering the obvious advantages of bare Nitinol surfaces for superelastic implants, details of their preparation are also outlined.

Application of paclitaxel-eluting metal stents in renal artery of pig model

BACKGROUND AND PURPOSE

Recent reports concerning coronary, carotid, and femoral vasculature have proposed the use of drug-eluting metal stents (MS) to improve clinical and angiographic outcomes. Based on these reports, we used paclitaxel-eluting MS within an animal renal artery lumen and compared the results with those using a bare-metal stent.

MATERIALS AND METHODS

The experimental model in this study was the female pig renal artery. Ten pigs with weights ranging from 25 to 30 kg were used. Twenty stents were placed, two in each animal. The MS placement was randomly performed in either the right or left renal artery of each animal. In 10 arteries, a 3.5 x 18 mm R-stent (group A) was placed; in the remaining 10 arteries, a 3 x 32 mm paclitaxel-eluting coronary stent (T-stent, group B) was inserted. Patency was estimated with the use of digital subtraction angiography, CT angiography, and virtual endoscopy at 24 hours and 1 month poststent placement.

RESULTS

The positioning of the MS was successful in all cases. The initial angiographic result was maintained 24 hours after the intervention. No stent migration was seen, except for one paclitaxel stent that was acutely occluded. The one-month patency rate, as demonstrated by angiography, CT angiography, and virtual endoscopy, was 70% (8 arteries) in group A and 90% (9 arteries) in group B. The thickness of the endothelium and of the muscular coat was statistically significantly less in group B compared with group A (P = 0.0352 and P = 0.0046, respectively).

CONCLUSION

These preliminary experimental study results suggest that the paclitaxel-eluting MS is more efficient than the bare-metal stent when used within the pig renal artery. Further experimental and clinical studies are necessary to validate our preliminary encouraging results.

Human umbilical vein versus heparin-bonded polyester for femoro-popliteal bypass: 5-year results of a prospective randomized multicentre trial

PURPOSE

To compare long-term patency of Heparin-Bonded Dacron (HBD) and Human Umbilical Vein (HUV) vascular prostheses in above-knee femoro-popliteal bypass surgery.

DESIGN

A prospective randomized multi-centre clinical trial.

PATIENTS AND METHODS

Femoro-popliteal bypasses were performed in 129 patients between 1996 and 2001. After randomization 70 patients received an HUV and 59 an HBD prosthesis. Patients were followed up every three months during the first postoperative year and yearly thereafter. The median follow-up was 60 months (range 3-96 months). Graft occlusions were detected by duplex scanning, angiography or surgical exploration.

RESULTS

The cumulative primary patency rates were 79%, 66% and 58% at 1, 3 and 5 years postoperatively. Primary patency rates for HUV were 74%, 64% and 58% at 1, 3 and 5 years and 84%, 68% and 58% for HBD, respectively (log-rank test, p=0.745). Overall secondary patency rates were 82%, 72% and 61% at 1, 3 and 5 years postoperatively. The overall cumulative limb salvage at 5 years follow-up was 89% (CI 80%-91%) and was not dependent on graft type. Smoking (p=0.019), number of patent crural arteries (p=0.030) and previous cerebro-vascular events (p=0.030) were significant predictors of graft occlusion.

CONCLUSION

There was no difference in long-term graft performance between HUV and HBD for above knee infrainguinal bypass.

Delivery of large biopharmaceuticals from cardiovascular stents: a review

This review focuses on new and emerging large-molecule bioactive agents delivered from stent surfaces in drug-eluting stents (DESs) to inhibit vascular restenosis in the context of interventional cardiology. New therapeutic agents representing proteins, nucleic acids (small interfering RNAs and large DNA plasmids), viral delivery vectors, and even engineered cell therapies require specific delivery designs distinct from traditional smaller-molecule approaches on DESs. While small molecules are currently the clinical standard for coronary stenting, extension of the DESs to other lesion types, peripheral vasculature, and nonvasculature therapies will seek to deliver an increasingly sophisticated armada of drug types. This review describes many of the larger-molecule and biopharmaceutical approaches reported recently for stent-based delivery with the challenges associated with formulating and delivering these drug classes compared to the current small-molecule drugs. It also includes perspectives on possible future applications that may improve safety and efficacy and facilitate diversification of the DESs to other clinical applications.

Applying drug-eluting stents in clinical practice

The use of percutaneous coronary interventions has resulted in significant improvement in patient care; however, the risk for restenosis remains a major limitation. Drug-eluting stents represent an impressive breakthrough in the evolution of interventional cardiology, but it is important to understand the limits to their added benefit. Safety of the procedure must continue to be the first consideration, and technique must not be compromised to accommodate new technology.

Heparin bioconjugate with a thermoresponsive cationic branched polymer: a novel aqueous antithrombogenic coating material

With a view to reducing the thrombogenic potential of artificial blood-contact devices and natural tissues, we developed a novel aqueous antithrombogenic coating material, comprising a heparin bioconjugate that incorporated a thermoresponsive cationic polymer as a surfactant. The polymer was prepared by the sequential steps of initiator-transfer agent-terminator (iniferter)-based living radical photopolymerization of N-[3-(dimethylamino)propyl]acrylamide, followed by the polymerization of N-isopropylacrylamide from tetra(N,N-diethyldithiocarbamylmethyl)benzene as a multifunctional iniferter. The polymer obtained possessed four branched chains, each consisting of a cationic PDMAPAAm block (Mn: ca. 3000 g.mol(-1)) forming an inner domain for heparin binding and a thermoresponsive PNIPAM block (Mn: ca. 6000 g.mol(-1)) forming an outer domain for surface fixation; bioconjugation of the polymer with heparin occurred immediately upon simple mixing in an aqueous medium. Because the lower critical solution temperature of the heparin bioconjugate was approximately 35 degrees C, it could be coated from an aqueous solution at room temperature. The excellent adsorptivity and high durability of the coating below 37 degrees C was demonstrated on several generally used polymers by wettability measurement and surface chemical compositional analysis, and on collagen sheets and rat skin tissue by heparin staining. Blood coagulation was significantly prevented on the heparin bioconjugate-coated surfaces. The thermoresponsive bioconjugate developed therefore appeared to satisfy the initial requirements for a biocompatible aqueous coating material.

Impact of 6-Month Angiographic Restenosis Inside Bare-Metal Stents on Long-Term Clinical Outcome in Patients With Coronary Artery Disease

This study enrolled 536 patients who underwent successful coronary stenting with bare-metal stents and 6-month angiographic follow-up examinations between 1998 and 2000. Baseline characteristics and angiographic and procedural parameters for these patients were obtained. Primary endpoints were all-cause mortality and nonfatal myocardial infarction. Patients were assigned to instent restenosis or non-instent restenosis groups based on 6-month angiographic follow-up results. Restenosis inside a bare-metal stent was defined as more than 50% stenosis at the intervention site. In total, 178 (33.2%) patients had restenosis inside bare-metal stents, while 358 (66.8%) patients were without. At mean follow-up of 56.8 +/- 20.3 months, 36 (6.7%) patients had a primary endpoint event while 500 (93.3%) patients had no primary endpoint event. Survival rates for patients free from primary endpoints in the instent restenosis and non-instent restenosis groups were 96.0 versus 99.4% at 1 year and 89.8% versus 94.8% at 5 years, respectively (P = 0.0033). Survival rates for patients free of all-cause mortality in the instent restenosis and non-instent restenosis groups were 96.0% versus 99.4% at 1 year and 91.6% versus 96.3% at 5 years, respectively (P = 0.0079). Multivariate Cox regression analysis showed that restenosis inside bare-metal stents was an independent predictor of primary endpoint events (odds ratio: 2.053; 95% CI: 1.048-4.022; P = 0.036) and was a predictor of total mortality with borderline significance (odds ratio: 2.036; 95% CI: 0.936-4.431; P = 0.073). In conclusion, in this study, restenosis inside bare-metal stents at 6-month angiographic follow-up was an independent predictor of long-term outcome-all-cause mortality and nonfatal myocardial infarction. Thus, this study provides clinical evidence that patients with restenosis inside bare-metal stents at 6-month angiographic follow-up likely warrant aggressive follow-up.