Silicon carbide-coated stents in patients with acute coronary syndrome

Effect of oxidation on intrinsic residual stress in amorphous silicon carbide films

The change in residual stress in plasma enhanced chemical vapor deposition amorphous silicon carbide (a-SiC:H) films exposed to air and wet ambient environments is investigated. A close relationship between stress change and deposition condition is identified from mechanical and chemical characterization of a-SiC:H films. Evidence of amorphous silicon carbide films reacting with oxygen and water vapor in the ambient environment are presented. The effect of deposition parameters on oxidation and stress variation in a-SiC:H film is studied. It is found that the films deposited at low temperature or power are susceptible to oxidation and undergo a notable increase in compressive stress over time. Furthermore, the films deposited at sufficiently high temperature (≥325 C) and power density (≥0.2 W cm^-2 ) do not exhibit pronounced oxidation or temporal stress variation. These results serve as the basis for developing amorphous silicon carbide based dielectric encapsulation for implantable medical devices. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1654-1661, 2019.

Drug-eluting stents versus bare-metal stents for acute coronary syndrome

BACKGROUND

Approximately 3.7 million people died from acute coronary syndrome worldwide in 2012. Acute coronary syndrome, also known as myocardial infarction or unstable angina pectoris, is caused by a sudden blockage of the blood supplied to the heart muscle. Percutaneous coronary intervention is often used for acute coronary syndrome, but previous systematic reviews on the effects of drug-eluting stents compared with bare-metal stents have shown conflicting results with regard to myocardial infarction; have not fully taken account of the risk of random and systematic errors; and have not included all relevant randomised clinical trials.

OBJECTIVES

To assess the benefits and harms of drug-eluting stents versus bare-metal stents in people with acute coronary syndrome.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, LILACS, SCI-EXPANDED, and BIOSIS from their inception to January 2017. We also searched two clinical trials registers, the European Medicines Agency and the US Food and Drug Administration databases, and pharmaceutical company websites. In addition, we searched the reference lists of review articles and relevant trials.

SELECTION CRITERIA

Randomised clinical trials assessing the effects of drug-eluting stents versus bare-metal stents for acute coronary syndrome. We included trials irrespective of publication type, status, date, or language.

DATA COLLECTION AND ANALYSIS

We followed our published protocol and the methodological recommendations of Cochrane. Two review authors independently extracted data. We assessed the risks of systematic error by bias domains. We conducted Trial Sequential Analyses to control the risks of random errors. Our primary outcomes were all-cause mortality, major cardiovascular events, serious adverse events, and quality of life. Our secondary outcomes were angina, cardiovascular mortality, and myocardial infarction. Our primary assessment time point was at maximum follow-up. We assessed the quality of the evidence by the GRADE approach.

MAIN RESULTS

We included 25 trials randomising a total of 12,503 participants. All trials were at high risk of bias, and the quality of evidence according to GRADE was low to very low. We included 22 trials where the participants presented with ST-elevation myocardial infarction, 1 trial where participants presented with non-ST-elevation myocardial infarction, and 2 trials where participants presented with a mix of acute coronary syndromes.Meta-analyses at maximum follow-up showed no evidence of a difference when comparing drug-eluting stents with bare-metal stents on the risk of all-cause mortality or major cardiovascular events. The absolute risk of death was 6.97% in the drug-eluting stents group compared with 7.74% in the bare-metal stents group based on the risk ratio (RR) of 0.90 (95% confidence interval (CI) 0.78 to 1.03, 11,250 participants, 21 trials/22 comparisons, low-quality evidence). The absolute risk of a major cardiovascular event was 6.36% in the drug-eluting stents group compared with 6.63% in the bare-metal stents group based on the RR of 0.96 (95% CI 0.83 to 1.11, 10,939 participants, 19 trials/20 comparisons, very low-quality evidence). The results of Trial Sequential Analysis showed that we did not have sufficient information to confirm or reject our anticipated risk ratio reduction of 10% on either all-cause mortality or major cardiovascular events at maximum follow-up.Meta-analyses at maximum follow-up showed evidence of a benefit when comparing drug-eluting stents with bare-metal stents on the risk of a serious adverse event. The absolute risk of a serious adverse event was 18.04% in the drug-eluting stents group compared with 23.01% in the bare-metal stents group based on the RR of 0.80 (95% CI 0.74 to 0.86, 11,724 participants, 22 trials/23 comparisons, low-quality evidence), and Trial Sequential Analysis confirmed this result. When assessing each specific type of adverse event included in the serious adverse event outcome separately, the majority of the events were target vessel revascularisation. When target vessel revascularisation was analysed separately, meta-analysis showed evidence of a benefit of drug-eluting stents, and Trial Sequential Analysis confirmed this result.Meta-analyses at maximum follow-up showed no evidence of a difference when comparing drug-eluting stents with bare-metal stents on the risk of cardiovascular mortality (RR 0.91, 95% CI 0.76 to 1.09, 9248 participants, 14 trials/15 comparisons, very low-quality evidence) or myocardial infarction (RR 0.98, 95% CI 0.82 to 1.18, 10,217 participants, 18 trials/19 comparisons, very low-quality evidence). The results of the Trial Sequential Analysis showed that we had insufficient information to confirm or reject our anticipated risk ratio reduction of 10% on cardiovascular mortality and myocardial infarction.No trials reported results on quality of life or angina.

AUTHORS' CONCLUSIONS

The current evidence suggests that drug-eluting stents may lead to fewer serious adverse events compared with bare-metal stents without increasing the risk of all-cause mortality or major cardiovascular events. However, our Trial Sequential Analysis showed that there currently was not enough information to assess a risk ratio reduction of 10% for all-cause mortality, major cardiovascular events, cardiovascular mortality, or myocardial infarction, and there were no data on quality of life or angina. The evidence in this review was of low to very low quality, and the true result may depart substantially from the results presented in this review.More randomised clinical trials with low risk of bias and low risks of random errors are needed if the benefits and harms of drug-eluting stents for acute coronary syndrome are to be assessed properly. More data are needed on the outcomes all-cause mortality, major cardiovascular events, quality of life, and angina to reduce the risk of random error.

In vivo Characterization of Amorphous Silicon Carbide As a Biomaterial for Chronic Neural Interfaces

Implantable microelectrode arrays (MEAs) offer clinical promise for prosthetic devices by enabling restoration of communication and control of artificial limbs. While proof-of-concept recordings from MEAs have been promising, work in animal models demonstrates that the obtained signals degrade over time. Both material robustness and tissue response are acknowledged to have a role in device lifetime. Amorphous Silicon carbide (a-SiC), a robust material that is corrosion resistant, has emerged as an alternative encapsulation layer for implantable devices. We systematically examined the impact of a-SiC coating on Si probes by immunohistochemical characterization of key markers implicated in tissue-device response. After implantation, we performed device capture immunohistochemical labeling of neurons, astrocytes, and activated microglia/macrophages after 4 and 8 weeks of implantation. Neuron loss and microglia activation were similar between Si and a-SiC coated probes, while tissue implanted with a-SiC displayed a reduction in astrocytes adjacent to the probe. These results suggest that a-SiC has a similar biocompatibility profile as Si, and may be suitable for implantable MEA applications as a hermetic coating to prevent material degradation.

Difference in clinical target lesion revascularization between a silicon carbide-coated and an uncoated thin strut bare-metal stent: the PRO-Vision study

BACKGROUND

Bare-metal stents trigger a foreign body reaction, resulting in neointima formation and restenosis. Silicon carbide (SiC) coating shields the metal from circulating blood and vessel wall, both potential sources of neointima smooth muscle cells.

METHODS

We investigated whether SiC-coated stents (PRO-Kinetic) have lower clinical target lesion revascularization (TLR) rates than do uncoated bare-metal stents (Vision). Stents were implanted in 2731 patients during 2 consecutive 18-month periods. Clinical TLR was evaluated at 1 year.

RESULTS

In the PRO-Kinetic group, TLR was significantly higher (9.0% vs 5.6%; unadjusted odds ratio, 1.61; 95% confidence interval [CI], 1.24-2.08; P < 0.001) compared with the Vision group. After adjustment for postintervention minimal luminal diameter (adjusted odds ratio [AOR], 0.56; 95% CI, 0.42-0.73), total implanted stent length (AOR, 1.01; 95% CI, 1.00-1.02), non-ST-segment elevation myocardial infarction or unstable angina at initial presentation (AOR, 1.89; 95% CI, 1.41-2.54), and triple vessel stenting (AOR, 2.68; 95% CI, 1.02-7.05), the use of PRO-Kinetic stents remained an independent predictor for revascularization (AOR, 1.57; 95% CI, 1.18-2.10; P = 0.002). Because strut thickness is lower in 2.0- to 3.0-mm PRO-Kinetic stents, a subgroup analysis (n = 2382 lesions) was performed. Even in this subgroup, PRO-Kinetic implantation proved an independent predictor of TLR (AOR, 1.62; 95% CI, 1.17-2.23; P = 0.003).

CONCLUSION

In contrast to theoretical expectations, the SiC-coated PRO-Kinetic stent was associated with greater target lesion revascularization rates at 1 year compared with the uncoated Vision stent.

RADAR - A randomised, multi-centre, prospective study comparing best medical treatment versus best medical treatment plus renal artery stenting in patients with haemodynamically relevant atherosclerotic renal artery stenosis

BACKGROUND

Prospective, international, multi-centre, randomised (1:1) trial to evaluate the clinical impact of percutaneous transluminal renal artery stenting (PTRAS) on the impaired renal function measured by the estimated glomerular filtration rate (eGFR) in patients with haemodynamically significant atherosclerotic renal artery stenosis.

METHODS

Patients will be randomised to receive either PTRAS using the Dynamic Renal Stent system plus best medical treatment or best medical treatment. Renal stenting will be performed under angiographic imaging. For patients randomised to best medical treatment the degree of stenosis measured by renal duplex sonography (RDS) will be confirmed by MR angio or multi-slice CT where possible. Best medical treatment will be initiated at randomisation or post procedure (for PTRAS arm only), and adjusted as needed at all visits. Best medical treatment is defined as optimal drug therapy for control of the major risk factors (blood pressure < or = 125/80 mmHg, LDL cholesterol < or = 100 mg/dL, HbA1c < or = 6.5%). Data recordings include serum creatinine values, eGFR, brain natriuretic peptide, patients' medical history and concomitant medication, clinical events, quality of life questionnaire (SF-12v2), 24 hour ambulatory blood pressure measurement, renal artery duplex ultrasound and echocardiography. Follow-up intervals are at 2, 6, 12 and 36 months following randomisation.The primary endpoint is the difference between treatments in change of eGFR over 12 months. Major secondary endpoints are technical success, change of renal function based on the eGFR slope change between pre-treatment and post-treatment (i.e. improvement, stabilisation, failure), clinical events overall such as renal or cardiac death, stroke, myocardial infarction, hospitalisation for congestive heart failure, progressive renal insufficiency (i.e. need for dialysis), need of target vessel revascularisation or target lesion revascularisation, change in average systolic and diastolic blood pressure, change in left ventricular mass index calculated from echocardiography, difference in the size of kidney (pole to pole length) measured by renal duplex sonography, total number, drug name, drug class, daily dose, regimen and Defined Daily Dose (DDD), of anti-hypertensive drugs, and change in New York Heart Association (NYHA) classification. Approximately 30 centres in Europe and South America will enrol patients. Duration of enrolment is expected to be 12 months resulting in study duration of 48 months.

TRIAL REGISTRATION

TRIAL REGISTRATION NUMBER

NCT00640406.

Silicon carbide coating of nitinol stents to increase antithrombogenic properties and reduce nickel release

BACKGROUND

The use of stents in the superficial femoral artery is still limited by the number of restenoses. Influencing factors include thrombus formation and smooth muscle cell proliferation as well as motion stress. A reduction of thrombogenicity can be achieved by passive coating with silicon carbide, which induces less thrombus formation due to its semiconducting properties.

METHODS AND MATERIALS

Self-expanding peripheral stents with and without silicon carbide coating were examined in a chandler loop model. Assessed parameters included thrombocyte count, beta-thromboglobulin (TG), thrombin-antithrombin (TAT) III complex, and polymorphonuclear elastase. Nickel release was quantified at Days 1, 3, and 223 using graphite furnace atomic absorption spectrometry. To visualize thrombus formation on the surface, scanning electron microscopy was conducted.

RESULTS

The tests showed a superiority of the coated stents regarding beta-TG (484.0+/-180.2 IU/l vs 2189.1+/-898.9 IU/l) as well as formation of TAT III complex (16.0+/-19.1 microg/l vs 458.3+/-761.0 microg/l). Scanning electron microscopy revealed a nearly absent thrombus formation on the coating. Nickel release was reduced by more than 90% at all time points.

CONCLUSIONS

In the provided in vitro setting, silicon carbide coating applied to self-expanding peripheral stents showed an advantage regarding thrombogenicity. The passive barrier resulted in a limited release of nickel from the alloy itself. These features seem promising for the use in the peripheral vasculature.

Balloon-expandable stenting with and without coiling for wide-neck and complex aneurysms

BACKGROUND

Wide-necked, saccular, dissecting, and fusiform intracranial aneurysms are poor coil retainers. Retention can be improved by parent-artery stenting across the aneurysm.

METHODS

We used a balloon-expandable stent and delivery system, intending to treat 38 aneurysms in 36 patients. Stents could not be advanced across the neck of 2 aneurysms near the ophthalmic artery origin. These cases were managed by temporary balloon remodeling and coiling. Stenting alone was done for 15 aneurysms, including 7 in vertebral artery V4 segments. Stenting with immediate or delayed coiling was done in 21 aneurysms.

RESULTS

Stenting alone caused immediate and complete obliteration of 1 treated aneurysm (7%), subtotal obliteration in 13 treated (86%) aneurysms, and was associated with 1 failure. Stenting and coiling yielded a significantly better 57% complete obliteration rate, 43% subtotal obliteration, and no failures. There were 5 complications: 1 wire perforation, 2 cavernous-carotid-sinus fistulae, and 2 partial in-stent thromboses. All were controlled or cleared with no long-term sequelae or deaths. Contrast imaging at 1 to 12 months was available for 30 patients (13 stent-only, 17 stent-plus-coiling), demonstrating complete obliteration in 25 (83%) and subtotal obliteration in 5. A total of 7 stent-only aneurysms (4 V4s) were completely obliterated, and 3 (all V4s) were > or = 90% obliterated.

CONCLUSION

Stenting and coiling through the wall of the stent resulted in 88% (15/17) complete obliteration when imaged 1 to 12 months after treatment. Stenting alone effectively closed off V4-segment wide-necked aneurysms but was inferior to stenting and coiling in less mobile vessels.

Role of stent design and coatings on restenosis and thrombosis

More than 15 years have passed since stent technology was introduced by Sigwart et al. [U. Sigwart, J. Puel, V. Mirkovitch, F. Joffe, et al. Intravascular stents to prevent occlusion and restenosis after transluminal angioplasty. N. Engl. J. Med. 316 (1987) 701-706.] among interventional cardiologists. Recently drug eluting stents have assumed dominance in the interventional world as positive trial results revealed their efficacy for preventing restenosis. Stent design, delivery-vehicle materials, and drug properties affect the function of these stents. Stainless steel stents with tubular and multicellular design have proven superior to coil or hybrid stent models. This chapter describes stents which have subtle influences of modular design, metal coverage, strut thickness, strut shape, surface smoothness, and coating materials like an alloy composition.

The paclitaxel-eluting Coroflex™ please stent pilot study (PECOPS I): Acute and 6-month clinical and angiographic follow-up

BACKGROUND AND OBJECTIVES

Various active stent coatings significantly reduce restenosis rates and target lesion revascularization compared to bare metal stents. Therefore, the procedural and 6-month performance of the new paclitaxel-eluting Coroflex. Please stent was investigated.

METHODS

Ninety-seven patients (66 +/- 7.6 years, 34/97(35.1%) diabetics, 11/97(11.3%) unstable angina) were enrolled per protocol for elective single stent deployment into native coronary de-novo or post-PTCA restenotic lesions (stenosis: >or= 70%, < 100%; reference diameter >or= 2.25 mm and <3.3 mm; lesion length <or= 16 mm) with 13/97(13.4%) lesion type A, 64/97(66%) type B1, 20/97(20.6%) type B2). The mean reference diameter was 2.88 +/- 0.42 mm, the lesion length 10.03 +/- 2.93 mm, and the minimal lumen diameter 0.64 +/- 0.22 mm.

RESULTS

The success rates of procedure and study stent deployment were 100% and 94.8%, respectively. In 5/97(5.2%) two stents were implanted. Follow-up was performed clinically in 86/87(98.9%) and angiographically in 77/87(88.5%) patients after 6.1 +/- 0.7 months. Major adverse cardiac events occurred in 7/87(8%) 1/87(1.2%) subacute thrombosis 10.3hrs post procedure, 1/87(1.2%) myocardial infarction, 5/87(5.7%) target lesion revascularizations. The in-segment stenosis declined from 78 +/- 7.2% to 9.4 +/- 6.2% after stenting increasing to 31.9 +/- 18.6% at follow-up. The in-segment late loss and the late loss index were 0.47 +/- 0.6 mm and 0.23 +/- 0.29 resulting in 6/77(7.8%) in-segment restenoses three each of which were located either within or beyond the stent structure. The outcome was neither influenced by the prevalence of diabetes ( p = 0.4), hypercholesterolemia ( p = 1), hypertension ( p = 1), overweight ( p = 1), nor by the family history of coronary artery disease ( p = 0.7).

CONCLUSION

The data of the paclitaxel-eluting Coroflex. Please stent tested in PECOPS I are within the range other available paclitaxel-eluting stent.