Examining the role of nickel and NiTi nanoparticles promoting inflammation and angiogenesis

Nickel titanium (NiTi, or Nitinol) alloy is used in several biomedical applications, including cardiac, peripheral vascular, and fallopian tube stents. There are significant biocompatibility issues of metallic implants to nickel ions and nano-/micro-sized alloy particles. Our laboratories have recently shown that microscale CoCr wear particles from metal-on-metal hips crosslink with the innate immune signaling Toll-like receptor 4 (TLR4), prompting downstream signaling that results in interleukin (IL)-1β and IL-8 gene expression. In vivo, NiTi alloy can also generate wear particles on the nanoscale (NP) that have thus far not been studied for their potential to induce inflammation and angiogenesis that can, in turn, contribute to implant (e.g. stent) failure. Earlier studies by others demonstrated that nickel could induce contact hypersensitivity by crosslinking the human, but not the mouse, TLR4. In the present work, it is demonstrated that NiCl₂ ions and NiTi nanoparticles induce pro-inflammatory and pro-angiogenic cytokine/chemokine expression in human endothelial and monocyte cell lines in vitro. These observations prompt concerns about potential mechanisms for stent failure. The data here showed a direct correlation between intracellular uptake of Ni²⁺ and generation of reactive oxygen species. To determine a role for nickel and NiTi nanoparticles in inducing angiogenesis in vivo, 1-cm silicone angioreactors were implanted subcutaneously into athymic (T-cell-deficient) nude mice. The angioreactors contained Matrigel (a gelatinous protein mixture that resembles extracellular matrix) in addition to one of the following: PBS (negative control), VEGF/FGF-2 (positive control), NiCl_2, or NiTi NP. The implantation of angioreactors represents a potential tool for quantification of angiogenic potentials of medical device-derived particles and ions in vivo. By this approach, NiTi NP were found to be markedly angiogenic, while Ni²⁺ was less-so. The angioreactors may provide a powerful tool to examine if debris shed from medical devices may promote untoward biological effects.

Mid-term Efficacy and Safety of Drug-coated Balloon versus Nitinol Bare Metal Stent for Primary Lesions in Femoropopliteal Artery Disease

OBJECTIVES

To compare drug-coated balloon (DCB) and bare metal stent (BMS) for primary lesions in femoropopliteal artery disease in Chinese population and to make subgroup analysis between the groups.

METHODS

Patients with primary lesions who underwent BMS or DCB treatment of a single tertiary vascular center were included and followed up for 24 months. Clinical and anatomic status were reported using the criteria recommended by the Society for Vascular Surgery. The primary endpoint included primary patency, clinically target limb revascularization, composite safety endpoint and all-cause death over 24 months assessed by Kaplan-Meier. Secondary endpoints included technical success rate and stent-related complications.

RESULTS

A total of 284 patients with 324 limbs were pooled into analysis and most of the baseline characteristics did not show significant difference. A total of 74 in BMS group and 71 in DCB group were claudicants while 83 in BMS group and 56 in DCB group suffered from chronic limb threatening ischemia (CLTI). The mean cumulative lesion length was 18.7 ± 9.8cm in BMS group while 17.2 ± 10.3cm in DCB group. Kaplan-Meier estimates of primary patency were 75.3% and 80.9% for BMS and DCB groups at 12 months while decreased to 63.9% and 70.2% at 24 months (log-rank P = 0.167), respectively. Freedom from clinically driven target limb revascularization was 86.8% and 92.7% for BMS and DCB groups at 12 months while dropped to 82.5% and 85.9% at 24 months (log-rank P = 0.342). Estimates of primary patency between BMS and DCB group did not show significant difference on lesions with poor runoff (58.8% vs. 67.3%, log-rank P = 0.127), severe calcification (64.5% vs. 69.4%, log-rank P = 0.525) and popliteal artery involvement (59.3% vs. 60.3%, log-rank P = 0.695) at 24 months. The overall survival (92.6% for BMS, 90.3% for DCB, log-rank P = 0.391) and freedom from composite safety endpoint (79.3% for BMS, 79.2% for DCB, log-rank P = 0.941) showed no significant difference at 24 months.

CONCLUSIONS

Over the 24 month follow-up, BMS and DCB showed equivalent efficacy and safety outcomes for primary femoropopliteal artery disease, which indicated the reduction of permanent metallic implant insertion might be possible.

Implantation of vascular mimetic implants in challenging chronic total occlusions - SuperaTM Extreme

Standard nitinol stents (SNS), with or without drug eluting technology, are an essential tool within the interventional armamentarium in the treatment of patients with peripheral arterial disease. However, they are plagued by a number of limitations: a.) stent fractures, although observed predominately in first-generation stents, do still occur in state-of-the art stent platforms, b.) lack of radial strength, resulting in inadequate stent expansion, c.) kinking up to a complete collapse of the stent, therefore compromising its use in areas of high mechanical stress such as bending zones. In contrast, the interwoven design of the Supera^TM stent, also referred to as "vascular mimetic implant", overcomes all of the above limitations of SNS. Several registries and studies not only confirmed its mechanical superiority (lack of stent fractures etc.) but also demonstrated remarkable clinical performance (patency and freedom from target lesion revascularization), despite its use in challenging lesions (calcification etc.) and territories (popliteal arteries etc.). Increasing confidence in the mechanical properties of the Supera^TM stent platform prompted interventionalists to further "push the limits" of this unique implant. The present article summarizes the clinical data and shows examples of "extreme" applications of this dedicated stent platform.

Biomechanical interpretation of observed fatigue fractures of peripheral Nitinol stents in the superficial femoral arteries through in silico modelling

PURPOSE

To suggest an in silico modelling approach to estimate the fatigue failure on peripheral Nitinol stents implanted in the superficial femoral artery (SFA) and interpret the clinically observed stent fractures of a retrospective series of patients.

MATERIALS AND METHODS

Preoperative data of 27 patients who underwent SFA Nitinol stenting were retrospectively analyzed. Data about preoperative features of the SFA and the lesion were collected. Follow-up data were also collected about the occurrence of restenosis/occlusion and stent fracture.

RESULTS

After a lengthening of the entire vessel, the occluded region was slightly stretched due to its high stiffness, whereas the healthy regions accommodated the artery length variation. The stent fatigue was predicted to be higher in the regions of low stiffness and higher shortening. In 7 out of 27 patients a stent fracture was clinically recorded. The model resulted to be accurate in 90% of the cases.

CONCLUSIONS

The clinical outcomes in terms of biomechanical fatigue behavior of peripheral Nitinol stents of the SFA could be interpreted by our new approach.

Real-world experience with a Paclitaxel-Coated Balloon for the treatment of atherosclerotic infrainguinal arteries: 12-month interim results of the BIOLUX P-III registry first year of enrolment

Background

Endovascular management of atherosclerotic infrainguinal arteries recently shifted towards drug eluting devices, designed to locally prevent the restenosis process. Numerous clinical studies report an advantage of drug coated balloons over uncoated balloon angioplasty in treating lower extremity peripheral artery disease. However, as coating and balloon platforms are different, each device requires dedicated clinical evaluations.

Objective

The aim of the study is to further investigate the safety and effectiveness of a Paclitaxel-Coated Balloon for the treatment of atherosclerotic infrainguinal arteries in a real-world setting.

Methods

203 patients out of a final sample of 882 were enrolled in this prospective multicenter, observational, all-comers registry during the first 12 months. The primary endpoints were major adverse events (defined as procedure or device related death within 30 days post index procedure, clinically-driven target lesion revascularization or major target limb amputation) at 6 months and freedom from clinically-driven target lesion revascularization at 12 months. Both endpoints were adjudicated by a Clinical Events Committee.

Results

Mean patient age was 70.2±10.4 years (60.1% male). 47.3% of the patients were diabetic and 67.5% had a history of smoking. Severe claudication was reported in 37.4% and 40% had critical limb ischemia. 257 lesions, including 13.2% in the infrapopliteal territory, were treated with Passeo-18 Lux (mean lesion length 75.1 mm±69.4, 20% occlusions, 76.3% calcified). At 6 months, the rate of major adverse events was 5.5% (95%CI 3.1-9.7). Freedom from clinically-driven target lesion revascularization at 12 months was 93.2% (95%CI 89.1-95.8). All causes mortality was 6.5% (95%CI 3.8-11.0) and overall amputation rate was 4.2% (95%CI 2.1-8.3) at 12 months.

Conclusion

In a real-world environment, the BIOLUX P-III registry preliminary results confirm the safety and efficacy of the Paclitaxel-Coated Passeo-18 Lux balloon as a stand-alone treatment option for atherosclerotic infrainguinal arteries.

A network meta-analysis of randomized controlled trials comparing treatment modalities for de novo superficial femoral artery occlusive lesions

BACKGROUND

Treatment of superficial femoral artery (SFA) lesions remains challenging. We conducted a network meta-analysis of randomized controlled trials aiming to explore the efficacy of treatment modalities for SFA "de novo" lesions.

METHODS

Eleven treatments for SFA occlusive disease were recognized. We used primary patency and binary restenosis at 12-month follow-up as proxies of efficacy for the treatment of SFA lesions.

RESULTS

A total of 33 studies (66 study arms; 4659 patients) were deemed eligible. In terms of primary patency, odds ratios (ORs) with 95% confidence intervals (CIs) were statistically significantly higher in drug-eluting stent (DES; OR, 10.05; 95% CI, 3.22-31.39), femoropopliteal bypass surgery (BPS; OR, 7.15; 95% CI, 2.27-22.51), covered stent (CS; OR, 3.56; 95% CI, 1.33-9.53), and nitinol stent (NS; OR, 2.83; 95% CI, 1.42-5.51) compared with balloon angioplasty (BA). The rank order from higher to lower primary patency in the multidimensional scaling was DES, BPS, NS, CS, drug-coated balloon, percutaneous transluminal angioplasty with brachytherapy, stainless steel stent, cryoplasty (CR), and BA. Combination therapy of NS with CR and drug-coated balloon were the two most effective treatments, followed by NS, CS, percutaneous transluminal angioplasty with brachytherapy, cutting balloon, stainless steel stent, BA, and CR in terms of multidimensional scaling values for binary restenosis.

CONCLUSIONS

DES has shown encouraging results in terms of primary patency for SFA lesions, whereas BPS still maintains its role as a principal intervention. On the contrary, BA and CR appear to be less effective treatment options.

Incidence and Predictors of In-stent Re-Stenosis in the Superficial Femoral Artery: Evaluation of Long-Term Outcomes by Color Duplex Ultrasound

This study aimed to investigate the incidence and predictors of in-stent re-stenosis (ISR) for nitinol stents in the superficial femoral artery (SFA) by color duplex ultrasound (CDU). In total, 235 patients undergoing SFA stenting were included in the present study. The cumulative ISR rates at 3, 6, 12, 24 and 36 mo post-procedure were 5.4%, 24.0%, 49.0%, 61.5% and 71.5%, respectively. The markedly low peak systolic velocity of the popliteal artery (PSV2) post-operation was inversely correlated with the ISR. The threshold for ≥50% re-stenosis was PSV2 ≤ 63 cm/s with 86.6% sensitivity and 90.5% specificity. With regard to re-occlusion, the PSV2 was ≤40 cm/s with 98.1% sensitivity and 93.4% specificity. Cox regression analysis indicated that the cumulative stent length, diabetes, and pre-stent stenosis level were independent risk factors of ISR. In conclusion, the ISR incidence after SFA stenting is relatively high and CDU follow-up is a feasible method for evaluating ISR.

Fatigue of Metallic Stents: From Clinical Evidence to Computational Analysis

The great success of stents in treating cardiovascular disease is actually undermined by their long-term fatigue failure. The high variability of stent failure incidence suggests that it is due to several correlated aspects, such as loading conditions, material properties, component design, surgical procedure, and patient functional anatomy. Numerical and experimental non-clinical assessments are included in the recommendations and requirements of several regulatory bodies and they are thus exploited in the analysis of stent fatigue performance. Optimization-based simulation methodologies have been developed as well, to improve the fatigue endurance of novel designs. This paper presents a review on the fatigue issue in metallic stents, starting from a description of clinical evidence about stent fracture up to the analysis of computational approaches available from the literature. The reported discussion on both the experimental and numerical framework aims at providing a general insight into stent lifetime prediction as well as at understanding the factors which affect stent fatigue performance for the design of novel components.