Helical Centerline Stent Improves Patency: Two-Year Results From the Randomized Mimics Trial

The BioMimics 3D Helical Centreline Nitinol Stent in Chronic Limb Threatening Ischaemia and Complex Lesions: Three Year Outcomes of the MIMICS-3D Registry

OBJECTIVE

There is a need for improved outcomes in the endovascular treatment of patients suffering from chronic limb threatening ischaemia (CLTI), highly calcified lesions, and chronic total occlusions (CTOs). The helical centreline self expanding BioMimics 3D stent might be particularly useful in these high risk subsets, combining flexibility and fracture resistance with radial strength. Herein, the performance of the BioMimics 3D stent was assessed in these high risk subsets.

METHODS

MIMICS-3D is a prospective, multicentre, European real world registry. This was a post hoc analysis, comparing patients with CLTI vs. intermittent claudication (IC), lesions with bilateral calcification vs. those without (peripheral arterial calcium scoring system [PACSS] 3,4 vs. PACSS 0 - 2), and CTO vs. no CTO. Propensity score matching was performed to reduce the impact of baseline variables. The 36 month endpoints were clinically driven target lesion revascularisation (CD-TLR), death, major target limb amputation, and stent patency.

RESULTS

A total of 507 patients were enrolled. At 36 months, patients with CLTI had lower freedom from major amputation than patients with IC (92.6% vs. 100%, p < .001). In terms of primary patency, patients with CTO had lower patency rates than those without (63.9% vs. 77.8%, p = .003), but the difference reduced after propensity score matching (70.5% vs. 76.8%, p = .43). Primary patency was not impaired for patients with PACSS 3,4 or patients with CLTI. Freedom from CD-TLR was not significantly different among the groups and was 73.8% for CLTI vs. 78.9% for IC (p = .15), 77.6% for PACSS 3,4 vs. 78.7% for PACSS 0 - 2 (p = .55), and 75.6% for CTO vs. 81.0% for no CTO (p = .11).

CONCLUSIONS

The outcome of the MIMICS-3D registry suggests that the BioMimics 3D stent is effective in the endovascular treatment of complex femoropopliteal lesions and in CLTI. Future randomised controlled trials should confirm its non-inferiority or superiority compared with existing alternatives.

Biomimetic Stents for Infrainguinal Peripheral Arterial Disease: Systematic Review and Meta-Analysis

OBJECTIVE

Biomimetic stents are peripheral infrainguinal self expanding stents that mimic the anatomy of the vasculature and artery movement. They are indicated for use in infrainguinal arteries. This research aimed to synthesise all current evidence on the use of biomimetic stents as adjuncts for endovascular treatment of infrainguinal peripheral arterial disease (PAD), helping to guide clinical decision making.

DATA SOURCES

MEDLINE, Embase, CINAHL and Cochrane databases.

REVIEW METHODS

Random effects meta-analysis following PRISMA guidelines (PROSPERO registration CRD42022385256). Study quality was assessed using the Joanna Briggs Institute critical appraisal tools checklist, and certainty assessment through the Grading of Recommendations, Assessment, Development and Evaluation (GRADE). Endpoints included primary patency, target lesion revascularisation, stent fracture, secondary patency, and Death at one year.

RESULTS

In total, 37 studies were included in the meta-analysis (33 cohort studies, two case series, and two randomised controlled trials [RCTs]), representing 4 480 participants. Of these, 34 studies included data on the Supera (81.5% of participants) and three studies reported data on the BioMimics 3D (18.5% of participants) stents. The pooled primary patency rate of 33 studies at one year follow up was 81.4% (95% confidence interval [CI] 78.7 - 83.9%), and the pooled target lesion revascularisation rate of 18 studies at one year was 12.2% (95% CI 9.6 - 15.0%). The certainty of evidence outcome rating as qualified by GRADE was very low for both. Only one study reported a positive stent fracture rate at one year follow up of 0.4% with a certainty of evidence outcome of low.

CONCLUSION

Using biomimetic stents for infrainguinal PAD may be associated with acceptable one year primary patency and target lesion revascularisation rates, with a near negligible one year stent fracture rate. Their use should be considered in those presenting with infrainguinal PAD undergoing endovascular revascularisation. A RCT is necessary to determine their clinical and cost effectiveness.

Effects of helical centerline stent vs. straight stent placement on blood flow velocity

As an approach to maintain patency in femoropopliteal stenting, a helical stent configuration was proposed, which showed improved patency in clinical trials. However, the effects of helical stent placement on the flow have not been quantitatively analyzed. The purpose of this study was to estimate flow velocities to quantify the influence of helical stent placement. Helical and straight stents were implanted in three healthy pigs, and the flow velocities were estimated using the time-intensity curve (TIC) in the angiography images. The angiographic images indicated thinning of the leading edge of the contrast medium through the helically deformed artery, which was not observed in the straight stent. The slower rise of the TIC peak in the helical stent indicated faster travel of this thinner edge. Arterial expansion due to stenting was observed in all cases, and the expansion rate varied according to location. All cases of helical stent implantation showed that velocity was maintained (55.0%-71.3% velocity retention), unlike for straight stent implantation (43.0%-68.0% velocity retention); however, no significant difference was observed.

BioMimics 3D Stent in Femoropopliteal Lesions: 3-Year Outcomes with Propensity Matching for Drug-Coated Balloons

Background: Through its helical centreline geometry, the BioMimics 3D vascular stent system is designed for the mobile femoropopliteal region, aiming to improve long-term patency and the risk of stent fractures. Methods: MIMICS 3D is a prospective, European, multi-centre, observational registry to evaluate the BioMimics 3D stent in a real-world population through 3 years. A propensity-matched comparison was performed to investigate the effect of the additional use of drug-coated balloons (DCB). Results: The MIMICS 3D registry enrolled 507 patients (518 lesion, length 125.9 ± 91.0 mm). At 3 years, the overall survival was 85.2%, freedom from major amputation 98.5%, freedom from clinically driven target lesion revascularisation 78.0%, and primary patency 70.2%. The propensity-matched cohort included 195 patients in each cohort. At 3-year follow-up, there was no statistically significant difference in clinical outcomes, such as overall survival (87.9% in the DCB vs. 85.1% in the no DCB group), freedom from major amputation (99.4% vs. 97.2%), clinically driven TLR (76.4% vs. 80.3%), and primary patency (68.5% vs. 74.4%). Conclusion: The MIMICS 3D registry showed good 3-year outcomes of the BioMimics 3D stent in femoropopliteal lesions, demonstrating the safety and performance of this device under real-world conditions, whether used alone or in combination with a DCB.

State-of-the-Art Endovascular Therapies for the Femoropopliteal Segment: Are We There Yet?

Peripheral arterial disease is an increasingly prevalent condition with significant associated morbidity, mortality, and health care expenditure. Endovascular interventions are appropriate for most patients with either ongoing symptoms of intermittent claudication despite lifestyle and medical optimization or chronic limb-threatening ischemia. The femoropopliteal segment is the most common arterial culprit responsible for claudication and the most commonly revascularized segment. Endovascular approaches to revascularization of the femoropopliteal segment are advancing with an evolving landscape of techniques for arterial access, device-based therapies, vessel preparation, and intraprocedural imaging. These advances have been marked by debate and controversy, notably related to the safety of paclitaxel-based devices and necessity of atherectomy. In this review, we provide a critical overview of the current evidence, practice patterns, emerging evidence, and technological advances for endovascular intervention of the femoropopliteal arterial segment.

Stents With Torsional Strength for Superficial Femoral Artery Disease: The Prospective Q3-Registry

PURPOSE

This postmarketing surveillance study aimed to assess effectiveness and safety of a peripheral self-expanding stent with high torsional strength (POLARIS stent) for the treatment of de novo superficial femoral artery (SFA) lesions in the routine clinical practice.

MATERIALS AND METHODS

Consecutive patients with symptomatic de novo SFA occlusive disease who underwent POLARIS stent implantation were enrolled into the prospective, multicenter, observational postmarket surveillance study. Primary outcome measure was freedom from clinically driven target lesion revascularization (cdTLR) at 12 months. Main secondary outcomes were procedural success, primary clinical improvement, and freedom from major adverse cardiovascular and limb events (MACLE) throughout 24 months.

RESULTS

A total of 199 participants (70±11 years, 70.4% men) were included in the study at 9 German sites from December 2014 to August 2018. Half of them (52.6%) were current smokers, 37.6% had diabetes, and 25.0% were obese. Most participants suffered from intermittent claudication (88.4%). Mean lesion length was 98±83 mm, 43.5% of lesions were occluded, and 27.3% were severely calcified. Freedom from 12 months cdTLR was 94.4% (95% confidence interval [CI], 90.6-98.2). At 24 months, freedom from cdTLR was 88.7% (95% CI, 83.0-94.4). Procedural success was achieved in 96.2% of participants. Primary clinical improvement occurred in 87.5% and 85.4% of participants at 12 and 24 months, respectively. Freedom from MACLE was 94.8% (95% CI, 91.4-98.1) and 93.8% (95% CI, 89.9-97.6) at 12 and 24 months, respectively.

CONCLUSIONS

Treatment of SFA occlusive disease in a real-world setting using the POLARIS stent with high bidirectional torsional strength is efficacious and does not raise any safety concern in the medium term. The study is registered with ClinicalTrials.gov (Identifier: NCT02307292).

BioMimics 3D vascular stent system for femoropopliteal interventions

Background: The MIMICS-3D study aimed to assess the safety and effectiveness of the BioMimics 3D Vascular Stent System for the treatment of symptomatic femoropopliteal artery disease in a real-world patient population. Patients and methods: Consecutive participants who were scheduled for implantation of the BioMimics 3D stent were enrolled in the prospective, observational, multicenter study. The primary effectiveness outcome was freedom from clinically driven target lesion revascularization at 12 months and the primary safety outcome was a composite of major adverse events comprising death, major target limb amputation, or clinically driven target lesion revascularization at 30 days. Outcomes through 24 months are reported. Results: A total of 507 patients (70±10 years, 65.5% male sex) were enrolled and treated with the study stent. 24.0% had critical limb-threatening ischemia, lesion length was 127±92 mm, and 56.8% of lesions were totally occluded. The Kaplan-Meier (KM) estimate of freedom from clinically driven target lesion revascularization at twelve-months was 90.6% (95% CI: 87.9%-93.3%) and the 30-day primary safety outcome occurred in 1.2% (95% CI: 0.5%-2.7%) of participants. At 24 months, clinical improvement was achieved in 86.6% and the KM estimate of freedom from clinically driven target lesion revascularization was 82.8% (95% CI: 79.4%-86.4%). The KM estimate of freedom from loss of primary patency according to PSVR >2.4 was 78.6% (95% CI: 74.7%-82.4%). Survival distribution functions regarding primary patency were lower with long lesions (>150 mm; log-rank p<0.001) but did not differ significantly between participants with or without critical limb-threatening ischemia (log-rank p=0.07). Conclusions: Endovascular treatment of atherosclerotic femoropopliteal lesions with the BioMimics 3D Vascular Stent System is efficacious and safe in a real-world setting.

Treatment of Femoropopliteal Lesions With the BioMimics 3D Vascular Stent System: Two-Year Results From the MIMICS-2 Trial

PURPOSE

To report the safety and effectiveness outcomes through 2 years of the BioMimics 3D Vascular Stent System in the treatment of symptomatic patients with atherosclerotic femoropopliteal disease.

MATERIALS AND METHODS

The tubular, nitinol BioMimics 3D stent, which was designed to impart a helical shape to the arterial segment, was implanted in 271 patients (mean age 68.4±9.5 years; 180 men) with de novo femoropopliteal lesions enrolled at 43 investigational sites [31 US (n=162), 6 German (n=78), and 6 Japanese (n=31)] in the prospective, single-arm MIMICS-2 investigational device exemption trial (ClinicalTrials.gov identifier NCT02400905) between June 2015 and October 2016. Mean lesion length was 81.2±38.4 mm, 30.0% of patients had total occlusions, and 45.9% had moderate to severe calcification. Primary safety and effectiveness endpoints were compared at 1 year with prespecified objective performance goals (OPGs) set by the VIVA Physicians organization. Outcomes through 2 years are reported.

RESULTS

The primary effectiveness endpoint of 12-month primary stent patency was met by 182 of 249 patients (73.1%, 95% CI 67.3% to 78.2%), exceeding the OPG of 66%. The primary safety endpoint of 30-day freedom from major adverse events (MAEs) was met in 268 of 269 patients (99.6%, 95% CI 97.7% to 100%), exceeding the OPG of 88%. Kaplan-Meier estimates of freedom from loss of primary patency were 83.1% at 12 months and 70.2% at 24 months, freedom from MAEs estimates were 86.9% at 12 months and 79.2% at 24 months, and freedom from clinically-driven target lesion revascularization estimates were 88.0% at 12 months and 83.0% at 24 months. At 24 months, 88.2% of patients showed improvement of ≥1 Rutherford category; the ankle-brachial index was >0.9 for 64.4% vs 11.3% at baseline. There were no cases of stent fracture.

CONCLUSION

Through 24 months, the BioMimics 3D Vascular Stent System provided safe and effective treatment for femoropopliteal lesions in patients with symptomatic peripheral artery disease.

Analyses of hemodialysis arteriovenous fistula geometric configuration and its associations with maturation and reintervention

OBJECTIVE

An arteriovenous fistula (AVF) is the preferred vascular access for chronic hemodialysis; however, the rates of AVF maturation failure and reintervention remain high. We investigated the AVF geometric parameters and their associations with AVF physiologic maturation and reintervention in a prospective multicenter study.

METHODS

From 2011 to 2016, patients undergoing vein end-to-artery side upper extremity AVF creation surgery were recruited. Contrast-free dark blood and phase-contrast magnetic resonance imaging (MRI) scans were performed using 3.0T scanners to obtain the AVF lumen geometry and flow rates, respectively, at postoperative day 1, week 6, and month 6. The arteriovenous anastomosis angle, nonplanarity, and tortuosity of the fistula were calculated according to the lumen centerlines. AVFs were considered physiologically matured if, using the week 6 MRI data, the flow rate was ≥500 mL/min and the minimum vein lumen diameter was ≥5 mm. The associations of these geometric parameters with AVF maturation and reintervention due to perianastomotic and mid-vein stenosis within 1 year were assessed.

RESULTS

A total of 111 patients had a usable day 1 MRI scan, with most having upper arm AVFs (n = 73). Compared with the forearm AVFs, upper arm AVFs had greater anastomosis angles (P < .001), larger deviations from a plane (nonplanarity; P = .002), and more prominent tortuosity (P = .038) at day 1. These parameters significantly increased between day 1 and week 6 in upper arm AVFs. In contrast, significant changes in these parameters in forearm AVFs were not observed. The rate of maturation was 54% and 86% for forearm and upper arm AVFs, respectively. None of the geometric parameters at day 1 were associated with AVF maturation in either location. The rate of reintervention was 24% and 30% for forearm and upper arm AVFs, respectively, with a larger nonplanarity angle at day 1 associated with less reintervention (30° ± 15° vs 21° ± 10°; P = .034) in upper arm AVFs only. This relationship was unchanged after adjusting for age, sex, race, dialysis status, or diabetes.

CONCLUSIONS

In our study, upper arm fistulas had a larger anastomosis angle, were more nonplanar, and had more tortuous veins than forearm fistulas. For upper arm fistulas, a larger nonplanarity angle is associated with a lower rate of reintervention within 1 year. Once confirmed, vascular surgeons could consider increasing the nonplanarity angle by incorporating a tension-free gentle curvature in the proximal segment of the mobilized vein to reduce reinterventions when creating an upper arm fistula.

The role of oxygen transport in atherosclerosis and vascular disease

Atherosclerosis and vascular disease of larger arteries are often associated with hypoxia within the layers of the vascular wall. In this review, we begin with a brief overview of the molecular changes in vascular cells associated with hypoxia and then emphasize the transport mechanisms that bring oxygen to cells within the vascular wall. We focus on fluid mechanical factors that control oxygen transport from lumenal blood flow to the intima and inner media layers of the artery, and solid mechanical factors that influence oxygen transport to the adventitia and outer media via the wall's microvascular system-the vasa vasorum (VV). Many cardiovascular risk factors are associated with VV compression that reduces VV perfusion and oxygenation. Dysfunctional VV neovascularization in response to hypoxia contributes to plaque inflammation and growth. Disturbed blood flow in vascular bifurcations and curvatures leads to reduced oxygen transport from blood to the inner layers of the wall and contributes to the development of atherosclerotic plaques in these regions. Recent studies have shown that hypoxia-inducible factor-1α (HIF-1α), a critical transcription factor associated with hypoxia, is also activated in disturbed flow by a mechanism that is independent of hypoxia. A final section of the review emphasizes hypoxia in vascular stenting that is used to enlarge vessels occluded by plaques. Stenting can compress the VV leading to hypoxia and associated intimal hyperplasia. To enhance oxygen transport during stenting, new stent designs with helical centrelines have been developed to increase blood phase oxygen transport rates and reduce intimal hyperplasia. Further study of the mechanisms controlling hypoxia in the artery wall may contribute to the development of therapeutic strategies for vascular diseases.

Effectiveness of the Pulsar-18 self-expanding stent with optional drug-coated balloon angioplasty in the treatment of femoropopliteal lesions – the BIOFLEX PEACE All-Comers Registry

Summary. Background: Previous studies showed favorable results after treatment of femoropopliteal lesions with the Pulsar-18 self-expanding (SE) nitinol stent. The objective of this registry was to evaluate whether these results will be confirmed in a real-world setting with varying stenting strategies. Patients and methods: In this prospective, observational trial, 160 patients with 186 femoropopliteal lesions were treated with the Pulsar-18 SE nitinol stent at 9 German sites. Mean lesion length was 116 ± 103 mm, and 41.9 % of the lesions were moderately or heavily calcified. Eighty lesions were concomitantly treated with drug-coated balloon (DCB). Main effectiveness outcome was primary patency at 12 months, and main safety outcome was freedom from the composite of device or procedure related death, major target limb amputation, and clinically driven target lesion revascularization (TLR) at 30 days and 6 months. Results: Kaplan-Meier estimate of primary patency was 89.1 %, 67.3 %, and 57.1 % at 6, 12, and 24 months. Freedom from TLR was 95.5 %, 91.4 %, and 85.2 % at 6, 12, and 24 months, respectively. Lesions, which were additionally treated with DCB (plus DCB-group), were longer (150 versus 82 mm on average, p < 0.0001), and associated with lower primary patency estimates than those without DCB angioplasty (stent-only-group) (log-rank p = 0.006). However, there was no difference in freedom from TLR between groups (log-rank p = 0.542). Improvement by ≥ 1 Rutherford category was achieved in 84.8 %, 81.0 %, and 81.7 % of patients at 6, 12, and 24 months, respectively. Walking distance and patient-reported pain improved persistently through 24 months (p < 0.001). Hemodynamic improvement was achieved in 68.2 %, 73.7 %, and 70.7 % of the patients at 6, 12, and 24 months, respectively. Conclusions: The Pulsar-18 self-expanding nitinol stent with optional drug-coated balloon angioplasty can be considered an efficacious and safe therapy option for endovascular treatment of femoropopliteal artery disease.

Biomechanical Forces and Atherosclerosis: From Mechanism to Diagnosis and Treatment

The article provides an overview of current views on the role of biomechanical forces in the pathogenesis of atherosclerosis. The importance of biomechanical forces in maintaining vascular homeostasis is considered. We provide descriptions of mechanosensing and mechanotransduction. The roles of wall shear stress and circumferential wall stress in the initiation, progression and destabilization of atherosclerotic plaque are described. The data on the possibilities of assessing biomechanical factors in clinical practice and the clinical significance of this approach are presented. The article concludes with a discussion on current therapeutic approaches based on the modulation of biomechanical forces.

Prospective Evaluation of the TIGRIS Vascular Stent Within a Modern Treatment Algorithm

Purpose: To prospectively evaluate the safety and efficacy of the TIGRIS Vascular Stent in the superficial femoral artery (SFA) and proximal popliteal artery within a treatment algorithm that reserved stent usage for more challenging patients. Materials and Methods: This prospective, single-center study enrolled 97 patients (mean age 68.7 years; 66 men) who were treated for 100 de novo or nonstented restenotic femoropopliteal lesions (≥70% stenosis) and had recoil or dissection after plain balloon predilation. The average lesion length was 5.6±2.3 cm (maximum 8 cm per protocol). The composite primary efficacy outcome was 12-month primary patency, defined as a peak systolic velocity ratio ≤2.5 at the stented target lesion on duplex ultrasound, and no clinically-driven reintervention within the stented segment. The primary safety outcome was freedom from device- and procedure-related target vessel revascularization, target limb major amputation (above the metatarsals), or death through 30 days. Secondary outcomes included secondary patency, clinically-driven target lesion revascularization (TLR), Rutherford category change relative to baseline, and binary restenosis of the target lesion. Results: All devices were successfully implanted with no device-related complications at the time of implant or within the 30-day postimplant window. The average stented length was 7.0±2.5 cm; no stent elongation was observed during deployment. One patient was lost to follow-up before 12 months and another died of an unrelated cause, leaving 95 patients (98 lesions) available for 12-month follow-up and 77 patients/lesions for the 24-month preliminary analysis. The binary primary and secondary patency rates at 12 months were 92.9% and 100%. The binary freedom from TLR was 94.9%. At 24 months, the Kaplan-Meier estimate of primary patency was 90.0%. Conclusion: This prospective study demonstrated that the TIGRIS Vascular Stent is a safe and effective device in a modern treatment algorithm that reserved bare stent use for postangioplasty dissection or recoil in distal femoropopliteal arteries.

Drug-coated balloons versus drug-eluting stents in the femoropopliteal artery: comparing apples to oranges?

Superficial femoral and popliteal artery disease are commonly involved in the development of symptomatic PAD. As time has gone on drug coated stents and drug coated balloons have supplanted the plain balloon angioplasty corner stone of therapy with superiority proven in randomized trials. Device approval trials are typically characterized by simple lesions that are less common than the longer complex disease. Registry data has demonstrated benefit of both technologies though drug coated balloons typically require a significant amount of adjunctive stenting in more complex disease. Recently published randomized data is starting to help proceduralists define when each therapy may be more optimal.

Efficiently Generating Mixing by Combining Differing Small Amplitude Helical Geometries

Helical geometries have been used in recent years to form cardiovascular prostheses such as stents and shunts. The helical geometry has been found to induce swirling flow, promoting in-plane mixing. This is hypothesised to reduce the formation of thrombosis and neo-intimal hyperplasia, in turn improving device patency and reducing re-implantation rates. In this paper we investigate whether joining together two helical geometries, of differing helical radii, in a repeating sequence, can produce significant gains in mixing effectiveness, by embodying a ‘streamline crossing’ flow environment. Since the computational cost of calculating particle trajectories over extended domains is high, in this work we devised a procedure for efficiently exploring the large parameter space of possible geometry combinations. Velocity fields for the single geometries were first obtained using the spectral/hp element method. These were then discontinuously concatenated, in series, for the particle tracking based mixing analysis of the combined geometry. Full computations of the most promising combined geometries were then performed. Mixing efficiency was evaluated quantitatively using Poincaré sections, particle residence time data, and information entropy. Excellent agreement was found between the idealised (concatenated flow field) and the full simulations of mixing performance, revealing that a strict discontinuity between velocity fields is not required for mixing enhancement, via streamline crossing, to occur. Optimal mixing was found to occur for the combination R = 0.2 D and R = 0.5 D , producing a 70 % increase in mixing, compared with standard single helical designs. The findings of this work point to the benefits of swirl disruption and suggest concatenation as an efficient means to determine optimal configurations of repeating geometries for future designs of vascular prostheses.

Heterogeneity in the nonplanarity and arterial curvature of arteriovenous fistulas in vivo

OBJECTIVE

Native arteriovenous fistulas (AVFs) for hemodialysis are susceptible to nonmaturation. Adverse features of local blood flow have been implicated in the formation of perianastomotic neointimal hyperplasia that may underpin nonmaturation. Whereas computational fluid dynamic simulations of idealized models highlight the importance of geometry on fluid and vessel wall interactions, little is known in vivo about AVF geometry and its role in adverse clinical outcomes. This study set out to examine the three-dimensional geometry of native AVFs and the geometric correlates of AVF failure.

METHODS

As part of an observational study between 2013 and 2016, patients underwent creation of an upper limb AVF according to current surgical best practice. Phase-contrast magnetic resonance imaging was performed on the day of surgery to obtain luminal geometry along with ultrasound measurements of flow. Magnetic resonance imaging data sets were segmented and reconstructed for quantitative and qualitative analysis of local geometry. Clinical maturation was evaluated at 6 weeks.

RESULTS

There were 60 patients who were successfully imaged on the day of surgery. Radiocephalic (n = 17), brachiocephalic (n = 40), and brachiobasilic (n = 3) fistulas were included in the study. Centerlines extracted from segmented vessel lumen exhibited significant heterogeneity in arterial nonplanarity and curvature. Furthermore, these features are more marked in brachiocephalic than in radiocephalic fistulas. Across the cohort, the projected bifurcation angle was 73 ± 16 degrees (mean ± standard deviation). Geometry was preserved at 2 weeks in 20 patients who underwent repeated imaging. A greater degree of arterial nonplanarity (log odds ratio [logOR], 0.95 per 0.1/vessel diameter; 95% confidence interval [CI], 0.22-1.90; P = .03) and a larger bifurcation angle (logOR, 0.05 per degree; 95% CI, 0.01-0.09; P = .02) are associated with a greater rate of maturation, as is fistula location (upper vs lower arm; logOR, -1.9; 95% CI, -3.2 to 0.7; P = .002).

CONCLUSIONS

There is significant heterogeneity in the three-dimensional geometry of AVFs, in particular, arterial nonplanarity and curvature. In this largest cohort of AVF geometry to date, the effect of individual geometric correlates on maturation is uncertain but supports the premise that future modeling studies will need to acknowledge the complex geometry of AVFs.

Swirling Flow and Wall Shear: Evaluating the BioMimics 3D Helical Centerline Stent for the Femoropopliteal Segment

The BioMimics 3D self-expanding nitinol stent represents a strategy for femoropopliteal intervention that is alternative or complementary to deployment of drug-coated stents or balloons. Whereas conventional straight stents reduce arterial curvature and disturb blood flow, creating areas of low wall shear, where neointimal hyperplasia predominantly develops, the helical centerline geometry of the BioMimics 3D maintains or imparts arterial curvature, promotes laminar swirling blood flow, and elevates wall shear to protect against atherosclerosis and restenosis. In the multicenter randomized MIMICS trial, treatment of femoropopliteal disease with the BioMimics 3D (n = 50) significantly improved 2-year primary patency (log-rank test p = 0.05) versus a control straight stent (n = 26), with no cases of clinically driven target lesion revascularization between 12 and 24 months (log-rank test p = 0.03 versus controls). In geometric X-ray analysis, the BioMimics stent was significantly more effective in imparting a helical shape even when the arterial segment was moderately to severely calcified. Computational fluid dynamics analysis showed that average wall shear was significantly higher with the helical centerline stent (1.13 ± 0.13 Pa versus 1.06 ± 0.12 Pa, p = 0.05). A 271-patient multicenter international MIMICS-2 trial and a 500-patient real-world MIMICS-3D registry are underway.

Novel Nitinol Stent for Lesions up to 24 cm in the Superficial Femoral and Proximal Popliteal Arteries: 24-Month Results From the TIGRIS Randomized Trial

PURPOSE

To evaluate the safety and effectiveness of the TIGRIS stent for lesions up to 24 cm in the superficial femoral and proximal popliteal arteries (SFA/PPA).

METHODS

This prospective, multicenter, randomized study enrolled 274 subjects at 36 sites in the United States and Europe. Subjects were randomly assigned in a 3:1 ratio to treatment with the TIGRIS stent (n=197; mean age 66.7±9.28 years; 141 men) or LifeStent (n=70; mean age 67.9±8.87 years; 49 men). The primary safety endpoint was 30-day freedom from major adverse events (MAE). The primary efficacy endpoint was primary patency at 12 months. Secondary endpoints included target lesion revascularization (TLR) and stent fracture. Clinical success and quality of life were also assessed.

RESULTS

Mean lesion length (107.6 vs 117.9 mm, p=0.29), procedure success (99.5% vs 97.1%, p=0.17), and freedom from MAE (99.5% vs 100%, p>0.99) were similar for the TIGRIS and control groups, respectively. Likewise, there was no difference in primary patency at 12 months (60.6% vs 63.2%, p=0.73) or 24 months (56.3% vs 50.2%, p=0.60) or in TLR at the same time points (76.6% vs 80.6%, p=0.49; 70.5% vs 67.2%, p=0.85). There were no differences in the changes in Rutherford category or the ankle/brachial index through 24 months. The rate of stent fracture was lower for TIGRIS compared with LifeStent (0% vs 32.7%, p<0.001).

CONCLUSION

The TIGRIS stent and LifeStent were similarly effective for the treatment of lesions in the SFA and PPA. The high flexibility and zero fracture rate associated with the TIGRIS stent make this device favorable for use in high-flexion arteries.

Expandable Mg-based Helical Stent Assessment using Static, Dynamic, and Porcine Ex Vivo Models

A bioresorbable metallic helical stent was explored as a new device opportunity (magnesium scaffold), which can be absorbed by the body without leaving a trace and simultaneously allowing restoration of vasoreactivity with the potential for vessel remodeling. In this study, developed Mg-based helical stent was inserted and expanded in vessels with subsequent degradation in various environments including static, dynamic, and porcine ex vivo models. By assessing stent degradation in three different environments, we observed: (1) stress- and flow-induced degradation; (2) a high degradation rate in the dynamic reactor; (3) production of intermediate products (MgO/Mg(OH)₂ and Ca/P) during degradation; and (4) intermediate micro-gas pocket formation in the neighboring tissue ex vivo model. Overall, the expandable Mg-based helical stent employed as a scaffold performed well, with expansion rate (>100%) in porcine ex vivo model.

Nitinol Self-Expanding Stents for the Superficial Femoral Artery

The superficial femoral artery is a complex artery subject to a unique set of biomechanical loading conditions in its course through the leg. Plain balloon angioplasty and balloon-expandable stents had unacceptably high rates of restenosis, necessitating target vessel revascularization. Nitinol alloy is well suited to provide the strength and flexibility needed of stents to withstand the external forces posed by the environment of the superficial femoral artery. Advances in stent technology with the addition of a slow-releasing antiproliferative agent and changes in scaffold design have shown promise in reducing the rates of stent fracture and in-stent restenosis.

Cost-effectiveness of superficial femoral artery endovascular interventions in the UK and Germany: a modelling study

OBJECTIVES

To assess the lifetime costs and cost-effectiveness of 5 endovascular interventions to treat superficial femoral arterial disease.

DESIGN

A model-based health economic evaluation. An existing decision analytical model was used, with updated effectiveness data taken from the literature, and updated costs based on purchasing prices.

SETTING

UK and German healthcare perspectives were considered.

PARTICIPANTS

Patients with intermittent claudication of the femoropopliteal arteries eligible for endovascular treatment.

METHODS

UK and German healthcare perspectives were considered, as were different strategies for re-intervention.

INTERVENTIONS

Percutaneous transluminal angioplasty (PTA) with bail-out bare metal stenting (assumed to represent the existing standard of care, and 4 alternatives: primary bare metal stents, drug-eluting stents, drug-eluting balloons (DEBs) and biomimetic stents).

PRIMARY OUTCOME MEASURES

The incremental cost-effectiveness ratio between 2 treatments, defined as the incremental costs divided by the incremental quality-adjusted life years (QALYs).

RESULTS

Use of a biomimetic stent, BioMimics 3D, was always estimated to dominate the other interventions, having lower lifetime costs and greater effectiveness, as measured by QALYs. Of the remaining interventions, DEBs were always the most effective, and PTA the least effective. There was uncertainty in the cost-effectiveness results, with key drivers being the costs and effectiveness of the biomimetic stent along with the costs of DEBs.

CONCLUSIONS

All 4 of the alternatives to PTA were more effective, with the biomimetic stent being the most cost-effective. As there was uncertainty in the results, and all of the interventions have different mechanisms of action, all 4 may be considered to be alternatives to PTA.

Flow cytometry what you see matters: Enhanced clinical detection using image-based flow cytometry

Image-based flow cytometry combines the throughput of traditional flow cytometry with the ability to visually confirm findings and collect novel data that would not be possible otherwise. Since image-based flow cytometry borrows measurement parameters and analysis techniques from microscopy, it is possible to collect unique measures (i.e. nuclear translocation, co-localization, cellular synapse, cellular endocytosis, etc.) that would not be possible with traditional flow cytometry. The ability to collect unique outcomes has led many researchers to develop novel assays for the monitoring and detection of a variety of clinical conditions and diseases. In many cases, investigators have innovated and expanded classical assays to provide new insight regarding clinical conditions and chronic disease. Beyond human clinical applications, image-based flow cytometry has been used to monitor marine biology changes, nano-particles for solar cell production, and particle quality in pharmaceuticals. This review article summarizes work from the major scientists working in the field of image-based flow cytometry.