Primary nitinol stenting for femoropopliteal disease

Determination effect of two different NiTi stents on the vessel wall and studying their flexibility using finite element method

Finite element simulation is used to analysis stent designs, extension as well as interaction between a stent and a vessel. In this paper, two different stents with different geometries have been simulated. One is Zilver stent and the other one is Navalis stent. The aim of this study is to determine the effect of stents deployment with various designs that are made of shape memory alloy (SMA) on the distribution of vessel wall stresses by using computational modeling approach. The constitutive model which described the behavior of SMA is based on Microplane model. In addition, SMA stents have been simulated under torsion loading to compare the flexibility of various designs under different conditions. The superelastic behavior and shape memory effect of SMA stents are investigated in this paper. The numerical simulation results show the different geometries of stents have significant effect on the arterial wall. The results show the Navalis stent causes less stress on the arterial wall and it is more flexible than the Zilver stent under the same torsion loading.

Ten-Year Clinical Follow-Up Following Bare-Nitinol Stent Implantation for Femoropopliteal Artery Disease

Aim: More than 5-year clinical outcomes after femoropopliteal (FP) stenting with bare-nitinol stent (BNS) have not yet been unclear. We investigate the long-term patency and mortality following FP stenting with BNS.

Methods: This study was a multicenter retrospective study of a prospectively maintained database. From April 2004 to December 2011, 1824 consecutive patients (2211 limbs) who underwent FP stenting with BNS for de novo lesions were selected and analyzed. Primary endpoint was primary patency which was defined as treated vessel without restenosis and reintervention and its associated factors.

Results: The prevalence of diabetes mellitus and dialysis was 60.5% and 23.8%, respectively. Chronic limb-threatening ischemia (CLTI) accounted for 30.8%. Chronic total occlusion (CTO) was found in 52.7%, and lesion length was more than 20 cm in 22.6%. During the median follow-up of 3.8 years (interquartile range, 1.4 to 7.4 years), 1049 cases lost patency, whereas 355 cases were dead without experiencing loss of patency. The primary patency (95% CI) was estimated to be 74.8%, 47.3% and 29.1% at 1-, 5- and 10-year. On multivariate analysis, female sex, age ≥ 80 years, diabetes, dialysis, CLTI, CTO, arterial calcification, long lesion (＞20 cm), and small vessel (≤ 4 mm) were the independent predictors of primary patency after FP stenting. In addition, the prognostic impact of age ≥ 80 years, CLTI, and arterial calcification was significantly attenuated afterwards (P＜0.05).

Conclusions: Ten-year patency after BNS implantation for FP disease has been continuously reducing up to 10 years and the prognostic impact of risk factors was changed over time.

Direct Stenting in Patients with Acute Lower Limb Arterial Occlusions: Immediate and Long-Term Results

PURPOSE

The purpose of this study is to accentuate the efficacy of direct stenting (stent placement without predilatation of the lesion) in patients with acute lower limb arterial ischemia (ALLI).

MATERIALS AND METHODS

Between January 2010 and September 2015, 16 patients (11 men and 5 women) underwent direct stenting of acute arterial occlusions. All patients had contraindication for surgical revascularization or catheter-directed thrombolysis. According to SVS/ISCVS Classification, six patients had IIa and ten patients IIb ALLI. The occlusions were located in CIA, EIA, SFA, or popliteal artery. Mean follow-up time with clinical examination and color Duplex ultrasonography was 37.6 months (range 1-72). We analyzed the technical and clinical outcomes of the procedures, as well the complications and patency rates.

RESULTS

Technical success was achieved in all patients (16/16) and there was significant clinical improvement in 15 patients. There was neither distal embolization nor procedure-related complications. During the 6 years of follow-up, four patients died due to non-procedure-related causes and there were two minor and one major amputations. The primary patency rates and the amputation-free survival rates were 93.7 and 87% at 1 year, 75.2 and 71.2% at 3 years, and 75.2 and 62.3%, respectively, at 6 years.

CONCLUSIONS

Direct stenting may be a valuable alternative procedure for acute arterial occlusions in selected cases with high technical success and significant clinical improvement.

LEVEL OF EVIDENCE

Level 4, Case Series.

Routine Endovascular Treatment With a Stent Graft for Access-Site and Access-Related Vascular Injury in Transfemoral Transcatheter Aortic Valve Implantation

Background—

Access-site and access-related vascular injury (ASARVI) is still a major limiting factor in transcatheter aortic valve implantation and affects the outcome of patients. Management strategies for ASARVI include manual compression, stent grafts, and vascular surgery. We hypothesized that the standard use of a self-expanding stent graft for the management of ASARVI is feasible and safe.

Methods and Results—

Of 407 patients treated by transfemoral transcatheter aortic valve implantation, 110 experienced ASARVI (27.0%). Of these, 96 (87.3%) were managed by the implantation of a self-expanding nitinol stent graft. In the majority of patients, minor vascular complications triggered the implantation of a stent graft (86.5%), mainly because of bleeding (90.6%) and dissection (5.2%) of the common femoral artery with high rates of primary treatment success (97.9%). Patients receiving stent grafts were more often female (62.2 versus 45.6%, P <0.01), had higher body mass indices (27.8±6.7 versus 25.7±4.7, P =0.01), and suffered more often from diabetes mellitus (34.4 versus 24.5%, P =0.04). Angiographic assessment after a median follow-up of 345 days (interquartile range, 23–745 days) revealed only one patient with moderate, asymptomatic instent-stenosis (1.0%). Compared with a propensity score–matched cohort of patients without ASARVI, stented patients had comparable long-term mortality, despite the occurrence of a vascular complication (1-year mortality: 17.7% versus 26.6%; stent versus matched cohort, respectively; P =0.1).

Conclusions—

Routine use of a self-expanding nitinol stent graft in selected patients experiencing ASARVI after transcatheter aortic valve implantation is feasible, safe, and associated with favorable short- and midterm clinical outcome.

Midterm Patency After Femoropopliteal Interventions

Purpose: To describe and compare primary patency rates in patients undergoing endovascular femoropopliteal interventions with standard or interwoven nitinol stents or drug-coated balloons. Methods: A cohort of 1292 patients was treated for symptomatic femoropopliteal occlusive disease classified as Rutherford category ≥1 at a large vascular center between June 2006 and August 2013 using either standard nitinol stents (SNS; n=432), interwoven nitinol stents (INS; n=470), or drug-coated balloons (DCB; n=390). Primary patency rates were assessed by ultrasound or angiographic readings for over 3 years of follow-up. Propensity score–matched pairs were formed to compare each treatment with another using survival analysis. Results: Survival curves of primary patency favored INS compared with SNS in 368 propensity score–matched pairs (p<0.001). Kaplan-Meier estimates at 1, 2, and 3 years were 86.6%, 76.4%, and 68.9%, respectively, in the INS group vs 60.5%, 46.1%, and 42.1%, respectively, in the SNS group. No significant difference (p=0.232) was seen for the comparison of SNS vs DCB in 284 matched pairs over long-term follow-up (primary patency estimates at 1, 2, and 3 years were 79.8%, 53.8%, and 32.9%, respectively, in the DCB group vs 60.5%, 44.8%, and 40.3%, respectively, in the SNS group). Survival curves of primary patency favored INS over DCB in 254 matched pairs (p<0.001). Kaplan-Meier estimates at 1, 2, and 3 years were 79.0%, 51.2%, and 30.1%, respectively, in the DCB group vs 89.0%, 76.9%, and 66.2%, respectively, in the INS group. Conclusion: Propensity score–based analysis of primary patency suggests profound differences in restenosis rates between various treatment modalities for femoropopliteal disease for over 3 years of follow-up.

Feasibility and Clinical Outcomes of Peripheral Drug-Coated Balloon in High-Risk Patients with Femoropopliteal Disease

BACKGROUND

Clinical outcomes of the drug-coated balloon (DCB) procedure in high-risk patients with femoropopliteal (FP) disease have not been investigated sufficiently.

METHODS

This retrospective, single-center study analyzed 87 patients (39% dialysis) and 97 affected legs (64% critical limb ischemia [CLI]) that underwent DCB for symptomatic FP disease from March 2013 to September 2014. Risk stratification was based on FeDCLIP (female, diabetes, dialysis, CLI, lesion length >150 mm and poor runoff) score. The DCB outcomes among the different risk groups were compared and factors predicting restenosis were analyzed during follow-up.

RESULTS

Most of study participants (84%) were moderate to high-risk patients. The procedural success rate was 100% and the 30-day major adverse vascular event rate was 2.1%. The mean lesion length was 178 ± 106 mm and the mean follow-up time was 428 ± 145 (range 50-782) days. The binary restenosis-free and clinically driven target lesion revascularization (CD-TLR)-free rates at 12 months were 77.5% and 84.3%, respectively, for all participants. No significant differences were observed in 1-year binary restenosis and CD-TLR rates in the low-, moderate-, and high-risk groups (60%, 84%, and 73%: p = 0.396; 78%, 89%, and 80%: p = 0.635, respectively). In multivariate analysis, lesion length >150 mm (Hazard ratio [HR]: 8.00, 95% confidence interval (CI) 1.12 to 55.6, p = 0.038) and Rutherford class 6 (HR: 7.09, 95% CI, 1.15 to 43.5, p = 0.034) were identified as independent predictors of binary restenosis.

CONCLUSIONS

Despite general comorbidities and advanced limb ischemia, 1-year outcomes of DCB in high-risk patients with FP disease were effective. The DCB procedure holds promise to improve vessel patency; however, lesion length >150 mm and major tissue loss were independent predictors for binary restenosis after the treatment.

Comparison of dual-antiplatelet therapy durations after endovascular revascularization of infrainguinal arteries

BACKGROUND

The optimal dual-antiplatelet therapy (DAPT) duration after endovascular revascularization of infrainguinal arteries is uncertain.

METHODS

This study examines DAPT prescription trends and 12-month major adverse limb events (MALEs; a composite of repeat endovascular or surgical revascularization, acute vessel thrombosis, or amputation of the target limb), major adverse cardiovascular events (MACEs; all-cause mortality, nonfatal myocardial infarction [MI], stroke, or coronary revascularization), fatal bleeding events, and those requiring interruption or discontinuation of DAPT (hemorrhagic complications) for patients enrolled into the Excellence in Peripheral Artery Disease (XLPAD) registry.

RESULTS

Data on 368 patients prescribed antiplatelet therapy were analyzed; 8.2% were prescribed antiplatelet monotherapy, 48.6% DAPT for ≤3 months, and 43.2% for >3 months. Patients in the >3 DAPT prescribed group were older, had preexisting coronary artery disease (CAD), and prior MI (all P < 0.001). Overall MALE in the ≤3 and >3-month DAPT prescribed groups were 22.3% and 23.9%, respectively (P = 0.541). Survival analysis showed significantly higher rates of MACE in patients prescribed >3-month DAPT (17.6% vs. 9.5%; P = 0.019). An "as-treated" analysis excluded 10 patients who were prescribed DAPT for >3 months and revealed similar rates of MALE (24.9% vs. 20.8%; P = 0.386) and MACE (12.2% vs. 14.8%; P = 0.443) in patients receiving ≤3 and >3 DAPT. Hemorrhagic complications were similar across all prescribed and "as-treated" DAPT groups.

CONCLUSIONS

After infrainguinal endovascular procedures, patients with underlying CAD were prescribed longer (>3 months) duration of DAPT and experienced more cardiovascular events compared with those prescribed ≤3 months of DAPT. Adverse limb events were similar in both groups.

A Study on the Effects of Covered Stents on Tissue Prolapse

Polyvinyl alcohol (PVA) cryogel covered stents may reduce complications from thrombosis and restenosis by decreasing tissue prolapse. Finite element analysis was employed to evaluate the effects of PVA cryogel layers of varying thickness on tissue prolapse and artery wall stress for two common stent geometries and two vessel diameters. Additionally, several PVA cryogel covered stents were fabricated and imaged with an environmental scanning electron microscope. Finite element results showed that covered stents reduced tissue prolapse up to 13% and artery wall stress up to 29% with the size of the reduction depending on the stent geometry, vessel diameter, and PVA cryogel layer thickness. Environmental scanning electron microscope images of expanded covered stents showed the PVA cryogel to completely cover the area between struts without gaps or tears. Overall, this work provides both computational and experimental evidence for the use of PVA cryogels in covered stents.

SUrgical versus PERcutaneous Bypass: SUPERB-trial; Heparin-bonded endoluminal versus surgical femoro-popliteal bypass: study protocol for a randomized controlled trial

Background

Endovascular treatment options for the superficial femoral artery are evolving rapidly. For long lesions, the venous femoropopliteal bypass considered to be superior above the prosthetic bypass. An endoluminal bypass, however, may provide equal patency rates compared to the prosthetic above knee bypass. The introduction of heparin-bonded endografts may further improve patency rates. The SUrgical versus PERcutaneous Bypass (SuperB) study is designed to assess whether a heparin-bonded endoluminal bypass provides equal patency rates compared to the venous bypass and to prove that it is associated with improved quality of life, related to a decreased complication rate, or not.

Methods/design

Two-hundred-twenty-two patients with peripheral arterial occlusive disease, category 3-6 according to Rutherford, will be randomized in two treatment arms; 1. the surgical femoro-popliteal bypass, venous whenever possible, and 2. the heparin-bonded endoluminal bypass. The power analysis was based on a non-inferiority principle, with an effect size of 90% and 10% margins (alpha 5%, power 80%). Patients will be recruited from 5 teaching hospitals in the Netherlands during a 2-year period. The primary endpoint is primary patency and quality of life evaluated by the RAND-36 questionnaire and the Walking Impairment Questionnaire. Secondary endpoints include secondary patency, freedom-from-TLR and complications.

Discussion

The SuperB trial is a multicentre randomized controlled trial designed to show non-inferiority in patency rates of the heparin-bonded endograft compared to the surgical bypass for treatment of long SFA lesions, and to prove a better quality of life using the heparin bonded-endograft compared to surgically treatment, related to a reduction in complications.

Medical and endovascular management of critical limb ischemia

Critical limb ischemia (CLI) is the term used to designate the condition in which peripheral artery disease has resulted in resting leg or foot pain or in a breakdown of the skin of the leg or foot, causing ulcers or tissue loss. If not revascularized, CLI patients are at risk for limb loss and for potentially fatal complications from the progression of gangrene and the development of sepsis. The management of CLI requires a multidisciplinary team of experts in different areas of vascular disease, from atherosclerotic risk factor management to imaging, from intervention to wound care and physical therapy. In the past decade, the most significant change in the treatment of CLI has been the increasing tendency to shift from bypass surgery to less invasive endovascular procedures as first-choice revascularization techniques, with bypass surgery then reserved as backup if appropriate. The goals of intervention for CLI include the restoration of pulsatile, inline flow to the foot to assist wound healing, the relief of rest pain, the avoidance of major amputation, preservation of mobility, and improvement of patient function and quality of life. The evaluating physician should be fully aware of all revascularization options in order to select the most appropriate intervention or combination of interventions, while taking into consideration the goals of therapy, risk-benefit ratios, patient comorbidities, and life expectancy. We discuss the incidence, risk factors, and prognosis of CLI and the clinical presentation, diagnosis, available imaging modalities, and medical management (including pain and ulcer care, pharmaceutical options, and molecular therapies targeting angiogenesis). The endovascular approaches that we review include percutaneous transluminal angioplasty (with or without adjunctive stenting); subintimal angioplasty; primary femoropopliteal and infrapopliteal deployment of bare nitinol, covered, drug-eluting, or bioabsorbable stents; cryoplasty; excimer laser-assisted angioplasty; excisional atherectomy; and cutting balloon angioplasty.

Atherectomy for infrainguinal peripheral artery disease

Compared to conventional percutaneous transluminal angioplasty (PTA) and stent implantation for arterial occlusive diseases, atherectomy offers the theoretical advantages of eliminating stretch injury on arterial walls and reducing the, rate of restenosis. Historically, however, neither rotational nor directional atherectomy, whether used alone or with adjunctive PTA, has shown any significant long-term benefit over PTA alone in the coronary or peripheral arteries. However, the SilverHawk Plaque Excision System has produced positive results in single-center prospective registries of patients with femoropopliteal and infrainguinal lesions, with reduced adjunctive PTA, minimal adjunctive stenting, and competitive 6-month and 12-month patency rates. In the observational nonrandomized TALON (Treating Peripherals with SilverHawk: Outcomes Collection) registry, freedom from target lesion revascularization was 80% for 87 patients at 12 months. Questions remaining for further research with this device include more accurate determination of an event rate for distal embolization, the appropriate use of distal protection, the value of and appropriate circumstances for adjunctive angioplasty, and definitive patency and clinical outcomes. Other atherectomy devices are discussed.