Endovascular Therapeutic Technique

Balloon Compliance

Balloon compliance is the expansive ability of the balloon, which is determined by the function of pressure and diameter. Currently available balloons for PAD are usually made of a plastic polymer with varying degrees of compliance. Compliance is expressed as a range from nominal pressure to rated burst pressure. Nominal pressure is defined as the pressure at which the balloon expands to its designed diameter and length, and generally lies somewhere between 4 to 10 atmospheres (atm). Rated burst pressure (RBP) is the pressure at which less than 1% of tested balloons will burst and beyond which the probability of rupture increases. RBP typically ranges from 6 to 20 atm.

Compliant balloons are usually made of polyolefin copolymer and polyethylene. These balloons, including semi-compliant balloons, are superior in trackability and are suitable for lesions in a curved portion of a vessel. Although they produce less vascular damage because of their gentle dilation, high-pressure inflation can result in a “doggie bone” effect that may damage the normal vessel proximal and distal to the lesion. Thus, a compliant balloon is not suitable for severe calcific lesions. However, an advantage of a compliant balloon is that a single balloon may be used for various vessel diameters.

Non-compliant balloons are referred to as high-pressure balloons or low compliance balloons. Most non-compliant balloons are made of polyethylene terephthalate or nylon-reinforced polyurethane. These materials improve the radial force of the balloon and allow high-pressure expansion. Non-compliant balloons are constructed to maintain their designed shape and size under high pressure and have a higher RBP compared with compliant balloons. Non-compliant balloons, preferred by most interventional specialists, exert more recoil force when used for severe calcific lesions or following insufficient expansion during postdilatation following stent deployment.

Profile and Balloon Ability

A balloon’s profile is usually expressed in French (Fr) size and is determined by the cross-sectional area and diameter of the balloon and shaft. A smaller profile is better than a larger profile for delivering to the lesion crossing severe stenotic lesions. Most peripheral balloons are deliverable via a 4- to 6-Fr compatible sheath. Balloons of 0.014 or 0.018-inch wire systems have a smaller profile compared to the 0.035-inch systems.

Cutting Balloons

The cutting balloon is a specialized device made of 3 or 4 microsurgical blades (atherotomes) mounted longitudinally along the surface of a standard PTA balloon ( Fig. 63.2 ). Peripheral cutting balloons (PCBs) require a 0.014- or 0.018-inch guide-wire system with a 6-Fr sheath. More specifically, small diameter (2–4 mm) PCBs are supported by a 0.014-inch guide wire and either an OTW or RX system. Large diameter (5–6 mm) PCBs are only used with a 0.018-inch guide wire with an OTW system. PCB length is typically 1.5–2.0 cm, and the nominal pressure of PCBs is 6 atm. Peripheral lesions that are suitable for treatment with a PCB are mainly short lesions. These include venous graft stenosis following bypass, bifurcation stenosis, highly calcified lesions, a no-stenting zone (such as common femoral or popliteal artery), and in-stent restenosis (ISR), as opposed to areas that require primary treatment of occlusive disease.

The midterm results of a retrospective study of PCBs versus conventional PTA (non-compliant balloons) for the treatment of short lesions of femoropopliteal artery stenosis were reported by Controneo et al. The results revealed better primary patency rates at 6, 12, and 24 months for the PCB vs. PTA group, with no recoil, dissection, or arterial tears requiring stents observed in the PCB group. In another study of 128 patients undergoing treatment of infrainguinal lesions, the primary patency rate following treatment with PCB was 82.1% at 1 and 2 years. In patients with critical limb ischemia (CLI), the primary patency rates at 1 and 2 years were 64.4% and 51.9%, respectively. In the treatment of short infrapopliteal bifurcation disease in 23 patients, the primary and secondary patency rates were estimated as 89.3% and 93.5% at 6 months and 77.7% and 88.8% at 12 months, respectively; the 1-year primary and secondary patency rates of the treated bifurcation were 74.2% and 87.0%. PCBs have also been utilized for hyperplastic stenosis in hemodialysis arteriovenous fistulae. In a review of several randomized trials, the patency of the target lesion at 6 months was significantly higher in the PCB group compared to the conventional balloon group implying greater freedom from restenosis without a significant increase in the complication rate. ^, Furthermore, in severely calcified lesions, calcium fracture was more often associated with rotational atherectomy followed by cutting balloon compared with rotational atherectomy followed by conventional balloon predilation before stenting. A strategy of rotational atherectomy followed by cutting balloon before stenting can increase the lumen diameter and acute lumen gain.

Scoring Balloons

The AngioSculpt balloons (AngioScore, Fremont, CA) and VascuTrak 2 (Bard Peripheral Vascular, Tempe, AZ) are designed to exert focal pressure on the lesions. The AngioSculpt balloon is composed of nitinol wires placed as spiral struts along the surface of a standard semi-compliant balloon. The 1-year outcomes of treatment for femoropopliteal lesions with the AngioSculpt balloon were reported by Lugenbiel et al., who treated 124 calcified femoropopliteal lesions in 101 consecutive patients. Overall, the primary patency rate after 12 months was 81.2%. Preparation with the AngioSculpt scoring balloon may offer a safe and valuable treatment option for calcified femoropopliteal lesions. The VascuTrak balloon catheter has two wires located along the longitudinal axis of the balloon to provide focal pressure, which is estimated to be approximately 50 to 400 times greater than a conventional balloon ( Fig. 63.3 ). Although there is no solid evidence supporting the VascuTrak, it is reported that its use in vessel preparation, and subsequent DCB angioplasty, was safe and effective in patients with femoropopliteal lesions.

Cryoplasty

Cryoplasty is a type of balloon angioplasty that combines the dilation force of balloon angioplasty with the delivery of cold thermal energy to the vessel wall. This system was expected to have the theoretical advantage of reduced myointimal hyperplasia in long-term patency and therefore avoid the need for stenting and reduce restenosis. When the balloon reaches the target lesion, liquid nitrous oxide inflates the balloon and exposes approximately 500 μm of the lesion to a cooling temperature of 14 degrees F (−10°C). Seven randomized controlled trials (RCTs) involving 478 patients with iliac, infrainguinal, femoropopliteal, and popliteal lesions treated by cryoplasty or conventional angioplasty were reviewed. There was no statistical difference between the treatment groups in target lesion patency and restenosis rates calculated at various periods in two primary cryoplasty trials. Adjunctive cryoplasty, which was performed for ISR of superficial femoral artery (SFA) lesions, was associated with improvements of patency only at 6-month (OR 5.37, 95% CI: 1.09–26.49). The authors concluded that the efficacy of cryoplasty over conventional angioplasty could not be proven. Since the effectiveness of cryoplasty is not supported, and there are additional costs ($1700) compared to conventional PTA, the value and role of cryoplasty for PAD is limited.

Drug-Coated Balloons

A drug-eluting balloon (DCB) is a non-stent technology for the effective homogenous delivery of antiproliferative drugs to the vessel wall through an inflated balloon. The balloon technology relies on targeted drug delivery, which helps in the rapid healing of the vessel wall and prevents the proliferation of smooth muscle cells. The drug-eluting stent (DES) was developed in 1999 to achieve local administration of an agent capable of inhibiting intimal hyperplasia without systemic side effects. The Cypher stent (Cordis Corporation, Fremont, CA), which was developed for the treatment of coronary artery disease, releases sirolimus. This is a macrolide antibiotic with a potent immunosuppressive effect that controls intimal hyperplasia. Subsequently, the TAXUS stent (Boston Scientific, Natick, MA), which is coated with paclitaxel, was developed as a second-generation DES. These stents could provide greater durability and reduce restenosis; however, they did not prolong life expectancy or decrease cardiac events compared to coronary bypass according to the SYNTAX trial. Moreover, dual antiplatelet drug therapy was required for 3 to 6 months after stent placement because of an increased risk of subacute thrombosis.

The DCB adopted the DES technology for the treatment of femoropopliteal or below-the-knee (BTK) lesions to treat de novo or restenotic lesions. The DCB consists of an OTW dual-lumen catheter with a distally mounted semi-compliant inflatable balloon and an atraumatic tapered tip. A minimum inflation time of 60 seconds is recommended in the instructions for use.

The LEVANT 1 trial was a European single-blind study that compared DCB and non-coated balloons. It evaluated the safety and efficacy of the Lutonix DCB (Bard Peripheral Vascular, Tempe, AZ) ( Fig. 63.4 ) for the treatment of femoropopliteal lesions. The Lutonix DCB is coated with a low dose of paclitaxel (2 μg/mm ² ) as an antiproliferative drug. The primary outcome of 6-month angiographic late lumen loss was significantly lower in the DCB group than in the uncoated group by intention-to-treat analysis (0.46 ± 1.13 mm vs. 1.09 ± 1.07 mm, P = 0.016). The primary patency rates were 72% in the DCB group versus 49% in the non-coated group at 6 months, and 67% in the DCB group versus 55% in the non-coated group at 12 months, respectively.

Consequently, LEVANT 2, a global, prospective, single-blind randomized trial, was conducted comparing Lutonix DCB with standard PTA. In this trial, 476 patients with symptomatic intermittent claudication or rest pain were randomly assigned in a 2:1 ratio to undergo angioplasty using DCB or a standard balloon for the treatment of femoropopliteal arterial disease. The primary patency rate (primary endpoint) of the DCB group was superior to the standard PTA group (65.2% versus 52.6%, P = 0.02). Additionally, the proportion of patients free from death or limb-related death at 12 months, amputation, or reintervention was 83.9% in the DCB group versus 79.0% in the standard PTA group, with no statistical difference.

The RANGER SFA study, the IN.PACT SFA study, and the ILLUMENATE study demonstrated the greater efficacy of paclitaxel-coated balloons over PTA in the SFA. Recently, the data of 3 years after DCB treatments became available revealing a durable and superior treatment effect among patients treated with DCB versus standard PTA, with significantly higher primary patency and lower clinically driven target lesion revascularization.

The LEVANT 2, the RANGER SFA, and the ILLUMENATE balloons are coated with paclitaxel at a dose density of 2 μg/mm ² , whereas the IN.PACT balloon coating has a dose density of 3.5 μg/mm ² . A recent systematic review and meta-analysis of summary-level data from 28 RCTs suggested an increased risk of death after femoropopliteal artery DCB treatment, beginning 2 years after the DCB procedure. The systematic review and meta-analysis of Katsanos et al. found an almost 2-fold increase in the relative risk for all-cause mortality after treatment with paclitaxel-containing devices compared with uncoated PTA for femoropopliteal PAD. However, this analysis has been criticized for its lack of long-term, homogeneous, patient-level data that might have identified confounding factors to better explain the observations. In the patient-level meta-analysis of the ILLUMENATE study at 3 years, there was no significant difference in all-cause mortality between the two cohorts through a full follow-up of the 589 patients for 3 years. Schneider et al. published the outcomes of a patient-level meta-analysis comprising 2 RCTs and 2 single-arm trials of 1980 patients: 1837 patients treated with a higher-dose paclitaxel-coated balloon from a single manufacturer and 143 patients treated with PTA with an uncoated balloon. Overall, there was no statistically significant difference in all-cause mortality between patients treated with DCB versus PTA through 5-year follow-up (15.1% vs. 11.2%, P = 0.09).

Initially, favorable outcomes have been presented for several DCB trials, but their long-term patency and safety remain unclear. Therefore, further long-term follow-up will be required to decide whether DCB therapy is appropriate for the treatment of complex stenotic lesions or occlusive lesions in infrainguinal PAD.

Balloon-Expandable Stents

The first commercially available balloon-expandable bare metal stent is the Palmaz stent. The efficacy of this stent has been validated in clinical trials. BESs are slotted metal tubes that are mounted, or “crimped,” onto a balloon suited to the diameter of the target vessel. The balloon is inflated to deploy the stent and secure it to the vessel wall. At first, the proximal and distal ends of the stent are expanded into a “doggie bone” shape, and subsequently, the middle portion of the stent is expanded. These stents are typically rigid to provide resistance against elastic recoil, but they may become irreversibly deformed when subjected to an external compression force. Thus, these stents are suitable for vessels that are not prone to external compression. Other advantages of BESs are the ability to place them precisely, and that they tend to be more radiopaque than SESs. Therefore, BESs are better suited to treat calcific ostial lesions involving the renal, mesenteric, iliac, subclavian, or brachiocephalic arteries. They are contraindicated for vessels prone to external compression, including the internal carotid artery and SFA. BESs may foreshorten if they are over-distended beyond their intended diameter. Furthermore, most stents made of a stainless alloy cause artifacts (signal loss) with magnetic resonance imaging (MRI). Although most BESs are made from stainless steel, newer BESs are composed of cobalt-chromium, which is stronger and provides a greater radial force with a lower crossing profile and enhanced flexibility.

Self-Expanding Stents

SESs are typically composed of nitinol, a nickel–titanium alloy, which provides flexibility and shape-memory. Due to the elastic properties of nitinol, stents with a diameter greater than the target reference vessel are selected so that they exert an outward force, resulting in appropriate vessel wall apposition. The eventual diameter of a lesion treated with an SES is a balance between the recoil of the lesion and the radial expansion force of the stent. SESs are more flexible than BESs, which provides greater trackability, allows for the navigation of tortuous vessels, and resistance to fracture. As a result of their elastic property, the diameter sizing of the stent is more forgiving than BESs, and an SES generally apposes well to the vessel with less chance of vessel perforation. In addition, because nitinol is a nonferromagnetic metal, it is less likely to create artifacts on MRI. The radial strength, flexibility, and most importantly, the maneuvers for deployment differ by manufacturer. Most SESs are stored in the delivery sheath, and they are deployed from the distal to the proximal end of the stent by unsheathing. Once deployed, most SESs cannot be restored or repositioned, with the exception of the Wallstent (Boston Scientific, Natick, MA), which can be repeatedly sheathed and repositioned. With the exception of the Misago stent (Terumo, Somerset, NJ), SES platforms are OTW systems. Various modifications have been developed aiming at improving performance in calcified lesions or areas subject to significant external stresses such as the adductor canal or the knee joint. In the Supera (Abbott Cardiovascular, Plymouth, MN) peripheral stent, a woven self-expanding stent constructed from nitinol, six pairs of closed-ended interwoven nitinol wires are arranged in a helical pattern designed to provide increased flexibility and resistance to fracture.

SESs are classified as open-cell or closed-cell design. An open-cell stent is a cylindrical structure of stacked serrated metal. The current stents, such as SMART (Cordis Corporation, Fremont, CA), Misago (Terumo, Somerset, NJ), EPIC (Boston Scientific Corporation, Natick, MA), Lifestent (Bard Peripheral Vascular, Tempe, AZ), and E-Luminexx (Bard Peripheral Vascular, Tempe, AZ) are composed of an open-cell configuration for the body of the stent and a closed-cell configuration for the stent edge. Although the open-cell structure has high flexibility, it is more susceptible to deformation, bending (strut), and could exert a non-uniform radial force on the target vessel. In addition, due to the large cell size, it is prone to plaque protrusion through the strut. However, the open-cell design allows for better tracking through tortuous vessels. In contrast, with a closed-cell design, all edges and vertices of the stent cells constituting the mesh are shared with an adjacent cell. Thus, it is advantageous for lesions at risk of embolization because the stent mesh is very fine. The disadvantages of closed-cell stents include less flexibility, which makes them less deliverable, and they also conform less well to tortuous vessels compared to open-cell stents.

Balloon-Expandable Covered Stents

There are several balloon-expandable covered stents available for use: the i-Cast (Atrium Medical Corporation, Hudson, NH) ( Fig. 63.5 ), Viabahn VBX (W.L. Gore & Associates, Flagstaff, AZ) ( Fig. 63.6 ), LifeStream (Bard Peripheral Vascular, Tempe, AZ), JOSTENT (Abbott Vascular Inc., Redwood, CA), and BeGraft (Bentley InnoMed, Hechingen, Germany). The i-Cast (Advanta V12) is made of 316L stainless-steel stent struts encased in PTFE fabric. This stent graft can be expanded beyond the stated stent diameter, although at the cost of foreshortening. All i-Cast stent grafts of <10 mm require 0.035-inch guide wire and 6- to 7-Fr sheaths depending on the diameter. This stent graft is approved by the FDA for the treatment of tracheobronchial strictures but not for PAD. However, it has been used off-label for various vessels such as the iliac or renal artery for occlusive lesions and perforation after PTA or stenting, and ISR. It has also been used for in-branch reconstruction for fenestrated endovascular treatment of thoracoabdominal aortic aneurysms. An advantage of the i-Cast is that it has the lowest profile. However, as with the balloon-expandable bare metal stent, due to its rigidity, the device is not suitable for tortuous vessels or lesions that are subject to structural changes. Although the improvement in patency using an i-Cast for the treatment of occlusive lesions has been demonstrated, data are limited. Long-term data are only available for the i-Cast device, which has a primary patency rate of 74.7% at 5 years.

Self-Expandable Covered Stents

There are three main devices: the Viabahn (W.L. Gore & Associates, Flagstaff, AZ), Fluency (Bard Peripheral Vascular, Tempe, AZ), and Flair (Bard Peripheral Vascular, Tempe, AZ). The Viabahn endoprosthesis consists of heparin-bonded PTFE attached to a nitinol stent. It is composed of a single-wire nitinol stent frame, without longitudinal connections, that is attached to the PTFE graft material with a thin film. These two proprietary design features confer its flexibility.

The VIPER trial, a prospective, single-arm, non-RCT, was conducted to evaluate primary patency at 12 months or performance of the device for the treatment of long SFA occlusive disease. The overall primary patency was 73%, and notably, patency was not significantly different for the lesion length over 20 cm or under 20 cm (70% vs. 75%). Subsequently, the VIASTAR trial, a randomized, prospective, single-blind, multicenter study, compared the Viabahn endoprosthesis with a conventional bare metal stent in 141 patients with symptomatic SFA lesions (Rutherford stage 2–5). ^, At 24 months, the overall primary patency rates of the Viabahn and the bare metal stent were 63.1% vs. 40.0%, respectively ( P = 0.004). The patency rate of the Viabahn device at 24 months for lesions ≥20 cm was higher than that of the bare metal stent (65.2% vs. 26.7%; P = 0.004). Freedom from bypass surgery and TLR and secondary patency were comparable between the two groups. Restenotic lesions after deployment of the Viabahn are usually focal and limited to both edges of the graft ( Fig. 63.7 ). Restenosis occurring after the bare metal stent, however, usually develops diffusely throughout the stent. The Viabahn endoprosthesis requires 0.018-inch wires and 6- to 7-Fr sheaths, depending on the diameter of the device, and the available length ranges from 2.5 cm to 25 cm. The Viabahn is deployed by withdrawing a ripcord and is similar to that of the Excluder stent graft (W.L. Gore & Associates, Flagstaff, AZ).

The Flair endograft, like the Viabahn, is composed of a nitinol stent and PTFE fabric. This graft is used in hemodialysis patients for the treatment of arteriovenous graft anastomotic stenosis. The tip of the graft has either a straight or flared shape. This graft has demonstrated improved patency compared with the standard PTA. The required delivery sheath is 9 Fr and it is supported by a 0.035-inch wire. The Fluency stent is approved by the FDA only for biliary application, and its vascular use is off-label. This stent graft is made of a nitinol stent based on the design of the Luminex stent and encapsulated with PTFE along its length, except for 2 mm at either end where the stent is flared. Its crossing profile is 9 Fr sheath compatible. The Fluency is supported by 0.035-inch wires, and the deployment method is like other self-expanding bare metal stents in which the stent is deployed by withdrawing the covering sheath.

Drug-Eluting Stents

Stents have shown improved patency in the treatment of PAD compared to conventional balloon angioplasty. However, the incidence of ISR and stent thrombosis due to intimal proliferation became apparent when treating long lesions with multiple stents. The DES was developed to overcome this, initially for coronary arteries. DESs are loaded with agents such as Paclitaxel and sirolimus, usually using polymers, and have been shown to dramatically improve the patency and ISR rates in coronary stenosis. ^, Subsequently, the coronary DES technology was applied to the femoropopliteal segment. The sirolimus-eluting stent, based on the SMART stent (Cordis Corporation, Fremont, CA), was the first peripheral DES. It was compared to a bare metal SMART stent in the prospective randomized SIROCCO I and II trials. ^, However, the restenosis rates at 24 months were not reduced (22.9% in sirolimus-eluting SMART stent versus 21.1% in bare metal SMART stent), and the program was terminated. The Dynalink stent (Abbott Vascular Inc., Redwood, CA), which is an everolimus-eluting stent, also failed to show superiority at 12 months (unpublished) compared with the historical controls of the STRIDES trial. Neither study was able to show a statistically significant difference between the “limus”-eluting stents and their respective bare metal counterparts.

The Zilver PTX stent (COOK Medical, Bloomington, IN) is a unique DES since it does not utilize a polymer to load the paclitaxel; the drug is simply applied to the stent. It has a 3 μg/mm ² dose of paclitaxel, which upon implantation is released during the first few days and remains in the vessel wall for up to 56 days. The sustained patency and freedom from TLR of the Zilver PTX stent were proven in a landmark multinational RCT with 479 patients, comparing primary Zilver stents with PTA with or without standard stents for the treatment of femoropopliteal (above-the-knee) lesions. In this trial, patients with symptomatic PAD underwent primary DES or standard PTA. When PTA patients suffered from flow-limiting dissection and required placement of a stent, secondary randomization was performed between bare metal stent and Zilver PTX. The primary patency rates at 12 months for the Zilver DES and PTA were 83.1% and 32.8%, respectively ( P < 0.001). In addition, the secondary randomization showed that the primary patency rate of the DES was superior to the patency rate of the bare metal stent group at 12 months (89.9% vs. 73.0%; P = 0.01), and the sustained superiority of the Zilver PTX stent has been demonstrated up to 5 years.

The Eluvia drug-eluting stent has drug-eluting technology designed to deliver controlled, localized, low-dose amorphous paclitaxel to the target lesion. Eluvia is built on the Innova stent platform, and the polymer allows the 0.167 μg/mm ² paclitaxel dose drug delivery to sustain beyond 1 year.

The IMPERIAL randomized cohort is a prospective, single-blind multicenter RCT comparing the Eluvia stent ( n = 309) to the Zilver PTX ( n = 156). The primary patency was 86.8% in the Eluvia group and 81.5% in the Zilver PTX group ( P < 0.0001). In all, 94.9% of patients in the Eluvia group and 91.0% of patients in the Zilver PTX group had not had a major adverse event at 12 months ( P < 0.0001), and no deaths were reported in either group. The Eluvia stent was noninferior to the Zilver PTX stent in terms of primary patency and major adverse events at 12 months after the treatment of patients for femoropopliteal PAD.

Multilayer Stents

The Multilayer Flow Modulator (MFM) stent is designed to exclude peripheral or visceral aneurysms while maintaining branch vessel flow. The MFM is an uncovered SES with high radial force and flexibility, constructed of braided fatigue and corrosion-resistant cobalt-alloy wire. The 3-dimensional wire layering of the MFM, which permits porosity in the range of 65%, alters blood flow and supports the formation of an organized, stable-layered thrombus inside the aneurysm sac. The Cardiatis MFM (Cardiatis, Isnes, Belgium) was approved in Europe in 2009. The first case report detailing implantation in a human was for a patient with a renal artery aneurysm, involving a branch of the renal artery. The efficacy of the Cardiatis MFM for the treatment of peripheral and visceral aneurysms was evaluated in an Italian multicenter trial. The primary patency at 1 year was 86.9%, and the cumulative side branch patency was 96.1%. Complete thromboses of aneurysms were achieved in 93.3%, and no aneurysmal rupture occurred. The MFM is currently being investigated for the management of complex aortic dissection or as a supplement to endovascular aortic repair.

Bioabsorbable Stents

The concept of bioresorbable vascular scaffolds (BVSs) with additional antiproliferative drug delivery has recently attracted great interest. These devices unify the advantages of metallic stents and DCBs by offering acute vessel support and limiting neointimal hyperplasia and late lumen loss. They ultimately disappear and allow the return of physiologic vasomotion. Full BVS resorption over 2–3 years could facilitate future endovascular procedures, and the previously stented segment could even serve as a suitable landing zone for bypass surgery. Bioabsorbable stents that were initially developed for coronary interventions are being applied to the peripheral arterial fields. The first coronary absorbable stent implanted in a human was the Igaki–Tamai stent (Igaki Medical Planning Company, Kyoto, Japan), which is made of poly-L-lactic acid and consists of a helical coil with a straight bridge configuration. In the peripheral fields, long, complex femoropopliteal lesions with a high degree of calcification were not suitable for the currently available technologies. The Igaki–Tamai stent was the first BVS to be evaluated for femoropopliteal interventions. The GAIA study, the most informative series testing this device, evaluated 30 femoropopliteal lesions with a mean length of 5.9 cm. Although immediate technical success was 96.7%, the binary restenosis rate for the 6 and 12 months follow-up was 39.3% and 67.9%, respectively. Histopathologic analysis of restenosis from eight specimens showed a mixed picture with hyperplastic tissue and remnants of stent struts (37.5%), inflammatory cells (50%), and thrombus (50%). A prospective, multicenter, observational registry from Belgium composed of 99 patients who received the Igaki–Tamai BVS reported lower patency rates (58% at 12 months), compared with contemporary studies using modern nitinol stents in the SFA. Considering these results, it is unclear if and when the technology will advance enough to replace modern metallic permanent implants for PAD.