Introduction
There has been a dramatic change over the past several decades in management of patients with femoropopliteal occlusive disease transitioning from open to minimally invasive endovascular repair. Optimal medical therapy continues to be the first-line therapy for patients with claudication caused by femoropopliteal disease. This includes smoking cessation and cardiovascular risk reduction, including antiplatelet therapy, cholesterol manipulation, exercise therapy, and oral statins. Supervised exercise programs have proven to be efficacious, but they require consistent participation from highly motivated patients. Revascularization may be appropriate in patients with claudication who still have lifestyle altering symptoms despite medical management. Patients with critical limb ischemia (CLI) require intervention to achieve limb salvage. These patients usually have multilevel vascular disease and often require complex procedures.
Currently, in many centers, endovascular management of superficial femoral artery (SFA) and proximal popliteal lesions is the first-line therapy regardless of degree of stenosis, extent of calcification, total plaque occlusion, or length of the lesion.
Plaque etiology and composition impacts on the ability to perform endovascular procedures. Lesions can be composed of smooth muscle cell intimal hyperplasia, calcific lesions, thrombotic material, arterial necrotic core material, and a combination. The plaque constituents also impact procedure success and long-term patency. Studies have shown that the greater extent of calcification, the less the likelihood of immediate and long-term success.
Patient Evaluation
Many medical processes can cause lower extremity symptoms, and a careful history and physical help clarify the potential etiology. If there is concern for peripheral artery disease (PAD), we generally perform noninvasive vascular laboratory studies to evaluate further. We have found that these studies can accurately identify the arterial occlusive lesions and direct intervention. Arterial duplex confirms the location of the lesions and the extent and degree of calcification. If duplex reveals a long segment calcific SFA occlusion and an adequate venous conduit, we schedule the hybrid angiographic suite for diagnostic angiography and potential endovascular or open bypass. Other vascular surgeons and interventionalists have reported added benefit to preintervention CT angiography of the aorta and lower extremities, including more sizing of balloons and stents.
Arterial Access
In our institution, all arterial access is performed under ultrasonic guidance. The common femoral artery (CFA) is accessed antegrade or retrograde with micropuncture system. To confirm location and orientation, we pass the inner dilator of the micropuncture sheath into the femoral vessel and perform oblique angiogram, confirming optimal access. The micropuncture sheath with the inner and outer dilators reconnected is reinserted and the system exchanged to a 0.035′′ wire and 4–5-French sheath.
Access for femoropopliteal occlusive lesions are routinely performed antegrade or retrograde, with the approach tailored to patient anatomy. Antegrade access is used with patent aortoiliac, CFA, and proximal SFA, and planned intervention in mid-distal SFA, popliteal, or tibial vessels. Antegrade access allows greater “pushability” to traverse arterial total occlusions and control of the wire and catheter torque for selective catheterization of branch vessels. Steep aortic bifurcations and extremely tall patients, where catheter length becomes an issue, are well served by antegrade approach. Possible drawbacks are a higher rate of hematoma and pseudoaneurysm, although this may have abated in more recent series. Antegrade access can be more uncomfortable for the operator, as most endovascular suites are better oriented to facilitate retrograde femoral access. To maintain the usual orientation of controls and not have to work around the head and upper body of the patient, we frequently place a longer sheath into the proximal SFA, using an 0.035′′ support wire with approximately 20 cm of sheath externalized. The sheath is then gently curved to the patient’s contralateral groin in an approximation of up-and-over position. An occlusive Ioban drape secures this in place. This allows direct access from the more conventional retrograde approach, with added stability.
Similar technique is used for retrograde access. Retrograde access allows visualization of the suprarenal, perivisceral, aortoiliac inflow regions, and bilateral lower extremity arterial run-off vessels. Aorto-iliac angulation and calcification can make retrograde access more challenging. Once aortoiliac angiography has been completed, angiography of the contralateral lower extremity is performed. It is critical that angiography be carried out to the level of the foot to have a thorough understanding of the vasculature of the patient. To facilitate higher-quality imaging and decrease contrast load, imaging is performed from the contralateral external iliac artery. If the SFA is patent, the catheter is advanced to the popliteal over a wire and run-off of tibial and pedal vessels performed. If there is SFA occlusion, better visualization of the popliteal and tibial vessels may require a more proximal catheter in the external iliac artery, such that collateralization from the profunda femoral artery (PFA) allows visualization of the popliteal through geniculate vessels. Severe angulation within the aortoiliac segment can make passage of a sheath more challenging. Options for facilitating placement of an up-and-over sheath include positioning a wire within the contralateral distal SFA. If that is unsuccessful, passing a stiffer catheter with a more supportive wire, such as Rosen or Amplatz may facilitate sheath passage. If the sheath will still not pass, we take a long dilator and pass it over the stiffer wire into the contralateral iliac system. With the dilator in place, the shorter sheath can be advanced over the shoulders of the dilator into the contralateral iliac artery. Additionally, by separating the dilator and sheath slightly, it is often possible to “walk” the sheath over steep bifurcations. Finally, if the sheath will not advance, contralateral femoral access can be obtained and a small sheath inserted, snaring the wire. With through-and-through access, the sheath can be advanced into the iliac arteries.
Femoral Interventions
Once the sheath is in place, characteristics of the plaque determine type of intervention. Characteristics that impact intervention include calcification, location of the plaque relative to branch points, degree of stenosis, presence of previously placed stents, presence or absence of in-stent restenosis, and length of lesion. First, the plaque must be crossed with a guidewire. We usually use a 0.035′′ hydrophilic coated wire. Traversing a totally occluded plaque can be challenging but is possible even with long calcific lesions. A central luminal or true lumen crossing is considered by many to be optimal. In order to accomplish this, a supportive catheter is placed through the sheath and brought into close proximity of the total arterial occlusion. The hydrophilic wire gently probes the cap of the occlusion, attempting to find a small microchannel allowing the wire to engage and to advance. Care is taken not to form a loop at this point because of the high probability of a subadventitial dissection. The subadventitial plane is actually misnamed subintimal and is actually a plane between the media and adventitia, similar to the plane encountered when performing carotid endarterectomy.
Once the hydrophilic wire advances, the support catheter is advanced to allow better pushability and control of the wire. The tip of the wire is continually rotated in a circular fashion to attempt to stay in the central luminal plane. If there is significant spiraling of the wire, it is likely the wire is in the subadventitial plane. The wire and catheter are advanced in sequential fashion until the reconstitution point is reached. It is extremely important that the arterial reconstitution point is identified prior to attempting crossing, to prevent the catheter and wire from propagating a dissection flap within the patent vessel rather than re-entering the true lumen. In Fig. 33.1 , we demonstrate use of the Crosser for crossing the distal cap of a chronic total occlusion in order to maintain true luminal position. By stopping immediately proximal to the distal cap, a wire can be used to probe to find a re-entry point. Once the wire passes into the true lumen, the catheter should be advanced, the wire removed, and the catheter aspirated to see whether there is a blood return. If there is a blood return, an angiogram should be performed confirming true-lumen re-entry.
It is possible to have blood return even if the catheter is still in a dissection plane. If the proximal aspect of the plaque cannot be engaged or the central luminal plane cannot be re-entered, there are several options. First, especially in long SFA occlusions, the question should be asked whether the patient is a surgical candidate. The patency of long-segment transatlantic inter society consensus classification D (TASC D) lesions endovascular interventions have not been favorable and, when appropriate, surgical bypass is recommended.
If the patient is not a good candidate for bypass, the Bolia technique creates a narrow loop in the hydrophilic wire just proximal to the proximal cap, advancing the wire into the subadventitial plane (subintimal) down to the reconstitution point of the occluded artery and then using a directional catheter to re-enter into true lumen. This technique does create an eccentric dissection plane within the subadventitial plane, which may impact on success and complication rates.
There are devices designed to aid in the traversing of the proximal and distal caps. The Crosser (BD Bard, Franklin Lakes, New Jersey) has an indication for proximal plaque traversing. It is placed just proximal to the plaque, activated, and gently brought in contact with the proximal plaque ( Fig. 33.1 ). Using a hydraulic (jackhammer) affect, the device gently probes the proximal cap and attempts to engage into microchannels and is slowly advanced. Traversing the main portion of the plaque is generally fairly straightforward until the distal cap, which can also be somewhat dense. The device is advanced slowly and works to re-enter the true lumen. Care must be taken that the Crosser device does not advance within a subadventitial plane and create a dissection.
The step-by-step technique uses the Spectranetics Excimer laser (Philips Medical, Colorado Springs, Colorado). The laser fiber is brought into close proximity to the proximal plaque, activated, and gently allowed to advance into the proximal cap. Once the proximal cap has been traversed by the laser fiber, the wire is advanced, and allowed to track through the plaque until the distal cap is encountered. The laser may be required to be activated again, traversing through the distal cap. This technique also performs initial laser atherectomy of the underlying plaque.
All of the techniques described are most effective if performed as primary therapy, rather than being attempted once wire and catheter traversal has failed. With attempted wire catheter crossing, channels can be created so that the crossing devices will engage and follow the same path, rather than creating a new path. If the plaque can be traversed through the proximal cap and the main body of the plaque, even in a subadventitial plane, but re-entry cannot be accomplished, a re-entry device can be used.
Several devices are available, and mechanism of action is generally insertion of a curved needle into true lumen from the extraluminal plaque, either using ultrasonic (Pioneer, Philips, Amsterdam, Netherlands) or fluoroscopic guidance (Outback, Cordis, Hialeah, FL). This has been shown to be highly effective for re-entry and can be accomplished after failed wire catheter traversal attempts.
Finally, Spinosa described a retrograde tibial or popliteal access, SAFARI technique. A small sheath or a bareback 0.018′′ crossing catheter (our preference) is inserted into distal patent vasculature, usually by ultrasonic guidance, and manipulated proximally through the plaque. Once the wire has traversed the plaque, it is snared from above establishing through-and-through wire access, facilitating endovascular intervention. This is demonstrated in Fig. 33.2 , where retrograde peroneal artery access is shown. Additionally, SAFARI techniques can be combined with outback re-entry devices ( Fig. 33.3 ). In that case, an outback catheter is used in conjunction with retrograde puncture and balloon inflation in order to obtain antegrade access into a tibial vessel.
As the profiles of the endovascular devices have decreased, some authors recommend primary retrograde intervention from tibial or popliteal access, without antegrade catheterization. In cases of instant restenosis and occlusion, care has to be taken to assure that you stay within the stent and not traverse the interstices. If there is concern, a small balloon can be passed over the crossing wire to confirm that struts have not been traversed. The stent can also be accessed percutaneously under fluoroscopic guidance, and then the 0.035′′ wire can be advanced through the stent and captured with a snare for a through-and-through access if unable to cross from above or below ( Fig. 33.4 ).
Endovascular Treatment Options
Dr. Charles Dotter initially introduced sequential arterial dilatation using semi-rigid dilators in 1964. In 1979, Dr. Andreas Grüntzig described percutaneously placed balloon angioplasty (PTA), dramatically changing management of coronary artery disease and PAD. Initially POBA (plain old balloon angioplasty) was recommended for short, focal, nonoccluded stenosis, with reasonable results. There was concern for plaque recoil and restenosis, dissection, and vessel perforation. Shillinger reports 1-year patency of POBA at 37% in femoral lesions. To address this, metallic stents were developed. Because of the need for flexibility and mobility in lower extremity, self-expanding stents were developed. Initial stent results were good, with 1-year primary patency approximately 66%. Long-term complications include stent fracture, occlusion or in-stent restenosis, and recurrent symptoms. Short focal stents are more effective than long-segment, entire SFA stenting. Current attempts to improve outcomes of intra-arterial stent placement have included use of medications to inhibit the proliferative response resulting in intimal hyperplasia. The Zilver PTX (Cook Medical, Bloomington, IN) drug-eluting stent 5-year data have shown 80% clinical benefit versus 59% for POBA and patency of 66% Zilver PTX versus 43% POBA. Recently, Eluvia Drug Eluting Stent (Boston Scientific, Marlborough, MA) reported primary patency at 1 year of 88%. Our current practice for longer or complex arterial plaques is to use drug-eluding stents, when a stent is indicated, provided that no other antimyeloproliferative therapy is administered simultaneously. We tend to limit use of stents because of concern for long-term complications of stent fracture and the stent itself acting as a mechanical barrier to future therapeutic modalities. Additional antimyeloproliferative therapy is now available using primarily paclitaxel-coated balloons. There are multiple different drug concentrations and crystalline structures available on paclitaxel-coated balloons. A larger crystalline structure has been associated with potential longer duration of drug exposure in the arterial wall in a “depot” mechanism of action. There is concern for possible distal embolization in these larger crystalline coatings. This has not been shown to be clinically significant nor to impact wound healing. Safety-related outcomes, major amputation, and death have been equivalent between POBA and drug-coated balloon (DCB) groups in pivotal trials. The long-term clinical benefits of DCB use are more equivocal over longer follow-up. The LEVANT II trial of the CR Bard drug-coated balloon Lutonix showed significant improvement in primary patency at 12 months (65.2% versus 52.6%, P =0.02). However, this was reduced to a 5.6% improvement in primary patency at 24 months. Results of the Medtronic DCB IN.PACT SFA randomized trial have had more promising durability results, with primary patency advantage remaining at 36 months (69.5% versus 45.1%, P <0.001). The ILLUMENATE pivotal trial for the Stellarex drug-coated balloon, showed similar durable advantage for DCB up to 24 months.
In December 2018, a meta-analysis found an increase in later term all-cause mortality from exposure to paclitaxel.¹ At 2 years, all-cause mortality showed a negative impact, and by 4 to 5 years this was more pronounced. (14.7% versus 8.1% with an odds ratio of 1.93.) This meta-analysis was a compilation of three randomly controlled trials (Zilver-PTX, Thunder and IN.PACT SFA), none of which was powered to evaluate the impact on all-cause mortality. This has drawn significant attention and discussion by physicians, industry, vascular societies, and regulatory agencies. The US Food and Drug Administration (FDA) initially released a notification of their concern in January 2019. (Paclitaxel in much higher doses has been used in treatment of patients with breast cancer without associated increase in long-term all-cause mortality.) In March and June 2019, the FDA stated that “While analyses are ongoing, preliminary review of this data has identified a potentially concerning signal of increased long-term mortality in study subjects treated with paclitaxel-coated products compared to patients treated with uncoated devices.” Their analysis further showed “In total, among this 975 subjects in these three trials, there was an approximately 50% increased risk mortality in subjects treated with the paclitaxel coated devices (20.1% versus 13.4% crude risk of death at five years).” The FDA recommendations are to continue diligent monitoring, to make treatment recommendations, and to include in the informed consent process the potential increase in all-cause long-term mortality with a discussion of risk and benefits for all available PAD treatment options. For some patients who are typically high risk for restenosis, the benefits may outweigh the potential risk of using the paclitaxel-containing products, thereby justifying their use.
Before this analysis, we were fairly liberal with the use of paclitaxel-containing products in all PAD patients. We now tend to use other modalities in patients with claudication. In patients with CLI and long highly calcific lesions or restenotic lesions, we consider use of paclitaxel after a thorough discussion with the patient and include this as part of informed consent.
Polytetrafluoroethylene (PTFE) has been used to cover a self-expanding stent to prevent intimal hyperplasia formation through the interstices. Covered stents are also effective in treatment of complications, including arterial perforation, pseudo-aneurysm formation or shaggy thrombotic lesions. The VIBRANT trial reported that at 3 years, there was no difference in patency of Viabahn covered stent grafts compared with bare-metal stenting, although they did note a 50% stent fracture rate in the bare-metal stents compared with 2.6% in Viabahn. Retrospective series suggest there may be a utility to using Viabahn stents in long-segment chronic total occlusions because patency seems less dependent on lesion length.
Many plaques and recurrent stenoses are mixed consistency, including calcification, smooth muscle cell intimal hyperplasia, thrombus, and necrotic material. As a result of this mixed nature, POBA has been associated with distal embolization and outflow arterial occlusion. In patients with significant risk of thrombus or necrotic material, we advocate the use of mechanical thromboatherectomy in the initial intervention. If the hydrophilic wire easily passes through an occluded vessel, concern for thrombus or necrotic material is significantly increased. Mechanical thrombectomy with aspiration allows removal of this thrombus and necrotic material, as well as initial atherectomy debulking. This allows better visualization and selective endovascular intervention with spot stenting or post mechanical thrombectomy/atherectomy angioplasty. If there is significant thrombus burden within the plaque, distal embolic protection devices are generally utilized in conjunction with therapeutic interventions. Some authors recommend routine use of embolic protection devices in all endovascular interventions.
Angioplasty and stenting do not remove or debulk atherosclerotic lesions but simply disrupt the internal and/or external elastic lamina, allowing the lumen to increase. Atherectomy debulks plaque and removes it. Each of the atherectomy devices has strengths and weaknesses ( Table 33.1 ). The devices are defined by the mechanism in which it debulks and include directional, rotational, orbital, and laser photo-ablative devices. Directional devices can be used effectively in eccentric and concentric plaques, and typically atheromatous material is stored in the device nosecone, which requires intermittent removal and cleaning. The DEFINITIVE LE study prospectively reviewed 800 patients undergoing directional atherectomy, revealing a 78% primary patency and freedom from reintervention in lesions up to 20 cm in length in SFA, popliteal, and tibial vessels. Embolization rate was 3%, with 1.6% requiring intervention. Preliminary results indicate that using directional atherectomy and DCB compared with DCB alone is potentially effective in long or highly calcific lesions. Highly calcific lesions can act as a mechanical barrier to prevent the penetration of the antiproliferative agents to the medial smooth muscle cells. Debulking before DCB treatment could allow better exposure of the underlying smooth muscle cells to the antimyeloproliferative agent. Directional atherectomy can excise calcified lesions but is associated with significant distal embolization, and embolic protection devices should be routinely used. Rotational atherectomy allows aspiration and one-time insertion but are limited in luminal gain. However, the Jetstream atherectomy device (Boston Scientific) increased luminal diameter by approximately 3.4 mm. Rotational atherectomy is effective in removing organized thrombus and atherosclerotic plaque. Orbital atherectomy is effective with short focal calcific lesions and, theoretically, reduces calcified plaque to minuscule particles washed out through the outflow bed. It is not effective with thrombus or intimal hyperplasia. A large registry study found that plaque reduction was most effective in calcified lesions and least in soft, fibrotic lesions. This study included three orbital atherectomy devices manufactured by CSI (St. Paul, Minnesota). On average, lesions achieved a stenosis reduction of 35%–88% prior to angioplasty.
