Atherectomy for Peripheral Arterial Disease
Bennett Cua, MD, FACC
Mahmoud Abdelghany, MD
Robert R. Attaran, MD, FACC, FASE, FSCAI, RPVI
Key Points
The principles and goals of atherectomy include plaque modification, debulking, vessel preparation, and minimizing the need for stent deployment.
The mechanisms of atherectomy by excimer laser include plaque debulking by photochemical, photothermal, and photomechanical for plaque ablation.
Orbital atherectomy, directional atherectomy, and forward-cutting atherectomy are other FDA-approved methods of atherectomy.
I. Introduction
A. Percutaneous Interventions for Peripheral Artery Disease Percutaneous interventions for peripheral artery disease (PAD) continue to rapidly evolve providing a variety of tools to restore lower extremity blood flow. However, the paucity of randomized control trials comparing these different revascularization techniques has left us without an evidence-based roadmap to guide treatment. Although the advent of nitinol stents has greatly reduced early restenosis after balloon angioplasty by addressing complications such as vessel dissection and elastic recoil during the index procedure, its long-term success remains hampered by in-stent restenosis (ISR). Drug-coated technology including stents and balloons, scoring balloons, and atherectomy devices are all potential tools for prevention and treatment of ISR. Current practices are based predominantly on evidence gathered from small safety trials and single-center experiences with a few selective randomized control trials.
B. Zilver PTX DES The Zilver PTX paclitaxel-coated nitinol drug-eluting stent (DES) (Cook Medical, Bloomington, IN) has gained popularity for the treatment of femoropopliteal arterial stenoses with a proven superior 12-month event-free survival and patency rates compared with balloon angioplasty with provisional bare metal stent (BMS), but it is important to note that the average lesion length was only 6.5 cm.1 More recently, 5-year follow-up data were published2 comparing Zilver PTX with balloon angioplasty. The Zilver PTX DES demonstrated sustained superiority in freedom from reintervention compared with balloon angioplasty.
C. Treatment Nevertheless, the optimal treatment strategy for longer lesions that are more frequently seen in real-world practice remains unclear, and the role for atherectomy remains to be seen.
II. Principles of Atherectomy
The fundamental aim of atherectomy is (1) plaque modification to facilitate passage of other endovascular equipment and balloon expansion, (2) debulking of atherosclerotic and calcium burden to maximize luminal diameter gain, (3) vessel preparation to avoid suboptimal
balloon angioplasty, and (4) to minimize the need for stent deployment. There are several different types of atherectomy devices designed to cut, shave, sand, or vaporize plaques in diseased arteries. Current data do not support use of atherectomy devices alone in de novo lesions but instead may be a helpful adjunct to revascularization. For example, vessel preparation by directional atherectomy (DA) before balloon angioplasty with drug-coated balloon (DCB) was effective and safe. Although the DEFINITIVE AR study (Directional Atherectomy Followed by a Paclitaxel-Coated Balloon to Inhibit Restenosis and Maintain Vessel Patency—A Pilot Study of Anti-Restenosis Treatment) did not show a significant difference between DA plus DCB in comparison with DCB only for the treatment of femoropopliteal artery disease at 1 year; patients treated with DA plus DCB had higher technical success rate (89.6% vs 64.2%; P = .004) and lower flow-limiting dissection rate (2% vs 19%; P = .01) compared with DCB only.3
balloon angioplasty, and (4) to minimize the need for stent deployment. There are several different types of atherectomy devices designed to cut, shave, sand, or vaporize plaques in diseased arteries. Current data do not support use of atherectomy devices alone in de novo lesions but instead may be a helpful adjunct to revascularization. For example, vessel preparation by directional atherectomy (DA) before balloon angioplasty with drug-coated balloon (DCB) was effective and safe. Although the DEFINITIVE AR study (Directional Atherectomy Followed by a Paclitaxel-Coated Balloon to Inhibit Restenosis and Maintain Vessel Patency—A Pilot Study of Anti-Restenosis Treatment) did not show a significant difference between DA plus DCB in comparison with DCB only for the treatment of femoropopliteal artery disease at 1 year; patients treated with DA plus DCB had higher technical success rate (89.6% vs 64.2%; P = .004) and lower flow-limiting dissection rate (2% vs 19%; P = .01) compared with DCB only.3
III. Excimer Laser Atherectomy
Spectranetics is the manufacturer of four excimer laser atherectomy devices for infrainguinal lower extremity arteries: (1) Turbo-Elite (previously CliRpath), (2) Turbo-Booster, (3) Turbo-Tandem, and (4) Turbo-Power (Fig. 14.1). The first device is used for both above- and below-the-knee arteries, whereas the latter three devices are for above-the-knee lesions.
A. ELA System Mechanics
The Spectranetics (Maple Grove, MN) excimer laser atherectomy devices emit a xenon chloride (XeCl) ultraviolet light from the fiberoptic catheter tip at a wavelength of 308 nm, ablating atherosclerotic plaque and vaporizing thrombi at a penetration depth of 50 µm by a combination of photochemical, photothermal, and photomechanical effects while minimizing damage to surrounding tissue.4 Through the photochemical process, the high-energy, monochromatic laser beams directly break the molecular carbon-carbon bonds of atherosclerotic plaque or thrombus with subsequent dissipation of energy. The released energy, through the photomechanical effect, evaporates the intracellular water ahead of the tip of the laser catheter, producing a steam bubble that rapidly expands and contracts resulting in tissue breakdown. The laser emission is pulsed rather than continuous like its Argon predecessors, minimizing the photothermal process as excessive heating promotes aneurysm formation, late perforations, and a high restenosis rate. Each pulse is 125 ns with 80 pulses delivered per second. This calculates to less than 1 mm of atherosclerotic plaque ablated per second necessitating slow advancement of the laser to ensure that the advancement rate does not exceed the tissue removal rate in to maximize
luminal diameter gain of the vessel. The residual particles measure less than 10 microns in diameter conferring minimal risk of distal embolization.5 The laser should only be activated after saline flush to remove iodinated contrast material from the target blood vessel, because contrast and hemoglobin absorb the excimer laser light at 308 nm, yielding cavitation bubbles, vapor bubbles, and percussive waves, which can lead to dissections or perforations.6
FIGURE 14.1: Turbo-Elite Laser Atherectomy Catheter. Courtesy of Royal Philips.
B. ELA for Critical Limb Ischemia
1. The Laser Angioplasty in Critical Limb Ischemia (LACI) Belgium trial published in 2005 demonstrated the safety and efficacy of the Turbo-Elite (previously CliRpath) for treatment of critical limb ischemia (defined as Rutherford category 4, 5, or 6) in poor surgical bypass candidates.6 There was fairly even distribution of lesions between femoropopliteal, infrapopliteal, and multilevel lesions. The standard endovascular method of crossing the lesion with a guidewire followed by over-the-wire lasing was successfully executed in 84% (43 of 51) of cases with the remainder 16% (8 of 51) of lesions requiring a step-by-step technique to achieve recanalization. The step-by-step technique involves sequential advancement of the guidewire and activation of the laser catheter in a telescoping fashion until the entire length of the occlusion is crossed. Adjunctive PTA, stenting, and a combination of PTA with stenting were used in 33%, 6%, and 47%, respectively. Limb salvage of the treated limb at 6 months (study primary endpoint) was 90.5% and freedom from critical limb ischemia was 86%.
2. The LACI Phase 2 trial also studied the Turbo-Elite enrolling patients in the United States and Germany with the same inclusion and exclusion criteria as LACI Belgium but comparatively resulted in a cohort with a higher incidence of diabetes and nonhealing ulcers (Rutherford category 5-6). Reflective of the cohorts’ poor protoplasm, there was a 10% mortality rate at 6 months almost exclusively from cardiac causes. The primary endpoint of 6-month limb salvage was achieved in 93% of surviving legs. The step-by-step technique was used in 17% (26 of 145) of cases with minimal additional risk while significantly increasing the success rate of crossing total occlusions. Adjunctive PTA and stent placement were required in 96% and 45% of cases, respectively.7
C. ELA in Claudicants
1. The Turbo-Elite laser catheter’s en face, concentric laser orientation limited its ability to optimally treat femoral-popliteal lesions as it was unable to create a lumen much larger than the nominal diameter of the ablation catheter.8 Directional lasing allowed for more complete removal of atherosclerotic plaque, neointimal hyperplasia, and thrombus by off-axis lasing, which was incorporated into the Turbo-Elite with the addition of a bias guide catheter.9 This first directional lasing catheter was known as the Turbo-Booster. The Turbo-Tandem followed as the second-generation directional ELA catheter. The Turbo-Power is the newest generation ELA catheter that has removed the bias guide catheter while still preserving its directional functionality with a newly designed eccentric tip.
2. CliRpath Excimer Laser System to Enlarge Lumen Openings (CELLO) was a single-arm, prospective registry published in 2009 studying the efficacy and safety of using the Turbo-Booster with the Turbo-Elite to increase luminal diameter of the superficial femoral and popliteal artery above the knee joint in patients with intermittent claudication. The average lesion length was 5.6 cm with 61.5% with moderate-to-severe calcification. The tandem use of Turbo-Elite followed by Turbo-Booster achieved both efficacy and safety primary endpoints with a reduction in index lesion percent diameter stenosis prior to any adjunctive therapy from 77% + 15% at baseline to 34.7% + 17.8% with no major adverse events (MAEs) at 6 months. Intravascular ultrasound (IVUS) data from CELLO showed that luminal diameter gain achieved with ELA had equal contribution from plaque debulking and vessel enlargement demonstrated by an increase in external elastic membrane circumference.8
D. ELA for In-Stent Restenosis (Table 14.1)
1. The Turbo-Booster, Turbo-Tandem, and Turbo-Power are the only atherectomy devices approved for treatment of femoral-popliteal ISR lesions (level 1 clinical evidence).
2. The Photoablation Using the Turbo-Booster and Excimer Laser for In-Stent Restenosis Treatment (PATENT) study in 2014 used the Turbo-Elite to create a pilot channel followed by a mean of 5.7 passes with the Turbo-Booster to treat symptomatic femoropopliteal ISR, which achieved a high procedure success rate but with only primary patency at 6 and 12 months of 64.1% and 37.8%, respectively.10
3. The EXCImer Laser Randomized Controlled Study for Treatment of FemoropopliTEal In-Stent Restenosis (EXCITE-ISR) trial in 2015 is the first large, prospective, randomized control trial that demonstrates superiority in terms of procedural success (93.5% vs 82.7%; P = .01) with significantly less procedural complications (major dissections, residual stenosis >30%, or need for bailout stenting), 6-month freedom from target lesion revascularization (TLR) (73.5% vs 51.8%; P < .005), and 30-day MAE rates (5.8% vs 20.5%; P < .001) when using ELA in addition to percutaneous transluminal angioplasty (PTA) versus PTA alone to treat bare nitinol in-stent restenosis.11 The average lesion length was 19.6 cm in the ELA plus PTA group and 19.3 cm in the PTA-only group. There was a statistically significant difference in the presence of severe calcification with 27.1% and 9.1% in the ELA plus PTA and PTA-only group, respectively. The combination of ELA and PTA offers a 52% reduction in TLR (HR 0.48; 95% CI: 0.31-0.74). Similar to the PATENT study, ELA was performed using
the Turbo-Elite to create a pilot channel if needed and then followed with 4 quadrant passes with the Turbo-Tandem for maximal plaque debulking. Prior treatment for ISR in the target limb, increased lesion length, decreased reference vessel diameter, and treatment with PTA alone without ELA were associated with an increase in TLR occurrence with lesion length as the only significant interaction term. There were no reported stent fractures due to laser-stent interactions. IVUS studies have demonstrated a 35% reduction in stenosis and a 112% luminal area gain, 60% of which is attributed to vessel expansion with the Turbo-Tandem.
Table 14.1. ELA and IVUS Key Points | |
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CLINICAL PEARLS
