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Table 5 -2
Peripheral Arterial Disease and Angiography
Rutherford Classification Scheme of Peripheral Arterial
Disease
Grade Category Clinical Symptoms
0 0 Asymptomatic
I 1 Mild claudication
II 4 Ischemic rest pain
III 6 Major tissue loss
Table 5 -3
2 Moderate claudication
3 Severe claudication
5 Minor tissue loss
Fontaine Classification Scheme of Peripheral Arterial
Disease
Stage Clinical Symptoms
I Asymptomatic
IIa Mild claudication
IIb Moderate to severe claudication
III Rest pain
IV Ulcer or gangrene
Duplex ultrasound is useful to diagnose anatomic location and
degree of stenosis. Duplex is frequently used to evaluate infrainguinal
vessels and can provide a detailed image of stenosis and its location
within the leg. Renal, iliac, and infrapopliteal vessels can also be
imaged using duplex ultrasound, but this is often time consuming and
technologist dependent and may be not possible in some patients
(bowel gas can obscure imaging). Although it is simple, low cost, and
can provide detailed information, it is very technologist dependent.
Duplex ultrasound is recommended for routine surveillance after
femoral-popliteal or femoral-tibial/pedal bypass.
CTA of the extremities may be used to diagnose anatomic location and presence of significant stenosis in patients with lowerextremity, renal, upper-extremity, and carotid stenosis. CTA may be
considered as a substitute for MRA for those patients with contraindications to MRA (claustrophobia or presence of pacemaker/implantable
cardioverter defibrillator). It is noninvasive but exposes the patient to
both nephrotoxic iodinated contrast and radiation. Computed tomography (CT) imaging of the infrapopliteal vasculature is limited; heavy
calcification can obscure accurate interpretation of images.
MRA can provide detailed anatomic location and degree of arterial stenosis without the use of radiation or iodinated contrast. MRA is
performed with gadolinium administration, which is contraindicated
in patients with an estimated glomerular filtration rate (eGFR) <
60 ml/
min, secondary to the possibility of inducing nephrogenic systemic
fibrosis (NSF) and nephrogenic fibrosing dermopathy. MRA often overestimates stenosis severity as well.
Invasive vascular angiography is the “gold standard” for anatomic
imaging. With an arterial stenosis of indeterminate severity, measuring
a pressure gradient across the lesion with a pressure wire may clarify
clinical relevance. Assessment of trans-stenotic gradients at rest and
during the use of vasodilators to mimic exercise defines lesion significance. Intravascular ultrasound (IVUS) or optical coherence tomographic imaging assists in defining extent of disease and presence of
thrombus or calcium. Angiography is limited to a two-dimensional
(2D) image of a three-dimensional (3D) structure; in addition, it
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requires use of iodinated contrast, potentially detrimental in patients
at risk for contrast-induced nephropathy (CIN). To reduce the contrast
load and risk of CIN, a 50/50 mixture of contrast and saline may be
used for most peripheral angiography. If the use of iodinated contrast
is not clinically feasible, gadolinium may also be considered.
Due to the nonmoving aspect of the periphery (to negate movement, we recommend breath holding for imaging of the abdomen,
pelvis, and thorax) and the presence of overlying bone, DSA is the
recommended angiography. Standard cineangiography may also
provide useful and satisfactory information but often exposes the
patient to higher radiation.
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Peripheral Arterial Disease and Angiography 243
Endovascular Revascularization
Overview
Revascularization, either surgically or endovascularly, is reserved for
patients who are symptomatic with claudication, rest pain, or tissue
loss. Those presenting with claudication should undergo a trial of
pharmacotherapy or exercise therapy before being considered for
revascularization unless focal aortoiliac disease is suspected; for these
patients, endovascular revascularization can be considered first line.
Current guidelines recommend endovascular procedures for individuals with a vocational or lifestyle-limiting disability due to inter mittent
claudication, when clinical features suggest a reasonable likelihood
of symptomatic improvement with endovascular intervention and (1)
there has been an inadequate response to exercise or pharmacological therapy and/or (2) there is a very favorable risk-benefit ratio (e.g.,
focal aortoiliac occlusive disease). However, revascularization is no
substitute for optimal medical care to reduce the patient’s cardiovascular morbidity and mortality.
In patients with CLI, the need for revascularization is most evident.
In patients with ankle pressures <
<30 mm Hg, ulcerations will not heal without revascularization
because the metabolic requirements to heal a wound and prevent
infection are markedly elevated compared with simply keeping the
skin intact without ulceration. Without revascularization, loss of skin
integrity increases risk for infection, gangrene, and tissue loss.
It has been shown that restoration of blood flow to the
angiosome—that is, the vessel that directly perfuses the affected
region of the foot—is more effective than restoring flow more indirectly through the other infrapopliteal vessels. In some instances, it is
not possible to provide direct in-line flow; supplying collateral flow
from the peroneal artery or via the metatarsal arch may still be effective, but meticulous obser vation is critical for wound-healing success.
For patients with CLI, revascularization is an essential element for
limb salvage. The choice of whether to pursue an endovascular or
surgical approach depends on patient- and institution-specific features. In addition, the revascularization approach may depend on the
technique that will provide the most robust straight-line flow, incurring
the lowest risk for the patient. Patient comorbidities, anatomic features, presence of surgical targets and venous conduit, surgeon preference, and overall candidacy for safe performance and recovery from
surgery must all be considered in this decision.
Endovascular options are minimally invasive and, when compared with surgery, confer a lower risk of perioperative stress and
adverse cardiovascular events. Endovascular therapy has historically
been plagued by high restenosis rates; restenosis may have limited
clinical impact, however, if the vessel stays open long enough to
promote wound healing. In the Bypass versus Angioplasty in Severe
Ischemia of the Leg (BASIL) trial, there was no difference in amputationfree survival for up to 3 years among patients treated with an
40 mm Hg and toe pressures
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endovascular-first (as compared with a surgical-first) strategy at 3
years. Although surgical bypass has been long held as the “gold standard” treatment for patients with CLI, endovascular approaches may
emerge dominant in the coming decade. Currently, the choice of
revascularization approach remains patient and institution specific.
gical revascularization, including (1) reduced morbidity and mortality
(same-day or short-stay procedure), (2) ease of repeat procedure if
needed, (3) does not preclude future surgery in optimal outcomes,
(4) general anesthesia unnecessary, and (5) decreased infection rates.
A small arteriotomy, compared with the large wound from an open
surgical approach, confers a lower risk of infection and typically
permits return to normal activity within 24 to 48 hours after an uncomplicated procedure. This has led to widespread adoption of an
“endovascular-first” approach, depending on the anatomical substrate
and patient.
lar injury (vascular dissection, perforation, abrupt closure, or thrombosis), bleeding (access, retroperitoneal, and potentially gastrointestinal
from dual antiplatelet therapy), and exposure to radiation and nephrotoxic contrast. In addition, depending on the vascular bed, endovascular therapy has a high rate of restenosis and need for repeat
revascularization. The Trans-Atlantic Inter-Society Consensus (TASC
II) document provides anatomic and lesion guidance on which revascularization strategy may be most efficacious for a particular lesion.
In general, TASC A and B lesions are felt to be amenable to endovascular therapy, whereas more complex lesions such as long occlusions
(TASC C and D) might be better served with surgical revascularization.
This document, however, was generated before the advent of technologies that, in experienced hands, permit successful crossing and treatment of even the most complex lesions using advanced endovascular
techniques. Each vascular bed (Fig. 5-1), and the corresponding angio-
graphic techniques and data for revascularization, are reviewed in
detail in the following sections.
Peripheral Arterial Disease and Angiography
Endovascular therapy offers several distinct advantages over sur-
Endovascular therapy, however, is associated with risk for vascu-
Iliac Interventions
As noted earlier, the TASC classification was generated for aortoiliac
lesions (Fig. 5-2), with general recommendations for an endovascular
approach for TASC A and B lesions and a surgical approach for the
more complex TASC C and D lesions. This classification system provides a simple schema to categorize lesion complexity. The evolution
of endovascular technology and outcome data, however, has rendered
the guidelines less relevant to contemporar y clinical practice. In
fact, recent expert consensus documents from the Society for Cardiovascular Angiography and Interventions (SCAI) advocates for an
“endovascular-first” approach to most aortoiliac lesions, with surgery
recommended for endovascular failures. Current American College of
Cardiology/American Heart Association (ACC/AHA) guidelines recommend endovascular revascularization of aortoiliac disease when a
favorable risk-benefit ratio is present, depending on patient- and
lesion-specific determinants.
In contemporary practice, using advances in crossing catheters
that permit true lumen reentr y and/or lumen crossing, most iliac occlusions and complex lesions may be revascularized with endovascular
technique with high procedural success rates and excellent long-term
patency. Two recent meta-analyses confirmed that technical success
rates for aortoiliac intervention exceed 90%, and confer 4- to 5-year
primary patency rates of 60% to 86%, secondary patency rates of 80%
to 98%, and limb salvage rates of 98%.
Aortoiliac lesions are generally stented because stenting may
minimize vessel recoil and prevent abrupt occlusion. The current ACC/
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Exterior iliac artery
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Peripheral Arterial Disease and Angiography 245
Aorta
Middle sacral artery
Interior iliac artery
Iliolumbar artery
Lateral sacral artery
Superior gluteal artery
Common
femoral artery
Lateral femoral
circumflex artery
Ascending branch
Descending
branch
A
Superficial
circumflex
Profunda
femoris a.
Median femoral
circumflex artery
C. iliac a.
E. iliac a.
iliac a.
Obturator artery
Internal
pudendal artery
Femoral artery
Superficial
Deep
Aorta
I.
Iliac a.
Medial
femoral
circumflex
a.
Femoral a.
(superficial)
Deep circumflex
iliac artery
Inferior epigastric
artery
Inferior gluteal
artery
Iliac wing
Inguinal
ligament
C. femoral a.
Lateral
femoral
circumflex a.
B
Figure 5-1 Schematic diagram of the iliac (A) and femoral (B) ar terial
systems. a., Artery; C., common; E., ex terior.
AHA guideline supports primary stenting over provisional stenting of
the common and external iliac arteries with a class-I recommendation
(level of evidence B) and should likely be considered at the preferred
approach in complex iliac lesions.
Technical Details
Preprocedural noninvasive imaging is very helpful to develop a viable
access/treatment strategy for these lesions. The preferred site for
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Type-A lesions
• Unilateral or bilateral stenosis of CIA
• Unilateral or bilateral single short (≤3 cm) stenosis of EIA
Type-B lesions
• Short (≤3 cm) stenosis of infrarenal aorta
• Unilateral CIA occlusion
• Single or multiple stenosis totaling 3 to 10 cm involving the EIA, not
extending into the CFA
• Unilateral EIA occlusion not involving the origins of internal iliac or CFA
Peripheral Arterial Disease and Angiography
Type-C lesions
• Bilateral CIA occlusions
• Bilateral EIA stenosis 3 to 10 cm long, not extending into the CFA
• Unilateral EIA stenosis extending into the CFA
• Unilateral EIA occlusion that involves the origins of internal iliac and/or
CFA
• Heavily calcified unilateral EIA occlusion with or without involvement of
origins of internal iliac and/or CFA
Type-D lesions
• Infrarenal aortoiliac occlusion
• Diffuse disease involving the aorta and both iliac arteries requiring
treatment
• Diffuse multiple stenosis involving the unilateral CIA, EIA, and CFA
• Unilateral occlusions of both CIA and EIA
• Bilateral occlusions of EIA
• Iliac stenosis in patients with AAA requiring treatment and not amenable
to endograft placement or other lesions requiring open aortic or iliac
surgery
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Figure 5-2 Trans- Atlantic Inter-Society Consensus (TASC) classification of
aortoiliac lesions. AA A, Abdominal aortic aneurysm; CFA, common femoral
artery; CIA, common iliac artery; EIA, external iliac artery. (Reproduced with
permission from Norgren L, Hiatt WR, Dormandy JA, et al: Inter-society
consensus for the management of PAD [TASC II]. J Vasc Surg 45[suppl
S]:S5–S67, 2007.)
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Peripheral Arterial Disease and Angiography 247
arterial access depends on several factors, including (1) location of
the target lesion(s), (2) presence/absence of any lesions in the contralateral iliac artery, (3) need to treat infrainguinal vessels, (4) presence
of common femoral artery (CFA) disease, (5) angulation of the aortoiliac bifurcation, (6) severity of target lesion (occluded or not), and
(7) availability of radial or brachial artery access. When treating unilateral disease within the proximal iliac system (e.g., the common iliac
artery), ipsilateral access is preferable to permit direct delivery of
equipment. A contralateral approach is possible but will often be met
with challenges of establishing adequate coaxial support to deliver a
balloon/stent to a lesion that is proximal in the common iliac artery.
In contrast, if the target lesion is in the distal common or external
iliac arter y, contralateral access may be preferred, particularly in situations wherein external iliac disease extends distally to the common
femoral region, compromising ipsilateral sheath placement. If entire
reconstruction of the aortoiliac bifurcation is required, bilateral
femoral access permits simultaneous bilateral iliac stent placement
and a “kissing” balloon postdilatations. More than one access site (a
second site could be femoral or brachial/ radial) may be required to
approach chronic total occlusions (CTOs) (Fig. 5-3) in order to facilitate both antegrade and retrograde crossing and for better visualization of the extent of occlusion. Initial arterial access via the radial or
brachial artery is also an attractive option, but lesion location and
equipment length should be taken into account during treatment
planning.
Perform initial angiography of the iliac arteries in the contralateral oblique, using either a pigtail or omniflush catheter with or without
power injection (Table 5- 4). Use DSA and have patients hold their
breath to minimize artifact. Contralateral oblique imaging opens up
the common iliac and bifurcation into the external and internal iliac
Table 5 -4
Most Useful Angiographic Views for Different Vascular
Territories
Artery or Vascular Territory Angiographic View (Degrees)
Aortic arch 30 to 60 L AO (with slight cr anial
Brachiocephalic vessels (origin) 30 to 60 L AO
Subclavian AP, ipsilater al oblique with caudal
Vertebral origin AP, ipsilateral oblique with cranial
Carotid extracranial Lateral, AP, ipsilateral, 45 oblique
Renal arteries (origin) AP, 5 to 25 LAO
Mesenteric arteries (origin) Lateral or steep RAO
Iliac arter y Contralateral, 20 to 45 oblique
CFA, SFA, and PFA arteries Ipsilateral, 30 to 60 oblique
Femoropopliteal AP, ipsilateral, 20 to 30 oblique
Infrapopliteal trifurcation and runoff AP
AP, Anteroposterior; CFA, common femor al ar tery; LAO, lef t anterior oblique; PFA,
profunda femoral artery; RAO, right anterior oblique; SFA, superficial femoral arter y.
angulation)
angulation
angulation
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Peripheral Arterial Disease and Angiography
A
B
Figure 5-3 A, Totally occluded right iliac arter y. B, Right iliac arter y af ter
successful angioplasty and stenting.
arteries. In the setting of iliac occlusions, the pigtail should be high
enough in the aorta (L4 to L5) to opacify all of the lumbar vessels that
often provide collaterals through various branches. The imaging
should be long enough to determine whether the occlusion involves
the CFA and/or lateral circumflex iliac vessel. If the CFA is not involved
and the lateral circumflex or another side branch is patent, ipsilateral
access can often be obtained under roadmap function with use of
these side branches for wiring to provide enough support to place a
sheath. This then permits a retrograde approach that affords greater
support for advancement of interventional equipment.
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Peripheral Arterial Disease and Angiography 249
Stent Types
Two types of stents are available for endovascular interventions.
Balloon-expandable stents offer greater precision of placement and
superior radial strength; they are therefore better suited for calcified
vessels but may be less desirable in segments that involve excessive
tortuosity. They are often used to treat common iliac lesions and with
aortoiliac kissing stents.
Self-expanding stents, characterized by their flexibility and ability
to conform to varying vessel diameters, are the optimal choice for
vessel size mismatch across the lesion. These stents have much less
radial strength compared with balloon-expandable stents, but in vascular segments inherently prone to flexion or extrinsic compression
or in tortuous vessels, the superior flexibility of self-expanding stents
may outweigh the compromise in terms of radial strength. Overall, no
clinically available stent has been demonstrated as superior to any
other in the aortoiliac distribution. There has been debate on whether
stent architecture or composition (i.e., nitinol vs. stainless steel) has
any effect on restenosis rates. However, the CTP to predict Response
to recanalization in Ischemic Stroke Project (CRISP) trial failed to
show any differences in clinical outcomes at 1 year between nitinol
(S.M.A.R.T. Nitinol Stent System; Cordis Corporation, Miami Lakes, FL)
and stainless steel (Wallstent, Boston Scientific Corp., Watertown, MA)
iliac artery self-expanding stents.
Polytetrafluoroethylene (PTFE)-covered stents are also available
in balloon-expandable and self-expanding formats. Whereas covered
stents were previously reserved for the treatment of iliac aneurysms,
arteriovenous (AV) fistulae, and iatrogenic perforations, recent studies
suggest that covered stents may be used for primary treatment of stenotic lesions as well. The comparison of covered versus bare expandable stents (Covered versus Balloon Expandable Stent Trial [COBEST])
for the treatment of aortoiliac occlusive disease trial demonstrated a
significantly lower restenosis rate with the use of the covered stent
when compared with bare-metal stents. In a subgroup analysis of these
data, the outcomes from treatment of TASC C and D lesions with
covered stents were superior to those treated with bare-metal stents,
although in part this finding might be attributed to operator confidence in providing higher-pressure balloon postdilatation following
covered-stent placement, resulting in greater luminal gain. One disadvantage of expanded PTFE (ePTFE)-covered stents, however, is the
slightly reduced deliverability due to the scaffold stiffness and the
need for larger sheaths, although this is changing and 6-F compatible
covered stents are available. PTFE-covered stents also may occlude
any subtended side braches, including major vessels, such as the
internal iliac artery and/or major collaterals, potentially obliterating
collateral flow in the event of stent occlusion.
Unfractionated heparin (UFH) is most commonly used for intraprocedural anticoagulation during aortoiliac intervention and offers
the benefit of acute reversibility (using protatmine sulfate) in the event
of serious adverse bleeding events, such as iliac perforation. Direct
thrombin inhibitors, such as bivalirudin, have been used for peripheral
intervention but are more costly and are irreversible.
After selection of the access site and placement of a sheath (4 to
8 F or larger), wiring techniques are similar to other interventional
procedures. Be familiar with equipment compatibility among stents,
balloons, crossing catheters, and covered stents, because they may
use 0.035-, 0.018-, and 0.014-inch systems. For the greatest degree of
support and trackability, especially if tortuosity or calcification is
encountered, 0.035-inch wires provide the best option. Although small
profile systems (stents and balloons) (4- to 6-F sheaths) are available
with 0.018- or 0.014-inch systems for most iliac stents, in cases where
perforation is possible, it is recommended that 7- or 8-F sheaths be
used to permit the delivery of covered stents. These larger sheaths are
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often also required for the delivery of specialized crossing catheter
and/or reentry catheters that can permit the success rate of crossing
even the most complex lesion to increase to more than 90%.
Peripheral Arterial Disease and Angiography
Complications of Iliac
Endovascular Intervention
Although major complications during iliac interventional procedures
are rare, the interventional team must always be vigilant for evidence
of contrast reaction, arterial perforation, dissection, embolization, and
access site complications. The two most dangerous complications are
distal embolization (DE) and iliac perforation. DE has been reported
to occur between 0.4% and 9% and may be treated with mechanical
or rheolytic thrombectomy, balloon inflation, stent placement, and,
occasionally, surgical embolectomy.
The most feared complication is iliac artery perforation or rupture,
the incidence of which ranges from 0.5% to 3%. With increasing lesion
complexity comes an increasing risk for iliac perforation and rupture.
Monitor patients carefully during any balloon inflation for pain, especially during postdilatation of stents because this indicates stretching
of the adventia and impending rupture. Given the free retroperitoneal
space, iliac rupture is potentially fatal, and it is imperative that the
operator manage the complete armamentarium of covered stents
and possibly aortic occlusion balloons on standby for any iliac
intervention.
Perforation can be caused by guidewires, reentry devices, or
crossing catheters and can occur during balloon/stent deployment.
Any acute low back or abdominal pain, especially during balloon
inflation, may be a sign of impending rupture. If there is a concern of
rupture, carefully observe the arterial pressure waveform. If a precipitous drop occurs, immediately perform balloon inflation proximal to
the possible site of rupture to tamponade the bleeding. Once tamponade is attained, place the covered stents. Rarely does one have time
to proceed with open surgical repair in these patients, but if the patient
is stable, this may be also considered.
Femoropopliteal Interventions
Compared with intervention in the aortoiliac distribution, the outcomes following endovascular treatment of the femoropopliteal
segment have much higher rates of restenosis. There are several pathophysiologic differences that explain this discrepancy in outcomes:
(1) Femoropopliteal atherosclerosis is often more diffuse, heavily calcified, or totally occluded than are lesions in the iliac segments; (2)
the femoropopliteal segment is uniquely exposed to major extrinsic
forces, including repetitive flexion, torsion, and compression along its
length, resulting in chronic, recurrent opportunities for vascular injury
following intervention; and (3) the engineering challenge is great for
creating a scaffold or platform that can withstand the biologic nature
and physical forces unique to the femoropopliteal segment.
In the TASC II document (Box 5-2), the complexity of femoropopliteal disease is categorized as A, B, C, or D, reflecting severity on the
basis of lesion length, presence of total occlusion, and territory
involved. Although more severe TASC C and D lesions have historically
been considered best amenable to surgical revascularization, recent
advances in endovascular technique and device technology have
drastically improved acute procedural success rates with endovascular treatment. Despite these advances, however, the long-term patency
following endovascular therapy remains suboptimal. Appropriate
treatment decisions for disease in the femoropopliteal territory require
careful consideration of patient, lesion, and operator-specific factors.
Patient factors include age, systemic comorbidity, availability of
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Peripheral Arterial Disease and Angiography 251
Box 5 -2 Trans-Atlantic Inter-Society Consensus
Classification of Femoropopliteal Lesions
Type-A Femoropopliteal Lesions
• Single stenosis <10 cm in leng th
• Single occlusion <5 cm in length
Type-B Femoropopliteal Lesions
• Multiple lesions (stenosis or occlusions), each <5 cm
• Single stenosis or occlusion, < 15 cm, not involving the infrageniculate
popliteal ar tery
• Single or multiple lesions in the absence of continuous tibial vessels to
improve inflow for a distal bypass
• Heavily calcified occlusion <5 cm in leng th
• Single popliteal stenosis
Type-C Femoropopliteal Lesions
• Multiple stenosis or occlusions totaling >15 cm with or without heavy
calcification
• Recurrent stenosis or occlusions that need treatment after two
endovascular interventions
Type-D Femoropopliteal Lesions
• Chronic total occlusions of CFA or SFA (>20 cm, involving the popliteal
artery)
• Chronic total occlusion of popliteal artery and proximal trifurcation vessels
CFA, Common femor al ar tery; SFA, superficial femo ral arter y.
Norgren L, Hiat t WR, Dormandy JA, et al: Inter-society cons ensus for the
management of per ipheral arterial disease (TASC II). J Vasc Surg 45[suppl
S]:S5– S67, 2007.
endogenous conduit, and whether disease is associated with CLI
versus claudication. Important anatomic features include extent of
disease, involvement of points of flexion less amenable to stent treatment and historically preserved for bypass anastomosis (common
femoral and popliteal arteries), and presence of calcification. Operator
experience with advanced techniques may also play an important role
in procedural outcomes and durability. Recently, publications have
highlighted the appropriateness of femoropopliteal interventions for
various disease subsets for each endovascular therapy available.
As noted, interventional therapy of the femoropopliteal segment
has historically been hampered by high rates of restenosis. Balloon
angioplasty has been associated with a 63% rate of restenosis at 1 year.
Balloon-expandable stents, subject to extrinsic compression and
chronic deformation, are not mechanically suitable here and should
not be used. More recently, nitinol self-expanding stents, with shape
memory and flexibility, have enjoyed greater success in the femoropopliteal segment.
As demonstrated in the coronary arteries, locally delivered restenotic therapy also reduces restenosis following treatment of the femoropopliteal segment. In the Zilver PTX trial, 2-year primary patency was
83.4% following paclitaxel-eluting stent deployment compared with
64.1% following bare-metal stent use.
Stent-graft systems (ePTFE covered self-expanding stents) may
have utility in the treatment of stenosis, iatrogenic perforation, and
aneurysmal disease in the femoropopliteal segment. Edge restenosis
within the graft may portend future graft thrombosis. Although the
Viabahn stent graft is FDA approved for the treatment of superficial
femoral artery (SFA) lesions, comparative studies with bare-metal
stents in complex TASC C and D have not shown an advantage to
Viabahn use over nitinol stents at 3 years.
Novel technologies, including atherectomy, cryoplasty, cutting
balloon, and laser atherotomy, may offer niche-specific advantages to
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