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4 The Angiographic Suite: Setup andErgonomics
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Basic Tools andTerminology
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forEndovascular Interventions
PeterJamieson andAbdelKaderAllouni
5
Basic Tools
There is a wealth of equipment that can be used for endovascular procedures, a list that only grows with new innovations
and new medical devices companies. As an endovascular
operator, it is important to be familiar with a wide range of
equipment, though becoming skilled with every device on
the market is unachievable. What follows is an overview of
the groups of devices available, their characteristics and
some examples of each category, though one should note that
other devices are available from alternative manufacturers,
with similar features and applications.
Needles
The vast majority of endovascular procedures begin with a
needle inserted into a vessel under ultrasound guidance.
Needles vary in length and diameter, with a general rule that
shorter and wider needles are stiffer, whereas longer and
thinner needles are more exible and can bend in the tissues,
making it more difcult to accurately hit a deep target.
Most vascular access needles are one-piece, hollow, bevelled needles, permitting passage of a guidewire into the vessel immediately following vessel single wall puncture,
though the operator should be careful to ensure good, pulsatile ow from the needle hub to ensure the bevel is not across
the vessel wall, risking dissection when the wire is introduced. A small notch or marker on the hub usually corresponds to the side the bevel faces.
Some needles are lled with an inner trocar that provides
extra rigidity and prevents the entrainment of air. In the past
these were used for double-wall vessel puncture (front and
back wall), though they are now rarely used for vessel access
and are more often used for non-vascular interventional
procedures.
Vascular access is gained through use of the Seldinger
technique, whereby the vessel is punctured with a hollow
needle, a guidewire is inserted through the needle into the
vessel, the needle is removed and a sheath with dilator is
inserted over the guidewire. Finally, removal of the dilator
(and often the guidewire) leaves just the sheath in situ. More
information on guidewires and sheaths can be found below.
Needle outer diameter is measured in gauge (G)—the
lower the gauge, the larger the needle. 19 G approximates to
0.038 of an inch, 1mm or 3 French.
– 25 G (orange) needle for supercial local anaesthetic
injection
– 23 G (blue) or 21 G (green) needle for deeper local anaes-
thetic injection
– 22G (micro-puncture) needle permits a 0.018 wire. This
is more frequently used for access to small arteries such
as the radial or infra-popliteal arteries, but can be used for
any vascular access. A dilator/sheath can be placed over
the 0.018 wire, or it can be exchanged through a 4 Fr dila-
tor for a 0.035 wire.
– 18–19 G needle permits a 0.035 wire (as for standard
sheath J-wires)
Dilators
Dilators are stiff plastic tubes with tapered tips that can be
advanced over a guidewire. They function to widen the vessel wall and the overlying soft tissues. Serial dilatation with
increasingly wide dilators can upsize even tiny micropuncture holes to a width large enough to accommodate a
large-bore access sheath for aortic stent-graft placement.
P. Jamieson · A. K. Allouni (*)
Department of Interventional Radiology, University Hospitals of
North Midlands NHS Trust, Stoke-on-Trent, UK
e-mail: peter.jamieson@uhnm.nhs.uk
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2024
G. Geroulakos et al. (eds.), Mastering Endovascular Techniques, https://doi.org/10.1007/978-3-031-42735-0_5
33
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P. Jamieson and A. K. Allouni
Sheaths
Sheaths are haemostatic conduits that are generally stationary within the access site of the vessel and prevent trauma
caused by repeated manipulation of endovascular catheters
or other devices and maintain haemostasis during catheter
exchanges. Sheaths are composed of a thin layer of stiff hollow plastic. They are often placed at the start of endovascular
procedures once access to the vessel has been gained by a
needle and secured with a wire. They are inserted over a dilator, over a wire, and the dilator is removed once the sheath is
in position.
At the external end of a sheath is a one-way valve, which
prevents egress of blood but allows the passage of wires and
catheters. From the hub extends a side-arm, on which there is
a 3-way tap to allow ushing.
Sheaths are typically labelled in French (Fr) size, which
represents their inner diameter (i.e. the size of device they
accommodate). For example, a 4 Fr sheath accommodates
a 4 Fr catheter. The external diameter of a sheath is normally 1.5–2 Fr larger than its internal diameter. 3
Fr=1mm.
Sheaths are available in diameters from 4–30 Fr. The
sheath should be selected in advance based on the intentions of the procedure, considering the target position of
the sheath tip and the size of the devices likely required
during the procedure. Standard sheaths are 10–12 cm in
length, but longer sheaths, up to 110 cm in length, are
available, maintaining secure access closer to the site of
therapy, particularly useful in contralateral femoral or arm
access, visceral or carotid interventions or infra-popliteal
interventions.
Braided sheaths (e.g. Destination Guiding Sheath,
Terumo) incorporate stiff rings or coils, often stainless steel,
that provide increased resistance to kinking or “ovalisation”
when compared with conventional sheaths, and should be
considered when the sheath is to cross tight corners, such as
the aortic bifurcation. Sheaths are also available with shaped
rather than conventional straight tips, such as the renal double curve (RDC) sheath, that intends to support access to the
visceral vessels.
Guidewires
Guidewires are used to navigate vessels to reach a target
lesion or vessel segment and to support the passage of a catheter or device to the target to allow treatment. They are constructed of a stiff inner “mandrel” core wrapped in a ne
wire or coated with a hydrophilic coating that makes them
more manoeuvrable when wet.
The physical properties of wires are interrelated and are
generally characterised by their pushability, trackability,
steerability, torque, supportability and opacity.
– Pushability is the amount of force needed to advance the
wire, which is related to both the axial stiffness of the
wire and the degree of surface friction.
– Trackability is the ability of the wire to follow the tip
along a vessel, related to exibility and surface coating.
– Steerability is the capacity of the wire tip to be navigate
vessels, intimately related to pushability and torque.
Torque is translation of a turn of the wire by the operator
into rotational movement at the tip of the wire.
– Supportability is the capacity of the wire to support the
passage of a device and its successful deployment. Stiffer
wires provide greater support for devices, but have a
greater propensity to cause damage to the vessel and are
less useful for vessel navigation.
– Opacity is the level of visibility of a wire under uoro-
scopic imaging—this can be enhanced with the inclusion
of platinum or gold, often most critical at the wire tip.
Most wires are composed of a stiff inner core which is
wrapped by a ne wire or coated with a polymer. Steel core
wires are stiff, whereas the inclusion of Nitinol in a wire
increases exibility and allows the wire to spring back into
shape after navigating a tortuous vessel segment.
Guide wires usually have a oppy tip, created by the
tapering of the stiff inner core, that enables navigation and
prevents vessel damage, with a stiff body to enable pushability and “torquability”.
Some wires are coated with a polymer, such as silicone or
polytetrauoroethylene (PTFE), to reduce friction. In a uid
environment, hydrophilic coatings reduce friction for easier
movement in small, stenosed or tortuous vessels. Hydrophilic
wires are slippery when wet and sticky when dry, so are more
difcult to handle. Manipulation of these wires is helped by
using a torque device (see below).
Radiopaque markers are commonly used to improve the
visibility of wires on uoroscopic X-ray imaging. These are
often precious metals, such as gold marker bands or the
inclusion of a platinum wire.
Wires can be spun between the thumb and index nger (or
with a torque device) to direct the angled tip in the desired
direction so that branches can be engaged, or avoided.
Continuously spinning the wire while advancing it within a
vessel prevents the wire from catching on to small branches
or atherosclerotic plaques. When advancing or removing
catheters over a wire, the back-end of the wire should be
xed to prevent inadvertent wire advancement or loss of
position.
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Wire Shapes andSizes
The tips of the wires come in various congurations to help
navigate, such as straight or differing degrees of curves,
including a “J” curve. Some tips can also be shaped by the
operator using a hard edge.
Wire diameters are measured in thousandths of an inch,
usually between 0.014 and 0.038 inches, referred to colloquially as ‘014’, ‘018’ and ‘035’. Thinner wires, such as 014
and 018, are generally used in smaller vessels and they allow
the use of smaller prole catheters and balloons.
Lengths are measured in centimetres, ranging from 80 to
450cm.
Length of wires varies, with a standard wire being around
145 cm long, but exchange wire length should allow for
catheter exchange, so must be at least twice the length of the
catheter or device.
Wire Types
Access Wires—simple short wires used for access and then
exchanged.
Navigation/Manoeuvring Wires—exible wires, often
hydrophilic, with shaped tips that can be steered to sub-select
vessels.
Support Wires—stiff, retain position and provide stability
for catheter exchanges and for inating balloons or deploying devices such as stents, whilst maintaining access.
Exchange wires are usually longer, often 260–300cm.
Graduated Wires—increase in stiffness from proximal to
distal, e.g. TAD/Jindo which transitions from a 0.018 diameter oppy tip to an 0.035 rigid shaft, useful in renal or mesenteric stenting.
Weighted tip wires***
Wire Problems
Shearing—Coated wires should not be passed through
access needles because of the risk of shearing off the coating
within the vessel.
Kinking—If a dilator or sheath is advanced at too acute an
angle or over a wire with insufcient tension then a bend or
kink can develop in a non-hydrophilic wire. This makes
passing a catheter over the wire difcult. Applying sufcient
retraction on the wire as the dilator or sheath is advanced,
and matching the puncture angle when advancing sheaths are
essential to prevent this difculty. When this occurs, the wire
should be exchanged.
Common Wire Examples
Wire Type Examples Indications Notes
Standard/access wires J-wire (e.g. Rosen wire,
Moderate stiffness Amplatz Stiff (Boston) Exchanges Available in up to 3m length. Floppy tip
Very stiff Amplatz Superstiff or
Extra stiff Lunderquist (Cook),
Steerable—hydrophilic Glidewire (Terumo),
Shapeable tip,
microcatheter support/
exchange
Weighted tip Approach CTO Microwire
Cook Medical)
Bentson wire (Cook
Medical)
Ultrastiff (Boston)
Meier (Boston)
Roadrunner (Merit),
Zipwire (Boston)
V14/V18 (Boston
Scientic), Fathom (***)
(Cook Medical)
Standard wires: These are soft wires that can be used for
initial access, exchanges and device delivery. ‘J’
wires—3mm, 5mm or 15 mmJ-shaped tip. The tip shape
reduces the risk of cannulating small collaterals or causing
intimal damage when advanced. Bentson wire is a straight,
oppy-tipped standard wire that is useful for the above indi-
Seldinger access, device delivery or
exchange. Bentson wires can cross
moderate stenoses or push coils
Difcult access, exchanges, device
delivery
Thoracic or abdominal aorta stent graft
delivery
Navigation, traversing disease Stiff Glidewire (Terumo) combines support and
Working/traversing wire in 0.014 or
0.018 systems
Traversing chronic total occlusions Provided in different weights of tip, measured
J wires have 3, 5 or 15mmJ-shaped tips.
Benston wires have a straight, oppy
atraumatic tip
Expensive. Great stability and very visible tip
steerability. Glidewires (Terumo) are available
in 0.018 and 0.035 sizes
For when smaller calibre devices are required
in grams
cations, but can also be used for crossing moderate stenoses
or pushing coils.
Moderate stiffness: e.g. Amplatz (Boston) Stiff, com-
monly used for difcult access and exchanges.
Very stiff: e.g. Amplatz (Boston) Superstiff or Ultrastiff,
commonly used for device delivery.
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P. Jamieson and A. K. Allouni
Extra stiff: e.g. Lunderquist (Cook) and Meier (Boston)
Wires, commonly used for thoracic or abdominal aortic
endograft delivery.
Steerable wires: Glidewire (Terumo)/Roadrunner (Merit)/
Zip (Boston) for crossing tight stenosis or tortuous vessels.
Stiff Glidewire (Terumo) combines support and steerability.
– V18 control wire (Boston)—has a radio-opaque, shape-
able, hydrophilic tip to increase manoeuvrability and per-
mit vessel selection, but a stiff main shaft to improve
pushability and facilitate catheter exchange. Typically
used in smaller vessels such as the tibial arteries.
Catheters
Guide Catheters
Catheters are exible tubes that are typically inserted over a
guidewire through a sheath. Their shape facilitates cannulation of vessels and they can be used to inject contrast media
to allow for the acquisition of digital subtraction angiograms
(DSA), or to inject medications, such as thrombolytic agents.
Catheters come in a variety of shapes and sizes to suit different anatomical structures.
The main practical distinctions between catheters are
whether they are end- or side-hole, hydrophilic or nonhydrophilic and the shape of their tip. Their propensity to
retain their shape and their “torquability” are characteristics
of the material they are made of and their thickness. For
example, Teon catheters have a low co-efcient of friction
but are at higher risk of kinking and polyethylene catheters
are softer and more exible, yet retain torsional rigidity and
therefore torque. Catheters are visible under uoroscopy as
they are impregnated with barium sulphate.
Fr sizes in catheters refer to their outer diameter, as
opposed to sheaths, where the size refers to inner diameter.
Most modern catheters are 5 Fr or smaller. 5 Fr catheters
tend to have the same size of lumen as 4 Fr catheters but with
thicker walls, giving them greater stiffness, torquability and
stability, but necessitating a large access hole. Higher ow
rates can be achieved through shorter, wider catheters, and
thicker catheters with narrower lumens are less likely to
burst. Catheters typically burst at the hub, but a kink increases
the risk of the catheter bursting inside the patient.
In general, catheters should be advanced over a wire; otherwise, their tips can scrape along the vessel wall and cause
trauma.
Microcatheter
More slender than traditional catheters, 1–8–3 Fr in diameter. They are normally used co-axially through larger 4 or 5
Fr catheters, typically over 0.010–0.018 guidewires, though
some microcatheters can be advanced without a wire in certain scenarios. Microcatheters are more exible and thus can
gain access to smaller and more tortuous vessels and are
commonly used within visceral and cerebral vessels for procedures such as embolisation. Support catheters are of similar calibre, but are stiffer, with utility in the below-knee
arteries where they enhance the operator’s ability to cross
lesions with small guidewires.
Common Catheter Examples
Catheter type Examples Indications Notes
Forward-facing, angled tip MPA, Berenstein (I or II), Van
Shee, vertebral
Non-selective Pigtail Angiography/venography, including by
Wall-bracing Cobra Crossing aortic bifurcation, visceral
Reverse-angled Simmons (I or II), SOS Omni,
sidewinder, rim, USC
Hydrophilic Glidecath or Glidecobra
(Terumo)
Microcatheter Progreat Microcatheter
(Terumo), Direxion (Boston
Scientic)
General vessel navigation/cannulation,
including arch vessels
injection pump
vessel cannulation
Visceral vessel cannulation, aortic arch
vessel cannulation, crossing aortic
bifurcation
When struggling to track a nonhydrophilic catheter
Selective vessel cannulation, typically
for embolisation (coils, particles,
microvascular plugs)
Vary in length and severity of
angulation
Pigtail-shaped tip with multiples
side-holes
The shape helps anchor the
catheter by increasing apposition
to the vessel wall
Need forming once inside the
patient, provide stability access to
visceral vessels
Some stability is sacriced in
return for increased trackability
Accommodate an 0.014 or 0.018
wire. Fit co-axially through a 4
Fr or 5 Fr catheter. 1.8–3 Fr in
diameter
5 Basic Tools andTerminology forEndovascular Interventions
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Catheter type Examples Indications Notes
Support microcatheter CXI Support Catheter (Cook
Medical)
Thrombolysis
Traversing occlusions or stenoses in
small vessels
Often t co-axially through a 4 Fr
catheter over an 0.014 or 0.018
wire. Provide support for lesion
traversing in small arteries
37
Torque Devices
Small barrel shaped devices that provide a secure grip point
for wires that are hard to grip and rotate (hydrophilic or
monolament). The wire is passed through these devices,
and they grasp the wire either using a spring mechanism or
by tightening a micro chuck.
Taps/Hubs/Connectors
Flow switch—a short, linear device with male and female
Luer lock ends that can be attached to syringes and catheters,
through which a wire can be passed. There is a central switch
that can be closed, preventing the passage of wires and the
egress of blood.
Tuohy–Bohrst—a Y-shaped connected with a luer lock
connector on one end and a haemostatic valve and tap for
ushing on the other end. The haemostatic valve can be
tightened to differing degrees depending on the width of the
wire or catheter within it. A ow switch is often attached to
the tap of the Tuohy–Bohrst. This device helps when using a
smaller wire or catheter within a larger catheter in which the
entire lumen is not occupied and would normally allow blood
ow around the inner wire, for example, a 0.018 wire or a
microcatheter within a 4 Fr catheter. This maintains haemostasis at the back of the catheter and allows ushing, preventing the clot formation that may otherwise occur.
Removable haemostatic valve (e.g. Cook Medical). These
enable the conversion of a guide catheter to a sheath and are
also useful for clot aspiration from a catheter. Destination
Guide Sheaths (Terumo) include a removable valve.
Snares
Snares are devices with loops at their distal end that can be
pulled tight to capture a wire, catheter or other device. The
most common snares are gooseneck snares, a single loop
snare, but other shapes such as the “polyhedral” snares exist
and they can improve the operator’s chance of capturing
small objects. Snares are commonly used to capture guide-
wires, allowing the reversal of access (e.g. from retrograde to
antegrade), facilitating alternative approaches to the navigation of tight bends or crossing of resistant occlusions. Snares
can also be used to retrieve migrated foreign bodies, such as
coils or guidewires, or to strip brin sheaths from longstanding central venous catheters.
Balloons
Angioplasty Balloons
Dilatation balloons, most commonly used for angioplasty,
but also with utility in the gastrointestinal and genitourinary
systems, are a form of catheter with a non-compliant or
semi-compliant plastic balloon at its distal end. Noncompliant balloons do not conform readily to the vessel contour and therefore exert more pressure on a lesion than on
normal vessel wall. A radio-opaque marker indicates each
end of the “working length” of the balloon, though the operator should be aware that a short tapering section of balloon
will project beyond the markers at both ends.
Balloons are labelled by their diameter at nominal pressure and by their length when fully inated. They should be
selected based on the target vessel diameter and lesion
length, with consideration of the pressure likely to be
required for successful vessel treatment (for example, venous
stenoses may require treatment with a high pressure
balloon).
Balloons are available on long or short delivery systems,
which describe the length of the catheter delivering the balloon. Short delivery systems, typically 75–80cm in length,
are most commonly used, but longer systems, such as those
135 cm in length may be required for contralateral angioplasty, or when access is obtained from the arm.
Balloons are more frequently “over the wire”, similar to a
conventional catheter, where the lumen of the catheter runs
along its entire length, but alternatively can be “monorail” or
“rapid exchange”, whereby the lumen (and therefore the
wire) exit the balloon part way along its shaft, permitting
these rapid exchange balloons to be used over shorted wires
than for a conventional balloon.
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P. Jamieson and A. K. Allouni
Further information provided includes the thickness of
the wire accommodated by the balloon and the size of sheath
required to insert them. Smaller prole balloons that can be
inserted through a 4 Fr sheath often require an “014” or
“018” exchange wire; balloons that can track over an “035”
wire tend to require a 5 Fr sheath or larger.
Balloon packaging will specify a nominal pressure in
atmospheres (ATM), which represents the pressure at which
the balloon will form its labelled diameter, but balloons can
be further inated up to a maximum “burst” pressure to treat
resistant stenoses, at which point the balloon will be of a
larger diameter, typically 5–10% greater than its nominal
diameter. The burst pressure is the maximum pressure the
balloon can withstand without rupturing.
Balloons should be inated with dilute contrast to permit
visualisation under uoroscopy, with care to keep air present
within the balloon minimal in case of balloon rupture and
distal embolisation. Balloons inate from outside-in.
A few special case balloons exist for use in certain
scenarios:
– High pressure balloons have higher burst pressures and
can be used to treat resistant stenoses, such as venous ste-
noses occurring in high ow arterio-venous stulae. They
tend to require a larger access sheath for delivery.
– Cutting balloons have multiple thin longitudinal blades
along the length of the balloon that score the intima when
the balloon is inated. They should be inated multiple
times within the lesion, rotated slightly between each
ination to score the intima in multiple places, before fur-
ther angioplasty with a conventional balloon. Care must
be taken when handling these balloons to avoid injury to
the operator.
– Drug-eluting balloons are coated with a medication that
prevents smooth muscle hyperplasia at the site of angio-
plasty, an example of which is the Ranger Drug-Coated
Balloon (Boston Scientic), which is coated in Paclitaxel.
Drug-coated balloons have been shown to reduce the risk
of re-stenosis at the site of angioplasty, though, at the time
of writing, their use is limited in many centres, due to
previous data showing an increase in mortality following
their use.
Compliant Balloons
Compliant balloons are used less frequently, but have particular utility when vessel occlusion is required, for example,
a Le Maitre balloon, which can be used to occlude the aorta
to prevent bleeding in pelvic surgery or traumatic scenarios.
Compliant balloons are also used to mould stent grafts to the
surrounding vessel wall, most commonly during endovascular aneurysm repairs.
Ination Devices
Ination devices are lled with dilute contrast and used to
inate angioplasty balloons to a pressure displayed on a
gauge. Through use of a corkscrew method of ination and a
quick-release mechanism, they allow the generation of far
greater ination pressures than could otherwise be managed
with human strength and a conventional syringe.
Stents
Stents function by exerting outward radial force and, unlike
balloons, remain in place once the procedure has concluded,
maintaining this radial force. Stents used in vascular
procedures are metallic (plastic stents are sometimes used in
biliary or urological procedures). There are two forms of
bare metal stent, described below.
Self-expanding stents are made of nitinol, a nickel–titanium alloy that has memory of their intended shape and will
attempt to form this when no longer constrained. In their
packaging, they are contained by a plastic delivery sheath
that allows the device to remain low prole for insertion
through access sheaths and positioning in the correct location. A release mechanism exposes the stent and allows it to
expand to its former diameter, continuing to exert outward
radial force wherever this nominal diameter cannot be
reached.
Self-expanding stents are more exible and conform
better to tortuous anatomy than balloon-expandable stents.
They are simple to deploy but tend to shorten as they are
deployed.
Balloon-expandable stents are loaded onto a balloon catheter—the stent is deployed by dilation of the balloon, taking
the stent to its nominal diameter, where it exerts higher radial
force than a self-expanding stent does. They can be deployed
more accurately than self-expanding and are therefore useful
for iliac origin disease. Balloon-expandable stents are nonconformable and will straighten the anatomy they are
deployed into. They can be crushed or fracture if placed in an
area where they are forced to ex, such as close to the groin,
and should not be used in these scenarios. It should also be
noted that balloon-expandable stents are not covered prior to
deployment like self-expanding stents are, so there is risk of
the stent becoming dislodged if being advanced through a
tight stenosis. This can be avoided by “unsheathing” the
stent within the stenosis.
Covered stents (stent grafts)—Stents can also be covered
with material, typically a synthetic polymer or fabric. Once
again, they can be self-expanding or balloon-mounted.
Covered stents can be used in scenarios where vessel relining is required, such as treatment of a focal bleeding point
or aneurysm exclusion, including EVAR. Due to the pres-
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ence of fabric, as well as metallic stents, they are larger prole than bare stents and require larger delivery sheaths.
As with balloons, stents are also available in drug-eluting
forms, such as the Eluvia drug-eluting stent that utilises
paclitaxel, with some studies showing increased long-term
popliteal segment. As for their balloon counterparts, historical controversies regarding potential long term mortality
risks cast a shadow over their use, dissuading many practitioners from employing them in vivo, and therefore they are
mostly limited to coronary use.
patency when used in atherosclerotic disease of the femoro-
Type Examples Indications Notes
Bare metal,
self-expanding
Bare metal, selfexpanding, exible
Bare metal,
balloon-expandable
Covered,
self-expanding
Covered,
balloon-expandable
Thoracic aorta
covered stent graft
Abdominal aorta
covered stent graft
Drug-eluting stent Eluvia (Boston Scientic) Resistant femoropopliteal
Smart (Cordis), Luminexx
(Bard)
Supera (Abbott), Biomimic
(***)
Palmaz Iliac vessels, visceral
Viabahn (***) Exclusion of bleeding,
VBX (***) Exclusion of bleeding,
TAG Conformable (Gore),
Valiant (Medtronic)
Endurant (Medtronic),
Excluder (Gore), *** (Cordis)
Standard stent placement,
e.g. iliac
Stenting in Length dependent on vessel preparation/deployment
arteries
aneurysms, stulae
aneurysms, stulae
Thoracic aortic aneurysm
or dissection
Thoracic aortic, common
iliac aneurysms
lesions
More suitable for tortuous vessels than
balloon-expandable
Better suited to straight anatomy. Can be positioned
more accurately than self-expanding (e.g. close to
bifurcation)
Typically a bifurcated system deployed from both groins
Still not widely used due to concerns regarding
potentially increased all-cause mortality
Re-entry Devices
Re-entry devices are catheters that can aid the return into the
lumen of an artery from the sub-intimal space. Wires and
catheters can sometimes breach the intima of a vessel when
attempts are made to cross occlusions or tight stenoses.
Though this sometimes takes place inadvertently, while the
operator is attempting an intraluminal approach, it is a legitimate way of crossing occlusions and the operator may perform this intentionally.
However, in order to angioplasty or stent the lesion, the
operator must regain access to the lumen of the artery
beyond the occlusion. Often this is straightforward with a
standard hydrophilic wire (e.g. Terumo glide wire) and
catheter (e.g. Berenstein), but on occasion this can prove
tricky. Re-entry devices are typically comprised of a sharp
needle towards the end of a catheter that can be extended
near-perpendicularly from the catheter when in position. A
marker alerts the operator to the side of the catheter the
needle will extend from, and this can be orientated towards
the lumen. The intention is that this needle punctures the
lumen and then can guide a wire into it. The re-entry device
is best used early in the attempt to break back into the vessel before the sub-intimal space becomes “baggy”, to
increase the probability of the needle engaging and puncturing the intima.
Examples of re-entry devices include the Outback
(Cordis) and Pioneer (Medtronic) catheters.
Embolisation Materials
Embolisation is the use of a material that induces intentional
blockage or reduction of blood ow. Embolic agents vary in
their permanency, size of material, size of vessel appropriate
for treatment, radiopacity and mechanism of action.
Coils are metallic devices made of titanium, platinum,
stainless steel or nitinol, that attempt to “coil” into a
pre- determined shape at the point of deployment. They are
often covered with Dacron bres that help to cause ow
obstruction, but ultimately rely on the patient’s own coagulation to cause thrombosis. Coils should be tightly packed in
order to be most effective and should be oversized by approximately 15% to improve stability within vessels.
Coils are described by their shape, diameter and length:
– Shape refers to the shape the coil forms when released
and allowed to form the shape it has memory of. Helical
are most common, but a variety of shapes exist for differ-
ent purposes.
– The deployed diameter refers to the width the coil when
formed. Coils are generally oversized by ~25% in relation
to the vessel diameter. The coil wire diameter determines
which catheter is required for deployment—coils are
available in standard 0.035 diameters or micro-coil sizes
such as 0.018 or even 0.010, as with guidewires.
– Length describes the undeployed length of the coil, which
gives the operator an idea of the amount of coil that will
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need to be pushed from the catheter to complete coil
placement. When deployed, they are much shorter due to
the memory shape they take on.
Various types of coil detachment exist. The simplest (and
cheapest) are those that are pushed through a catheter and are
immediately released on exit from the catheter, known as
“pushable” coils. This type of coil can also be ushed from
the catheter using saline. “Detachable” coils feature some
sort of detachment device, which include interlocking mechanisms or electrolytic or mechanical breakage of an internal
wire. Detachable coils are considered when precise placement is required and there is greater risk of coil migration or
non-target embolisation of a vital arterial branch, as stability
of the coil can be tested prior to detachment. Detachable
coils are more expensive.
Vascular plugs (e.g. Amplatzer vascular plugs, Abbott) are
devices that expand to a pre-determined 3D geometrical
shape when unsheathed, much like a self-expanding stent, but
instead are made of a ne, partially occlusive mesh that promotes thrombosis. They are quick to deploy and can be recaptured until the point of detachment, performed by
unscrewing the lock in an anticlockwise direction. Plugs typically require larger delivery sheaths than coils and, like coils,
they rely on the patient’s own clotting to induce thrombosis,
the timing of which is unpredictable. Amplatzer I and II plugs
exist for treatment of vessels from 2–17mm diameter, requiring delivery catheters of 5–9 Fr respectively. Amplatzer IV
plugs are smaller in their delivery calibre and can treat vessels
of 2.5–6mm through a 0.038 guidewire- compatible catheter.
Microvascular plugs (Medtronic) are similar devices, but
instead of mesh have occlusive fabric and therefore do not
rely on thrombus formation. They are lower prole than
Amplatzer plugs, which allows for placement through a
microcatheter in more distal or tortuous vessels, up to
5–7mm in diameter.
Particles are small non-biodegradable materials, most
commonly formed of polyvinyl alcohol (PVA), which can be
uniform (microspheres) or non-uniform. Uniform particles
(e.g. Embospheres, Merit) are more expensive but are less
likely to cause catheter clogging. Particles mechanically
occlude vessels, activate thrombin and cause ingrowth of
broblasts, leading to fairly permanent occlusion.
Particles are mixed with a solution containing 40% contrast, which suspends them and prevents aggregation, and
then are injected following selective vessel cannulation. The
smaller the particles used, the more distal the vasculature in
the vascular bed is blocked. Particles are commonly used
when ischaemia of hyperplastic tissue or tumour is desired,
such as the prostate, uterine broids, or vascular bone metastases prior to surgery. Care must be taken to avoid “nontarget embolisation”, which occurs when the particles travel
to and block an unintended vessel.
Particles can be impregnated with chemotherapy agents
and used to perform chemoembolisation. For example, PVA
particles sized to between 100–500 μm can be soaked in
doxorubicin and used to embolise hepatocellular carcinoma.
A similar principle is utilised for selective internal radiation
therapy (SIRT), where particles are instead radioactive and
deliver local radiotherapy.
Gelfoam is a sponge-like material made of porcine gelatin. It expands when in contact with blood, forming temporary occlusion that later breaks down allowing vessel
re-canalisation within a few weeks. This temporary embolisation has utility in scenarios such as in gastrointestinal
bleeding, such as those caused by an ulcer, or in traumatic
bleeding, where cessation of bleeding until the underlying
abnormality has had time to heal is all that is required.
Gelfoam can be injected as a slurry, formed from aggressive
mixing of Gelfoam strips with contrast in a syringe external
to the patient, or as rolled-up strips known as “torpedoes”.
Liquid embolics solidify or polymerise upon contact with
blood. Glue (cyanoacrylate), indistinct from the agent used
as skin glue, forms a cast within vessels shortly following
injection. A very effective and fast-acting embolic agent, it
requires a greater level of skill and care to use to avoid complication. It is emulsied with lipiodol (Guerbet), a poppyseed oil that acts as both a contrast agent and for extending
the glue polymerisation time, so that the embolic can be
visualised under uoroscopy. A 1:1 mixture creates a very
viscous embolic that will form quickly with little transit,
whereas greater concentrations of lipiodol allow for a more
liquid form that will travel further from the catheter tip. The
delivery catheter must be ushed with dextrose prior to
injection of glue, as normal saline will induce premature
polymerisation.
Onyx (Medtronic) is a newer embolic liquid. It is formed
from a combination of ethylene vinyl-alcohol copolymer
(EVOH), dimethyl-sulfoxide (DMSO) and tantalum powder,
creating a radio-opaque, injectable embolic that forms a
spongy coherent substance when the DMSO diffuses away
in blood. It comes in different formulations, Onyx 18, which
is less viscous and therefore penetrates further, and Onyx 20
or Onyx 34, which are in turn more viscous and more useful
in higher ow scenarios. Prior to Onyx injection, the delivery
catheter “dead-space” should be lled with DMSO to prevent premature polymer solidication.
Finally, sclerosants act to induce endothelial damage,
leading to inammation, thrombosis and eventually brosis.
Sodium tetradecyl sulfate (STS) is a synthetic detergent
commonly used to treat varicose veins, and also used by
some operators in testicular vein embolisation for the treatment of a varicocoele. It is mixed with air to form a foamlike substance. It is not radio-opaque, but can be indirectly
visualised through the formation of a column of contrast that
the foam displaces. Alcohol (ethanol) can be used in a simi-
5 Basic Tools andTerminology forEndovascular Interventions
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41
lar fashion, also inducing endothelial damage and thrombosis; however it must be used with great care to avoid toxicity
and non-target embolisation.
Pressure measurement devices allow for the measurement of vessel pressure. They are xed to the end of a catheter and provide live luminal pressure readings reecting the
position of the catheter tip. Possible use cases include the
assessment of portal or hepatic vein pressures in the context
of trans-jugular portosystemic shunting, or the evaluation of
angiographically dubious stenoses. If a stenosis is signicant, there should be a pressure rise across the stenosis and a
pressure drop beyond it, when compared with proximal
pressures.
Closure Devices
Conventional vessel closure for percutaneous access is with
digital compression. However, closure devices can quicken
vessel closure and reduce the time of, or obviate the need for,
digital compression. Closure devices can shorten the time
required before ambulation and shorten post-operative stays,
increasing efciency within the IR department. Closure
devices can also permit the closure of large holes than would
be possible with digital compression alone. A variety of closure device types exist:
Suture-mediated—Perclose (Abbott), Prostar
– Can be pre-deployed for large bore access as “pre-
closure”, where sutures are then tightened at the conclu-
sion of the procedure.
vessel are the most common contraindications to closure
device usage.
Thrombectomy, Embolectomy and Atherectomy Devices
• Catheters
– Side-hole
– Ultrasonic
• Mechanical
– Stent retrieval devices
– Angiojet
Embolic Protection Devices
Embolic protection devices protect the intracerebral vessels
from emboli during carotid interventions. Filters are the
most common devices but can be difcult to place in tortuous vessels and may induce spasm. Balloon protection is also
available but risks causing cerebral ischaemia while inated.
Filters:
• Fixed basket:
– Symmetrical=Accunet, Emboshield Pro
– Asymmetrical=Filterwire EZ
• Bare wire:
– Symmetrical=Emboshield Pro
– Asymmetrical=Spider
• Balloon protection:
– Proximal=Mo.Ma, NPS
– Distal=Percusurge
Plug closure—Angioseal (Terumo), Mynx Grip/Control
(Cordis), Manta (Teleex)
– These devices place a collagen plug on the external aspect
of the vessel defect, pushed against a luminal object that
is held against the internal aspect of the vessel defect with
traction.
– The Angioseal (Terumo) device uses a luminal footplate
that dissolves 3months following placement. The Mynx
(Cordis) device uses a luminal balloon, that is deated
and removed following plug placement.
Clip closure—Starclose (Abbott)
– A nitinol clip is xed to the external aspect of the arterial
wall and seals the vessel defect.
Each device will have its own individual contraindications and complications and unique method of deployment.
Heavy calcic disease at the puncture site and a small access
Inferior Vena Cava Filters
Venous Ablation Devices
Atherectomy Devices
Intravascular Ultrasound
Central Venous Catheters andPorts
Tunnelled central venous catheters (CVCs) and implantable
central venous access ports provide reliable central venous
access for the delivery of prolonged courses of cytotoxic
therapy or intravenous antibiotics and for blood sampling.
Tunnelled CVCs are also used for the administration of parenteral nutrition or to facilitate haemodialysis.
Ports require a more involved procedure to install, but are
entirely internal once implanted, reducing the risks of infection and migration, and requiring fewer limitations in terms
of bathing or sports.
Tunnelled CVCs are composed of silicone or polyurethane and feature a cuff that sits close to the exit of the tunnel, inducing a brotic reaction that seals the subcutaneous
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