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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3892_Библиотеки_им_академика_М_И_Перельмана
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48
What units
are catheter
inner diameters
measured in?
Inches. This correlates with the units of wire
diameters.
What units are
wire diameters
measured in?
Inches
What are the units
of catheter length?
Centimeters
Sheath French
sizes refer to what
measurement?
Inner diameter. Select sheath size based
on the goal of the procedure and what
interventional device (balloon or stent) will
be used.
The outer diameter
of a sheath is how
much bigger than
its inner diameter?
Sheath outer diameter, and therefore size
of arteriotomy or venotomy is 1.5–2-French
sizes bigger than that of its inner diameter.
M. C. Taon
https://t.me/med1917
49© Springer Nature Switzerland AG 2022
R. Chand et al. (eds.), Essential Interventional Radiology
Review, https://doi.org/10.1007/978-3-030-84172-0_11
Chapter 11
Guidewires
MatthewCzar Taon
M. C. Taon (*)
Kaiser Permanente Los Angeles Medical Center,
Los Angeles, CA, USA
https://t.me/med1917
50
What are the
four major
components
of a
guidewire?
Core, tip, body, and coating. Guidewires can be made of various materials including stainless steel,
nitinol, platinum, or other alloy metals. The core of a guidewire, referred to as a mandrel, is composed
of a stiff, inner, central wire upon which subsequent layers are wound. The shaft of wires can have
different degrees of stiffness and facilitates structural integrity during wire use. The stiffness of the
shaft is primarily attributed to the metal type and thickness of the core.
The distal end of the guidewire is referred to as the tip. If the core extends up to the tip of the wire, it
is referred to as a “core-to-tip” design, which provides good tactile feedback, tip control, tip load, and
torqueability. If the core does not reach the distal tip of the wire, a small, flat metal ribbon provides
the continuity to the distal most tip, and is referred to as a “shaping ribbon” design. This design
provides good wire shape retention, softness, and flexibility of the tip, but with decreased tip torque
control. Historically, guidewire designs incorporated a fine “safety wire” along the full length of the
wire to prevent the outer wire coil from uncoiling and breaking off. This precursor to the safety ribbon
design allowed the wire to be shaped but resulted in added tip stiffness. Some wire tips lack a shaping
ribbon altogether resulting in greater wire flexibility and safety but with decreased directional control.
The body of a guidewire includes coils, covers, and sleeves. The body of the guidewire, surrounding the
core, is typically made of coils or polymer (plastic) covering. If a guidewire consists of a polymer cover
along the body but leaves the distal free coils along the tip uncovered, this is referred to as a sleeve.
The spring coil design contributes to a wire’s shapeability, shape retention, and tactile feedback. A
polymer cover design can improve guidewire deliverability but may decrease tactile feedback.
The body of the wire, whether it be a spring coil or polymer cover design, can have an additional
coating. This additional coating can reduce surface friction, improve tactile feedback, and improve
guidewire tracking. Hydrophilic coating attracts water to create a slippery “gel-like” surface for
improved trackability. Alternatively, hydrophobic coating repels water to create a “waxlike” surface
which enhances tactile feedback but decreases slipperiness and trackability.
M. C. Taon
https://t.me/med1917
51
What is the
relationship
between
columnar
strength
(stiffness)
of a wire,
torsional
strength, and
radius of the
wire?
Both the stiffness and torsional strength of a guidewire are directly proportional to the fourth power
of the core diameter.
What are the
two factors
of guidewires
that
determine
frictional
resistance?
Guidewire stiffness and the coefficient of friction
(continued)
11 Guidewires
https://t.me/med1917
52
What is the
relationship
between
lubricity of
a guidewire
and tactile
feedback?
Inverse relationship. As lubricity increases, tactile feedback decreases.
What is tip
load?
Tip load is the measure of how many grams of force (gram-force) are required to buckle a wire tip
when forced against a standard surface.
What is
penetration
power?
Penetration power is calculated as wire tip load divided by wire tip area. Tapered tip wires have
higher penetration power as compared to non-tapered wires, even if tip load is equivalent, given the
decreased wire tip area. Also, penetration power can be increased for any wire if there is an over-the-
wire device in place, such as a microcatheter, with minimal wire protrusion.
How does
a long core-
to-tip taper
compare to
a short core-
to-tip taper
in terms of
support and
trackability?
Wires with a long core-to-tip taper provide improved vessel tracking but less support. Wires with a
short core-to-tip taper provide more support but greater tendency to prolapse.
M. C. Taon
https://t.me/med1917
53
What is the
difference
between
hydrophilic
and
hydrophobic
wire
coatings?
Hydrophilic coatings attract water to create a “gel-like,” lubricious wire surface. Given the ease
of advancement, these carry a risk of dissection or perforation. Hydrophobic coatings repel water
to create a “waxlike” wire surface with improved tactile feedback but decreased lubricity and
trackability.
How long
should an
exchange
wire be in
relation to
the length of
the catheter
being
utilized?
Ideally, an exchange wire should be two times the length of the catheter to maintain wire positioning
during catheter exchange.
What is the
SAFARI
technique?
SAFARI refers to subintimal arterial flossing with antegrade-retrograde intervention. It involves
obtaining through-and-through wire access in the subintimal space to cross a chronic total lower
extremity arterial occlusion.
11 Guidewires
https://t.me/med1917
55© Springer Nature Switzerland AG 2022
R. Chand et al. (eds.), Essential Interventional Radiology
Review, https://doi.org/10.1007/978-3-030-84172-0_12
What is the
difference between a
nonselective (flush)
catheter and a
selective catheter?
Nonselective flush catheters are designed
to withstand high injection pressures
and provide high-flow rate contrast
injections with uniform contrast dispersal
and minimal recoil. Selective catheters
are designed to provide improved
torqueability, facilitate cannulation of a
vessel orifice, and obtain distal access.
A guiding catheter is a type of selective
catheter and is constructed to have a larger
inner diameter to assist in delivering and
stabilizing interventional devices.
Generally, what are
the three layers of a
guiding catheter?
An outer layer composed of polyurethane
or polyethylene to provide stiffness, a
middle layer composed of a wire matrix for
torque generation, and a lubricious inner
coating made of polytetrafluoroethylene
(PTFE) to allow for smooth passage of
balloon catheters and stents.
Chapter 12
Catheters
MatthewCzarTaon
M. C. Taon (*)
Kaiser Permanente Los Angeles Medical Center,
Los Angeles, CA, USA
(continued)
https://t.me/med1917
56
What are the three
basic components of
a guiding catheter?
A hub for connection; a shaft with varying
diameter, length, and stiffness; and a soft
tip
What is one method
to determine if
a catheter tip is
facing anterior or
posterior?
The catheter tip is facing the anterior
position if it turns right with clockwise
rotation and left with counterclockwise
rotation. The catheter is facing the
posterior position if it turns left with
clockwise rotation and right with
counterclockwise rotation.
What is the
difference between
passive and active
support methods
to keep a guiding
catheter in position
and to provide a
stable platform?
Passive support is dependent on the
inherent physical characteristics of the
guide catheter wall and the preformed
shape of the catheter. Minimal
manipulation of the catheter is required.
Active support requires operator-
dependent catheter manipulation to seat a
catheter beyond the ostium of a vessel or
mold the catheter within the endovascular
space to obtain stable position.
What is the double
flush technique?
For catheters at or above the thoracic
aorta, a double flush technique is used
to prevent migration of blood clots into
the cerebral circulation. This technique
requires two syringes: one is utilized to
aspirate the catheter with subsequent
disposal of the contents, while the other
syringe is utilized to flush the catheter.
What are the
characteristics of a
braided catheter?
Braided catheters have increased axial
rigidity, have improved stability, are less
vulnerable to kinking or rupture, but have
less ability to be steam shaped.
In general, why
must a catheter be
advanced over a
wire?
To prevent the catheter tip from scraping
the vessel wall and causing dissection or
emboli
M. C. Taon
https://t.me/med1917
57
What is a method to
prevent inadvertent
air embolus from
occurring during
guidewire removal
from a catheter?
Remove the guidewire slowly and drip/
inject heparinized saline into the catheter
hub during wire withdrawal.
What is the
difference between
a rapid exchange
(monorail) system
compared to an
over-the-wire
system?
With a rapid exchange (monorail) system,
the guidewire exits the catheter relatively
close to the tip of the catheter, allowing
the use of shorter wire lengths and smaller
wire, catheter, and interventional device
diameters. With an over-the-wire (OTW)
system, the guidewire passes through the
entire length of the catheter lumen in a
coaxial fashion.
12 Catheters
https://t.me/med1917
59© Springer Nature Switzerland AG 2022
R. Chand et al. (eds.), Essential Interventional Radiology
Review, https://doi.org/10.1007/978-3-030-84172-0_13
What are examples of
flow-control devices?
Flow switches, metal or plastic
stopcocks, K-switch valves used
for CO2 angiography, and rotating
hemostatic valves
What is the difference
between a Luer-lock and
a Luer-slip connection?
A Luer-lock tip has a collar with an
internal thread and requires twisting
and locking of the connection tip.
It is used for injections requiring a
secure connection. A Luer-slip tip is
composed of a smooth spigot without
a collar. It requires a friction-fit
connection utilizing push-and-twist
technique. Luer-slip tips are used for
rapid refilling or for tasks involving
multiple adapters.
Chapter 13
Connectors
MatthewCzarTaon
M. C. Taon (*)
Kaiser Permanente Los Angeles Medical Center,
Los Angeles, CA, USA
(continued)
https://t.me/med1917
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