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1.6 Antegrade Approach
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39
load (to ensure greater crossability) and should nd the
point where the guidewire cannot easily be advanced
further. Then you should explore the direction in which
the guidewire can be advanced slowly without deviating
into the subintimal space (penetration with exploration
by the xed point guidewire rotation strategy [Fig. 1.51];
see 1.4.6.3. “Fixed Point Guidewire Rotation”).
5. In some cases, you cannot prevent the guidewire from
slipping into the subintimal space. In this situation, you
should pull the guidewire back to a point close to the
entrance of the CTO and advance it in a different direction while attempting to follow the true lumen. If this
also fails, you should orient the guidewire tip in the
opposite direction to explore the site where it was
blocked by hard tissue (Fig.1.52). If no such site can be
found, you should withdraw the guidewire to the entry
and search for a dimple again. Alternatively, you can use
the parallel wire technique. If the site of obstruction is
found, you should keep the guidewire tip at that point
and subtly direct it in the presumed direction of the true
lumen. You should push the wire forward slightly while
gently rotating it within ±90 degrees (see 1.6.4.3 “Fixed
Point Guidewire Rotation”). If this maneuver leads to
smooth advancement of the guidewire, there is a 90%
probability that its tip is in the subintimal space. If the
guidewire advances gradually without deviation, it is
more likely to be in the true lumen.
6. If the guidewire is blocked by hard tissue inside the
lesion despite these exploratory efforts, you should
exchange it for another wire with a higher tip load
(greater crossability) and explore the optimal direction
for advancing the wire (exploration with penetration
strategy).
7. You should set a landmark and then explore the optimal
direction for advancing the guidewire with reference to
the landmark (exploration with landmark strategy).
I think that the basic guidewire crossing techniques
can be summarized as (1) through (7) above, but it is also
necessary to consider the variations described below.
8. A CTO can have the combined features of (2) and (3) if
occlusion initially arises from a tight stenosis and thrombosis progresses to the nearest side branch at the proximal end of the occlusion (Fig.1.46c). In such a CTO, a
guidewire that is aligned with the center of the true
lumen at the entrance to the lesion can be advanced
smoothly through the true lumen.
9. There are many possible variations with regard to evolution of the lesion. If there is a brous cap at the proximal
end of the occlusion, brosis and calcication will be
more advanced at this site. Accordingly, a guidewire
with a high tip load should be used to penetrate the proximal cap. After entering the true lumen, it may be reasonable to step down to a less stiff wire.
10. If a guidewire is blocked by a calcied region within the
CTO, it may represent preexisting calcied plaque or
may be calcication that occurred after occlusion
(Fig.1.53). In both cases, you should explore the optimal
route by performing xed point rotation of the guidewire
in an exploratory manner (see 1.6.4.7 “Rotation”).
11. Another tissue that can exist before occlusion is soft
plaque, which is often associated with positive remodeling. When the guidewire is manipulated within soft plaque
inside the lumen, the tip moves relatively freely, and you
may feel as if the tip has gone outside the vessel wall
(Fig.1.54). Also, the distance between the guidewire tip
and an available landmark in the lumen may be too long
to allow estimation of the correct route for advancing the
wire. In this situation, while the interventionalist expects
the guidewire to pass through the subintimal space, postcrossing IVUS often demonstrates that the guidewire has
actually crossed the lesion through the true lumen.
12. Sometimes, part of an occluded vessel may undergo
extreme negative remodeling (Fig.1.55), and the guidewire may enter the subintimal space at the end of such a
region. You can only conrm this by post-crossing
IVUS, so it is important to advance the guidewire
according to the standard rules even at such sites.
Some lesions show both positive and negative
remodeling.
When selecting the exploration strategy, you must
keep the following in mind: “Always start guidewire
manipulation with a feather touch and never push the
guidewire so strongly as to deect the tip” (see Chap. 5:
“Mitsudo’s Non-pushing PCI Technique”). Specically,
you should:
13. Always start exploration of the guidewire route with a
feather touch.
14. Even when advancing a guidewire after the tip has
entered a dimple, only the minimum force required to
advance it should be employed.
15. Never push the guidewire forward strongly enough to
deect its tip.
16. If there is no route to advance the guidewire with a force
that does not deect its tip, exchange the wire for one
with a higher tip load.
17. Start manipulation of the new guidewire with a
feather touch, and explore the route that allows
advancement with a force that does not lead to deflection of its tip.
It is uncommon to obtain information on the mechanisms
involved in CTO formation and the histology of the lesion
and surrounding tissues before starting PCI.However, you
can make an estimate from the patient’s medical history, age,
and concomitant illnesses, as well as angiographic images of
the lesion. After starting PCI, you may also obtain supporting information from the actual sensations as the guidewire
is manipulated through the target vessel. For practical tips
about xed point guidewire rotation, please refer to 1.6.4.7
(page 58).
40
Microchannel
（＋）
Tracking microchannel
Microchannel（−
）
Central softer tissue
a
b
c
Microchannel（−
）
Central softer tissue
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1 Mitsudo’s PCI Techniques forCTO
Guidewire
Occlusion site
Microchannel
Vessel
Fig. 1.48 Exploration strategy. If there is a microchannel within a rela-
tively large occluded vessel, you should nd its entrance and insert the
guidewire. Once the entrance has been identied, the next step is to
track the microchannel. You must not try to penetrate the CTO with a
guidewire that was selected for tracking. When it is advanced forcibly
in an attempt to cross the CTO, the guidewire often enters the subintimal space, even if it does not have a stiff tip
（＋）
Guidewire
Occlusion site
Vessel
（−）
Guidewire
Occlusion site
Vessel
Fig. 1.50 Penetration with exploration strategy. The guidewire should
be advanced through homogenous tissue within the CTO.The hardness
of the plaque and the subintimal layer, as well as the distribution of
plaque, may determine the correct direction for advancing the guidewire. If it is pushed forward forcibly, the guidewire will also deviate
into the subintimal space in this setting, so you should advance the
guidewire slowly with little force while exploring to nd the correct
direction
Fig. 1.49 Exploration with penetration strategy. The guidewire should
be advanced while exploring to nd a relatively soft site where occlusion would have occurred most recently. This strategy may be the same
as “loose tissue tracking” (proposed by Sumitsuji). At the entry to the
CTO, you should search for a point where the guidewire can penetrate
the cap with as little pressure as possible. If exploration while pushing
the guidewire strongly enough to slightly deect its tip fails, you should
exchange the guidewire for another wire with a higher tip load and
repeat exploration. If the guidewire enters the lesion, you should then
advance it with as little force as possible while exploring to nd the
correct direction
Fig. 1.51 Penetration with exploration by xed point guidewire rota-
tion. (a) If a guidewire becomes blocked by hard tissue within the
lumen and then abruptly moves forward when pushed forcibly, its tip
will usually have entered the subintimal space. (b) After slightly
advancing the guidewire, either of the two projections will often show
that it has been deected. If so, you should pull the guidewire back
nearly to the inection point and search for the place where the wire
was initially obstructed. (c) While keeping the guidewire tip at the
blockage to prevent subintimal deviation, you should orient the tip in
the opposite direction. Then you should explore to nd the direction in
which the guidewire can be advanced while rotating the tip within ±90
degrees
a
b
c
a
b
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Fig. 1.52 If the guidewire enters the subintimal space relatively easily.
(a) In this situation, the guidewire has been advanced into the subintimal space without any resistance, so the point at which the wire actually
enters the subintimal space is difcult to determine. (b) If it is expected
to be possible to track the true lumen from the entry of the CTO, you
should pull the guidewire back to a most proximal point possible within
the lesion and orient it in the opposite direction to explore for the correct route. (c) If this maneuver fails to advance the guidewire through
the true lumen, you should completely withdraw the guidewire from the
lesion and nd a new entry point that is more likely to allow successful
crossing of the CTO
41
Fig. 1.54 Occlusion of a segment with positive remodeling. If there is
marked positive remodeling, it may feel as if the guidewire is not crossing the lesion through the true lumen
Fig. 1.55 Negative remodeling of the occlusion. This shows an
occluded coronary artery with extreme negative remodeling, which
means that a guidewire advanced through plaque readily deviates into
the subintimal space
Fig. 1.53 Inuence of calcied plaque at the occlusion. (a) The tip of
the guidewire may enter preexisting plaque and become blocked by a
calcied area of the plaque. (b) Alternatively, the tip of the guidewire
may be obstructed by calcication at the core of the lumen where nal
occlusion occurred
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Column 5 Advancing the Guidewire and Inuence of Tissue Hardness
1 Mitsudo’s PCI Techniques forCTO
Here, I will discuss how the hardness of tissue in the lesion inuences advancement of the guidewire. This discussion
is theoretical because we cannot accurately know the ultrastructure of each lesion. Nonetheless, we can often accomplish PCI successfully by devising strategies while simulating various scenarios during the procedure. Although the
model used here has relatively soft tissue at the core, many of the lesions encountered in practice are homogeneous or
heterogeneous with a mosaic structure. These latter two types may be modeled as homogeneous lesions and calcied
lesions, respectively.
A guidewire with a tip that is stiff enough to penetrate the core tissue and not stiff enough to go through the surrounding plaque can readily follow the true lumen. A CTO with this histological architecture can be successfully
crossed by drilling with a non-tapered guidewire of intermediate stiffness (Intermediate Miracle series; Fig.1.56).
The hardness of the lesion will not necessarily be compatible with the stiffness of the guidewire selected. Of course,
a guidewire that is less stiff than a CTO cannot cross it. Also, as the intima/media is unexpectedly soft, even a exible guidewire is likely to enter the subintimal space. Since we usually do not know the exact hardness of the CTO,
it is generally more economical to initially choose a moderately stiff guidewire, rather than stepping up from a more
exible wire. There are several tips for making the best use of stiff guidewires. If a stiff guidewire is advanced with a
stronger force than is required for crossing the target plaque, it is likely to go through the plaque into the subintimal
space (Fig.1.57).
So, how should we manipulate the guidewire to avoid this outcome? The strategy to adopt is “exploration,” and it
is based on the following assumption. As seen in Fig.1.57, the guidewire chosen is stiff enough to cross the occlusion
and may be stiffer than required to penetrate the target plaque (which is considered to be hard). In order to advance
such a stiff guidewire through relatively soft tissue rather than through hard plaque, you should start PCI by exploring
to nd the point where the guidewire can be advanced with as little force as possible. What is the optimal force for
advancing the guidewire? I have measured the optimal force for advancing a Conquest Pro guidewire as “about 0.6 g”
and “no more than 1.0 g” at maximum. When advanced using such force, the Conquest Pro guidewire often follows the
soft core and does not penetrate hard plaque. If this exploration strategy using minimal force fails to advance the wire,
it means that the core is not as soft as was expected. Then there is no choice other than to gradually increase the force
applied to the wire until it enters the core, but it should never be pushed strongly enough to deect the tip.
If even these efforts fail to identify the entry point or direction for crossing, you should exchange the guidewire for
a stiffer one. Again start manipulation with minimal force, and gradually increase the force until crossing is successful.
When a stiff guidewire is selected, you must not apply force strongly enough for its tip to be deected.
This method of manipulation is applicable to all crossing guidewires, including those in the Conquest Pro and Gaia
series (Fig.1.58).
A lipid-rich plaque within the CTO may lead the guidewire into the subintimal space. If the guidewire enters the
subintimal space, you should pull it back to the proximal part of the occlusion and try to advance it in the right direction again. However, subintimal guidewire deviation can only be veried by performing IVUS after recanalization. A
lipid core in the plaque may be detected by CT, but is unlikely to provide an accurate landmark for deciding the optimal
point to which the guidewire should be pulled back. You should retry crossing the CTO after pulling the guidewire back
a long way if there is a possibility of success (Fig.1.59).
A guidewire that is stiffer than the plaque at a CTO, but less stiff than a calcied or brosed region within the lesion,
is likely to enter either the plaque or the subintimal space (Fig.1.60).
Even if a guidewire is surrounded and blocked by hard tissue, you must not push it forward strongly enough to
deect it. If the presence of calcied plaque is suspected, you should explore to nd a route that allows the guidewire to
bypass the plaque, remembering that the gap between two calcied plaques will also be relatively hard. If a guidewire
Bypass
wire with a stiffer tip
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is blocked by hard tissue, it is generally safer to exchange it for a stiffer wire. However, even a stiffer guidewire cannot penetrate the core of a calcied plaque, so it is necessary to try to advance the wire through the gap between two
calcied plaques or near the rim of each plaque (Fig.1.61).
Even while exploring with minimal force, you may accidentally advance a guidewire into the subintimal space and
through the adventitia. If a guidewire advanced with minimal force has reached the artery distal to the occlusion but
is in the adventitia, the wire must have entered the subintimal space at the entrance of the occlusion (Fig.1.62). While
leaving this guidewire in place, you should try to nd another route through the CTO from the entrance with a second
guidewire. If there is a side branch that can accommodate an IVUS catheter, you should perform IVUS to check that
the second guidewire is located at the correct entry point before advancing it further (Fig.1.63).
43
Fig. 1.56 Inuence of tissue hardness on advancing the guide-
wire. H
ness of the guidewire, H
H
<SGW<HP, H
CST
hardness of the adventitia, H
Ad
CST
hardness of the surrounding plaque,
P
hardness of the soft core, SGW stiff-
hardness of the lipid core
Lip
Fig. 1.57 If the guidewire is stiffer than the surrounding plaque.
H
<HP<S
CST
GW
Fig. 1.58 If the guidewire is stiffer than the surrounding plaque.
H
<HP<S
CST
GW
Fig. 1.59 If there is lipid-rich plaque within the occlusion.
H
<H
Lip
<HP<S
CST
Lipid-rich plaque may lead the guidewire
GW.
into the subintimal space
Fig. 1.60 If there is hard tissue within the occlusion.
H
<H
<SGW. If there is calcied plaque, then HP<SGW<H
P
CST
CST
The guidewire is blocked by the hard tissue and deviates into the
subintimal space
Exchange the guidewire for another
Fig. 1.61 If there is hard tissue within the occlusion.
H
<H
<SGW. If there is calcied plaque, then HP<SGW<H
P
CST
CST
Exploration should be performed to nd another route that allows
the guidewire to bypass the plaque
.
.
44
PF GTA= /
PF
2
=
()
PF
2
=
()
GG
22
./
()()
pp
()
./
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1 Mitsudo’s PCI Techniques forCTO
1
2
Fig. 1.62 If the guidewire has been advanced through the adven-
titia from the CTO entry point. H
wire advanced with minimal force has reached the vessel distal to
the occlusion in the adventitia, the wire must have entered the subintimal space at the CTO entry
<H
<SGW<HP. If a guide-
Ad
CST
1.6.4 Guidewire Strategies
1.6.4.1 Tip Load andPenetration Force: Why
aCrossing Guidewire Is Needed
toPerform Antegrade PCI forCTO
You may think that a non-tapered CTO guidewire with an
intermediate tip load can more readily penetrate hard plaques
and would be safer to use, i.e., less likely to deviate into the
subintimal space or outside the vessel wall. It is true that a
non-tapered guidewire can sometimes easily cross an occlusion even if it is not manipulated carefully.
However, a tapered guidewire has greater maximum penetration force per area unit compared to a non-tapered guidewire with an identical tip load, and thus less force needs to
be applied for it to cross a lesion of a given hardness. The
maximum penetration force is calculated as follows:
Fig. 1.63 If the guidewire has been advanced through the
adventitia from the CTO entry. The guidewire may be inadvertently advanced through the subintimal space, even if it is pushed
with minimal force throughout the procedure. Once the wire has
entered the subintimal space, it is likely to advance while creating a dissection, even when very little force is applied. If the
guidewire deviates from the true lumen into the subintimal space
within the lesion, you will generally feel some obstruction during manipulation. It is reasonable to consider that the guidewire
has entered the subintimal space at the CTO entry
force, a 0.014-inch guidewire would need a tip load about 2.5
times higher than that of a 0.009-inch guidewire. Therefore,
you do not need to push so hard on a tapered crossing guidewire to advance through a CTO.This is a great advantage
of a tapered wire and is the chief reason why I use a tapered
crossing guidewire when performing antegrade PCI for CTO.
However, please note that the penetration force of a
guidewire during PCI also depends on the “pushing force”
applied to it. For example, applying a force of “X g” (where
X<9g) to the Conquest Pro 9-g and 12-g guidewires (both
have a 0.009-inch tip) will result in exactly equal penetration
force with both wires:
PF =
X/
p
X /. /0 00006362
=
2
0 009 4
2
gin
where PF is the penetration force, G is the tip load, and TA
is the tip area. The ratio of the maximum penetration force
of a crossing guidewire with a 0.009-inch tip relative to a
guidewire with an identical tip load and a 0.014-inch tip is
calculated as follows:
//.///
PF PF
914
14
9
=
22
0 014 0 009
./.
=
242
.
=
Thus, the penetration force of a guidewire with a 0.009inch tip is about 2.5 times greater than that of a guidewire
with a 0.014-inch tip. Conversely, to acquire equal penetration
G
0 0014 4
/. /p
G
0 0009 4
/. /p
0 0009 400014 4
During PCI, the penetration force of a guidewire is a function of the pushing force and is independent of the intrinsic maximum penetration force, so it varies with the force
applied to the wire. However, a guidewire with a tip load
of 9g must not be pushed with a force greater than 9 g (as
explained later), while a guidewire with a tip load of 12g
can be pushed with a force of up to 12g and therefore has a
greater maximum penetration force.
A crossing guidewire usually has a hydrophilic coating,
except at its tip. Friction between the shaft and the surrounding tissues increases the force needed to advance the
guidewire through a lesion. To reduce friction and make
“non-pushing PCI” practicable, a guidewire with a hydrophilic coating is required.
However, hydrophilic coating makes it more difcult to
determine whether the guidewire has remained within the
true lumen or is being advanced through the subintimal space.
Certainly, the current CTO crossing wires do not produce sufcient friction to create a “rough” sensation. Of course, this
“rough” sensation is subjective and cannot be quantied or
ab
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45
reported accurately. If possible, interventionalists should try
to assess the outcome of PCI and transmit their own techniques to the next generation by using objective measures.
You do not need to use a guidewire with a hydrophilic
coating on the tip when trying to catch a small dimple at the
CTO entrance (Fig.1.64) or when directing the tip of the wire
in the desired direction within a lesion (Fig.1.65). A coated
tip may make the guidewire so slippery that it becomes hard
to catch and penetrate a dimple or change direction inside the
CTO.Therefore, the tip of the guidewire (at least the ball of
the tip) should not have a hydrophilic coating.
If guidewires with different tip loads exhibited identical
behavior, it would be possible to substitute a guidewire with
a higher tip load for a wire with a lower tip load by using less
force to advance the former wire. If so, gradually stepping
up guidewires would be unnecessary, and a single guidewire
would be enough to accomplish PCI, but this is not true in
practice. In this subsection, I will discuss the structural and
strategic factors affecting guidewire manipulation based on
my empirical evidence and logical deduction.
Slip!
Fig. 1.64 Slipperiness of the guidewire. When manipulated to catch a
small and shallow dimple, a guidewire with a smooth tip is likely to
deviate into a side branch and fail to penetrate the dimple (a). On the
other hand, a guidewire without a smooth tip is more likely to catch and
penetrate the dimple (b)
Fig. 1.65 Problem with hydrophilic coating. If a guidewire
becomes blocked by calcied plaque, you may want to change
direction. In this situation, a guidewire with hydrophilic coating
on the tip may slide past the plaque and go in the wrong direction (dotted line)
46
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1 Mitsudo’s PCI Techniques forCTO
1.6.4.2 Curve oftheGuidewire Tip
A guidewire with a straighter tip has stronger penetration
force. When a bench test is performed, the tip load of the
guidewire is measured with its tip straight. However, you
cannot control the direction of a guidewire with a straight
tip when it is in a CTO (Fig.1.66). What is the optimal size
and angle for the curve of the guidewire tip? All patent (nonoccluded) vessels have curves to a greater or lesser extent.
For advancing a guidewire through a curved vessel, it is ideal
if the distance between the tip and shaft of the wire is slightly
greater than the inner diameter of the vessel (Fig.1.67). It
should optimally be 1 to 1.5 mm (30 to 40%) larger than
the vessel diameter, although this depends somewhat on the
curvature of the vessel. If the distance between tip and shaft
is too short, the guidewire cannot be directed toward a side
branch. If the distance is too long, it becomes difcult to
control the wire at a sharp bifurcation.
A target vessel with a CTO corresponds to a vessel with
an inner diameter of 0 mm. However, advancing a guidewire creates a new channel with an inner diameter of about
0.014 inches (≈0.35 mm). When the abovementioned rule
is applied, the optimal size of the curve at the guidewire tip
is calculated to be about 0.5 mm and slightly larger than
0.35mm. If the tip diameter is 0.009 inches (=0.225mm), a
guidewire with a curve slightly larger than 0.225mm should
be chosen.
While participating in the development of Conquest Pro
guidewires around 1998 to 2000, I tried to minimize the
curve of the tip. Using an inserter, I was able to shape a
curve only 1 to 2mm in size, as shown in Fig.1.68, but
I found that the curve was lost during intervention. I then
tried to manually shape a curve at the tip of the wire with
a 25-G needle or after extruding the tip from the top of the
inserter, but failed to create a curve with a consistent shape
and size. Since manual shaping also caused severe pain in
my ngertips, I asked the manufacturer to make me a shaping device (Fig.1.69).
I used this device to handcraft curves at the guidewire tip
(Figs.1.70 and 1.71). As can be seen in this photograph, these
guidewires do not have a second curve, but I initially tried
to cross CTOs with such guidewires. It could be suggested
that a tapered guidewire with a high tip load might only go
straight forward, but I thought that even such a wire could be
deected if advanced with minimal force after being blocked
by a hard lesion (too hard to penetrate with a Conquest Pro).
Because the tip load of a guidewire is measured with the tip
straight, you may think that a guidewire with a tip load of
9 g cannot be deected unless a force greater than 9 g is
applied. However, a guidewire with a curved tip like that
shown in Fig.1.70 is deected by even weaker forces. Dr.
Osamu Kato referred to this as the “deection” phenomenon
and promoted this concept.
When manipulated within loose tissue, a guidewire with
a high tip load and a small curve will go straight toward the
lateral wall of the vessel at a bend. However, if such a guidewire becomes blocked by tissue that is too hard to penetrate,
the curve of the tip will be increased whenever the wire is
pushed, and its tip will be oriented medially in the desired
direction (Fig.1.72). The guidewire can be advanced through
a CTO in the desired direction if its tip, even if deected, can
nd the optimal route. Thus, I found it possible to control
the direction of the tip of a guidewire when the tip load and
curve had been optimized with reference to the hardness of
the target lesion, even if the tip was stiff and tapered as with
the Conquest Pro series.
Subsequently, I only used guidewires from the Conquest
Pro series with a small tip curve for a while, and these guidewires were deected from hard tissues inside many CTOs.
However, I found that I could not direct a guidewire without a
second curve toward the CTO entry in some tortuous vessels.
Therefore, I handcrafted a guidewire with a gentle second
curve (Fig.1.73). I found that this modication sometimes
led to successful crossing of the CTO, but the second curve
was easily lost during prolonged manipulation, making the
tip straighter and leaving only the rst curve. To prevent this,
the second curve must be created by bending the guidewire.
I initially thought that bending the guidewire at 5–8 mm
from the rst curve (Fig.1.74a) would create a gentle second
curve, but I found that a guidewire curved in this way produced severe whipping artifacts and was difcult to control.
By reducing the distance between the rst and second curves,
I gradually overcame problems with whipping. Finally, I
found that the optimal distance between the two curves was
about 2mm (Fig.1.75b) to minimize the frequency of whipping while preserving a functional second curve.
At present, I set an almost constant distance between the
two curves at the tip of a tapered CTO crossing guidewire,
but I slightly modify the angles of the curves according to the
diameter of the target vessel just proximal to the occlusion,
the type of stump (abrupt or tapered), the tortuosity of the
vessel, and the hardness of the occlusion (Fig.1.75).
As mentioned later, the guidewire needs a sufciently
large curve at its tip to orient it toward the entry of a bifurcation occlusion or an occlusion in a large tortuous vessel. In
such circumstances, a gentle curve at the tip of a guidewire
with a low tip load (e.g., an XT-R or XT-A) can prevent it from
becoming straight during manipulation, whereas a guidewire
from the Gaia series or any other series with a higher tip load
should desirably have multiple staggered curves (Fig.1.76b)
rather than a single gentle curve (Fig.1.76a).
The optimal size and acuteness of the curve at the tip will
depend on the features of the lesion, which are often demonstrated during IVUS-guided PCI.If a guidewire with the
tip shape shown in Fig.1.77a cannot remain inside the true
lumen at a point distal to the CTO entry, penetration should
be reattempted after the curve of the tip has been made
slightly smaller and slightly more acute (Fig. 1.77b). This
second attempt is often successful.
a
b
c
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Fig. 1.66 Guidewire with a straight tip. A guidewire with a straight tip
has the greatest penetration force, but its direction is difcult to
control
a
47
Fig. 1.68 Optimal guidewire tip curve for crossing a CTO. (a) If the
plaque is hard, a guidewire with a tip curve slightly larger than the
diameter of the new channel created by advancing the guidewire (0.009
b
to 0.014 inches=0.22 to 0.35mm) should be used. (b) A guidewire
with too large a tip curve is difcult to control. (c) Conquest Pro guidewire with a tip curve shaped by using an inserter
c
Fig. 1.67 Guidewires with tip curves of various sizes in non-occluded
coronary arteries. While the vessel diameter changes continually, the
relationship between diameter and the size of the guidewire tip curve at
critical points is considered here. (a) If the curve of the guidewire tip is
too large for the vessel diameter, it is difcult for the guidewire to enter
a small side branch arising at an acute angle (particularly if a larger
curvature is required to enter the branch). (b) On the other hand, if the
curve of the guidewire tip is too small for the vessel diameter, the guidewire cannot reach the ostium of a side branch arising at an acute angle
for which a smaller curve is needed or is likely to enter another side
branch that requires a larger curve. (c) It is optimal for the curve of the
guidewire tip to be slightly larger than the vessel diameter
48
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1 Mitsudo’s PCI Techniques forCTO
Fig. 1.69 Shaping device. To shape a curve at the tip of a guidewire,
insert the tip into the hole at the top of the device (a), and bend the tip
(b). This simple device is useful for creating small curves at the tips of
guidewires, including wires in the Conquest Pro and Gaia series. The
smallest curve that can be created with this device is around 0.5 to
0.6mm. While there is no device or method available to shape even
smaller curves at the guidewire tip, curves of this size are sufcient for
manipulation
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