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of dissection in the distal segment even if that segment has
no plaque, and this risk is increased by more rapid balloon
ination.
In contrast, what will happen if a 2.75-mm balloon is
selected with the intention of inating it at a high pressure
(18 atm) to a diameter of 3.05 mm? Although an indentation may remain after ination at the nominal pressure
(Fig.5.16d), gradually escalating the pressure to 22atm may
remove the indentation and achieve a nal balloon diameter
of about 3.05mm (Fig. 5.16e). This approach considerably
reduces the risk of dissection in the distal segment.
The stenosis may sometimes be harder than expected. The
approach I explained above aims to achieve optimal stent
expansion by upfront high-pressure ination of a slightly
undersized balloon while ensuring the safety of high- pressure
angioplasty by slowly escalating the ination pressure. This
reduces the risk of dissection associated with unplanned
high-pressure ination of a balloon to an oversized diameter.
5 Mitsudo’s Non-pushing PCI Techniques
Fig. 5.16 My method of high-pressure balloon angioplasty. In a ste-
notic vessel (a), ination of a balloon with a diameter matching the
luminal diameter of an intact segment of the vessel at its nominal pressure results in insufcient preparation of the lesion (b). If this balloon is
inated at a higher pressure to achieve sufcient lesion preparation (and
optimal stent expansion), the nal balloon diameter will exceed the normal luminal diameter, possibly leading to dissection (c). An undersized
balloon can be inated at high pressure to a diameter matching the normal luminal diameter. If ination to the nominal diameter results in
insufcient lesion preparation (d), the undersized balloon can be
inated to an even higher pressure without exceeding the normal luminal diameter (e)
5.3.3 Mechanisms ofDissection
andCountermeasures
Fig. 5.15 Causes of dissection. If a balloon with a diameter matching
the luminal diameter of an intact segment of a straight vessel is inated
across a lesion (a), the intact vessel wall will only just come into contact
with the balloon and will not be injured (b). In contrast, the intact part
of the vessel can be injured if the balloon has a larger diameter than the
luminal diameter of the intact segment (c). In a curved vessel, even a
balloon with a diameter matching the luminal diameter of the intact
segment will apply greater stress on the vessel wall at its edges and can
cause injury to the larger curvature of a bend (d, e)
The previous subsection discussed the risk of dissection
during angioplasty with a balloon when the distal marker is
located in a segment distal to the lesion. However, dissection can also occur by other mechanisms during PCI, which
means that precautions and countermeasures for dissection
due to various mechanisms should be devised.
1. If the coronary artery distal to a lesion is vulnerable or
contains plaque that is continuous from the stent landing
zone, dissection is likely to occur at the distal edge of a
stent/balloon. The risk of dissection is particularly high
for the coronary segment distal to a CTO that has become
vulnerable (due to lack of exposure to blood pressure) and
also contains plaque.
2. It is well-known that balloon angioplasty can rupture ste-
notic plaque, causing controlled dissection, but local dissection may sometimes propagate distally during balloon
angioplasty. To prevent this, the balloon should be inated
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b
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slowly to minimize intima-media separation. Before performing POBA, you should identify hard lesions with a
5.3.4 Scoring andCutting Balloon
Angioplasty
risk of propagating dissection and create longitudinal
cracks in the lesion by rotablation or scoring balloon
angioplasty. Dissection associated with longitudinal
cracks is unlikely to propagate distally (Fig. 5.17a). In
contrast, transverse dissection creates a blind end that is
subject to stress from blood ow and thus is likely to
propagate distally or even occlude the vessel (Fig.5.17b).
3. A very high rate of dissection was reported after angioplasty with a previously available balloon. This balloon
was found to have a very low slipperiness. In a vessel with
irregular walls, parts of the balloon may have become
adherent to the walls during ination, after which further
ination of the balloon may have placed excessive stress on
the vessel that led to dissection. Since all currently available balloons have improved slipperiness, dissection is
unlikely to occur by this mechanism. However, the risk of
dissection is increased by inating the balloon too rapidly.
The balloons available for these procedures (Lacrosse
NSE, ScoreFlex, and AngioSculpt) have distinct characteristics. Since creating longitudinal cracks permits the
vessel wall to expand radially, I prefer to use scoring balloons that purely create longitudinal cracks. Specically,
I almost always use the Lacrosse NSE balloon because of
its good crossability and the effectiveness of the pattern of
cracks it creates.
The Lacrosse NSE balloon creeps forward and it can
be advanced little by little without pushing forcibly. Even
if a Lacrosse NSE balloon is stopped at the entrance of
a stenosis, pre-dilating the lesion will allow it to creep
forward if the scoring elements at the tip can be wedged
in the lesion. If the tapered tip of this balloon distal to
the distal marker can be inated to the same shape as its
proximal part, this indicates that the balloon will be able to
creep forward again (Fig.5.18a). Thus, this balloon has to
be inated until it is able to creep forward. If the balloon
has been inated sufciently, it can usually be advanced
little by little without pushing it forcibly. If the distal
part is not inated to the same shape as the proximal part
(Fig.5.18b), it is probable that the body of the balloon has
not yet crossed the lesion.
If scoring angioplasty with a Lacrosse NSE balloon is not
effective, cutting balloon angioplasty should be attempted.
When cutting balloon angioplasty is performed, the cutting
balloon must not be pushed forward either. Due to the risk
of destroying the blade or bursting the balloon by injury due
to the blade, performing rotablation or high-pressure balloon
angioplasty should be considered prior to cutting balloon
angioplasty.
Fig. 5.17 Longitudinal versus transverse dissection. Unlike a longitu-
dinal dissection (a), a transverse dissection (b) is subject to stress from
blood ow that may enlarge the dissection or cause occlusion of the
vessel
Fig. 5.18 Advancing a Lacrosse NSE balloon catheter. When the
tapered part of a Lacrosse NSE balloon (indicated by the arrows) is
fully inated, the balloon can creep forward (a). Conversely, poor ination of the tapered part indicates that it will be difcult for the balloon
to cross the lesion (b)
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5 Mitsudo’s Non-pushing PCI Techniques
5.4 Use oftheRotablator
At my center, rotablation is primarily indicated for debulking lesions with circumferential calcication or lesions that
cannot be dilated sufciently by balloon angioplasty (residual indentation of the balloon). Two rotablation guidewires
are available, which are the RotaWire Extra-Support and
RotaWire Floppy.
5.4.1 Tornus andRotaWire
Most of the lesions that need debulking with a Rotablator
can only be crossed by the Tornus catheter. It is very difcult
to pass a RotaWire Extra-Support through a Tornus catheter.
Although this may sometimes be achieved in a straight vessel, it is usually impossible to advance a RotaWire ExtraSupport through a Tornus catheter despite pushing and
rotating it. However, a RotaWire Floppy can be advanced
into a Tornus catheter by rotating it. To facilitate rotation and
advancement, instead of attaching a clip to the guidewire
(Fig.5.19a), I attach a torquer (Fig.5.19b). Attempts to forcibly push a RotaWire guidewire can easily result in kinking
at the point of obstruction.
5.4.2 Debulking aLesion ataBend
If the lumen distal to a hard stenosis at a bend in a coronary artery is only slightly narrowed, the rotablation burr
may become stuck immediately after crossing the lesion
and be difcult to withdraw. This is likely to occur with
the RotaWire Floppy, but is rare with the RotaWire ExtraSupport. Therefore, the RotaWire Extra-Support should be
used when debulking a severe stenosis located at a bend.
5.4.3 Reducing Guidewire Bias andBurr Bias
When a RotaWire, especially the RotaWire Extra-Support,
passes through a bend in a vessel, the wire becomes biased
toward the inner curvature of the bend (Fig. 5.20a). This
inward guidewire bias may offset the outward bias of the
burr. On the other hand, the burr shows bias toward the outer
curvature that is opposite to the guidewire bias (Fig.5.20b).
If the guidewire passes through two bends in a vessel, the
effect of crossing the rst bend may bias the burr toward the
inner curvature of the second bend.
The situation becomes complicated when the target
vessel has two or more bends. As shown in Fig. 5.21a,
Fig. 5.19 Difculty in advancing the RotaWire without rotation. (a) A clip can easily be attached to the RotaWire, but is of limited usefulness for
rotating the wire. (b) A torquer can rotate the wire efciently and help to advance it
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the guidewire is biased toward the inner curvature of each
bend. In contrast, the burr is biased toward the outer curvature of the rst bend as a reaction to the guidewire bias, but
this bias of the burr amplies the guidewire bias at the second bend (Fig.5.21b). If the guiding catheter is oriented so
that guidewire bias at the rst bend becomes equivalent to
that at the second bend, the burr directs the guidewire bias
toward the outer side, tending to eliminate the guidewire
bias (Fig.5.21c).
Performing rotablation with a biased burr will eventually result eccentric debulking of the lesion, and it will
need to be entirely stented. It is sometimes difcult to
deliver a stent to such a lesion, but it can be effective to
use the child-in- mother technique to advance the stent
part of the way.
a
b
Fig. 5.20 Using the RotaWire Extra-Support when debulking a lesion
at a bend. The guidewire is biased toward the inner curvature of the
bend (a), while the burr passes along the outer curvature (b)
a
b
c
Fig. 5.21 Advancing the RotaWire across two bends. The burr is
biased toward the outer curvature of the rst bend, and this burr bias
amplies the guidewire bias toward the inner curvature of the second
bend (a, b). Changing the orientation of the guiding catheter can reduce
guidewire bias at the second bend (c)
5.4.4 Advancing aBurr
You can advance a rotablation burr into a stenosis by (1) lightly
pressing the burr into the entrance of the lesion for several seconds or (2) repeatedly approaching the entrance with a pecking
motion of the burr. I prefer to use the former method because the
burr seems to follow the operator’s intentions better, although
there is no denite evidence to support this choice. You should
advance the burr very slowly while running it at a constant rate
of not less than 5000rpm. In this context, I may add that you
should not vibrate a balloon like a pecking motion when delivering it and must not vibrate a stent when delivering it.
5.5 ELCA
We assessed the benet of ELCA in 116 patients undergoing PCI at my center during the period from 2001 to 2008.
Among these 116 patients, 101 patients had CTO and 98 of
them underwent 0.9-mm ELCA. ELCA was indicated for
debulking of CTOs that could be crossed by a guidewire, but
not by a balloon catheter.
After the introduction of retrograde PCI in October 2005,
our use of ELCA declined dramatically and reached zero in
2008. A retrograde guidewire that has crossed a CTO can be
introduced into the antegrade guiding catheter and trapped to
create a guidewire loop, so that a retrograde microcatheter
can almost always track the collateral channel and cross the
CTO.If a retrograde microcatheter has crossed the CTO, an
antegrade microcatheter or balloon catheter can also almost
always cross the CTO.Thus, use of the 0.9-mm laser catheter for treating CTOs has been abandoned.
Since ELCA was recently approved for coverage by the
national health insurance scheme in Japan, its benet for the
treatment of thrombotic occlusion has been reappraised. The
importance of non-pushing PCI techniques should always
be kept in mind when treating thrombotic occlusions. Since
a thrombotic occlusion is soft, it can be readily crossed by
advancing a laser catheter. However, you should always bear
in mind that rapidly advancing a laser catheter is not a good
idea. There is a risk of inadvertently pushing the catheter forward too vigorously.
A single laser energy pulse of up to 80 J only ablates
0.05mm of tissue. At the maximum frequency of 80 pulses/
sec, a laser catheter can only be advanced at a speed of
4.0 mm/s. Advancing the laser catheter more rapidly than
4.0mm/s involves utilization of mechanical energy in addition to laser energy.
It may be considered reasonable to push the ELCA catheter to help it cross the CTO, but pushing will considerably
reduce the ability to ablate soft tissue.
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5.6 Stenting
5.6.1 General Precautions forStenting
5.6.1.1 Lesion Preparation
The two objectives of preparing a lesion for stenting are (1)
to facilitate smooth delivery of the stent to the target location
without the need to apply force strong enough to deform the
stent and (2) to dilate the lesion sufciently to ensure optimal
stent expansion.
To facilitate smooth stent delivery, it is most important
to dilate the lumen of the lesion to a sufcient diameter for
delivering the stent. In addition, lesion preparation should
eliminate luminal irregularities. In particular, irregularities
that create indentations visible in the short axis view on the
larger curvature of a bend in the target vessel can interfere
with advancement of a stent (Fig. 5.22a). In contrast, an
irregularity that can only be seen in the long axis view will
not block advancement of a stent (Fig.5.22b).
How can a lesion be prepared sufciently for optimal
stent expansion? A stent can exert a maximum resistance
of 3kPa (3atm) to prevent recoil of the surrounding vessel
walls, which means that any stent can be deformed when
compressed by vascular recoil with a force greater than
3atm. It is well-known that a lesion should be pre-dilated
until the balloon is fully inated to eliminate all indentations.
Thus, lesion preparation with balloon angioplasty (nominal
pressure: 3atm) is theoretically inadequate if any indentation remains in the balloon, although this has not been tested
for economic reasons. To ensure optimal stent expansion,
the vessel wall at the lesion needs to be made redundant (to
reduce recoil).
Effective methods of adequately preparing a lesion for
smooth stent delivery and optimal stent expansion include
(1) debulking with a Rotablator, (2) scoring balloon angioplasty, (3) high-pressure balloon angioplasty, and (4) sufcient POBA.
POBA alone can prepare a stenotic lesion with soft
brous plaque or lipid-rich plaque, while high-pressure balloon angioplasty may be required for a calcied lesion or a
lesion with harder brous plaque. With a very hard lesion,
scoring balloon angioplasty (e.g., Lacrosse NSE) can be
performed to create cracks in the calcied or hard brous
plaque, thereby reducing vascular recoil after balloon angioplasty. A calcied lesion that is too hard for scoring balloon
angioplasty or that resists delivery of the scoring balloon
should be debulked with a Rotablator.
1. The debulking devices available include ELCA and the
Rotablator. Debulking with a Rotablator is most effective
for preparing a calcied lesion for stent implantation.
Rotablation can enlarge the lumen and also reduces the
vascular burden of calcication and thus decreases rigidity of the vessel wall.
2. A lesion that seems difcult to dilate sufciently by highpressure balloon angioplasty even after debulking with a
Rotablator should be scored with a Lacrosse NSE balloon. After performance of scoring balloon angioplasty,
such a lesion will be easier to dilate by relatively lowpressure balloon angioplasty.
3. Adding high-pressure balloon angioplasty to scoring balloon angioplasty will fracture calcied plaque, thereby
creating vessel wall redundancy and reducing recoil.
a
b
Fig. 5.22 Differences of luminal irregularities. Luminal irregularities
on the larger curvature that appear to be similar in the long axis view
may have a different distribution in the short axis view. Irregularities on
the larger curvature that can also be seen in the short axis view may
interfere with stent delivery (a), whereas irregularities only seen in the
long axis view will not (b)
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b
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5.6.1.2 Diculty withStent Delivery: Predicting
andAvoiding Problems
After apparently sufcient lesion preparation, it may still
prove difcult to advance a stent during PCI.This is probably due to residual luminal irregularities after balloon angioplasty (Fig.5.23a).
Difculty delivering a naked stent can often be predicted by difculty with delivering a balloon for lesion
preparation. I use the child-in-mother technique (e.g.,
GuideLiner) if I encounter difculty in advancing a balloon or if it becomes blocked after high-pressure balloon
angioplasty.
Fig. 5.23 Lesion at a bend with calcied plaque. (a) Sufcient dilata-
tion of a lesion with calcied plaque can enlarge the lumen, but may
cause dissection or indentation at the edge of the plaque that inhibits
stent advancement. (b) Additional high-pressure balloon angioplasty
may further enlarge the dissection or indentation at the edge of the calcied plaque, which may preclude stent delivery
5.6.1.3 Stent Delivery Strategy Based
onthePattern ofDiculty withDelivery
A stent that appears to be deliverable may become blocked
and difcult to advance into the target lesion. If this happens,
I choose the optimal stent delivering strategy according to
the pattern of difculty with delivery. I never push the stent
hard or push it in while wiggling it. If it suddenly becomes
impossible to advance a stent immediately after feeling that
it was deected, attempts to push the stent further are likely
to deform it. It is safer and more reliable to advance the stent
via a child catheter in order to bypass luminal irregularities.
If you notice that advancing a stent gradually becomes
more difcult until it is completely impossible to move it
further, you must not increase the force applied to the stent.
In this situation, pushing hard on the stent will not help to
advance it. Rather, some struts will be deformed at the edges
or in the body of the stent, wherever friction is greater, eventually making the stent undeliverable to the landing zone.
Instead, you should continue to apply the same force to stent
delivery catheter as that which advanced it before, which
will result in slight deection of the shaft of the stent delivery catheter (Fig.5.24a). If you then pull the catheter back
slightly to eliminate the deection and apply the same force
again, the stent will advance a little (Fig.5.24b).
This maneuver will achieve delivery of the stent into a
short lesion, but may not prevent it from becoming stuck again
in a long lesion. If the stent again stops advancing, it should
be pulled back to eliminate deection of the shaft and then
pushed in again to advance it slightly. Such alternating pullback and advancement of the stent will eventually achieve
delivery. This is the safest and most reliable method, although
it is time-consuming. However, if it becomes completely
impossible to advance the stent after repeating this maneuver
two or three times, the best option is to slowly withdraw the
stent and switch to stenting via the child-in- mother technique.
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Fig. 5.24 When a stent is difcult to deliver. (a) To deliver a stent into
a difcult lesion (e.g., a lesion with calcied plaque), it should be push
in with slight force to deect the shaft of the stent delivery catheter. (b)
Then the catheter should be pulled back slightly to eliminate deection
of its shaft and slowly advanced again. This maneuver may help to
bypass the obstruction and allow advancement of the stent. If the stent
becomes obstructed again, this maneuver should be repeated. If several
repetitions cannot achieve stent advancement, the stent should be withdrawn and then advanced via a child catheter. However, the stent should
never be pushed in forcibly
5.6.1.4 Other Strategies
In recent years, the abovementioned strategy has been widely
used to deliver a stent into a difcult lesion. In addition, the
strategies discussed in previous chapters (e.g., the buddy wire
technique, buddy balloon technique, slip-through technique,
and trapping technique) are also effective. These techniques
are worth trying if another guidewire has crossed a distal
bifurcation lesion or an additional guidewire is available.
However, a forcible attempt to advance an additional guidewire may fail or may cause deformation of a stent that has
not been completely protected, so is questionable whether
an additional guidewire should be inserted to facilitate stent
delivery. The child-in-mother technique may be safer and
more reliable for delivering a stent into a difcult lesion.
soon after performance of positioning CAG, the stent may
advance further during expansion. After a stent has been
advanced to the target, the stent delivery catheter should be
pulled back slightly (so as to only straighten its shaft while
not withdrawing the stent) before positioning CAG is performed. Whenever there is an interval between positioning
CAG and stent deployment, positioning CAG (uoroscopy)
should be repeated immediately before inating the SDB.
5.6.2 Using aConformable Stent
5.6.2.1 What Is aConformable Stent?
As is the case for bifurcation stenting, it is better to use a
conformable stent for general coronary artery stenting. A
conformable stent is preferred for the following four reasons:
(1) less edge effect, (2) a low risk of fracture, (3) the ability to
only apply bending stress to the vessel after fracture occurs
at a link, and (4) less edge effect at the fractured stumps.
What makes a stent conformable? As shown in Fig.5.25,
less stress is produced when conformable stent is bent, so that
it can be longitudinally expanded on the larger curvature and
compressed on the smaller curvature. Thus, “conformability” of a stent is a synonym for “longitudinal deformability.”
Particularly for bifurcation stenting, I prefer to use stents
with fewer links (such as the Wiktor, GFX, S-6, S-7, Driver,
S-stent, Nobori 3.5-mm, Element, and Integrity), as stated
previously. I rarely use the Cordis and CrossFlex stents
because the radio-opacity of the former is too high and the
proximal part of the latter shows suboptimal expansion.
5.6.1.5 Stent Positioning
Before stably positioning a stent that has been delivered into
a lesion, CAG should be performed to conrm that the distal
edge of the stent has reached the target. If CAG takes too
long, a stent that has reached the target will often move further before deployment and expansion. Even if it is expanded
Fig. 5.25 Design of a conformable stent
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5.6.2.2 Points toConsider
Based on the nding that stents with fewer links are more
likely to undergo deformation, I have made efforts to develop
techniques for successfully placing such stents without
deforming them. I take great care to prevent deformation of
stent struts by a balloon during its advancement into the SB
of a bifurcation lesion or by the exit port of an IVUS catheter during withdrawal. I consider that the interventionalist is
required to maintain the original shape of an implanted stent
by using various techniques. However, stent deformation by
other devices under the abovementioned circumstances is
often localized and sometimes undetectable by CAG.Hence,
stent deformity may often be overlooked during PCI.
The PROMUS Element is a two-link stent composed of
eight short crowns, with struts linked by short oblique peakto- valley interconnections and thus aligned in the identical
phase. This conguration prevents overlap between adjacent
struts and helps to achieve good conformability (longitudinal
deformability) of the stent (Fig.5.26).
Since I began to use the PROMUS Element stent, I have
failed to prevent deformation several times despite taking
great care during delivery, while its high conformability has
deeply impressed me. Since I considered it my mission or
raison d’etre to safely place this highly conformable stent
without deforming it, I reviewed six cases of stent deformation among over 200 cases of coronary artery stenting to
identify risk factors for stent deformation.
These six cases included the following: (1) a severely
tapered lesion (Fig. 5.27), (2) a tapered lesion in a highly
angulated vessel (Fig. 5.28), (3) an aorto-ostial lesion
(Fig. 5.29), (4) a bifurcation lesion with a large-diameter
proximal MB (Fig. 5.30), (5) a severely calcied lesion
(Fig.5.31), and (6) a lesion recanalized by stenting a false
lumen (Fig.5.32). In all of these lesions, a balloon for postdilatation or SB dilatation had to be advanced into or across a
stent with some struts that had not been apposed. The risk of
stent deformation appears to be particularly high for lesions
at a bend in the vessel or ostial lesions. Signicant irregularity of the stent lumen (e.g., after deployment in a severely
calcied lesion) or the balloon surface creates severe friction
during balloon advancement, which can be another risk factor for stent deformation.
Such longitudinal deformation results in the struts
being pushed together or pulled apart after stent deploy-
ment. Why is sufcient force to cause deformation applied
to the stent? This primarily occurs because a stent strut
or link has obstructed another device (Fig. 5.33). When
additional force is applied to advance the device, the strut
is very likely to undergo severe deformation. Accordingly,
you should not attempt to push a device forward after hitting a stent strut and should take other measures that help
to bypass the strut. In a tortuous vessel, in particular, even
the tip of a balloon introduced to improve apposition of
the proximal part of a stent is likely to hit a non-apposed
strut (Fig.5.34). In this situation, even slight application of
force can cause severe deformation of the stent. To avoid
such deformation, it is important to place the stent so that
its struts will not be hit by other devices during the subsequent steps of PCI, such as delivery of the post-dilatation
balloon.
I have encountered little stent deformation since I adopted
several techniques (both old and new) to prevent collision of
other devices with the struts and to eliminate these risk factors for deformation.
Fig. 5.26 PROMUS Element stent. At a bend in the vessel, the
PROMUS Element stent applies less stress to the vessel wall as it can
be longitudinally expanded on the outer curvature of the bend and compressed on the inner curvature
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Fig. 5.27 Stenting an LAD lesion (a). Low-pressure ination of the
SDB to the target vessel diameter has not achieved optimal stent expansion at the point indicated by an arrow. When the stent delivery catheter
was pulled back slightly, only the proximal marker moved and the distal
marker did not, indicating that the stent has been shortened (b). Immediate
withdrawal of the stent delivery catheter would establish deformation
(shortening) of the stent and preclude delivery of a post- dilatation balloon. On the other hand, readvancing the stent delivery catheter resolved
shortening of the stent due to its high conformability (c). Then the SDB
was inated slowly until all indentations were eliminated (d)
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Fig. 5.28 LCX bifurcation lesion. After bifurcation
stenting, an IVUS catheter was advanced into the stent
and caused deformation of the stent edge on the larger
curvature of the bend (arrow) due to proximal
malapposition
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Fig. 5.29 Stenting an RCA lesion in a patient with acute coronary syndrome. Due to severe tortuosity of the RCA, the tip of a post-dilatation
balloon contacted the stent as it was being advanced and caused shortening of the stent (arrow)
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