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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3585_Библиотеки_им_академика_М_И_Перельмана
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2 Stenting ofBifurcation Lesions
Balloon Ination
1. Initially inate the kissing balloons at a relatively low
pressure of about 8 to 10atm to expand the stent into a
shape compatible with the bifurcation (Fig.2.53).
2. If the proximal MB has not been dilated with a largediameter balloon (POT), the proximal ends of the two
kissing balloons must be positioned at or proximal to the
proximal edge of the MB stent, and the two balloons must
not overlap beyond the proximal edge of the stent
(Fig.2.54). If the proximal ends of the two kissing bal-
Fig. 2.53 Kissing balloon
ination using a male-male
connector. Use of a male-male
connector with KBI permits
synchronous ination and
deation of multiple (2–3)
balloons at equal pressures.
This is a cost- and laborsaving procedure, since the
interventionalist can operate
the indeator without an
assistant.
loons are distal to the proximal edge of the stent, ination
will lead to suboptimal expansion and malapposition of
the proximal part of the stent (Fig.2.54e). Also, the balloon surfaces will become irregular after ination and
deation, so a balloon may get stuck in the proximal part
of the stent and deform it during subsequent withdrawal of
the two balloons.
3. After KBI, only inate the SB balloon at a sufcient pressure to dilate the SB ostium.
4. Perform nal KBI at a relatively low pressure.
Fig. 2.54 Dilating a
bifurcation and the proximal
MB.When performing POT
(a), the proximal end of the
balloon must be proximal to
the proximal edge of the stent
(b). After optimal POT, KBI
could be performed
adequately (c). If the proximal
part of the stent undergoes
suboptimal expansion (d or
e), one or both balloons may
get stuck on malapposed stent
struts and deform the stent
during withdrawal after
ination and deation. If a
short balloon cannot
sufciently expand the distal
part of the stent and cannot be
advanced into the stent, it
should be withdrawn and
rewrapped before attempting
readvancement
b
c
d
e
a
b
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2.3 Optimal Stenting Techniques forBifurcation Lesions
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Proximal Optimization Technique
The proximal optimization technique (POT) refers to dilating the proximal MB by inating an optimally sized balloon
in a stent placed from the proximal MB to the distal MB or
the SB (Fig.2.55).
The diameter of the proximal MB may be too large compared with the diameters of the distal MB and SB to achieve
optimal stent apposition in the proximal MB by only inating a stent delivery balloon. In such cases, you should inate
a balloon of the optimal size for the proximal MB only in this
segment (POT), and then perform SB rewiring before
KBI.Performing POT will prevent deformation of the proximal part of the stent by KBI.Ensure that the stent is positioned to cover more than 6mm of the proximal MB. To
minimize damage to the MB segment proximal to the proximal edge of the stent, the balloon should only be inated
within the stent and should not overlap the stent into the
proximal MB.Therefore, it is better for the stent in the proximal MB to be longer than the shortest balloon currently
available.
It is not always easy to achieve optimal positioning of the
balloon for POT.If a balloon with a tapered tip is used, it can
over-dilate and injure the ostium of the distal MB.A sandbagshaped balloon with a less tapered tip should be used and
positioned so that its distal marker is just proximal to the
carina (Fig.2.56). Even if slight stent malapposition occurs
near the carina, subsequent KBI can optimize apposition at
this site (which originally had an elliptical lumen).
b
Fig. 2.55 Proximal optimization technique (POT). (a) A stent placed
in the MB may not show optimal apposition in the proximal MB if the
diameter of the vessel is too large. (b) Subsequent ination of a balloon
with the correct size for the proximal MB only in this segment can
achieve optimal stent expansion and apposition. If the patient has a nonostial lesion, the balloon should be inated to a diameter compatible
with the stent landing zone in the proximal MB, while it should be
inated to the diameter of the proximal MB for an ostial lesion. If there
is a jailed guidewire, the ination pressure should not exceed 14atm, in
principle
Fig. 2.56 Balloons suitable for POT. (a) A balloon with a tapered tip
can injure the ostium of the distal MB because its tip may enter this
segment. (b) A sandbag-shaped balloon with a less tapered tip is suitable for POT
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Column 18 Necessity of Performing POT and KBI
2 Stenting ofBifurcation Lesions
When bifurcation stenting using POT is performed according to the following procedure, there may seem to be no need for KBI.
1. Implant a stent compatible with the diameter of the distal MB using the MB crossover technique.
2. Perform POT.
3. Perform SB wiring.
4. Dilate only the SB ostium.
However, I object to this procedure for the following reasons:
• While better mid-term outcomes have been reported for some stents (e.g., Cypher) without KBI than with KBI, this
does not mean that KBI should be absolutely avoided even with such stents.
• KBI should be performed proactively if the stent design permits culotte or provisional stenting to salvage a compromised SB after KBI and if the long- term outcome of PCI will be better than without KBI
• When employing KBI, the optimal stent needs to be selected and placed as sophisticatedly as possible in order to
safely accomplish optimal bifurcation stenting.
The disadvantages of not using KBI should also be considered, since bifurcation stenting without KBI theoretically
has the following disadvantages:
• Performing POT does not ensure optimal stent apposition at the carina and does not completely eliminate SB jailing.
If the POT balloon impinges on the distal MB, performing POT can cause carina shift toward the SB and injury of the
distal MB.The outcome of stenting plus POT alone is markedly different from that of optimal bifurcation stenting.
• Can these issues be overcome without performing KBI by only dilating the SB, i.e., by opening a cell for SB access
with a very short balloon? Even if inating a very short balloon can achieve optimal dilatation of the SB ostium, the
contralateral stent struts at the carina will be drawn toward the SB, just as when the SB is dilated by a long balloon
(Fig.2.57). Optimal stent apposition cannot be achieved without dilating the ostium of the distal MB.
• The risk of complications associated with KBI can be minimized by using a 2-link stent, by wiring the SB through
the most distal cell at the carina, and by optimizing the sizes of the kissing balloons and their ination pressures.
Fig. 2.57 Dilating only the SB with a balloon
after stent implantation. This procedure results in
malapposition of the contralateral stent struts
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2.3 Optimal Stenting Techniques forBifurcation Lesions
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Conrmation of Jailing and SB Rewiring
1. IVUS
IVUS is the best method to check for jailing after
KBI.You should advance an IVUS catheter into the MB and
estimate the extent of stent jailing from the edge of the
carina. If it is within 1mm, jailing may be considered acceptable. If it exceeds 1.5mm, you should always perform SB
rewiring.
2. SB rewiring using a Crusade catheter
• Crusade catheter advanced over the MB guidewire
(Fig.2.58)
You should advance a Crusade catheter over the MB
guidewire while maintaining the SB guidewire as a landmark. To ensure that the probing guidewire goes through a
cell just distal to the landmark guidewire, you should pull
the landmark wire back slightly and bring it into contact
with the proximal rim of the cell after placing its radiolucent part at the SB ostium. Then you should pull the probing guidewire back very gently and stop. If the probing
guidewire is distal to the landmark guidewire and if the
two wires are not in contact with each other, it is highly
probable that the probing guidewire has crossed the stent
through a cell at least one strut more distal to that of the
landmark guidewire.
• Crusade catheter advanced over the SB guidewire
(Fig.2.59)
You should advance a Crusade catheter over the SB guidewire (landmark) while keeping the probing guidewire within
the catheter. After conrming smooth entry of the Crusade into
the SB, you should withdraw it so that the side hole is in the
proximal MB and then advance the probing guidewire into the
distal MB.Subsequently, you should pull the guidewire back
while orienting its tip toward the SB and try to insert it into the
SB through a more distal cell. When the guidewire just enters
the SB, you should advance the Crusade a little. If the probing
guidewire has crossed the stent through a different cell from
that of the landmark guidewire, there will be at least one strut
between the tip of the Crusade and the probing guidewire delivered through its side hole, and this will prevent advancement of
the catheter beyond the carina. If the Crusade catheter does not
go beyond the carina, the probing guidewire may be considered
to have crossed the stent through a cell at least one strut more
distal to that of the landmark guidewire. If the probing guidewire has crossed the stent through the same cell as the landmark guidewire, the Crusade will readily go beyond the carina.
3. Final KBI
If SB rewiring through the most distal cell is considered
to be highly probable, you should perform nal KBI with
balloons chosen as described above using the abovementioned technique.
4. IVUS
Then you should repeat IVUS to conrm that the extent of
jailing is acceptable (≤1mm).
b
c
Fig. 2.58 SB rewiring using the Crusade microcatheter (advanced
over the MB guidewire). (a) Kissing balloon technique for suboptimal
side branch rewiring. (b) Side branch wire is in the more proximal cell
(c) Advance a Crusade catheter over the MB guidewire to the distal MB
d
and pull the probing guidewire back together with the catheter. (d) If the
probing guidewire is distal to the landmark guidewire and if the two
wires are not in contact with each other, it is highly probable that the
probing guidewire has crossed the stent through a more distal cell
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2 Stenting ofBifurcation Lesions
fed
g
Fig. 2.59 SB rewiring using the Crusade microcatheter (advanced
over the SB guidewire). (a) Kissing balloon technique for suboptimal
side branch rewiring. (b) Side branch wire is in the more proximal cell.
If the probing and landmark guidewires have crossed the stent through
different cells (c, d), the Crusade catheter will never go beyond the
2.4 Ideal Double Stenting ofBifurcation
Lesions
The controversy over the choice between single and double
stenting is generally relevant to bifurcation lesions, for which
both strategies appear to achieve equally good short-term
outcomes. It is true that only double stenting can achieve
favorable short-term results in some bifurcation lesions.
What is the ideal double stenting method for bifurcation
lesions? To achieve ideal double stenting for a bifurcation
lesion, what stent design, wiring strategy, device strategy,
and dilatation/deployment strategy should be used?
Section 2.2 of this chapter provides diagrams of the ideal
scaffold for bifurcation lesions which also involve the SB
(see Fig.2.60 [p. XX]). Figure2.60a depicts a single stent, as
we cannot rule out the possibility that one stent may be optimal for bifurcation lesions. Although the gure legend does
not specify whether this bifurcation scaffold can be con-
h
i
KBI : 3.0 mm, 2.5 mm
carina (f). If the two guidewires have crossed the stent through the same
cell, the Crusade will readily go beyond the carina (e). (g) SB rewiring
after placing a stent from Segment 3 to Segment 4in the RCA. (h) KBI.
(i) To overcome severe jailing, SB rewiring is done with the aid of a
Crusade catheter advanced over the SB guidewire
structed with one or two stents, at least two stents are needed
currently, and two-stent or three-stent methods have been
proposed for handling bifurcation lesions. Here, I will discuss how closely these methods correspond to the ideal
method.
2.4.1 Comments onVarious Two-Stent
Methods
The key to procedural success with provisional T-stenting,
modied T-stenting, mini-crush stenting, or sleeve stenting is
to accurately position the SB stent without its struts entering
the MB and without a gap between the two stents. One of the
problems with all of these stenting techniques is creation of
a gap between the stents, particularly at the shoulder of the
SB.When performing provisional T-stenting, you can minimize the risk of creating such a gap by placing the SB stent
a
c
b
a
c
b
2.4 Ideal Double Stenting ofBifurcation Lesions
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195
exactly from the SB ostium while maintaining the option to
switch to culotte stenting if the proximal edge of the stent
protrudes into the MB. With provisional or modied
T-stenting, half of each strut ring in the proximal part of the
SB stent loses the support of the vessel wall, which may
reduce the radial strength of the stent (Fig.2.60).
If provisional T-stenting is performed at a large
(≥2.75mm) bifurcation with a small SB take-off angle, some
struts of the SB stent will show malapposition and fail to
contribute to the radial strength of the stent (Fig.2.61a). If
both the MB and SB are small, the distal struts of the SB
stent will protrude into the MB lumen more prominently
relative to the MB diameter (Fig.2.61b). If the branching
angle is larger, protrusion of SB stent struts into the MB
lumen becomes less prominent (Fig.2.61c).
When the sleeve technique is used (Fig.2.62), even if the
distal struts of the SB stent protruding into the MB lumen are
pressing on the MB wall, the struts oblique to the MB stent
may lose radial strength because the SB stent cannot show
optimal apposition to the walls of the SB while maintaining
its original zigzag structure (Fig.2.62b). At the ostium of the
SB, it is highly probable that the struts of the SB stent have
been distorted (Fig.2.62c). This is particularly likely if there
is a calcied lesion at the ostium of the SB.
With the V-stenting (SKS) technique, each stent will
always have insufcient radial strength in the proximal
MB. The principle of this technique also prevents optimal
stent apposition (Fig.2.63).
Culotte stenting (Fig. 2.64) is a relatively simple technique, which involves two cycles of stenting with
KBI. However, interventionalists often seem to think that
this technique is complicated and thus avoid it. Although the
two stents overlap in the proximal MB, proper deployment
of optimally designed stents will achieve complete stent
apposition and adequate radial strength while avoiding MB/
SB jailing. Therefore, culotte stenting is a near-optimal strategy for bifurcation stenting.
Fig. 2.60 Provisional T-stenting (a), modied T-stenting (b), and
culotte stenting (c). With provisional or modied T-stenting, the stent
may lose radial strength on the contralateral side
Fig. 2.61 Various T-stenting patterns. (a) If the bifurcation has a small
SB take-off angle, the SB stent struts protruding into the MB lumen are
unable to contribute to the radial strength of the stent. (b) If the bifurcation has a small MB and small SB, struts from the SB stent will protrude
into the MB lumen more prominently relative to the MB diameter. (c) If
the bifurcation has a large SB take-off angle, protrusion of SB stent
struts into the MB lumen becomes less prominent
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b
c
Fig. 2.62 Sleeve stenting. (a) Side branch stent is protruded to main
vessel. After the stent is returned to the SB, it is unlikely to preserve its
zigzag strut structure (b) and is likely to have been distorted (c)
2 Stenting ofBifurcation Lesions
Fig. 2.64 Culotte stenting. Culotte stenting allows complete stent
apposition and preserves high radial strength of both stents.
2.4.2 Culotte (Y) Stenting
2.4.2.1 Indications forCulotte Stenting
1. A true bifurcation lesion where stenting with KBI has
caused SB dissection with a risk of occlusion or resteno-
sis or signicant SB stenosis due to plaque or carina shift.
2. A bifurcation lesion with an extreme SB take-off angula-
tion that is likely to prevent SB stenting after MB stent-
ing. In this setting, upfront culotte stenting should be
planned so that SB stenting precedes MB stenting.
3. A bifurcation lesion where pre-dilatation has caused
severe SB dissection that is likely to prevent SB wiring
after MB stenting in provisional stenting. In this case, SB
stenting should precede MB stenting, with the intention
of performing culotte stenting.
Fig. 2.63 V-stenting. The radial strength of each stent is very low as it
depends on the strength of the contralateral stent struts.
ac
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2.4.2.2 Practical Approach toCulotte Stenting
1. Perform MB stenting with KBI as described above. If SB
wiring through the most distal cell has not been conrmed, assess the extent of jailing by IVUS. If jailing
exceeds about 1.0mm, try SB rewiring through a cell that
is at least one strut more distal. Perform KBI and then
check stent apposition by IVUS.
2. Place a stent in the SB. Note that stent size should be
compatible with the SB diameter at the ostium, e.g., if the
SB diameter at the ostium exceeds 4.0 mm, a 3.5-mm
stent should be placed and expanded by balloon ination
at low pressure.
3. Overlap the two stents in the proximal MB for a distance
of about 3 to 5 mm. If SB stenting is done before MB
stenting, place the proximal edge of the SB stent 3 to
5mm proximal to the carina. Cover the entire proximal
MB with the MB stent (Fig.2.65).
4. Advance the SB stent slowly and with great care so as to
prevent its distal edge from hitting the MB stent. If the
distal edge of the SB stent contacts the MB stent during
rapid advancement, the struts at the edge will be distorted
and damaged, so that it may become impossible to advance
the stent into the SB.It is important to advance the stent
into the SB slowly and gently, and you should never
attempt to push the stent in if it is blocked even slightly.
5. There are several ways of advancing an SB stent that has
been blocked by struts of the MB stent.
(a) When stenting the proximal MB (e.g., LMT), with-
drawal and advancement of the guiding catheter
should be repeated until its tip is as coaxial with the
SB ostium as possible.
(b) Slightly press the stent into the struts to deect the
stent delivery balloon a little, withdraw the balloon
catheter to straighten the deected part, and then
immediately push it in again (Fig.2.66).
(c) Insert another guidewire (buddy wire) to advance the
stent gently. If delivery of the stent is still not achieved
even after these procedures, advance the stent while
pushing the buddy wire forward after conrming the
safety of pushing in a wire with a prolapsed tip.
(d) Advance a buddy balloon along the buddy wire to
push in the stent with minimal force. Alternatively,
advance the buddy balloon rst and then gently push
in the stent.
6. It may become difcult to advance the stent or even to
withdraw it, if deformation occurs during any of the
abovementioned steps. There is a temptation to push
harder with the intention of advancing the stent “just a
little further,” but even a slight increase of force can easily
deform the stent, so you must not push a stent in. By using
the abovementioned procedures, you can almost always
deliver a stent. If all of these procedures fail, you can try
the mother/child guiding technique. This technique
involves introducing a child catheter into the affected
coronary artery by using an anchor balloon previously
introduced via the catheter and inated at a low pressure.
You should advance the child catheter very gently while
pulling the anchor balloon back to prevent coronary artery
injury and stent deformation by the catheter tip. The stent
can be delivered successfully if the catheter is advanced
so that its tip is just distal to the carina.
7. After placing a stent in the SB, perform KBI by the same
method as that for initial stenting with KBI.For in-stent
dilation, use an optimally sized (not oversized) semicompliant balloon inated to a relatively high pressure. If
necessary, perform nal KBI with noncompliant balloons
inated to a relatively high pressure.
Fig. 2.65 Stent implantation
for culotte (Y) stenting. (a)
Place a stent in the SB.Limit
the protrusion of struts into
the MB to about 3mm. (b)
After KBI. (c) Place a stent in
the SB. (d) After KBI
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Fig. 2.66 Measures to take if
the balloon tip is blocked by
stent struts (a). (b) Never
forcibly push the stent
delivery balloon (SDB)
catheter, but slightly press the
stent into the struts to deect
the tip of the SDB a little. (c)
Pull the catheter back slightly
to straighten the tip of the
SDB and promptly push it in
a little way. This may allow
smooth stent delivery into
theSB
2 Stenting ofBifurcation Lesions
cb
Stenting ofRCA Ostial Lesions
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3
PCI of RCA ostial lesions has long posed a challenge for
interventional cardiologists for the following two reasons:
(1) the RCA ostium is too rigid to be dilated successfully and
is likely to show severe recoil, resulting in a high restenosis
rate, and (2) stent fracture and restenosis occur frequently at
the region several millimeters from the ostium.
The high rigidity and recoil of the RCA ostium have been
attributed to the sphincter-like arrangement of myolaments
in the aorto-ostial smooth muscle, while prominent movement of the aorto-ostial junction has been suggested to contribute to the high frequency of stent fracture and restenosis
after stenting at this site.
3.1 Radial Force
When a vessel is poorly dilatable and likely to recoil after
stenting, how strong does the resistance of the stent to radial
force (i.e., its radial stiffness) need to be in order to support
the vessel wall and prevent “stent recoil” (actually vascular
recoil)?
Before discussing this question, it is important to conrm
how strong a stent can be. Although this depends on the denition of radial force and the method of measuring it, let us
assume a stent is implanted in a silicone tube immersed in
water and consider what will happen if the water pressure is
increased. With an increase of the external pressure, the stent
will change shape and its diameter will gradually decrease.
When the pressure reaches a certain level, the stent will
abruptly collapse. This is referred to as the buckling point
(radial strength). If the water pressure at the buckling point is
dened as the radial strength of the stent, resistance to a
radial force of about 2atm (2000hPa) may be regarded as
adequate. If so, a stent with “adequate” radial strength would
show “recoil” due to vascular compression at a pressure
greater than 3atm. If it was implanted in a lesion that was
pre-dilated at 16 atm or could only be post-dilated at
≥22 atm, the stent might be compressed at ≥3 atm after
post-dilatation.
When IVUS is performed after stent implantation, it
shows adequate dilation of many lesions, and follow-up
angiography rarely shows stent lumen loss. This means that
compression of the stent (due to recoil of the vascular wall)
is often no more than moderate. Nevertheless, compression
of about 3atm may readily be applied to the stent in the presence of severe brosis or calcication of the vascular wall. In
fact, vascular recoil often occurs at the RCA ostium even
after pre- and post-dilatation at an adequate pressure for
eliminating balloon indentations.
In such situations, the vessel may be regarded as having a
recoil force of about 2 to 3atm. Recoil of such a vessel may
be preventable by placing a stent with adequate resistance to
compression. However, a vessel with rubberlike recoil after
being dilated by balloon ination at high pressure (without
the balloon popping out) will probably compress the stent
with a force much larger than its radial strength. A stent with
low to medium radial strength cannot be an adequate scaffold for such a vessel. Unfortunately, all attempts to
strengthen the scaffold (e.g., by using a stent with a larger
radial strength or overlaying two stents) and prevent restenosis at the RCA ostium have failed, as was theoretically predicted before these attempts. Hence, the consensus has been
reached that strengthening the scaffold is useless for lesions
with a hardness exceeding a certain threshold, while adequate lesion preparation to attenuate the recoil force of the
vessel is much more practical.
3.2 Lesion Preparation
Therefore, we need to consider how a hard lesion should be
prepared to attenuate vascular recoil and to make the vessel
wall redundant like that at a soft lesion. Although the same
principles apply to hard non-ostial lesions, the situation at
the RCA ostium is special.
Some calcied lesions can be successfully debulked by
rotablation, cutting balloon angioplasty, or directional coronary atherectomy (DCA). However, the DCA system is
© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
K. Mitsudo, Non-Pushing PCI Techniques, https://doi.org/10.1007/978-981-15-7043-8_3
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