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1.6 Antegrade Approach
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If you can conrm that the guidewire has crossed the
occlusion through the true lumen, you should advance a
microcatheter over the guidewire, exchange the guidewire
for another with a less stiff tip, and deliver the appropriate
devices to dilate the lumen. If collateral imaging fails to
provide clear conrmation that the guidewire has crossed
the occlusion through the true lumen, you should check for
free backow of blood from the microcatheter after withdrawing the guidewire and then perform tip injection. After
conrming that the guidewire crossed the CTO through the
true lumen, you should record the conrmation.
1.6.5 Microcatheter
You must always use a microcatheter to assist the guidewire in crossing a CTO.Using a microcatheter allows you
to exchange guidewires and to nely adjust the orientation,
movement, and backup of the guidewire.
1.6.5.1 Selection oftheMicrocatheter
Which microcatheter should be chosen for antegrade PCI?
The minimum requirement to be met may be the ability to
improve the manipulability of the guidewire more. In particular, friction between the microcatheter and guidewire needs
to remain relatively constant, even after passing through a
very tortuous vessel (Fig.1.131).
In addition, the microcatheter needs to have a tip that can
easily enter an occlusion when advanced over a guidewire.
To meet this requirement, the microcatheter should have a tip
that is as small as possible and a shaft that is as slim as possible. A microcatheter with superior crossability even with
rotation is better. A desirable microcatheter can be used to
advance a Conquest Pro 12 or another guidewire that has
a high tip load without perforation of the microcatheter by
the guidewire tip, even when the tip is located at a curve
of the target vessel. There is no ideal microcatheter among
the many currently available, so the optimal microcatheter
should be selected depending on the morphology and hardness of the target lesion.
Fig. 1.131 CTO of an RCA with a very tortuous proximal segment. In this situation, using a soft microcatheter will cause greater friction with
the guidewire and reduce its manipulability
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1.6.5.2 Position oftheMicrocatheter Tip
When manipulating a guidewire toward a CTO through a
microcatheter, you should place the tip of the microcatheter near the entrance of the occlusion. Positioning the tip of
the microcatheter about 5mm from the entry will improve
backup for the guidewire. However, if the distance is too
short, the microcatheter will bias the guidewire toward the
larger curvature of a curved vessel and increase the risk of
guidewire whipping. You may approximate the microcatheter tip to the CTO entry if stronger backup is absolutely
necessary, but you should usually position the catheter tip at
1 to 1.5cm from the entry to ensure good manipulability of
the guidewire.
1.6.6 Device Delivery Strategy
After a guidewire has crossed a CTO through the true lumen,
you can deliver devices along the guidewire. To reduce the
risk of injury or perforation of the coronary artery segment
distal to the occlusion during device delivery, you should
exchange the CTO crossing guidewire for another guidewire. Before performing guidewire exchange, you should
rst advance a microcatheter along the guidewire.
Advancing this device is the only procedure during PCI
for which an interventionalist may use a strong pushing
force.
Because of good trackability, a microcatheter with a soft
tip may be able to cross a tortuous lesion that is relatively
hard, while a microcatheter with a stiff tip often fails to do
so, since the latter type of catheter can be advanced into a
hard CTO but cannot track a tortuous vessel.
The crossability of a microcatheter also depends on the
diameter of its shaft. A microcatheter with a slimmer shaft
can cross an occlusion more easily. One may think that a
microcatheter with a stiffer shaft provides stronger backup.
Considering the importance of reducing friction by rotating
the microcatheter to facilitate its advancement, a stiffer shaft
is better as it provides superior torque and greater resistance
to twisting deformation. Nonetheless, a microcatheter may
only be rotated to-and-fro several times.
Once a microcatheter has become wedged in an occlusion or tight stenosis and cannot be rotated further, continued
attempts to rotate it in the same direction will cause deformation of the shaft. It is very difcult to slide the guidewire
through such a deformed microcatheter. To withdraw the
microcatheter, it is also necessary to withdraw the guidewire
that has successfully crossed the lesion.
a
1.6.6.1 Microcatheter
For the reasons mentioned above, a microcatheter with
good crossability should be selected. The crossability of
a microcatheter is a function of the characteristics of the
lesion and the properties of the microcatheter tip. Here, I
will discuss a phenomenon that is particularly notable with
balloon catheters, but is also applicable to microcatheters.
In brief, it is difcult to cross a hard (e.g., calcied) occlusion using a microcatheter with a soft tip. This is because
the tip of a microcatheter tends to are out when blocked by
a hard obstruction (Fig.1.132a) and it will be deformed if
pushed forcibly (Fig. 1.132b). These changes substantially
increase the prole of the tip and make it more difcult for
the microcatheter to cross the occlusion. In contrast, if the
microcatheter has a stiff tip that is not easily deformed, it can
be advanced while deforming the lesion instead.
b
c
Fig. 1.132 Microcatheter with a small soft tip. When a microcatheter
with a small soft tip is pushed forward into a severely calcied hard
occlusion, the tip may are out (a) or be deformed (b). If the microcatheter crosses such a hard occlusion, its tip may be stretched when the
catheter is withdrawn from the lesion (c). The appropriate microcatheter for a severely calcied hard lesion should have a small stiff tip
1.6 Antegrade Approach
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1.6.6.2 Balloon Catheter
If a microcatheter fails to cross the occlusion, you should try
to deliver a semi-compliant balloon catheter with the smallest diameter feasible. As is the case for microcatheters, a balloon catheter with a stiff tip is more suitable for crossing a
hard straight occlusion, while a balloon catheter with a soft
tip is desirable for a tortuous lesion.
If a balloon catheter that has been advanced with sufcient backup fails to cross the occlusion, you should consider
the next strategy. Before proceeding to the next step, you
should withdraw the balloon catheter and inspect its tip. If
the tip is even slightly ared, cut off about 0.3mm using
sharp scissors (Fig.1.133), since the balloon catheter may
cross the occlusion without its ared tip. Instead of using a
new balloon catheter, I modify the rst catheter in this way
to save limited medical resources (see Chap. 2.3.4 “Delivery
of a Balloon Catheter for the Kissing Balloon Technique”
[page 186]).
Fig. 1.133 Modifying a
balloon catheter with a ared
tip. During attempts to
penetrate a severely calcied
hard occlusion with a balloon
catheter or to enter a side
branch through a stent strut,
the tip of the catheter may
become ared (a), and even
slight aring can interfere
with delivery. After the ared
tip is cut off with scissors (b),
the balloon catheter may
become able to cross the
lesion or pass the stent strut
ab
1.6.6.3 Anchoring
As mentioned in Sect. 1.3 (“Guiding Catheter”), anchoring
is very effective for stabilizing a guiding catheter, which can
easily become disengaged when a balloon catheter is pushed
in through it. I use an Amplatz left-type guiding catheter
(e.g., AL 1 ST) when performing PCI for CTO of the RCA,
and anchoring is sometimes necessary to stabilize this catheter because its curve does not always t the size of the sinus
of Valsalva. In this setting, the side branch used for anchoring may be the conus branch, sinoatrial node branch, right
ventricular branch, or atrial branch. The anchoring balloon
should be slightly oversized and should be inated at a low
pressure of about 4 to 6atm.
1.6.6.4 Tornus Crossing Catheter
If the occlusion is too hard to cross with a balloon catheter,
you can often use a Tornus crossing catheter instead. If the
guiding catheter is unstable even when using a Tornus cath-
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eter, you should maintain the anchoring balloon at its previous position to stabilize the guiding catheter. An anchoring
balloon with a diameter of 2mm or more can be used as a
trapping balloon during delivery and removal of the Tornus
catheter.
After delivering the Tornus catheter, you should exchange
the guidewire for a 0.014-inch extra support-type guidewire and try to advance a balloon catheter over the wire.
(Alternatively, you can exchange the guidewire for a oppy
RotaWire in order to perform rotablation.) If the balloon
catheter fails to cross the lesion, you should exchange it for
a Tornus catheter again and exchange the 0.014-inch guidewire for a oppy RotaWire to start rotablation (see Chap.
5.1.3 “Tornus Catheter” [page 245]).
1.6.6.5 Excimer Laser Coronary Angioplasty
(ELCA)
If a retrograde guidewire has crossed the occlusion, a loop
can be formed between the antegrade and retrograde guiding
catheters, which will almost denitely ensure successful deliv-
ery of the devices. If an antegrade guidewire has crossed the
occlusion, a loop cannot be formed until guidewire exchange,
so a balloon catheter or Tornus catheter may be unable to cross
the lesion. In such cases, a laser catheter with a diameter of
0.9mm can be used to perform angioplasty (excimer laser coronary angioplasty: ELCA). However, ELCA is not effective
for recanalizing a severely calcied lesion, and there is often
no choice other than to perform rotablation for this purpose.
1.6.6.6 Rotablator
To perform rotablation before device delivery, you have to
exchange the guidewire for a RotaWire through a microcatheter with its tip xed at the CTO entry point. If the microcatheter is advanced too far, its tip will become bent upon
withdrawal of the guidewire from the catheter (Fig.1.134),
and it will be impossible to orient the tip toward the entry
point. Therefore, when exchanging guidewires before rotablation, it is important to only press the tip of the microcatheter lightly against the CTO entry point.
a
Fig. 1.134 If a microcatheter is advanced into an occlusion, its tip
becomes bent on withdrawal of the guidewire. A microcatheter with a
guidewire inside it is relatively straight (a). Upon withdrawal of the
guidewire, the microcatheter (and its tip) becomes curved due to the
release of accumulated force (b). When advanced through a microcatheter with a slightly bent tip that has lost coaxiality with the occlusion, it
will be difcult for a RotaWire to follow the correct route. A microcath-
c
eter with a slightly bent tip can be reused after withdrawing it and
straightening the tip. However, a microcatheter with a severely
deformed and folded tip (c) can hardly be returned to its original shape.
Therefore, after its tip has been pushed into the occlusion, you should
pull a microcatheter back slightly to release the accumulated force
before withdrawing the guidewire from the catheter
1.7 Retrograde Approach
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1.6.6.7 Double or Triple Wires
In the past, I would deliver a device to the occlusion through
a lumen that was enlarged by using two or even three CTO
crossing wires. However, I have not employed this strategy
recently because the CTOs that I encounter have not required
or permitted it.
1.6.7 From Balloon Ination toStent
Placement
After device delivery has been achieved, balloon ination
may be performed. In general, you should dilate an occlusion by inating a small balloon (1.0 to 1.5mm in diameter)
and then perform observation by IVUS.The ballooning and
stenting procedures employed for CTOs are largely the same
as those for non-occlusive lesions, except that special care is
needed in case of crossing a false lumen and for preserving
a small side branch when treating double CTOs of the main
trunk and a larger branch. Please refer to IVUS-guided wiring in Sect. 1.7 “Retrograde Approach.”
1.7 Retrograde Approach
The “retrograde approach” is a term that has become widely
used since 2005, when Dr. Osamu Kato proposed a breakthrough strategy that he referred to as “controlled antegrade
and retrograde subintimal tracking (CART).” However, Dr.
Kato and colleagues actually started to employ retrograde
guidewires around 2000 to track a collateral channel and
reach the vessel distal to a CTO for use as a landmark when
navigating an antegrade guidewire through the occlusion.
Here I summarize the strategies that I include in the cat-
egory of retrograde PCI for CTO.
1. Direct retrograde crossing: This involves retrogradely
advancing a guidewire through a collateral channel to
reach the lumen of the target coronary artery distal to a
CTO and directly crossing the occlusion by using a retrograde CTO guidewire with the support of a microcatheter
for the proximal true lumen (Fig.1.135a).
2. Reverse CART technique: This involves navigation of a
retrograde guidewire to a space within a CTO that was
previously reached by an antegrade guidewire and
enlarged by a balloon and using the retrograde wire to
cross the occlusion (Fig.1.135b).
3. CART technique: This involves navigation of an antegrade guidewire to a space in the distal part of an occlusion that was previously reached by a retrograde guidewire
and enlarged by a balloon and using the antegrade wire to
cross the occlusion (Fig.
4. Antegrade CTO crossing: This involves placing the tip of
a retrograde guidewire in the distal part of a CTO and
using it as a landmark while crossing the CTO antegradely (Fig.1.135d).
5. Kissing wire technique: This involves advancing an antegrade or retrograde guidewire into a CTO and using it as
a landmark to navigate another guidewire across the
occlusion from the opposite direction (Fig.1.135e).
1.135c).
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a
b
c
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Fig. 1.135 Techniques for the
retrograde approach. (a) An
antegrade guidewire (landmark)
is not always required to
perform direct retrograde
crossing. As I attempt antegrade
PCI for CTO before switching
to the retrograde approach
whenever possible, I always
leave the antegrade guidewire in
position as a landmark for direct
retrograde crossing. (b) Reverse
CART technique. (c) CART
technique. (d) Antegrade CTO
crossing: A retrograde
guidewire is used as a landmark
for the distal true lumen. The tip
of the retrograde guidewire is
positioned just beyond the distal
end of the occlusion, (1) and an
antegrade guidewire is advanced
toward it (2). (e) Kissing wire
technique using a retrograde
guidewire as a landmark for the
distal true lumen. A retrograde
guidewire is advanced into the
occlusion (1), and then an
antegrade guidewire is
navigated toward the retrograde
wire (2)
1 Mitsudo’s PCI Techniques forCTO
proximal distal
d
Antegrade guidewire
Retrograde guidewire
e
1.7.1 Indications fortheRetrograde
Approach
the proximal end of the lesion to serve as a landmark. PCI is
contraindicated for occlusions resulting from coronary
ostial atresia. To rule out this possibility, you must perform
As mentioned above, I consider antegrade PCI to be the “primary intervention for CTO.” However, I think that retrograde
PCI can be indicated if there is a collateral channel that can
be tracked and if any of the following requirements are met:
CT angiography if there is no dimple at the proximal end of
an ostial occlusion, since a diagnosis of ostial atresia can
only be established by CT angiography (Fig.1.138).
3. If the distal end of an occlusion is at a branching point and
both branches require recanalization despite having small
1. If a large dissection (false lumen) has been created in a
CTO after failure of antegrade PCI (Fig.1.136): You may
be lucky enough to nd a route that leads to the true
lumen at the end of the occlusion, but an antegrade CTO
crossing guidewire will readily enter the large false lumen
in most cases. Therefore, you should consider early
switching to retrograde PCI.
Before switching to retrograde PCI, you should
advance a relatively soft antegrade CTO guidewire. This
wire may possibly be able to cross the occlusion through
the true lumen, and it can serve as a landmark to facilitate
retrograde wiring if crossing fails.
2. If the proximal cap of a CTO is located at a large coronary
ostium and is inaccessible from the ostium (Fig. 1.137):
Such a CTO cannot be recanalized by antegrade PCI.If possible, an antegrade guiding catheter should be positioned at
luminal diameters (Fig. 1.139): Even if an antegrade
guidewire crosses such an occlusion through the true
lumen, it often penetrates plaque at the branching point
and enters the true lumen distal to the carina. In this situation, the side branch may not be isolated even after dilation by a small balloon. In contrast, a guidewire advanced
retrogradely to the branching point always enters plaque
proximal to the carina, so the side branch will not be
occluded by inating a balloon in the occlusion.
4. If an antegrade guidewire fails to enter the distal true
lumen (Fig.1.140).
5. If an antegrade guidewire undergoes deviation into the
subintimal space after being blocked by a hard obstruction (Fig. 1.141): When an antegrade guidewire with a
very high tip load (e.g., a Conquest Pro 12) is blocked by
a hard obstruction within a CTO and cannot be advanced
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further through the true lumen, you should advance
another guidewire retrogradely. If the retrograde guidewire can reach the site of the obstruction, you may then
bypass the obstacle relatively easily with the antegrade
guidewire. Eventually, this may lead to successful crossing of the CTO by the reverse CART technique (reverse
CART) with a short false lumen passage.
6. If an antegrade guidewire undergoes extravascular deviation while being advanced through a long occlusion with
a
anatomy unclear: In this situation, you should promptly
switch to retrograde PCI.If a retrograde guidewire fails to
enter the true lumen, you may try to advance an antegrade
guidewire again using the retrograde guidewire as a landmark (kissing wire technique). This often leads to successful intimal/subintimal tracking and allows reverse
CART.
b
c
Fig. 1.136 CTO of the distal RCA (Segment #3) (a). (b) An antegrade
guidewire has reached the distal true lumen, but has tracked through a
false lumen on its way to the exit. After completion of PCI, the posterior
descending branch was still occluded. (c) Imaging immediately before
reattempting PCI showed a large false lumen in Segment #3. A guidewire could easily track the posterolateral branch, so the posterior
descending branch was approached retrogradely, and the CTO was successfully recanalized without side branch occlusion
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a b
Fig. 1.137 In-stent occlusion in the proximal RCA.A stent previously implanted from the ostium of the RCA precluded sufcient backup by the
guiding catheter and diagnostic contrast imaging
Fig. 1.138 Coronary ostial atresia. (a) CAG. (b) CT angiogram. RCA angiography provides good visualization of the LCA.CT angiography
shows no ndings suggestive of LCA ostial atresia
ab
1.7 Retrograde Approach
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Fig. 1.139 CTO of the distal RCA (Segment #3). Antegrade PCI was
attempted, but the CTO could not be crossed. Subsequently, retrograde
PCI via the LCX was successful
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Fig. 1.141 Antegrade guidewire blocked by a hard obstruction (a). (b)
After a retrograde guidewire has entered the occlusion in the true
lumen, it may become easier to direct the antegrade guidewire toward
the true lumen
Fig. 1.140 CTO of the LAD
(a) (Segment #7). After
failure to cross the CTO
antegradely (b), the retrograde
approach via the RCA was
successful (c)
abc
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1.7.2 Collateral Channels
Whether the retrograde approach can be performed is dependent on the availability of accessible collateral channels.
General knowledge of the collateral channels that usually
exist may help you to discover obscure channels on CAG.In
addition, understanding the anatomy of these channels facilitates selection of the optimal uoroscopy angles for viewing
the longitudinal axis of each channel, as well as assisting
with assessment of the accessibility of each channel and
devising the optimal tracking strategy.
Here, I present the collateral channels that I have success-
fully tracked when performing retrograde PCI, although this
list may not include all types of channels that could potentially exist.
Collateral channels that can be used for the retrograde
approach to CTOs of the RCA, LAD, and LCX are presented
in Figs.1.142, 1.143, and 1.144, respectively.
Diagnostic CAG images and control CAG images
obtained immediately before switching to retrograde PCI
should be reviewed to identify every possible collateral
channel and determine their accessibility.
Continuity of a channel may be obvious in a certain view,
but not in another view. Performing tip injection of contrast
medium with a microcatheter will eventually lead to a conclusion regarding channel continuity. However, the anatomy
of collateral channels generally follows certain rules. An epicardial channel does not cross another channel without communication, i.e., it does not jump over a nearby vessel to join
another more distant vessel. As a result, collateral channels
that connect the anterior and posterior sides of the heart run
on the surface of the atria or through the atrial septum, or
through the ventricular septum, or on the surface of the apex.
Even if two channels running through the ventricular septum
appear to cross each other, they will actually run on the left
and right ventricular sides of the septum and not in the same
plane (i.e., overhead crossing). You must not miss such channels that appear to cross each other on CAG.A guidewire
may be able to track a channel that is invisible on CAG and
reach the lumen of the target vessel distal to the occlusion.
This is particularly true for septal channels, and it should be
remembered that a guidewire may be advanced beyond the
visible end of a channel (Fig.1.145).
de f
Fig. 1.142 Collateral channels available for the retrograde approach to
CTO of the RCA. (a) RAO. (1) LCX→ACC→AVB. (2) SB→AVB.
(3) PL→ FWEp→RCAPL. (4) SB→4PD. (5) LAD apex→4PD. (b)
RAO.RVB→SB and RVB→LAD. (c) RAO. (1) Dg→Apex→RVB.
(2) Dg → Apex→4PD. (d) LAO. (1) LCX → ACC → AVB. (2)
LCX→FWEp→AVB. ACC atrial circumex channel, AVB atrioven-
tricular branch, FWEp free wall epicardial channel. (e)
LAO. Intracoronary collateral; Right atrial branch (SNA) → Kugel
anastomosis→AVB (AVNA). SNA sinoatrial node artery, AVB atrioventricular branch, AVNA atrioventricular node artery. (f)
RAO.Intracoronary collateral; RVB → RVB.RVB: right ventricular
branch
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