- Email: [email protected]
Tip Detection Method Using the New IVUS Facilitates the 3-Dimensional Wiring Technique for CTO Intervention
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ª 2019 THE AUTHORS. PUBLISHED BY ELSEVIER ON BEHALF OF THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION. THIS IS AN OPEN ACCESS ARTICLE UNDER THE CC BY-NC-ND LICENSE (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Tip Detection Method Using the New IVUS Facilitates the 3-Dimensional Wiring Technique for CTO Intervention Atsunori Okamura, MD,a Katsuomi Iwakura, MD,a Mutsumi Iwamoto, MD,a Hiroyuki Nagai, MD,a Akinori Sumiyoshi, MD,a Kota Tanaka, MD,a Takamasa Tanaka, MD,b Koichi Inoue, MD,a Yasushi Koyama, MD,a Kenshi Fujii, MDa
ABSTRACT
OBJECTIVES The study assessed the efficacy of the tip detection method during intravascular ultrasound (IVUS)–based 3-dimensional (3D) wiring with a new chronic total occlusion (CTO)–specific IVUS system (AnteOwl IVUS [AO-IVUS]) for CTO percutaneous coronary intervention (PCI). BACKGROUND The study developed angiography-based 3D wiring for CTO-PCI. Previously, the authors produced a short-tip CTO-specific IVUS system (Navifocus WR IVUS [Navi-IVUS]), which has been upgraded into the AO-IVUS system by adding a pullback transducer system for IVUS-based 3D wiring. METHODS A CTO lesion 20 mm in length composed of 2.5% agar was experimentally inserted into the coronary artery of a beating heart model. The target (a microcatheter with a 0.6-mm lumen) was placed in the distal part of the CTO lesion. IVUS-guided wiring was performed to insert the guidewire into the target using the Navi-IVUS and then using the AO-IVUS 8 times each. In wiring with AO-IVUS, the IVUS-based 3D wiring using the tip detection method was performed. The crossing time and the number of punctures to the target were calculated. RESULTS The crossing time was significantly shortened and the number of punctures was significantly reduced in AO-IVUS–based wiring compared with Navi-IVUS–based wiring (median crossing time 80.5 [interquartile range: 44.0 to 112.3] s vs. 333.0 [interquartile range: 88.8 to 790.0] s; p ¼ 0.036; median 1.0 [interquartile range: 1.0 to 2.0] puncture vs. 24.0 [interquartile range: 5.8 to 52.5] punctures; p ¼ 0.001). CONCLUSIONS The tip detection method enables the authors to easily perform the IVUS-based 3D wiring, and the new CTO IVUS system will facilitate this method in clinical practice. (J Am Coll Cardiol Intv 2019;-:-–-) © 2019 The Authors. Published by Elsevier on behalf of the American College of Cardiology Foundation. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
A
ccurate guidewire control is essential to
vessel damage. Owing to the long proximal monorail
improve and standardize percutaneous coro-
lumen (26 cm in length), this IVUS system can main-
nary intervention (PCI) for chronic total
tain good deliverability in CTO lesions despite the
occlusion
(CTO)
lesions.
In
collaboration
with
short tip-to-transducer length.
Terumo Corporation (Tokyo, Japan), we produced a
Our clinical experience with Navi-IVUS–guided
CTO-specific intravascular ultrasound (IVUS) system,
wiring indicated that 3-dimensional (3D) imaging is
Navifocus WR IVUS (Navi-IVUS), in 2012 (1,2). This
important for accurate guidewire control in CTO-PCI.
IVUS system has a small-profile transducer (2.5-F)
Therefore, we developed an angiography-based 3D
with a short tip-to-transducer length (9 mm) to allow
wiring method (3), which we have been using in our
insertion into the subintimal space with minimal
clinical practice since 2014. Recently, we reported the
From the aDivision of Cardiology, Sakurabashi Watanabe Hospital, Osaka, Japan; and the bDivision of Cardiovascular Medicine, Hyogo College of Medicine, Hyogo, Japan. Dr. Okamura has received speaking fees from Terumo. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose. Manuscript received March 26, 2019; revised manuscript received July 25, 2019, accepted July 30, 2019.
ISSN 1936-8798
https://doi.org/10.1016/j.jcin.2019.07.041
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ABBREVIATIONS
efficacy of angiography-based 3D wiring in
to the transducer and the IVUS’ own guidewire,
AND ACRONYMS
our clinical practice (4). 3D wiring enables
which can
accurate guidewire control, which improves
image to that of the angiographic image for accurate
the success rate of antegrade wiring and
navigation of the next guidewire into the true
reduces
lumen on both the IVUS image and the angio-
3D = 3-dimensional AO-IVUS = AnteOwl intravascular ultrasound
CTO = chronic total occlusion IVUS = intravascular
the
antegrade
procedure
time,
resulting in improvements of the overall success rate. However, if the guidewire is inserted into the subintimal space, it is
ultrasound
necessary to move on to other strategies,
Navi-IVUS = Navifocus WR intravascular ultrasound
such as the retrograde approach (5), dissec-
PCI = percutaneous coronary
tion re-entry (6), or IVUS-guided wiring (1,2).
intervention
While establishing the angiography-based 3D wiring method, we found that the tip detection method, involving observation of the guidewire tip as well as the shaft, simplifies and facilitates 3D wiring under IVUS-guided wiring for CTO-PCI. To perform IVUS-based 3D wiring using this tip detection method, the pullback system is essential to real-time observation of the guidewire tip as well as the shaft and the target true lumen. Therefore, we produced AnteOwl IVUS (AO-IVUS) (Terumo), which is an upgraded version of Navi-IVUS with an added pullback transducer system. AO-IVUS received regulatory approval in Japan in June 2018, though it is not yet available for clinical use. This experimental study was performed to assess the efficacy of the tip detection method during IVUSbased 3D wiring with the AO-IVUS, which has a short tip and a pullback transducer system. We have also reported on a case of CTO treated by IVUS-based 3D wiring using the tip detection method.
METHODS SPECIFICATIONS OF AO-IVUS. Figure 1 illustrates
the specifications of AO-IVUS. The major change from Navi-IVUS is the addition of the pullback system that allows the transducer to be pulled back by 15 cm. The other minor modifications are as follows: 1) the tip-to-transducer length has been shortened from 9 mm to 8 mm; 2) the diameter of the tip has been reduced by impregnating contrast agent into the tip without the marker band; 3) the diameter of the shaft has also been reduced from 3.2-F to 3.1-F, and therefore AO-IVUS can be inserted into a 7-F
transfer
the
direction
of
the
IVUS
graphic image. METHODOLOGY OF IVUS-BASED 3D WIRING USING THE TIP DETECTION METHOD. Previously, we re-
ported an angiography-based 3D wiring method that can construct a real-time mental 3D image from 2 perpendicular angles of the x-ray system monitor during CTO-PCI (3,4). To allow the operator to construct 3D images during CTO-PCI, it is necessary to divide the guidewire into shaft and tip sections and to determine their relationships with the target. The Central Illustration illustrates the methodology of angiography-based 3D image construction and IVUSbased 3D image construction during CTO-PCI. In construction of the angiography-based 3D image (Central Illustration), we should apply the 3D image rule: “The object (shaft or tip) is always in front (behind) on the next image after rotation if the object is in the same (opposite) direction as the rotational direction of the x-ray detector.” By using this 3D image rule, 2 images of the 2 perpendicular angles from the x-ray monitor can be fused into an IVUS-like image, which is mentally constructed image in the mind of the operator. In construction of the IVUS-based 3D image, the tip detection method should be used to construct a 3D image only from IVUS images without using angiography. The Central Illustration illustrates the tip detection method in IVUS-based 3D wiring during navigation of the second guidewire into the true lumen during IVUS observation from the subintimal space. Not only the shaft, but also the tip and its direction can be clearly visualized by moving the transducer back and forth between the end of the tip and the transition point of the tip to the shaft (Figure 2). By moving the transducer back and forth around 5 mm from the target to the tip area, the 3D image can be easily visualized, which then directly shows the direction (counterclockwise) and degree of guidewire rotation (Central Illustration).
guide catheter with a Corsair microcatheter (Asahi
EXPERIMENTAL
Intecc, Aichi, Japan) for the second guidewire.
WIRING. Figure 3A shows the experimental CTO
However, AO-IVUS still cannot be inserted into a 6-F
lesion for wiring. We used an experimental beating
guide catheter with any other microcatheters for the
heart model (Terumo) and created a target pinpoint
second guidewire. The AO-IVUS has the same func-
penetration model (3,4) for IVUS-based 3D wiring. A
tionality as described for Navi-IVUS (2); the double
CTO lesion 20 mm in length and 3.0 mm in diameter
monorail lumen system maintains a fixed asym-
was made of 2.5% agar and inserted into the mid-right
metrical structure, which is a proximal marker next
coronary artery. The target, which was a Sniper
CTO
LESION
AND
IVUS-BASED
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F I G U R E 1 Specifications of AO-IVUS
(A) Complete structural illustration of AnteOwl intravascular ultrasound (AO-IVUS). (B) Magnification of the tip-to-transducer area of AO-IVUS.
microcatheter (Terumo) with a 0.6-mm lumen, was
2 groups using SPSS version 22.0 (IBM Japan, Tokyo,
placed in the distal part of the CTO lesion.
Japan) and p < 0.05 was considered to indicate a
Figure 3B shows IVUS-based wiring using Navi-
statistically significant difference.
IVUS or AO-IVUS. The first guidewire was passed outside of the target in the experimental CTO lesion. IVUS was advanced through the first guidewire and
RESULTS
reached the desired position where the transducer was just beyond the target. The second guidewire
with the 1 mm curve at an angle of 45 (Confianza-12g, Asahi Intecc) supported by a Corsair microcatheter was advanced into the CTO lesion to within 5 mm of
the
target
using
angiography-based
wiring
including the angiography-based 3D wiring (Central Illustration). In Navi-IVUS–based wiring, the second guidewire was advanced to the target using the onedirection fluoroscopic image and the IVUS image just beyond the target. In AO-IVUS based wiring, the second guidewire was advanced using the onedirection fluoroscopic image and IVUS images from the target to the tip area to perform IVUS-based 3D wiring using the tip detection method. These IVUSbased wirings were performed 8 times each and the crossing time and number of punctures to the target were calculated.
REPRESENTATIVE USING
THE
TIP
AO-IVUS–based DETECTION
3D
WIRING
METHOD
FOR
EXPERIMENTAL CTO LESIONS. The first guidewire
was passed outside of the target in the experimental CTO lesion (Figure 4A). AO-IVUS was advanced through the first guidewire (Figure 4B). After AO-IVUS had reached the desired position where the transducer was just beyond the target, the transducer was pulled back to observe the target, which was clearly visualized as a round-shaped entrance with a lumen 0.6 mm in diameter (Figure 4C). Figure 5 shows the AO-IVUS–based 3D wiring. The second guidewire (Conquest 12g) supported by a Corsair was advanced into the CTO lesion to within 5 mm of the target using angiography-based wiring (Figure 5AI). By IVUS observation
from
the
target
to
the
tip
area
(Figures 5AII and 5AIII), the appropriate route for the second guidewire could be determined (Figure 5AIV).
STATISTICAL ANALYSIS. All data are given as me-
Then, the IVUS-based 3D image construction was
dian (interquartile range [IQR]). The 2 groups were
performed by moving the transducer back and forth
independent because we used different experimental
from the target to the tip area to allow visualization of
vessel models in every procedure. Mann-Whitney U
the 3D image in real time (Figure 5BI), which allowed
test was used to assess differences between the
the second guidewire to be accurately advanced
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C E N T R A L IL LU ST R A T I O N Methodology of the Angiography- and IVUS-Based 3D Image Constructions
A
B AO-IVUS
IVUS images
Shaft Tip
IVUS Target
CTO
Vessel LAO 60°
RAO 30°
Movement of transducer back and forth
True
Tip detection method
Shaft
2nd-wire
3D image rule
True
Mental construction of 3D image
IVUS Shaft
Mental construction of 3D image
Counter clockwise
Clockwise 45°
True True 1st-wire
IVUS True
Tip
Subintima
Subintima
RAO 30° LAO 60°
Counter clockwise e
Okamura, A. et al. J Am Coll Cardiol Intv. 2019;-(-):-–-.
(A) Angiography-based 3-dimensional (3D) image construction. (B) Intravascular ultrasound (IVUS)–based 3D image construction using the tip detection method. AO-IVUS ¼ AnteOwl intravascular ultrasound; CTO ¼ chronic total occlusion; LAO ¼ left anterior oblique; Navi-IVUS ¼ Navifocus WR intravascular ultrasound; RAO ¼ right anterior oblique.
to the target while rotating in a counterclockwise
COMPARISON OF CROSSING TIME AND NUMBER OF
direction (Figures 5BII to 5BIV). The second guidewire
PUNCTURES
was inserted into the target in the first puncture
WIRING. The crossing time of IVUS-based wiring
(Figures 5CI and 5CII).
was significantly shortened using AO-IVUS compared
TO
THE
TARGET
OF
IVUS-BASED
F I G U R E 2 AO-IVUS Images of Guidewire Shaft and Tip
AnteOwl intravascular ultrasound (AO-IVUS) images of the guidewire (Confianza-12g; Asahi Intecc, Aichi, Japan) with a 1-mm curve at a 45 angle. (A) The guidewire shaft could be visually recognized as a distinct point with the echo shadow behind it (white arrow). (B) The guidewire tip and its direction could be visually recognized as a thin line (dotted arrow).
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F I G U R E 3 Experimental CTO Lesion and Its Target and 2 Methods of IVUS-Based Wiring
(A) Angiographic image and illustration of the experimental chronic total occlusion (CTO) lesion. (B) The method of intravascular ultrasound (IVUS)–based wiring using Navifocus WR IVUS (Navi-IVUS) or AnteOwl IVUS (AO-IVUS).
F I G U R E 4 Angiographic Images and IVUS Image During the Observation of the Target
(A) Angiographic image after advancement of the first guidewire. (B) Angiographic image during advancement of AO-IVUS. (C) Angiographic image after advancement of AO-IVUS as well as IVUS image at the entrance level of the target. Abbreviations as in Figure 3.
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F I G U R E 5 Angiographic Images and IVUS Images During AO-IVUS–Based 3-Dimensional Wiring
(A) Angiographic image after advancement of the second guidewire within 5 mm of the target (I), IVUS images at the tip (II) and target (III) levels, and illustration of the appropriate route for the second guidewire (IV). (B) Angiographic (I) and IVUS (II to IV) images during IVUS-based 3D wiring using the tip detection method. (C) Angiographic (I) and IVUS (II) images after successful pinpoint puncture. Abbreviations as in Figure 3.
with Navi-IVUS (80.5 [IQR: 44.0 to 112.3] s vs. 333.0
tip-to-transducer length (22 mm). It is commonly
[IQR: [88.8 to 790.0] s; p ¼ 0.036) (Table 1). The
used in Japan and the specifications are similar to
number of punctures to the target was significantly
those of OptiCross IVUS (Boston Scientific, Natick,
reduced using AO-IVUS compared with Navi-IVUS
Massachusetts),
(1.0 [IQR: 1.0 to 2.0] vs. 24.0 [IQR: 5.8 to 52.5];
the world.
p ¼ 0.001) (Table 1).
which
is
widely
used
around
A female patient in her seventies with stable
REPRESENTATIVE CASE OF 3D WIRING USING TIP DETECTION METHOD. As AO-IVUS is currently still
being prepared for clinical use, we present this case of 3D wiring using the tip detection method with AltaView IVUS (Terumo). AltaView IVUS has a pullback transducer system, but a relatively long
angina pectoris underwent PCI for CTO lesion in the proximal right coronary artery (Figure 6AI), but the guidewires could not pass thorough the lesion because they entered into the subintimal space (Figure 6AII). Therefore, she was transferred to our hospital to retry the procedure for the CTO lesion. An 8-F short-tip left Amplatz 1.0 guide catheter (Medtronic AVE, Santa Rosa, California) was inserted
T A B L E 1 Comparison of the Crossing Time and the Number of Punctures to the
into the right coronary artery. A GAIA Second (Asahi
Target Between the AO-IVUS– and Navi-IVUS–Based Wiring
Crossing time of the IVUS-based wiring, s Punctures to the target, count
Intecc) and then a Confianza-12g guidewire supported by a Corsair microcatheter could not pass through the
AO-IVUS With Tip Detection (n ¼ 8)
Navi-IVUS Without Tip Detection (n ¼ 8)
p Value*
80.5 (44.0–112.3)
333.0 (88.8–790.0)
0.036
1.0 (1.0–2.0)
24.0 (5.8–52.5)
0.001
CTO lesion using angiography-based 3D wiring because of the residual subintimal space created by the first procedure (Figure 6BI). An Ultimate Bros3 guidewire
(Asahi
Intecc)
(first
guidewire)
was
Values are median (interquartile range). *Mann-Whitney U test.
advanced into the subintimal space 3 cm beyond the
AO-IVUS ¼ AnteOwl intravascular ultrasound; IVUS ¼ intravascular ultrasound; Navi-IVUS ¼ Navifocus WR intravascular ultrasound.
entrance of the CTO, and the Corsair was advanced 2 cm beyond the entrance to create the space for
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F I G U R E 6 Angiographic Images of the First and Second Procedures
(A) Angiographic images before percutaneous coronary intervention (PCI) (I) and during guidewire manipulation (II) at the first PCI. (B) Angiographic images during guidewire manipulation (I) and after recanalization due to stent implantation (II) at the second PCI in our hospital.
the IVUS catheter. Then, the AltaView IVUS was
a short tip and a pullback transducer system. As this
advanced through the Ultimate Bros3, which revealed
IVUS is still being prepared for clinical use, we re-
that the Ultimate Bros3 had entered into the sub-
ported the tip detection method in a clinical case
intimal space 1 cm distal from the entrance of the CTO
using the regular IVUS system (AltView IVUS).
(Figure 7A). The Confianza-12g (second guidewire) was advanced supported by the Corsair microcatheter and IVUS-based 3D wiring using the tip detection method was performed from the entrance by moving the transducer back and forth from the transitional site of the true and subintimal spaces to the tip area, which allowed the second guidewire to be accurately advanced to the true lumen (Figures 7B and 7C). The CTO lesion was dilated with 2 drug-eluting stents and normal antegrade blood flow was achieved (Figure 6BII).
EFFICACY OF IVUS-BASED 3D WIRING USING THE TIP DETECTION METHOD. As we reported previously,
to allow the operator to construct 3D images during CTO-PCI, it is necessary to divide the guidewire into shaft and tip sections and to determine their relationships with the target (3,4). At present, operators around the world only observe the true lumen (target) and the guidewire shaft, but not the guidewire tip, in IVUS-guided wiring. Furthermore, the operators only confirm that the guidewire shaft is inside the true lumen after several attempts of guidewire advancement to the position that is presumed to be the true
DISCUSSION
lumen on angiographic images. However, to construct a 3D image, it is necessary to observe the guidewire
In the present experimental study, we demonstrated
tip as well as the guidewire shaft and target. There-
the efficacy of the tip detection method during IVUS-
fore, we developed a tip detection method to
based 3D wiring with the new CTO IVUS system
construct IVUS-based 3D images. In the present
(AO-IVUS), which is the first of its kind that has both
study, the number of punctures to the target was
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F I G U R E 7 IVUS-Based 3D Wiring Using the Tip Detection Method
(A) Angiographic (I) and IVUS (II) images just before IVUS-based 3-dimensional (3D) wiring using the tip detection method. (B) Illustrations and IVUS images (I to VI) during IVUS-based 3D wiring. IVUS images (I to III) showing how to construct the mental 3D image. IVUS images (IV to VI) showing that the tip was accurately directed to the true lumen after clockwise rotation. (C) IVUS image and illustration after successful puncture of the guidewire into the true lumen. Abbreviations as in Figure 3.
wiring
moved back and forth in real time according to the
compared with Navi-IVUS–based wiring (1.0 [IQR: 1.0
movement of the guidewire, which will cause further
to 2.0] vs. 24.0 [IQR: 5.8 to 52.5]; p ¼ 0.001). The tip
damage to the CTO lesion and interfere with the
detection method makes the IVUS guided wiring
manipulation of the guidewire. Therefore, the oper-
quite accurate, but without the tip detection method,
ator can only confirm the location of the guidewire
IVUS-guided wiring is much less accurate, and the
after guidewire advancement, which is less accurate.
large IQR means that successful puncture sometimes
If the operator wishes to perform IVUS-based 3D
only occurs by chance.
wiring using the tip detection method, OpitCross
significantly
reduced
in
AO-IVUS–based
(relatively long-tip IVUS, 20 mm) should be used THE SHORT- IP WITH PULLBACK SYSTEM IVUS
despite the disadvantage of longer subintimal space
FACILITATES IVUS-BASED 3D WIRING. The pullback
formation. If IVUS systems with both a short tip and
system is essential to perform IVUS-based 3D wiring
pullback system, such as AO-IVUS, also become
using the tip detection method, and furthermore the
available around the world, IVUS-based 3D wiring
short tip is also desirable to minimize subintimal
using the tip detection method will be widely adopted
space formation. Therefore, we produced AO-IVUS,
and is promising for being able to be used in more
which is an upgraded version of Navi-IVUS (short-
situations after the use of the antegrade guidewire
tip IVUS), by adding a pullback transducer system.
escalation in hybrid strategies (8,9). If the passage of
Outside of Japan, Eagle-Eye IVUS (short-tip IVUS)
a guidewire through the intima is likely to be difficult
(Volcano, Royal Dutch Philips Electronics, Best, the
because of severe calcification or severe bending and
Netherlands) is usually used for IVUS-guided wiring
the distal re-entry site can be visualized, the dissec-
in cases of CTO lesions (7). Eagle-Eye IVUS does not
tion re-entry should be considered. However, if the
have the pullback system. To observe the guidewire
lesions are not severely calcified and severely ben-
shaft and tip, Eagle-Eye IVUS catheter itself should be
ded, the AO-IVUS–guided tip detection will be more
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suitable among the antegrade approaches because the
Osaka, Japan), for preparation of the angiographic
side branches will be preserved due to the true lumen
and IVUS images.
passage. Furthermore, if the vessel course is not unclear and the distal site cannot be visualized, consider
FOR
Okamura,
Sakurabashi-Watanabe
inside the vessel followed by the AO-IVUS guided tip
Umeda
detection method. The IVUS guided tip detection
[email protected]. Twitter: @Aokamura5.
Kitaku,
CORRESPONDENCE:
Dr. Atsunori
ADDRESS
the knuckle wire technique to keep the guidewire
Osaka
530-0001,
Hospital,
2-4-32
Japan.
E-mail:
method usually needs the Confianza-12g to reroute the guidewire into the true lumen at the transition site. This method can navigate the CTO stiff wire throughout the CTO lesion; however, de-escalation to softer wires with lower risks of perforation can be considered for the body of the lesion before the transition site. After the successful passage into the true lumen, the guidewire de-escalation also can be considered.
PERSPECTIVES
WHAT IS KNOWN? We developed an angiography-based 3D wiring method in 2014 and recently reported on its efficacy in our clinical practice for CTO-PCI. We previously produced a short-tip CTO-specific IVUS system (Navi-IVUS) in 2012, which has been commonly used for IVUS-guided wiring for CTO-PCI in Japan.
STUDY LIMITATIONS. As AO-IVUS is still being pre-
pared for clinical use, we demonstrated the efficacy of
WHAT IS NEW? Our final objective was the development of
AO-IVUS–based 3D wiring using the tip detection
IVUS-based 3D wiring allowing most accurate guidewire manip-
method only for experimental CTO lesions and re-
ulation for CTO-PCI. We developed a tip detection method to
ported a clinical case treated by this method with
simplify IVUS-based 3D wiring. To standardize this method in
AltaView IVUS, which has a long tip and pullback
clinical practice, we upgraded Navi-IVUS to AO-IVUS by adding a pullback transducer system and demonstrated the efficacy of
transducer system.
IVUS-based 3D wiring using the tip detection method with AO-
CONCLUSIONS
IVUS.
The tip detection method enables us to easily
WHAT IS NEXT? In the very near future, AO-IVUS will be used
perform the IVUS-based 3D wiring, which will be
in clinical practice in Japan and we will standardize AO-IVUS–
further facilitated by the new CTO IVUS system
based 3D wiring using the tip detection method in clinical prac-
(AO-IVUS).
tice. By continuing to promote this concept internationally, we
ACKNOWLEDGMENTS The authors thank Keiichiro
Yamamoto, Yoichi Ito, Yasunori Yamashita, Soichiro Sugihara,
and
Yuji
Yokomizo
(Terumo,
Tokyo,
Japan) for production of AO-IVUS and Katsutoshi Kawamura,
RT
(Sakurabashi-Watanabe
hope that CTO IVUS with both a short tip and pullback system will become available all over the world, which will lead to standardization of IVUS-based 3D wiring using the tip detection method.
Hospital,
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KEY WORDS chronic total occlusion,
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coronary intervention, IVUS-based 3D wiring, tip detection method
Lu TM. Intravascular ultrasound guided wiring
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ª 2019 THE AUTHORS. PUBLISHED BY ELSEVIER ON BEHALF OF THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION. THIS IS AN OPEN ACCESS ARTICLE UNDER THE CC BY-NC-ND LICENSE (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Tip Detection Method Using the New IVUS Facilitates the 3-Dimensional Wiring Technique for CTO Intervention Atsunori Okamura, MD,a Katsuomi Iwakura, MD,a Mutsumi Iwamoto, MD,a Hiroyuki Nagai, MD,a Akinori Sumiyoshi, MD,a Kota Tanaka, MD,a Takamasa Tanaka, MD,b Koichi Inoue, MD,a Yasushi Koyama, MD,a Kenshi Fujii, MDa
ABSTRACT
OBJECTIVES The study assessed the efficacy of the tip detection method during intravascular ultrasound (IVUS)–based 3-dimensional (3D) wiring with a new chronic total occlusion (CTO)–specific IVUS system (AnteOwl IVUS [AO-IVUS]) for CTO percutaneous coronary intervention (PCI). BACKGROUND The study developed angiography-based 3D wiring for CTO-PCI. Previously, the authors produced a short-tip CTO-specific IVUS system (Navifocus WR IVUS [Navi-IVUS]), which has been upgraded into the AO-IVUS system by adding a pullback transducer system for IVUS-based 3D wiring. METHODS A CTO lesion 20 mm in length composed of 2.5% agar was experimentally inserted into the coronary artery of a beating heart model. The target (a microcatheter with a 0.6-mm lumen) was placed in the distal part of the CTO lesion. IVUS-guided wiring was performed to insert the guidewire into the target using the Navi-IVUS and then using the AO-IVUS 8 times each. In wiring with AO-IVUS, the IVUS-based 3D wiring using the tip detection method was performed. The crossing time and the number of punctures to the target were calculated. RESULTS The crossing time was significantly shortened and the number of punctures was significantly reduced in AO-IVUS–based wiring compared with Navi-IVUS–based wiring (median crossing time 80.5 [interquartile range: 44.0 to 112.3] s vs. 333.0 [interquartile range: 88.8 to 790.0] s; p ¼ 0.036; median 1.0 [interquartile range: 1.0 to 2.0] puncture vs. 24.0 [interquartile range: 5.8 to 52.5] punctures; p ¼ 0.001). CONCLUSIONS The tip detection method enables the authors to easily perform the IVUS-based 3D wiring, and the new CTO IVUS system will facilitate this method in clinical practice. (J Am Coll Cardiol Intv 2019;-:-–-) © 2019 The Authors. Published by Elsevier on behalf of the American College of Cardiology Foundation. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
A
ccurate guidewire control is essential to
vessel damage. Owing to the long proximal monorail
improve and standardize percutaneous coro-
lumen (26 cm in length), this IVUS system can main-
nary intervention (PCI) for chronic total
tain good deliverability in CTO lesions despite the
occlusion
(CTO)
lesions.
In
collaboration
with
short tip-to-transducer length.
Terumo Corporation (Tokyo, Japan), we produced a
Our clinical experience with Navi-IVUS–guided
CTO-specific intravascular ultrasound (IVUS) system,
wiring indicated that 3-dimensional (3D) imaging is
Navifocus WR IVUS (Navi-IVUS), in 2012 (1,2). This
important for accurate guidewire control in CTO-PCI.
IVUS system has a small-profile transducer (2.5-F)
Therefore, we developed an angiography-based 3D
with a short tip-to-transducer length (9 mm) to allow
wiring method (3), which we have been using in our
insertion into the subintimal space with minimal
clinical practice since 2014. Recently, we reported the
From the aDivision of Cardiology, Sakurabashi Watanabe Hospital, Osaka, Japan; and the bDivision of Cardiovascular Medicine, Hyogo College of Medicine, Hyogo, Japan. Dr. Okamura has received speaking fees from Terumo. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose. Manuscript received March 26, 2019; revised manuscript received July 25, 2019, accepted July 30, 2019.
ISSN 1936-8798
https://doi.org/10.1016/j.jcin.2019.07.041
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ABBREVIATIONS
efficacy of angiography-based 3D wiring in
to the transducer and the IVUS’ own guidewire,
AND ACRONYMS
our clinical practice (4). 3D wiring enables
which can
accurate guidewire control, which improves
image to that of the angiographic image for accurate
the success rate of antegrade wiring and
navigation of the next guidewire into the true
reduces
lumen on both the IVUS image and the angio-
3D = 3-dimensional AO-IVUS = AnteOwl intravascular ultrasound
CTO = chronic total occlusion IVUS = intravascular
the
antegrade
procedure
time,
resulting in improvements of the overall success rate. However, if the guidewire is inserted into the subintimal space, it is
ultrasound
necessary to move on to other strategies,
Navi-IVUS = Navifocus WR intravascular ultrasound
such as the retrograde approach (5), dissec-
PCI = percutaneous coronary
tion re-entry (6), or IVUS-guided wiring (1,2).
intervention
While establishing the angiography-based 3D wiring method, we found that the tip detection method, involving observation of the guidewire tip as well as the shaft, simplifies and facilitates 3D wiring under IVUS-guided wiring for CTO-PCI. To perform IVUS-based 3D wiring using this tip detection method, the pullback system is essential to real-time observation of the guidewire tip as well as the shaft and the target true lumen. Therefore, we produced AnteOwl IVUS (AO-IVUS) (Terumo), which is an upgraded version of Navi-IVUS with an added pullback transducer system. AO-IVUS received regulatory approval in Japan in June 2018, though it is not yet available for clinical use. This experimental study was performed to assess the efficacy of the tip detection method during IVUSbased 3D wiring with the AO-IVUS, which has a short tip and a pullback transducer system. We have also reported on a case of CTO treated by IVUS-based 3D wiring using the tip detection method.
METHODS SPECIFICATIONS OF AO-IVUS. Figure 1 illustrates
the specifications of AO-IVUS. The major change from Navi-IVUS is the addition of the pullback system that allows the transducer to be pulled back by 15 cm. The other minor modifications are as follows: 1) the tip-to-transducer length has been shortened from 9 mm to 8 mm; 2) the diameter of the tip has been reduced by impregnating contrast agent into the tip without the marker band; 3) the diameter of the shaft has also been reduced from 3.2-F to 3.1-F, and therefore AO-IVUS can be inserted into a 7-F
transfer
the
direction
of
the
IVUS
graphic image. METHODOLOGY OF IVUS-BASED 3D WIRING USING THE TIP DETECTION METHOD. Previously, we re-
ported an angiography-based 3D wiring method that can construct a real-time mental 3D image from 2 perpendicular angles of the x-ray system monitor during CTO-PCI (3,4). To allow the operator to construct 3D images during CTO-PCI, it is necessary to divide the guidewire into shaft and tip sections and to determine their relationships with the target. The Central Illustration illustrates the methodology of angiography-based 3D image construction and IVUSbased 3D image construction during CTO-PCI. In construction of the angiography-based 3D image (Central Illustration), we should apply the 3D image rule: “The object (shaft or tip) is always in front (behind) on the next image after rotation if the object is in the same (opposite) direction as the rotational direction of the x-ray detector.” By using this 3D image rule, 2 images of the 2 perpendicular angles from the x-ray monitor can be fused into an IVUS-like image, which is mentally constructed image in the mind of the operator. In construction of the IVUS-based 3D image, the tip detection method should be used to construct a 3D image only from IVUS images without using angiography. The Central Illustration illustrates the tip detection method in IVUS-based 3D wiring during navigation of the second guidewire into the true lumen during IVUS observation from the subintimal space. Not only the shaft, but also the tip and its direction can be clearly visualized by moving the transducer back and forth between the end of the tip and the transition point of the tip to the shaft (Figure 2). By moving the transducer back and forth around 5 mm from the target to the tip area, the 3D image can be easily visualized, which then directly shows the direction (counterclockwise) and degree of guidewire rotation (Central Illustration).
guide catheter with a Corsair microcatheter (Asahi
EXPERIMENTAL
Intecc, Aichi, Japan) for the second guidewire.
WIRING. Figure 3A shows the experimental CTO
However, AO-IVUS still cannot be inserted into a 6-F
lesion for wiring. We used an experimental beating
guide catheter with any other microcatheters for the
heart model (Terumo) and created a target pinpoint
second guidewire. The AO-IVUS has the same func-
penetration model (3,4) for IVUS-based 3D wiring. A
tionality as described for Navi-IVUS (2); the double
CTO lesion 20 mm in length and 3.0 mm in diameter
monorail lumen system maintains a fixed asym-
was made of 2.5% agar and inserted into the mid-right
metrical structure, which is a proximal marker next
coronary artery. The target, which was a Sniper
CTO
LESION
AND
IVUS-BASED
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F I G U R E 1 Specifications of AO-IVUS
(A) Complete structural illustration of AnteOwl intravascular ultrasound (AO-IVUS). (B) Magnification of the tip-to-transducer area of AO-IVUS.
microcatheter (Terumo) with a 0.6-mm lumen, was
2 groups using SPSS version 22.0 (IBM Japan, Tokyo,
placed in the distal part of the CTO lesion.
Japan) and p < 0.05 was considered to indicate a
Figure 3B shows IVUS-based wiring using Navi-
statistically significant difference.
IVUS or AO-IVUS. The first guidewire was passed outside of the target in the experimental CTO lesion. IVUS was advanced through the first guidewire and
RESULTS
reached the desired position where the transducer was just beyond the target. The second guidewire
with the 1 mm curve at an angle of 45 (Confianza-12g, Asahi Intecc) supported by a Corsair microcatheter was advanced into the CTO lesion to within 5 mm of
the
target
using
angiography-based
wiring
including the angiography-based 3D wiring (Central Illustration). In Navi-IVUS–based wiring, the second guidewire was advanced to the target using the onedirection fluoroscopic image and the IVUS image just beyond the target. In AO-IVUS based wiring, the second guidewire was advanced using the onedirection fluoroscopic image and IVUS images from the target to the tip area to perform IVUS-based 3D wiring using the tip detection method. These IVUSbased wirings were performed 8 times each and the crossing time and number of punctures to the target were calculated.
REPRESENTATIVE USING
THE
TIP
AO-IVUS–based DETECTION
3D
WIRING
METHOD
FOR
EXPERIMENTAL CTO LESIONS. The first guidewire
was passed outside of the target in the experimental CTO lesion (Figure 4A). AO-IVUS was advanced through the first guidewire (Figure 4B). After AO-IVUS had reached the desired position where the transducer was just beyond the target, the transducer was pulled back to observe the target, which was clearly visualized as a round-shaped entrance with a lumen 0.6 mm in diameter (Figure 4C). Figure 5 shows the AO-IVUS–based 3D wiring. The second guidewire (Conquest 12g) supported by a Corsair was advanced into the CTO lesion to within 5 mm of the target using angiography-based wiring (Figure 5AI). By IVUS observation
from
the
target
to
the
tip
area
(Figures 5AII and 5AIII), the appropriate route for the second guidewire could be determined (Figure 5AIV).
STATISTICAL ANALYSIS. All data are given as me-
Then, the IVUS-based 3D image construction was
dian (interquartile range [IQR]). The 2 groups were
performed by moving the transducer back and forth
independent because we used different experimental
from the target to the tip area to allow visualization of
vessel models in every procedure. Mann-Whitney U
the 3D image in real time (Figure 5BI), which allowed
test was used to assess differences between the
the second guidewire to be accurately advanced
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C E N T R A L IL LU ST R A T I O N Methodology of the Angiography- and IVUS-Based 3D Image Constructions
A
B AO-IVUS
IVUS images
Shaft Tip
IVUS Target
CTO
Vessel LAO 60°
RAO 30°
Movement of transducer back and forth
True
Tip detection method
Shaft
2nd-wire
3D image rule
True
Mental construction of 3D image
IVUS Shaft
Mental construction of 3D image
Counter clockwise
Clockwise 45°
True True 1st-wire
IVUS True
Tip
Subintima
Subintima
RAO 30° LAO 60°
Counter clockwise e
Okamura, A. et al. J Am Coll Cardiol Intv. 2019;-(-):-–-.
(A) Angiography-based 3-dimensional (3D) image construction. (B) Intravascular ultrasound (IVUS)–based 3D image construction using the tip detection method. AO-IVUS ¼ AnteOwl intravascular ultrasound; CTO ¼ chronic total occlusion; LAO ¼ left anterior oblique; Navi-IVUS ¼ Navifocus WR intravascular ultrasound; RAO ¼ right anterior oblique.
to the target while rotating in a counterclockwise
COMPARISON OF CROSSING TIME AND NUMBER OF
direction (Figures 5BII to 5BIV). The second guidewire
PUNCTURES
was inserted into the target in the first puncture
WIRING. The crossing time of IVUS-based wiring
(Figures 5CI and 5CII).
was significantly shortened using AO-IVUS compared
TO
THE
TARGET
OF
IVUS-BASED
F I G U R E 2 AO-IVUS Images of Guidewire Shaft and Tip
AnteOwl intravascular ultrasound (AO-IVUS) images of the guidewire (Confianza-12g; Asahi Intecc, Aichi, Japan) with a 1-mm curve at a 45 angle. (A) The guidewire shaft could be visually recognized as a distinct point with the echo shadow behind it (white arrow). (B) The guidewire tip and its direction could be visually recognized as a thin line (dotted arrow).
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F I G U R E 3 Experimental CTO Lesion and Its Target and 2 Methods of IVUS-Based Wiring
(A) Angiographic image and illustration of the experimental chronic total occlusion (CTO) lesion. (B) The method of intravascular ultrasound (IVUS)–based wiring using Navifocus WR IVUS (Navi-IVUS) or AnteOwl IVUS (AO-IVUS).
F I G U R E 4 Angiographic Images and IVUS Image During the Observation of the Target
(A) Angiographic image after advancement of the first guidewire. (B) Angiographic image during advancement of AO-IVUS. (C) Angiographic image after advancement of AO-IVUS as well as IVUS image at the entrance level of the target. Abbreviations as in Figure 3.
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F I G U R E 5 Angiographic Images and IVUS Images During AO-IVUS–Based 3-Dimensional Wiring
(A) Angiographic image after advancement of the second guidewire within 5 mm of the target (I), IVUS images at the tip (II) and target (III) levels, and illustration of the appropriate route for the second guidewire (IV). (B) Angiographic (I) and IVUS (II to IV) images during IVUS-based 3D wiring using the tip detection method. (C) Angiographic (I) and IVUS (II) images after successful pinpoint puncture. Abbreviations as in Figure 3.
with Navi-IVUS (80.5 [IQR: 44.0 to 112.3] s vs. 333.0
tip-to-transducer length (22 mm). It is commonly
[IQR: [88.8 to 790.0] s; p ¼ 0.036) (Table 1). The
used in Japan and the specifications are similar to
number of punctures to the target was significantly
those of OptiCross IVUS (Boston Scientific, Natick,
reduced using AO-IVUS compared with Navi-IVUS
Massachusetts),
(1.0 [IQR: 1.0 to 2.0] vs. 24.0 [IQR: 5.8 to 52.5];
the world.
p ¼ 0.001) (Table 1).
which
is
widely
used
around
A female patient in her seventies with stable
REPRESENTATIVE CASE OF 3D WIRING USING TIP DETECTION METHOD. As AO-IVUS is currently still
being prepared for clinical use, we present this case of 3D wiring using the tip detection method with AltaView IVUS (Terumo). AltaView IVUS has a pullback transducer system, but a relatively long
angina pectoris underwent PCI for CTO lesion in the proximal right coronary artery (Figure 6AI), but the guidewires could not pass thorough the lesion because they entered into the subintimal space (Figure 6AII). Therefore, she was transferred to our hospital to retry the procedure for the CTO lesion. An 8-F short-tip left Amplatz 1.0 guide catheter (Medtronic AVE, Santa Rosa, California) was inserted
T A B L E 1 Comparison of the Crossing Time and the Number of Punctures to the
into the right coronary artery. A GAIA Second (Asahi
Target Between the AO-IVUS– and Navi-IVUS–Based Wiring
Crossing time of the IVUS-based wiring, s Punctures to the target, count
Intecc) and then a Confianza-12g guidewire supported by a Corsair microcatheter could not pass through the
AO-IVUS With Tip Detection (n ¼ 8)
Navi-IVUS Without Tip Detection (n ¼ 8)
p Value*
80.5 (44.0–112.3)
333.0 (88.8–790.0)
0.036
1.0 (1.0–2.0)
24.0 (5.8–52.5)
0.001
CTO lesion using angiography-based 3D wiring because of the residual subintimal space created by the first procedure (Figure 6BI). An Ultimate Bros3 guidewire
(Asahi
Intecc)
(first
guidewire)
was
Values are median (interquartile range). *Mann-Whitney U test.
advanced into the subintimal space 3 cm beyond the
AO-IVUS ¼ AnteOwl intravascular ultrasound; IVUS ¼ intravascular ultrasound; Navi-IVUS ¼ Navifocus WR intravascular ultrasound.
entrance of the CTO, and the Corsair was advanced 2 cm beyond the entrance to create the space for
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F I G U R E 6 Angiographic Images of the First and Second Procedures
(A) Angiographic images before percutaneous coronary intervention (PCI) (I) and during guidewire manipulation (II) at the first PCI. (B) Angiographic images during guidewire manipulation (I) and after recanalization due to stent implantation (II) at the second PCI in our hospital.
the IVUS catheter. Then, the AltaView IVUS was
a short tip and a pullback transducer system. As this
advanced through the Ultimate Bros3, which revealed
IVUS is still being prepared for clinical use, we re-
that the Ultimate Bros3 had entered into the sub-
ported the tip detection method in a clinical case
intimal space 1 cm distal from the entrance of the CTO
using the regular IVUS system (AltView IVUS).
(Figure 7A). The Confianza-12g (second guidewire) was advanced supported by the Corsair microcatheter and IVUS-based 3D wiring using the tip detection method was performed from the entrance by moving the transducer back and forth from the transitional site of the true and subintimal spaces to the tip area, which allowed the second guidewire to be accurately advanced to the true lumen (Figures 7B and 7C). The CTO lesion was dilated with 2 drug-eluting stents and normal antegrade blood flow was achieved (Figure 6BII).
EFFICACY OF IVUS-BASED 3D WIRING USING THE TIP DETECTION METHOD. As we reported previously,
to allow the operator to construct 3D images during CTO-PCI, it is necessary to divide the guidewire into shaft and tip sections and to determine their relationships with the target (3,4). At present, operators around the world only observe the true lumen (target) and the guidewire shaft, but not the guidewire tip, in IVUS-guided wiring. Furthermore, the operators only confirm that the guidewire shaft is inside the true lumen after several attempts of guidewire advancement to the position that is presumed to be the true
DISCUSSION
lumen on angiographic images. However, to construct a 3D image, it is necessary to observe the guidewire
In the present experimental study, we demonstrated
tip as well as the guidewire shaft and target. There-
the efficacy of the tip detection method during IVUS-
fore, we developed a tip detection method to
based 3D wiring with the new CTO IVUS system
construct IVUS-based 3D images. In the present
(AO-IVUS), which is the first of its kind that has both
study, the number of punctures to the target was
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F I G U R E 7 IVUS-Based 3D Wiring Using the Tip Detection Method
(A) Angiographic (I) and IVUS (II) images just before IVUS-based 3-dimensional (3D) wiring using the tip detection method. (B) Illustrations and IVUS images (I to VI) during IVUS-based 3D wiring. IVUS images (I to III) showing how to construct the mental 3D image. IVUS images (IV to VI) showing that the tip was accurately directed to the true lumen after clockwise rotation. (C) IVUS image and illustration after successful puncture of the guidewire into the true lumen. Abbreviations as in Figure 3.
wiring
moved back and forth in real time according to the
compared with Navi-IVUS–based wiring (1.0 [IQR: 1.0
movement of the guidewire, which will cause further
to 2.0] vs. 24.0 [IQR: 5.8 to 52.5]; p ¼ 0.001). The tip
damage to the CTO lesion and interfere with the
detection method makes the IVUS guided wiring
manipulation of the guidewire. Therefore, the oper-
quite accurate, but without the tip detection method,
ator can only confirm the location of the guidewire
IVUS-guided wiring is much less accurate, and the
after guidewire advancement, which is less accurate.
large IQR means that successful puncture sometimes
If the operator wishes to perform IVUS-based 3D
only occurs by chance.
wiring using the tip detection method, OpitCross
significantly
reduced
in
AO-IVUS–based
(relatively long-tip IVUS, 20 mm) should be used THE SHORT- IP WITH PULLBACK SYSTEM IVUS
despite the disadvantage of longer subintimal space
FACILITATES IVUS-BASED 3D WIRING. The pullback
formation. If IVUS systems with both a short tip and
system is essential to perform IVUS-based 3D wiring
pullback system, such as AO-IVUS, also become
using the tip detection method, and furthermore the
available around the world, IVUS-based 3D wiring
short tip is also desirable to minimize subintimal
using the tip detection method will be widely adopted
space formation. Therefore, we produced AO-IVUS,
and is promising for being able to be used in more
which is an upgraded version of Navi-IVUS (short-
situations after the use of the antegrade guidewire
tip IVUS), by adding a pullback transducer system.
escalation in hybrid strategies (8,9). If the passage of
Outside of Japan, Eagle-Eye IVUS (short-tip IVUS)
a guidewire through the intima is likely to be difficult
(Volcano, Royal Dutch Philips Electronics, Best, the
because of severe calcification or severe bending and
Netherlands) is usually used for IVUS-guided wiring
the distal re-entry site can be visualized, the dissec-
in cases of CTO lesions (7). Eagle-Eye IVUS does not
tion re-entry should be considered. However, if the
have the pullback system. To observe the guidewire
lesions are not severely calcified and severely ben-
shaft and tip, Eagle-Eye IVUS catheter itself should be
ded, the AO-IVUS–guided tip detection will be more
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suitable among the antegrade approaches because the
Osaka, Japan), for preparation of the angiographic
side branches will be preserved due to the true lumen
and IVUS images.
passage. Furthermore, if the vessel course is not unclear and the distal site cannot be visualized, consider
FOR
Okamura,
Sakurabashi-Watanabe
inside the vessel followed by the AO-IVUS guided tip
Umeda
detection method. The IVUS guided tip detection
[email protected]. Twitter: @Aokamura5.
Kitaku,
CORRESPONDENCE:
Dr. Atsunori
ADDRESS
the knuckle wire technique to keep the guidewire
Osaka
530-0001,
Hospital,
2-4-32
Japan.
E-mail:
method usually needs the Confianza-12g to reroute the guidewire into the true lumen at the transition site. This method can navigate the CTO stiff wire throughout the CTO lesion; however, de-escalation to softer wires with lower risks of perforation can be considered for the body of the lesion before the transition site. After the successful passage into the true lumen, the guidewire de-escalation also can be considered.
PERSPECTIVES
WHAT IS KNOWN? We developed an angiography-based 3D wiring method in 2014 and recently reported on its efficacy in our clinical practice for CTO-PCI. We previously produced a short-tip CTO-specific IVUS system (Navi-IVUS) in 2012, which has been commonly used for IVUS-guided wiring for CTO-PCI in Japan.
STUDY LIMITATIONS. As AO-IVUS is still being pre-
pared for clinical use, we demonstrated the efficacy of
WHAT IS NEW? Our final objective was the development of
AO-IVUS–based 3D wiring using the tip detection
IVUS-based 3D wiring allowing most accurate guidewire manip-
method only for experimental CTO lesions and re-
ulation for CTO-PCI. We developed a tip detection method to
ported a clinical case treated by this method with
simplify IVUS-based 3D wiring. To standardize this method in
AltaView IVUS, which has a long tip and pullback
clinical practice, we upgraded Navi-IVUS to AO-IVUS by adding a pullback transducer system and demonstrated the efficacy of
transducer system.
IVUS-based 3D wiring using the tip detection method with AO-
CONCLUSIONS
IVUS.
The tip detection method enables us to easily
WHAT IS NEXT? In the very near future, AO-IVUS will be used
perform the IVUS-based 3D wiring, which will be
in clinical practice in Japan and we will standardize AO-IVUS–
further facilitated by the new CTO IVUS system
based 3D wiring using the tip detection method in clinical prac-
(AO-IVUS).
tice. By continuing to promote this concept internationally, we
ACKNOWLEDGMENTS The authors thank Keiichiro
Yamamoto, Yoichi Ito, Yasunori Yamashita, Soichiro Sugihara,
and
Yuji
Yokomizo
(Terumo,
Tokyo,
Japan) for production of AO-IVUS and Katsutoshi Kawamura,
RT
(Sakurabashi-Watanabe
hope that CTO IVUS with both a short tip and pullback system will become available all over the world, which will lead to standardization of IVUS-based 3D wiring using the tip detection method.
Hospital,
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KEY WORDS chronic total occlusion,
7. Huang WC, Teng HI, Hsueh CH, Lin SJ, Chan WL,
coronary intervention, IVUS-based 3D wiring, tip detection method
Lu TM. Intravascular ultrasound guided wiring
9