Author + information
- Received March 26, 2019
- Revision received July 25, 2019
- Accepted July 30, 2019
- Published online January 6, 2020.
- Atsunori Okamura, MDa,∗ (, )@Aokamura5,
- Katsuomi Iwakura, MDa,
- Mutsumi Iwamoto, MDa,
- Hiroyuki Nagai, MDa,
- Akinori Sumiyoshi, MDa,
- Kota Tanaka, MDa,
- Takamasa Tanaka, MDb,
- Koichi Inoue, MDa,
- Yasushi Koyama, MDa and
- Kenshi Fujii, MDa
- aDivision of Cardiology, Sakurabashi Watanabe Hospital, Osaka, Japan
- bDivision of Cardiovascular Medicine, Hyogo College of Medicine, Hyogo, Japan
- ↵∗Address for correspondence:
Dr. Atsunori Okamura, Sakurabashi-Watanabe Hospital, 2-4-32 Umeda Kitaku, Osaka 530-0001, Japan.
Objectives This 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 s [interquartile range: 44.0 to 112.3 s] vs. 333.0 s [interquartile range: 88.8 to 790.0 s]; p = 0.036; median 1.0 puncture [interquartile range: 1.0 to 2.0 punctures] vs. 24.0 punctures [interquartile range: 5.8 to 52.5 punctures]; p = 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.
Accurate guidewire control is essential to improve and standardize percutaneous coronary intervention (PCI) for chronic total occlusion (CTO) lesions. In collaboration with Terumo Corporation (Tokyo, Japan), we produced a CTO-specific intravascular ultrasound (IVUS) system, Navifocus WR IVUS (Navi-IVUS), in 2012 (1,2). This IVUS system has a small-profile transducer (2.5-F) with a short tip-to-transducer length (9 mm) to allow insertion into the subintimal space with minimal vessel damage. Owing to the long proximal monorail lumen (26 cm in length), this IVUS system can maintain good deliverability in CTO lesions despite the short tip-to-transducer length.
Our clinical experience with Navi-IVUS–guided wiring indicated that 3-dimensional (3D) imaging is important for accurate guidewire control in CTO-PCI. Therefore, we developed an angiography-based 3D wiring method (3), which we have been using in our clinical practice since 2014. Recently, we reported the efficacy of angiography-based 3D wiring in our clinical practice (4). 3D wiring enables accurate guidewire control, which improves the success rate of antegrade wiring and reduces the antegrade procedure time, resulting in improvements of the overall success rate. However, if the guidewire is inserted into the subintimal space, it is necessary to move on to other strategies, such as the retrograde approach (5), dissection re-entry (6), or IVUS-guided wiring (1,2). 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 IVUS-based 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.
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 guide catheter with a Corsair microcatheter (Asahi Intecc, Aichi, Japan) for the second guidewire. However, AO-IVUS still cannot be inserted into a 6-F guide catheter with any other microcatheters for the second guidewire. The AO-IVUS has the same functionality as described for Navi-IVUS (2); the double monorail lumen system maintains a fixed asymmetrical structure, which is a proximal marker next to the transducer and the IVUS’ own guidewire, which can transfer the direction of the IVUS image to that of the angiographic image for accurate navigation of the next guidewire into the true lumen on both the IVUS image and the angiographic image.
Methodology of IVUS-based 3D wiring using the tip detection method
Previously, we reported 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 IVUS-based 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).
Experimental CTO lesion and IVUS-based wiring
Figure 3A shows the experimental CTO lesion for wiring. We used an experimental beating heart model (Terumo) and created a target pinpoint penetration model (3,4) for IVUS-based 3D wiring. A CTO lesion 20 mm in length and 3.0 mm in diameter was made of 2.5% agar and inserted into the mid-right coronary artery. The target, which was a Sniper microcatheter (Terumo) with a 0.6-mm lumen, was placed in the distal part of the CTO lesion.
Figure 3B shows IVUS-based wiring using Navi-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 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 one-direction fluoroscopic image and the IVUS image just beyond the target. In AO-IVUS based wiring, the second guidewire was advanced using the one-direction fluoroscopic image and IVUS images from the target to the tip area to perform IVUS-based 3D wiring using the tip detection method. These IVUS-based wirings were performed 8 times each and the crossing time and number of punctures to the target were calculated.
All data are given as median (interquartile range [IQR]). The 2 groups were independent because we used different experimental vessel models in every procedure. Mann-Whitney U test was used to assess differences between the 2 groups using SPSS version 22.0 (IBM Japan, Tokyo, Japan) and p < 0.05 was considered to indicate a statistically significant difference.
Representative AO-IVUS–based 3D wiring using the tip detection 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). Then, the IVUS-based 3D image construction was performed by moving the transducer back and forth from the target to the tip area to allow visualization of the 3D image in real time (Figure 5BI), which allowed the second guidewire to be accurately advanced to the target while rotating in a counterclockwise direction (Figures 5BII to 5BIV). The second guidewire was inserted into the target in the first puncture (Figures 5CI and 5CII).
Comparison of crossing time and number of punctures to the target of IVUS-based wiring
The crossing time of IVUS-based wiring was significantly shortened using AO-IVUS compared with Navi-IVUS (80.5 s [IQR: 44.0 to 112.3 s] vs. 333.0 s [IQR: [88.8 to 790.0 s]; p = 0.036) (Table 1). The number of punctures to the target was significantly reduced using AO-IVUS compared with Navi-IVUS (1.0 puncture [IQR: 1.0 to 2.0 punctures] vs. 24.0 punctures [IQR: 5.8 to 52.5 punctures]; p = 0.001) (Table 1).
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 tip-to-transducer length (22 mm). It is commonly used in Japan and the specifications are similar to those of OptiCross IVUS (Boston Scientific, Natick, Massachusetts), which is widely used around the world.
A female patient in her seventies with stable 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 into the right coronary artery. A GAIA Second (Asahi Intecc) and then a Confianza-12g guidewire supported by a Corsair microcatheter could not pass through the 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 advanced into the subintimal space 3 cm beyond the entrance of the CTO, and the Corsair was advanced 2 cm beyond the entrance to create the space for the IVUS catheter. Then, the AltaView IVUS was advanced through the Ultimate Bros3, which revealed that the Ultimate Bros3 had entered into the subintimal space 1 cm distal from the entrance of the CTO (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).
In the present experimental study, we demonstrated the efficacy of the tip detection method during IVUS-based 3D wiring with the new CTO IVUS system (AO-IVUS), which is the first of its kind that has both a short tip and a pullback transducer system. As this IVUS is still being prepared for clinical use, we reported the tip detection method in a clinical case using the regular IVUS system (AltView IVUS).
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 lumen on angiographic images. However, to construct a 3D image, it is necessary to observe the guidewire tip as well as the guidewire shaft and target. Therefore, we developed a tip detection method to construct IVUS-based 3D images. In the present study, the number of punctures to the target was significantly reduced in AO-IVUS–based wiring compared with Navi-IVUS–based wiring (1.0 puncture [IQR: 1.0 to 2.0 punctures] vs. 24.0 punctures [IQR: 5.8 to 52.5 punctures]; p = 0.001). The tip detection method makes the IVUS guided wiring quite accurate, but without the tip detection method, IVUS-guided wiring is much less accurate, and the large IQR means that successful puncture sometimes only occurs by chance.
The short-TIP with pullback system IVUS facilitates IVUS-based 3D wiring
The pullback system is essential to perform IVUS-based 3D wiring using the tip detection method, and furthermore the short tip is also desirable to minimize subintimal space formation. Therefore, we produced AO-IVUS, which is an upgraded version of Navi-IVUS (short-tip IVUS), by adding a pullback transducer system. Outside of Japan, Eagle-Eye IVUS (short-tip IVUS) (Volcano, Royal Dutch Philips Electronics, Best, the Netherlands) is usually used for IVUS-guided wiring in cases of CTO lesions (7). Eagle-Eye IVUS does not have the pullback system. To observe the guidewire shaft and tip, Eagle-Eye IVUS catheter itself should be moved back and forth in real time according to the movement of the guidewire, which will cause further damage to the CTO lesion and interfere with the manipulation of the guidewire. Therefore, the operator can only confirm the location of the guidewire after guidewire advancement, which is less accurate. If the operator wishes to perform IVUS-based 3D wiring using the tip detection method, OpitCross (relatively long-tip IVUS, 20 mm) should be used despite the disadvantage of longer subintimal space formation. If IVUS systems with both a short tip and pullback system, such as AO-IVUS, also become available around the world, IVUS-based 3D wiring using the tip detection method will be widely adopted and is promising for being able to be used in more situations after the use of the antegrade guidewire escalation in hybrid strategies (8,9). If the passage of a guidewire through the intima is likely to be difficult because of severe calcification or severe bending and the distal re-entry site can be visualized, the dissection re-entry should be considered. However, if the lesions are not severely calcified and severely bended, the AO-IVUS–guided tip detection will be more suitable among the antegrade approaches because the side branches will be preserved due to the true lumen passage. Furthermore, if the vessel course is not unclear and the distal site cannot be visualized, consider the knuckle wire technique to keep the guidewire inside the vessel followed by the AO-IVUS guided tip detection method. The IVUS guided tip detection 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.
As AO-IVUS is still being prepared for clinical use, we demonstrated the efficacy of AO-IVUS–based 3D wiring using the tip detection method only for experimental CTO lesions and reported a clinical case treated by this method with AltaView IVUS, which has a long tip and pullback transducer system.
The tip detection method enables us to easily perform the IVUS-based 3D wiring, which will be further facilitated by the new CTO IVUS system (AO-IVUS).
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.
WHAT IS NEW? Our final objective was the development of IVUS-based 3D wiring allowing most accurate guidewire manipulation for CTO-PCI. We developed a tip detection method to simplify IVUS-based 3D wiring. To standardize this method in clinical practice, we upgraded Navi-IVUS to AO-IVUS by adding a pullback transducer system and demonstrated the efficacy of IVUS-based 3D wiring using the tip detection method with AO-IVUS.
WHAT IS NEXT? In the very near future, AO-IVUS will be used in clinical practice in Japan and we will standardize AO-IVUS–based 3D wiring using the tip detection method in clinical practice. By continuing to promote this concept internationally, we 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.
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 Hospital, Osaka, Japan), for preparation of the angiographic and IVUS images.
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.
- Abbreviations and Acronyms
- AnteOwl intravascular ultrasound
- chronic total occlusion
- intravascular ultrasound
- Navifocus WR intravascular ultrasound
- percutaneous coronary intervention
- Received March 26, 2019.
- Revision received July 25, 2019.
- Accepted July 30, 2019.
- 2020 The Authors
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