Author + information
- Received March 27, 2017
- Revision received June 12, 2017
- Accepted June 29, 2017
- Published online November 6, 2017.
- Scott A. Harding, MDa,∗ (, )
- Eugene B. Wu, MDb,
- Sidney Lo, MBBSc,
- Soo Teik Lim, MDd,
- Lei Ge, MDe,
- Ji-Yan Chen, MDf,
- Jie Quan, MDg,
- Seung-Whan Lee, MD, PhDh,
- Hsien-Li Kao, MDi and
- Etsuo Tsuchikane, MD, PhDj
- aDepartment of Cardiology, Wellington Hospital, Wellington, New Zealand
- bPrince of Wales Hospital, Hong Kong
- cLiverpool Hospital, Sydney, Australia
- dNational Heart Centre, Singapore
- eShanghai Zhongshan Hospital, Shanghai, China
- fGuangdong General Hospital, Guangdong, China
- gBeijing Fuwai Hospital, Beijing, China
- hDepartment of Cardiology, Asan Medical Center, University of Ulsan, Seoul, Republic of Korea
- iDepartment of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan
- jToyohashi Heart Centre, Toyohashi, Aichi, Japan
- ↵∗Address for correspondence:
Dr. Scott A. Harding, Department of Cardiology, Wellington Hospital, Private Bag 7902, Wellington South, New Zealand.
Although the hybrid chronic total occlusion (CTO) algorithm had many excellent recommendations, there has been infrequent adoption in the Asia Pacific region. The Asia Pacific CTO club propose an algorithm for case selection based on the Japan-CTO score and a new CTO algorithm, which is applicable globally. This algorithm allows for differing skill sets and equipment availability and contains practical teaching for CTO percutaneous coronary intervention. Similar to the hybrid algorithm there are 3 main questions that determine whether the primary approach is antegrade or retrograde: 1) is there proximal cap ambiguity; 2) is the distal vessel of poor quality; and 3) are there interventional collaterals present. In contrast to the hybrid algorithm occlusion length alone does not determine the choice of either a wire escalation strategy or a dissection re-entry strategy. Rather a combination of factors including ambiguity of the vessel course, severe calcification, tortuosity, length, and previous failure are used to determine this. The role of intravascular ultrasound–guided entry to overcome proximal cap ambiguity and the CrossBoss catheter in occlusive in-stent restenosis are highlighted in the algorithm. Both the parallel wire technique and dissection re-entry with the Stingray system have been included as options when the initial antegrade wire passage fails. Intravascular ultrasound–guided wiring along with limited subintimal tracking and re-entry are included as final options in the algorithm. Finally, the algorithm incorporates guidance on when to stop the procedure. It is hoped that this algorithm will serve as the basis for future CTO percutaneous coronary intervention proctoring and training.
Chronic total occlusions (CTO) represent one of the most challenging lesion subsets in patients undergoing percutaneous coronary intervention (PCI). Historically CTO PCI was associated with significantly lower success rates and increased adverse events compared with PCI for other lesion subsets (1). Recently there has been a rapid and continuous evolution of CTO equipment and techniques that has driven greater procedural success and improved clinical outcomes. Despite this, success rates remain variable (2) with the best outcomes being reported in centers with dedicated CTO programs and high-volume CTO operators (3–5).
The landmark work by Brilakis et al. (2) describing a percutaneous treatment algorithm for crossing CTO, now commonly referred to as the hybrid algorithm, has become the basis of discussion and reference for CTO PCI worldwide. This algorithm emphasized the importance of dual injections for CTO PCI angiography, promoted careful review and a standardized approach to the evaluation of the coronary angiogram, used the angiographic characteristics to guide selection of the initial strategy, and encouraged early conversion to an alternative crossing strategy if the initial crossing strategy failed. The algorithm has been shown to enhance success rates in complex CTO lesions and to be reproducible and teachable. The same authors are also to be credited with executing a remarkable and efficacious proctoring program that has radically altered the landscape of CTO intervention in North America and Europe (6–8).
Although there are many excellent recommendations within the hybrid algorithm, there has been infrequent adoption of the hybrid algorithm in the Asia Pacific region where most of the world's population resides. This is caused in part by the traditional wire-based CTO teaching that is dominant in the region, and limited access to the CrossBoss and Stingray system (Boston Scientific, Marlborough, Massachusetts), which eliminates the antegrade dissection re-entry arm of the hybrid algorithm. Other factors, such as lower rates of coronary artery bypass grafting (3,9), have also likely contributed to the differences in CTO PCI approaches seen in the Asia Pacific region.
The Asia Pacific CTO club, a group comprised of 10 high-volume CTO operators who are recognized as leaders in CTO intervention in their respective countries, was motivated by the hybrid authors to propose a new algorithm for CTO PCI that would be relevant and applicable globally. This algorithm allows for differing skill sets and equipment availability and contains practical teachings for CTO PCI. It is hoped that this algorithm will serve as the basis for future CTO PCI proctoring and training.
Japan-CTO Score, Case Selection, and Proctoring
Mastering retrograde techniques and the use of the CrossBoss and Stingray system requires training and experience. Although these techniques can be taught it is unlikely that operators will become proficient in all techniques unless they perform a large volume (>50 cases per year) of CTO PCI. However, many skilled PCI operators can perform CTO PCI using antegrade wire escalation techniques with a high degree of success if appropriate cases are selected. We therefore propose an algorithm incorporating the Japan-CTO (J-CTO) score to guide the selection of which cases should be attempted by nonexpert CTO operators and which cases should be referred or performed with the assistance of a proctor (Figure 1).
The J-CTO score was derived from the J-CTO (Multicenter CTO Registry of Japan) registry cohort to predict the probability of successful guidewire crossing within 30 min and is the most widely accepted measure of CTO complexity (10). The J-CTO score is determined by assigning 1 point for each of the following independent predictors of this endpoint: blunt entry stump, calcification, bend >45°, occlusion length >20 mm, and previous failed attempt. The summation of all points accrued is then used to stratify lesions into 4 difficulty groups: easy (J-CTO score of 0), intermediate (score of 1), difficult (score of 2), and very difficult (score of ≥3). As the J-CTO score increases, procedural efficiency and overall success rates fall (10–13).
In the original study a J-CTO score of ≥2 was associated with a <50% chance of successful wire crossing within 30 min (10). A subsequent study performed in the United States by hybrid operators demonstrated that as the J-CTO score increased, the use of the retrograde approach increased markedly with the retrograde approach being the successful approach in 34% of those with a J-CTO score ≥2 compared with only 5% in those with a J-CTO score of <2 (13). We therefore recommend that for cases with a J-CTO score ≥2, operators relatively early in their CTO PCI experience or with a limited range of CTO skills should either seek the assistance of a proctor or refer the case to a CTO expert. A CTO expert can be defined as an operator who has performed at least 200 CTO PCIs, has mastered all the available techniques, and who can achieve a ≥85% success rate in unselected clinically indicated cases.
Proctoring is a powerful tool to improve CTO PCI skills. Sharma et al. (14) found the impact of proctoring to be particularly useful in patients with J-CTO scores of ≥2 with success rates improving from 49.5% to 70.7%. We encourage nonexpert CTO operators to seek proctoring for complex cases where possible and recommend that all retrograde and antegrade dissection re-entry cases should be proctored until the operator has gained competency in these techniques.
The Main Algorithm
The main algorithm (Figure 2) begins with a careful review of the anatomy (coronary angiogram and coronary computed tomography angiography [CCTA] if available). Isolated occlusive in-stent restenosis (ISR) is separated into a distinct category where it is recommended that use of a CrossBoss catheter be considered as the primary crossing strategy.
Similar to the hybrid algorithm there are 3 main questions that determine whether the primary approach is antegrade or retrograde: 1) is there proximal cap ambiguity; 2) is the distal vessel of poor quality; and 3) are there interventional collaterals present. In contrast to the hybrid algorithm the role of intravascular ultrasound (IVUS)–guided entry to overcome proximal cap ambiguity is highlighted in the main algorithm. In our experience ambiguity of the proximal cap is relatively common. We believe IVUS-guided proximal cap entry is an essential skill for CTO operators to acquire and one that can be easily taught and that can resolve proximal cap ambiguity in most cases.
The algorithm also differs from the hybrid algorithm in that the length of the occlusion alone does not determine the choice of either a wire escalation strategy or a dissection re-entry strategy. We acknowledge that lesion length is an important determinant of successful lesion crossing when using a wire escalation strategy wire (10). However, there are several other important factors including ambiguity of the vessel course, tortuosity, degree of calcification, and whether there has been previous failed wiring attempts that should also be taken into account when making this decision, which are highlighted in the main algorithm. The course of the CTO body is considered ambiguous where there is a long length of occlusion with no landmarks, such as calcium, previous stents, or visible channels to indicate the vessel course, and CCTA has not been performed.
The use of the parallel wire technique and IVUS-guided wiring as a last resort has been included as options in the antegrade arm of the algorithm. Parallel wiring can be very effective and not all distal vessels are suitable for re-entry. The use of antegrade dissection re-entry with the Stingray System (Boston Scientific) may also be limited by other factors including availability, expertise, and cost.
Guidance on when to stop a procedure is also incorporated into the main algorithm. This and other aspects of the main algorithm are discussed in more detail next.
Careful analysis of the angiogram is fundamental to planning the CTO PCI strategy and assessing the risk/benefit ratio. Dual injections are an essential component of CTO PCI and should be performed routinely except in cases where there are no contralateral collaterals. Pre-procedural CCTA provides information about the vessel course in the occluded segment, calcification, lesion length, stump morphology, presence of side branches, and post–coronary artery bypass grafting anatomy, which may not be apparent on invasive angiography and may improve procedural success in complex CTO PCI (15). We recommend that pre-procedural CTCA be considered in cases with a high J-CTO score, previous coronary artery bypass grafting, and previous failure. In general CTO PCI should be performed as a planned procedure rather than on an ad hoc basis because this allows time for careful analysis of the angiogram, calculation of the J-CTO score, thorough procedural planning, and informed discussion with the patients.
We recommend that the CrossBoss catheter should be considered as the first-line device for recanalization of occlusive ISR because it facilitates rapid crossing of the ISR segment with high procedural success rates (16). The advantage of the CrossBoss catheter is that its blunt rounded tip generally prevents the device from going underneath stent struts, which results in either inability to cross with devices or deformation of the previously placed stent. If there is diffuse proliferative ISR involving the vessel proximal to the stent then use of a wire to lead the CrossBoss into the stented segment is recommended. Because the CrossBoss is a blunt dissection tool it often requires strong backup support to be advanced through the CTO. Occasionally the proximal cap may be very hard preventing progress of the CrossBoss. To overcome this we recommend puncture of the proximal cap with an intermediate to high penetration force wire and pre-dilation with a small balloon. Once in the ISR segment, the CrossBoss can be advanced by rapid spinning until the CrossBoss has either crossed the CTO or reached the distal stent edge. If the ISR extends distal to the stent then we recommend using a wire to access the distal lumen. If the wire cannot access the distal true lumen after a brief try, the CrossBoss should be delivered further distally. The CrossBoss will either enter the distal true lumen or produce a subintimal space to set up for Stingray re-entry.
Acute angulation in the stented segment is the most common reason for failure of the CrossBoss to pass through occlusive ISR (16). In some of these cases redirection of the CrossBoss catheter within the occlusion using a stiff coronary guidewire may be successful. Other causes of failure include exit of the CrossBoss into a side branch or the subintimal space when there is a gap between stents in the occlusive segment, stent fracture, stent deformation, or gross stent underdeployment. Therefore, it is important to review the angiogram closely to identify such issues.
IVUS Guidance to Overcome Proximal Cap Ambiguity
Proximal cap ambiguity is encountered frequently and represents a major barrier to a successful antegrade approach to CTO PCI. Accurate identification of the proximal cap is essential to allow safe and successful antegrade wiring. If ambiguity of the proximal cap is present we should resolve this using IVUS guidance. The IVUS catheter should be placed in the branch closest to the region of the proximal cap and angiograms in multiple views taken when the IVUS is located at the proximal cap. Use of an 8-F guiding catheter is required to accommodate a Corsair (Asahi Intecc, Nagoya, Japan) and an IVUS catheter at the same time allowing wiring of the proximal cap using real-time IVUS guidance. However, use of a lower-profile microcatheter, such as the Caravel (Asahi Intecc), allows accommodation of an IVUS catheter at the same in a 7-F guiding catheter. In addition, IVUS also provides information regarding the composition of the cap and can help to guide the initial wire choice. Occasionally, there may be no side branch near the cap suitable for IVUS or IVUS may fail to resolve the ambiguity. In such cases retrograde wiring up to the proximal cap or techniques that “move the cap,” such as balloon-assisted subintimal re-entry or the “scratch-and-go,” technique can be used to overcome proximal cap ambiguity and progress the case (17).
Antegrade Preparation First Philosophy
The importance of overcoming proximal cap ambiguity with IVUS is part of our “antegrade preparation first” philosophy. Even if we plan to use retrograde, antegrade preparation should be performed beforehand in most cases. The rationale for this is that antegrade preparation first reduces the time the retrograde system is engaged and thus reduces donor artery risk and CTO territory ischemic time (particularly if the collateral is dominant). It also encourages going directly to reverse controlled antegrade retrograde tracking (CART), which is the most efficient way to attain retrograde wire crossing. Finally, the antegrade preparation first philosophy removes the risks of single retrograde wire crossing in ostial lesions.
Antegrade Wire Escalation
If there is no proximal cap ambiguity or if it can be resolved by use of IVUS then antegrade wire escalation is the preferred initial strategy in most cases. Even if unsuccessful it can serve as preparation for either antegrade dissection re-entry or a retrograde approach and may avoid the need for or reduce the length of subintimal dissection. However, it is important not to get “stuck in a failure mode” with antegrade wiring expending contrast, radiation, and time with little progress thereby eliminating the possible use of other strategies.
There are multiple wires on the market that are promoted for use in CTO PCI and several different techniques for using these wires including sliding, intentional intimal tracking, controlled drilling, penetration, and subintimal tracking. The most commonly used CTO wires and their properties are listed in Table 1. We outline a strategy for antegrade wire escalation (Figure 3) but accept wire choice is driven by operator familiarity and availability.
Microcatheters should routinely be used in conjunction with the guidewire as part of CTO PCI procedures. Microcatheters allow for rapid exchange of guidewires while maintaining wire position and improve guidewire torque response. Microcatheters also improve support and allow the penetration power of the guidewire to be altered dynamically by changing the distance between the microcatheter tip and wire tip. The Corsair and Turnpike (Vascular Solutions, Minneapolis, Minnesota) microcatheters have good penetration power and are excellent for antegrade CTO crossing and retrograde channel crossing.
Angiographic morphology can guide initial guidewire choice for proximal cap penetration. If IVUS interrogation of the proximal cap has been performed this is also very helpful delineating cap morphology and can guide guidewire choice. If there is a functional CTO or partial recanalization with visible channels we recommend starting with a tapered polymer jacketed wire with a low tip load, such as the Fielder XT-R (Asahi Intecc). The tapered tip facilitates entry into the microchannel, the polymer jacket enhances lubricity and trackability, and the low tip load reduces the likelihood of the guidewire exiting the microchannel.
If the proximal cap has a tapered morphology this often signifies that the occlusion is more recent and has a softer composition (18). In these cases we recommend starting with a Fielder XT-A (Asahi Intecc), or other low penetration force wire. If this is unsuccessful then escalation to an intermediate penetration force guidewire, such as the GAIA 2nd (Asahi Intecc) or Pilot 200 (Abbott Vascular, Santa Clara, California), and if necessary to a high gram-force wire with a tapered tip, such as the Conquest Pro or Conquest Pro 12 (Asahi Intecc), should be undertaken.
It the proximal cap has a blunt morphology this often signifies that the occlusion is older and is likely to have a tougher composition. We recommend use of an intermediate penetration force wire as the initial wire in combination with a microcatheter with good penetration properties, such as the Corsair or Turnpike in these cases. If penetration is unsuccessful further escalation to a high penetration force guidewire is recommended.
If a high penetration force guidewire has been used to puncture the proximal cap it is important to step down to a lower penetration force wire, unless the occlusion is short and the course unambiguous. Stepping down to an intermediate nontapered wire, such as the MiracleBros 3 (Asahi Intecc) or Pilot 200, reduces the risk of perforation and increases the chance of tracking the vessel.
Once the distal cap is reached it may be necessary to step up to a wire with a higher penetration force to puncture through the distal cap into the distal true lumen. It is very important to control the wire tip intentionally to the direction of the distal true lumen with examination of the angiogram from several different angles before attempting to penetrate the distal cap.
When to Knuckle Wire
The knuckle wire has become an important tool in both antegrade and retrograde CTO PCI. The major benefit of the knuckle wire is that it allows occluded segments to be negotiated rapidly with a low perforation risk even in the presence of anatomic ambiguity. However, as the knuckle tracks the subintimal space, a mechanism for re-entry into the true lumen distal to occlusion segment is required, usually the Stingray system for the antegrade approach and reverse CART for the retrograde approach. Polymer jacketed guidewires, such as the Fielder XT (Asahi Intecc) or the Pilot 200, are the most commonly used wires for knuckling. The Gaia 2nd wire can also be effectively knuckled. It is preferable to keep the size of the knuckle as small as possible to minimize vessel trauma. The knuckle formed by the Fielder XT wire tends to be smaller than those formed by the Pilot 200 wire. The knuckle diameter can also be controlled to some degree by keeping the microcatheter close to the knuckle. It is important to avoid rotation of the knuckle wire to avoid knotting the guidewire. When the knuckle wire is being used as part of antegrade dissection re-entry it is important to stop the knuckle before the re-entry zone and use the CrossBoss to extend the subintimal space into the re-entry zone, thereby minimizing the subintimal space at the re-entry site and increasing the chances of successful true lumen re-entry using the Stingray system.
In this algorithm anatomic ambiguity rather than lesion length is the primary reason for considering use of a knuckle wire and a dissection re-entry strategy. We also recognize the value of using a knuckle wire and dissection re-entry techniques in heavily calcified and tortuous vessels where the success rates are lower and the risks of perforation higher with wire escalation strategies. In CTO lesions longer than 20 mm and in those with a previous failed attempt, antegrade wire escalation can result in successful crossing particularly when other anatomic features are favorable (yielding a low J-CTO score).
Parallel Wiring Versus Antegrade Dissection Re-Entry
Use of the parallel wire technique and IVUS-guided wiring are included as options in the antegrade arm of the main algorithm. The parallel wire technique has been a widely used and successful strategy to facilitate the passage of the guidewire into the true lumen when the first antegrade wire has failed. In this technique the initial guidewire is left in place as a marker and to obstruct the false channel. A second stiffer wire supported by a microcatheter is then advanced parallel to the first wire until the point of the first wire is thought to have deviated; this is often detectable by a subtle inflection in the course of the first wire. The second wire is then directed toward the distal target and advanced into the true lumen.
Antegrade dissection re-entry using the dedicated Stingray system has been shown to improve procedural success rates and efficiency particularly in those with high J-CTO scores (19). However, not all lesions are suitable for antegrade dissection re-entry and effective use of the Stingray system requires training. Lack of availability and cost may also limit use in some countries. For the Stingray system to be successful, it should be used early before any significant subintimal space expansion has occurred in the re-entry zone.
When using antegrade wire escalation as the initial strategy, if the guidewire goes past the distal cap into the subintimal space a decision needs to be made on how to proceed. If the initial guidewire position is close to the distal true lumen it is reasonable to attempt redirection of the wire into the distal true lumen. The Gaia series of wires (Asahi Intecc) are particularly effective for this because of their high torque control. However, if this fails a decision needs to be made whether to continue with wire-based techniques, change to dissection re-entry, or change to a retrograde approach. This choice is determined by the presence of interventional collaterals, the operators skill set, equipment availability, and anatomic factors. A relatively disease-free re-entry zone, close proximity of the antegrade wire to the distal true lumen, and the absence of severe calcification in the re-entry zone all favor re-entry with the Stingray system. Conversely, the presence of severe disease, calcification, or a bifurcation in the re-entry zone favors parallel wiring or a retrograde approach.
When the Stingray system is not available and both antegrade wiring and retrograde strategies have failed then IVUS-guided wiring may be used as a last resort. To perform this, a 1.5-mm balloon is advanced over the antegrade wire and inflated in the subintimal space to allow delivery of an IVUS catheter. IVUS is then used to determine the location of the true lumen and direct a second antegrade high penetration force wire, such as a Conquest Pro, from the subintimal space toward the distal true lumen.
The retrograde approach is an essential component of CTO PCI and use of this approach has substantially increased success rates in complex CTO PCI (7). A detailed discussion of the retrograde approach and the related problem solving is beyond the scope of this article and will be the focus of a subsequent paper. A brief overview of our approach is discussed next.
Use of the retrograde approach requires the presence of an interventional collateral. Failure of collateral crossing remains the most common cause of failure of the retrograde approach (20). Once the retrograde channel is crossed with the guidewire, the retrograde microcatheter is advanced to the distal cap. In cases with a nonambiguous vessel course without other adverse anatomic features we recommend use of contemporary reverse CART to facilitate retrograde crossing. In contemporary reverse CART a small balloon, usually 2.0 mm, is advanced antegradely as distally as possible and inflated. An intermediate to high penetration force wire with good torque control, such as the GAIA 2nd or 3rd, is then advanced retrogradely before there is subintimal space expansion distal to the CTO and intentionally directed toward the antegrade balloon. The antegrade balloon is then deflated and the retrograde wire advance into the balloon space.
Similar to antegrade wire escalation, use of a knuckle wire is favored when there is anatomic ambiguity that cannot be overcome by advancement of the antegrade wire or when there is a combination of the following: tortuosity, calcification, and a long occlusion length. In these cases, once there is overlap of the retrograde knuckle wire with the antegrade wire, reverse CART can then be performed. If there is difficulty making the connection IVUS guidance should be used to determine the location of the antegrade and retrograde wires and select the appropriate strategy. Use of a guide extension catheter to facilitate reverse CART or so-called guide-extension reverse CART has become common practice. This is particularly useful where there is a significant length of disease or dissection in the target vessel proximal to the connection site and where the retrograde microcatheter is unable to reach the anterograde guide catheter because of long collateral channel course (21). Once the connection has been made and the retrograde wire advanced into the guide or guide extension catheter wire externalization can be performed with subsequent antegrade ballooning and stenting.
When to Stop
Knowing when to stop is a key issue in CTO PCI. It is important to balance the potential risks of a significant complication with the chance of procedural success when deciding whether or not to stop the procedure. Our algorithm provides specific guidance suggesting that operators should consider stopping a CTO procedure if the procedure time is >3 h, if more than 3.7 ml × the estimated glomerular filtration rate of contrast has been used or if the radiation dose is >5 Gy air kerma unless the procedure is well advanced. The procedure being well advanced can be defined as having the antegrade wire in the distal true lumen, having the stingray catheter in position in the re-entry zone, or having crossed the collateral channel with the retrograde wire and microcatheter. These cutoffs are based on the published literature that suggests the risk of radiation skin injury and contrast nephropathy increases significantly beyond these limits (22,23).
Algorithms provide an important platform for discussion, have proven to be an effective tool for proctoring, and have advanced the practice and success of CTO PCI. Rapid technological developments in the area of CTO PCI have led to some increase in CTO PCI success rates, but further improvements are heavily dependent on expansion of CTO PCI knowledge. The difficulties in applying the hybrid algorithm in the Asia Pacific region has led us, the Asia Pacific CTO club, to develop an algorithm for CTO PCI that is globally relevant. Further studies are needed to confirm not only the success rates of CTO PCI using this algorithm, but more importantly the success of proctoring CTO PCI with this algorithm.
Dr. Harding has received speaking and consultancy fees from Boston Scientific, Medtronic, Bio-Excel, and Asahi Intecc. Dr. Wu has received proctoring fees from Boston Scientific; and has stock ownership in Abbott and Medtronic. Dr. Lo has received speaking and proctoring honoraria from Bio-Excel. Dr. Lim has received research grant/travel support or speaker honorarium from Orbus Neich, Asahi Intecc, Terumo, Biosensors, Biotronik, Abbott Vascular, Aluimedica, Boston Scientific, and Keneka. Dr. Tsuchikane is a consultant for Boston Scientific, Asahi Intecc, and Nipro. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- Abbreviations and Acronyms
- controlled antegrade and retrograde tracking
- coronary computed tomography angiography
- chronic total occlusion
- in-stent restenosis
- intravascular ultrasound
- Japan-CTO Score
- percutaneous coronary intervention
- Received March 27, 2017.
- Revision received June 12, 2017.
- Accepted June 29, 2017.
- 2017 American College of Cardiology Foundation
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- Graphical abstract
- Japan-CTO Score, Case Selection, and Proctoring
- The Main Algorithm
- Anatomic Analysis
- In-Stent Restenosis
- IVUS Guidance to Overcome Proximal Cap Ambiguity
- Antegrade Preparation First Philosophy
- Antegrade Wire Escalation
- When to Knuckle Wire
- Parallel Wiring Versus Antegrade Dissection Re-Entry
- Retrograde Subalgorithm
- When to Stop