Author + information
- Nicholas J. Lembo, MD∗ (, )
- Raja Hatem, MD and
- Dimitri Karmpaliotis, MD, PhD
- Center for Interventional Vascular Therapy, Division of Cardiology, Department of Medicine, Columbia University Medical Center, New York, New York
- ↵∗Address for correspondence:
Dr. Nicholas J. Lembo, Center for Interventional Vascular Therapy, Division of Cardiology, Department of Medicine, Columbia University Medical Center, 161 Fort Washington Avenue, HIP 6-610, New York, New York 10032.
Dating back as far as 1985, many small series have reported their own predictors of primary success and failure modes in chronic total occlusion (CTO) percutaneous coronary intervention (PCI) (1,2). Early predictors of failure included increasing age of the occlusion, presence of calcium, presence of a nontapered stump, excessive tortuosity of occluded vessels, long occlusion length, presence of side branches at the proximal cap, bridging collateral vessels, and lack of visibility of the distal bed (3). These early predictors of success and failure were reported before the development of retrograde and antegrade dissection re-entry techniques.
Fast-forward to 2011: Morino et al. (4) reported on 494 native CTO lesions and developed the J-CTO (Multicenter CTO Registry in Japan) score. The objective parameter of the score was to determine the different parameters that influenced successful guidewire crossing within 30 minutes of starting the case. Independent predictors of failure to do so included calcification, vessel tortuosity, ambiguous cap, occlusion length, and prior failed procedure in the CTO territory. The score is then categorized as easy, intermediate, difficult, or very difficult. Subsequent validations of the score have demonstrated positive results pertaining to final success rates in relation to initial J-CTO score (5).
In 2015, Alessandrino et al. (6) described independent predictors of CTO PCI failure that included clinical and lesion-related scores: previous coronary artery bypass graft surgery, previous myocardial infarction, severe calcification, CTO lesion length ≥20 mm, non–left anterior descending coronary artery location, and blunt cap. Success rates varied from 85% for the lowest scores to 32% for the highest ones.
In 2016, the PROGRESS-CTO (Prospective Global Registry for the Study of Chronic Total Occlusion) research group reported its own predictors of successful CTO PCI based on of an extensive multicenter registry (7). Technical success was achieved in 93% of cases, demonstrating that implementing the validated hybrid algorithm for CTO PCI resulted in better success rates compared with historical series. On multivariate analysis, the independent predictors of failure were proximal cap ambiguity, moderate to severe tortuosity, left circumflex coronary artery CTO, and absence of interventional collateral vessels. Subsequent validation of the PROGRESS-CTO score demonstrated that it performed similarly to the J-CTO score in predicting procedural success.
Additional scores integrating the use of coronary computed tomographic angiography have also been evaluated for predicting efficient guidewire crossing and procedural success (8).
In summary, multiple factors have been associated with predicting success or failure in CTO PCI. Multivariate predictors that surfaced most frequently over the years were lesion length, calcification, severe tortuosity, and proximal cap ambiguity. Moving forward, with more modern techniques and the systematic application of the hybrid algorithm, newer predictors such as quality of the distal vessel and quality of interventional collateral vessels have also surfaced as good discriminators.
In their study reported in this issue of JACC: Cardiovascular Interventions, Ellis et al. (9) collected data from 7 clinical sites and 9 experienced but not ultra-high-volume operators implementing the hybrid approach (average 61 cases per year, technical success rate 79.4%). Only angiographic variables were studied and evaluated as predictors of CTO PCI success.
Failure was correlated mostly with the presence of an ambiguous proximal cap. In that situation, collateral vessels (Werner classification and level of tortuosity) added to retrograde tortuous trajectory scores were further associated with lower success rates, if elevated. In the absence of an ambiguous proximal cap, angiographic predictors of failure were poor distal target, occlusion length ≥10 mm, ostial location of the CTO, and the procedure’s being done by a certain operator G. This model yielded very good technical success predictability as measured by strong C statistics of 0.753 for the training cohort and 0.738 for the validation cohort. This score was, therefore, more superior at predicting technical success rates, in a statistically significant way, than either the J-CTO (0.55) or PROGRESS-CTO (0.61) score (p < 0.05).
This new model offers several advantages to previous models for predicting coronary CTO success and failure. Powerful predictors were the presence of an ambiguous proximal cap or of a poor landing zone, which are 2 key features of the hybrid algorithm. Occlusion length ≥20 mm, a key feature in selecting a PCI strategy in the hybrid algorithm, was not well correlated with technical success in this study population. Furthermore, it incorporates the suitability of collateral vessels, which is a major strategy in contemporary CTO PCI.
That being said, a major limitation of this model is the complex definition used for the fourth variable of the hybrid algorithm (i.e., interventional collateral vessels). The investigators used a 4-step grading system to define interventional collateral vessels involving: 1) the Werner classification; 2) the number of septal vessels fulfilling at least Werner criterion 1B; 3) tortuosity classification; and 4) the presence or absence of a 90° turn into or out of the best interventional collateral vessel. We do not believe that operators will use this complex definition in their day-to-day clinical practice. Operators will likely use their own definition of a suitable interventional collateral vessel, which is “Can I get through this vessel?” In other words, what constitutes a usable collateral vessel is highly dependent on operator skill and familiarity and access to novel tools such as new specialized wires and microcatheters. One comment worth making regarding proximal ambiguity is that it is not a binary distinction. Although less discussed along these lines compared with interventional collateral vessels, the way a proximal cap is dealt with may be as challenging as dealing with a difficult collateral vessel.
An inherent limitation of any predictive model is wide variability in operator experience. In this model, operator G was an independent predictor of failure. Therefore, because most CTO operators are likely to be low- or medium-volume operators and therefore less skilled than the operators in this study, the widespread clinical predictability of success or failure using this model will likely be less, but it could be more useful as a research tool.
Finally, it is important to keep in mind that scoring systems should not be used to decide whether CTO PCI is indicated or actually performed. They are continuously improving in predicting success, and of note, there is some preliminary evidence that they may predict complications. CTO PCI is maturing as a subspecialty in interventional cardiology, and interventionalists should use these scores and their clinical judgment and be willing to refer high-end, complex cases to regional and national centers of excellence to maximize the benefit to their patients.
In conclusion, Ellis et al. (9) have developed an improved model for predicting coronary CTO PCI success using the hybrid approach, but it may have limited day-to-day clinical applicability for CTO operators because of the complex and difficult process involved in their classification of collateral vessels.
↵∗ Editorials published in JACC: Cardiovascular Interventions reflect the views of the authors and do not necessarily represent the views of JACC: Cardiovascular Interventions or the American College of Cardiology.
Dr. Lembo is on the Speakers Bureau for Boston Scientific, Abbott Vascular, and Medtronic Vascular; and is a member of the Abbott Vascular Medical Advisory Board. Dr. Karmpaliotis has received honoraria from Boston Scientific, Abbott Vascular, Medtronic, and Vascular Solutions. Dr. Hatem has reported that he has no relationships relevant to the contents of this paper to disclose.
- 2017 American College of Cardiology Foundation
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