A coronary artery chronic total occlusion (CTO) is defined as an occlusion present for 3 or more months, which will feature classic histopathologic changes (Fig. 35-1). Although considered separately in this book, the treatment decisions for coronary revascularization should focus on coronary physiology and ischemia rather than specific anatomic considerations. To that end, the indications for treatment of CTOs should be indistinguishable from 95% coronary lesions. However, once the decision to treat a CTO percutaneously is chosen, the technical aspects of this treatment diverge significantly from standard coronary intervention. For many interventionalists, CTOs continue to represent a major technical challenge.

Percutaneous coronary intervention (PCI) is invariably predicated upon a steerable guide wire spanning the target lesion and acting as a rail over which devices can be delivered. Typically, this wire is tracked in the vessel lumen using angiography as a guide. In the absence of a visible lumen during angiography, tracking the coronary vessel and ensuring an intraluminal position can be difficult. Thus, the primary challenge of CTO PCI lies in initially traversing the target lesion with a guide wire. In recent years, important strategic and technical advancements have been made that facilitate overcoming this essential challenge in a reproducible fashion.¹ Most major PCI programs now have, or are planning for, specialized competence in contemporary CTO procedures. An understanding of the field has become essential knowledge for all interventionalists and arguably for any cardiologist who advises patients regarding revascularization options. The goal of this chapter is to describe the technical and strategic considerations necessary to understand CTO PCI.

Angiography for CTO PCI should emphasize simultaneous dual injections to visualize the antegrade and retrograde coronary flow, thus defining the extent of the lesion. Access choice is up to the operator’s discretion recognizing that 2 arterial access points are typically required. Frequently, at least 1 of the access points is 8 Fr to facilitate specific techniques described below. The relative merits of potentially larger sheath/guide sizes via femoral access can be weighed against the reduction in vascular complications and improved patient comfort when radial access is used.^2,3 When femoral access is chosen, long (45-cm) sheaths can overcome iliac tortuosity and increase guide catheter support. Guiding catheter size is usually limited to 6-Fr from the radial approach, although sheathless 7-Fr systems are increasingly common. Good passive support with coaxial alignment is crucial, especially in complex CTO procedures. Although the choice of the guiding catheter shape is generally dictated by personal experience, it is important for operators to seek a guide with optimal support at the onset of the procedure rather than accepting one with merely satisfactory support. The radial operator should be familiar with active guide manipulation to augment “pushability,” and all operators should be versed in balloon anchoring and mother-and-child techniques to improve support when needed.⁴

Even if the distal vessel bed is opacified by ipsilateral collaterals, this opacification can be limited following wire or catheter advancement, resulting in preferential collateral shift to contralateral collaterals during the procedure. Therefore, to achieve the best diagnostic angiography (ie, to fill the entire collateral bed), contralateral injection should be performed at the start of the procedure if any visible contralateral collaterals are present. Operators from the EuroCTO Club have used contralateral injection in 62% of their cases,⁵ whereas dual injection was used in 78% of cases in a more recent North American series.⁶ Dual-injection collateral analysis is performed best using low magnification, so that the entire coronary tree is visualized without panning. Careful study of the collaterals not only provides important information in choosing the most appropriate collateral, but will also alert the operator to the risk of ischemia and hemodynamic or electrical instability if the wired collateral becomes occluded. Three typical collateral pathways are demonstrated in Figures 35-2, 35-3, and 35-4. A careful and detailed review of the angiogram is critical for creating primary and alternative CTO treatment strategies to optimize the efficacy, efficiency, and safety of the procedure.⁷

Anticoagulation during CTO PCI is best achieved with unfractionated heparin (UFH) because it allows for titration of the anticoagulant effect. The desired activated clotting time (ACT) recommended by many operators during retrograde CTO PCI to minimize the risk of donor vessel (ie, the vessel that provides the collateral) and guide thrombosis is >350 seconds, as opposed to the more routine 250 seconds used in typical PCI. Bivalirudin requires ongoing coronary circulation and exposure to blood to maintain its pharmacotherapeutic effect and therefore has the potential for higher guide catheter thrombosis rates in CTO PCI. As with all PCI, preloading with a P2Y₁₂ adenosine diphosphate (ADP) receptor inhibitor and aspirin is important to reduce the risk of acute stent thrombosis and periprocedural myocardial infarction.

Predicting the difficulty of CTO crossing with a guide wire is important for case selection and procedural planning. The Multicenter CTO Registry of Japan (J-CTO) score is determined by assigning 1 point to each of the following 5 variables: (1) previously failed lesion, (2) blunt type of entry, (3) calcification, (4) bending, and (5) occlusion length. Patients are classified into 4 difficulty groups: easy (J-CTO score of 0), intermediate (a score of 1), difficult (a score of 2), and very difficult (a score of 3 or higher). The J-CTO score correlated well with the probability of successful guide wire crossing within 30 minutes (87.7%, 67.1%, 42.4%, and 10.0%, respectively)⁸ and was recently validated in an independent single-center Canadian cohort.⁹ Recent reports using a hybrid-based CTO algorithm have shown that the J-CTO score predicts an increasing need for retrograde procedures to achieve success (Fig. 35-5). More recently, the Prospective Global Registry for the Study of Chronic Total Occlusion (PROGRESS CTO) score has been developed to predict procedural success using hybrid methodologies.¹⁰

Antegrade Guide Wire Approach

Antegrade guide wire–based recanalization of CTOs has been and remains the most common approach worldwide.^11-13 In general, an over-the-wire catheter is delivered to the proximal cap on a workhorse wire, and then CTO-specific wires and wire tip shapes are applied. The approach of gradually escalating wire stiffness to achieve crossing has been generally abandoned in favor of an antegrade wire modification strategy that employs 3 or 4 wires chosen so that each performs a specific and different function based on their different characteristics. Historically, operators have started with tapered soft polymer jacketed wires when attempting antegrade wire crossing of CTOs. Recent data have shown that this wire type has a very low initial success rate. As such, most high-volume CTO programs would typically start with a stiffer polymer jacketed wire or a Gaia second wire with a rapid escalation to a tapered stiff wire. Modern wire modification strategies, also referred to as step-up/step-down techniques, start as described earlier, but then may step up to stiff, spring-coil tapered wires to overcome any hard, calcified, or fibrotic segments of the occlusion. Such a step up should then be matched by a step down to a soft, polymer/hydrophilic wire once the microcatheter is delivered into the calcified cap so that one does not exit the vessel but instead continues tracking along the occluded segment.⁷ Due to a rapidly expanding range of CTO guide wires, it is incumbent on the CTO specialist to have an organized approach to wire choice that keeps pace with evolving global experience and new guide wire designs.¹⁴