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Breaking Barriers in Complex Coronary CTO Interventions: Mastering Uncrossable Lesions
Ayman Helal, MD Cardiology
Interventional cardiologist, Kettering General Hospital
Abstract
Coronary chronic total occlusions (CTOs) represent one of the most challenging lesions to treat in percutaneous coronary intervention (PCI). Uncrossable lesions, which cannot be traversed by standard guidewires, balloons, or microcatheters, are a significant subset of these CTOs, accounting for up to 9% of cases. These lesions are often calcified and tortuous, resulting in longer procedural times, increased radiation exposure, and a higher likelihood of failure. The management of uncrossable lesions follows a systematic approach, beginning with first-line strategies such as enhanced guide catheter support and microcatheter use, and progressing to second-line plaque modification techniques like rotational and orbital atherectomy. Third-line strategies, such as dissection re-entry, are used as a last resort. This article presents an in-depth analysis of various techniques and tools available for managing uncrossable CTO lesions.
Introduction
Chronic total occlusions (CTOs) are coronary artery lesions with 100% occlusion for a duration of over three months. They pose a significant challenge during percutaneous coronary intervention (PCI), particularly when encountering “uncrossable lesions,” where even advanced tools like guidewires, balloons, and microcatheters fail to pass through the occlusion. Uncrossable CTOs are associated with a higher procedural difficulty and lower success rates, often requiring advanced techniques and tools. This article discusses the stepwise approach to managing uncrossable CTO lesions, focusing on both conventional and novel strategies.[1]
Understanding Uncrossable Lesions in CTO
Uncrossable lesions are those that cannot be crossed with a balloon after successful guidewire crossing, often due to heavy calcification, tortuosity, or a combination of both. These lesions are more common in older patients and those with complex cardiovascular anatomy. Uncrossable lesions present procedural challenges and are linked to increased rates of procedural failure, longer fluoroscopy times, and higher contrast volumes.[1]
Strategies for Managing Uncrossable CTO Lesions
First-Line Strategies
Figure 1: GuideLiner catheter. (A) and (B) show that wire crossing and Guideliner catheter introducing was achieved in the mid RCA (C) [4]
4. Wire-Based Support Techniques: Operators usually starts with with low-penetration wires like the SION or Fielder wires, then escalates the wires to high-penetration or stiffer wires such as the Gaia wires if the softer wires fail to cross. Supportive wires, such as the Wiggle wire (with several bends proximal to the tip, helps redirect pushing forces to navigate the balloon or stent through resistant lesions), extra-supportive wires (like the Confianza Pro) help cross resistant lesions. Techniques like the buddy wire (technique involves a second wire to enhance support, straighten tortuous bends, and reduce wire bias) or wire cutting can also improve success in crossing uncrossable lesions. In the wire-cutting technique (Figure 2 A), a second guidewire is advanced through the occlusion while a balloon is positioned and inflated over the first guidewire. The second guidewire is then withdrawn with the balloon still inflated, cutting and modifying the proximal cap. After deflation and removal, a new balloon is advanced, often successfully crossing the altered lesion. A modified version, the see-saw wire-cutting technique (Figure 2 B, involves inflating two balloons over two guidewires alternately to modify the lesion on both sides. This technique has been shown to improve success rates and reduce procedure time compared to the Tornus catheter in a study of 80 patients. [5]
Figure 2: wire-cutting and (b) the see-saw wire-cutting techniques [5]
5. Anchoring Techniques: Anchor balloons provide additional stability. In the side branch anchor technique (Figure 3, left panel), a guidewire is advanced into a side branch, such as the conus or acute marginal branch for the right coronary artery, or the diagonal branch for the left anterior descending artery. A small balloon, typically 1.5–2.0 mm in diameter depending on the size of the side branch, is then inflated at 6–8 atm. This anchors the guide into the vessel, facilitating the advancement of balloons or microcatheters. Occasionally, patients may experience chest pain during balloon inflation in the side branch. To enhance support further, guide extension anchoring technique (Figure 3, right panel) can be used but this requires a second guide catheter will be needed to advance a balloon beside the guide extension, the balloon is then inflated against the to trap guide extension which subsequently increases the support and enhances equipment delivery.[5]
Figure 3: Side branch anchoring (left panel) and guide extension anchoring (right panel) techniques for facilitating delivery of a balloon across lesion technique [5]
6. Microcatheters: Microcatheters, such as the Tornus or Turnpike Spiral, help facilitate lesion crossing by improving pushability and allowing for wire exchanges. The Tornus, for example, has a metal coil design for increased torque transmission, while the Turnpike Spiral’s rotational assistance helps navigate resistant lesions (Figure 4).[6]
Figure 4: Turnpike microcatheter family, Turnpike, Turnpike Spiral, Turnpike Gold with the composition of the shaft and the different tips.[6]
Second-Line Strategies
Balloon-Assisted Microdissection (BAM): Balloon-assisted microdissection involves the use of a low-profile balloon advanced and inflated at high pressure at the beginning of the lesion to create microdissections within the proximal cap, facilitating subsequent passage of the balloon or stent. This technique can be effective but carries a risk of perforation. This technique is illustrated in Figure 5.[3]
Figure 5: Balloon-Assisted Microdissection (BAM). Following wire crossing (A), a small low-profile compliant balloon is advanced to the proximal cap and inflated (B) to create microdissections (B,C), then balloon crossing (D) and inflation (E) to facilitate further interventions. [3]
Excimer Laser Coronary Atherectomy (ELCA): Excimer Laser Coronary Atherectomy (ELCA) uses monochromatic ultraviolet light to ablate calcified tissue via photochemical, photothermal and photokinetic mechanisms (Figure 6). The primary mechanism affecting calcification is photoacoustic energy, which fractures calcium and prepares the lesion This technique is particularly useful for modifying heavily calcified lesions, allowing subsequent balloon or stent expansion. The pulsed ultraviolet light emitted at a wavelength of 308 nm has a shallow penetration depth, minimizing the risk of dissection and vessel perforation. For non-crossable and non-expansile lesions, the highly deliverable 0.9 mm X-80 catheter is preferred, with a maximum fluence of 80 mJ/mm² and a repetition rate of 80 Hz. Each activation lasts for 10 seconds, followed by a mandatory five-second rest period, and this cycle is repeated until the catheter crosses the lesion or sufficient lesion modification allows for balloon crossing or expansion. Though effective, laser use with contrast carries a risk of perforation.[7]
Figure 6: Advanced calcium modification devices and its effect. (A) RotaPro® rotational atherectomy system allows front-cutting (arrows in A’). (B) The diamond-coated crown of Diamondback 360® orbital atherectomy system sands calcified plaque in the radial direction (arrows in B′). (C) ELCA catheters emit ultraviolet energy forward (arrows in C′) . (D) Shockwave C2® system creates pulsatile sonic pressure waves along the length of the device (arrows in D′). [7]
Rotational Atherectomy (RA): Rotational atherectomy (Figure 6) is often the next step when other techniques fail; however this will need a wire exchange to ROTAWIRE over microcatheter which may be technically difficult in the context of an uncrossable lesion. The diamond-coated rotating burr used in RA selectively ablates calcified plaque and inelastic portions of the plaque into micro-particles, while sparing the more elastic vessel walls allowing for successful balloon and stent placement. RA is particularly effective in dealing with heavily calcified lesions that are otherwise resistant to balloon inflation.[8]
Orbital Atherectomy (OA): Orbital atherectomy (Figure 6), using the DiamondBack 360 system, creates a “sandblasting” effect that pulverizes the calcified tissue into microparticles, which are then absorbed by the bloodstream. OA has shown success even when used after rotational atherectomy and other methods have failed. The ability to expand the role of orbital atherectomy in treating fibrotic or highly resistant occlusions represents a new frontier in CTO PCI. There are only limited case reports where orbital atherectomy was used from the outset in managing a CTO. [9]
Third-Line Strategies: Dissection Reentry (Subintimal Approach)
In extreme cases where all other methods fail, operators may resort to the subintimal dissection re-entry technique. This involves creating a dissection plane around the occlusion and re-entering the true lumen on the distal side of the lesion (Figure 7). This can be performed either through antegrade or retrograde approach. While highly effective, this method is technically demanding and should only be performed by experienced operators.[10]
Figure 7: Antegrade dissection re-entry (ADR) technique [10]
Conclusion
Uncrossable CTO lesions present a formidable challenge in PCI, often requiring a stepwise approach that incorporates both conventional and novel techniques. First-line strategies focus on optimizing catheter and wire support, while second-line techniques involve advanced plaque modification methods like rotational and orbital atherectomy. In cases where these methods fail, the subintimal approach serves as a last resort. The evolution of techniques and tools has expanded the therapeutic options available for treating uncrossable CTO lesions, improving outcomes for this challenging subset of patients.
References