What are the current challenges of chronic total occlusion (CTO) procedures?
First, while experienced centers perform CTO procedures with high success rates, many or most centers actually don’t have the required expertise, and thus have significantly lower success rates. Experienced, high-volume centers have success rates up to 85% to 90%, whereas success in less experienced centers is much lower, around 60%.
Second, complications still occur in approximately 2.5% to 3% of cases. Although we have made significant improvements in success, the complication rates have not decreased.
Third, efficiency and cost-effectiveness can be further improved. CTO interventions can be taxing for the operator, the cath lab team, the patient, and the hospital, as they often require a lot of time and equipment.
What are the primary complications seen in CTO procedures?
There are some unique complications for CTO procedures, such as donor vessel injury, that can be life-threatening. The most common complications of CTO procedures are perforations, which occur more often than with non-CTO procedures.
How are you focusing on preprocedural planning to help with CTO cases?
Preprocedural planning is key for the success and safety of the procedure. We spend at least 15-30 minutes reviewing the angiogram and writing down a procedural plan outlining equipment and strategy (such as antegrade, antegrade dissection/re-entry, and retrograde). There are several angiographic scores that can be used to facilitate and standardize the way we evaluate the angiograms, such as the Japan CTO (J-CTO) and the PROGRESS-CTO scores.
Do you typically get a computed tomography (CT) scan for CTO patients prior to the intervention?
CT angiography (CTA) has been a relatively new and highly promising aspect of CTO PCI planning that we have been increasingly incorporating in our practice. Many patients have CTAs instead of diagnostic angiograms as the initial diagnostic test to help detect coronary artery disease. We often obtain a CTA in patients with CTOs, especially complex CTOs, or CTOs in patients with previous coronary bypass graft surgery. CTA can help clarify proximal (and distal) cap ambiguity, understand the occlusion length, and understand the composition (such as calcification) and course of the occlusion.
An additional benefit of CTA is live procedural guidance through the co-registration of the CTA with the angiogram. Co-registration helps to guide wiring towards the distal true lumen, avoid side branches, and choose the most suitable reentry zone. The program we use is called syngo CTO Guidance (Siemens Healthineers), which essentially takes the CTA and fuses it with the live angiographic images. It offers us a live roadmap during the procedure. syngo CTO Guidance helps by creating center lines of the vessels, and it can clarify if a vessel is foreshortened or not in each view. We are able to see live whether the guidewire is following the track of the vessel or if it is going into a different location. The fusion process is fairly simple in most cases and doesn’t require a lot of expertise to create. Usually it is our fellows who perform this process or sometimes it is the CT tech. The co-registration software performs automated segmentation that is accurate in most cases.
Does syngo CTO Guidance help you to plan a case?
Yes, syngo CTO Guidance is excellent for planning. For example, we had a case of a complex patient with saphenous vein graft failure that couldn’t be recanalized, because it was severely diseased. We were not sure about the location of the native vessel on the angiogram. We actually stopped the procedure, sent the patient for an emergent CT scan that same morning, and then brought him back later in the day to do the procedure. The CT clarified the location of the CTO vessel proximal cap, and made crossing much safer and easier.
CTA gives us greater confidence in determining the potential course of the occlusion and allows us to advance guidewires in the right direction. Co-registration helps us see, live, if the wire is moving in the intended course, reducing the need for contralateral contrast injections. Live co-registration permits us to visualize the center lines of the vessel and more easily understand where we are actually going. Thus, we can reduce the risk for perforations and other complications.
Does use of syngo CTO Guidance shorten procedure time?
Yes, especially in complex cases. It makes CTO procedures safer and sometimes faster as well. It can convert a failed case to a successful case. For example, we had a case that was attempted twice without success at a different institution, due to proximal cap ambiguity. Using CTA clarified the course of the vessel and using an angled microcatheter, we were able to direct the wire appropriately and successfully across the occlusion.
Should all CTO cases undergo a CT? It sounds like some patients don’t necessarily need it.
In easy, straightforward cases (such as those with a J-CTO score of 0 or 1), in which the course of the vessel is clear and the occlusion appears soft and not calcified, without ambiguity in the proximal cap, success rates are high without syngo CTO Guidance. In more complex cases, however, syngo CTO Guidance can play an important role, helping answer questions about occlusion length, calcification, distorted anatomy, and/or proximal cap ambiguity.
Are you finding that you are seeing more complex cases?
Absolutely, both in terms of CTOs and non-CTOs. We rarely see simple lesions anymore. We often see previously failed cases or cases that are not attempted elsewhere due to high complexity.
Can the use of syngo CTO Guidance lower radiation exposure?
Absolutely. Complex CTOs often require long procedure times, that could be shortened with syngo CTO Guidance, reducing patient and operator radiation dose.
How does co-registration affect image quality?
The quality of the imaging is the same with and without co-registration. You still see the regular x-ray, because co-registration does not affect the images you generate from the x-ray, but overlays the course of the artery on the fluoroscopic image. You can always turn co-registration on and off throughout the case.
How do you see this technology affecting procedures in the future?
syngo CTO Guidance could be helpful in multiple ways. First, for preprocedural planning. It offers much better planning and we can better choose the strategies that are more likely to be successful. In a recent study, J-CTO score based on CT angiography was much more accurate than the angiographic J-CTO score in predicting the success of the procedure and the likelihood of wire crossing within 30 minutes. Using syngo CTO Guidance, we can select equipment more wisely and better set up the case. Moreover, it can make the procedure more efficient and successful, and reduce the risk for complications. syngo CTO Guidance can help approach some very complex CTOs.
When you first started reviewing CTs, how would you describe the learning curve?
Like everything else in CTO PCI, there is definitely a learning curve. I am still learning myself. For all my cases where I have a CTA, I review the film with a CT expert. This collaborative approach helps me better understand the anatomy and plan the crossing approach.
Are there any CTO studies you would like to highlight?
The EUROCTO study was published in 2018, showing better symptom relief with CTO PCI as compared with medical therapy at 12 months after the procedure.1 We are currently performing a sham-controlled study of CTO PCI vs no CTO PCI, similar to the ORBITA trial, named SHINE-CTO, that we believe will be critical to accurate determine the symptomatic benefits of CTO PCI. We are also planning a randomized study to evaluate a novel approach to saphenous vein graft failure, in which where patients will be randomized to either PCI of the saphenous vein graft lesions or PCI of the native coronary artery CTO. It may be that by treating the native CTO, we get better long-term outcomes than with the vein graft intervention. There are two ongoing Scandinavian trials called ISCHEMIA CTO and NOBLE CTO, looking at the impact of CTO PCI on hard outcomes. These trials will, however, not be completed for nearly a decade, due to large number of patients needed.
There are several new CTO devices currently under development. We are excited about the SoundBite device that can facilitate crossing through severe calcification, as well as studies with other devices, such as the ReCross (IMDS [Interventional Medical Device Solutions]), a dual lumen device that may facilitate reentry into the distal true lumen, similar to the Stingray balloon (Boston Scientific). Finally, through the PROGRESS CTO registry, we are collaborating with several operators and institutions around the world, sharing new techniques and best practices.
Any final thoughts?
CT angiography is being used more and more, and the radiation dose from CTA is decreasing. I believe we will see increased use of CTA in daily cardiology practice, which will make more people comfortable looking at CTAs, and as a result, they will also be more comfortable looking at CTAs specifically for planning CTO PCI and other complex procedures. Use of scores based on CT angiography, such as the CT-RECTOR score2, will expand and facilitate our approach to CTO lesions.
Disclosure: Dr. Emmanouil Brilakis reports consulting/speaker honoraria from Abbott Vascular, the American Heart Association (associate editor, Circulation), Boston Scientific, Cardiovascular Innovations Foundation (board of directors), CSI, Elsevier, GE Healthcare, Infraredx, and Medtronic; research support from Regeneron and Siemens. Shareholder: MHI Ventures. Board of Trustees: Society of Cardiovascular Angiography and Interventions (SCAI).
Dr. Brilakis can be contacted at firstname.lastname@example.org.
- Werner GS, Martin-Yuste V, Hildick-Smith D, et al; EUROCTO trial investigators. A randomized multicentre trial to compare revascularization with optimal medical therapy for the treatment of chronic total coronary occlusions. Eur Heart J. 2018 Jul 7;39(26):2484-2493.
- Fujino A, Otsuji S, Hasegawa K, et al. Accuracy of J-CTO score derived from computed tomography versus angiography to predict successful percutaneous coronary intervention. JACC Cardiovasc Imaging. 2018 Feb;11(2 Pt 1):209-217.