Novel Japanese CTO Algorithm Prompts Potential for a More Global Strategy

A new chronic total occlusion (CTO) algorithm moves beyond anatomic and imaging features to suggest guidewire manipulation time should also be factored in as part of the current strategy.

Greater lesion complexity requires more manipulation of the guidewire to successfully cross the lesion, and the success rate decreases the longer it takes. A lengthier procedure in turn leads to longer fluoroscopic times and large contrast volumes, according to Hiroyuki Tanaka, MD (Kurashiki Central Hospital, Okayama, Japan), and colleagues. “Therefore, it is necessary to determine an appropriate CTO PCI strategy based on angiographic characteristics and guidewire manipulation time to perform a more efficient procedure and reduce the risk of complications.”

The hybrid algorithm for CTO PCI is the current preference for many US operators, although an algorithm based on EuroCTO data, as well as one released by the Asia Pacific CTO Club, have also shown promise. This new strategy, published online ahead of the November 12, 2019, issue of the Journal of the American College of Cardiology, is the first to incorporate guidewire manipulation as part of the current treatment approach.

However, experts question the need for another regionally-based algorithm for these complex lesions and instead say the focus should be on global strategy coalescence.

Commenting to TCTMD, Sanjog Kalra, MD (Einstein Medical Center, Philadelphia, PA), who was not involved in the study, said “it's a very interesting and very important attempt to try to systematize the Japanese way of doing things . . . . The issue that I have with it is that the point of an algorithm in my mind is to standardize and teach, and if you're going to standardize and teach something, you want to make whatever it is that you're going to use to define your pathways of solving a particular problem as universally appreciated as possible.”

Given that guidewire manipulation varies among operators, this “becomes less generalizable as an algorithm because not every operator has the touch, feel, understanding of the way the wires work that the Japanese operators might,” Kalra explained. “One of the beauties of the hybrid algorithm is the idea that it doesn't matter if you're really good with your hands and wires or you're not as good with your hands and wires, you can look at an angiogram and understand what is likely to work here because of the anatomic features.”

In an accompanying editorial, Stéphane Rinfret, MD (McGill University Health Centre, Montreal, Canada), and Scott A. Harding, MD (Wellington Hospital, New Zealand), write that “the proposed algorithm is a welcomed attempt from Japanese experts to better describe their thought process when approaching a CTO in an algorithmic fashion. It supports switching between strategies and introduces for the first-time ADR [antegrade dissection and reentry] as an option in cases not appropriate for retrograde. Although they acknowledged the role of ADR, we believe that its position as a bailout strategy is flawed by misunderstanding or inexperience with modern ADR procedures. Conversely, the algorithm is quite supportive of retrograde-first approaches despite minimal justification from their own data analysis.”

This algorithm will need to be tested and validated outside of Japan before it can be accepted, they add.

Focus on Guidewire Manipulation Time

For the creation of the Japanese algorithm, Tanaka and colleagues looked at 5,843 patients from the Japanese CTO-PCI registry treated between 2014 and 2017. The 26.7% who were treated with a primary retrograde compared with primary antegrade approach had a higher J-CTO score; had more right coronary artery, ostial, calcified, and tortuous CTO lesions; and were more likely to have a CTO length of at least 20 mm. The average J-CTO scores for patients treated with an antegrade approach alone, rescue retrograde approach, and primary retrograde approach were 1.6, 2.1, and 2.3, respectively (P < 0.001).

The median guidewire manipulation times associated with guidewire success and failure were 56 and 176 minutes, respectively (P < 0.001). Median guidewire manipulation time was shorter for the primary antegrade versus primary retrograde approach (39 vs 113 minutes; P < 0.001). The median successful guidewire crossing time was shorter for single wiring compared with parallel wiring in antegrade alone cases (23 vs 60 minutes) and longer for the rescue versus primary retrograde approach (126 vs 107 minutes; P < 0.001).

On multivariate analysis, reattempt, greater lesion tortuosity, CTO length ≥ 20 mm, and no stump in the proximal cap (defined as the absence of a visible entry even when using intravascular ultrasound) all independently predicted lower antegrade guidewire success in the primary antegrade approach.

Their resulting treatment algorithm was based on both angiographic characteristics as well as guidewire manipulation time. Notably, they recommend switching to a retrograde approach if guidewire manipulation time exceeds 20 minutes in the primary antegrade approach. The authors also suggest stopping treatment altogether once guidewire manipulation time exceeds 3 hours.

“In patients undergoing percutaneous revascularization of CTOs, low lesion complexity and chronically occluded stents favor a primary antegrade approach,” Tanaka and colleagues conclude. “A retrograde approach can be most useful when guidewire manipulation time exceeds 20 min, when there is no arterial stump, and for second attempts. Special considerations apply to parallel wiring, antegrade dissection with reentry, and IVUS-guided procedures, but cessation of attempts should be strongly considered when guidewire manipulation time extends for 3 hours.”

Fundamental Differences

Something that “stuck out like a sore thumb” in this analysis, according to Kalra, was the low 7.3% rate of post-CABG lesions included, especially considering this rate was 37% in the OPEN-CTO registry. “Post-CABG lesions are longer, they are more calcified, they are supplied by atypical collaterals, the proximal cap is tougher to penetrate, they tend to be blunt, [and] there is more retrograde use in those types of cases,” he explained.

“The features of the Japanese cohort are different than the features of the US cohort,” Kalra added. “That may limit the generalizability of an algorithm that uses guidewire manipulation time either in the antegrade or retrograde setting to be able to define strategy switching.”

Rinfret and Harding highlight some further differences between Japanese and non-Japanese operators.

“Although Japanese operators have developed advanced skills with dedicated guidewires for crossing tortuous epicardial vessels and will usually have a lower threshold in using them for a retrograde approach, hybrid operators are advised to exhaust antegrade, retrograde through septal channel or graft pathways, or intravascular ultrasound-guided options before selecting a higher-risk collateral,” they write. “Also, hybrid operators will not be discouraged to attempt crossing septal channels even if no large connection can be isolated, collaterals often considered ‘noninterventional’ for Japanese operators.”

Further, the editorialists explain that “antegrade crossing has generally been preferred over retrograde as the initial crossing strategy, given the higher risk of complications with the retrograde approach. The complication rates in this registry were remarkably low. Although this was likely due to the expertise of the operators, it may also be attributable to treatment of a lower-risk population, with < 10% with previous coronary artery bypass grafting. Even so, a retrograde-first approach was associated with double the rate of major adverse events compared with a primary antegrade.”

Given the recent publication of a best practices document on CTO PCI, Rinfret and Harding write that “the multiplication of algorithms for CTO PCI may lead to confusion rather than clarity. Maybe it’s time for a globally agreed CTO-PCI algorithm.”

“What a laudable, lovely, and optimal utopia that would be,” Kalra replied. “That's an optimal goal for all of us to shoot towards, but I think the most important piece of that statement is ‘global,’ in that as global operators we need to work together and learn from one another to solve common anatomical  problems. I think a global algorithm will be difficult to put together because patient populations in the major areas of the world are fundamentally different.”

That said, strategies can be shared globally and applied to various populations. “Ultimately, what it comes down to is a global initiative to coalesce strategies as opposed to a global initiative to coalesce algorithms,” Kalra concluded. “Algorithms are based on what patients need, but strategies are tools in a toolbox that can be used in the right circumstance.”