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The Role of Dissection/Re-Entry in CTO PCI
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Although dissection/re-entry techniques can significantly improve the success of chronic total occlusion PCIs, they often incite a mixture of confusion and intimidation among interventionalists.
In this column, I will attempt to clarify the dissection/re-entry terminology and techniques and discuss their strengths and limitations.
How to Do It
Dissection/re-entry involves CTO crossing through the subintimal space instead of crossing through the (occluded) true lumen. A guidewire or other device is directed (intentionally or unintentionally) into the subintimal space and advanced across the occlusion, followed by re-entry into the distal true lumen. This can be accomplished in either the antegrade or the retrograde direction (Figure 1).
Emmanouil S.
Brilakis
Antegrade dissection can be done using a “knuckle wire.” In this case, the wire — usually a polymer-jacketed guidewire, such as Fielder XT (Asahi Intecc) or Pilot 200 (Abbott Vascular) — is pushed until a loop is formed and advanced through the lesion.
Another technique for antegrade dissection is the CrossBoss catheter (BridgePoint Medical/Boston Scientific), which is a blunt microdissection catheter with a 1-mm metal tip that is rapidly rotated (fast spin technique) for advancement (Figure 2).
After subintimally crossing a CTO, re-entry into the distal true lumen is required. This step can often be quite challenging. In the early days, re-entry was accomplished by pushing a “knuckled” guidewire until it spontaneously re-entered the true lumen. This technique was first described by Antonio Colombo, MD, and given the name STAR (subintimal tracking and re-entry). In subsequent years, gifted CTO operators created techniques to make re-entry more predictable and minimize the extent of the dissection. William Lombardi, MD, and Craig Thompson, MD, described the LAST (limited antegrade subintimal tracking) technique in which either a stiff Confianza Pro 12 wire (Asahi Intecc/Abbott Vascular) or a Pilot 200 wire is used to form a 90-degree distal bent. Alfredo Galassi, MD, described the mini-STAR technique in which a Fielder XT wire was used in the same way. BridgePoint Medical created a dedicated re-entry device (Stingray) that consists of a specially designed balloon and guidewire (Figure 2). The Stingray balloon is 2.5 mm in diameter and 10 mm in length and has a flat shape with two side exit ports. After inflation at 2 atm to 4 atm, the balloon automatically orients one exit port toward the true lumen, which is accessed using the Stingray guidewire (stiff guidewire with a 20 cm distal radiopaque segment and a 0.0035-inch distal taper).
Although dissection/re-entry is mostly associated with antegrade crossing, it is also commonly used during retrograde CTO interventions. In the retrograde direction, dissection is accomplished with the same “knuckle” wire technique described above, whereas re-entry can be achieved by two techniques: the controlled antegrade and retrograde tracking and dissection (CART) and reverse CART that were discussed in more detail in the May/June 2012 CTO Corner column.
Figure 1. Overview of the chronic total occlusion dissection/re-entry strategies.
Abbreviations: CART, controlled antegrade and retrograde tracking; CTO, chronic total occlusion; LAST, limited antegrade subintimal tracking; STAR, subintimal tracking and re-entry.
Source: Emmanouil S. Brilakis, MD, PhD; reprinted with permission.
Figure 2. Panel A: Illustration of the CrossBoss Catheter, which is an over-the-wire catheter (0.014-inch guidewire compatible) with a 1-mm rounded tip, a coiled shaft and a moveable proximal torque device that releases under high torque to prevent product damage. Panel B: Illustration of the Stingray CTO re-entry system that has two components: the Stingray CTO orienting balloon catheter and the Stingray CTO re-entry guidewire. The Stingray balloon has two side exit ports (arrows) located on diametrically opposite balloon surfaces immediately proximal to two radiopaque markers (shown as yellow bands). The flat shape of the Stingray balloon automatically orients one exit port toward the vessel true lumen upon low pressure inflation (2-4 atm). The Stingray guidewire has a 0.0035-inch distal taper (shown in image insert) allowing it to re-enter the true vessel lumen through the exit port of the Stingray balloon after subintimal passage of the guidewire.
Source: BridgePoint Medical; reprinted with permission.
Why Do It
One of the main reasons dissection/re-entry is an important technique to master is that it allows for the rapid crossing of very long CTO segments safely and with high success and low complication rates. Although perforation is a feared complication, it is exceedingly rare, as the media are distensible and unlikely to be perforated by blunt objects. Employing dissection allows rapidly moving the so called “base of operations” distal to the CTO distal cap, focusing subsequent efforts in re-entering the true lumen.
In the FDA pivotal Facilitated Antegrade Steering Technique in Chronic Total Occlusions (FAST-CTOs) trial, the BridgePoint devices were effective in crossing refractory CTOs with low risk for complications. However, one should be careful to avoid advancing the device into a small side branch, as this can lead to perforation (and that is why a “knuckle” wire is often used to redirect the CrossBoss device through tortuous coronary segments).
Indications
There remains, however, much to be learned about dissection/re-entry techniques. First, there are limited long-term data. The original STAR technique was associated with high restenosis rates (up to 57%), but the rates could be lower with techniques that minimize the dissection length, such as the LAST and mini-STAR techniques. Dissection/re-entry could be associated with perforation when the knuckle wire or the CrossBoss catheter is inadvertently advanced into a small side branch. Dissection could predispose to aneurysm formation due to weakening of the media. Moreover, use of these techniques requires excellent antegrade and retrograde skills, and methodical training.
Given the lack of long-term outcomes and high restenosis with the early versions of dissection/re-entry techniques, they remain a second-line strategy, for use after antegrade and/or retrograde true lumen crossing fails; however, advanced operators currently advocate frontline use in long, complex CTOs. An additional role of dissection/re-entry is for refractory cases of “balloon uncrossable” CTOs to create a pathway of lesser resistance through the occlusion.
Dissection/re-entry is a powerful tool, but as with all powerful tools, skillful and judicious application is required. The results can be very gratifying.