Abstract
Dissection/reentry can be achieved either in the antegrade or the retrograde direction. Antegrade dissection can be achieved using knuckled guidewires or using the CrossBoss catheter. Antegrade reentry can be achieved using guidewires or using the Stingray balloon and guidewire. Antegrade dissection/reentry can be divided into four steps. First, a decision is made to attempt antegrade dissection/reentry as a primary strategy or after failure of other crossing techniques. Second, a microcatheter (or an over-the-wire balloon or CrossBoss catheter) is advanced to the chronic total occlusion (CTO). Third, a knuckle guidewire or the CrossBoss catheter is used to subintimally cross the CTO. Fourth, reentry into the distal true lumen is achieved using guidewires or the Stingray system. Minimization of the subintimal dissection length and size is desired, as long subintimal crossing length can lead to side branch occlusion, long stented segments, and subsequent higher in-stent restenosis rates.
Keywords
Chronic total occlusion, CrossBoss, Devices, Dissection, Guidewires, Procedural success, Reentry, Stingray, Subintimal space, Technique
Antegrade dissection/reentry is a safe and efficient strategy for crossing long chronic total occlusions (CTOs), as outlined in the hybrid CTO crossing algorithm ( Chapter 7 ). Antegrade dissection takes advantage of the distensibility of the subintimal space for traversing the occlusion rapidly and safely, concentrating subsequent efforts in crossing back into the distal true lumen (reentry). In the past, distal true lumen reentry was problematic because satisfactory tools and techniques were lacking, but dedicated equipment (Stingray balloon and guidewire, Boston Scientific) has significantly facilitated reentry.
5.1
Clarifying the Terminology
The terminology utilized in dissection/reentry CTO strategies can be confusing. CTO crossing can occur either in the antegrade or the retrograde direction. In either direction, crossing can be achieved either from true-to-true lumen or by first entering the subintimal space, followed by reentry into the true lumen (dissection/reentry strategies) ( Figs. 5.1 and 5.2 ).
The term subintimal may increase this confusion, as there is typically no intimal layer within the atheroma of a totally occluded artery. Rather, subintimal in CTO percutaneous coronary intervention (PCI) has evolved as a general term that refers to a tissue plane within or beyond the occlusion that may be (1) subintimal, (2) intraplaque, (3) intraadventitial, or (4) combinations thereof, where the location of a tissue plane is related to disease morphology and position along the length of the artery.
Extensive dissection/reentry (subintimal tracking and reentry (STAR) technique), requires stenting of long coronary segments, often sacrifices side branches, and has been associated with poor long-term outcomes with high rates of in-stent restenosis. The goal is always to achieve recanalization with a limited dissection/reentry (using wire-based strategies or dedicated reentry systems, such as the Stingray reentry system Figure 5.2 ), allowing targeted reentry, side branch preservation, and shorter stent lengths.
In the antegrade approach, dissection can be achieved by:
- 1.
Wire-based strategy (i.e., inadvertent wiring or knuckle wire) . A knuckle (prolapsed guidewire) is formed by pushing a polymer-jacketed guidewire, (usually Fielder XT or Pilot 50 or 200) until it forms a tight loop at its tip ( Fig. 5.3 ). The knuckle is then advanced subintimally through the occlusion. Compared to trying to advance the tip of a wire, advancing a knuckle is much faster, safer (the tight loop minimizes the risk of vessel perforation), and less likely to enter side branches.
Figure 5.3
Illustration of knuckle wires. It is important to limit the diameter of the knuckle, as large knuckles enlarge the subintimal space and hinder reentry.
- 2.
Catheter-based strategy, using the CrossBoss catheter .
In the antegrade approach, reentry can be achieved by:
- 1.
Wire-based strategies (not recommended) .
- a.
Continuing to advance the knuckled guidewire until it spontaneously reenters the true lumen (usually at a distal bifurcation). This is the STAR technique that was invented by Antonio Colombo. A modification of the STAR technique called the contrast-guided STAR or Carlino technique, named after its inventor, uses subintimal contrast injection through a microcatheter inserted into the proximal cap to create/visualize a dissection plane and facilitate guidewire advancement ( Fig. 5.4 ). However, the STAR technique (1) often results in side branch loss, (2) is less predictably successful, and (3) has high reocclusion rates (likely due to long stent length and limited vessel outflow). It is rarely used as a definitive technique, but may be employed as a last-ditch effort, especially in the right coronary artery.
Figure 5.4
Contrast-guided subintimal tracking and reentry.
Chronic total occlusion of the proximal right coronary artery ( arrow , A), treated with injection of contrast via a microcatheter resulting in subintimal contrast entry ( arrows , B) into the distal true lumen, with successful recanalization after stenting (C).
Reproduced with permission from Michael TT, Papayannis AC, Banerjee S, Brilakis ES. Subintimal dissection/reentry strategies in coronary chronic total occlusion interventions. Circ Cardiovasc Interv 2012; 5 :729–38.
- b.
Reentering the true lumen as early as possible after the occlusion with a guidewire distal to the occlusion, which can be achieved by the mini-STAR or the limited antegrade subintimal tracking ( LAST ) technique (described in detail in Section 5.4, Step 4.2 ). These techniques, however, tend to have lower success rates because of difficulty in reliably reentering the true lumen, often due to extensive uncontrolled dissection with subintimal hematoma formation and true lumen compression.
- a.
- 2.
Dedicated reentry systems (recommended) .
- a.
Using the Stingray (Boston Scientific) balloon and guidewire.
- a.
In the retrograde approach , dissection is usually performed using a knuckle wire and reentry is achieved using the techniques described in Chapter 6 , Step 7.2.
5.2
When Should Antegrade Dissection/Reentry Be Used?
Antegrade dissection/reentry can be used ( Fig. 5.5 ):
- 1.
After failure of antegrade wire escalation (inadvertent subintimal wire crossing) or failure of the retrograde approach.
- 2.
As the initial crossing strategy (primary dissection/reentry).
Good candidate lesions for primary dissection/reentry strategy are those with:
- 1.
Well-defined proximal cap.
- 2.
Large-caliber distal vessel.
- 3.
No large branches within the CTO or more importantly at the distal cap.
- 4.
Lack of good interventional collaterals.
- 5.
≥20 mm length.
5.2.1
The Antegrade Dissection/Reentry Debate
The optimal role and timing of antegrade dissection/reentry in CTO PCI has been a subject of debate. Hybrid operators ( Chapter 7 ) favor early application of antegrade dissection/reentry to increase success rates and improve efficiency of the procedure, while keeping the risk low. Other operators argue that dissection/reentry should only be used as a last resort after other crossing strategies fail.
Several studies have shown that more complex lesions are more likely to require use of advanced crossing techniques (i.e., antegrade dissection/reentry and the retrograde approach; Fig. 6.44 ). However, antegrade dissection/reentry carries lower risk than the retrograde approach, hence for many operators it is the preferred initial advanced crossing technique in challenging cases.
Moreover, several studies have shown similar restenosis rates with antegrade dissection/reentry and antegrade wiring. Antegrade dissection reentry can also provide unique solutions to anatomic challenges, such as proximal cap ambiguity (move-the-cap techniques, such as balloon-assisted subintimal entry and scratch-and-go”, Section 9.1 ), wire uncrossable lesions (Carlino technique, Section 9.2 ), balloon uncrossable lesions (subintimal lesion modification or subintimal distal anchor, Section 8.1 ), and crossing of in-stent restenosis (using the CrossBoss catheter, Section 9.7 , Online Case 19 ). However, the cost of antegrade dissection/reentry equipment can be high, limiting adoption in some areas.
If technically and economically feasible and among operators with experience in the techniques, limited antegrade dissection/reentry (i.e., use of the Stingray system for reentry close to the distal cap) should be the preferred advanced crossing technique for complex lesions. In contrast, extensive dissection/reentry techniques (such as STAR; see Section 5.6.1 ) have been associated with high restenosis and reocclusion rates and should be rarely used, except potentially as a final bail-out maneuver.
5.3
How to Use the CrossBoss Catheter
The CrossBoss catheter is used according to the following four steps ( Fig. 5.6 ).
Unless the CTO proximal cap is ostial or very proximal, it should be accessed with a workhorse guidewire advanced through a microcatheter, over-the-wire balloon, or the CrossBoss catheter itself, as described in Step 4.2 .
The CrossBoss catheter is then advanced into the proximal cap and the guidewire is retracted within the CrossBoss catheter (but not removed, as it may help prevent blood entry and thrombus formation within the CrossBoss catheter lumen) ( Fig. 5.7 ).
The CrossBoss catheter torquer is positioned 2–3 cm (two to three finger widths) proximal to the Y-connector and tightened.
This is done to limit potentially excessive forward movement of the CrossBoss catheter (so-called CrossBoss jump) during catheter spinning. As the CrossBoss catheter engages and penetrates tissue, at times the device stores torsional energy and has the propensity to jump during advancement and navigation.
The CrossBoss catheter is rotated using the fast-spin technique and gentle forward pressure.
The Y-connector is held between the small finger and the palm of the left hand and the torque device is rotated using the index finger and thumb of both hands.
The catheter can be spun by hand in either direction, rotating as fast as possible (until crossing or significant operator discomfort!) . Faster spinning decreases friction and increases the likelihood of advancement and crossing. During catheter advancement it is important to keep the CrossBoss torquer device close (two finger-breadths) to the hemostatic valve, to prevent excessive forward movement of the CrossBoss.
The result of the fast-spin technique is assessed using contralateral injection (antegrade injections should not be performed after antegrade dissection/reentry is started to minimize the risk of extending a proximal dissection) and orthogonal views (to detect possible entry of the CrossBoss catheter into a side branch). There are five possible outcomes of the fast-spin technique.
4.1. CrossBoss Fails to Advance ( Fig. 5.11 )
Failure of the CrossBoss to advance can be due to poor guide catheter support or a hard, calcified proximal cap. Potential solutions include:
- 1.
Increase guide catheter support (for example by using a more supportive guide catheter, a side-branch anchor technique, or a guide catheter extension as described in detail in Chapter 3, Section 3.6 ).
- 2.
In patients with hard, calcified proximal cap a stiff guidewire, such as the Confianza Pro 12, Hornet 14, or Astato 20 can be used to puncture the proximal cap (should not be advanced >5–10 mm to prevent vessel perforation). This wire should be immediately withdrawn and the CrossBoss advanced by itself, using the fast-spin technique. Alternatively, a polymer-jacketed wire can be used to create a knuckle and subsequently advanced, followed by CrossBoss crossing of the final CTO segment.
- 3.
Change to a guidewire crossing strategy.
4.2. CrossBoss Enters a Side Branch ( Fig. 5.12 )
Although the CrossBoss catheter is highly unlikely to exit the vessel adventitia, due to its blunt trip, it can enter side branches. If undetected, entry of the CrossBoss into a side branch can be a catastrophic complication, as continued advancement can make it exit the side branch, causing a large and often challenging-to-treat perforation.
Detection : Side-branch course of the CrossBoss catheter is detected by using imaging in various projections and contralateral injection. Side-branch course is suspected when the CrossBoss catheter is not dancing in sync with the CTO target vessel.
Management : The CrossBoss catheter is retracted and redirected, usually using a knuckled polymer-jacketed guidewire or less commonly a stiff guidewire (such as the Gaia 2nd or Confianza Pro 12), which are less likely to enter the side branches.
4.3. CrossBoss Partially Crosses the Occlusion ( Fig. 5.13 )
Partial CrossBoss crossing can be due to intraocclusion calcification and/or tortuosity or due to interaction with a previously deployed stent.
Management : The CrossBoss catheter is retracted and redirected, usually using a knuckled polymer-jacketed guidewire or less commonly a stiff guidewire (such as the Gaia 2nd or Confianza Pro 12).
4.4. CrossBoss Crosses Into Subintimal Space Distal to the Distal Cap ( Fig. 5.14 )
- •
Crossing of the CrossBoss catheter in the subintimal space distal to the distal cap creates favorable conditions for reentry, as it has a low profile and hence does not enlarge the subintimal space .
Figure 5.14
CrossBoss crosses into subintimal space distal to the distal cap.
- •
Reentry is optimally performed using the Stingray balloon (see Section 5.5 ) without reentry attempts with guidewires, as the latter may enlarge the area of dissection and cause large subintimal hematomas, which in turn can compress the distal true lumen, and hinder reentry attempts.
- •
The CrossBoss should be removed over a stiff, straight, nonlubricious guide wire, such as a Miracle 12, using the trapping technique to prevent wire movement and maintain distal position without enlarging the dissection.
- •
After subintimal crossing with the CrossBoss it is useful to disconnect the contrast-containing syringe from the antegrade guide catheter manifold (or cover the manifold) to minimize the risk of hydraulic dissection ( Fig. 5.15 ). Inadvertent contrast injection could enlarge the subintimal space and hinder reentry attempts.
Figure 5.15
Example of disconnecting the injection syringe from the manifold (panel B; panel A shows the connected manifold) after antegrade subintimal crossing to prevent inadvertent contrast injection that could enlarge the subintimal space.
4.5. CrossBoss Crosses Into Distal True Lumen ( Fig. 5.16 )
The CrossBoss catheter may cross into the distal true lumen in approximately one-third of cases ( Fig. 5.17 ). A workhorse guidewire is then inserted into the distal true lumen and the CrossBoss catheter is removed (ideally using the trapping technique to minimize the risk of losing guidewire position), followed by standard balloon angioplasty and stenting.
5.4
How to Use a Knuckle Wire for Crossing
Step-by-Step Knuckle Wire Crossing ( Fig. 5.18 )
The most common scenario for using a knuckled guidewire is when the antegrade (or retrograde) guidewire enters into the subintimal space. Alternative strategies to knuckled guidewire are (1) redirecting the initial guidewire into the true lumen, (2) using a parallel wire technique ( Chapter 4 , Step 7b), or (3) retrograde guidewire crossing ( Chapter 6 ).
Subintimal Crossing: Knuckle Wire Versus CrossBoss
Two techniques can be used for subintimal CTO crossing: (1) wire-based (knuckle wire technique) and (2) catheter-based (CrossBoss device).
The advantages of the CrossBoss catheter over a knuckle wire are the following:
- 1.
It creates a smaller and more controlled subintimal dissection space ( Fig. 5.20 ), enabling a more predictable and controlled reentry into the distal true lumen.
Figure 5.20
Comparison dissection created using a knuckled guidewire (larger size) and created with a CrossBoss catheter (smaller size).
Courtesy of Dr. Craig Thompson.
- 2.
The relatively stiff CrossBoss catheter tends to advance along a longitudinal path parallel to the artery axis, whereas guidewires sometimes wrap around the artery circumference (in a barber-pole fashion; Fig. 5.21 ), potentially hindering subsequent advancement of other devices and reentry into the distal true lumen.
