Abstract
Antegrade wire escalation is the most easily understood and most widely used chronic total occlusion (CTO) crossing technique and is most appropriate for short occlusions or longer occlusions where a through-and-through microchannel is suspected. Antegrade wire escalation can be divided into seven steps. First, a microcatheter (preferred) or over-the-wire balloon is selected. Second, the microcatheter is advanced to the CTO. Third, a guidewire is selected. Fourth, the guidewire tip is shaped. Fifth, the guidewire is advanced using sliding, drilling, penetration, or a combination of these techniques. Sixth, the wire position is assessed to determine further action. Seventh, if the wire crosses into the distal, true lumen balloon angioplasty and stenting are performed per standard fashion; if the wire enters the subintimal space it is redirected into the distal true lumen using a variety of techniques; if the wire exits the vessel architecture, it is withdrawn and crossing attempts are restarted.
Keywords
Antegrade, Bifurcation, Chronic total occlusion, Guidewire, In-stent restenosis, Intravascular ultrasonography, Microcatheter, Technique
Antegrade wire escalation is the simplest and most widely used chronic total occlusion (CTO) crossing technique. At least 50% of CTO interventions are currently successfully recanalized using antegrade wire escalation. Familiarity and confidence with this technique provides the foundation upon which all other CTO percutaneous coronary intervention (PCI) techniques (antegrade dissection/reentry and retrograde) are built. Wire escalation may be most helpful in short occlusions (i.e., <20 mm length), longer occlusions of straight segments and/or where a through-and-through microchannel is suspected, and in selected cases of occlusive in-stent restenosis.
Goal
Select the equipment most likely to assist with CTO crossing.
How?
A microcatheter or over-the-wire balloon should be used for antegrade crossing in all CTOs (i.e., CTO crossing should not be attempted with unsupported guidewires) because such a system:
- a.
Enhances the wire penetrating capacity ( Figure 2.17 ).
- b.
Allows wire tip reshaping without losing wire position.
- c.
Facilitates wire exchanges.
- d.
Prevents twisting of wires when using the parallel wire technique.
A microcatheter is preferred by most operators (as described in Chapter 2 , Section 2.4 ), because it:
- a.
Allows accurate assessment of the microcatheter tip location (because the marker is located at the tip, whereas in 1.20–1.50 mm balloons the marker is located in midshaft and the tip is not angiographically visible).
- b.
Is more resistant to kinking.
These advantages are particularly important in cases of tortuosity or poor guide catheter support , because over-the-wire balloons:
- a.
Are prone to kinking upon wire removal, thus hindering reliable wire exchanges.
- b.
Provide less support due to lack of wire braiding.
- c.
Are more likely to cause proximal vessel injury.
Goal
Deliver a guidewire and microcatheter/over-the-wire balloon to the proximal CTO cap.
How?
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 .
CTO wires with high penetrating power and tapered tips should not be used to traverse the proximal vessel to get to the CTO proximal cap because:
- a.
They can cause vessel injury, especially in diffusely diseased vessels ( Fig. 4.1 ).
- b.
The wire bend required to reach the CTO is usually different (much larger) than the wire bend used when entering and crossing the CTO (much smaller) ( Fig. 4.2 ).
A soft-tipped, workhorse guidewire should be used to reach the CTO proximal cap, followed by the microcatheter or over-the-wire balloon ( Fig. 4.3 ). The guidewire is then switched for the CTO crossing guidewire through the microcatheter or over-the-wire balloon ( Fig. 4.4 ).
After removing the workhorse guidewire, contrast injection through the microcatheter can sometimes be very useful for clarifying the location and characteristics of the proximal cap.
Goal
Select the most appropriate guidewire for initial antegrade CTO crossing.
How?
Although several coronary guidewires are available for CTO crossing, a simplified selection and escalation scheme is preferred ( Fig. 4.5 ).
A detailed description of the guidewires and their properties is presented in Chapter 2 , Section 2.5 . A tapered, polymer-jacketed wire (such as the Fielder XT, Fielder XT-A or Fighter) is usually used first to track a microchannel (which may sometimes be invisible). This attempt should be brief, unless progress is achieved.
If this wire fails to cross, and the course of the CTO vessel is well understood (especially if the CTO is short), a stiff, tapered guidewire (such as the Gaia 2nd) is preferred. If the course of the CTO is unclear, then a stiff, polymer-jacketed guidewire (such as the Pilot 200) or a composite core, moderate stiffness, nontapered guidewire (such as the Ultimate Bros 3) is preferred, because it is more likely to track the vessel architecture than exit the vessel wall.
Goal
Shape the wire tip to maximize the likelihood of successful CTO crossing .
How?
A small (1 mm long, 30–45 degrees) distal bend ( Fig. 4.6 ) is preferred for CTO crossing because it:
- a.
Enhances the penetrating capacity of the guidewire.
- b.
Facilitates entry into microchannels.
- c.
Reduces the likelihood of deflection outside the vessel architecture or into branches arising within the occlusion.
- d.
Improves steerability within tight spaces, such as the CTO segment, which would normally straighten larger bends.
Creating such a small bent can only be accomplished by inserting the guidewire through an introducer, rather than using the side of the introducer, as is commonly done for workhorse guidewires ( Fig. 4.7 ).
- a.
The guidewire is inserted through an introducer with approximately 1 mm protruding through the tip.
- b.
The guidewire tip is bent by 30–45 degrees (sometimes a syringe is used to bend the tip of very stiff guidewires, such as the Confianza Pro 12 guidewire, as they can puncture the operator’s glove).
- c.
The guidewire tip is inspected to verify optimal shaping.
- d.
The guidewire is withdrawn into the introducer and advanced into the microcatheter or over-the-wire balloon (it is best to insert the shaped guidewires into a microcatheter using an introducer to prevent potential tip damage or deformation).
Special care must be taken when shaping composite core wires because if their bend gets too sharp, it is difficult to straighten it and the attempts may damage the tip. In contrast, the polymer-jacketed guidewires are somewhat resistant to shaping and are prone to straightening during manipulations.
