Abstract
There are several complex subsets of chronic total occlusion (CTO) lesions, such as CTOs with proximal cap ambiguity, impenetrable proximal or distal cap, flush aortoostial CTOs, ostial circumflex and left anterior descending artery CTOs, CTOs with bifurcation at the proximal and the distal cap, in-stent CTOs, saphenous vein graft CTOs, and heavily calcified CTOs. Moreover, use of hemodynamic monitoring and support may be needed in patients with heart failure. This chapter reviews various techniques for achieving recanalization of these complex CTOs.
Keywords
Bifurcation at proximal and distal cap, Chronic total occlusion, Flush aortoostial CTOs, Impenetrable proximal cap, Proximal cap ambiguity
9.1
Proximal Cap Ambiguity
Online Cases 2 , 5 , 16 , 30 , 32 , 33 , 34 , 45 , 47 , 49 , 51 , 55 , 56 , 69 , 80 , 88 , 93 , 104 .
Proximal cap ambiguity refers to the inability to determine the exact location of the proximal cap of the occlusion, due to the presence of obscuring side branches or overlapping branches that cannot be resolved despite multiple angiographic projections. It is encountered in approximately 31% of chronic total occlusion (CTO) percutaneous coronary interventions (PCIs) and is independently associated with technical failure. In the hybrid algorithm, proximal cap ambiguity is an indication for a primary retrograde approach ( Fig. 9.1 ); however, several antegrade options also exist ( Fig. 9.2 ).
9.1.1
Better Angiography
High-quality angiography, including dual injections and multiple, possibly steep, angiographic projections, may help resolve proximal cap ambiguity. Here are some examples :
- 1.
A Vieussens collateral (which is a collateral from the conus branch of the right coronary artery [RCA] to the left anterior descending artery [LAD]) may not fill with contrast if the RCA catheter is deeply engaged, or it may have a separate ostium instead of originating from the aorta. Contrast injections with the catheter less deeply engaged in the RCA can allow filling of the Vieussens collateral and help clarify proximal cap ambiguity ( Fig. 9.3 , Online Case 2 ).
- 2.
The origin of the CTO may overlap with the origin of a side branch. Various angiographic views with different angulation may help to separate the branches.
9.1.2
Computed Tomography Angiography
Computed tomography angiography (CTA) can help clarify the course of the occluded vessel ( Fig. 9.4 ), as well as provide information on the presence of calcification and tortuosity. CTA is particularly useful when the proximal lesion anatomy is unclear ( Section 3.3.6 ). There are ongoing efforts for coregistration of the coronary angiography and computed tomography images to facilitate crossing.
9.1.3
Intravascular Ultrasonography
Intravascular ultrasonography (IVUS) can help clarify the location of the proximal cap, especially when there is a side branch close to the occlusion ( Fig. 9.5 ). A short-tip, solid-state IVUS catheter is preferred as it can reach further down the vessel, allowing enhanced visualization. However, sometimes a smaller diameter rotational IVUS catheter can be used for smaller side branches that have a longer landing zone .
How?
- •
In ostial branch occlusions (e.g., ostial obtuse marginal CTO), inserting an IVUS in the main vessel can demonstrate the entry point into the occlusion (see Online Case 34 ) ( Fig. 9.5 ).
- •
In main vessel occlusions, if there is a side branch adjacent to the occlusion (classic example is LAD CTO at the takeoff of a large diagonal branch, see Online Case 93 ), the IVUS is inserted into the side branch to identify the beginning of the CTO.
- •
IVUS guidance can be either (a) real-time (i.e., crossing attempts with simultaneous IVUS visualization), or (b) intermittent (i.e., imaging, followed by crossing attempts, followed by reimaging, etc.).
- •
Real-time guidance has several limitations:
- 1.
It requires 8 Fr guide catheters if the Corsair or Turnpike microcatheters are used, or 7 Fr guide catheters if lower profile microcatheters (such as the FineCross or Micro 14) are being used. Alternatively, a ping-pong guide catheter technique can be used.
- 2.
Intravascular position of the IVUS during crossing attempts may interfere with guidewire manipulation and hinder simultaneous contrast injection.
- 3.
The IVUS catheter may require constant repositioning due to movement during guidewire manipulation. Hence, live IVUS guidance is infrequently used for wiring through ambiguous proximal caps, and intermittent (serial imaging) is preferred instead.
- 1.
- •
In both scenarios, IVUS can be used to demonstrate the wire position during antegrade wire-crossing attempts. If the wire is in the intima or the subintimal space, but within the occlusion, a microcatheter can be advanced over the wire to provide additional support and facilitate crossing. If not, the wire is withdrawn and redirected.
- •
If a suitable sized artery is available, the short-tip solid-state IVUS catheter is preferred (Eagle Eye short tip, Volcano); it minimizes the extent of distal advancement, which is needed for distal imaging, and is also more deliverable.
- •
Increasing the diameter of the field of view can be useful in visualizing the occluded vessel, particularly as it traverses away from the IVUS catheter.
What Can Go Wrong?
- 1.
Injury (including perforation) of the side branch from advancing the IVUS catheter, hence the IVUS catheter should not be advanced through very small or tortuous vessels.
- 2.
Thrombosis, due to insertion of multiple equipment in the coronary artery.
9.1.4
Move-the-Cap
See Online Cases 32 , 45 , 82 , 83 , and 104 .
The move-the-cap techniques use antegrade dissection/reentry to clarify the course of the occluded vessel and achieve crossing. There are three variations of this technique: the balloon-assisted subintimal entry (BASE) technique, the scratch-and-go technique, and the Carlino technique. Each allows the operator to decide on the site of proximal subintimal entry .
9.1.4.1
Balloon-Assisted Subintimal Entry ( Fig. 9.6 )
How?
- •
Use a slightly oversized compliant balloon (1.1:1 or 1.2:1 balloon:vessel diameter ratio).
- •
Check in orthogonal projections that the wire and balloon are actually within the intended segment.
What Can Go Wrong?
- •
Balloon may not advance due to severely diseased proximal vessel and/or severe calcification. In such cases predilation with a smaller balloon or other lesion preparation (e.g., with atherectomy or laser) may need to be performed first. Alternatively, a larger or more supportive guide catheter (such as Amplatz 1 for the RCA) or other guide supporting techniques, such as side branch anchor or guide catheter extension ( Section 3.6 ) may need to be used.
How?
- •
Through the guide catheter to verify that proximal vessel dissection has indeed occurred.
What Can Go Wrong?
- •
Propagation of the dissection either downstream (potentially compressing the distal true lumen) or upstream (causing aortocoronary dissection). This can be prevented by gentle injection under fluoroscopic or cineangiographic imaging. Side-hole guides, or partially disengaging the guide, can also reduce the contrast injection force.
How?
- •
Over the workhorse guidewire that was used to deliver the angioplasty balloon.
What Can Go Wrong?
- •
Inability to deliver microcatheter due to tortuosity or calcification (unlikely given prior balloon inflation). If it occurs, additional balloon dilations or increased guide catheter support may be needed.
How?
- •
Advance a polymer-jacketed guidewire (such as Fielder XT, Fighter, or Pilot 200) through the microcatheter. Wire is advanced by pushing, not turning, to minimize the risk for fracture
What Can Go Wrong?
- •
Perforation. Can be prevented by checking the wire course in orthogonal projections.
- •
Inability to form a knuckle. The wire tip may be reshaped into an umbrella-handle or other configuration, ensuring that the wire is folding back on itself rather than dissecting forward, before reinserting.
- •
Guidewire entrapment in the vessel wall ( Fig. 9.7 ). This is a very infrequent complication. Potential solutions include advancing a second guidewire next to the entrapped wire and performing balloon inflations in an attempt to free the wire. If the guidewire fractures, IVUS can help ascertain that there is no wire unraveling into the proximal part of the vessel or into the aorta.
Figure 9.7
Guidewire entrapment during antegrade dissection reentry.
Bilateral coronary angiography demonstrating a chronic total occlusion of the mid-left anterior descending artery ( arrow , A). Entrapment of a knuckled Fielder XT guidewire ( arrow , B). The chronic total occlusion was successfully crossed with a Pilot 200 guidewire ( arrow , C) advanced parallel to the entrapped guidewire. After balloon angioplasty was performed around the entrapped guidewire ( arrow , D), the entrapped guidewire was successfully retrieved (E) with an excellent final angiographic result ( arrow , F).
Reproduced with permission from Danek BA, Karatasakis A, Brilakis ES. Consequences and treatment of guidewire entrapment and fracture during percutaneous coronary intervention. Cardiovasc Revasc Med 2016; 17 :129–33 (see Online Case 24 ).
How?
- •
Once a wire knuckle enters the subintimal space it can be advanced through the occluded segment with very low risk of causing perforation due to the distensibility of the subintimal space. Reentry can now be set up beyond the distal cap of the CTO, ideally proximal to the origin of any large branches.
How?
- •
In most cases reentry is achieved as close to the distal cap as possible, using the Stingray system, as described in Chapter 5 . High-end reentry approaches, such as the “double Stingray” (see Online Case 80 ) or use of the retrograde approach, may be needed if the distal cap is at the bifurcation of a large branch (e.g., right posterior descending and right posterolateral vessel).
9.1.4.2
Scratch-and-Go ( Fig. 9.8 )
See Online Cases 2 , 16 , 32 , 45 , 59 , and 61 .
Step 1 Wire the Vessel Proximal to the Chronic Total Occlusion
How?
- •
Use any standard microcatheter, such as the Corsair and Turnpike.
- •
Check in orthogonal projections that the wire and microcatheter are actually within the intended segment.
What Can Go Wrong?
- •
Microcatheter may not advance due to severely diseased proximal vessel and/or severe calcification. In such cases predilation with a small balloon may need to be performed first. Alternatively, a larger or more supportive guide catheter (such as Amplatz 1 for the RCA) or other guide-supporting techniques (such as side branch anchor, or guide catheter extensions; Section 3.6 ) may need to be used.
How?
- •
Use stiff guidewire, such as the Confianza Pro 12, Gaia 2nd or 3rd, or Hornet 14.
- •
Shape distal tip at 90 degrees bend and 2–3 mm length.
- •
Advance guidewire into vessel wall proximal to the proximal cap. Only advance 1–2 mm into the wall to avoid perforation.
What Can Go Wrong?
- •
Wire may be advanced too far, causing perforation. Wire advancement alone is extremely rare to cause perforation, but if the microcatheter follows, perforation is possible.
How?
- •
Advance the microcatheter tip over the stiff guidewire toward the vessel wall (only a minimal distance, usually 1 mm or less).
What Can Go Wrong?
- •
Perforation, if the guidewire or microcatheter has exited the vessel wall, hence confirmation that the guidewire has not perforated (by antegrade contrast injection) is needed before advancing the microcatheter.
How?
- •
Insert a polymer-jacketed guidewire (such as the Fielder XT, Fighter, or Pilot 200) through the microcatheter.
- •
Advance (pushing without turning) to form a knuckle.
What Can Go Wrong?
- •
Perforation, inability to form a knuckle, and guidewire entrapment in the vessel wall, as described in Step 6 above.
Step 6 Creation of Knuckle Into Dissection Plane (as described in Section 5.4 )
Step 7 Chronic Total Occlusion Crossing (as described in Section 5.4 )
Step 8 Reentry (as described in Section 5.4 )
9.1.4.3
Carlino Technique for Resolving Proximal Cap Ambiguity ( Figs. 9.9 and 9.10 )
The Carlino microdissection technique is described in detail in Chapter 5 , Section 5.6.3 . The Carlino microdissection technique has multiple other uses, such as to facilitate crossing of wire-uncrossable lesions and forward advancement during antegrade subintimal crossing attempts ( Figs. 9.9 and 9.10 ).
How?
- •
The Carlino technique can be used after a microcatheter tip has entered the subintimal space before, during, or after guidewire advancement attempts, to facilitate subintimal dissection, and also to confirm that the wire tip is indeed located within the subintimal space.
Step 1 Wire the Vessel Proximal to the Chronic Total Occlusion
Step 2 Advance Microcatheter Proximal to Proximal Cap
Step 3 Insert Stiff Guidewire Over Microcatheter and Advance Toward Vessel Wall
Step 4 Advance Microcatheter Over Stiff Guidewire Inside Vessel Wall
How?
- •
Use a small (usually 3 cc) luer lock syringe.
- •
Inject a small amount (0.5–1.0 mL) of contrast gently under cineangiographic guidance.
What Can Go Wrong?
- •
Perforation. The risk can be minimized by injecting a small amount of contrast and meticulous fluoroscopic visualization of the injection.
- •
Retrograde contrast propagation causing side branch or proximal branch occlusion.
(Sometimes the contrast might dissect into the distal true lumen.)
Step 7 Chronic Total Occlusion Crossing (as Described in Section 5.4 )
9.1.5
Retrograde Crossing
See Online Cases 5 , 31 , 33 , 36 , 51 , 56 , 69 , 70 , 88 , and 104 .
Retrograde crossing can provide an excellent solution to proximal cap ambiguity, as the retrograde guidewire can be advanced either in the true lumen or in the subintimal space to the proximal cap, clarifying the vessel course and resolving the proximal cap ambiguity. Moreover, the retrograde guidewire can modify the proximal cap, facilitating antegrade crossing (see Online Case 102 ). The Carlino technique can be used through the retrograde microcatheter (see Online Case 62 ) and retrograde balloons can be used to perform the controlled antegrade and retrograde tracking and dissection (CART) technique.
9.2
Impenetrable Proximal (or Distal) Cap
Heavily calcified or fibrotic proximal (or distal) caps may be challenging or impossible to penetrate with a guidewire. Distal caps may be particularly challenging to cross in patients with prior coronary bypass graft surgery, presumably because the distal cap was exposed to systemic arterial pressure when the bypass graft was patent and also because bypass graft surgery can lead to severe calcification. There are several possible options for crossing such caps, which can be grouped into two major categories: (1) get-through and (2) go-around ( Fig. 9.11 ).
9.2.1
Get-Through
Advancing through a wire impenetrable lesion can be achieved via (1) strong guidewire support and/or (2) high penetrating power guidewires or devices. Novel technologies are currently in development and could facilitate crossing of such lesions, such as the Soundbite system and administration of collagenase.
Strong guidewire support can be achieved via various microcatheters (especially the more supportive Corsair and Turnpike Spiral), support catheters, guide catheter extensions, and anchoring techniques, as described in Section 3.6 . A variation of the coaxial anchoring technique is inflating a balloon next to a microcatheter, hence providing support by pressing against the vessel wall (power microcatheter; Fig. 9.12 and Online Case 82 ). This approach can also be used to power anchor a guide extension catheter for even more support, but requires a second guide catheter system (e.g., ping-pong guide).
