1. Is the proximal cap ambiguous in its location?
2. Is the target distal vessel diseased, or is there a bifurcation at the distal cap?
3. Is the lesion length longer than 20 mm?
4. Is there a collateral or a graft (patent or occluded) that can be used as a conduit to deliver some retrograde gear (‘interventional collateral’)?
The algorithm is depicted in Fig. 11.1. The philosophy of hybrid is to maximize the likelihood of success while limiting the amount of contrast, radiation and time. This is done by selecting the most appropriate strategy to start with, and then rapidly switching from a failing to alternative approaches allowing testing of multiple strategies during the procedure. A retrograde approach should be adopted first when the proximal cap is unclear (because of either proximal cap bluntness, significant side-branches or poor visualization of the true distal vessel), the distal vessel is diseased, or when the distal cap is at a bifurcation. However, this is conditional to the presence of an interventional collateral. If the proximal cap is clear and the distal vessel is not severely diseased, without major side branches at the distal cap, the first approach should be antegrade. After selecting the direction (antegrade or retrograde), the crossing strategy will depend on occlusion length. When coming retrograde, and facing a short occlusion (<20 mm), a true-to-true (TTT) crossing attempt with sequential wires should be attempted first. However, if the lesion length is >20 mm, a retrograde DR with reverse-Controlled Antegrade and Retrograde Technique (R-CART) should be performed. When coming antegrade, with short lesions (<20 mm), a TTT crossing should also be attempted first. However, for lesions longer than 20 mm, antegrade dissection re-entry (ADR) with CrossBoss and Stingray is the preferred approach. Failing with the first strategy is not uncommon with the approach; nevertheless, success rates with the hybrid approach can reach over 90 %, because of the use of multiple strategies in the case of failing ones.
Fig. 11.1
The original hybrid algorithm
The hybrid approach adoption has been associated with improved procedural success, adequate procedural safety, and improved efficiency, but among these three barriers to CTO-PCI adoption, procedure time and resource utilization remain well above non CTO-PCI [11]. Since these publications there have been significant advances in the approach to common obstacles encountered during hybrid CTO-PCI procedures, many of which have been published as stand-alone techniques. The purpose of this chapter is to describe ten common obstacles to successful and efficient CTO revascularization and to provide pragmatic procedural solutions in a logical sequence to overcome these barriers, leading to an expanded hybrid CTO PCI algorithm as shown in Fig. 11.2. A structured approach to these CTO-PCI obstacles should facilitate the systematic evaluation and further refinement of the Hybrid approach that ultimately improves operator efficiency and success of CTO PCI.
Fig. 11.2
Enhanced hybrid CTO PCI algorithm. Acronyms: ADR antegrade dissection and re-entry, CART controlled antegrade and retrograde sub-intimal tracking, CTO chronic total occlusion, IVUS intra-vascular ultrasound, LAST limited antegrade subintimal tracking, MDCT multi-detector cardiac tomography, STAR sub-intimal tracking and re-entry, TTT true-to-true, RDR retrograde dissection and re-entry, WE wire escalation
Common Problems and Solutions
Problem 1: Failure to Penetrate a CTO Cap (Antegrade or Retrograde) Using Standard Guidewire Escalation Techniques
Definition
Suggested Approach
End around, break the cap, then bailout to the alternate approach.
End Around
Like the trick American football play “End around”, the Hybrid operator with a mastery of re-entry techniques can functionally move around the resistant cap in the subintimal space. The subintimal space should be accessed proximally in the antegrade approach and distally in the retrograde approach. The end around should be avoided if possible when major left ventricular side branches arise near the cap as these branches are at risk for occlusion with dissection techniques. There are two ways to perform an end around:
1.
Balloon assisted subintimal entry (BASE) is a technique where the intention is to cause an intimal disruption in the vessel thereby expediting safe wire and catheter access to the subintimal space (Figs. 11.3 and 11.4) [12]. This technique can be used to get around and avoid resistant CTO caps. It is particularly useful in the antegrade approach when there is an adequate stump or segment of vessel in which to place a balloon, and is most effective when there is disease within the segment. Using standard techniques, a balloon sized at a ratio of 1:1 with the artery is inflated above nominal pressure in the vessel proximal to the impenetrable cap. Once the balloon is deflated and removed, a Corsair (Asahi-Intecc, Japan) catheter is advanced to the dilation site. A jacketed wire (e.g. Fielder XT (Asahi-Intecc, Japan) or Pilot 200 (Abbott Vascular, USA)) is advanced toward the vessel wall and manipulated into the subintimal space where it is knuckled over and advanced forward. For very proximal disease, it is not uncommon to notice that the guide catheter moves towards a dissection plane created by the balloon inflation. A very gentle contrast injection (less than 1 cc) is sometimes enough to confirm that the dissection maneuver was effective, and the operator can follow with the knuckled wire as described (Fig. 11.4, Videos 11.1, 11.2, 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, 11.9, 11.10, and 11.11). After confirming the knuckled wire is within the wall of the artery (the wire is moving in concert with the vessel) an antegrade or retrograde dissection and re-entry strategy may be employed depending on the direction chosen for the approach to the CTO. The knuckled wire should be stopped at least 10 mm before the target and the dissection finished with the Crossboss Catheter (Boston Scientific, USA) when employing this technique antegrade (see Chap. 6 and 7). When performing this procedure retrograde, re-entry is made with R-CART described elsewhere [13] and in Chap. 9.
2.
The “scratch and go” technique can be employed if BASE is not possible or difficult (i.e. short stump or potential side branch compromise) (Fig. 11.5). In this maneuver a stiff tapered guidewire e.g. Confianza Pro 12 (Asahi-Intecc, Japan) with a 60° 3–4 mm single tip bend, is loaded into a Corsair catheter and used to “scratch” or penetrate the intima proximal to the cap, thereby allowing access to the subintimal space. Once the subintimal space is entered, the Corsair catheter is inserted 1–2 mm into the subintimal space without letting the wire move forward or backward. This requires meticulous control of the wire while rotating and controlling forward advancement of the Corsair. After confirming the catheter is within the wall of the artery (the catheter is moving in concert with the vessel), the stiff wire is exchanged for a polymer jacketed wire which is then intentionally knuckled and pushed in the subintimal space past the cap. At this juncture, an antegrade or retrograde dissection and re-entry strategy may be employed depending on the direction chosen for the approach to the CTO.
Fig. 11.3
Balloon-Assisted Sub-intimal Rentry (BASE) technique. (a) A balloon is used to dilate and create dissection planes proximal to the ambiguous proximal cap. (b) A wire is used to puncture towards the artery wall. (c) A microcatheter is advanced, its tip engaging under the plaque. (d) A wire is knuckled in the sub-intimal space to gain control of the artery
Fig. 11.4
(Videos 11.1, 11.2, 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, 11.9, 11.10, and 11.11). Balloon-assisted sub-intimal entry (BASE) and blind stick techniques. (a, b) A more than 20 mm RCA CTO with a very ambiguous proximal cap, largely because of the presence of several ipsilateral bridge collaterals (Videos 11.1 and 11.2). (c) Retrograde approach with a Sion through the large epicardial CC from the LCX to the PLV (Video 11.3). (d) Failure to connect into the distal RCA, with sub-intimal tracking in the last few mm (Video 11.4). (e) Antegrade bailout with BASE (Balloon-Assisted Sub-intimal Entry). After dilating the proximal RCA segment with a 3.0 mm balloon, a very tiny injection was performed with 1 cc of contrast, showing a dissection plane (Video 11.5). (f) A Fielder XT is knuckled into the dissection plane, with the support of a CrossBoss (Video 11.6). (g) The CrossBoss is advanced to the distal RCA for re-entry (Video 11.7). (h) A Stingray ballon is in place (Circle), but an antegrade hematoma is compressing the true lumen. Suction of blood from the Stingray ports did not improve visualization (Video 11.8). (i) A first stick is performed through the port pointing upward, as the common position of a Stingray following a CrossBoss is following the greater curvature of the artery (Video 11.9). (j) Successful swap with a Pilot 200 shaped as the Stingray wire (Video 11.10). (k) Final result after DES deployment (Video 11.11)
Fig. 11.5
Scratch and go technique. (a) A sharp wire is directed towards the sub-adventitial space. (b) Following advancement of the microcatheter, a polymer-jacketed guidewire is knuckled in the space
Break the Cap
The second option is to break up the cap with a “hydraulic dissection” or excimer laser (antegrade cap only).
1.
Breaking the cap by hydraulic disruption can be performed either antegrade or retrograde using a Corsair catheter driven into the cap often only a millimeter or two (Fig. 11.6). Through this catheter, 0.5–1 ml of contrast is briskly injected under fluoroscopic visualization. If contrast is tracking in the wrong direction the injection should be terminated. This has been called the “modified Carlino technique” [14], and the reader should refer to Chap. 8 for more details. In addition similar to dissecting the vessel with a microcatheter, the same can be accomplished by injection of a small amount (2–3 ml) of contrast through a wedged antegrade guide or guide extension catheter, as described earlier for the BASE technique. While intentionally dissecting a vessel was considered anathema to mainstream interventionalists, the development and use of reliable and safe re-entry techniques [15] by hybrid operators makes these tasks preferable to the use of stiff tapered guidewires which can more easily cause perforations.
2.
In situations where the antegrade proximal cap is defined and tapered, breaking the cap can be performed with the excimer laser (Spectranetics, Inc., USA). This can be achieved with either the coronary or peripheral 0.9 mm excimer laser (ELCA and Turbo elite, Spectranetics, Inc., USA) delivered to the proximal cap. Laser photoablation is then performed for 30 s to 1 min, in order to soften the proximal cap and facilitate either penetration by a wire or Crossboss catheter. It should be emphasized that the proximal cap morphology should funnel the laser toward the occlusion and not the sidewall of the vessel to avoid perforation. Thus the laser is not suited for eccentric or ambiguous proximal caps.
Fig. 11.6
Contrast-induced hydraulic micro-dissection. (a) A small amount of contrast is injected from the tip of the microcatheter, modifying the proximal cap compliance. (b) A wire is advanced into the dissection planes
Bailout
If all of the above fail, the third option is to reverse directions (antegrade to retrograde or retrograde to antegrade). When working antegrade, if suitable collaterals exist, or when working retrograde if proximal cap ambiguity can be solved, a knuckled wire can be pushed to the resistant cap from the opposite direction. The knuckled guidewire will create a space in the vessel wall beside the cap and serve as a target for a stiff tapered guidewire from the opposite direction.
All of these techniques require the operator to be experienced with subintimal crossing and both antegrade and retrograde re-entry techniques. Further, they should be employed in sequence with rapid switching in order to avoid getting stuck in a failure mode.
Problem 2: The Device-Uncrossable Antegrade or Retrograde Cap
Definition
A wire has successfully crossed the CTO into the true lumen but no catheter or balloon can cross the lesion. In this instance it is assumed the guide support has been maximized with either a guide extension or anchor balloon.
Suggested Approaches
The options available include balloon-assisted microdissection (BAM), Laser, Tornus, rotational atherectomy (RA), external crush, and end around techniques. The choice is somewhat dictated by the approach (antegrade vs retrograde).
1.
To perform the BAM technique for a ‘device resistant’ CTO lesion, advance a 1.2–1.5 mm balloon (at least 20 mm because it has a longer length before getting to the marker which is the widest profile on the balloon) and attempt to wedge the balloon into the lesion. Then inflate the balloon up to rated burst pressure and deflate, noting whether the balloon can move forward. If it moves forward, continue to dilate from proximal to distal. If the balloon cannot be advanced further antegrade then inflate the balloon until it ruptures, causing a hydraulic dissection of the proximal cap. The key to limiting the dissection with this strategy is careful attention to the insufflator pressure, as soon as the pressure falls (due to balloon rupture), aspiration is performed and the balloon removed. Afterwards, the operator should retry crossing with a small balloon or microcatheter (Fig. 11.7).
Fig. 11.7
Balloon-Assisted Microdissection (BAM). (a) A small balloon is inflated above its rate-burst pressure, modifying the proximal cap compliance. (b) A wire is advanced into the dissection planes
2.
If still unsuccessful, or alternatively, a 2.1 or 2.6 Fr Tornus (Asahi-Intecc, Japan) catheter can be utilized to dotter the resistant portion of the lesion and can be especially useful for highly calcified proximal disease [16].
3.
Next, if available, a 0.9 mm rapid exchange laser catheter can be used to photoablate the resistant portion of the lesion. The laser catheter is advanced to the point of resistance and activated at a fluency of 60–80 and frequency of 60–80 pulse/s. This technique is preferred when the resistant tissue is fibrous and non-calcified [17].
4.
If the wire is in the true lumen and the above techniques do not work or cannot be utilized then the external crush technique can be performed. Here, a second wire is inserted into the subintimal space next to luminal wire. Then a balloon (sized 1:1 to the artery) is inflated to crush the plaque from the subintimal space and enable gear to then move over initial true lumen wire [18].
5.
If the above fail, the operator should advance a Finecross (Terumo, Japan), a Valet (Volcano, USA), a Turnpike (Vascular Solutions, USA) or a Corsair (Asahi Intecc, Japan) microcatheter as far distally as possible through the lesion, attempt rewiring the lesion with a RotaWire and performing rotational atherectomy (RA) (Rotablator, Boston Scientific, USA). The tip of the RotaWire should be shaped with a very short 1 mm bend, as for CTO wires, and drilling of the wire should be applied to re-cross through the channel created with the previous wire. The distal end of the RotaWire can hinder effective wiring, if so, one can cut the last 2 cm of the tip off of a rota-floppy wire and position the RotaWire such that the radiopaque transition is more than 5 mm beyond the resistant portion of the lesion. RA is then performed with a 1.25 mm burr, at 180,000 revolutions per minute.
6.
If these techniques fail, then entering the subintimal space partially through the lesion with a knuckled wire or the Crossboss catheter and re-entry performed with the Stingray balloon and Stingray wire (Boston Scientific, USA) can also be attempted. Otherwise proceed to the “end around” algorithm or “bailout to another approach” as outlined above.
Tackling device resistant lesions when working via a retrograde approach, primarily involves placement of retrograde wire into the antegrade guide. The operator should bring an Rx balloon into the antegrade guide and inflate at high pressure to trap the tip of the retrograde guidewire in the antegrade guide. This maneuver provides a stronger wire platform with greater pushability for the retrograde microcatheter. Then, we should retry crossing the lesion with the retrograde Corsair followed by a Finecross microcatheter. Next, the operator should consider retrograde balloon dilation of the spot where the Corsair won’t cross with 1.2–1.5× 20 mm balloon and progress on to BAM if necessary. If all else fails follow the “end around” algorithm to go around the resistant portion of the lesion in a new tissue plane and repeat retrograde dissection re-entry at new more proximal location.
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