Suggested Technique

Modified CART Technique: How to Maximize the Efficiency of CART and Reverse-CART Techniques to Cross CTOs

Sreejit Nair, MD; Ashwani Sastry, MD

Sunrise Vascular, North Carolina

Sreejit Nair, MD; Ashwani Sastry, MD

Sunrise Vascular, North Carolina

The treatment of chronic total occlusions (CTOs) poses a technical challenge for endovascular revascularization in both the coronary and peripheral arteries. Yet there has been significant progress made in the collective technical understanding of how to treat patients with an arterial CTO via endovascular methods.1,2 Experienced endovascular operators today have not only an armamentarium of catheters and wires and techniques to treat CTOs, but also a defined algorithm2 to escalate each as needed. For the treatment of peripheral vascular disease, when true lumen antegrade crossing of the occlusion fails, subintimal antegrade crossing can be attempted, typically by knuckling the wire in the subintimal plane and advancing to the end of the occlusion, termed STAR (Subintimal Tracking and Re-entry).3-5 However, crossing an occlusion through the subintimal plane in an antegrade fashion can have limited technical success, because it can often be difficult to re-enter the true lumen distal to the occlusion without resorting to use of a re-entry device.

The SAFARI (Subintimal Arterial Flossing with Antegrade-Retrograde Intervention) technique improves the technical success of subintimal crossing in cases where there is either (1) failure to reenter the true lumen distal to the occlusion or (2) a limited length of patent segment distal to the occlusion that the operator would like to preserve by not extending the subintimal dissection.6 The SAFARI technique in theory reduces the cost of the procedure, since a re-entry device is not needed.

In the SAFARI technique, a wire that is placed into the subintimal space of a CTO from the retrograde access is threaded into a catheter placed in the subintimal space of the CTO from the antegrade access. This setup allows a ‘through-and-through’ flossing wire to be placed in order to facilitate the completion of the intervention from the antegrade and/or retrograde access. However, in practice, arriving at this positioning can be quite time-consuming and often requires use of complex positioning of the x-ray tube and image intensifier to be able to thread the wire into the catheter. Additionally, if this wire positioning fails and a loop snare is required to secure the flossing wire, it can further add to the time of the procedure as well as significantly increase its cost (perhaps equaling the cost of a re-entry device).

Other, previously described techniques, such as CART (Controlled Antegrade and Retrograde Tracking and Dissection) as well as reverse-CART, have demonstrated excellent success in allowing antegrade or retrograde crossing of CTOs in both coronary and peripheral vascular intervention.7-9 In the CART/reverse-CART techniques, antegrade and retrograde wires are placed into the subintimal plane of a CTO. A balloon is placed and inflated from either an antegrade or retrograde approach into the subintimal space of the occlusion. The balloon is retracted and the opposite wire is advanced into the space created by the balloon. Since this space is in communication with the true lumen, the wire can be advanced into the true lumen, thereby crossing the occlusion.

In practice, there remains an element of “luck” in achieving a technically successful crossing with the traditional CART and reverse-CART techniques, as with the SAFARI technique. The CART and reverse-CART techniques also don’t solve the problem of excessive duration of the procedure, since these techniques remain more time-consuming than the average endovascular intervention.

To increase the odds in the operator’s favor and to help reduce the duration of the procedure, we propose the below escalation algorithm and for the following principles to be applied to the CART and reverse-CART techniques (“Modified CART technique”):

1. Take detailed angiographic pictures of the occlusion, defining the proximal and distal caps.

2. Attempt a true lumen crossing in an antegrade fashion with a crossing catheter and wire of the operator’s choice.

3. If true lumen antegrade crossing fails,  attempt the STAR technique in an antegrade fashion, keeping the knuckle of the wire tip small, so as to limit expansion of the subintimal plane.

4. If antegrade STAR fails, get retrograde access (for example, pedal access) and attempt retrograde true lumen crossing.

5. If retrograde true lumen crossing fails, attempt retrograde STAR, again keeping the knuckle of the wire tip small, so as to limit expansion of the subintimal plane.

6. If the retrograde STAR fails, attempt CART/reverse-CART as follows:

a. Place wire from antegrade access into subintimal plane of occlusion.

b. Place wire from retrograde access into subintimal plane of occlusion.

c. Place a suitable balloon over the wire from retrograde access into the subintimal plane of the occlusion, but not past the occlusion.

d. Inflate with the balloon in the subintimal plane of the occlusion, retract the balloon, and inflate again, with the balloon placed partially back into the true lumen distal to the occlusion.

e. Pull the retrograde balloon back into the true lumen distal to the occlusion, then loop the antegrade wire in the true lumen proximal to the occlusion, and then use it to reenter the subintimal plane with a support catheter placed close to the looped portion of the wire.

f. If CART fails, do the reverse-CART, using the same principles as above.

In our experience, in order to maximize chances of successful CART/reverse-CART, the subintimal plane needs to be expanded by the balloon only to the end of the chronic total occlusion (entry point) where the wire from the opposite access will be entering the subintimal plane from the true lumen. If the subintimal space is expanded by the balloon past this entry point, it may diminish the chances of a successful crossing. Furthermore, knuckling the wire from the opposite access prior to entering the subintimal plane seems to help the wire find the desired balloon-expanded subintimal plane rather than a different, undesirable subintimal plane. The latter happens more frequently, in our experience, if the wire is not knuckled prior to entering (Figure 1).

By keeping complex procedures as quick and effective as possible, we can improve their utility, reduce cost, reduce radiation to the patient and operators, and make complex procedures more feasible to perform.

Case Vignette

NM is a 84-year-old man with diabetes, hypertension, and dyslipidemia. He is a former smoker. He presented with a nonhealing ulcer of the base of the left 1st metatarsal and severe lifestyle-limiting rest pain of both legs (left > right) in April of 2020.

Duplex ultrasound was performed, revealing patent mid superficial femoral artery (SFA) and popliteal arteries; however, there was occlusion in the anterior tibial and posterior tibial arteries. The patient was medically optimized. Given his nonhealing ulcer, an angiogram was performed (Figures 2-10).

Angiography of the left leg was performed, revealing diseased but patent superficial femoral and popliteal arteries of the left leg. However, the anterior tibial and posterior tibial arteries were occluded.

In an attempt to recanalize the occluded posterior tibial artery, antegrade and retrograde crossings were initially unsuccessful. Therefore, our modified CART technique was employed as described in our algorithm. The posterior tibial artery was recanalized and we were able to restore flow to the plantar arteries. At a later date, we also were able to recanalize the anterior tibial artery to restore 3-vessel runoff to the foot. The patient’s ulcer healed within 4 weeks of this intervention. 

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