VEITHSymposium: A Wire and a Catheter: Techniques for Crossing Lower Extremity CTOs

What considerations are important when planning for the successful treatment of a chronic total occlusion in the lower extremities?

Chronic total occlusions (CTOs) are a complex clinical scenario. For lower extremity intervention of CTOs, successful treatment involves several variables. One is the experience of the physicians or the operator. Are they a beginner, are they intermediate, or do they have advanced skills and training? As you go along the spectrum from beginner to more advanced, fewer adjunctive devices will be required to complete the procedure. The majority of physicians with advanced-level skills can complete a CTO case using just a wire and a catheter to cross the occlusion and to re-enter the true lumen. Another variable to consider is the complexity of the lesion itself. Is it a short or long lesion? Is it calcified or non-calcified? Does the occlusion have a thrombotic component (suggestive of recent occlusion) or is it just a “complete” (chronic) occlusion? 

There are essentially two steps to successful completion of a CTO procedure. Step one is crossing the occlusion and step two is re-entry into the true lumen (Figure 1). In the BASIL trial (Bypass vs. Angioplasty in Severe Ischaemia of the Leg), a multicenter, randomized trial, the occurrence of failure was highest during these two steps.1 Reentry into the true lumen experienced the highest rate of failure, followed by crossing the occlusion. 

What are the strategies for avoiding failure with the use of just a wire and catheter?

There are three possible techniques when using a wire and catheter (obviously the cheapest form of treating a CTO): the loop technique for subintimal angioplasty, the intraluminal CTO technique, and a balloon-assisted CTO technique. 

Loop technique (subintimal angioplasty). By forming a loop with the wire, this technique permits access and traversing of the subintimal space, and then a return to the true lumen. Begin by using an angle catheter — usually a 4 or 5 French vertebral catheter can be used, and we use an .035” hydrophilic wire (Figure 2). Once you get into the subintimal space, push and pull on the wire in a back and forth motion until the tip of the wire forms a loop. As the loop is formed, you force it down into the occlusion, and as you emerge from the occlusion, the loop, more likely than not, will go back into the true lumen (see Figures 3a-3h for an example of this technique). If you don’t get back in the true lumen, then a reentry device can be utilized.

Intraluminal CTO technique. In this technique, the operator uses a 4 or 5 French straight-tip catheter and a straight-tip hydrophilic .018” wire. The wire is directed by using the catheter close to the center of the occlusion, pushing through the occlusion and, hopefully, emerging back in the true lumen on the other side. If you fail to reenter the true lumen, again, just like with subintimal angioplasty, a reentry device can be used to gain access to the true lumen. 

Balloon-assisted CTO technique. Use of a balloon-assisted CTO technique means that the operator is unable to get into the proximal cap (occlusion) with only a wire and catheter. The proximal portion of the CTO is the toughest or hardest part of the plaque, so it can be very difficult to get in with just a wire and a catheter. This technique involves the placement just above the occlusion of a short balloon that is the same diameter as the vessel. The balloon is inflated to the diameter of the vessel, then a CTO wire or a stiff wire is used to pierce through the balloon into the plaque. The balloon stabilizes and centers the lumen of the channel of the wire, allowing the operator to pierce the plaque with a CTO wire or a stiff wire. Once we get in, the balloon is used as an assist to guide the wire through the rest of the occlusion, and hopefully it will emerge through the end back in the lumen. Failure to reenter back in the true lumen means the use of a reentry device. 

Devices to overcome failure. Failure to cross, based on skills or based on experience, opens the door to device use, such as a laser, ultrasound-guided device, or devices such as the Frontrunner (Cordis), in order to go through the plaque. Failure to get back in the true lumen can be corrected with the use of reentry catheters such as the Outback (Cordis), Pioneer (Volcano Corporation), and OffRoad (Boston Scientific). Essentially, once the operator is back in the true lumen, the endovascular intervention can proceed as planned. 

What is your history with these techniques?

My success rate is over 90% by just using the wire and a catheter. My usage of devices is less than 10%. 

Are there increased time concerns when you use only a wire and catheter?

If the operator is experienced, the procedure will still go fast. If the operator’s experience is limited, that may add time. One of the advantages of using devices, such as a crossing or reentry device, is to minimize radiation both for the physician and the patient, minimize contrast use, minimize procedure time, and increase success. It is most useful and more likely for an operator who is a beginner or intermediate. Physicians with advanced skills may initially attempt a CTO procedure with a wire and catheter, and give it anywhere from 10 to 30 minutes. If, after that time period, things don’t work out, then the decision to convert and get help from a crossing and/or reentry device is made.

So often, we hear “don’t push” and “don’t force.” Are these instructions equally applicable to a CTO procedure?

The CTO is not a delicate procedure. It’s not like carotid stenting, where the operator needs to be very delicate. The CTO, if you will, is a rough procedure, at least rough in terms of getting started with the CTO, going into the subintimal or intraluminal space, and then going through the occlusion. Returning to the true lumen does require more gentleness. So at least the first part of the procedure, getting into the subintimal space and crossing the occlusion, is rough. If we look at physicians who do carotid stenting along with physicians who do peripheral angioplasty and stenting, we all have different dexterity in terms of the sensory perception that we develop in our fingertips. For example, if you do an angioplasty of the femoral artery and pass the wire through a lesion, it is done very delicately. If you are doing carotid stenting, you must be even more delicate in passing the wire and protection device. When you are doing endovascular aortic repair (EVAR), these are stiff wires in the body, so you are pushing the device in with some force. A CTO procedure does fall into the category of requiring a rough technique, at least at the beginning of the procedure, but then gentleness is required to get the wire back into the true lumen. n

Dr. Ali Amin can be contacted at amin007@verizon.net.

Reference

1. Adam DJ, Beard JD, Cleveland T, et al. Bypass versus angioplasty in severe ischemia of the leg (BASIL): multicenter, randomized controlled trial. Lancet. 2005; 366: 1925-1934.