Combining Technical Skill With a Uniquely Designed Device for CTO Success

Introduction

J.A. Mustapha, MD

Chronic total occlusions (CTOs) in the infrainguinal arterial bed have variable characteristics.  It is fair to say that not all CTOs are created equal, hence the unpredictability of crossing as well as outcome of successful CTO crossing, despite the evolution of skills and technologies. The question that has not been answered yet is whether we have combined the technologies with the proper techniques to extract the most value of the tool that is built specifically for a disease state, such as the Wingman (ReFlow Medical) for CTO crossing and the Spex Catheter for re-entry (ReFlow Medical). In this issue, I am honored at the chance to interview Dr. Mahmood Razavi, one of the pioneers in CTO crossing who has historically demonstrated that combining proper technical skill to a uniquely designed CTO device provides a favorable success. I am hoping to show you his view during this interview. I also feel that it would be helpful to us, as physicians, to dive into the minds of engineers who develop tools for us to use without any clinical experience, but yet they manage to build devices that help us in our day-to-day practice. Isa Rizk and his company, ReFlow Medical, have agreed to share with us the mechanism of action behind their CTO and re-entry devices, and describe why they should be utilized in complex infrainguinal CTOs.

J.A. Mustapha, MD: Dr. Razavi, you have pioneered many techniques for infrainguinal CTO crossing using many different tools. Can you describe to us different composition in the variable types of CTOs you encounter, both above and below the knee? 

Mahmood Razavi, MD: Thank you, Dr. Mustapha, for the opportunity to discuss some of the issues surrounding this important topic. Plaque composition in various vascular beds and its correlation to disease progression and subsequent symptoms is now well recognized. Similarly, acute endovascular success and patient outcome appear to be associated with the content/composition of the occluded vessel. 

Hence plaque composition and morphology (calcification, eccentricity, etc.) are important independent procedural prognosticators. In addition, you have taught us that the configuration of both proximal and distal caps matter. They determine the degree of difficulty in crossing a CTO as well as the need for utilization of adjunctive techniques once the vessel is crossed. 

It has long been known that the surface of the occluded segments exposed to blood (cap) is usually platelet-rich and depending on the chronicity of the occlusion, may be endothelialized. These features make its penetration more difficult. Underlying calcified plaques, when present, add to the challenge of a successful crossing. 

Angiographic features of both proximal and distal caps such as concavity versus convexity, smooth versus fissured, calcified versus fibrotic, and presence or absence of an adjacent collateral, for example, impact the ease of crossing, utilization of materials (hence the procedural costs), and outcome of the intervention.

Once the cap is crossed, it is not always possible (and perhaps occasionally not desirable) to maintain an intraluminal position for the length of the CTO. Once again, presence, extent, and type of calcifications can affect both procedural success and medium-term vessel patency (long-term patency of such interventions is not well documented in the literature). On the topic of calcification, for example, studies have shown that its presence in the infrageniculate arteries appears to be a better predictor of amputation than ankle brachial index (ABI). 

It should be kept in mind that occluded vessels may contain clot at various stages of organization, as well as non-adherent components of atherosclerotic plaques with propensity for distal embolization once flow is reestablished. If such is suspected, we perform vigorous aspiration thrombectomy throughout the length of the occlusion prior to angioplasty. 

Finally, I think a brief discussion of inflammatory conditions such as thromboagiitis obliterans is helpful. Crossing of the fibrotic lesions may be as challenging as any atherosclerotic plaque and outcome of interventions appears to be inferior. This is also true of restenotic lesions, which are mainly composed of hyperplastic tissue. 

Dr. Mustapha: Based on your description, it seems as if CTOs, although they might be present in the same location, almost never have the same CTO cap composition. Please explain to us how you manage to use the Wingman to increase your CTO crossing success rate. Do you use an algorithmic approach?

Dr. Razavi: Yes, I do use an algorithmic approach to CTOs, starting with a simple support catheter and wire, and escalating as needed. In our practice, this type of hierarchical approach can reduce costs while avoiding unnecessary prolongation of the procedure. Penetration into a smooth concave cap is not always easy. On the other hand, convexities often direct the plane of dissection into the subintimal space, which may require re-entry maneuvers more distally. This is made even more challenging in the presence of either calcification or a large collateral emanating smoothly at the cap. 

I have a fairly low threshold for switching to backup crossing devices such as the Wingman. Reducing procedural times and radiation to the patient and medical personnel are important considerations. A lab involved with CTOs should be well stocked to be able to deal with more challenging cases. In such cases, being penny-wise is truly dollar-foolish. 

When the wire fails to penetrate or the catheter cannot be advanced, the Wingman and Spex catheter can be helpful. Use of the Wingman is fairly intuitive with a short learning curve. The braid-reinforced construct improves pushability and its extendable beveled tip can engage the cap or tough plaque to penetrate lesions better than support catheters. The Wingman’s ability to be used in a coaxial or triaxial fashion using a wire of my choice is another distinct advantage of the system. Once the CTO is crossed, the Wingman is withdrawn, and a balloon or atherectomy device is advanced. If a hydrophilic or a heavy tip wire unsuitable for intervention has been used to cross the lesion, it can be exchanged through the Wingman without the need for an additional intermediary catheter exchange. 

Dr. Mustapha: Historically, many of us tend to always start with a wire and catheter technique to cross any type of CTO. And when we fail, we usually fail due to a deep subintimal dissection or a perforation. Do you believe the Wingman can still be used after a failure to cross with a wire/catheter technique that meets one of the above complications?

Dr. Razavi: In above-the-knee cases, failure to cross using standard catheter-wire techniques is usually due to a deep subintimal path and inability to reenter the reconstituted lumen distally. Perforation is thankfully rare and can be avoided by keeping the plane of dissection close to the expected path of the vessel by the use of a crossing catheter or device with a shallow angle to redirect as needed. 

In below-the-knee cases, recanalization failure is more commonly due to inability to reenter, dense calcified lesions preventing wire/catheter advancement, and perforations. 

As mentioned above, Wingman is particularly useful for cap penetration and advancement through tough lesions. Perforations need to be handled differently. If the wire goes extraluminal, I usually back away the catheter well above the level of the perforation and construct a different crossing path (or well below if using a retrograde access). Wingman could be very useful in such situations, allowing the operator to create a new plane of passage away from the perforation. Creating reentry tears, however, is not a feature of Wingman (or at least I have not used it for such). The Spex catheter, on the other hand, can be fashioned to act as both an effective support catheter and a reentry device. As with any new device, there are nuances and features that the operators need to be familiar with. What I like about the engineers at ReFlow Medical is that they have been very responsive to physician input and feedback to improve the performance of these products. 

Dr. Mustapha: In rare cases where, despite all you do, you are stuck in the subintimal space at the level of the distal CTO cap, you have presented the method of using the Spex catheter of the Wingman to re-enter into the true lumen. I find this to be very intriguing. How did you think of such an approach and what are the steps that are needed to ensure success? 

Dr. Razavi: As you are well aware, the current reentry devices in the U.S. have substantial limitations that preclude their use in significant proportion of patients with long CTOs. The idea behind the Spex catheter was to create a suitable crossing catheter that can also act as a reentry device. The engineers at Reflow Medical have done a nice job conferring pushability and trackability, as well as directionality and torque control to the device, some of which are best in class, in my opinion. This allows for the use of the same catheter to both cross tough lesions and reenter if necessary. 

In ipsilateral antegrade common femoral artery (CFA) access, I tend to place a shallow angle on the Spex near its tip. This will allow directional control without hampering pushability and trackability of the catheter. If my access is through a contralateral CFA with a crossover sheath, then I use the angle of the sheath over the aortic bifurcation to confer the angle onto the Spex, which is usually sufficient. 

If distal reentry becomes necessary, two techniques can be used with the Spex. First, sequential clockwise-counterclockwise rotation of the angled Spex catheter at the distal cap frequently breaks through and allows wire passage into the true lumen. A second approach is to point the tip of the Spex in the direction of the reconstituted lumen and use a heavy tip wire to cross the flap. Spex has the directional control and tip fidelity to give support to the crossing wire. 

Dr. Mustapha: Is there any type of CTOs where you find it most suitable to start with the Wingman rather than beginning with the wire/catheter technique? 

Dr. Razavi: Penetration of certain cap configurations and vessel morphologies pose difficult challenges. These could include smooth concavities with no fissures for wire engagement, smooth runoff into an adjacent collateral, flush occlusion of proximal SFA or a tibial artery, dense calcified luminal plaques, etc. In such cases there is a high probability of failure of standard catheters to cross. Having said that, I still start with my favorite standard wire and catheter before going to the Wingman or Spex. 

Case Reports

Case #1

This is a 73-year-old male with worsening right lower extremity claudication and occluded, densely calcified superficial femoral artery (SFA). 

A)-B) Digital subtraction angiograms show the occluded SFA with reconstitution of the popliteal artery.

C) Initial attempts at luminal or subintimal crossing of the calcified segment using standard hydrophilic catheters and wires failed.  Subsequently, a Wingman was used tofacilitate crossing.

D)-E). Following successful crossing of the occluded segment with Wingman, stents were placed after prolonged high pressure balloon angioplasty reestablishing flow. 

Case #2

This case demonstrates use of the Spex catheter to cross and gain distal reentry in an occluded SFA.

A) Antegrade access into the ipsilateral common femoral artery (CFA) and occluded SFA.

B) Subintimal crossing of the chronic total occlusion (CTO) was performed, but distal reentry could not be achieved. The catheter was then changed to the Spex catheter, directing it towards the reconstituted popliteal artery. 

C) Wire passage was secured using the Spex catheter and a V-18 wire, which was then switched to an exchange .035-inch wire for percutaneous transluminal angioplasty and stent placement. 

D) Post-procedural digital subtraction angiography with re-establishment of flow in the SFA. 

Cases by Mahmood Ravazi, MD

Disclosure: Dr. Mustapha reports he is a consultant for Bard, Covidien, Cordis, CSI, Spectranetics, Boston Scientific, Cook, and Terumo. Dr. Razavi reports he is an adviser/consultant to Abbott Vascular, Boston Scientific, Bard, Medtronic, Reflow, and Veniti; he is a co-principal investigator for Spectranetics, Veniti, and Mercator.

Dr. J.A. Mustapha can be contacted at jihad.mustapha@metrogr.org.
Dr. Mahmood Razavi can be contacted at jpigott@venturemedgroup.com.