CLI PERSPECTIVES

The Value of Atherectomy in CLI

November 5, 2017
Authors: 

CLI Perspectives is headed by section editor J.A. Mustapha, MD, Metro Health Hospital, Wyoming, Michigan. 

Dr. Mustapha interviews Thomas M. Shimshak, MD, FACC, FSCAI, Interventional Cardiologist, Medical Director Heart and Vascular Center, Florida Hospital Heartland Medical Center, Sebring, Florida.

It is time for us to start using a superior technical approach by adding ultrasound to groin access, whether retrograde or antegrade, simply due to the fact that operators can visualize a segment. This can ensure an exit strategy can be safely closed or manually compressed before first stick.

J.A. Mustapha, MD: There are many atherectomy devices out there. How do you derive the value of each device, and when and where do you choose to use each device?

Thomas M. Shimshak, MD: There is a growing understanding of the value of atherectomy for complex de novo disease, as well as for in-stent restenosis. I believe vessel preparation, plaque modification, and calcium removal prior to drug-coated balloon and/or stenting, can improve early and long-term results. In selecting one device over another, I rely not only on angiographic findings, but also intravascular ultrasound (IVUS) data. Compared to fluoroscopy and angiography, IVUS more accurately characterizes plaque burden, vessel size, and the presence and extent of superficial calcium. The use of IVUS-based virtual histology provides additional information regarding plaque composition, including soft, firm tissue, thrombus, and calcium. 

Each currently available atherectomy device has unique performance attributes. The choice of one device over another is based on operator experience and specific device features, and then selecting the appropriate device based on angiographic and IVUS findings. Soft plaque with or without thrombus can be safely approached with laser, excisional, or rotational atherectomy with dynamic aspiration. Orbital, excisional, and rotational atherectomy with dynamic aspiration performs safely and effectively in more heavily calcified lesions. Currently, in the United States, laser atherectomy is approved for use in in-stent restenosis, and rotational atherectomy with dynamic aspiration is being evaluated in an ongoing clinical trial.  

The infra-popliteal circulation presents additional complex anatomic features, including long segments of heavily calcified disease. Orbital, laser and rotational atherectomy (with or without dynamic aspiration) have all been effective and safe below the knee.

Dr. Mustapha: Many chronic total occlusions (CTOs) tend to have layers of fibrin, thrombus, calcium, and cholesterol. When you combine all that together, you are pretty much dealing with ossification or near-ossification of the plaque. How do you approach crossing CTOs? What is your method of escalating aggressiveness until you cross?

Dr. Shimshak: My approach to crossing CTOs has changed significantly over the past few years. Prior to the introduction of dedicated CTO wires and crossing devices, we relied on .035-inch hydrophilic guidewires and low profile support catheters. The evolution of more refined crossing wires, catheters, and techniques in the peripheral circulation parallels the advances in wire technology and techniques for crossing coronary CTOs. 
I like to break down the crossing of CTOs into 3 phases, including 1) penetrating the proximal cap, 2) negotiating the body of the CTO, and 3) crossing the distal cap.  

First, I like to use high magnification to identify any subtleties of the proximal cap, looking for a small micro channel(s). I begin using a dedicated .014- or .018-inch CTO wire (12-30 gram weight tip) with a small bend, supported by a low profile catheter (usually 4 French [Fr] angled catheter). I try to penetrate the cap with the tip in an opened configuration and then advance the system as far as possible in this configuration. If the catheter fails to cross the proximal cap, I would downsize the support catheter, sometimes even using a low profile balloon catheter to begin the recanalization. Once the wire fails to advance further into the proximal portion of the CTO, I would exchange for an .014- or .018-inch hydrophilic wire, and then begin to prolapse the wire through the occlusion, supported by a low profile catheter.  

If the .014- or .018-inch CTO wire(s) or hydrophilic wires fail to advance within the body of the CTO, I would then upsize to an .035-inch hydrophilic wire with a 4 Fr support catheter. This is typically a very effective and efficient strategy for negotiating longer CTOs.

I do not routinely perform repeated contrast injections as I am negotiating the long CTO. Instead, I rely on fluoroscopy with multiple views. Once the distal cap is approached, contrast injections with multiple oblique views are important to define the course of the recanalization, as well as the distal landing zone. I try to cross the distal cap first with either an .014- or .018-inch CTO or hydrophilic wire, and only use an .035-inch wire if these fail to cross. 

Advances in wires and crossing techniques have led to crossing success rates even for long CTOs of >95%. The use of dedicated CTO devices including Crosser (Bard Peripheral Vascular), Wingman (Reflow Medical), Truepath (Boston Scientific), and Outback (Cordis, a Cardinal Health Company) can further improve crossing success rates. In addition to be successful in crossing the CTOs, these techniques contribute to intraluminal crossing, which facilitates use of atherectomy devices. 

Dr. Mustapha: After crossing a tight, very hard CTO cap and trying unsuccessfully to advance the balloon to dilate, what are some tips and tricks to get through such a difficult scenario without compromising the integrity of the vessel?

Dr. Shimshak: This is probably one of the most frustrating scenarios encountered when negotiating a long CTO. There are a few strategies that can be used to solve this problem. First, consider decreasing the profile of the wire and support catheter. Small differences in wire and/or profile can significantly impact your success in crossing this portion of the CTO. Consider using a .014- or .018-inch wire and balloon catheter. Frequently, I will exchange for a .014-inch wire and use a very small profile, undersized high-pressure coronary balloon to push through and dilate this portion of the occlusion. This is generally very effective in overcoming these difficult segments of the CTO and allows for continuation of conventional crossing techniques through the remainder of the CTO. The use of newer crossing devices, like the Wingman, can increase crossing through these resistant segments. 

Finally, it may be necessary to reassess the position of the wire and consider recrossing in another tissue plane.

Improving pushability of the system is also an important solution to be considered. Ineffective “push” through a CTO typically occurs with long CTOs with excessive calcification, especially when approaching the distal superficial femoral artery (SFA) CTO with contralateral access. In this situation, consider either an antegrade approach to improve pushability or retrograde access to complete the recanalization. This may necessitate a staged procedure. 

Dr. Mustapha: Many have described long CTOs to be theoretically hibernating lumens with and without dormant thrombus and/or intermittent non-occlusive plaque. In these types of lesions, which device would you chose to treat both the presence of thrombus and calcified plaque?

Dr. Shimshak: I agree completely with this observation. Long CTOs are complex with mixed morphologies, including soft, firm, concentric, eccentric plaque with or without associated thrombus, and superficial and deep calcification. The arteriogram will not allow accurate assessment of these features. Intravascular ultrasound is a very effective and quick way to assess the complexity of the CTO and then select the most appropriate atherectomy device. I prefer Jetstream atherectomy (Boston Scientific) for these complex CTOs because of its ability to effectively and safely treat all plaque morphologies. This device is approved as both an atheretomy and thrombectomy device. It has proven efficacy in removing calcium and improving lumen cross-sectional area. The range of available catheter sizes and the feature of expandable cutters allows treatment of the common femoral, SFA-popliteal, and infra-popliteal segments. 

Dr. Mustapha: You are faced with a long CTO, up to 400 mm in the superficial femoral artery/popliteal region. After crossing the proximal CTO cap, you are at the distal CTO cap. Would it be reasonable to treat the 400 mm segment that you crossed to ensure removal of all the dormant thrombus and calcified plaque, then proceed with crossing the distal cap? 

Dr. Shimshak: This is an interesting technique for debulking long CTOs that has been used effectively by some Jetstream operators. Basically, “preserving” the distal cap occlusion until the end and treating the more proximal disease first, theoretically creates a “physiologic” filter. Particulate material generated by the atherectomy device is prevented from distal embolization by virtue of the preserved distal cap.  

The risk of distal embolization exists with any atherectomy device. Although clinical trial data would suggest the risk is low (<2% in the initial Jetstream trial), it does increase with long, complex CTOs and for in-stent occlusions/stenoses. The clinical consequences of distal emboli are quite varied, ranging from non-consequential to catastrophic, especially in the critical limb ischemia (CLI) patient with diffuse infra-popliteal disease. 

I have adopted a different technique for using Jetstream atherectomy in long CTOs. I prefer to cross the entire CTO using the techniques and wires previously discussed. Following recanalization, I prefer to pre-dilate the entire length of the CTO using a low profile 2.0 mm or 2.5 mm balloon catheter. I then exchange for a 300 cm, .014-inch non-hydrophilic wire (Jetwire [Boston Scientific] or Barewire [Abbott Vascular]). This is followed by an IVUS interrogation of the entire CTO. Pre-dilation with an undersized balloon allows easy passage of the IVUS system. I am able to understand the pathology of the CTO process, wire position (i.e., intraluminal), lesion composition and appropriateness of atherectomy, as well as atherectomy device selection. If use of distal protection is desired, it can be safely and easily deployed by virtue of the pre-dilation. More importantly, though, the creation of a small micro-channel post recanalization improves the efficiency of the initial pass of the Jetstream device, maintains revolutions per minutes (RPMs), avoids stalling, improves aspiration, and reduces the risk of embolization. For very long CTOs with extensive calcification, I believe the risk of distal embolization can also be reduced by integrating a “step approach” with cutter sizes, much like the technique used for Rotablator (Boston Scientific) in the coronary circulation. I will start with a 1.6 or 1.85 mm cutter for very complex CTOs, and make a 1 or 2 passes encompassing the entire CTO. I then reassess the treated segment with a follow-up angiogram and then typically progress to the 2.1/3.0 mm catheter. 

Using these techniques, coupled with very slow “to-and-fro” advancement of the cutter, will greatly reduce the risk of distal embolization, even for very long CTOs. 

Dr. Mustapha: When you cross the distal cap after performing the above-discussed method of clearing long CTO segment, do you prefer to use embolic protection devices with a severely calcified CTO cap? If so, which type do you prefer and where do you position it? Especially if your reconstitution is just above the trifurcation of the tibial arteries.

Dr. Shimshak: As a rule of thumb, I would consider distal embolic protection (DEP) routinely for very long complex, calcified, stenotic lesions or CTOs, especially in high risk patients (CLI, diffuse distal disease). If more aggressive debulking is planned (as opposed to simple plaque modification), I would also consider using DEP. I prefer the Emboshield (4-7 mm) filter for the Jetstream device. It has excellent capture efficiency and capacity and the Barewire is very compatible with the Jetstream device. I try to position the filter in the P2 or P3 segment, and am attentive to its position before each atherectomy run and during catheter exchanges. If more aggressive debulking is performed, it is important to assess the filter to determine if it has reached its capture capacity. It may be necessary to remove it and reinsert a new filter if the initial filter is filled.  
If the filter distal landing zone is in close proximity to the trifurcation, I would still place the filter in the P2 or P3 segment, complete the atherectomy to the P1 or P2 level, and treat the continuing, more distal segments after the filter has been removed.

Dr. Mustapha: So far, we have described an extremely complex CTO with severely calcified lesions that would require balloons with the ability to overcome the resistance coming from the aforementioned pathology. Which balloons do you have in mind that can overcome such resistance and why?  

Dr. Shimshak: There is no question that plaque modification and calcium removal with atherectomy facilitates balloon angioplasty, reduces inflation pressure requirements, and associated balloon-induced injury and dissection. I would first consider appropriate atherectomy of such a resistant lesion, supplemented by IVUS. Small changes in plaque composition and calcium removal greatly improve the response of the lesion to balloon angioplasty. Typically, lower balloon inflation pressures are required after successful atherectomy. Undersized, non-compliant, high-pressure balloons can be used for very resistant lesions. Focal force balloons or cutting balloons are also very effective for resistant lesions. 

Dr. Mustapha: Next, how do you approach the treatment of this pathology? Do you start with a lower profile balloon and escalate up to the final target balloon or do you start with the target balloon? 

Dr. Shimshak: I tend to use slightly undersized balloons to predilate complex lesions, especially if there is excessive calcification. This strategy minimizes angioplasty-induced dissections and/or perforations. It also allows for lower pressure inflations with the definitively sized balloon, whether plain old balloon angioplasty or drug-coated balloon (POBA or DCB). 

Dr. Mustapha: You just finished treating the 400 mm CTO segment and you have the option of a drug-coated balloon (DCB), with data showing reasonable one-year patency rates between high 80s and low 90s, and a drug-eluting stent (DES) with a patency rate at one year of 94%. Which one would you chose if available to you and why that choice specifically in this severely complex, calcified, long CTO?

Dr. Shimshak: This is always the fundamental question following successful recanalization and vessel preparation for long (and very long) “real-world” CTOs.  Clearly, significant, flow-limiting dissections should be stented either with bare metal nitinol or drug-eluting stents. I prefer helical stent designs (Supera) for more distal disease, and when the mid and distal popliteal segments are involved. I prefer a more precise positioning nitinol stents for very proximal SFA disease, to minimize Supera stent elongation across the profunda and extending into the common femoral artery. 

In the absence of dissections, the fundamental question is whether DCB or contemporary stenting results in better long-term outcomes. The short answer is we don’t know. However, based on subset analysis of DEFINITIVE AR and recent registry data, combining atherectomy with subsequent DCB appears to improve procedural success and long-term patency. I believe this is related not only to calcium removal, but also plaque modification and removal.  

We tend to rely on a single angiographic view to determine our therapeutic endpoint. While angiography is valuable, I typically supplement it with IVUS evaluation of the entire treated segment. Based on IVUS data, if there is no significant residual disease and the lumen cross-sectional area is adequate, I would consider using DCB. However, if there is excessive plaque burden and significant compromise to the lumen cross-sectional area, I tend to stent these areas. In my practice, the latter situation is the more typical scenario. The net result, however, is that shorter stent lengths are used because of atherectomy and vessel preparation. I also feel it is essential to assess the proximal and distal cap segments post atherectomy and angioplasty to determine the extent of residual disease. This is often the site of restenosis and/or occlusion if left unstented.

Disclosure: Dr. Thomas Shimshak reports he is a consultant and speaker for Abbott Vascular, Boston Scientific, and Philips Volcano; received physician training programs support and clinical research from Boston Scientific; and is a member of the Medical Advisory Board for Boston Scientific. 

Dr. J.A. Mustapha can be contacted at jihad.mustapha@metrogr.org.
Dr. Thomas Shimshak can be contacted at tshimshak@gmail.com

Case Illustration
By Thomas M. Shimshak, MD

This is a 55-year-old man with severe, lifestyle-limiting claudication. Selective femoral arteriography with contralateral access demonstrated a long chronic total occlusion (CTO) of the distal superficial femoral artery (SFA) and proximal popliteal segment. This was successfully recanalized with .014-inch and .018-inch 12-30 gm Victory (Boston Scientific) CTO wires and low-profile support catheter. Following recanalization, balloon angioplasty was performed with a long 2.5 mm balloon catheter. The CTO wire was exchanged for a 300 cm bare wire and a 4-7 mm Emboshield (Abbott Vascular) was deployed. Intravascular ultrasound evaluation demonstrated 1) intraluminal position of the guidewire; 2) extreme superficial calcification; 3) severe residual obstructive disease.

Jetstream atherectomy (Boston Scientific) was used, incorporating 1.85, 2.1, and 3.0 mm cutters. Two passes with each device were performed, followed by balloon angioplasty with 7 mm balloon catheter and ultimate deployment of a 6.5 mm Supera self-expanding stent (Abbott Vascular) with wide patency.