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Choosing the Ideal Treatment Strategy for CTO in Patients With PAD
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Chronic total occlusion is observed in approximately 40% to 50% of patients with symptomatic peripheral artery disease. Successfully crossing the CTO with a guidewire can be challenging due to a resistant fibrous cap, severe calcification, long length and subintimal wire passage with unsuccessful re-entry. Failure to cross a CTO with a guidewire or to re-enter the true lumen beyond the CTO can lead to the need for amputation in patients with critical limb ischemia or bypass surgery.
Figure 1. Long CTO starting near the ostium of the left superficial femoral artery (SFA) in an 85-year-old male with severe lifestyle-limiting claudication refractory to exercise regimen and cilostazol.
Figure 2. A guidewire (Glidewire, Terumo) with the support of a glide catheter was carefully advanced through the CTO while attempting to stay in the true lumen. Contrast injection shows collaterals from the profunda femoris artery with reconstitution of the distal SFA.
Images provided by Michael S. Lee, MD, FACC, FSCAI; printed with permission.
Choosing the Access Site
One of the most important decisions the operator must make for successful CTO recanalization is choosing the appropriate vascular access site. Vascular access can be obtained from the contralateral or ipsilateral side of the lesion. Contralateral access may be more convenient for the operator, whereas antegrade access may enhance the ability to advance catheters.
The antegrade approach is more commonly used because of operator convenience. However, if the guidewire does not cross the CTO, the retrograde approach offers an alternative strategy because penetration of the distal cap is usually easier to traverse than the proximal cap. Retrograde tibial or pedal access can be used to cross the distal cap in the infrapopliteal vessel to externalize the wire at the proximal vascular access site. Ultrasound guidance to obtain tibial or pedal access is particularly useful given the technical difficulty of obtaining vascular access due to the small vessel diameter. Retrograde access through the distal superficial femoral or popliteal artery is less commonly performed but can be performed for CTO in the common femoral or superficial femoral artery.
If wiring from the antegrade and retrograde approach is unsuccessful, the SAFARI (subintimal arterial flossing with antegrade-retrograde intervention) technique is useful for subintimal recanalization.
Wire-Based Strategies
An initial strategy of wire escalation with 0.014”, 0.018” or 0.035” wires with a support catheter can be tried to cross the CTO (Figures 1 to 4).
If unsuccessful, the Bolia technique can be used. A 0.035” hydrophilic guidewire (Glidewire, Terumo) is buckled to create a small loop at the tip of an angled or straight support catheter and advanced into the subintimal plane, beyond the distal cap and adjacent to the reconstitution site. If an initial strategy of wire escalation is unsuccessful in re-entering the true lumen, a viable option includes the use of a re-entry catheter.
Re-entry catheters are effective for advancing the guidewire from the subintimal space and puncturing back into the true lumen. The Outback catheter (Cordis) is advanced over a 0.014” wire. Using simple orthogonally oriented radiopaque markings to direct a re-entry needle toward the true lumen under fluoroscopic guidance, the “L” and “T” helps orient the re-entry cannula toward the true lumen under fluoroscopy. A 22-gauge nitinolol cannula deploys into the true lumen, followed by wire passage. The needle is retracted and device removed. After balloon dilatation, stenting can be performed if indicated. The Pioneer catheter (Volcano Corp.) is another re-entry catheter that is advanced over a 0.014” wire. The catheter is advanced subintimally, beyond the distal cap and adjacent to the site of reconstitution. With IVUS guidance to orientate the re-entry cannula toward the true lumen, a nitinol needle is deployed into the true lumen, allowing the wire to safely enter the true lumen.
The Viance crossing catheter (Covidien/Medtronic) is another guidewire-based device to cross the CTO via the true lumen. The operator spins the device to transfer torque while advancing the catheter. If the device tracks into the subintimal space, the Enteer re-entry system (Medtronic) enables the operator to target the true lumen due to the catheter’s unique flat shape, which self-orients in the subintimal space.
Catheter-Based Crossing Strategies
Devices designed to cross the CTO while remaining in the true lumen include crossing catheters, laser atherectomy and blunt dissection catheters.
The Crosser catheter (FlowCardia Inc.) utilizes low-amplitude, high-velocity microvibrations (20,000 cycles per second to a depth of 20 µm) to pulverize the CTO to create a channel. The catheter is advanced over a 0.014” wire and designed to remain selectively intraluminal as the elastic arterial wall is resistant to the vibration. The Crosser is relatively easy to use with success rates ranging from 64% to 75%.
The Ocelot system (Avinger Inc.) utilizes OCT to help direct a rotating catheter tip to traverse the CTO while remaining inside the true lumen.
The excimer laser (Spectranetics) can be used to cross the CTO with a step-by-step technique. Bursts of forward-firing UV energy can ablate plaque with shallow tissue penetration, facilitating wire passage into the true lumen.
Figures 4A and 4B. Final angiography reveals restoration of straight in-line flow in the SFA after implantation of two long nitinol self-expanding stents.
The Frontrunner XP CTO catheter (Cordis) enables controlled crossing of CTO by using blunt microdissection to create a channel through the CTO to facilitate wire placement. It is designed to maintain the guidewire in the center of the lumen and penetrate the plaque in a controlled fashion. However, if the device tracks subintimally, a re-entry catheter may be needed to regain access into the true lumen. The device is uncommonly used, given its difficulty to use, long procedural time, low success rates and contraindication in infrapopliteal vessels due to its size.
‘Go-To’ Techniques
Successful CTO recanalization, particularly if the lesion is heavily calcified or long, can be technically challenging. If an initial strategy of wire escalation is unsuccessful, a variety of strategies and technology are available to facilitate recanalization. However, no device has distinguished itself as the ideal treatment strategy for all lesions due to the heterogeneity of patients and lesion types, as well as nonrandomized study designs with small sample sizes. Although it is not possible to master all the techniques and devices, a commitment to learning several “go-to” techniques and devices can lead to successful recanalization of complex CTOs.
- References:
- Bolia A, et al. Clin Radiol. 1989;40:325.
- Norgren L, et al. J Vasc Surg. 2007;doi:10.1016/j.jvs.2006.12.037.
- For more information:
- Michael S. Lee, MD, FACC, FSCAI, is an interventional cardiologist and associate professor of medicine at UCLA Medical Center. He can be reached at 100 Medical Plaza, Suite 360, Los Angeles, CA 90095; email: mslee@mednet.ucla.edu.
Disclosure: Lee reports receiving speaker’s honoraria/consultant fees from Cardiovascular Systems Inc.