Can't See the Forest for the Trees: Transcollateral Crossing of Chronic Total Occlusions

Abstract

Chronic Total Occlusions (CTOs) remain a significant clinical challenge in the treatment of peripheral artery disease. Successful treatment of CTOs is largely dependent on the skill level, patience, and experience of the interventionalist and is associated with a success rate between 34% and 91%. A transcollateral approach can be taken to cross and treat complex lesions that are untreatable using traditional techniques. This paper is focused on the techniques and tools required for successfully using the transcollateral approach to cross CTOs in the peripheral artery tree. 

VASCULAR DISEASE MANAGEMENT 2015;12(6):E109-E113

Key words: transcollateral, chronic total occlusions, peripheral artery disease

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Peripheral artery disease (PAD) affects 8 million to 12 million Americans. Of the population over the age of 65, 12% to 20% is at risk of developing symptomatic peripheral arterial insufficiency.¹ Chronic total occlusions (CTOs) in the peripheral artery tree are common; nearly 40% of PAD cases have CTOs.² Percutaneous endovascular intervention has emerged as the preferred method to restore blood flow to alleviate symptoms of PAD. However, endovascular treatment of CTOs is challenging due to the lack of tools for crossing and treating, time commitment, and skill level. In fact, treatment of CTOs has a success rate ranging between 34% and 91%. The interventionalist may utilize various approaches to successfully cross the CTO in order to treat the lesion. An antegrade approach is the traditional method of crossing a CTO. However, traditional techniques to recanalize the vessel fail in 20% of all cases.³ Using a different approach such as the retrograde and/or transcollateral technique may allow the interventionalist to treat complex lesions that are untreatable by traditional techniques. This paper will focus on the utilization of transcollaterals to cross infrainguinal CTOs. 

Collateral Arteries

Peripheral arterial collaterals develop to shunt blood around a chronic total occlusion, first described by Longland in 1953.⁴ Commonly recognized, infrainguinal collateral vessels are paired with their respective main vessel occlusion (profunda collateral andsuperficial femoral artery [SFA] occlusion; geniculate collateral and popliteal occlusion; peroneal collateral and tibial occlusion; plantar loop collateral and dorsalis pedis or plantar occlusion) (Figures 1-4). These collaterals serve to provide the metabolic nutrients to the distal vasculature. However, when these collaterals do not fulfill the needs of the distal vasculature, symptoms develop in the form of claudication and at its worst critical limb ischemia.⁵ If symptoms develop, opening the chronic total occlusion is warranted to provide in-line blood flow. Many times an antegrade approach is unsuccessful and the operator will consider other avenues to cross the lesion.^6,7 A transcollateral approach is an exotic technique that can be used to treat occlusions regardless of their location in the peripheral arterial tree without having to gain a second access point. 

Treating CTOs Using a Transcollateral Approach

When the antegrade approach fails in crossing a CTO, a transcollateral approach may be considered. Angiographically, multiple angulated views are obtained to delineate the exact course of the collateral artery considering its many branches and tortuosity. The collateral vessel is initially treated with vasodilators, considering its tapering size (many times less than 1 mm) and to reduce vasospasm.⁸ Additionally, the patient is anticoagulated with heparin with a goal activated clotting time ≥250. A floppy tipped 300 cm hydrophilic wire is then advanced through the collateral artery and positioned such that the tip of the wire is at the distal cap of the CTO and is facing in a retrograde fashion. A 0.014˝/0.018˝ 150 cm crossing catheter is inserted over the wire and advanced to the distal cap. The floppy tipped wire is then exchanged for a 0.014˝/0.018˝ CTO wire, which is used to cross the occlusion. Longer length wires, and long-shaft percutaneous transluminal angioplasty (PTA) balloons are preferred when treating from the transcollateral approach. The paucity of long, and low profile interventional tools place a significant limitation in treating CTOs from a transcollateral approach when the access point is far from collateral and the patient is tall.

Retrograde Wire Enters True Lumen

If the CTO wire is able to successfully cross the occlusion and remain in true lumen, crossing should be followed up with PTA to treat the occlusion and recanalize the vessel. This is shown in a patient whose chronic total occlusion extends from the tibioperoneal trunk into the proximal posterior tibial artery (Figure 2). An antegrade approach is attempted to cross the lesion but the chronic total occlusion wire enters a subintimal plane jeopardizing the ostium of the anterior tibial artery. Therefore, a transcollateral approach is attempted through a tortuous geniculate artery which starts in the mid popliteal and extends to the proximal posterior tibial. The collateral is successfully traversed with a long, floppy, hydrophilic wire supported by a low-profile crossing catheter. The benign wire is switched for an 18g CTO wire and successfully crossed into the true lumen. Balloon angioplasty is then performed through the collateral with a low profile balloon successfully recanalizing the tibial-peroneal trunk and posterior tibial artery. 

If the collateral is too small and/or tortuous to advance a balloon, then a wrapping wire technique should be performed. (Figure 1C) This is illustrated in a patient with a CTO of the SFA and a transcollateral approach through the profunda artery is performed. The collateral is too small to advance a balloon, therefore a second wire is placed in an antegrade fashion. The antegrade wire uses the retrograde wire as a guide. Wires have a natural affinity for each other, and as such the antegrade wire wraps the retrograde wire, advancing until the antegrade wire successfully crosses the CTO. Then treatment can be performed in an antegrade fashion as illustrated in Figure 1, recanalizing the SFA. 

Antegrade and Retrograde Wires Enter Subintimal Planes

If the antegrade wire followed by the retrograde transcollateral wire enters two different subintimal planes, a double balloon technique can be used to fenestrate the two lumens of the vessel (Figure 5). To do this, both antegrade and retrograde wires are advanced using multiple angiographic views to ensure that the wires are no more 2-3 mm apart.⁹ PTA balloons are advanced over each wire, abutting the tips of the balloons. Both balloons are inflated simultaneously, successfully fenestrating the lumen at the tips of the balloon.¹⁰ The antegrade wire is then advanced into the retrograde channel and distally into true lumen. The retrograde equipment is then removed and the vessel is treated from an antegrade fashion. 

Tools Required to Treat CTOs

Utilizing the transcollateral approach to treat CTOs requires specialized tools that are capable of being deployed in smaller vessels while being able to provide support as the interventionalist maneuvers through the collateral channels and re-enters the native vessel. Longer length, flexible interventional tools are required to successfully cross and treat CTOs using the transcollateral approach. Floppy tipped, strong-bodied wires and low-profile support catheters are desirable when using the transcollateral approach. In addition, stiff-tipped, polymer-coated CTO wires are preferable when crossing CTOs. Treating CTOs using this approach requires flexible PTA balloons that are low profile with long shaft lengths. Development of new interventional tools that are designed to be used for transcollateral crossing will give interventionalists a wider array of tools to choose from thereby enhancing the chances of success. 

Conclusion

Treatment of CTOs is a critical challenge, and advanced techniques such as transcollateral crossing may enhance the chances of successful recanalization. Utilizing the transcollateral approach may allow clinicians to cross and treat lesions that are untreatable by traditional approaches and thereby improve patient outcomes. Few interventional tools exist that can be successfully used in conjunction with a transcollateral approach. Development of new tools can enhance techniques available to interventionalists. Clinicians need to invest time to gain the appropriate training to successfully use advanced techniques and add transcollateral crossing of CTOs to their arsenal of techniques to cross CTOs. 

Editor’s note: Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no disclosures related to the content herein.

Manuscript received January 22, 2015; manuscript accepted March 10, 2015. 

Address for correspondence: George L. Adams, MD, Rex Healthcare, 300 Health Park Drive, Suite 110, Garner, NC 27529 United States. Email: adamsgla@hotmail.com.

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