Blunt Microdissection and Rotational Atherectomy: An Effective Combination for the Resistant Chronic Total Occlusion

Reported success rates of percutaneous coronary interventions (PCI) of chronic total occlusions (CTO) range from approximately 60–75%,^1–3 and are much lower when compared with PCI of nontotal occlusions.4,5 When combined with specialized equipment, some reports have stated slightly higher success rates.6,7 The most common reasons for procedural failure include the inability of the guidewire to cross the occlusion (80–90%), the inability of the balloon to cross the occlusion (2–15%), and the inability to adequately dilate the lesion (2–5%).^7,8,9 In the latter two categories of failure, rotational coronary atherectomy can be helpful in improving procedural success rates.^10,11 Use of the Rotablator^® rotational atherectomy device (Boston Scientific Corp., Natick, Massachusetts), however, can be limited by recrossing the occlusion with a relatively delicate and less maneuverable 0.009 inch stainless steel RotaWire™ (Boston Scientific). In the circumstance of a resistant CTO, where rotational atherectomy is the only available option, recrossing the occlusion with a less favorable guidewire poses an obstacle. Such a clinical conundrum is encountered in the present case report. The additional use of the Frontrunner™ blunt microdissection catheter (LuMend, Inc., Redwood City, California) allowed for successful recrossing of a resistant CTO with the RotaWire, which led to the ultimate successful PCI result. The challenge of percutaneous revascularization of CTOs requires innovative approaches. This case highlights the effectiveness of combined techniques and devices; other novel approaches are also discussed. Case Report A 68-year-old male who had a history of multiple coronary risk factors including hypertension, diabetes mellitus and dyslipidemia, presented with a non-ST-segment elevation myocardial infarction (NSTEMI). A diagnostic coronary angiogram was performed demonstrating only mild-to-moderate disease in the circumflex and right coronary arteries. The middle left anterior descending artery (LAD) segment, however, had significant proximal disease followed by a 100% chronic occlusion in the middle segment (Figure 1). Distally, the LAD received collateral circulation from the circumflex artery (Figure 2). A 7 Fr CLS 3.5 guide was used for support in the initial attempt to treat the LAD CTO. With added balloon catheter support, wire-probing was performed with multiple coronary guidewires, and the PT Graphix™ (Boston Scientific) was successful in crossing the occlusion (Figure 3). The lesion, however, could not be crossed with multiple 1.5 mm balloon catheters (monorail and over-the-wire systems), including the Maverick2™ (Boston Scientific) and the Voyager™ (Guidant Corp., Indianapolis, Indiana). Plaque modification was deemed necessary at this juncture. However, an attempt to rewire the occlusion with the RotaWire was unsuccessful. The procedure was aborted. The patient declined surgery and was medically managed. Approximately 2 months later, the patient presented with another NSTEMI. A repeat coronary angiogram demonstrated similar findings, with a CTO in the middle segment of the LAD. Guide support was increased with an EBU 4.0 mm catheter, and the occlusion was crossed with an Asahi Miracle Bros 3 gram wire (Abbott Vascular Devices, Redwood City, California). Despite improved guide support, none of the 1.5 mm balloons, including the Maverick2, Voyager™ monorail or over-the-wire systems were able to cross the lesion. A Pilot™ 150 (Guidant) “buddy wire” was placed in a side branch proximal to the occlusion, but did not help with the balloon advancement. An attempt to cross the occlusion with the buddy wire was unsuccessful. Again, rotational atherectomy was deemed as a necessary step toward a successful procedural outcome. Recrossing the CTO with the less maneuverable RotaWire, however, was a major concern. The Asahi Miracle Bros wire was exchanged for a 0.009 inch Extra Support RotaWire to the lesion site; however, the RotaWire was unable to recross the occlusion as in the previous attempt, despite improve guide support. Blunt microdissection was performed using the Frontrunner catheter without complete penetration of the CTO (Figure 4). Microdissection of the plaque at the entrance of the CTO, however, allowed for successful crossing of the occlusion with the RotaWire (Figure 5). Rotational atherectomy was performed with a 1.25 mm burr. The lesion was further pretreated with a1.5 mm and a 2.5 mm Maverick2™ balloon. Stent deployment was performed using multiple Taxus™Express2™ drug-eluting stents (Boston Scientific) from the proximal-to-middle segments of the LAD. Post-dilatation was performed using a NC Monorail™ balloon (Boston Scientific), achieving to a final diameter of 3.42 mm, based on the balloon compliance chart (Figure 6). The patient did well clinically and was discharged from the hospital. Discussion The present case of PCI of a CTO demonstrated a technical challenge when the balloon failed to cross the lesion after successful passage of the coronary guidewire. The LAD CTO was complicated by prior proximal disease from both clinical and technical standpoints. The proximal disease may have played a role in the patient’s clinical syndrome, since it provided inlet for a moderate-size diagonal branch. It was also unknown whether there was sufficient collateral circulation to the distal LAD. Prior to noninvasive risk stratification, the recurrence of NSTEMI suggested that initial PCI of this segment into the diagonal branch could have been an alternative approach. Significant disease in the proximal LAD also served as a mechanical hindrance to the passage of interventional devices. Friction with the balloon catheter generated in this segment can lessen the transmitted forces to the balloon tip, thereby decreasing its pushability. Nonetheless, PCI of the CTO was successful. Evidence of the clinical benefits to successful PCI of CTOs is apparent,^2,12,13 and underscores the importance of achieving successful procedural outcomes. When PCI of CTOs fails due to unsuccessful crossing of the balloon catheter, combination use of the Frontrunner and the Rotablator devices should be considered. The Frontrunner catheter is designed to create blunt microdissections inside the plaque to allow for passage of a guidewire through the lesion.^14,15 In this case, the extended application of the Frontrunner is to increase the crossability of any guidewires, including difficult-to-maneuver wires such as the RotaWire. This is a crucial step for the necessary plaque modification that ultimately results in a successful PCI. Other technical options to consider when confronted with failure to balloon-cross may include: increasing guide support, placement of a buddy wire into a proximal branch, placement of a buddy wire through the occlusion into the distal vessel, or the use of an excimer laser.^9,16 In the presented case, all of these strategies were explored to no avail; a more supportive guide and a proximal buddy wire did not help the balloon catheter to cross. The buddy wire, in this case, could not be advanced parallel to the first wire to cross the occlusion. The excimer laser and rotational atherectomy are usually the devices of choice when the lesions cannot be crossed with a balloon or cannot be dilated. In general, rotational atherectomy has a higher procedural success rate than laser angioplasty.¹⁷ As is the case in many catheterization laboratories, the excimer laser was not available to us. Other equipment and device innovations in PCI of CTOs include the newer, specialized CTO wires with or without taper tips or hydrophilic coating.⁹ In this case, two of these wires were used with successful crossing of the occlusions: the hydrophilic PT Graphix and the Asahi Miracle Bros 3 gram wire. Along with the Frontrunner, the SafeCross^®-RF guidewire (IntraLuminal Therapeutics, Inc., Carlsbad, California) is the other FDA-approved device for the treatment of refractory CTO recanalization. This device utilizes infrared optical coherence reflectometry at the wire tip to guide crossing of the occlusion.^18,19 The Asahi Tornus^® is the latest FDA-approved device for treatment of CTOs. The manual rotation of the over-the-wire catheter is designed to penetrate severe or total occlusions after successful wire crossing.²⁰ It is a promising technology for the presented scenario, however, its formal approval and availability came after this case. The fixed wire-balloon system, also known as balloon-on-a-wire, was another novel technology designed to facilitate the crossing of guidewire and balloon dilatation using a probing catheter. It was attractive due to its extremely low profile,^8,21,22 however, the relative lack of pushability, trackability and steerability diminished its popularity and production.⁸ Other investigational approaches include drug infusion therapy with fibrinolytic agents²³ and collagenase,²⁴ and mechanical vibrational angioplasty.²⁵ Recanalization of CTOs requires innovative approaches. This case study suggests the appropriate combination use of currently available devices that can help to increase the procedural success rate of treating CTOs.

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