Chronic total occlusions (CTO) represent some of the most challenging scenarios for percutaneous coronary interventions (PCI). Predictors of procedural success in PCIs of CTOs include length of occlusion, duration of occlusion, presence of tapered entry configuration, bridging collaterals and calcification.1–3 CTO in the form of in-stent restenosis, however, may represent an added advantage to PCI in that the additional “road map” and “vessel protection” provided by the existing stent are present. The stent “skeleton” can serve as a guide to visualization of the vessel’s anatomic course and may provide some added protection against vessel trauma/perforation. Two cases of successful PCI of long in-stent restenosis CTOs are presented with the use of the Frontrunner® (LuMend, Inc., Redwood City, California) blunt microdissection device: a native right coronary and a coronary bypass in-stent restenosis lesion. To date, these represent some of the first reported cases of the treatment of in-stent restenosis coronary CTOs using the intraluminal blunt dissection catheter and the first of such in a coronary artery bypass graft.4,5 The successful results should encourage more frequent attempts of treating these otherwise difficult lesions. Case Report #1. The first case involves a 68-year-old female with a history of inferior wall myocardial infarction and stent placement in the middle-to-distal RCA. The stented segment was long, consisting of one 2.5 x 13 mm Multi-Linnk Tristar™ stent (Guidant Corporation, Indianapolis, Indiana), followed by a 2.5 x 28 mm Multi-Link Tristar™ stent. The final stent diameter was 2.6 mm after postdilatation. Three years later, the patient returned with recurrent chest pain, and a coronary angiogram demonstrated a long occlusion of the RCA at the stent site. Attempt to perform PCI on this occlusion failed due to the inability to cross the lesion with guidewires, including the BMW (Guidant) and PT Graphix™ (Boston Scientific Corporation, Natick, Massachusetts). The patient was medically managed until one year later, when she returned due to debilitating chest pain. A repeat angiogram was performed. The LAD and LCX were unchanged and had insignificant coronary artery disease. The RCA had a long CTO in the form of in-stent restenosis of the entire stented segment (Figure 1A). An 8 French (Fr) AR1 guiding catheter was chosen for support. An attempt to cross the lesion with coronary guidewires, including the Asahi Prowater and the Asahi Confianza (Abbott Vascular Devices, Redwood City, California), was unsuccessful, with only approximately 10 mm of penetration into the occlusion.The guidewires were difficult to torque in an attempt to keep them in the central lumen in the relatively firm restenotic lesion; the wire tips could not be manipulated away from abutting the stent struts. The total dwell time of the wire was approximately 30 minutes. The guidewire was exchanged for the Frontrunner catheter and blunt microdissection was performed throughout the entire length of the occlusion without difficulty, and took approximately 7 minutes (Figure 1B). The lesion was re-wired with the ChoICE® PT guidewire (Boston Scientific) (Figure 1C). Predilatation was performed using a 1.5 x 20 mm Maverick® (Boston Scientific), a 2.5 x 20 mm Maverick 2™ (Boston Scientific), and followed by a 2.75 x 6 mm Cutting Balloon™ (Boston Scientific). The entire lesion was restented with Taxus® Express2™ stents (Boston Scientific – from distal to proximal including the proximal diseased segment not previously stented) 2.5 x 24 mm, 2.75 x 32 mm, and 2.75 x 20 mm. Postdilatation with a Quantum™ Maverick™ balloon was achieved with an estimated final diameter of 3.18 mm based on the balloon compliance chart (Figure 1D). Case Report #2. A 63-year-old male underwent coronary artery bypass surgery with a LIMA to the LAD, a saphenous vein graft (SVG) to the distal RCA, and a radial arterial graft to a large obtuse marginal (OM) system. Two months later, the patient presented with recurrent angina and a coronary angiogram showed significant disease at the distal anastomotic site of the SVG to the RCA and a subtotally occluded radial graft to the OM. The native RCA was stented with a Cypher™ Stent (Cordis Corporation, Miami, Florida), and extensive stenting was performed in the radial graft using 9 short Multi-Link Pixel® coronary stents (Guidant), yielding a final diameter of 2.5 mm. Attempts to deliver drug-eluting stents at that time were unsuccessful. Several weeks later, the patient began to experience recurrent symptoms which led to a repeat angiogram 3 months later. The coronary angiogram demonstrated an occluded radial artery bypass graft to the OM at the stent sites (Figure 2A). All other vessels showed no changes from the previous angiogram. An 8 Fr JR4 guiding catheter was used for support. Initially, a 0.014 inch Asahi Prowater guidewire was used to probe the CTO and could only be advanced approximately 10–15 mm into the lesion; the vessel tortuosity and the CTO lesion type caused the wire to migrate away from the central lumen toward the stent struts. After approximately 15 minutes of probing, further wiring of this lesion was deemed futile and the coronary wire was exchanged for the Frontrunner device. Blunt microdissection was performed throughout the entire stented segment of the graft without difficulties and took approximately 10 minutes (Figure 2B). The lesion was re-wired with the Choice PT (Figure 2C). Predilatation was performed using a 1.5 x 15 mm Voyager™ RX Coronary Dilatation Catheter (Guidant), a 2.25 x 20 mm Maverick 2, and followed by a 2.75 x 10 mm Cutting Balloon. Intravascular ultrasound with the Atlantis® SR Pro Catheter (Boston Scientific) provided the proper vessel sizing. Stenting of the entire graft was achieved with Taxus Express2 stents (from distal to proximal): 2.5 x 24 mm, 2.75 x 32 mm, 2.75 x 28 mm, and 3.0 x 32 mm. Postdilatation was performed using the Quantum™ Maverick™ (Boston Scientific) balloon to an estimated final diameter of 3.08 mm proximally and 2.75 mm distally based on the balloon compliance chart (Figure 2D). Discussion Two successful cases of PCI of in-stent restenosis CTO were presented. Both cases had failed initial wire attempts. The relatively long length and high degree of tortuosity of the occluded segments, especially in the bypass graft case, made further wire attempts unattractive. The relatively firm intimal hyperplastic tissue or possibly organized thrombus, as well as vessel curvature, guided the wire tips toward the stent struts making further manipulation difficult. The relatively easy passage with the Frontrunner and the successful outcome of these cases were attributed to the presence of the previously placed stents. The stent “skeleton” allows for direct visualization of the anatomic course of the vessel’s trajectory. A big challenge in CTO-PCI is to know where to probe, and the existing stents mitigate this technical difficulty. Furthermore, the original stents can serve as a protective shell to minimize the likelihood of vessel trauma and perforation, especially with the use of a relatively blunt device such as the Frontrunner microdissection catheter. Because of the relative security gained by direct visualization and relative protection, the operator is afforded a more aggressive approach, thereby increasing the chances of procedural success. Potential complications of the Frontrunner may include coronary perforation, which may lead to cardiac tamponade, myocardial infarction and death.5 In cases of in-stent restenosis, however, the use of the microdissection device is deemed safer because the tip of the device is blunt and larger than the cells of the stents. The risk of vessel perforation in the stented segment, therefore, should be much less than non-stented segments. Few cases of CTO-PCI using the Frontrunner device have been reported in de novo coronary and peripheral arterial occlusions.6–8 There is only one other CTO-PCI with blunt microdissection in native coronary in-stent restenosis reported in recent literature. The in-stent restenosis CTO occurring in an arterial bypass graft with a subsequently successful PCI result using the Frontrunner adds to the uniqueness of this report. The Frontrunner blunt microdissection catheter may facilitate the recanalization of a vessel occlusion when the standard initial approach with coronary guidewires fails. This further allows for treatment of the in-stent restenosis, which includes drug-eluting stents and intracoronary brachytherapy. These modalities have shown promising long-term results.9,10 The successful treatment of patients with in-stent restenosis CTOs may provide benefits similar to those achieved with successful PCI of de novo coronary CTOs.11 The potential contribution of the blunt microdissection catheter in the treatment of CTOs, with or without in-stent restenosis, merits further study.
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