Sirolimus-Eluting Stent Implantation Outside a Previous Stent

Case Presentation. A 43-year-old male with a history of myocardial infarction and primary stenting (left circumflex artery in July 1997 and right coronary artery in September 2005) was admitted to undergo angioplasty for his totally reoccluded left circumflex artery (Figure 1A). After a hydrophilic-coated soft wire with a microcatheter failed to cross the lesion, a tapered-tip stiff wire, designed for chronic total occlusions, was able to cross the lesion.¹ Neither the microcatheter nor a 2.0 x 15 mm balloon was able to cross the in-stent reoccluded segment, so a Tornus^® penetration catheter (Asahi Intecc, Tokyo, Japan) was selected next. This catheter has a main shaft consisting of 8 stranded stainless-steel wires designed to cross through a severe stenosis by manual rotation.² After successful penetration with the catheter and dilatation with the balloon, 3 Cypher™ sirolimus-eluting stents (Cordis Corporation, Miami, Florida) were implanted at a pressure of 16 atm.
As stent underexpansion is a significant cause of failure after sirolimus-eluting stent (SES) implantation for treatment of in-stent restenosis,³ intravascular ultrasound (IVUS) examination was performed to ensure optimal stent expansion. Although coronary angiography showed optimal results (Figure 1B), IVUS examination revealed a crushed stent (crescent-shaped) previously implanted outside the SES (Figures 1C, D, and E), suggesting subintimal (outside the stent) passage of the guidewire. IVUS examination before balloon dilatation/stent implantation should have been performed if true intraluminal passage had not been ensured. However, we chose to end the procedure because IVUS verified that the stents were fully expanded. At 7-month follow up, 64-slice computed tomography (Somatom Sensation 64, Siemens Medical, Malvern, Pennsylvania, 120kV, 800mA, collimation 0.6 mm, rotation time 0.33 sec) was performed for his atypical chest pain. While the stents were patent, double-barrel stents were seen on several axial cross-sections (Figure 2).

Discussion. The procedural success rates of percutaneous coronary intervention (PCI) in chronic total occlusions (CTOs) have steadily increased over the past 15 years because of greater operator experience as well as improvements in equipment and procedural techniques. Despite these improvements, CTOs remain the lesion subtype in which PCI is most likely to fail. The most common PCI failure mode is the inability to successfully pass a guidewire across the occlusion into the true lumen of the distal vessel. In a recent large series,⁴ reasons for procedural failure included the inability to cross the lesion with a guidewire (63% of cases), long intimal dissection with creation of a false lumen (24%), dye extravasation (11%), failure to cross the lesion with the balloon or to dilate adequately (2%), and thrombus (1.2%).
Numerous devices have been developed to improve procedural success rates. Many of these devices never progressed beyond the investigational phase because their use demonstrated either excessively high rates of complications (typically either dissection and/or perforation) or success rates not clearly greater than those achieved by standard equipment.⁵ Two devices specifically designed for refractory CTO recanalization have demonstrated sufficient safety and efficacy to have received approval by the Food and Drug Administration: the Safe Cross-RF guidewire (Intraluminal Therapeutics, Inc., San Diego, California)⁶ and the Frontrunner catheter (LuMend, Inc., Redwood City, California),⁷ though neither have been approved in Japan. Other novel device-based and pharmacological strategies currently under investigation include a penetration catheter (used in this case),² lumen re-entry devices, connections between a coronary artery and vein, prolonged infusions of fibrinolytic agents, therapeutic ultrasound, vibrational angioplasty, forward-looking ultrasound and magnetically-enabled three-dimensional wire guidance.⁸ Lumen reentry devices have been developed to facilitate guidewire reentry into the true lumen after the creation of a dissection plane, including the ultrasound-guided Pioneer catheter (Medtronic, Inc., Minneapolis, Minnesota),⁹ and the fluoroscopically-directed LuMend Outback catheter, which have been mainly used in treating peripheral artery disease. Recently, subintimal tracking and reentry techniques have been introduced in the treatment for coronary artery disease after failure to cross the occlusion with conventional guidewires.¹⁰ Although the procedural success rate, defined as distal lumen penetration with TIMI 3 flow, was as high as 97% (30/31), the target vessel revascularization rate was high (52%, 11/21) despite 60% use of drug-eluting stents. These devices and technique were not applicable for in-stent occluded lesions such as this case because these may cause stent deformation and fracture.
In conclusion, with device improvements, more total occlusions have been crossed with a guidewire and balloon. However, true intraluminal/intrastent passage is not always accessed, which is not apparent on coronary angiography. In such cases, careful intravascular ultrasound examination may be required to ensure true intraluminal passage and avoid complications such as perforation prior to stent implantation in totally occluded lesions (with or without a previous stent).

Acknowledgment. The authors gratefully acknowledge the excellent assistance of all medical personnel in the catheterization laboratory. The authors thank Heidi N. Bonneau, RN, MS, for her expert review of the manuscript, and Shingo Mizuno, MD and Satoshi Sekine, RT, for their help with CT imaging.

References

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