Stent Longitudinal Integrity: Bench Insights Into a Clinical Problem
What are the stent design features that predispose to longitudinal distortion?
The authors used bench-top testing to assess the impact of force required to compress and to elongate seven contemporary stents. Stents were deployed in a silicone phantom and were damaged by a balloon or guide catheter and then were imaged using microcomputed tomography.
The stents with two connectors (Omega/Element from Boston Scientific and Driver/Endeavor from Medtronic) required significantly less force to be compressed up to 5 mm and elongated by 1 mm than designs with more connectors. The Cypher Select stent with six connectors required the most force for any longitudinal distortion. The Liberte and Integrity required more force than the Driver to compress by 1 mm, whereas the Vision and Multilink distorted at forces similar to that required to compress the Cypher Select stent. The Omega and Driver stents required the least amount of force to elongate by 1 mm, followed by Liberte and Integrity stents, whereas the Vision and Multilink stents required more force to elongate, with the Cypher Select stent requiring the most force to elongate.
The authors concluded that the number of interconnectors between hoops appears to influence longitudinal stability, with stents with more connectors most resistant to elongation or shortening.
This bench-top study provides an important backdrop to the recent interest in Concertina effect prompted by reports from European centers. This study suggests that attempts to increase flexibility come at the cost of longitudinal stability, and stents with too few interconnectors may be more prone to shortening; this may potentially predispose to restenosis and/or stent thrombosis, and obstruct passage of devices. The clinical implications of this, however, remain unknown since it appears to be a rare condition with only sporadic case reports. The most longitudinally stable stent (Cypher Select) is no longer available, but the other four stents (Vision, Multilink, Liberte, and Integrity) that demonstrated reasonable longitudinal stability are commonly used, have a proven record of safety and efficacy, and should be preferentially considered when longitudinal distortion may be a potential concern.
Keywords: Cyclopentanes, Coronary Restenosis, X-Ray Microtomography, Coronary Angiography, Thrombosis, Boston, Silicones, Catheters, Pressure, Stents
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