Major stent deformation/pseudo fracture of 7 crown Endeavor stent: Incidence and causative factors

Abstract

Introduction: This is the initial report of a unique complication of the 7 crown Endeavor stent (2.25–2.75mm) whereby the post-dilation balloon catches and causes major stent deformation angiographically appearing as a large stent fracture (see figure). We sought to determine frequency and cause. The 7 crown stent has a single helix supporting backbonewhich improves flexibility but limits longitudinal strength. Methods: A retrospective analysis of all 7 crown Endeavor stents deployed at our institution. Bench testing was also performed by deploying and post-dilating stents in 2.5mm tubing at a 50mmdiameter constant curve, then imaging with IVUS and optical scanning. Results: There were 7 cases of major stent deformation/pseudo fracture representing an incidence of 1.0% (7/ 701), or 1.2%of stents thatwerepost-dilated (7/575). Procedural variables increasing risk include tortuosity and the use of stiffer wires. In benchtop testing, balloon “catch” was reproducible at a frequency of 10–50% depending on technique. Factors increasing frequency included suboptimal stent deployment, stiffer wires, and slower speed of balloon advancement. Under worst case conditions (tip of the post-dilatation balloon came in contact with the stent opposite its supporting helix) balloon catch resulted in significant stent deformation 10% of the time. The complication could not be replicated with 9 crown stents (double helix weld pattern). Conclusion: When post-dilation is performed, major stent disruption/pseudo fracture occurs with the 7 crown Endeavor in 1.2% of cases. Operators need to be aware of the complication and develop strategies to deal with it.