Direct Microscopic Observation of Striations in a Fractured Section of a Sirolimus-Eluting Stent (Cypher Bx Velocity^®) Indicates Induction of Stent Fracture by Continuous Shear Stress

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A 73-year-old woman with severe congestive heart failure was treated by implantation with a sirolimus-eluting stent (SES; Cypher Bx Velocity^®) in the left main coronary artery (LMCA) using the staged T-stent, kissing balloon, and hugging balloon techniques. Follow-up coronary multislice computed tomography after 10 months revealed that SES was completely fractured in 2 directions; the fractured stent appeared in the shape of the letter “L” and had migrated into the aorta. An SES fragment was surgically removed and subsequent electron microscopy revealed striations (striped patterns in fractured sections) on the fracture plane, indicating continuous shear stress after SES implantation in the LMCA. This case provides direct evidence of continuous shear stress on the SES and indicates the necessity of improving the structure of the stent such that it can withstand shear stress.