Delayed stent fracture after successful sirolimus-eluting stent (cypher®) implantation

Background and Objectives: Sirolimus-eluting stent (SES) is very effective for preventing in-stent restenosis through the suppression of neointimal proliferation. Treatment failure cases related to stent fracture have recently been reported on, but any studies concerning the pattern or mechanism of SES fracture are very rare. Subjects and Methods: Between December 2003 to January 2005, 457 patients underwent follow-up coronary angiography after SES implantation at three referral center. We reviewed the angiographic and procedural data for eleven of theses patients [6 males (55%), mean age: 60 year-old age, range: 43-74 years] who were proven to have experience complete SES fracture. Results: The left anterior descending artery (LAD) and right coronary artery (RCA) stent fracture were 7 cases (63%) and 4 cases (37%), respectively. Myocardial bridge was shown in 6 cases with LAD fracture (86%). Overlapping stent implantation was performed in 5 cases (45%). The mean value of the maximal angulations at the fracture site before intervention was 50° (range; 39-70°) and the mean change between the maximal and minimal angulations was 13.2° (range; 2-28°). The mean stent diameter and length were 3.0 mm (range; 2.75-3.50 mm) and 40 mm (range; 23-52 mm). Stent inflation with high pressure was performed on 6 cases (54%) and it's frequency was higher in the RCA than the LAD (3 cases, 75%, mean inflation pressure: 13.1 mmHg). The mean follow-up duration was 7.2 month and only 2 cases were admitted due to the recurrent chest pain. The binary restenosis rate was 55% (6 cases) and the restenotic lesions were treated by balloon angioplasty in 2 cases and additional stenting was done in 2 cases. Conclusion: Our results demonstrated that SES fracture occurred in 7 cases with LAD lesion and in 4 cases with RCA lesion. Long stenting including overlapping implantation and more than 40° angulated long stent implantation may be the factors for SES fracture. Our results also showed high pressure stent inflation was performed more frequently at the RCA lesion, and myocardial bridge and kinking motion was detected more frequently at the LAD lesions.