Fracture of Zotarolimus-Eluting Stent after Implantation

Abstract

Drug-eluting stents were developed and approved for the reduction of in-stent restenosis. However, restenosis still occurs, and stent fracture is suggested as a cause of restenosis after implantation. Although sirolimus-eluting stents are considered to carry a high risk of fracture, the risk is also present with other drug-eluting stents. Herein, we report the case of a 78-year-old woman who received a zotarolimus-eluting stent for a bifurcation lesion of the left anterior descending coronary artery. Ten months later, she underwent coronary angiography due to angina. The angiogram revealed in-stent restenosis, with a grade IV stent fracture. After percutaneous coronary angioplasty, the patient's clinical symptoms improved.

Although drug-eluting stents (DESs) reduce in-stent restenosis, important complications of coronary DESs are restenosis and thrombosis. Stent fractures have also been reported¹ and are considered to be possible causes of restenosis² within DESs. The sirolimus-eluting stent is reported to be prone to fracture.³ For example, there is the Cypher® stent (Cordis Corporation, a Johnson & Johnson company; Miami Lakes, Fla)—made of balloon-expandable stainless steel, a durable copolymer mixture of polyethylene-covinyl acetate and poly-u-butyl methacrylate, and sirolimus, which is a Gap 1 (G1) cell-cycle inhibitor.⁴ Other DESs are also considered to be at risk of fracture. One, the Endeavor® Sprint Zotarolimus-Eluting Coronary Stent System (Medtronic, Inc.; Minneapolis, Minn), uses a cobalt chromium stent platform; a durable, antithrombotic, phosphorylcholine-encapsulated coating; and another G1 cell-cycle inhibitor, zotarolimus.⁴ Here, we report the case of a woman who was treated with a zotarolimus-eluting stent that subsequently fractured.

Case Report

In June 2007, a 78-year-old woman with hypertension and dyslipidemia presented with stable angina pectoris. She underwent a stress test, which was positive. Elective coronary angiography revealed a substantial lesion of a bifurcation of the left anterior descending coronary artery (LAD). The left main coronary artery was engaged with a 6F guiding catheter via a left radial approach. A 0.014-inch IQ™ guidewire (Boston Scientific Corporation; Natick, Mass) was used to cross the bifurcation lesion in the LAD. The lesion was dilated with a Sprinter® RX Balloon Dilatation Catheter (2.5 × 20 mm, Medtronic) at 8 atm, and an Endeavor stent (2.5 × 24 mm) was deployed at 12 atm. The guidewire was inserted into the diagonal-branch crossing of the stent, and the ostial stenosis of the diagonal branch was dilated with a Sprinter balloon (2 × 20 mm). The final result was good.

The patient was discharged from the hospital on medical therapy, including ticlopidine, fluvastatin, and valsartan. Ten months later, her clinical symptoms of angina returned. Coronary angiography revealed a grade IV stent fracture (Fig. 1) that was associated with substantial in-stent restenosis (Fig. 2). We treated the bifurcation lesion using the kissing-balloon technique (Sprinter 2.5 × 20 mm at 8 atm in the LAD, and a Sprinter 2.5 × 20-mm balloon at 6 atm in the diagonal branch). Afterwards, the patient's clinical symptoms improved. Her clinical condition remained stable on follow-up.

Fig. 1. Cineangiography reveals a grade IV fracture in the Endeavor stent (arrows).

Fig. 2. Coronary angiography reveals in-stent restenosis at a bifurcation of the left anterior descending coronary artery (arrow).

Discussion

Drug-eluting stents were developed in the early 2000s. The Cypher stent was approved for clinical use in Europe in April 2002 and in the United States in May 2003. Many other DESs were later approved for clinical use. Although DESs decreased restenosis more than did bare-metal stents, in-stent restenosis was still observed in some patients. In association with in-stent restenosis, stent fractures occurred in 3% to 18% of implanted DESs.^3,5,6 Shaikh and colleagues³ reported that the frequency of fracture depended upon stent type, anatomic location (in the right coronary artery more than in the LAD, and in the LAD more than in the left circumflex coronary artery), vessel geometry (bend, >75°), the number and length of stents, and the presence of overlap. Stent fracture was identified in 23.9% of cases of sirolimus-eluting stent-associated restenosis, and in 9% of cases of restenosis in paclitaxel-eluting stents.³ However, that report³ was a retrospective analysis, and not a randomized or double-blind study. Large prospective studies are needed to determine the incidence and risk factors that are associated with stent fracture. In addition, the incidence of stent fracture in zotarolimus-eluting stents is unclear.

Zotarolimus-eluting stents were evaluated through trials of the Endeavor stent and the ZoMaxx™ stent (Abbott Vascular; Redwood City, Calif). The ZoMaxx-I trial was halted due to a high incidence of late luminal loss.⁷ The Endeavor stent is still approved for clinical use. The frequency of fracture and the mechanisms that underlie the fracturing of Endeavor stents are unclear. In our patient, stent angulations and the angioplasty for the bifurcation lesion after stent implantation could have been the cause of the fracture.

The morphologic classification of stent fracture⁸ is as follows: grade I, single-focal strut fracture; grade II, 2 or more focal strut fractures; grade III, 2 or more focal strut fractures with deformation of the stent without transsection; and grade IV, fractures with transsection. The diagnosis of stent fracture should include routine high-resolution cineangiography (stent boost), especially when in-stent restenosis of a DES is suspected. Intravascular ultrasonography is also helpful in the evaluation of stent fractures. Yamada and colleagues⁹ reported that intracoronary ultrasonography can more reliably detect stent fracture than can coronary angiography. Lim and associates¹⁰ showed that the sensitivity of 64-section coronary computed tomographic angiography enables the early detection of stent fracture.

In conclusion, stent fracture should be considered when in-stent restenosis of a DES is suspected, even in a zotarolimus-eluting stent. High-resolution cineangiography is the 1st choice for evaluation of stent condition.