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Chinese “Firebird” Brand Sirolimus-eluting Stent Fracture
From the Department of Cardiology, Shanghai Minhang District Central Hospital, Shanghai, China. The authors report no conflicts of interest regarding the content herein. Manuscript submitted May 4, 2009, provisional acceptance given June 23, 2009, final version accepted July 15, 2009. Address for correspondence: Wei Hu, Department of Cardiology, Minhang District Central Hospital, 201100, Shanghai, China. E-mail: huwei0516@hotmail.com
_______________________________________________ ABSTRACT: Recently, a stent fracture (SF) was reported as having occurred with sirolimus-eluting stents (SES) and paclitaxel-eluting stents (PES). The Chinese Firebird brand stent is a type of SES that has a similar structure to the Cypher stent. As of early 2008, Firebird SES have been used in 200,000 cases worldwide, but there have been no reported cases of stent fracture in relation to this brand. In this report we highlight a case of SF with the Firebird SES which occurred more than thirteen months after implantation.
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J INVASIVE CARDIOL 2009;21:E242–E244 Key words: stent fracture; acute coronary syndrome Drug-eluting stents (DESs) can significantly reduce the incidence of in-stent restenosis when compared with bare-metal stents, resulting in increasing use of DESs in current clinical practice, this is also the case in China. The Firebird stent (Microport Co Ltd, China) is a type of sirolimus-eluting stent (SES) which is made from 316L stainless wire, and which has a similar structure to, but different drug-coating technique from, the Cypher stent (Cordis Corp, Miami Lakes, Florida). The safety and efficacy of Firebird SES has been demonstrated, and up to early 2008, more than 200,000 Firebird stents have been used worldwide.1,2 Recently, cases of stent fracture (SF) have drawn the keen attention of interventional cardiologists. Although several small studies showed that SF seemed to occur more often with SES than with pacitaxel-eluting stent (PES), one cannot draw this conclusion before more evidence is gathered.3–5 Although a large number of Firebird SES have been used, there have hitherto been no cases of SF reported in relation to this brand. Here, we report a case of stent fracture with the Firebird SES, more than 13 months after implantation. Case Description. In June 2005, a hypertensive 58-year-old female was diagnosed with sub-acute anterior wall myocardial infarction. A selective coronary artery angiography (CAG) documented two-artery-disease: two lesions located in the proximal and middle segment of left anterior descending artery (LAD, in the proximal and middle segment, respectively, see Figure 1A), two lesions in the distal segment of the left circumflex (LCX) and its branch. Only the two lesions of the LAD were treated by percutaneous coronary intervention (PCI): a 2.5 x 23 mm Firebird SES was implanted with 12 atmospheres (ATMs) in the middle segment after balloon angioplasty. The direct stenting technique was adopted to treat the proximal lesion, with the implantation of a 3.0 x 18 mm Firebird SES, using 14 ATMs. There was a 5 mm distance between the two stents. The immediate follow-up CAG demonstrated a good result (see Figure 1B). In July 2006, the patient underwent a second CAG because of atypical chest pain, which showed no in-stent restenosis, SF or novel lesion (see Figures 2A and B). In September 2008, the patient was hospitalized for a third time, being diagnosed with acute non-ST segment elevation myocardial infarction (NSTEMI). An emergency CAG showed no lesion progression in the LCX or right coronary artery (RCA), however, the middle stent of the LAD was completely fractured, with development of a small aneurysm, and the LAD was occluded at this site (see Figures 3A and B). Moreover, three other small, isolated aneurysms were detected in the middle and distal part of the proximal stent and at the beginning of the middle stent, respectively (Figures 3B and C). Because the patient refused an attempted re-PCI, he finally received coronary bypass surgery (CABG). Discussion. To the best of our knowledge this is the first case report of SF using the Firebird SES. After reviewing published literature, it appears that the prevalence of SF varies from 1.7–7.7%. Although several small studies showed that SF seemed to occur more often with SES than with PES, one can not draw this conclusion before more evidences appeared.3–5 The variation may be explained by different lesion characteristics, techniques of detection, the definition of SF and the follow-up time. Since the Firebird stent is a type of SES and has similar structure to the Cypher stent, the fracture rate of this brand needs to be studied in the future. In our case, although the LAD was occluded at the site of SF and the patient presented with acute NSTEMI, we don’t believe SF occurred suddenly because the arterial lumen at the site of SF was stretched into a small bend and developed into a small aneurysm. It seems clear that SF occurred at least 13 months after implantation because there was no evidence of SF when the patient underwent the second CAG. Based on the published data, and including our case, one can ascertain that SF may occur immediately or a long time after stent implantation.6–8 Unfortunately, at present the exact mechanisms of SF are unknown. Lesion characteristics (long length, RCA or saphenous vein graft or hinge point location, bifurcation, calcification and tortuosity, etc.), procedural factors (operator's experience, dilatation pressure, overlapping or not, etc.) and stent type are thought to be possible reasons for SF..8–10 In our case, SF may be associated with long lesion length, hinge location, relative low dilatation pressure and stent type. It is also unknown whether the mechanism of acute SF is different to that of late SF. It is assumed that acute SF might be caused by procedural factors, while metal fatigue may also play an important role in late SF. There is still some discussion on the clinical impact of SF.3–5,10–12 Some authors think it does not cause adverse events, while others think it can result in binary restenosis, stent migration, development of aneurysm and thrombus. In our case, SF caused occlusion of the LAD and presentation of NSTEMI, in addition, several small aneurysms were detected within the stented segment, which may be caused by released drug toxicity that disturbed the intimal healing process. Okamura et al reported a case of SF which resulted in the development a giant aneurysm.11 Several current imaging techniques can detect SF, such as CAG, intravascular ultrasound and 64-multi-detector row computed tomography,7,10,11,13 however, among these imaging techniques, CAG may be the best choice when SF causes adverse clinical outcomes. Moreover, if possible, re-PCI may be a good choice in this situation. In our case, however, the patient preferred surgery.14 Two things can be learned from our case. Firstly, SF may also occur with the Chinese Firebird SES. Secondly, SF may occur very late after implantation.
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