Outcomes of using Firebird rapamycin eluting stents in routine coronary intervention practice

Recent clinical trials with rapamycin-eluting stents have shown very low restenosis rates.1–4 However, the higher penetration of drug eluting stent (DES) in China is being limited by the high costs of these imported devices, especially when considering multiple stenting. Firebird (Microport Co. Ltd., China) is a rapamycin (Huadong Pharmaceutical, China) polymer-based eluting stent with reasonable cost. The objective of this study was to evaluate the safety and efficacy of using Firebird stents in routine interventional practice. METHODS Patients Eighty-four consecutive patients (101 lesions) treated with Firebird stents from September to December 2004 in our hospital were included in this study. Procedures and post-intervention medications All patients were pre-treated with aspirin and clopidogrel. 300 mg loading dose of clopidogrel before the index procedure was administered if patients were not pretreated. During the procedure, patients received intravenous unfractionated heparin 10 000 IU. All stents were implanted with high deployment pressure (>1215.9 kP). Biochemical markers [creatine- kinase (CK) and CK-MB] of acute myocardial infarction (MI) were routinely measured after the procedure in all patients. All patients were on maintenance aspirin therapy, and clopidogrel was administered for at least 9 months following Firebird stent implantation. Clinical definitions and follow-up Clinical follow-up was performed by telephone contact or office visit at 1 year after the index procedure, angiographic follow-up was scheduled for between 6 and 8 months post-procedure unless clinically indicated at an earlier time. Major adverse cardiac events (MACE) were defined as cardiac death, myocardial infarction (MI), and target lesion revascularization (TLR), either percutaneous or surgical. All deaths were considered cardiac unless otherwise documented. A non-Q-wave MI was defined as CK-MB enzyme elevation three or more times the upper limit of the normal value; when, in addition to enzyme elevation, there were new pathological Q-waves in the electrocardiogram, the event was defined as a Q-wave MI. Target lesion revascularization (TLR) was defined as a repeat intervention with a stenosis ≥50% within the stent or in the 5 mm proximal or distal segments adjacent to the stent. Target vessel revascularization (TVR) was defined as repeat revascularization within the target vessel. Stent thrombosis was defined as an acute coronary syndrome with angiographic documentation of either vessel occlusion or thrombus within or adjacent to a previous successfully stented vessel. Quantitative coronary angiography (QCA) Coronary angiograms were analyzed using validated edge detection system (MEDCON TCS QCA software package, Israel). On the pre-intervention angiogram, reference vessel diameter (RVD) and lesion length were measured. Minimal lumen diameter (MLD), RVD and percent diameter stenosis (DS%) at post-procedure and at follow-up were measured, respectively. Late lumen loss was defined as the difference between the MLD immediately after the procedure and at follow-up. Angiographic restenosis was defined as DS≥50% by QCA within a previously stented vessel segment (5 mm proximal and distal) at the follow-up angiography. Statistical analysis Continuous variables with normal distribution were expressed as mean ± standard deviation (SD). Categorical variables were presented as frequencies (%). P<0.05 was considered significant statistically. RESULTS Baseline clinical and procedural characteristics There were 67 male patients (79.8%) in this study. The average patient age was (60.6±10.3) years (range 30 to 79 years), with an incidence of 15.5% of diabetics, 66.7% of hypertension, 40.5% of hyperlipidemia, and 27.4% of current smoker in the study group. Presenting clinical symptoms were stable angina in 38 (45.2%) and unstable angina in 46 (54.8%). There was a history of previous MI in 33 patients (39.3%). Approximately half of lesions were located in left anterior descending coronary artery (51.5%), and 82.1% of lesions were complex lesions (≥ACC-AHA class B2). The average diameter of reference vessels average was (2.95±0.39)mm, and mean length of lesions was (18.6±12.9)mm. The mean number of stents per lesion was (1.3±0.7) (135/101), and the average stent length was (24.1±14.6)mm. High stent deployment pressure [mean (1479.3± 263.4) kPa] was used. Of all lesions, 76.2% were treated with one stent, 14.9% with 2 stents, and 8.9% with 3 or more stents. Lesion success rate was 98.0%. Quantitative coronary angiography (QCA) Follow-up coronary angiography was performed in 43 (64 lesions) patients (51.2% of eligible cases) (Table 1). Binary restenosis (diameter stenosis >50%) was identified in 3 lesions (3 patients) (4.7%); all of them were occurred within the stent. All restenosis were focal and <10 mm in length. Among these 3 patients, 2 were asymptomatic (DS%<60%) and did not undergo repeat revascularization, 1 was stent under expansion (intravascular ultrasound identified) and was retreated with high-pressure balloon angioplasty. Obviously, the late luminal loss (in-stent) reduced to (0.17±0.44) mm.Table 1: Quantitative coronary angiography (n=43, mean±SD)Clinical outcomes Major adverse cardiac events (MACE) in the hospital and at one year of follow-up are listed in Table 2. All studied patients underwent clinical follow-up. No patient died in hospital and during the follow-up period. Non-Q-wave myocardial infarction occurred in 2 patients in the hospital due to side branch occlusion. During the follow-up period, 1 patient was supposed to have late stent thrombosis, which presented with unstable angina without cardiac enzyme elevation. Two patients underwent TLR.Table 2: Major adverse cardiac events (MACE) in the hospital and outside of the hospital during one year of follow-up (n=84)DISCUSSION Sirolimus (rapamycin)-eluting stent implantation has been proven to markedly reduce the incidence of angiographic restenosis and repeat revascularization in patients with coronary heart disease.1–4 Firebird stent is a sirolimus (rapamycin)-eluting stent, which is made in China. The effectiveness of Firebird stents in unselected patients treated in the daily practice is currently unknown. In this study, the use of Firebird stent implantation in the “real word” interventional cardiology was associated with a low rate of MACE, mainly because of a reduced incidence of target lesion revascularization. In particular, Firebird stent demonstrated effective suppression of neointimal hyperplasia with a late lumen loss of 0.17 mm in-stent and 0.08 mm in-segment, respectively, which is comparable to that (0.17 mm and 0.24 mm, respectively) of the important study of the sirolimus-eluting Bx velocity balloon expandable stent trial (SIRIUS). Accordingly, the restenosis rate observed after Firebird stent was strikingly lower (4.7%, both in-stent and in-segment) than those in SIRIUS (3.2%, 8.9%, respectively). No “edge effect” phenomenon in this study might be due to procedural technique improvement. During the study period, we avoided “pull back” dilatation and fully covered the lesion. Among 3 patients with restenosis, consistent with previous reports regarding the angiographic pattern of restenosis of sirolimus-eluting stent (SES), all our restenoses were focal and therefore easy to treat with repeat percutaneous coronary intervention.5 In this study, stent success rate was high, and no patients died throughout the whole period. Only two (2.4%) non-Q-wave MI occurred in hospital, both of that were caused by side branch occlusion, which was obviously related to technique problem. One patient who presented with unstable angina during follow-up period was found to have late stent thrombosis. In this case, the target lesion was in-stent restenosis, which was previously reported to be associated with higher incidence of stent thrombosis after SES restented. Based on the evidence mentioned above, we suppose that Firebird stent implantation is safe in the daily coronary interventional practice. The major limitations of this report are the non-randomized study design and angiographic follow-up was not performed in all patients. A small volume of patients was another limitation of this study. In conclusion, the final results of the pilot study suggest that using Firebird stents in routine interventional practice is associated with a high procedural success rate and low incidence of MACE during hospitalization and at one-year follow-up.