Journal of Invasive Cardiology

Abstract: Background. We evaluated the clinical and angiographic outcomes of silicon carbide-coated cobalt chromium PRO-Kinetic bare-metal stent in patients with acute ST-segment elevation myocardial infarction (STEMI) who underwent primary percutaneous coronary intervention (PCI). Methods. Patients with acute STEMI (2.75-5.00 mm vessels; lesion length ≤30 mm by visual estimation) were treated with PRO-Kinetic stents at 5 centers in Korea. The primary endpoint was the rate of major adverse cardiac events (MACE), defined as all-cause death, new myocardial infarction, and target lesion revascularization (TLR) at 6-month follow-up. Follow-up angiography was recommended after the completion of the 6-month clinical follow-up. Results. A total of 64 patients (56.6 ± 12.9 years old, 56 male) were enrolled in the study. Procedural success was achieved in 100% of the lesions. The mean stent size was 3.51 ± 0.67 mm and the mean stent length was 20.3 ± 4.4 mm. There was 1 case of in-hospital death due to cardiac tamponade. During the 6-month clinical follow-up, 4 patients (6.3%) received TLR. Therefore, the total rate of MACE was 7.8%. Angiographic follow-up data were available for 42 patients (65.6%) and the in-stent late lumen loss was 1.02 ± 0.62 mm and in-segment late lumen loss was 0.99 ± 0.64 mm. Binary restenosis occurred in 53% of reference vessel diameters (RVDs) ≤3.0 mm, 25% of RVDs between 3.0 and 3.5 mm, and 0% of RVDs >3.5 mm (P=.006). Conclusions. The use of the PRO-Kinetic stent seems to be safe and feasible in primary PCI for acute STEMI, and shows favorable clinical and angiographic outcomes in large (>3.0 mm) coronary arteries, but not in small arteries. 

J INVASIVE CARDIOL 2012;24(6):270-273

Key words: bare-metal stent, acute myocardial infarction, restenosis

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Drug-eluting stents (DESs) have shown favorable results for the rates of restenosis and target lesion revascularization (TLR) compared with bare-metal stents (BMS) in patients with coronary artery disease.^1,2 However, DESs may be associated with an increased incidence of stent thrombosis (ST), particularly late or very late ST.^3-5 Delayed arterial healing processes, incomplete endothelial cell covering, inflammation, and hypersensitivity reaction of polymers may play an important role in ST.⁶

Silicon carbide is a coating material with anti-thrombogenic as well as anti-inflammatory effects, and silicon carbide coating was shown in vitro to reduce the thrombogenic properties of the metal surface and facilitate complete endothelialization.^7,8 The Tenax for the Prevention of Restenosis and Acute Thrombotic Complications: A Useful Stent Trial (TRUST) study demonstrated the clinical safety and feasibility of silicon carbide-coated stents in unstable angina patients.9 However, there have been few studies about the safety and feasibility of silicon-carbide coated stents in primary percutaneous coronary intervention (PCI) for patients with acute ST-segment elevation myocardial infarction (STEMI).

The aim of this study was to evaluate the clinical and angiographic outcomes of silicon carbide passive-coated cobalt chromium stents (PRO-Kinetic coronary stent with PROBIO coating, Biotronik AG) in patients with STEMI.

Methods

Patients. The Efficacy and Safety of PRO-Kinetic Metal Alloy Stent in Hospitalized Patients with Acute ST-Elevation Myocardial Infarction (PROMETHEUS) study was performed in 5 primary PCI centers in Korea, with a prospective, open-label, and single-arm cohort design. The study protocol was reviewed and approved by the ethics committee of each hospital, and informed consent was obtained from each patient.

Patients were eligible for the study if they were >18 and <85 years old, had symptoms of STEMI for >30 minutes but ≤12 hours, and the electrocardiogram showed ST-segment elevation of more than 0.1 mV in 2 contiguous leads. The infarct-related vessel had to be a native coronary artery with a visually estimated reference vessel diameter (RVD) of 2.75-5.0 mm and lesion length ≤30 mm.

Study procedure and stent implantation. All patients received aspirin (300 mg loading and 100 mg/day indefinitely) and clopidogrel (300 mg loading and 75 mg/day for at least 1 month). Use of thrombectomy devices, predilatation, post-stenting adjunctive balloon inflation, intravascular ultrasound, intra-arterial balloon counterpulsation, or glycoprotein IIb/IIIa inhibitor were all left to operator discretion. Heparin was administered before PCI to keep activated clotting time at 250-300 seconds. Procedural success was defined as thrombolysis in myocardial infarction (TIMI) flow more than grade 2 with a final residual stenosis <30%.

Study endpoints. The primary endpoint was the rate of major adverse cardiac events (MACE), defined as all-cause death, new-onset MI, and TLR at 6-month follow-up exam. The secondary endpoint was defined as late lumen loss at the follow-up coronary angiogram. For this purpose, quantitative coronary angiographic (QCA) substudy was performed and routine follow-up angiography was recommended after the completion of the 6-month clinical follow-up. Stent thrombosis (ST) was defined according to Academic Research Consortium (ARC) definition.¹⁰

QCA analysis. Baseline, immediate postprocedure, and follow-up coronary angiographies were analyzed by QCA using the Cardiovascular Angiography Analysis System (CAAS) II (Pie Medical Imaging) by an experienced technician who was not aware of the study purpose.¹¹

The minimum lumen diameter (MLD), RVD, percent stenosis, acute gain (defined as the difference of MLD before and after stent implantation), late lumen loss (defined as the difference between the postprocedure and follow-up MLD), and binary restenosis (defined as stenosis of 50% or more at follow-up angiography) were measured. All QCA measurements of the target lesion were obtained in the in-stent zone, and over entire segment including the stent and its 5 mm proximal and distal margins (in-segment zone).

Statistical analysis. Continuous variables were presented as mean ± standard deviation. Categorical variables, presented as frequencies and percentages, were compared using the Chi-square test or Fisher’s exact test as appropriate. All statistical analyses were performed with the aid of commercially available software (SPSS version 17.0; SPSS, Inc.).

Results

Patient demographics. A total of 64 patients were enrolled for the study. The mean age of the patients was 56.6 ± 12.9 years, and there were 56 males (87.5%). Eleven patients (17.2%) had a history of diabetes mellitus and 28 patients (43.8%) had a history of hypertension. The baseline characteristics are summarized in Table 1.

Angiographic findings and procedural characteristics. Ten patients (15.6%) had 3-vessel disease, 20 patients (31.3%) had 2-vessel disease and 34 patients (53.1%) had 1-vessel disease. The right coronary artery (n = 30; 46.9%) was the most common target vessel and 41 lesions (64.1%) were of type B2 or C. The baseline angiographic and lesion characteristics of the patients are summarized in Table 2.

The mean stent diameter was 3.51 ± 0.67 mm and the mean stent length was 20.3 ± 4.4 mm. Procedural success was achieved in 100% of the lesions. The preprocedure TIMI flow was 0 or 1 in 33 patients (51.6%) and postprocedure TIMI flow was 2 or 3 in all patients.

Clinical follow-up. There was 1 case of in-hospital death due to cardiac tamponade. During a 6-month clinical follow-up period, 5 patients underwent repeated coronary angiography due to the onset of new symptoms, positive stress test, or additional planned interventional procedures, of whom 4 (6.3%) received TLR. Therefore, the total rate of MACE was 7.8%. There was no episode of ST during follow-up (Table 3).

QCA data. Baseline QCA data were available for 63 patients. Eight patients had RVDs of less than 2.75 mm. The mean RVD was 3.32 ± 0.55 mm and average lesion length was 22.8 ± 4.7 mm. Postprocedural acute gain was 2.69 ± 0.66 mm (Table 4).

Follow-up QCA data were available for 42 patients; 5 before the completion of a 6-month clinical follow-up and 37 after a 6-month follow-up. In-stent late lumen loss was 1.02 ± 0.62 mm and in-segment late lumen loss was 0.99 ± 0.64 mm (Table 5). Binary restenosis occurred in 53% of RVDs ≤3.0 mm, 25% of RVDs between 3.0 and 3.5 mm, and 0% of RVDs >3.5 mm (P=.006, Figure 1).

Discussion

This study is the first prospective clinical study evaluating the effects of PRO-Kinetic stents in patients with STEMI. In this study, we evaluated the 6-month clinical outcomes of the PRO-Kinetic stent, which showed low rates of TLR (6.3%) and MACE (7.8%), and no episodes of ST.