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Early and Late Clinical and Angiographic<br />
Outcomes Following Terumo Coronary Stent Implantation
May 2002
Coronary stenting has evolved into the principal non-balloon device in percutaneous coronary intervention (PCI) procedures.(1) Continual improvement in stent designs promises greater deliverability and durability. Indeed, widespread application of this technology in an unselected population has improved patients outcomes.(2) Importantly, different stent characteristics and compositions may impact the interaction with the vessel wall, and the incidence of subsequent angiographic restenosis and clinical events.(3)
The Terumo stent (Terumo® Corporation, Osaka, Japan) is a new, balloon-expandable, stainless-steel, tubular stent. Notably, the unique 4-cell monolink structure has been shown to provide greater trackability, flexibility and conformity to the vasculature (Figure 1A). In addition, the diamond-shaped cellular design is able to afford exceptional radial strength. The “stoppers” at both ends of the stent further enhance the safety of the delivery system by preventing inadvertent embolization (Figure 1B). With these favorable characteristics, this stent has the potential to render excellent outcomes. We evaluate the immediate and long-term clinical and angiographic results following Terumo stent implantation in patients with native coronary artery disease in a prospective, multicenter study.
METHODS
Patient population. Patients were eligible for enrollment if there was symptomatic coronary artery disease or positive functional testing, and angiographic evidence of single- or multi-vessel disease with a target lesion stenosis of >= 75% in a >= 2.5 mm vessel. Patients were excluded if there was left main disease (>= 50%), recent myocardial infarction (MI) (= 3 stents needed for 1 target site. Informed consent was obtained from all patients. The study protocol was approved by each institution’s ethics committee.
Stent characteristics. The Terumo stent is a 20-mm long, stainless-steel, laser-cut, tubular, slotted-tube multicellular device mounted on a customized, non-compliant, polyethylene terephthalate (PET), non-tapered balloon with a short balloon overhang (0.5 mm). Its unique characteristics have been described earlier. In the unexpanded state, the crossing profile is 0.048´´.
Stent implantation procedure. Procedures were performed using standard angioplasty technique with a 6 French (Fr), 7 Fr or 8 Fr guiding catheter via the femoral or radial artery approach. A bolus of 100 IU/kg of heparin was administered intraarterially after insertion of the vascular access sheath. Target lesions were initially treated with appropriate balloon dilatation. The reference diameter of the target vessel was estimated visually, and stent size was determined based on a stent-to-artery ratio of 1.1:1 to 1.2:1. The stents were deployed at 8–10 atmospheres (atm), and high-pressure balloon inflation (recommended at 12 atm) was then applied with a non-compliant short balloon to avoid distal dissection.
Post-procedure medication protocol and follow-up. After successful stent implantation, heparin was not routinely administered unless there was a clinical indication, such as a large residual dissection. Radial sheaths were removed at the end of the procedure, while femoral sheaths were removed 4–6 hours after the procedure. Aspirin 100 mg once daily and ticlopidine 250 mg twice daily were continued for 2 weeks, and aspirin was thereafter 100 mg once daily indefinitely. Electrocardiograms (ECG) were recorded immediately post-procedure, then daily before discharge. Creatine kinase (CK) or its MB-fraction (CK-MB) level was measured 12 hours and 24 hours post-procedure. Additional ECG and CK/CK-MB assays were performed if the patient had recurrent chest pain post-procedure. The majority of patients were discharged 2 days post-procedure. Follow-up coronary angiography was performed at 6 months, or earlier if clinically indicated.
Quantitative angiographic measurement. Quantitative coronary angiographic analysis was performed at the National Heart Centre Angiographic Core Laboratory using the Cardiovascular Angiography Analysis System (CAAS) version 3v1.6 (Pie Medical Imaging B.V., Maastricht, The Netherlands). Angiographic measurements were obtained during end-diastole using the image that showed the greatest narrowing, without overlap and with the least degree of foreshortening. Intracoronary nitroglycerin was administered at baseline and final angiography. Measurements of the reference vessel diameter, minimal lumen diameter (MLD) and percent diameter stenosis were determined by the average of 2 orthogonal views. The index reference diameter was the average of proximal and distal reference vessel diameters. Lesion length was measured on the baseline angiography using the “shoulder-to-shoulder” definition. Lesions were characterized according to the modified American College of Cardiology/American Heart Association (ACC/AHA) classification. Changes in MLD were expressed as acute gain (post-procedural MLD minus pre-procedural MLD), late loss (post-procedural MLD minus 6-month follow-up MLD), net gain (acute gain minus late loss), and loss index (late loss/acute gain). Angiographic restenosis was defined as renarrowing of target lesion > 50% based on a single worst view.
Data collection and statistics. Demographic, clinical and technical data were prospectively entered into a computerized database. All patients were interviewed and examined monthly. Follow-up coronary angiography was performed 6 months after the procedure. If a revascularization procedure involving the target site had been performed before the 6-month angiography, the findings of the most recent angiography (>= 2 months after the initial procedure) were used as data for follow-up angiography. Data were presented as mean ± standard deviation (SD) values for continuous variables and as frequencies with percentages in parentheses for categorical variables.
RESULTS
Between July 1998 and June 1999, the Terumo stent was implanted in 105 patients for 111 lesions. Baseline demographic and angiographic characteristics of the patients are summarized in Tables 1 and 2. Of note, there was a high proportion of patients with diabetes mellitus (34%) and multivessel disease (56%). More than half of these patients had complex morphological characteristics (type B2 or C lesions). The mean reference lumen diameter was 2.76 ± 0.41 mm, with 64% of the lesions
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