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Six-Month Clinical and Angiographic Outcomes of the Tecnic Carbostent‚Ñ¢Coronary System: The Phantom IV Study
November 2004
The Tecnic Carbostent™ (Sorin Biomedica, Saluggia, Italy) is a balloon-expandable, stainless steel tubular coronary stent with a unique cellular design and proprietary Carbofilm™ permanent coating.1-3 Recently the stent has been pre-mounted on a new low-profile rapid-exchange delivery system. The aim of this study was to assess the procedural, in-hospital, and long-term clinical and angiographic outcomes of patients undergoing angioplasty with the new Tecnic Carbostent system for de novo coronary lesions.
Methods
Patient population. Between October 2001 and March 2002, consecutive patients with symptoms or signs of coronary artery disease scheduled for stent implantation at three clinical centers were considered for study enrolment. Inclusion criteria were: de novo coronary lesion, stable or unstable angina, and silent ischemia. Patients were excluded from enrolment if they had: evolving myocardial infarction; ejection fraction 140 µmol/L); contraindications to heparin, aspirin or ticlopidine therapy. All patients gave their informed consent for the stent procedure. Furthermore, in accordance with the study protocol and institutional Ethics Committee approval, all patients treated in two of the three clinical centers gave informed consent for 6-month angiographic follow-up.
Study endpoints. Primary endpoints were the procedural success and the incidence of major adverse cardiac events (MACE) in hospital and at 30 days. Secondary endpoints were the rate of major bleeding and site access complications, the stent elastic recoil as assessed by quantitative coronary angiography (QCA), and the incidence of angiographic restenosis at 6 months.
Procedural success was defined as a residual stenosis 2 ECG leads together with an increase in CK-MB levels to at least twice the upper normal limit. Non-Q-wave myocardial infarction was diagnosed if CK-MB levels were three or more times normal values in the absence of any new pathological ECG Q-waves.
Major bleeding was defined as cerebrovascular, retroperitoneal or gastrointestinal bleeding, or the need for any blood transfusion. Site access complications, defined as A-V fistula, pseudoaneurysm, major hematoma (hematoma associated with > 15% decrease in hematocrit) and surgical repair, were also assessed and recorded. Patients were seen at the outpatient’s clinic at 1 and 6 months for an interview, physical examination and ECG.
Stent procedure. All procedures were performed via the femoral approach using 6 Fr or 8 Fr guiding catheters. A bolus of 5,000 units of heparin was given after sheath insertion, and then supplemented as needed to maintain an activated clotting time of 250 seconds throughout the procedure. The use of pre-procedural infusion of glycoprotein IIb/IIIa receptor inhibitors was left to the discretion of the operator. After the procedure, all patients received ticlopidine 250 mg twice daily for one month, and 250–500 mg/day of aspirin indefinitely. Stent implantation was performed using a direct stenting technique or after predilation with a semi-compliant balloon. The Tecnic Carbostent (9, 12, 15,19, 25 and 32 mm) was deployed using pressures of up to 20 atm, whereas post-dilation was usually accomplished by means of short non-compliant balloons.
Stent characteristics. The Tecnic Carbostent coronary system (Sorin Biomedica, Saluggia, Italy) is a stainless steel tubular stent.1 The stent has an innovative cellular geometry (omega links), conceived to avoid stress concentration and elastic distortion. The entire surface of the stent is mirror like polished and the edges are rounded to optimize fluid dynamic aspects, minimize the likelihood of trauma to the vessel wall and to reduce, in association with the Carbofilm coating, the risk of stent thrombosis. Stent struts are 0.075 mm thick, and are coated with an integral and permanent coating (0.3–0.5 µm) of turbostratic carbon (Carbofilm). This passive coating renders stent surface thromboresistant and enhances biocompatibility compared to bare metal stent as demonstrated by in-vitro studies.1 Carbofilm consists of pure carbon characterized by a polycrystalline structure. Turbostratic carbon is an ideal material for prostheses in contact with blood because of its unique physical and chemical characteristics, such as inertness, isotropy, low weight, compactness, elasticity, high strength, great hardness and wear resistance.2,3 The stent is pre-mounted on a new delivery system characterized by a hypotube shaft and a polyamide balloon that confer high pushability and very low system profile (0.04 inches).
Angiographic analysis. Trained technicians not involved in the procedures analyzed off-line all coronary angiograms using the computer-assisted Intelligent Images QCA program (version 1.4).4 The intra- and inter-observer variability of the angiographic measurements are respectively 1.1 ± 9.7% and 1.5 ± 9.2.5 In order to obtain absolute measurements of the vessel and balloon size, the images were calibrated with the contrast-filled guiding catheter of each arteriographic run. All measurements were made using end-diastolic frames with optimal vessel opacification. The lesions were classified according to the modified American College of Cardiology/American Heart Association classification.6 Acute recoil immediately after stent implantation was defined as the difference between the mean cross sectional area (CSA) of the fully expanded balloon on which the stent was mounted, and the mean CSA of the stented segment immediately after stent deployment and balloon deflation.7 Videodensitometry was used to circumvent geometric assumptions concerning the shape of the stenosis.8,9 The length of the stented segment was the sum of the length of all of the stents implanted in the coronary segment. Binary restenosis was defined as a > 50% diameter stenosis at the treated site. The morphology of in-stent restenosis was defined according to the classification proposed by Mehran, et al.10Statistical analysis. Data are expressed as mean values ± SD. Student’s T test and the chi-square test were used as appropriate. The differences in mean CSA recoil in the stent groups were analyzed by means of one-way ANOVA and a post-hoc analysis using Scheffé’s test. A p value of Patients. A total of 123 patients were enrolled into the study. The baseline clinical characteristics of the population are shown in Table 1. Most of the patients (63%) had stable angina or silent ischemia. Diabetes was present in 13% of the patients.
Procedural assessments. The angiographic and procedural characteristics are summarized in Tables 2 and 3. A total of 179 stents were implanted in 149 lesions. Direct stenting was performed in 34 lesions (23%). A single stent was used in 86.6% of the cases. Abciximab was administered in 23 patients (19%), most of whom were treated for acute coronary syndrome. The mean inflation pressure was 14.1 ± 2.7 atm, whereas post-dilation was accomplished in 35.7% of the cases. The angiographic results are summarized in Table 4. Procedural success was obtained in all cases. The mean percent diameter stenosis decreased after the intervention from 75% ± 11% to 8% ± 4%. The mean cross-sectional area recoil of the stent was 8.8 ± 7.3% (Table 5).
In-hospital and 30-day clinical outcomes. No in-hospital or 30-day MACE were documented. No major bleeding or site access complications were reported. One patient had a staged procedure on a different vessel one day after the indexed procedure.
Six-month follow-up. Six-month clinical follow-up was available in 123 patients (100%) (Table 6). During the 6-month follow-up period, there were no deaths or myocardial infarctions. A total of 18 patients (14.6%) were subjected to a new procedure of revascularisation: two patients underwent coronary artery bypass surgery and 16 repeat-PTCA. The incidence of target lesion revascularisation was 12.7% (19 out of 149 lesions). Eighty patients (92% of those with a scheduled angiographic follow-up) were readmitted to the hospital for the 6-month angiographic control. Angiographic restenosis rate was 14.1%: a focal or limited pattern (class I or II) was found in 83% of cases, whereas the remaining 17% had a proliferative morphology (class III or IV). No difference in terms of the incidence of repeat revascularisation was observed between patients who did and did not undergo routine angiographic follow-up (16% versus 12%; p = 0.46).
Discussion
This multicenter prospective experience shows the optimal performance and the good clinical and angiographic results of the Tecnic Carbostent system. The stent has some peculiar features such as a design based on modular sinusoidal elements longitudinally interconnected by omega links that permits a homogeneous expansion. The whole stent surface is integrally coated with a thin, high-density pure carbon film which superior features in terms of hemo- and biocompatibility have been widely proven in more than 10 years of experience on mechanical heart valve and polyester vascular prostheses.1-3
Our results confirm that the advanced design and surface coating of the Carbostent have non-thrombogenic properties as revealed by the absence of MACE and in particular of thrombotic events at 30 days.11,12 The biocompatibility of this stent has been the object of a previous study, which showed the effectiveness of the Carbostent in preventing thrombotic complications in a group of selected patients treated with aspirin alone.13 The prevention of stent thrombosis may be partially explained by the use of glycoprotein IIb/IIIa receptor inhibitors in 19% of the cases. However, our results are better than those observed by Schuhlen, et al.,14 in a larger series of 5,678 stented patients receiving a similar anti-thrombotic regimen.
The Tecnic Carbostent could be placed and correctly delivered in all of the attempted lesions. Compared to the previous delivery system no difference was found in terms of procedural success,11-13 however, in this study, direct stenting was allowed and was used in 23% of the procedures. The low profile (0.04 inches), and the particularly high pushability and longitudinal flexibility of this new stent system, permitted delivery even in very tortuous and complex anatomies without failure or stent dislodgement off the balloon.
The scaffolding properties and degree of elastic recoil of the Carbostent stent were also assessed. The mean percent cross sectional area recoil of the implanted stent was 8.8% ± 7.3%. This low-recoil feature is similar to that observed with the NIR stent, which showed to have the best scaffolding properties in a previous study comparing four different stent designs.7
In our experience the 6-month incidence of restenosis and target lesion revascularisation was 14% and 13% respectively. This rate of recurrence is pretty similar to that reported by Dawkins et al. in a recent multicenter trial with a second-generation stainless steel stent.15 However, it is noteworthy that our population consisted of patients with a higher proportion of lesions at high risk of recurrence, as demonstrated by a higher number of type B2 and C lesions (59% versus 41%), and a longer lesion length (15 mm versus 12 mm).
The good clinical and angiographic performance at six month of the Tecnic Carbostent can also be related to the relatively low prevalence of diabetic patients in our population (13%). In addition it can also be speculated that the particularly thin stent struts (0.075 mm) contributed to obtain this result; this hypothesis is supported by the recent results of the ISAR-STEREO-2 study that clearly demonstrated that strut thickness plays a significant role in restenosis occurrence when comparing stents with identical design.16
Another finding of our study relates to the type of angiographic in-stent restenosis pattern following the Tecnic Carbostent implantation. Several studies have shown that in-stent restenosis has a proliferative pattern in the majority of cases.12,17 The restenotic process observed in our study with the Tecnic Carbostent suggests a lower intensity of proliferation, as evidenced by the predominance of class I or II morphology (focal pattern) in 83% of the patients. This finding may indicate a high biocompatibility of this stent and its coating that translates in a modest tissue response after intracoronary implantation.18 In fact, a recent randomized comparison of the Sirius Carbostent with two different stainless steel stents showed no difference in terms of recurrence (18.1% versus 20.6% respectively). In this study, patients receiving the Sirius Carbostent had a statistically smaller post-procedure minimal lumen diameter compared to uncoated stents (2.59 ± 0.43 mm versus 2.72 ± 0.46 mm; p = 0.01).19 However, even in presence of a suboptimal procedural result, no increase of angiographic restenosis rate could be documented.
Study limitations. As the aim of this 3-center study was to provide evidence of the safety and effectiveness of the Tecnic Carbostent stent, there was no comparative arm. The trial was not powered to reveal differences in the incidence of stent thrombosis and restenosis in comparison with historical controls. Nevertheless, its results indicate excellent clinical and angiographic performance of the Tecnic Carbostent system in a series of consecutive patients with de novo coronary lesions.
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