1Cardiovascular Centre, OLV Hospital, Moorselbaan 164, 9300 Aalst, Belgium
2AZ Middelheim, Antwerpen, Belgium
3Friedrich-Schiller-Universitat Jena, Jena, Germany
4Krankenhaus Siegburg GmbH, Siegburg, Germany
5Catharina Ziekenhuis, Eindhoven, The Netherlands
6Kerckhoff-Klinik GmbH Bad Nauheim, Nauheim, Germany
7Hospital de Gran Canaria Dr Negrin, Las Palmas, Gran Canaria
8Reinier de Graaf Gasthuis, Delft, The Netherlands
9Erasmus Medical Centre, Rotterdam, The Netherlands
Received 22 August 2004; revised 13 February 2005; accepted 24 March 2005; online publish-ahead-of-print 11 May 2005.
* Corresponding author. Tel: +32 53724439; fax: +32 53724185. E-mail address: william.wijns{at}olvz-aalst.be
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Abstract |
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Methods and results Two hundred and two patients with a single de novo lesion (diameter 3.0 mm and length
13 mm) were randomized to DS (n=101) vs. PD. Stent deployment was guided by on-line quantitative coronary angiography (QCA). A second randomization assigned half of the patients to intravascular ultrasound (IVUS) and fractional flow reserve (FFR) assessment. QCA was repeated at 6 months. Baseline characteristics were similar. Crossover to PD was necessary in seven DS patients. Stent deployment was successful in 97% (DS) and 98% (PD). The post-procedural MLD was 2.79±0.45 mm (DS) and 2.76±0.40 mm (PD). The null-hypothesis of non-equivalence could be rejected (95% one-sided; P=0.0003). The minimum stent area (IVUS) was 7.89±1.75 mm2 (DS) and 8.07±2.37 mm2 (PD; P=0.69), with an FFR of 0.92±0.07 and 0.92±0.05, respectively (P=0.97). Major adverse cardiac event rates at 6 months were 9% (DS) and 11% (PD; P=0.93). Target lesion re-angioplasty was 6% (DS) and 5% (PD; P=0.77). The in-stent restenosis rate by QCA was 7.4% (DS) and 6.8% (PD; P=0.87).
Conclusion DS with BeStent2 is equivalent to PD. Both strategies resulted in a low angiographic restenosis rate.
Key Words: Direct stenting Restenosis Angioplasty IVUS FFR
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Introduction |
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Improvements in balloon and stent technology have resulted in the development of the direct stenting DS strategy (stent delivery without PD). This technique, demonstrated to be feasible and safe, is potentially less traumatic to vessel walls, faster, cheaper, and reduces radiation exposure.26 In several small trials, however, the DS technique showed similar results to standard PD, with the exception of lesions with angiographic evidence of calcification and in elderly subjects who may have had calcified lesions that were not angiographically evident.3,79
Randomized trials were not published at commencement of this study and the aim of the Conventional Stenting Versus Direct Stenting in (Un)stable Angina Pectoris (CONVERTIBLE) study was to compare the two strategies prospectively. If the two techniques are found to have equivalent safety and delivery success rates, the DS technique may be preferred in a selected patient population for its significant decrease in resource utilization.
Clinical, angiographic, intravascular ultrasound (IVUS), and fractional flow reserve (FFR) parameters were utilized to document the outcome of both treatment modalities. In addition, statistical techniques were applied to determine the value of these parameters to predict the 6 months angiographic restenosis rate.1012
Study objective
The primary objective of this study was to demonstrate equivalence of the minimum lumen diameter (MLD) immediately following stent placement of a DS strategy vs. the conventional PD strategy using the Medtronic BeStent2 Coronary Stent Delivery System.
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Methods |
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Trial design and randomization
This was a prospective, single-blinded, randomized, and multi-centre study. Patients were randomized from a central independent randomization centre either to DS or to standard PD procedure in a 1:1 ratio. When a final result of 15% in-stent residual stenosis was obtained, as assessed by on-line quantitative coronary angiography (QCA), the patients were either randomized to undergo additional documentary IVUS/FFR assessments or not. This secondary randomization was done to yield a 1:1 ratio (DS vs. PD) in half of the total population (Figure 1).
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All major endpoints were adjudicated by an independent Clinical Events Committee blinded to the treatment assigned.
Patient and lesion selection
Between June 2000 and July 2001, 202 patients (18 years) with stable or unstable angina pectoris or a positive functional study with a planned PCI procedure of a single de novo lesion in a native coronary artery were randomized, following informed consent, in 17 clinical centres (Appendix).
Assessment of the target vessel (a major coronary artery or major branch with visual estimated stenosis of 50 and <100%) reference diameter by on-line QCA was mandatory, and vessels suitable for implantation of a stent with a diameter of 3.0, 3.5, or 4.0 mm were selected. Additional target lesion criteria were a length of
13 mm to allow placement of a single stent with a maximum length of 15 mm. Patients with a left ventricular ejection fraction <30%, an acute myocardial infarction in the previous 3 days, a platelet count of <100 000 or >700 000 cells/mm3, a white blood count of <3000 cells/mm3, and patients with a moderately to severely tortuous vessel were excluded. In addition, lesions that were extremely calcified or containing thrombus, lesions with a side branch >2.5 mm that would be covered by the stent, and lesions with an aorto-ostial location and within 2 mm of the origin of the LAD, LCX, or RCA were excluded.
Summary of study plan
All subjects were planned to receive a Medtronic BeStent2TM. At the investigator's discretion, other stent types were utilized only when successful placement of the Medtronic BeStent2 was unachievable.
Stent implantation was guided by visual assessment and by on-line QCA. The final result was documented by on-line QCA measurements, aimed at reaching a residual in-stent diameter stenosis 15%.
At the end of the procedure, a secondary randomization assigned half of the patients in both study groups to documentary IVUS and FFR evaluation. Neither the IVUS nor the FFR measurements were used by the investigators to guide management.
Patients returned for a clinical follow-up after 30 days and for a clinical and angiographic follow-up after 6 months (scheduled between week 22 and 28 post-procedure). Variance from this schedule was restricted to demanding medical indication.
Concomitant medical therapy
Antiplatelet therapy was administered according to the centres' standard practice, with the following recommendation: either aspirin (minimum 75 mg/day) and ticlopidine (500 mg loading followed by 250 mg twice daily) or aspirin (minimum 75 mg/day) and clopidogrel (300 mg loading followed by 75 mg/day) on the day of the procedure. Ticlopidine or clopidogrel was discontinued after 14 or 28 days. Aspirin was recommended indefinitely or at least up to 6 months post-procedure.
During catheterization, all patients received intravenous heparin bolus sufficient to attain an activated clotting time (ACT), as recommended, of 250300 s and if an intravenous glycoprotein IIb/IIIa receptor blocker was administered, a lower ACT (
200 s) was maintained.
Study stent
Medtronic BeStent2TM Coronary Stent System in the rapid exchange platform was used. Manufactured from 316L stainless steel, it consists of a laser cut serpentine lattice structure with a strut thickness ranging from 0.085 to 0.095 mm. The delivery balloon overhang from the stent edges is 0.4 mm and a gold marker embedded at either ends of the stent aids fluoroscopic visualization. The available stent diameters are 3.0, 3.5, and 4.0 mm and at lengths of 9, 12, and 15 mm each.
Statistical considerations
The study was designed to evaluate equivalence by testing the null-hypothesis H0: MLDdirectMLDconv0.18; where MLDdirect and MLDconv were the mean values of the MLD after DS and conventional stenting, respectively. Rejecting the null-hypothesis would show that the mean MLD after DS is at least equivalent to the mean MLD after conventional stenting, where equivalence is defined as being within 0.18 mm.
All data were analysed using the intention-to-treat principle. It was calculated that 188 patients were needed to show equivalence between DS and PD assuming a mean MLD of 2.7 in both groups and a SD of 0.42; with the use of a significance level of 0.05 and a power of 90%. The sample size was increased to allow for patient dropout during the study period.
The primary analysis consisted of the calculation of a one-sided lower 95% confidence interval for the difference MLDconvMLDdirect. The null-hypothesis was rejected if the entire interval was <0.18. Secondary analyses were done to describe the patient population and to evaluate whether both treatment groups were equally distributed regarding baseline characteristics. These evaluations were done using the following two-sided tests for continuous variables: t-test or Wilcoxon test. For discrete variables, the following two-sided tests were used, the 2 test or the Fisher's exact test. For these evaluations, a significance level of 0.05 was used.
Analysis of variance or Fisher's exact test (two-sided) was used to evaluate if trends are visible for subgroups. First, subgroups of interest were diabetic vs. non-diabetic patients because diabetic patients tend to have higher restenosis rates. Secondly, an evaluation was made between patients with FFR0.9 and patients with FFR<0.9 because patients with higher FFR values tend to have better clinical outcome. Finally, an evaluation was made between patients that underwent IVUS/FFR, and patients that did not have this additional procedure. The latter evaluation was made to investigate if these additional procedures influenced the outcome of the study.
For evaluation of MACE, the KaplanMeier approach was applied and differences between treatment arms were calculated using the log-rank test. Continuous variables were expressed as mean±SD. The value p0.05 was considered as significant.
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Results |
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Procedural and stenting characteristics
DS was successful in 94% (94/101) of patients. Inability to reach or cross the lesion was the main reason for deployment failure. In one case, the stent dislodged from the balloon, while attempting to cross the lesion, but was successfully retrieved and delivered at the target site. With the inclusion of crossover to PD, stent deployment was successful in 97% with DS. In the PD group, the stent was successfully delivered in 98% of cases (Table 2). Out of the 220 stents implanted, 93% were BeStent2: a 9 mm was used in 21% (DS) and 12% (PD), a 12 mm was used in 35 and 34%, and a 15 mm in 40 and 48%, respectively. Non-study stents were used in three patients with DS and in six patients with PD.
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The mean balloon pre-dilatation pressure for the PD strategy was 9.0±2.5 mmHg, with the maximum mean inflation pressure for successful stent deployment being higher for the DS (13.4±2.4 mmHg) group than for the PD (12.5±2.7 mmHg; P=0.013) group.
Overall, the total materials used were less for the DS strategy, which was predominantly due to less balloon usage (Table 2). Use of guide wires, number of stents, contrast agent, and mean radiation exposure time were similar between the two groups (Table 2).
Characteristics of cross-over lesions
A total of seven patients crossed from DS to PD. The target lesion was in LAD (n=3), RCA (n=3), and LCX (n=1), with all being morphologically eccentric and type B2. Five of the seven had moderate calcification. The lesion length was 0.6±3.9 mm, with a luminal diameter of 0.84±0.44 mm, and per cent stenosis of 68±18.
Procedural and in-hospital outcome
The pre- and post-procedural angiographic characteristics were similar between the two groups (Table 3). The post-procedure MLD was 2.79±0.45 mm for the DS group and 2.76±0.40 mm for PD (P=0.63) group. The null-hypothesis of non-equivalence could therefore be rejected (P=0.0003). With documentary IVUS evaluation, stent expansion was 89.5±17.5% with DS and 87.5±16.5% with PD (P=0.59) (Table 4). The minimum stent area was 7.89±1.75 mm2 with DS and 8.07±2.37 mm2 with PD (P=0.69). The FFR was 0.92±0.07 and 0.92±0.05, respectively (P=0.97), and was greater than 0.90 in 70% of patients in both groups.
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Six month angiographic and clinical outcomes
Angiographic data were available for 183 patients. By QCA, the MLD and late loss were similar in both groups. The angiographic in-stent binary restenosis rate was 7.4% after DS and 6.8% after PD (P=0.87) (Table 3). On the basis of the post-procedural IVUS examination, the predicted restenosis rate was expected to be 11% after DS and 13% after PD.10
A total of 20 MACE were reported in 19 patients on completion of the 6-month follow-up (Table 5), with MACE occurring in 9% with DS and 10% with PD. No deaths occurred in either group. The log-rank test on MACE-free survival curves showed no significant differences between the groups (P=0.82) (Figure 2).
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Revascularization of the target lesion was performed in six DS and five PD patients (P=0.77), with all being performed between 125 and 196 days after the index procedure. Surgical revascularization was required for one patient in each group, with target lesion being grafted for the PD patient only.
When comparing patients with post-procedural FFR 0.9 and <0.9, the per cent stenosis at follow-up was higher in those with FFR<0.9 when compared with FFR
0.9 (30.8±14.0 and 23.5±12.7%, respectively; P=0.02). The FFR measurement for those presenting with and without MACE was 0.88±0.03 and 0.92±0.06, respectively (P=0.07).
Comparing diabetic and non-diabetic patients, there was no significant difference in per cent stenosis (28.8±18.6 and 26.1±15.7%, respectively; P=0.36) and MACE (12 and 9%, respectively; P=0.77) at 6-month follow-up, with five diabetic and eight non-diabetic patients presenting with a binary restenosis (P=0.16).
The MLD post-stenting, binary restenosis, MACE, and need for in-stent post-dilatation for the four subgroups (DS with IVUS/FFR, DS without IVUS/FFR, PD with IVUS/FFR, and PD without IVUS/FFR) were statistically similar (Table 6).
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Discussion |
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An overall good and comparable procedural success rate was observed in both groups. The stent was successfully deployed in 94% of DS patients, with a final success rate of 97% when those who crossed to PD were included (Table 2). Furthermore, the need for additional post-stent procedures and the incidence of dissections were statistically similar between the groups.
MACE and restenosis
No death occurred during the course of this study. As documented in other studies,1315 no difference in MACE (DS=9%, PD=10%) or rate of in-stent restenosis (DS=7.4%, PD=6.8%) was observed. These findings hold even for diabetic vs. non-diabetic patients. Importantly, however, an overall lower MACE and restenosis rates than those observed in previous studies with bare-metal stents were observed.1315
We can only hypothesize about the factors that potentially contributed to the low MACE and restenosis rates observed following implantation of this non-drug eluting stent. The patient demographics are quite similar to most previously reported randomized trials, with nearly a third presenting with unstable angina and 20% of the patients having diabetes. The utilization of post-stent QCA to gauge the result (with post-deployment dilatation utilized when required) might have helped to optimize MLD, a critical determinant of late outcome.16 In addition, it is likely that the characteristics of the stent design used in this trial contributed to the observed results. The utilization of shorter stents (
57% of patients received a stent <15 mm), with its relatively low stent strut thickness (0.0850.095 mm), is a property that is possibly associated with reduced late loss.1719 Furthermore, the low overhang (
0.4 mm) of the delivery balloon from the stent edges may have resulted in reduced vessel trauma and dissection at the stent edges.
Clinical Implications
DS is safe and when utilized appropriately may result in reduced cost (reduced use of material). However, more complex lesions with calcification and low MLD are best pre-dilated prior to stenting.
The potential advantage of DS in reducing the risk of in-stent restenosis as suggested in experimental studies20,21 was not observed in this study. It has been suggested that, with DS, the undamaged remnant endothelial cells that remain between the stent struts regenerate, negating the need for smooth muscle cell proliferation.2 Perhaps the use of post-stent dilatation, that invariably tends to be at higher pressures, damages these remaining cells and potentially annihilates the initial advantage created by DS.
The overall procedural success, however, could be improved by ensuring adequate stent deployment and larger final MLD by the utilization of online QCA, IVUS, and FFR. As observed here, a post-procedure FFR 0.9 is associated with a reduced per cent stenosis at follow-up, with a trend towards lower MACE.22
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Conclusions |
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Appendix |
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Core laboratory for QCA and IVUS measurements: Cardialysis BV, Rotterdam, The Netherlands.
Clinical Event Committee: M. Vrolix, ZOL Campus St Jan, Genk and J. Vainer, University Hospital Maastricht.
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References |
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