CLINICAL RESEARCH: INTERVENTIONAL CARDIOLOGY
9-Month Clinical, Angiographic, and Intravascular Ultrasound Results of a Prospective Evaluation of the Axxess Self-Expanding Biolimus A9-Eluting Stent in Coronary Bifurcation LesionsThe DIVERGE (Drug-Eluting Stent Intervention for Treating Side Branches Effectively) Study
Stefan Verheye, MD, PhD*,*,
Pierfrancesco Agostoni, MD*,
Christophe L. Dubois, MD ,
Joseph Dens, MD, PhD ,
John Ormiston, MD ,
Stephen Worthley, MD||,
Brett Trauthen, MS¶,
Takao Hasegawa, MD#,
Bon-Kwon Koo, MD, PhD#,
Peter J. Fitzgerald, MD, PhD#,
Roxana Mehran, MD** and
Alexandra J. Lansky, MD**
* Antwerp Cardiovascular Institute Middelheim, Ziekenhuis Netwerk Antwerpen, Antwerp, Belgium
University Hospital Gasthuisberg, Leuven, Belgium
Oost-Limburg Hospital, Genk, Belgium
Auckland City Hospital, Auckland, New Zealand
|| Royal Adelaide Hospital, Adelaide, Australia
¶ Devax, Inc., Lake Forest, California
# Stanford University Medical Center, Stanford, California
** Columbia University Medical Center and Cardiovascular Research Foundation, New York, New York
Manuscript received November 19, 2008;
revised manuscript received December 8, 2008,
accepted December 10, 2008.
* Reprint requests and correspondence: Dr. Stefan Verheye, Antwerp Cardiovascular Institute Middelheim, Ziekenhuis Netwerk Antwerpen, Lindendreef 1, 2020 Antwerp, Belgium (Email: stefan.verheye{at}telenet.be).
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Abstract
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Objectives: This study sought to assess the safety and performance of the Axxess (Devax Inc., Lake Forest, California) self-expanding drug-eluting stent in coronary bifurcation lesions.
Background: Percutaneous treatment of coronary bifurcations is a predictor of adverse late outcomes, in part because of the lack of dedicated devices.
Methods: Patients with de novo bifurcation lesions were prospectively enrolled in a multicenter study. The Axxess stent was deployed at the level of the carina followed by additional sirolimus-eluting stents in the distal parent vessel (PV) and/or side branch (SB). All patients underwent clinical follow-up at 9 months; 150 were to receive control angiography and 76 were to receive intravascular ultrasound. The primary end point was the rate of major adverse cardiac events (MACE): a composite of death, myocardial infarction (MI), and target lesion revascularization (TLR). Secondary end points included in-segment restenosis, late loss, and percent neointimal volume obstruction.
Results: Overall, 302 patients were treated with 299 Axxess stents (99%). Additional stenting of 1 branch was performed in 21.7% of patients (17.7% PV, 4% SB), and of both branches in 64.7%. At 9 months, 99.3% of patients returned for clinical follow-up; from the angiographic and IVUS substudies, 93.3% and 89.4% returned. The cumulative 9-month MACE rate was 7.7% (0.7% death, 3.3% non–Q-wave MI, 1.0% Q-wave MI, 4.3% TLR). Subacute and late stent thrombosis occurred in 0.7% and 0.3% of patients. Total restenosis was 6.4% (3.6% PV, 4.3% SB), late loss was 0.20 ± 0.41 mm in the PV and 0.17 ± 0.34 mm in the SB. In the Axxess stent segment, percent neointimal volume obstruction was 4.3 ± 5.2%.
Conclusions: This prospective multicenter study confirms the safety and performance of the Axxess stent in bifurcation lesions. (Drug-Eluting Stent Intervention for Treating Side Branches Effectively; ACTRN12606000259549)
Key Words: coronary artery disease • Biolimus A9-eluting stent • bifurcation lesion • restenosis
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Abbreviations and Acronyms
| | IVUS = intravascular ultrasound | | MACE = major adverse cardiac event | | MI = myocardial infarction | | MLD = minimal luminal diameter | | PCI = percutaneous coronary intervention | | PV = parent vessel | | RVD = reference vessel diameter | | SB = side branch | | TLR = target lesion revascularization |
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Coronary bifurcation lesions are defined as stenoses involving 1 of the 3 primary epicardial coronary vessels and a branching vessel with a reference vessel diameter (RVD) of at least 2.2 mm (1). The percutaneous treatment of these lesions with stent implantation is associated with increased adverse clinical events and inferior angiographic outcomes, when compared with mid-vessel lesions (2,3). This is mainly because of suboptimal results in the side branch (SB). Despite the implementation of numerous techniques (T-stenting, V-stenting, kissing-balloon stenting, crush stenting, culotte stenting) to stent both branches, none of them, even in the drug-eluting stent era, has shown clinical and angiographic superiority to the single parent vessel (PV) stent technique with provisional T-stenting of the SB in case of dissection or residual severe disease (4–6).
Novel dedicated stents have recently been developed to provide easier access to the SB and to scaffold more effectively its ostium, matching the stent configuration more closely to the anatomy of the bifurcation. However, clinical data on these devices are still sparse (7).
The Axxess stent (Devax Inc., Lake Forest, California) belongs to this category of dedicated bifurcation lesion stents (8). It is a self-expanding drug-eluting stent, deployed at the level of the carina, which provides easy access to the distal branches that subsequently can be provisionally treated with percutaneous coronary intervention (PCI), depending on the disease status of these branches. The rationale behind this stent is to provide an anatomically tailored treatment of the bifurcation with maximum drug coverage and minimum overlap or deformation of the stent struts. The Axxess stent has been previously tested in clinical practice in the prospective multicenter Axxess Plus registry enrolling 139 patients, in whom, together with the Axxess stent, sirolimus- or paclitaxel-eluting stents were used as additional stents to optimize the procedure. The SB treatment was left at operator discretion, and stenting of the SB was performed in approximately one-half of the lesions. Post hoc analysis of lesions treated with stent deployment in the SB provided better procedural outcomes and better late results with <10% restenosis of the SB, compared with >20% SB restenosis after balloon-only angioplasty (9).
The current study was planned to expand these results in a broader population, keeping stricter protocol obligations for lesion treatment, such as the mandated use of sirolimus-eluting stents as additional stents for the PV and the SB if the residual diameter stenosis exceeded 30%.
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Methods
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The DIVERGE (Drug Eluting Stent Intervention for Treating Side Branches Effectively) study is a prospective multicenter registry. The local ethics committee of every hospital participating in the study approved the study design. All enrolled patients provided written informed consent before the index procedure.
Patient population.
The study population consisted of male and female patients, 18 to 80 years of age, with documented stable or unstable angina or positive functional study, identified for elective PCI of a de novo native coronary artery bifurcation lesion in a major coronary artery in which either the PV or the SB had at least a 50% diameter stenosis. The RVD by visual estimate had to be 2.75 to 3.75 mm in the PV and  2.25 mm in the SB. The lesion length had to be  25 mm in the PV, with 10 mm proximal to the carina. The SB ostium needed to be located >12 mm from the left main coronary artery. The angle between the distal PV and the SB had to be <70°. The protocol allowed concurrent treatment of 1 additional lesion, provided it was located in a different primary epicardial vessel and was successfully treated before the bifurcation lesion.
Clinical exclusion criteria were: pregnant female; myocardial infarction (MI) within the previous 72 h; cardiogenic shock; creatine kinase level above the upper limit of normality at the time of the procedure; documented left ventricular ejection fraction <30%; cerebrovascular accident or gastrointestinal/genitourinary bleeding within the past 6 months; renal insufficiency (creatinine >2.0 mg/dl); thrombocytopenia (platelet count <105/mm3); anemia (hemoglobin <10 g/dl); current or planned use of oral anticoagulant agents; contraindications to aspirin, clopidogrel, heparin, or contrast agents; known sensitivity to sirolimus, stainless steel, titanium, nickel; life expectancy <2 years; or current participation in another investigational drug or device study. Angiographic exclusion criteria were: previous PCI in the target vessel <9 months from the index procedure; left main stenosis; severe calcification, excessive tortuosity, or presence of intraluminal thrombus by visual estimation; and pre-treatment of the target lesion with any unapproved device or atherectomy or laser (cutting balloon was allowed).
Study device.
The Axxess stent is made from a nickel-titanium alloy (nitinol) in the austenitic (superelastic) phase. The stent elutes Biolimus A9 (Biosensors International, Ltd., Newport Beach, California), a derivative of sirolimus, with similar antiproliferative properties (10). Drug release is mediated by a bioabsorbable polylactic acid-based polymer (which is metabolized over time into carbon dioxide and water). This drug-polymer coating is applied to the abluminal surface of the stent. The nominal drug loading is 22 µg/mm of stent length for all sizes.
The procedure for stent placement typically requires wiring of both branches of the lesion, followed by successful pre-dilation of the PV and the SB to provide space for the self-expanding stent. The stent is kept in place on the delivery system by a covering sheath, which is clearly visible under fluoroscopy. The stent is deployed by gently retracting the sheath once the stent is in place at the level of the carina. The stent has 1 radiopaque marker at the proximal edge and 3 markers at the distal edge to assist in accurate positioning and deployment at the target site (Fig. 1). The Axxess stent's conical shape and self-expanding property allow it to cover the irregular anatomy of a bifurcation at the level of the carina up to bifurcation angles of 70°. The stent is unique in that it spans both the PV and the SB without obstructing access to either, and allows easy passage of additional stents in both branches. If needed, additional stents are implanted to complete lesion coverage. Accurate distal stent position is aided by the presence of the distal markers on the Axxess stent. In this study a small amount (1 to 2 mm) of overlap was targeted. Post-dilation focus is on the distal branch stents, with attention to ensure full deployment at the overlap segments. Because the branch vessel stents are implanted distal to the carina, flow to the SB is unobstructed, and no strut deformation is induced by post-dilation (Fig. 2).
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Figure 2 Final Placement Angiogram
(A) Contrast-filled angiogram shows the Axxess stent in the proximal left anterior descending artery (LAD) (left anterior oblique artery view with 1 marker at the level of the mid-LAD and 2 markers in the diagonal branch) and an additional Cypher in the mid-LAD. (B) Stent boost image shows an enhanced contrast-negative stent visualization.
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Procedural protocol and follow-up.
After percutaneous access was obtained, heparin was administered to maintain an activated clotting time >250 s (or >200 s if glycoprotein IIb/IIIa inhibitors were given). Eligible patients underwent mandatory pre-dilation of the PV and, at operator's discretion, of the SB. At this point, placement of the Axxess self-expanding stent at the site of the bifurcation was performed. The stent diameters available for the study were 3.0 and 3.5 mm, with lengths of 11 or 14 mm. All patients who had the study stent introduced into the vasculature were considered enrolled in the DIVERGE study. Depending on the disease status of the distal PV and distal SB, adjunctive stenting, in overlap of the distal edge of the Axxess stent and extending into the branch vessels, was permitted. An optimal angiographic outcome was strongly recommended to obtain no residual stenosis at the end of the procedure. Thus, additional stents were implanted if there was a residual stenosis of >30% in any segment of the bifurcation. The protocol mandated the use of Cypher sirolimus-eluting stents (Cordis, Johnson & Johnson, Warren, New Jersey) for this purpose. Bail-out stenting with additional Cypher stents was allowed in case of dissection or incomplete lesion coverage. The first 150 patients enrolled were allocated into an angiographic substudy, whereas the first 76 patients at selected sites were allocated into an intravascular ultrasound (IVUS) substudy. The IVUS examination was performed at the end of the procedure according to standard protocols using a 20 to 40 MHz ultrasound probe with motorized pullback (speed: 0.5 mm/s). Aspirin (80 mg/day) was given daily and clopidogrel (loading dose of at least 300 mg before or immediately after the procedure and 75 mg/day thereafter) was administered for at least 6 months in all patients. A protocol amendment of October 2007 mandated clopidogrel for 12 months post-procedure according to the updated American Heart Association/American College of Cardiology/Society for Cardiovascular Angiography and Interventions recommendations (11). Serial blood samples for creatine kinase and creatine kinase-MB were routinely obtained 8 and 16 h after the intervention.
Patients were evaluated clinically at 1, 6, and 9 months after the procedure. Control angiography and IVUS were performed after the 9-month visit, or earlier if there were recurrent symptoms. If restenosis was not found in an angiography performed <4 months post-procedure, a second angiography was done at 9 months.
Quantitative coronary angiography and IVUS analysis.
Digital coronary angiograms were analyzed offline by an independent core laboratory, using a validated automated edge detection system (QAngioXA version 7.1.14.0, Medis, Leiden, the Netherlands). Matched views were selected for angiograms recorded before and immediately after the intervention and at follow-up. Bifurcation lesions were classified according to the Medina classification (12). Angiographic measurements were made both in the stent and in the stented segment (defined as the whole stented tract plus the 5-mm edges proximal and distal to the stent) during diastole using the contrast-filled guiding catheter for magnification calibration. Lesion RVD, minimal luminal diameter (MLD), percent diameter stenosis, and length were obtained at baseline for both the PV and the SB. The MLD and diameter stenosis were evaluated at the end of the procedure and at follow-up for the in-segment and -stent sections in both the PV and the SB, and specifically only for the Axxess stent. Acute gain was defined as the difference between the MLD at the end of the intervention and the MLD at baseline. Late lumen loss was calculated as the difference in MLD between measurements immediately after the procedure and at follow-up. Binary angiographic restenosis was defined as diameter stenosis 50% by quantitative coronary angiography at the follow-up angiogram.
Quantitative and qualitative IVUS analyses were performed offline by an independent core laboratory using validated software (echoPlaque, INDEC Medical Systems, Santa Clara, California), allowing semi-automated detection of luminal and stent boundaries in reconstructed longitudinal planes. Volumetric quantitative IVUS analysis was obtained for vessel, stent, and lumen. Serial volumetric measurements were done if baseline and follow-up runs were matched and of adequate quality. Neointimal volume index was computed as the difference between stent volume and lumen volume per millimeter of stent. Percent volume obstruction was calculated as the ratio between the neointimal volume and stent volume x 100. Incomplete stent apposition was defined as 1 or more stent struts clearly separated from the vessel wall with evidence of a void behind the strut in a vessel segment not associated with any SBs.
End points and definitions.
The primary end point of the study was the rate of major adverse cardiac events (MACE) at 9 months; MACE were defined as any of the following: cardiac or noncardiac death, Q-wave or non–Q-wave MI, and ischemia-driven target lesion revascularization (TLR). Secondary angiographic end points included binary restenosis and late lumen loss, evaluated in-segment, in the stented area, and in the Axxess stent only. Secondary IVUS end points were neointimal tissue volume, percent volume obstruction within the study device, and incidence of late-acquired stent incomplete apposition and strut tissue coverage at 9 months. Cardiac death was defined as death caused by acute MI, congestive heart failure, cardiac perforation, arrhythmia, cerebrovascular accident within 30 days of the index procedure, or complication of the index procedure (including bleeding, vascular repair, transfusion reaction, or bypass surgery) or any death in which a cardiac cause could not be excluded. Noncardiac death was defined as a death not attributable to cardiac causes. Myocardial infarction was defined as: 1) Q-wave MI when chest pain or symptoms consistent with myocardial ischemia and new pathological Q waves in 2 or more contiguous electrocardiograph leads were present; and 2) non–Q-wave MI if creatine kinase was elevated >2x the upper laboratory normal with the presence of elevated creatine kinase-MB in the absence of new pathological Q waves. The TLR was considered ischemic, defined as repeat revascularization (PCI or bypass surgery) in the presence of a positive functional study for ischemia because of restenosis of any portion of the target lesion, or TLR of a 70% diameter stenosis anywhere within the target lesion. In this study, the target lesion was defined as any treated segment of the bifurcation—PV or SB—plus a border of 5 mm. Stent thrombosis was defined according to the Academic Research Consortium criteria (13). An independent clinical events committee adjudicated all of the clinical events, and an independent data safety monitoring board reviewed clinical data periodically throughout the study.
In addition, several procedure parameters were assessed. Primary device success was defined as deployment of the Axxess stent without system failure or device-related complication. Lesion success was defined as attainment of <50% residual stenosis of the target lesion using the assigned device or any percutaneous method. Procedure success was defined as attainment of a final lesion (angiographic) success in the absence of any in-hospital MACE. Finally, Axxess stent placement was evaluated independently by the core laboratory. It was considered accurate if 1 of the 3 distal markers of the stent was clearly in each of the PV and SB, respectively, or if 2 markers were in the triangle formed by the carina and the ostia of the branch vessels.
Statistical analysis.
All analyses were conducted according to the intention-to-treat principle. Continuous data are expressed as mean ± SD or as median [interquartile ranges], as appropriate, whereas dichotomous data are summarized as frequencies.
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Results
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Between June 2006 and October 2007, 302 patients were enrolled in the DIVERGE study (Fig. 3).
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Figure 3 Flow Diagram of Subjects' Progress Through Phases of the DIVERGE Study
DIVERGE = Drug-Eluting Stent Intervention for Treating Side Branches Effectively; FU = follow-up; IVUS = intravascular ultrasound.
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Study population and the procedural and in-hospital outcomes.
Baseline clinical characteristics of the patients are shown in Table 1, whereas the angiographic and procedural characteristics of the lesions treated are presented in Tables 2 and 3. A majority of the lesions were categorized as true bifurcations (77.4%) and had presence of disease in the SB (78.1%) according to the Medina classification system. At baseline, mean lesion length and RVD by quantitative coronary angiography were 14.6 and 2.93 mm, respectively, in the PV, and 6.9 and 2.3 mm in the SB.
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Table 3 Quantitative Coronary Angiography Analysis of the Lesions Treated in the Total Cohort and in the Angiographic Subgroup
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The Axxess stent was placed in 299 of 302 patients (99.0%). The placement was scored as optimal by the angiographic core laboratory in 93% of cases. In 3 patients, the Axxess stent was withdrawn because of anatomical configurations outside of the study inclusion criteria. In 2 additional cases, the Axxess stent was not placed at the bifurcation, thus primary device success was obtained in 297 of 302 patients (98.3%). These lesions were successfully treated with other techniques.
Additional stents were placed in the distal branch vessels depending on disease distribution, resulting in the patterns shown in Figure 4. In keeping with the prevalence of diseased SBs in this study, the most frequent treatment pattern was for both branch vessels to be stented (64.7%), but in several cases single distal stents were placed in the PV (17.7%) or the SB (4.0%). Post-dilation was performed in 85.8% of cases to a mean inflation pressure of 12.5 ± 3.2 atm.
Lesion (angiographic) success was obtained in 300 of 302 patients (99.3%). No deaths, TLR, or stent thrombosis occurred during hospitalization. The rate of periprocedural non–Q-wave MI was 3.0%, accounting for all in-hospital MACE. One of these was caused by periprocedural occlusion of the nonstented SB, because of untreatable dissection. Thus, the procedure success rate was 96.7%.
30-day and 9-month clinical outcomes.
Clinical events are presented in Table 4. Between the end of the hospitalization and the first month after treatment, subacute stent thromboses resulted in 2 Q-wave MIs (both occurring on day 4 after the index procedure and under double antiplatelet therapy). Both patients underwent urgent percutaneous revascularization, but 1 event was fatal. There was 1 ischemia-driven TLR, so that the overall rate of 1-month MACE was 4.0%. At 9 months, clinical follow-up was available in 300 patients (99.3%). Two patients withdrew consent for further follow-up at 6 months: 1 was event-free, whereas the other experienced a TLR after 3 months. The cumulative 9-month MACE rate was 7.7%, including 0.7% death, 4.3% MI, and 4.3% TLR. Between 1 and 9 months, 1 cardiac death was recorded at 8 months in a patient who underwent elective bypass surgery (with proven in-stent restenosis of both the PV and the SB and additional de novo coronary lesions). One Q-wave MI, caused by late stent thrombosis, occurred in a patient 7 months after the index procedure, 1 month after clopidogrel discontinuation. An additional non–Q-wave MI was caused by iatrogenic total occlusion of the distal target vessel during the planned 9-month control angiography and IVUS (which showed a good result of the index PCI) because of embolization of thrombotic material from the guiding catheter. Both patients were successfully treated with PCI. Finally, there were 8 additional percutaneous TLRs, all with proven restenosis (1 occurred in a patient who did not receive the Axxess stent, but rather a bare metal stent). Of interest, among the total 13 cases of TLR, 6 (46.1%) were PV restenoses (with or without involvement of the SB), 4 (30.8%) were driven exclusively by SB restenosis, and 3 (23.1%) were stent thromboses.
Quantitative coronary angiography and IVUS outcomes.
Of the 150 patients included in the angiographic substudy, 140 (93.3%) received the planned control angiogram. Angiographic data are presented in Table 3. In-bifurcation restenosis occurred in 9 patients (6.4%): 2 patients had restenosis in both the PV and the SB (1 total occlusion starting just before the Axxess stent and 1 multifocal restenosis in 2 sites, 1 proximal to the Axxess stent and 1 in the SB stent), 3 patients had PV restenosis (1 proximal to the Axxess stent, and 2 in the PV stent after the bifurcation), 4 patients had SB restenosis (including also the patient with the total occlusion of the nonstented SB causing a periprocedural MI at baseline).
Of the 76 patients included in the IVUS substudy, 68 (89.4%) received the planned control IVUS. Baseline and follow-up 3-dimensional volumetric analyses were available for the Axxess stent in 54 and 56 patients, respectively. Of the 68 follow-up patients, serial 3-dimensional analysis for the Axxess stent was available in 51 patients, and serial qualitative analysis for incomplete stent apposition was possible in 62 Axxess stents.
The IVUS data are presented in Table 5. Follow-up neointimal hyperplasia obstruction within the Axxess stent in terms of percent of stent volume was 4.3 ± 5.2%. The self-expanding Axxess stent increased in mean volume index from the procedure to follow-up from 7.4 ± 2.0 mm3/mm to 9.6 ± 2.6 mm3/mm of the stent, leading to a net increase in lumen volume index from 7.3 ± 2.0 mm3/mm to 9.2 ± 2.5 mm3/mm.
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Discussion
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The use of the Axxess Biolimus-eluting stent for the treatment of complex bifurcation lesions resulted in a high procedure success rate (96.7%), a low all-cause cumulative 9-month MACE rate (7.7%, including 3.0% periprocedural non–Q-wave MI), and a low 9-month TLR rate (4.3%). Systematic angiographic follow-up of 140 patients showed an overall in-segment restenosis rate of 6.4% inclusive of both PV and SB. The IVUS analysis showed marked suppression of neointimal hyperplasia within the stent and a significant increase in lumen volume over time within the Axxess stent. In addition, there are several methodological strengths in this study that reinforce the validity of the results obtained: prospective enrollment, multicenter setting, total and independent monitoring of data acquisition, independent evaluation of the events, enrollment of one of the largest published cohorts of patients with bifurcation lesions, and focus on a drug-eluting stent specifically dedicated for bifurcations.
The design of the Axxess stent allows conformability of the stent to the vessel wall without deformation of the struts and with easy access to both branches for additional PCI. The placement technique is novel, and requires thorough pre-dilation and careful attention to marker position within the bifurcation for optimal positioning. In this study, optimal placement was obtained in 93% of patients. Of the suboptimal placements, a successful angiographic outcome was obtained in all cases.
The advantage of this technique is that additional stents can be placed in either or both distal segments provisionally, depending on angiographic appearance, without distortion from their cylindrical shape. This allows the length and diameter of distal stents to be selected for a precise fit to the lesion. Because the Axxess stent covers the ostium of the branch vessels, distal stents are placed at or slightly distal to the carina, thus eliminating ostial stent strut obstruction and minimizing stent strut overlap. Thus, techniques used to compress or distort obstructing stent struts in other bifurcation techniques, such as kissing-balloon dilation, are eliminated.
Comparison with the current evidence.
Despite the fact that there is no firm agreement on the standard treatment of bifurcation lesions, there is some consensus that a strategy based on single stenting of the PV with provisional stenting of the SB is recommended; however, neither an advantage nor a disadvantage of stenting both branches has ever been shown.
There are a few studies comparing simple and complex strategies for bifurcation lesions. The NORDIC trial compared a single PV sirolimus-eluting stent strategy (with kissing-balloon angioplasty of the SB only if the flow was impaired, but not if there was a residual angiographically severe lesion) to a strategy of stenting both the PV and the SB with sirolimus-eluting stents (in this case different techniques were allowed). This trial showed good clinical results, with low 6-month TLR rates in both arms (1.9% in the PV stent arm and 1% in the PV + SB stent arm), not influenced by the angiographic follow-up, performed on purpose at 8 months. However, the overall MACE rates evaluated at 6 months (2.9% in the PV stent arm and 3.4% in the PV + SB stent arm) did not include the periprocedural MI, which were as high as 8% in the PV stent group and 18% in the PV+SB stent group. Moreover, post-procedural blood samples for myocardial enzymes were not available in the whole cohort, but only in around 68% of the patients, thus a risk of underestimation of the event rate should also be considered. Furthermore, the angiographic restenosis rate, evaluated at 8 months, remained elevated in both groups (22.5% in the PV stent group and 16% in the PV + SB stent group), mainly driven by the SB restenosis (4).
Another single-center trial compared the single PV sirolimus-eluting stent technique (with mandated kissing-balloon stenting in all patients) and the routine T-stenting technique also with sirolimus-eluting stents, still showing 1-year MACE rates of 12.9% and 11.9%, respectively, and 9-month restenosis rates of 12.5% and 13.5%, respectively (6).
In general, according to these trials, no major differences were noted if balloon-only angioplasty or stenting were performed in the SB, and the angiographic restenosis rate still remained above 10% with all of the techniques used. A general weakness of these studies is that a specific strategy for the SB treatment was mandated by the protocol, rather than by vessel diameter or presence of disease. On the contrary, the first-in-man Axxess Plus study, despite its nonrandomized design, suggested improved angiographic outcomes in the SB if it was treated with a drug-eluting stent (with a restenosis rate of 7.9%) as compared with balloon angioplasty (with a restenosis rate of 25%) (9). However, stenting of the SB in the Axxess Plus study occurred only in one-half of the cohort enrolled. In the DIVERGE study, stents were used to obtain an optimal angiographic result in the bifurcation in the same way as would be done for a midvessel lesion. Using this approach, a single Axxess stent was used in 12% of lesions, an additional stent was added in 21.5% of lesions, and a stent was added to both branches is 65% of lesions. The rationale behind this approach was to cover any diseased part of the bifurcation with both stent and drug and to obtain an angiographically optimal outcome at the end of the procedure. This strategy resulted in a TLR rate of 4.3%, a total bifurcation restenosis rate of 6.4%, and a SB restenosis rate of 4.3%.
Despite the use of multiple stents to obtain complete coverage of the lesion in the bifurcation (seen until now as a possible risk factor for stent thrombosis [5]), the Axxess strategy may offer beneficial effects in terms of low stent thrombosis rate as was seen in this study: subacute and late stent thrombosis rates according to Academic Research Consortium definitions were 0.7% and 0.3%, respectively (13). One mechanistic explanation could be the combination of the self-expanding properties of the study device with local drug delivery resulting in a large proximal PV lumen, coupled with lack of strut deformation, minimization of stent overlap, and undisturbed flow into the distal branch vessels.
Thus, it seems that dedicated stenting technology for bifurcation lesions in combination with site-specific drug delivery offers an excellent outcome in terms of clinical, angiographic, and IVUS end points. Based on these findings, there seems to be no penalty for stenting the SB, but it remains to be seen in a randomized manner whether this strategy is superior to provisional stenting.
Limitations of the technique are the angulation (>70° angulation should be avoided) and the use of multiple stents (which may also be advantageous given the results), yet angiographic analysis did not show any increase of restenosis at overlapping stent segments.
Study limitations.
The major limitation of this study is the single-arm, nonrandomized setting. Despite the encouraging results shown in the DIVERGE study, a randomized trial is warranted to prove the angiographic and clinical superiority of the Axxess stent versus current bifurcation stenting techniques.
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Appendix
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For a complete list of participating DIVERGE Investigators, please see the online version of this article.
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Footnotes
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Dr. Ormiston is on the advisory board of Devax, Inc., Abbott Vascular, and Boston Scientific. Mr. Trauthen is an employee of Devax, Inc. Dr. Mehran has received research grants to CRF from Abbott Vascular, The Medicines Co., Boston Scientific, Medtronic, and Cordis; and honoraria from The Medicines Co., Lily/Daiichi Sankyo, Cordis, Boston Scientific, Abbott Vascular, Medtronic, and Bracco. Dr. Lansky has received research support (unrestricted grant) from Devax, Inc. The results of this study were presented at the 2008 Transcatheter Cardiovascular Therapeutics (TCT) Conference Proceedings (Late Breaking Clinical Trial session), Washington, DC, October 12 to 17, 2008.
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References
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