Original Contribution

COmplex Bifurcation Lesions: RAndomized Comparison of Modified-T Stenting vs Reconstruction With Self-Expanding Stent and Bioresorbable Scaffold: COBRA II

Johan Bennett, MD, PhD1,2;  Keir McCutcheon, MD, PhD1,2;  Maarten Vanhaverbeke, MD, PhD1;  Ruben Pauwels, MD1;  Tom Adriaenssens, MD, PhD1,2;  Peter Sinnaeve, MD, PhD1,2;
Walter Desmet, MD, PhD1,2;  Christophe Dubois, MD, PhD1,2

Johan Bennett, MD, PhD1,2;  Keir McCutcheon, MD, PhD1,2;  Maarten Vanhaverbeke, MD, PhD1;  Ruben Pauwels, MD1;  Tom Adriaenssens, MD, PhD1,2;  Peter Sinnaeve, MD, PhD1,2;
Walter Desmet, MD, PhD1,2;  Christophe Dubois, MD, PhD1,2

Abstract

Objectives. To evaluate the role of a double bioresorbable vascular scaffold (BVS) strategy in coronary bifurcations, alone or in combination with a dedicated bifurcation device. Methods. COBRA II is a prospective, single-center, randomized controlled trial. Patients were randomized to treatment with biolimus-eluting Axxess bifurcation device (Biosensors) in combination with Absorb BVS (Abbott Vascular) or a modified-T strategy using Absorb BVS. Optical coherence tomography (OCT) was performed post procedure and at 30 months. The primary endpoint was change in minimal luminal area (MLA) on OCT from baseline to 30-month follow-up. Clinical endpoints included major adverse cardiac event (MACE) rate. Results. From February 2016 to February 2017, a total of 15 patients with complex coronary bifurcation lesions were randomized to Axxess (n = 8) or modified-T strategy (n = 7). Procedure success rate was 100%. At 30-month follow-up, MLAs were significantly smaller than post procedure in proximal main vessel (MV), ostial distal MV, and ostial side branch (SB) after modified-T (mean difference, -3.1 ± 1.3 mm2 [P<.001]; -2.1 ± 1.0 mm2 [P<.01]; -2.1 ± 1.4 mm2 [P=.03], respectively) and in ostial distal MV and ostial SB after Axxess (-2.1 ± 0.8 mm2 [P<.001]; -1.6 ± 0.7 mm2 [P<.01], respectively), while in proximal Axxess segment, the MLA remained stable (-0.1 ± 0.0; P=.93) and significantly larger than modified-T, mainly due to a smaller neointimal area (1.8 ± 0.7 mm2 vs 3.2 ± 0.6 mm2; P<.001). Acute BVS strut discontinuities were observed in 53%, and late intraluminal dismantling was seen in 38% of patients. At 3 years, 1 MACE and no scaffold thromboses were observed. Conclusions. In this serial imaging bifurcation study, BVS luminal dimensions were significantly smaller at 30 months, with acute strut discontinuities and late Intraluminal dismantling frequently observed.

J INVASIVE CARDIOL 2021;33(4):E281-E293. Epub 2021 March 4. 

Key words: bioresorbable scaffolds, coronary bifurcation, dedicated devices, optical coherence tomography


Fully bioresorbable vascular scaffolds (BVSs) were designed to mitigate the potential long-term adverse effect of metallic drug-eluting stent (DES) implantation.1 These devices offer transient scaffolding of the dilated coronary vessel to prevent acute recoil and abrupt vessel closure, elute an antiproliferative drug to prevent neointimal hyperplasia, and ultimately disappear through bioresorption. The polymeric bioresorbable everolimus-eluting Absorb BVS (Abbott Vascular) received its CE mark in 2010 and was approved by the United States Food and Drug Administration on the basis of reported non-inferiority of the BVS to the cobalt-chromium everolimus-eluting stent (CoCr-EES) at 1 year in pivotal trials.2 However, long-term results demonstrated higher risks for device thrombosis with the BVS than with CoCr-EES during the time period when bioresorption was still ongoing, culminating with the reporting of the AIDA trial in 2017, which observed a significantly increased risk of scaffold thrombosis with Absorb BVS compared with conventional DES (3.5% vs 0.9%, respectively; P<.001) in a contemporary patient cohort.3,4 Shortly after this, the safety concerns raised by these results forced the manufacturer to discontinue marketing the device. 

In 2015, at the time of conception of the COBRA II study, there was substantial interest in evaluating the Absorb BVS in complex bifurcation treatment. This technology was felt to offer a particular advantage compared with metallic DES, ie, the restoration of vessel patency without permanent foreign material, which theoretically provides a nidus for stent-related ischemic adverse events.5 Given the concerns that the integrity of polymeric scaffolds may be compromised during bifurcation procedures, the authors agreed with the position of the European Bifurcation Club (EBC), which stated that the use of Absorb BVS in complex bifurcation lesions should only be performed in the setting of a clinical trial.6 Based on an in vivo multimodality imaging study, we identified modified-T (mod-T) stenting as the most promising fully BVS 2-scaffold strategy.7 We therefore designed the COBRA II bifurcation study with the objective of assessing the acute performance and long-term vessel healing with the mod-T stenting technique vs an approach combining BVS with a dedicated metallic drug-eluting bifurcation stent. To our knowledge, this is the only randomized controlled trial performed to investigate the safety, feasibility, and performance of BVS in complex coronary bifurcations.

Active enrollment of patients was prematurely halted in early 2017 because of apprehension regarding the increased risk of scaffold thrombosis with the BVS. Here, we present the acute and 30-month findings in these patients in order to contribute to future improvements in bioresorbable scaffold technology and the use of BVS in more complex interventions, such as true bifurcation lesions.

Methods

Study designs and population. The COBRA II study is a prospective, randomized, controlled, single-center trial (NCT02628288). The rationale and design of the study have been previously published.8 After providing informed consent, patients identified for elective percutaneous coronary intervention (PCI) of de novo and true native coronary bifurcation lesions (Medina classification 1,1,1/1,0,1/0,1,1) were randomized to bifurcation treatment with the self-expanding biolimus-eluting Axxess bifurcation device (Biosensors International) combined with additional BVS in the branches of the bifurcation (Axxess group) or to the 2-stent mod-T stenting technique with Absorb BVS (mod-T group). The required reference vessel diameter (RVD) by visual estimate was 2.75-3.75 mm in the proximal main vessel (MV) and >2.5 mm in the side branch (SB). Full inclusion and exclusion criteria have been detailed.8 

Procedural protocol, devices, and chosen implantation techniques. After mandatory predilation, patients were randomly assigned to the Axxess group or mod-T group through an interactive voice response system (IVRS) via an independent entity (Leuven Coordinating Center), using a centralized computer-generated random sequence (Figure 1). Characteristics of the dedicated Axxess bifurcation system and Absorb BVS have been previously described,8 with strut thickness displayed in Figure 1. In this study, the treatment strategy with Axxess is complemented by additional implantation of Absorb BVS in each of the distal branches, aiming for 1-2 mm overlap with the dedicated device, using a V-stenting technique, with the aim of reducing the potential for compromise of the BVS integrity since no scaffold sidehole dilation or aggressive postdilation strategies are required. In addition, the combination of the Axxess bifurcation device and Absorb BVS in the distal branches would result in optimal scaffolding of the bifurcation, with a carina free of struts as well as low angiographic restenosis rates and complete endothelialization in the long term due to the full bioresorption of the BVS in the branches.

The mod-T stenting technique is a modification of the technique described by Van Mieghem et al and is a single-kiss mini-crush.9 It consists of stenting 1 branch (usually the SB) of the bifurcation lesion with an Absorb BVS with slight protrusion (1-2 mm) of the scaffold into the MV, followed by crushing the protruding scaffold segment with a balloon. Subsequently, the second Absorb BVS is expanded in the MV, followed by proximal optimization using an appropriately sized NC balloon (≤0.5 mm larger than the MV-BVS), finally followed by rewiring of the SB. The procedure is completed by kissing-balloon dilation using a mini-kiss technique where the SB balloon is almost entirely in the SB with only minimal protrusion into the MV when kissing (at low pressure) is performed, therefore preventing damage to the proximal scaffold while still optimizing the carina. The mod-T stenting technique with Absorb BVS was chosen based upon results of a multimodality imaging study in an in vivo rabbit aorta-iliac bifurcation model.7 In this technique, there is a minimal layer of double scaffold struts and the SB is stented before the MV, avoiding the need to pass and deploy one scaffold through another scaffold, thereby reducing potential damage to the scaffold integrity.

After completion of the bifurcation treatment and final angiography, intracoronary nitroglycerin was administered and optical coherence tomography (OCT) examinations were performed using the Optis system (pullback speed, 18 mm/s) with DragonFly Duo catheters (St. Jude Medical).

Antiplatelet regimen and follow-up. Dual-antiplatelet therapy (DAPT) was administered for at least 30 months in all patients (until final angiography). All patients taking the aspirin/clopidogrel combination therapy underwent VerifyNow P2Y12 testing (Kordia Life Sciences) prior to index PCI. In “poor responders,” clopidogrel was replaced by ticagrelor to ensure adequate inhibition of platelet aggregation.

Patients underwent clinical follow-up at 1, 6, and 12 months after inclusion, and annually thereafter up until 3 years. Angiographic follow-up, with OCT examination of the target bifurcation, was performed at 30 months.

Primary and secondary endpoints. The primary endpoint of the study was change in minimal luminal area (MLA) from baseline to 30 months per predefined bifurcation segment, as assessed with OCT. The predefined bifurcation segments were: (1) proximal MV segment, defined as 5 mm segment proximal to the bifurcation segment; (2) bifurcation segment, defined as OCT frames on MV pullback from the carina point to the most proximal visible SB frame); (3) ostial distal MV segment, defined as OCT frames starting from the carina point and extending 3 mm distal into the distal MV; and (4) ostial SB segment, defined as OCT frames starting from the carina point and extending 3 mm distal into the SB.

Secondary OCT endpoints included change in MLA from baseline to 30 months in the other predefined bifurcation segments as detailed previously;8 other secondary OCT endpoints were lumen and device area, as well as neointimal thickness and area. Angiographic endpoints consisted of binary restenosis (>50% diameter reduction) and late lumen loss (LLL), evaluated per subsegment (proximal MV, distal MV, and SB) as well as combined.

Clinical endpoints and definitions. The clinical endpoints of the study are reported for descriptive purposes only and include the major adverse cardiac event (MACE) rate and the components of all-cause death, target-vessel revascularization (TVR), non-target vessel revascularization (non-TVR), and stent thrombosis. MACE is defined as any of the following: cardiac death, myocardial infarction (MI), and ischemia-driven target-lesion revascularization (TLR). Definitions of clinical endpoints have previously been described.8

Quantitative coronary angiography (QCA) and OCT analysis. Detailed analysis methodology for both QCA and OCT in bifurcated vessel segments has previously been reported by our group.10,11 Briefly, digital coronary angiograms were analyzed blindly offline by the local core lab, using a validated automated edge-detection system (QAngio XA). Matched views were selected for angiograms recorded before and immediately after the intervention and at follow-up. Measurements were performed and results reported according to the consensus statement of the EBC.12

Quantitative and qualitative OCT analyses were performed blindly offline by the local core lab. OCT images of stented/scaffolded segments, performed at the end of the index intervention, were analyzed with regard to stent/scaffold strut apposition, free-floating struts, degree/number of double strut layers, acute structural rupture, position of scaffold markers, and presence of thrombus. Thirty-month OCT imaging endpoints included mean and minimal stent/scaffold diameter, percentage of uncovered struts, percentage of malapposed struts, mean neointimal hyperplasia thickness, and area and presence of intraluminal defects. A malapposition distance >0 was the criterion of malapposition. Uncovered struts were defined as those with any part of the strut visibly exposed to the lumen, while covered struts were those with a layer of tissue visible over all of the reflecting surfaces. Frequency of acute disruption and late discontinuities were assessed according to the published methods.13 Acute structural strut rupture was defined by the presence of at least 1 of the following in at least 1 cross-section: (1) if 2 struts overhung each other in the same angular sector of the lumen perimeter, with malapposition (overhung strut) or without malapposition (stacked strut); or (2) if there were isolated strut(s) located without obvious connection with other surrounding struts in 2-dimensional OCT. Strut discontinuities with malapposed and/or uncovered struts were further classified as intraluminal scaffold dismantling (ISD).13 

For OCT endpoint analysis, device area and derived measures are based on abluminal stent contours. Quantitative assessment of OCT was performed separately in 4 bifurcation segments (proximal MV, distal MV, and SB at 1 mm intervals and bifurcation core at 0.3 mm intervals), while qualitative assessment of acute disruption and/or late discontinuities was performed frame by frame.

Statistical analysis. Due to the exploratory nature of this study, no formal sample size calculation was performed. Continuous data are summarized by their mean, standard deviation, minimum, Q1, median, Q3, and maximum. Categorical data are presented by frequency and percentage. Baseline characteristics are compared between randomized groups using a t-test or Mann-Whitney U-test for continuous variables and a Chi-squared or Fisher’s exact test for categorical variables. Event-free survival was assessed using the log-rank test. The primary analysis set of interest is the full analysis set (FAS), which consists of all randomized patients who have OCT measurements at 30 months available. All statistical tests are 2-sided and assessed at a 5% significance level.

Further details of the primary and secondary endpoint analysis performed have been previously described.8

Results

Between February 2016 and February 2017, a total of 15 patients were randomized to bifurcation treatment with the Axxess combined with additional BVS (n = 8) or to mod-T stenting technique with Absorb BVS (n = 7). Due to enforced early discontinuation of the study, the planned 60 patients could not be enrolled. Baseline patient characteristics are presented in Table 1. The target bifurcation was left anterior descending/diagonal in 12 cases, while 3 patients were treated for lesions in the left circumflex/marginal bifurcation. Bifurcation lesion and procedural characteristics are presented in Table 2. All patients had a true bifurcation lesion (Medina 1,1,1 or 0,1,1). QCA measurements before PCI are presented in Supplemental Table S1 and show similar RVD and total lesion length in both treatment groups.

Procedural outcomes. The device was successfully implanted in all 8 patients randomized to Axxess, although the Axxess position was judged by the core lab to be too proximal in 1 patient. In the Axxess group, 1 Absorb BVS could not be delivered to the SB, although after kissing inflations, the result was deemed satisfactory by angiography (<50% stenosis). Due to proximal edge dissection, additional overlapping BVSs were implanted proximally in 1 patient in each group. All patients assigned to mod-T underwent successful implantation of Absorb BVSs. Procedures were completed with kissing inflation (mini-kissing in mod-T cases) in all 15 patients. Per protocol, the number of stents used per patient assigned to a strategy with Axxess was significantly higher compared with mod-T patients, but cumulative stent length per patient was similar in both groups. Procedure duration and fluoroscopy times were longer in the Axxess group, reflecting the higher complexity and increased number of steps involved in deployment of the Axxess device and additional BVSs.

QCA measurements immediately after PCI are presented in Supplemental Table S2. Overall, these results point toward a consistently numerically larger minimal lumen diameter in the proximal MV segment with Axxess, whereas similar minimal lumen diameters were achieved in both treatment arms in distal branches. 

Angiographic and OCT outcomes at 30 months. Angiographic follow-up at 30 months was available in 14 patients (93%) and is presented in Supplemental Table S2. In 1 patient, repeat angiography and OCT were not feasible. In 1 patient with poorly managed diabetes, only angiography was possible due to diffuse atheroma prohibiting OCT evaluation. There was no statistically significant difference in LLL between the treatment groups, although LLL in the proximal MV of the Axxess group was numerically smaller compared with the mod-T group (Supplemental Table S2).

Examples of OCT evaluation at baseline and 30-month follow-up are presented in Figures 2 and 3. Table 3 summarizes the quantitative OCT analysis in 13 patients (87%). In the Axxess group, significantly more stent struts were analyzed per patient in the proximal MV, due to the specific design of the stent having more struts per cross-section as compared with Absorb BVS. Only a small percentage of struts were uncovered, occurring more frequently in the proximal MV of the Axxess group than the mod-T group (2.2% vs 0.0%, respectively; P<.001). No evidence of neoatherosclerosis was observed.

Luminal dimensions at 30 months were consistently larger in the proximal MV in the Axxess group compared with the mod-T group (9.3 ± 2.9 mm2 vs 5.8 ± 1.3 mm2, respectively; P<.01) because of smaller neointimal area (1.8 ± 0.7 mm2 vs 3.2 ± 0.6 mm2, respectively; P<.001) and larger device area (11.2 ± 2.9 mm2 vs 8.9 ± 1.6 mm2, respectively; P=.03). Lumen dimensions were not significantly different in the distal MV and SB. 

The primary endpoint analysis of change in MLA on OCT from baseline to 30 months per predefined bifurcation segments is presented in Figure 4 and Supplemental Table S3). The MLAs at 30 months were significantly smaller than post procedure in the proximal MV, ostial distal MV, and ostial SB in the mod-T group, with mean differences of -3.1 ± 1.3mm2 (P<.001), -2.1 ± 1.0 mm2 (P<.01), and -2.1 ± 1.4 mm2 (P=.03), respectively. Similar results were noted in the Axxess group in the ostial distal MV (-2.1 ± 0.8 mm2; P<.001) and ostial SB (-1.6 ± 0.7 mm2; P<.01) while in the proximal MV the mean difference was only -0.1 ± 0.0 (P=.93), mainly due to less neointimal formation in the Axxess compared with the BVS (1.8 ± 0.7 mm2 vs 3.2 ± 0.6 mm2, respectively; P<.001) and larger device area (11.2 ± 2.9 mm2 vs 8.9 ± 1.6 mm2, respectively; P=.03). At the bifurcation core, the MLAs were larger at 30 months compared with baseline, numerically more so in the mod-T group than the Axxess group (3.1 ± 0.5 mm2 vs 0.5 ± 0.5 mm2, respectively; P=.07), likely due to resorption of the polymeric neocarina in the mod-T group. 

Mean differences in MLA from baseline to 30 months for the other bifurcation segments are presented in Table 4. Again, results between the groups were similar, except for the proximal MV segment, where the mean difference in MLA in the Axxess group was significantly smaller compared with the mod-T group (-0.1 ± 2.3 mm2 vs -3.1 ± 1.2 mm2, respectively; P=.02). 

Examples, incidence, and fate of acute strut discontinuities and frequency of late strut discontinuities are presented in Figure 5. At baseline, BVS strut discontinuities were found in 12 separate lesions in 8 out of the 15 patients (53%). These included extended crushed BVS-SB segments (n = 3), extensive double neocarina layer (n = 3), malapposition at overlap of Axxess and BVS (n = 2), and acute BVS structural rupture (n = 2). At 30 months, BVS strut discontinuities were found in 12 separate lesions in 8 out of the 15 patients (53%), 4 (33%) of which were covered and opposed. In 8 lesions (67%), discontinued struts were either uncovered and/or malapposed (ISD). In 1 lesion with uncovered and malapposed struts at 30 months, the struts had been fully apposed post procedure. In all 4 lesions with acute structural rupture, there was some form of ISD present at 30 months. 

Clinical outcomes. We did not observe differences in clinical outcome at 30 days, 1 year, or 3 years, and the overall event rate was low in this small cohort of patients (Table 5). Only 1 MACE occurred; at 30 months after Axxess procedure, during planned angiography and OCT evaluation, an asymptomatic patient underwent TLR due to a severe stenosis in the bifurcation segment involving the ostial distal MV (Supplemental Figure S1) (MLA, 0.7 mm2), which was hemodynamically significant (fractional flow reserve, 0.71). Three patients underwent non-TVR. There were no cases of cardiac death, spontaneous MI, or stent/scaffold thrombosis. Of note, all but 1 patient adhered to DAPT therapy until the 30-month control angiography. At 3-year follow-up, only 4 patients (27%) were still taking DAPT (Table 5). 

Discussion

The COBRA II study is the only randomized controlled clinical study to date that has evaluated the potential role of BVS in the treatment of complex coronary bifurcations. Due to the withdrawal of the Absorb BVS from the market in 2017, the planned number of patients could not be attained. Nevertheless, for the 15 patients with complex bifurcation lesions randomized within the study, 100% clinical follow-up to 3 years was accomplished with angiographic follow-up at 30 months in 14/15 patients (93%) and OCT evaluation at baseline and 30 months in 13/15 patients (87%). 

The main findings of this study are: 

(1) It is feasible to perform complex bifurcation stenting with BVS alone or in combination with a dedicated bifurcation device with excellent angiographic result. 

(2) At 30 months, MLAs were significantly smaller than post procedure in the majority of bifurcation segments treated with BVS due to neointima formation, while MLAs in the proximal Axxess segment remained stable mainly due to less neointima formation and to a lesser degree due to larger device area. 

(3) BVS-treated vessels did not show favorable vessel responses, such as positive vessel remodeling and late luminal enlargement. 

(4) Acute BVS strut discontinuities were observed in 53% of patients following bifurcation stenting, and late ISD was present in 38% of patients.

To date, evaluation of the Absorb BVS in bifurcation stenting has been limited to ex vivo bench testing, in vitro animal studies, and observational registries.7,14,15 The patients in this study had long lesions in large-caliber coronary bifurcations, representing truly complex bifurcation lesions. All patients were successfully treated with the assigned technique. Procedure duration was longer in the Axxess group, reflecting time spent in careful positioning of the Axxess system at the level of the bifurcation carina before positioning the BVS in the branches and performing the additional V-stenting. 

Procedures were clinically uneventful, and all patients obtained a satisfactory angiographic result. Nevertheless, in 1 case, the Axxess was positioned too proximal and in another case, a BVS could not be delivered beyond the Axxess into the SB due to a high take-off angle of the SB. The mod-T technique is a single-step mini-crush that involves just 1 wire recrossing and a mini-kissing post dilation. The crucial step is the correct positioning of the SB-BVS, aiming to position the proximal marker of the SB-BVS at the lower shoulder of the carina, thereby limiting the extent of scaffold crush (approximately 1 mm). 

Of note, MLD in the proximal MV segment was significantly larger immediately after treatment with the Axxess compared with the mod-T strategy. This difference can most likely be attributed to a more correct stent sizing with Axxess, according to the true RVD of the proximal segment, as opposed to a more conservative sizing according to the distal branches when performing a mod-T procedure. Despite proximal optimization and mini-kissing balloon inflation, these maneuvers with the mod-T approach do not allow the undersized scaffold cage to fully conform to the true proximal RVD. 

The primary endpoint of change in MLA was used because it was anticipated that the MLA at 30 months would be larger due to resorption of scaffold material. Unfortunately, with the exception of the bifurcation core, the opposite was observed, as scaffolds were still undergoing resorption in a process that appears to stimulate abundant neointimal formation. The promise of favorable vessel responses, such as positive vessel remodeling and late luminal enlargement, are thus unfulfilled.

Interestingly, despite similar strut thickness, neointimal formation was significantly greater in the proximal bifurcation segments in patients treated with BVS only compared with Axxess. 

Very late scaffold thrombosis beyond 1 year is a major safety issue with the polymeric BVS, although the exact causative mechanisms remain unclear. Several OCT studies have suggested a high prevalence of ISD at the time of very late BVS thrombosis.17 In a recent multimodality serial-imaging study by Onuma et al18 that comprised 400 patients randomized to either BVS or metallic DES, structural discontinuities (covered and/or uncovered) were noted in all cases at the time of BVS thrombosis. In their study, ISD was observed in 14% of cases at 3 years. Interestingly, the serial OCT analyses demonstrated that these intraluminal dismantlings developed at 2 years even if struts were fully apposed post procedure, with new dismantling developing between 2 and 3 years. The authors therefore suggest that optimizing strut apposition at the time of implantation does not eliminate the risk of late ISD. In the present study, due to the nature of bifurcation stenting, acute strut discontinuities were present in more than 50% of cases, with multiple discontinuities in different bifurcation segments present in 2 cases. The majority of discontinuities persisted up until 30 months in the form of covered and apposed discontinuities (4/12 lesions) or ISD (8/12 lesions) (Figure 5). There was 1 new case of ILSD in a bifurcation segment (ostial distal MV) where the struts were fully opposed post procedure with no obvious strut rupture on postprocedural OCT. Our group has previously shown in an in vivo animal bifurcation model that BVS strut fractures, clearly identified on micro-computed tomography, are frequently not apparent on OCT, as the affected struts tend to fall outward and thus do not protrude into the lumen.7 

If the SB-BVS is deployed too proximally, then an extensive triple layer of scaffold struts will be located just proximal to the origin of the SB. This occurred in 3/7 mod-T cases, although at 30 months there was complete endothelial coverage (Supplemental Figure S2); this theoretically increases the risk of early and late scaffold failure. If one or both of the BVSs in the Axxess group are placed too proximal (2 cases), or if there is proximal cell recrossing instead of distal in the mod-T group (1 case), then an extensive double layer of “thick-strutted” neocarina can result. In 2 of these cases, it resulted in persistent malapposed (covered) strut discontinuities at 30 months, while in 1 case complete endothelial covering was observed at 30 months (Figure 5). The presence on OCT of an acute strut rupture was noted in 4 patients (2 in each group) and resulted in asymptomatic late luminal dismantling in all 4 cases (Figure 5). 

Although the BVS platform investigated in this study is no longer available for clinical use, several bioresorbable scaffolds are in development or under investigation. Therefore, the present study provides important data (and caution) to guide the potential application of BRS technology to the percutaneous management of complex bifurcation lesions.

Study limitations. The main limitation of this study is the small number of patients included, with enrollment halted prematurely. Because of the exploratory nature of the study, no formal sample size calculations were performed and consequently no conclusions can be drawn on the clinical impact of the different bifurcation strategies with Absorb BVS. In addition, postprocedure OCT was performed for documentary purposes and not for guiding stent/scaffold sizing or optimization. Lastly, OCT and QCA analyses were not performed in independent core labs and blinding was not possible due to apparent differences between metallic DES and BVS devices.

Conclusion

In this randomized, controlled trial with serial intracoronary imaging, luminal dimensions were smaller in the segments treated with BVS alone compared with the Axxess bifurcation device, driven mainly by greater neointimal formation in the BVS. Although no cases of scaffold thrombosis occurred, acute strut discontinuities and late ISD, suspected to be one of the mechanisms of very late BVS thrombosis, were frequently observed. These observations suggest that future iterations of this bioresorbable technology should have thinner struts, eliminate late dismantling and, due to compromise of structural integrity, should probably be avoided in complex coronary interventions such as bifurcations. 

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8. Bennett J, Adriaenssens T, Desmet W, Dubois, C. Complex bifurcation lesions: randomized comparison of a fully bioresorbable modified t stenting strategy versus bifurcation reconstruction with a dedicated self-expanding stent in combination with bioresorbable scaffolds, an OCT study: rationale and design of the COBRA II trial. Catheter Cardiovasc Interv. 2016;88:843-853.

9. Van Mieghem N, Wilschut JJ, Ligthart J, Witberg K, van Geuns RJ, Regar E. Modified T-technique with bioresorbable scaffolds ensures complete carina coverage: an optical coherence tomography study. JACC Cardiovasc Interv. 2014;7:e109-e110. 

10. Dubois C, Adriaenssens T, Ughi G, et al. Healing responses after bifurcation stenting with the dedicated TRYTON side-branch stent in combination with XIENCE-V stents: a clinical, angiography, fractional flow reserve, and optical coherence tomography study: the PYTON study. Catheter Cardiovasc Interv. 2013;81:E155-E164.

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13. Onuma Y, Serruys PW, Muramatsu T, et al. Incidence and imaging outcomes of acute scaffold disruption and late structural discontinuity after implantation of the absorb everolimus-eluting fully bioresorbable vascular scaffold: optical coherence tomography assessment in the ABSORB cohort B trial. JACC Cardiovasc Interv. 2014;7:1400-1411.

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16. Verheye S, Agostoni P, Dubois CL, et al. 9-month clinical, angiographic, and intravascular ultrasound results of a prospective evaluation of the Axxess self-expanding biolimus A9-eluting stent in coronary bifurcation lesions: the DIVERGE study. J Am Coll Cardiol. 2009;53:1031-1039.

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From the 1Department of Cardiovascular Medicine, University Hospitals Leuven, Leuven, Belgium; and 2Department of Cardiovascular Sciences, Katholieke Universiteit Leuven, Leuven, Belgium.

Funding: This study is an investigator-initiated trial, supported with a research grant from Abbott Vascular. The Axxess devices were supplied by Biosensors International. 

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Bennett reports grant support from Abbott Vascular and Biotronik AG; consultancy fees from Boston Scientific, Abbott Vascular, Biotronik AG, and Terumo. Dr Dubois reports grant support from Abbott Vascular and Boston Scientific. The remaining authors report no conflicts of interest regarding the content herein.

The authors report that patient consent was provided for publication of the images used herein.

Manuscript accepted June 22, 2020.

Address for correspondence: Prof Dr J. Bennett, Department of Cardiovascular Medicine, University Hospitals Leuven, Herestraat 49, B 3000 Leuven, Belgium. Email: johan.bennett@uzleuven.be

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