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Real-World Bioresorbable Vascular Scaffold Experience Compared With Second-Generation Metallic Drug-Eluting Stents in Complex Coronary Lesions
Abstract: Objectives. The aim of the study was to compare the acute outcomes of Absorb bioresorbable vascular scaffolds (BVS) and second-generation drug-eluting stent (DES) implantation in routine clinical practice. There is a paucity of data regarding BVS use in a real-world patient population. Methods. The study population comprised 40 consecutive patients who underwent percutaneous coronary intervention (PCI) with BVS implantation at a tertiary-care center in New York, New York between July and December of 2016. An optimal implantation technique including adequate lesion preparation, mandatory postdilation, and optical coherence tomography (OCT) imaging was used in all cases. De novo lesions treated with BVS were compared to lesions treated with DES matched by OCT calcium arc, scaffold/stent size, use of atherectomy device, and lesion postdilation. Acute lumen gain, minimal device area, malapposition, eccentricity, and symmetry index were assessed using OCT. Results. We analyzed OCT images of 40 BVS cases and 40 matching DES cases from 35 and 40 patients, respectively. Compared to the DES group, the BVS group demonstrated similar acute lumen gain, minimal scaffold/stent area, eccentricity index, and symmetry index after PCI. There were fewer malapposed struts detected after BVS implantation; however, malapposition distance and length were not different between the groups. Conclusion. BVS implantation in a real-world patient population with optimal implantation technique resulted in similar stent expansion and better strut apposition compared to DES implantation.
J INVASIVE CARDIOL 2018;30(7):251-255. Epub 2018 April 15.
Key words: bioresorbable vascular scaffold, drug-eluting stent, optical coherence tomography
Bioresorbable vascular scaffold (BVS) implantation was introduced more than a decade ago as a potential major breakthrough for the treatment of coronary artery lesions, providing a possibility to overcome numerous limitations of metallic drug-eluting stent (DES) implantation. Among numerous BVS devices under development, the Absorb BVS (Abbott Vascular), an everolimus-eluting polymeric scaffold with 157 µm strut thickness, has undergone the most extensive clinical evaluation in a series of randomized clinical trials. Despite the favorable preliminary results for this first-generation BVS, several serious concerns related to higher target-lesion failure and thrombotic risk were raised by subsequent reports on long-term follow-up,1-5 leading to discontinuing commercial sales of the device. Understanding the shortcomings of the first-generation BVS is crucial for the future development of improved next-generation devices.
Compared to randomized clinical trials with highly selected patient population, there are limited data regarding the use of BVS in routine clinical practice.6 Recently, the acute performance of BVS has been compared with second-generation DES implantation in real-world complex coronary lesions matched by the degree of angiographic calcification.7,8 Optical coherence tomography (OCT) has been shown to detect coronary calcification with higher sensitivity and specificity than angiography9 and allows the quantitative assessment of the degree of lesion calcium by measuring calcium arc and length.10 The aim of the study was to compare the acute outcomes of BVS and DES implantation in complex coronary lesions matched by the degree of OCT calcification.
Methods
Study population. The study population comprised consecutive patients who underwent percutaneous coronary intervention (PCI) with BVS implantation and OCT imaging for treatment of stable coronary artery disease (CAD) in our institution from July to December of 2016. For patients with de novo lesions, we selected patients who underwent second-generation DES implantation and OCT imaging between 2015 and 2016 matched for baseline characteristics, maximal calcium arc by OCT, scaffold/stent size, use of atherectomy device, and lesion postdilation. Clinical follow-up included telephone follow-up at 30 days and 1 year after PCI and a review of medical records and clinical visits by trained research coordinators.
Treatment procedure. For BVS implantation, lesions were treated with predilation using conventional semicompliant or non-compliant balloons. The use of additional devices, such as rotational and orbital atherectomy, was performed at the operator’s discretion. OCT pullbacks were performed before and after BVS implantation; postdilation was performed in all BVS cases.
Quantitative coronary angiography (QCA). QCA was performed using QCA-QAngioXA version 7.3 dedicated software (Medis) by experienced analysts (HU, YV, and NO) as previously described.11
OCT image acquisition and analysis. OCT pullbacks were acquired before and after BVS/DES implantation with the commercially available C7-XR OCT Intravascular Imaging System (Abbott Vascular). OCT images were analyzed offline using the Medical Offline Review Workstation (St. Jude) according to current guidelines.10 In DES cases, stent area, strut apposition, and incomplete strut apposition (ISA) distance were assessed on the basis of conventional definitions.10 In order to reduce the biases of comparison between BVS and DES, we used endoluminal scaffold contour to assess scaffold area and ISA distance in BVS cases (Figure 1).12 Eccentricity index (EI) was calculated as the ratio of the minimum scaffold/stent diameter and the maximum scaffold/stent diameter in each analyzed cross-section. Symmetry index (SI) was calculated as (maximum scaffold/stent diameter – minimum scaffold/stent diameter) ÷ maximum scaffold/stent diameter for each lesion.8 Acute lumen gain was defined as the difference between minimum lumen diameter (MLD) before and after intervention.
Statistical analysis. All continuous measurements were expressed as mean ± standard deviation and compared using Student’s t-test or Mann-Whitney U-test depending on distribution. Categorical variables are presented as frequencies (percentages) and were compared using the Chi-square test or Fisher’s exact test. Propensity-score matching was performed using multiple logistic regression analysis including the following variables as covariates: previous myocardial infarction, previous coronary artery bypass graft surgery, smoking, dyslipidemia, diabetes mellitus, use of atherectomy device, stent/BVS postdilation, stent/BVS diameter and length, and maximal calcium arc assessed by OCT. Statistical analysis was performed using SPSS 24.0 statistical software (IBM Corporation).
Results
Study population. Forty patients with 46 lesions underwent PCI with BVS implantation and OCT imaging. Of these, thirty-five patients presented with 40 de novo lesions that were used for the present analysis, while the remaining 6 lesions were treated for in-stent restenosis. All BVS de novo lesions were matched to 40 lesions treated with DES in 40 patients from our multimodality imaging database, which has been approved by our Institutional Review Board. Baseline demographic and clinical characteristics were similar between the groups (Table 1).
Angiographic and procedural characteristics. Angiographic and procedural parameters are summarized in Table 2. There were no significant differences in lesion complexity, atherectomy, and postdilation; however, predilation was more frequently performed in the BVS group. The predilation balloon size in the BVS group was significantly larger compared with balloon size in the DES group. Scaffold/stent sizes and the frequencies of postdilation were also similar in the BVS and DES groups, with higher final postdilation balloon pressure in the BVS group.
QCA findings. QCA findings before and after scaffold/stent implantation are summarized in Table 3. There were no differences in minimum lumen diameter and diameter stenosis before and after intervention; implantation of BVS led to acute lumen gain similar to the DES group.
OCT analysis. OCT findings before and after PCI are shown in Table 3. BVS-treated and DES-treated lesions were well matched by the prevalence of calcification and the maximum calcification arc. After PCI, minimum scaffold/stent area, EI, and SI were similar in both groups. Similar to QCA, acute lumen gain assessed by OCT was comparable between the groups. Furthermore, BVS and DES demonstrated a similar prevalence of stents with ISA, maximum ISA distance, and total ISA length; however, the percentage of malapposed struts was lower in the BVS group than in the DES group (1.80 ± 2.80% vs 4.19 ± 4.39%, respectively; P<.01).
Clinical outcomes for BVS patients. Follow-up data were available for 100% of BVS and DES patients at 30 days and 1 year. At 1 month, there was no death, myocardial infarction, target-lesion revascularization, target-vessel revascularization, or scaffold thrombosis (ST) reported in the BVS group. Two myocardial infarctions were reported at 1-year follow-up. No death or ST was reported at 1 year.
Discussion
In this study, we report our center’s experience treating CAD patients with Absorb BVS under optimal implantation techniques, including adequate lesion preparation, mandatory postdilation, and the routine use of OCT imaging. We further compared the acute performance of BVS with that of second-generation DES implanted into coronary lesions with a similar degree of calcification as assessed by OCT. The main findings of the study are: (1) acute lumen gain by QCA and OCT was comparable after BVS and DES implantation; (2) BVS and DES demonstrated similar scaffold/stent expansion characteristics, including minimum scaffold/stent area, residual stenosis, EI, and SI; and (3) ISA area and distance were comparable between the groups; however, there were fewer malapposed struts observed after BVS implantation.
One-year ABSORB II trial analysis showed non-inferiority of Absorb BVS compared to second-generation DES; however, the 3-year follow-up study reported a higher rate of ST with BVS.1 A significant increase in ST has been reported by several meta-analyses and randomized trials.3,5 Incomplete lesion coverage, scaffold under-expansion, and strut malapposition were the most frequently observed OCT findings in cases of ST.13 Small in-stent minimum lumen area and small minimum stent area were also predictors of adverse events after DES implantation in several OCT studies.14,15 In order to avoid the mechanical causes of ST and improve clinical outcomes, an optimal implantation technique including satisfactory lesion preparation, intravascular imaging guidance, and mandatory postdilation has been recommended for BVS cases.16 Our BVS group had a higher frequency of predilation with a larger balloon compared to the DES group; postdilation with higher pressure was performed in all BVS cases. As a result, scaffold expansion, acute lumen gain, and malapposition area and distance in the BVS group were similar to the DES group; furthermore, BVS cases had fewer struts identified as malapposed compared to DES cases. The results suggest that with adequate implantation technique, BVS cases can achieve optimal scaffold deployment with acute outcomes similar to DES cases in a real-world patient population. Despite the comparable metrics of BVS and DES deployment, the Absorb BVS has a thicker strut (157 µm) to improve its radial strength, resulting in struts occupying about 27% of the vessel wall vs only 13% for DES.17 Next-generation BVS devices with thinner struts might be able to mitigate the risk for ST while providing the benefits of complete restoration of vascular physiology.
Coronary artery calcification is an important marker of CAD and might present a challenge during PCI. BVS implantation in calcific lesions has been shown to be feasible and safe with meticulous lesion preparation in order to facilitate optimal stent expansion and apposition.18 Two recent studies used OCT imaging to compare the acute outcomes of BVS and DES implantation in calcified lesions and reported similar scaffold/stent expansion.7,8 The DES group in both studies was selected from current cases to match angiographic characteristics of the BVS group, including lesion length, vessel diameter, and degree of angiographic calcification. OCT identified calcium with high sensitivity (95%) and specificity (97%) in a histology validation study;19 it detected calcium in almost twice as many lesions as angiography (77% vs 40%, respectively) in 440 target lesions of stable patients undergoing PCI.9 In addition, OCT can assess calcification arc, length, thickness, area, and volume, since infrared light can penetrate calcific deposits. To the best of our knowledge, the present analysis is the first comparison of acute outcomes after BVS and DES implantation in complex coronary lesions with a similar degree of calcification assessed by OCT in addition to procedural characteristics and device dimensions. Similar to our findings, matching BVS and DES lesions by angiographic calcium resulted in similar scaffold/stent area, EI, and SI,7,8 and less frequent strut malapposition.20 In contrast to our analysis, BVS cases were associated with more eccentric expansion characterized by lower SI (0.85 vs 0.87; P<.01) in a report by Fam et al.20 The authors suggested that a larger balloon size used for postdilation of DES compared to BVS was responsible for the difference in SI. In our study, similar postdilation balloon size with higher pressure was used in the BVS group, which resulted in a comparable EI in BVS and DES cases. Another possible explanation could be better-matched comparison groups, since we used OCT, a more precise method than angiography to assess coronary calcium in our study to select matching DES cases.
Study limitations. The study is a single-center retrospective analysis of a small number of patients. Since the abluminal side of a malapposed DES strut is invisible in contrast to BVS, it might lead to an over-estimation of ISA frequency after DES implantation.
Conclusion
BVS implantation in a real-world patient population with optimal implantation technique resulted in similar stent expansion and better strut apposition compared to DES implantation.
References
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From the Division of Cardiology, Mount Sinai Hospital and Icahn School of Medicine at Mount Sinai, New York, New York.
Funding: The study was sponsored by Abbott Cardiovascular Systems, Inc.
Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.
Manuscript submitted February 27, 2018 and accepted March 5, 2018.
Address for correspondence: Annapoorna S. Kini, MD, Mount Sinai Hospital, One Gustave L. Levy Place, Box 1030, New York, NY 10029. Email: annapoorna.kini@mountsinai.org
