Safety and efficiency of percutaneous coronary intervention using a standardised optical coherence tomography workflow.

BACKGROUND: While intravascular imaging guidance during percutaneous coronary intervention (PCI) improves outcomes, routine intravascular imaging usage remains low, in part due to perceived inefficiency and safety concerns.  Aims: The LightLab (LL) Initiative was designed to evaluate whether implementing a standardised optical coherence tomography (OCT) workflow impacts PCI safety metrics and procedural efficiency. METHODS: In this multicentre, prospective, observational study, PCI procedural data were collected over 2 years from 45 physicians at 17 US centres. OCT-guided PCI incorporating the LL workflow (N=264), a structured algorithm using routine pre- and post-PCI OCT imaging, was compared with baseline angiography-only PCI (angio) (N=428). Propensity score analysis identified 207 matched procedures. Outcomes included procedure time, radiation exposure, contrast volume, device utilisation, and treatment strategy. RESULTS: Compared with angiography alone, LL workflow OCT-guided PCI increased the median procedural time by 9 minutes but reduced vessel preparation time (2 min LL workflow vs 3 min angio; p<0.001) and resulted in less unplanned additional treatment (4% LL workflow vs 10% angio; p=0.01). With LL workflow OCT guidance, fewer cineangiography views were needed compared to angiography guidance, leading to decreased radiation exposure (1,133 mGy LL workflow vs 1,269 mGy angio; p=0.02), with no difference in contrast utilisation between groups (p=0.28). Furthermore, LL workflow OCT guidance resulted in fewer predilatation balloons and stents being used, more direct stent placement, and greater stent post-dilatation than angiography-guided PCI. CONCLUSIONS: The incorporation of a standardised pre- and post-PCI OCT imaging workflow improves procedural efficiency and safety metrics, at a cost of a modestly longer procedure time.

Mechanical stress-induced hemolysis of bovine blood is donor-dependent.

INTRODUCTION: In vitro hemolysis testing is an essential method for assessing the hemolytic potential of blood pumps, but has poor reproducibility. Further investigations are needed to determine the sources and extent of variability and to find a practical way to reduce the variation. METHODS: A small volume blood circulating loop driven by a Centrimag pump was established to provide relatively higher hemolysis readouts within a short run time and to be able to sequentially perform multiple repeated hemolysis tests in a working day. RESULTS: The repeatability with this system was demonstrated as the %RSD at 4.3% for the NIH or MIH from three repeated tests using the same blood. The bovine blood from different randomly selected donors was tested and gave more than a two-fold difference in NIH results (0.077 vs. 0.032 g/100 L) under the same testing conditions and same pump. This wide variation in hemolysis using bovine blood from different donors happened repeatedly. More importantly, it was observed that the difference in hemolysis test results using the blood drawn from the same donor on multiple days was narrow although the native hematocrits varied. The %RSD of NIH values obtained on five different days were 6.8%, 8.4%, 11.5%, and 7.8% for donor-specific blood from donors 1 to 4, respectively. CONCLUSION: The study results indicate that the mechanical stress-induced hemolysis behavior is donor-dependent. It has been also demonstrated that the reproducibility of in vitro hemolysis testing can be improved when the blood drawn from same donor is used.

Comparison of Angiographic and Intravascular Ultrasound Vessel Measurements in Infra-Popliteal Endovascular Interventions: The Below-the-Knee Calibration Study.

BACKGROUND: Endovascular revascularization (ER) via percutaneous transluminal angioplasty (PTA) and stenting are viable options for revascularization in below-the-knee (BTK) peripheral arterial disease. Two-dimensional angiography has been the standard of practice for estimating vessel size and selecting treatment devices during ER. However, in other vascular territories, intravascular ultrasound (IVUS) offers better visualization of the lumen dimensions. PURPOSE: To compare angiographic and intravascular ultrasound reference vessel (lumen) measurements in below-the-knee peripheral artery interventions. METHODS: Twenty consecutive patients were enrolled in the BTK Calibration study from 2 sites in the United States and Australia. Patients with at least one diseased segment in a native infra-popliteal artery (below-the-knee) and a clinical indication for endovascular therapy (EVT) were included with no limitations with regard to vessel diameter or lesion length. Digital subtraction angiography and IVUS imaging were collected pre- and post-PTA and images were sent to an independent core lab for standardized quantitative analysis of the normal-looking reference vessel dimensions when available. The results were presented as least square means with 95% confidence intervals and a p-value of <0.05 was considered significant. RESULTS: The overall (N = 19) mean reference vessel diameter for QVA was 2.98 ± 1.24 mm vs. 3.47 ± 0.72 mm for IVUS (mean difference was -0.50 mm, (95% CI: -0.80, -0.20; p = 0.14). As expected, in the proximal segments (N = 12), the mean reference vessel diameters were larger: for QVA, it was 3.17 ± 1.34 mm vs. 3.55 ± 0.76 mm in IVUS, (mean difference was -0.38 mm, (95% CI: -0.79, 0.03; p = 0.40); while in the distal segments (N = 7), mean reference vessel diameters were smaller: for QVA, it was 2.64 ± 1.06 mm vs. 3.33 ± 0.67 mm in IVUS, (mean difference was -0.69 mm, (95% CI: -1.04, 0.34; p = 0.17). We observed a greater degree of acute gain in cases where the treatment balloon size correlated with the IVUS measured reference size. CONCLUSION: Angiography underestimates infrapopliteal reference vessel lumen size even when quantitatively assessed. Adjunctive IVUS imaging use in guiding BTK procedures could help ensure adequate sizing and possibly impact immediate post-procedure indices.

Improving efficiency and operator proficiency during percutaneous coronary interventions utilizing a standardized optical coherence tomography workflow.

OBJECTIVES: This study was designed to compare efficiency and quality metrics between percutaneous coronary intervention (PCI) procedures using optical coherence tomography (OCT) guided by a variable workflow versus a standardized workflow in a real-world population. BACKGROUND: The LightLab (LL) Initiative was designed to evaluate the impact of a standardized OCT workflow during PCI to address barriers to adoption. METHODS: The LL Initiative was a multicenter, prospective, observational study. PCI efficiency data were collected from 1/21/19 to 1/8/21 from 45 physicians at 17 US centers. OCT-guided PCIs were compared between baseline phase (variable workflow; N = 383) and the LL workflow utilization phase (N = 447). The LL workflow uses OCT to assess lesion Morphology, Length and Diameter, and then optimize outcomes by correcting for Medial dissection, stent mal-Apposition, and under-eXpansion (MLD MAX). Matching based on propensity scores was used to control for differences between PCIs. RESULTS: After propensity matching, 291 paired procedures were included. Integration of the LL versus variable workflow resulted in no difference in procedure time (51 min vs. 51 min, p = 0.93). There was a reduction in radiation exposure (1124 mGy vs. 1493 mGy, p < 0.0001) and contrast volume (160 cc vs. 172 cc, p < 0.001). The LL workflow decreased the proportion of underexpanded lesions (34% vs. 54%, p < 0.0001) and improved minimum stent expansion (85% vs. 79%, p < 0.0001). Number of noncompliant balloons used was reduced with the LL workflow. (2.0 vs. 1.7, p < 0.01). CONCLUSIONS: These data suggest that standardizing imaging with the LL workflow may overcome barriers to imaging and improve PCI outcomes without prolonging procedures.

Design Effect of Metallic (Durable) and Polymeric (Resorbable) Stents on Blood Flow and Platelet Activation.

Bioresorbable vascular scaffolds (BVS) provide transient vessel support for occluded coronary arteries while resorbing over time, potentially allowing vessel restoration approximating the native, healthy state. Clinical trials indicate that the Absorb BVS (Abbott Vascular, Santa Clara, CA) performance was similar to that of the Xience metallic drug-eluting stent (DES), with low long-term complications rates. However, when under-deployed in very small vessels (diameter < 2.25 mm), the thrombosis rate of BVS was higher, possibly due to the effect of strut thickness on the hemodynamics (157 µm BVS vs. 81 µm DES). This study aims to determine the influence of BVS design in vessels of varying diameter on the potential platelet activation. Sixteen computational fluid dynamics models of vessels of varying diameter (1.8-3.0 mm), strut thickness (81-157 µm), and BVS/DES designs were compared. Platelet stress accumulation (SA), a metric for the activation potential, was calculated along platelet flow trajectories and their probability distribution was compared. The models were consistent with clinical observations, indicating that devices deployed in very small vessels exhibited increased probability for platelet activity as compared to the same devices deployed in nominal sized vessels. Deployment, although with residual stenosis, increased probability for higher SA than in similar diameter straight vessels. Reducing BVS struts thickness while maintaining their pattern improved performance closer to that of DES. Our findings highlight the importance of appropriate vessel sizing and deployment technique for BVS, and may help designing future BVS with thinner struts, ultimately improving performance in very small vessels.

Evaluation of chemical stability of polymers of XIENCE everolimus-eluting coronary stents in vivo by pyrolysis-gas chromatography/mass spectrometry.

The polymers poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and poly(n-butyl methacrylate) (PBMA) are employed in manufacturing the XIENCE family of coronary stents. PBMA serves as a primer and adheres to both the stent and the drug coating. PVDF-HFP is employed in the drug matrix layer to hold the drug everolimus on the stent and control its release. Chemical stability of the polymers of XIENCE stents in the in-vivo environment was evaluated by pyrolysis-gas chromatography with mass spectrometry (Py-GC/MS) detection. For this evaluation, XIENCE stents explanted from porcine coronary arteries and from human coronary artery specimens at autopsy after 2-4 and 5-7 years of implantation, respectively, were compared to freshly manufactured XIENCE stents (controls). The comparison of pyrograms of explanted stent samples and controls showed identical fragmentation fingerprints of polymers, indicating that PVDF-HFP and PBMA maintained their chemical integrity after multiple years of XIENCE coronary stent implantation. The findings of the present study demonstrate the chemical stability of PVDF-HFP and PBMA polymers of the XIENCE family of coronary stents in the in-vivo environment, and constitute a further proof of the suitability of PVDF-HFP as a drug carrier for the drug eluting stent applications. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1721-1729, 2018.

Lessons Learned Regarding Handling and Deployment of the Absorb Bioresorbable Vascular Scaffold in Infrapopliteal Arteries.

PURPOSE: To describe relevant technical details with which to facilitate safe and effective use of the Absorb coronary bioresorbable vascular scaffold (BVS) in lower extremity arteries. TECHNIQUE: The Absorb BVS is a balloon-expandable, poly-l-lactide structure covered in a poly-d,l-lactide bioresorbable polymer that contains the antiproliferative drug everolimus. As a polymeric structure, it has a number of unique physical, handling, and imaging properties that may differ from metallic stents and pose a challenge to the interventionist. Attention must be paid to lesion selection, preparation, scaffold sizing, deployment, and postdilation to achieve optimal outcomes. A detailed description of these issues and deployment techniques is offered based on experience using this BVS in below-the-knee arteries. CONCLUSION: The Absorb BVS may have application in the infrapopliteal circulation; however, its unique properties warrant careful consideration before use in the lower limb.

Paving the way to a bioresorbable technology: Development of the absorb BRS program.

Bioresorbable scaffolds (BRS) combine attributes of the preceding generations of percutaneous coronary intervention (PCI) devices with new technologies to result in a novel therapy promoted as being the fourth generation of PCI. By providing mechanical support and drug elution to suppress restenosis, BRS initially function similarly to drug eluting stents. Thereafter, through their degradation, BRS undergo a decline in radial strength, allowing a gradual transition of mechanical function from the scaffold back to the artery in order to provide long term effectiveness similar to balloon angioplasty. The principles of operation of BRS, whether of polymeric or metallic composition, follow three phases of functionality reflective of differing physiological requirements over time: revascularization, restoration, and resorption. In this review, these three fundamental performance phases and the metrics for the nonclinical evaluation of BRS, including both bench and preclinical testing, are discussed. © 2016 Wiley Periodicals, Inc.

The BVS concept. From the chemical structure to the vascular biology: the bases for a change in interventional cardiology.

Bioresorbable vascular scaffolds (BVS), the fourth generation of percutaneous coronary intervention (PCI), aim to improve the long-term outcomes of PCI facilitating the restoration of the physiology of the treated vessels when the scaffold dismantling process is completed. In this paper we will review all the technical aspects as well as the potential clinical indications of this technology.

Design Principles of Bioresorbable Polymeric Scaffolds.

The concept for a bioresorbable vascular scaffold combines the best features of the first 3 generations of percutaneous coronary intervention (namely), balloon angioplasty, bare metallic stents, and drug-eluting stents, into a single device. The principles of operation of a BRS follow 3 phases of functionality that reflect the different physiologic requirements over time; revascularization, restoration, and resorption. Most BRS designs make use of the continuum of hydrolytic degradation in aliphatic polyesters, such as poly(l-lactide), in which molecular weight, strength, and mass decrease progressively in 3 distinct stages, consistent with the in vivo requirements of each performance phase.

Relation Between Bioresorbable Scaffold Sizing Using QCA-Dmax and Clinical Outcomes at 1 Year in 1,232 Patients From 3 Study Cohorts (ABSORB Cohort B, ABSORB EXTEND, and ABSORB II).

OBJECTIVES: This study sought to investigate the clinical outcomes based on the assessment of quantitative coronary angiography-maximal lumen diameter (Dmax). BACKGROUND: Assessment of pre-procedural Dmax of proximal and distal sites has been used for Absorb scaffold size selection in the ABSORB studies. METHODS: A total of 1,248 patients received Absorb scaffolds in the ABSORB Cohort B (ABSORB Clinical Investigation, Cohort B) study (N = 101), ABSORB EXTEND (ABSORB EXTEND Clinical Investigation) study (N = 812), and ABSORB II (ABSORB II Randomized Controlled Trial) trial (N = 335). The incidence of major adverse cardiac events (MACE) (a composite of cardiac death, any myocardial infarction [MI], and ischemia-driven target lesion revascularization) was analyzed according to the Dmax subclassification of scaffold oversize group versus scaffold nonoversize group. RESULTS: Of 1,248 patients, pre-procedural Dmax was assessed in 1,232 patients (98.7%). In 649 (52.7%) patients, both proximal and distal Dmax values were smaller than the nominal size of the implanted scaffold (scaffold oversize group), whereas in 583 (47.3%) of patients, the proximal and/or distal Dmax were larger than the implanted scaffold (scaffold nonoversize group). The rates of MACE and MI at 1 year were significantly higher in the scaffold oversize group than in the scaffold nonoversize group (MACE 6.6% vs. 3.3%; log-rank p < 0.01, all MI: 4.6% vs. 2.4%; log-rank p = 0.04), mainly driven by a higher MI rate within 1 month post-procedure (3.5% vs. 1.9%; p = 0.08). The independent MACE determinants were both Dmax smaller than the scaffold nominal size (odds ratio [OR]: 2.13, 95% confidence interval [CI]: 1.22 to 3.70; p < 0.01) and the implantation of overlapping scaffolds (OR: 2.10, 95% CI: 1.17 to 3.80; p = 0.01). CONCLUSIONS: Implantation of an oversized Absorb scaffold in a relatively small vessel appears to be associated with a higher 1-year MACE rate driven by more frequent early MI. (ABSORB Clinical Investigation, Cohort B [ABSORB Cohort B], NCT00856856; ABSORB EXTEND Clinical Investigation [ABSORB EXTEND], NCT01023789; ABSORB II Randomized Controlled Trial [ABSORB II], NCT01425281).

Long-term safety of an everolimus-eluting bioresorbable vascular scaffold and the cobalt-chromium XIENCE V stent in a porcine coronary artery model.

BACKGROUND: The Absorb everolimus-eluting bioresorbable vascular scaffold (Absorb) has shown promising clinical results; however, only limited preclinical data have been published. We sought to investigate detailed pathological responses to the Absorb versus XIENCE V (XV) in a porcine coronary model with duration of implant extending from 1 to 42 months. METHODS AND RESULTS: A total of 335 devices (263 Absorb and 72 XV) were implanted in 2 or 3 main coronary arteries of 136 nonatherosclerotic swine and examined by light microscopy, scanning electron microscopy, pharmacokinetics, and gel permeation chromatography analyses at various time points. Vascular responses to Absorb and XV were largely comparable at all time points, with struts being sequestered within the neointima. Inflammation was mild to moderate (with absence of inflammation at 1 month) for both devices, although the scores were greater in Absorb at 6 to 36 months. Percent area stenosis was significantly greater in Absorb than XV at all time points except at 3 months. The extent of fibrin deposition was similar between Absorb and XV, which peaked at 1 month and decreased rapidly thereafter. Histomorphometry showed expansile remodeling of Absorb-implanted arteries starting after 12 months, and lumen area was significantly greater in Absorb than XV at 36 and 42 months. These changes correlated with dismantling of Absorb seen after 12 months. Gel permeation chromatography analysis confirmed that degradation of Absorb was complete by 36 months. CONCLUSIONS: Absorb demonstrates comparable long-term safety to XV in porcine coronary arteries with mild to moderate inflammation. Although Absorb was associated with greater percent stenosis relative to XV, expansile remodeling was observed after 12 months in Absorb with significantly greater lumen area at ≥ 36 months. Resorption is considered complete at 36 months.

Lumen gain and restoration of pulsatility after implantation of a bioresorbable vascular scaffold in porcine coronary arteries.

OBJECTIVES: Using intravascular ultrasound (IVUS) and histomorphometry, this study sought to evaluate the potential of nonatherosclerotic porcine coronary arteries to undergo progressive lumen gain and a return of pulsatility after implantation with an everolimus-eluting bioresorbable vascular scaffold (BVS). BACKGROUND: Unique benefits such as lumen gain and restored vasomotion have been demonstrated clinically after treatment with BVS; however, a more rigorous demonstration of these benefits with a randomized clinical trial has not yet been conducted. METHODS: Seventy nonatherosclerotic swine received 109 everolimus-eluting BVS and 70 everolimus-eluting metal stents randomized among the main coronary arteries. Arteries were evaluated in vivo by angiography and IVUS and post-mortem by histomorphometry at time points from 1 to 42 months. RESULTS: From 1 to 6 months, both BVS- and everolimus-eluting metal stent-implanted arteries demonstrated stable lumen areas (LAs). From 12 months to 42 months, there was a progressive increase in the LA of arteries implanted with a BVS as assessed by histomorphometry and IVUS. This lumen gain in the implanted segment corresponded to an increase in the reference vessel LA. Normalization in the in-segment LA (LA:reference vessel LA) was observed qualitatively by angiography and quantitatively by IVUS. Additionally, BVS-implanted arteries demonstrated restored in-segment pulsatility on the basis of IVUS assessment of the differences in the mid-scaffold area between end-diastole to end-systole. CONCLUSIONS: Starting at 12 months, BVS-implanted porcine coronary arteries underwent progressive lumen gain and showed restored pulsatility. These benefits demonstrated preclinically may translate into improvements in long-term clinical outcomes for patients treated with BVS compared with conventional drug-eluting stents.

Intracoronary optical coherence tomography and histology of overlapping everolimus-eluting bioresorbable vascular scaffolds in a porcine coronary artery model: the potential implications for clinical practice.

OBJECTIVES: This study sought to assess the vascular response of overlapping Absorb stents compared with overlapping newer-generation everolimus-eluting metallic platform stents (Xience V [XV]) in a porcine coronary artery model. BACKGROUND: The everolimus-eluting bioresorbable vascular scaffold (Absorb) is a novel approach to treating coronary lesions. A persistent inflammatory response, fibrin deposition, and delayed endothelialization have been reported with overlapping first-generation drug-eluting stents. METHODS: Forty-one overlapping Absorb and overlapping Xience V (XV) devices (3.0 × 12 mm) were implanted in the main coronary arteries of 17 nonatherosclerotic pigs with 10% overstretch. Implanted coronary arteries were evaluated by optical coherence tomography (OCT) at 28 days (Absorb n = 11, XV n = 7) and 90 days (Absorb n = 11, XV n = 8), with immediate histological evaluation following euthanasia at the same time points. One animal from each time point was evaluated with scanning electron microscopy alone. A total of 1,407 cross sections were analyzed by OCT and 148 cross sections analyzed histologically. RESULTS: At 28 days in the overlap, OCT analyses indicated 80.1% of Absorb struts and 99.4% of XV struts to be covered (p < 0.0001), corresponding to histological observations of struts with cellular coverage of 75.4% and 99.6%, respectively (p < 0.001). Uncovered struts were almost exclusively related to the presence of "stacked" Absorb struts, that is, with a direct overlay configuration. At 90 days, overlapping Absorb and overlapping XV struts demonstrated >99% strut coverage by OCT and histology, with no evidence of a significant inflammatory process, and comparable % volume obstructions. CONCLUSIONS: In porcine coronary arteries implanted with overlapping Absorb or overlapping XV struts, strut coverage is delayed at 28 days in overlapping Absorb, dependent on the overlay configuration of the thicker Absorb struts. At 90 days, both overlapping Absorb and overlapping XV have comparable strut coverage. The implications of increased strut thickness may have important clinical and design considerations for bioresorbable platforms.

Endoprótesis coronarias bioabsorbibles / The coronary bioresorbable vascular scaffold

El desarrollo de las técnicas de intervencionismo coronario percutáneo se puede resumir en cuatro oleadas o revoluciones: la propia aparición de la técnica de angioplastia coronaria con balón, el desarrollo de las endoprótesis coronarias (stents) para solucionar las limitaciones de la angioplastia con balón, la adición de fármacos antiproliferativos en los stents farmacoactivos para evitar la reestenosis y, finalmente, la aparición de las endoprótesis vasculares bioabsorbibles. Este artículo comienza con una breve descripción de los dispositivos utilizados en el intervencionismo a lo largo de tres décadas que han conducido a la aparición final de las endoprótesis bioabsorbibles. Posteriormente, se revisan las principales características y dificultades en el desarrollo de estas endoprótesis. El núcleo de este artículo es una descripción de los productos en desarrollo y de los resultados preclínicos y clínicos disponibles actualmente. La conclusión refleja una visión del prometedor futuro del intervencionismo y las endoprótesis bioabsorbibles (AU)

The development of percutaneous coronary intervention techniques occurred in four waves or revolutions: (i) the introduction of coronary balloon angioplasty; (ii) the development of coronary stents to tackle the limitations of balloon angioplasty; (iii) the incorporation of antiproliferative drugs into drug-eluting stents to help prevent restenosis; and, finally, (iv) the advent of bioresorbable vascular scaffolds. This article starts with a brief description of the devices that have been used in coronary interventions during the last three decades and that ultimately led to the development of the bioresorbable vascular scaffold. Then, the main characteristics of these devices and the problems faced in developing them are summarized. The core of the article contains a description of devices currently under development, and discusses recent preclinical and clinical findings. The conclusion foresees a promising future for coronary interventions and bioresorbable vascular scaffolds (AU)

In vivo characterisation of bioresorbable vascular scaffold strut interfaces using optical coherence tomography with Gaussian line spread function analysis.

AIMS: Optical coherence tomography (OCT) of a bioresorbable vascular scaffold (BVS) produces a highly reflective signal outlining struts. This signal interferes with the measurement of strut thickness, as the boundaries cannot be accurately identified, and with the assessment of coverage, because the neointimal backscattering convolutes that of the polymer, frequently making them indistinguishable from one another. We hypothesise that Gaussian line spread functions (LSFs) can facilitate identification of strut boundaries, improving the accuracy of strut thickness measurements and coverage assessment. METHODS AND RESULTS: Forty-eight randomly selected BVS struts from 12 patients in the ABSORB Cohort B clinical study and four Yucatan minipigs were analysed at baseline and follow-up (six months in humans, 28 days in pigs). Signal intensities from the raw OCT backscattering were fit to Gaussian LSFs for each interface, from which peak intensity and full-width-at-half-maximum (FWHM) were calculated. Neointimal coverage resulted in significantly different LSFs and higher FWHM values relative to uncovered struts at baseline (p<0.0001). Abluminal polymer-tissue interfaces were also significantly different between baseline and follow-up (p=0.0004 in humans, p<0.0001 in pigs). Using the location of the half-max of the LSF as the polymer-tissue boundary, the average strut thickness was 158±11 µm at baseline and 152±20 µm at six months (p=0.886), not significantly different from nominal strut thickness. CONCLUSIONS: Fitting the raw OCT backscattering signal to a Gaussian LSF facilitates identification of the interfaces between BVS polymer and lumen or tissue. Such analysis enables more precise measurement of the strut thickness and an objective assessment of coverage.

Spatial distribution and temporal evolution of scattering centers by optical coherence tomography in the poly(L-lactide) backbone of a bioresorbable vascular scaffold.

BACKGROUND: Scattering centers (SC) are often observed with optical coherence tomography (OCT) in some struts of bioresorbable vascular scaffolds (BVS). These SC might be caused by crazes in the polymer during crimp-deployment (more frequent at inflection points) or by other processes, such as physiological loading or hydrolysis (eventually increasing with time). The spatial distribution and temporal evolution of SC in BVS might help to understand their meaning. METHODS AND RESULTS: Three patients were randomly selected from 12 imaged with Fourier-domain OCT at both baseline and 6 months in the ABSORB cohort B study (NCT00856856). Frame-by-frame analysis of the SC distribution was performed using spread-out vessel charts, and the results from baseline and 6 months were compared. A total of 4,328 struts were analyzed. At baseline and follow-up all SC appeared at inflection points. No significant difference was observed between baseline and 6 months in the number of SC struts (14.9 vs. 14.5%, P=0.754) or in the distribution of SC. The proportion and distribution of SC did not vary substantially among the patients analyzed. CONCLUSIONS: The SC observed in OCT imaging of the BVS are located exclusively at inflection points and do not increase with time. These findings strongly suggest that SC are caused by crazes in the polymer during crimp-deployment, ruling out any major role of hydrolysis or other time-dependent processes.