Local Variations in Carbohydrates and Matrix Lignin in Mechanically Graded Bamboo Culms

The mechanical performance of bamboo is highly dependent on its structural arrangement and the properties of biomacromolecules within the cell wall. The relationship between carbohydrates topochemistry and gradient micromechanics of multilayered fiber along the diametric direction was visualized by combined microscopic techniques. Along the radius of bamboo culms, the concentration of xylan within the fiber sheath increased, while that of cellulose and lignin decreased gradually. At cellular level, although the consecutive broad layer (Bl) of fiber revealed a relatively uniform cellulose orientation and concentration, the outer Bl with higher lignification level has higher elastic modulus (19.59–20.31 GPa) than that of the inner Bl close to the lumen area (17.07–19.99 GPa). Comparatively, the cell corner displayed the highest lignification level, while its hardness and modulus were lower than that of fiber Bl, indicating the cellulose skeleton is the prerequisite of cell wall mechanics. The obtained cytological information is helpful to understand the origin of the anisotropic mechanical properties of bamboo.

Diagnostic Performance of Frequency-Domain Optical Coherence Tomography to Predict Functionally Significant Left Main Coronary Artery Stenosis

Aims. The aim of this study was to assess the safety and diagnostic efficacy of frequency-domain optical coherence tomography (FD-OCT) in identifying functional severity of the left main coronary artery (LM) stenosis determined by fractional flow reserve (FFR). Methods and Results. 101 patients with LM lesion (20–70% diameter stenosis angiographically) underwent FFR measurement and FD-OCT imaging of the LM. The following parameters were measured by FD-OCT in the LM: reference lumen area (RLA), reference lumen diameter (RLD), minimum lumen area (MLA), minimum lumen diameter (MLD), % lumen area stenosis, and % diameter stenosis. The LM lesions were analyzable by FD-OCT in 88/101 (87.1%) patients. FFR at maximum hyperemia was ≤0.80 in 39/88 (44.3%) patients. FFR values were correlated significantly with FD-OCT-derived LM lumen parameters. An MLA cutoff value of 5.38 mm2 had the highest sensitivity and specificity of 82% and 81%, respectively, followed by an MLD of 2.43 mm (sensitivity 77%, specificity 72%) and AS of 60% (sensitivity 72%, specificity 72%) for predicting FFR <0.80. Conclusions. FD-OCT is a safe and feasible imaging technique for the assessment of LM stenosis. An FD-OCT-derived MLA of ≤5.38 mm2 strongly predicts the functional severity of an LM lesion.

Impact of Baseline and Postprocedural Intravascular Ultrasound Findings on 1-Year Primary Patency After Drug-Coated Balloon Treatment of Femoropopliteal Lesions

Purpose: Drug-coated balloons (DCBs) are commonly used for endovascular treatment of femoropopliteal lesions. Here, we employed intravascular ultrasound (IVUS) to investigate the predictors of restenosis after DCB treatment. Methods: This retrospective and single-center study was performed to examine 1-year primary patency after DCB treatment and to identify the risk factors for restenosis by analyzing clinical characteristics, angiographic findings, and IVUS measurements. We included 111 consecutive patients undergoing DCB treatment for de novo femoropopliteal lesions at our hospital from July 2018 to March 2020. Results: The primary patency rate was found to be 80.0% at 1 year. The Cox proportional hazard multivariate analysis revealed that restenosis was independently associated with chronic total occlusion (CTO; p < 0.001), circumferential calcification (p = 0.023), and smaller postprocedural minimum lumen area (MLA; p = 0.036). Furthermore, receiver operating characteristic curve analysis showed that the cutoff value of postprocedural MLA to prevent restenosis was 12.7 mm2, with an area under the curve of 0.774 (p< 0.001). The multivariate analysis indicated that patients with a postprocedural MLA below 12.7 mm2 (n = 44) had a significantly smaller distal reference vessel size (p < 0.001) compared to those with a postprocedural MLA over 12.7 mm2 (n = 67). Conclusions: Restenosis after DCB treatment was shown to correlate with CTO, circumferential calcification, and postprocedural MLA as evaluated by IVUS. Moreover, smaller vessel sizes might represent a particular challenge to the DCB strategy due to the difficulty of restoring a sufficient postprocedural lumen area by balloon dilatation.

Comparison of Angiographic Dissection Classification Systems in the Femoropopliteal Arteries Using IVUS Validation and Reliability Testing

Purpose: Objective assessment of dissection severity is difficult. Recognition of this has led to the creation of classification systems. This study investigated the performance of the National Heart Lung and Blood Institute (NHLBI) and Kobayashi systems at differentiating severity of femoropopliteal dissection using intravascular ultrasound (IVUS) as the reference standard. Comparison between the 2 systems and the inter- and intra-observer reliability were also investigated. Materials and Methods: Angiographic and IVUS imaging was assessed in 51 cases sourced from a RCT investigating the use of IVUS in femoropopliteal disease. A total of 2 readers independently scored the angiography images according to NHLBI and Kobayashi dissection classification systems and a consensus score was obtained for each system in each case. The NHLBI classification was condensed into 3 grades of dissection to allow comparison between systems. Dissection length, dissection arc, minimum lumen area, and lumen area stenosis were obtained from the IVUS imaging. IVUS parameters were compared between grades of severity for both systems. Agreement in grading between the systems was assessed and IVUS parameters for each level of dissection severity were compared between systems. Inter and intra-observer agreement tested for each system. Results: Dissection was present on IVUS in 92.2% (47/51) of cases and angiography identified 78.7% (37/47) of these. No difference was present in any IVUS parameters between mild and severe dissections with either classification system. No difference in IVUS findings was present for the same grades of dissection between systems. The 2 systems agreed on severity grade in 47 of 51 cases. The inter-observer agreement was for NHLBI was k=0.549 and k=0.627 for Kobayashi. Intra-observer agreement for NHLBI was k=0.633 and k=0.633 and for Kobayashi was k=0.657 and k=0.297. Conclusion: The lack of difference in IVUS parameters between mild and severe dissection for the NHLBI and Kobayashi systems raises doubts about their ability to effectively differentiate dissection severity. Weak to moderate reliability suggests that variability in interpreting dissection may be higher than acceptable. IVUS imaging is more sensitive for detecting dissection than angiography and research is required to establish the value of adding IVUS to dissection classification systems.

Impact of Intravascular Ultrasound–Guided Optimal Stent Expansion on 3-Year Hard Clinical Outcomes

Background: Although stent underexpansion on intravascular ultrasound (IVUS) has been a major predictor for adverse outcomes in previous studies, these studies have primarily focused on angiographic restenosis or repeat revascularization with short-term follow-up. This study sought to evaluate the long-term benefit of different criteria for IVUS-defined optimal stent expansion on hard clinical outcomes. Methods: From the pooled data of 2 randomized trials, IVUS-XPL (Impact of Intravascular Ultrasound Guidance on the Outcomes of Xience Prime Stents in Long Lesions) and ULTIMATE (Intravascular Ultrasound Guided Drug Eluting Stents Implantation in All-Comers Coronary Lesions) that compared IVUS- versus angiography-guided drug-eluting stent implantation, a total of 1254 patients with IVUS-guided drug-eluting stent implantation into 1484 long lesions (implanted stent length, ≥28 mm) were included. Different criteria for IVUS-defined optimal stent expansion based on minimum stent area (MSA) as an absolute measure or MSA relative to reference lumen area were applied and validated. The primary end point was composite of cardiac death, target lesion–related myocardial infarction, or stent thrombosis at 3 years. Results: The rate of the primary end point was lower in patients with optimal stent expansion versus those without optimal stent expansion according to 3 IVUS-defined optimal stent expansion criteria: MSA >5.5 mm 2 (0.5% versus 2.2%; hazard ratio, 0.21 [95% CI, 0.06–0.75]; P =0.008), MSA >5.0 mm 2 (0.6% versus 2.6%; hazard ratio, 0.24 [95% CI, 0.09–0.68]; P =0.003), and MSA/distal reference lumen area >90% (0.5% versus 2.4%; hazard ratio, 0.32 [95% CI, 0.12–0.88]; P =0.019). Achieving other relative expansion criteria, MSA/distal reference lumen area >100% or 80% or MSA/average reference lumen area >90% or 80%, was not associated with a reduction in hard clinical events. Conclusions: In patients undergoing IVUS-guided drug-eluting stent implantation for long lesions, achieving optimal stent expansion of MSA >5.5 mm 2 , >5.0 mm 2 , or MSA/distal reference lumen area >90% was associated with improved long-term hard clinical outcomes.

Prediction of the functional significance of the left main stenosis using frequency domain optical coherence tomography

Background Frequency domain optical coherence tomography (FD-OCT) has been used for the assessment of non-ostial left main coronary artery stenosis (LM). However, no study has evaluated the use of this imaging technique for the prediction of functional significance of LM lesions determined by the fractional flow reserve (FFR). Purpose The aim of this study was to assess the safety and diagnostic efficacy of FD-OCT in identifying functional severity of the LM stenosis determined by (FFR). Methods One hundred one patients with LM lesion (20–70% diameter stenosis angiographically) underwent FFR measurement and FD-OCT imaging of the LM. The following parameters were measured by FD-OCT in the LM: reference lumen area (RLA), reference lumen diameter (RLD), minimum lumen area (MLA), minimum lumen diameter (MLD), % lumen area stenosis, % diameter stenosis. Results The LM lesions were visible and measurable by FD-OCT in 88/101 (87.1%) patients. However lesions with ostial location were analyzable by FD-OCT only in 17/30 (56.4%) patients (Figure 1). FFR at maximum hyperemia was ≤0.80 in 39/88 (44.3%) patients. FFR values were correlated significantly with FD-OCT derived LM lumen parameters. Receiver operating characteristic curves showed that an MLA cutoff value of 5,38 mm2 had the highest sensitivity and specificity of 82% and 81% respectively (Figure 2A), followed by an MLD of 2.43 mm (sensitivity 77%, specificity 72%) (Figure 2B) and an %AS of 60% (sensitivity 72%, specificity 72%) (Figure 2C) for predicting FFR ≤0.80. Conclusions FD-OCT is safe and feasible imaging technique for the assessment of a LM stenosis except the ostial LM lesions which are analyzable in half of the cases. An FD-OCT derived MLA of ≤5.38 mm2 strongly predicts the functional severity of a LM lesion. FUNDunding Acknowledgement Type of funding sources: None. Angiography and OCT image of LM stenosis ROC curves of MLA, MLD and AS

The “Fracking” technique: a novel approach to crack deep calcified plaque in the common femoral artery with hydraulic pressure

Background The patency achieved by conventional peripheral interventions for atherosclerotic lesions in the common femoral artery (CFA), called the “no stenting zone”, is not superior to that achieved by surgical endarterectomy due to calcified plaque occupying the area. Plaque modification strategies to obtain acute gain in CFA patency provide the better clinical outcomes than standard balloon angioplasty. Atherectomy devices, which focus on the modification of superficial calcifications, contribute to the improvement of clinical outcomes. However, deep calcifications resist vessel expansion such that luminal gain is not easily achieved. Main text We propose a novel calcified plaque modification technique, named the “fracking technique” (FT). The term fracking refers to how a rock is fractured by the high hydraulic pressure. In this technique, deep calcifications are cracked with hydraulic pressure via a balloon indeflator through an 18-gauge needle, which punctures calcifications to achieve greater acute luminal gain. Case 1 involved an 81-year-old male with eccentric calcified plaque in the right CFA. Conventional balloon angioplasty for the lesion yielded a suboptimal minimal lumen area (MLA), which increased from 6.2 to 10.7-mm2 on intravascular ultrasound (IVUS). The FT was implemented to obtain a larger MLA. After the FT was repeated at three locations at up to 8-atm, a greater MLA of 27.1-mm2 was achieved without complications. Case 2 involved a 72-year-old male undergoing hemodialysis due to diabetes mellitus who presented with ischemic pain in his right limbs at rest due to severe stenosis with eccentric calcification in the distal CFA. The MLA on IVUS before and after balloon angioplasty was 10.0-mm2 and 13.1-mm2, respectively, and this result was still suboptimal. The FT was attempted and successfully yielded a greater MLA of 28.9-mm2 without complications. Restenosis has not been detected for 2 years follow-up period. Conclusions The FT is an effective option for treating calcified CFA lesions to achieve a larger lumen area. Long-term follow-up studies are necessary.

Automatic detection of vessel structure by deep learning using intravascular ultrasound images of the coronary arteries

Intravascular ultrasound (IVUS) is a diagnostic modality used during percutaneous coronary intervention. However, specialist skills are required to interpret IVUS images. To address this issue, we developed a new artificial intelligence (AI) program that categorizes vessel components, including calcification and stents, seen in IVUS images of complex lesions. When developing our AI using U-Net, IVUS images were taken from patients with angina pectoris and were manually segmented into the following categories: lumen area, medial plus plaque area, calcification, and stent. To evaluate our AI’s performance, we calculated the classification accuracy of vessel components in IVUS images of vessels with clinically significantly narrowed lumina (< 4 mm2) and those with severe calcification. Additionally, we assessed the correlation between lumen areas in manually-labeled ground truth images and those in AI-predicted images, the mean intersection over union (IoU) of a test set, and the recall score for detecting stent struts in each IVUS image in which a stent was present in the test set. Among 3738 labeled images, 323 were randomly selected for use as a test set. The remaining 3415 images were used for training. The classification accuracies for vessels with significantly narrowed lumina and those with severe calcification were 0.97 and 0.98, respectively. Additionally, there was a significant correlation in the lumen area between the ground truth images and the predicted images (ρ = 0.97, R2 = 0.97, p < 0.001). However, the mean IoU of the test set was 0.66 and the recall score for detecting stent struts was 0.64. Our AI program accurately classified vessels requiring treatment and vessel components, except for stents in IVUS images of complex lesions. AI may be a powerful tool for assisting in the interpretation of IVUS imaging and could promote the popularization of IVUS-guided percutaneous coronary intervention in a clinical setting.

Fracking Technique: The Novel Approach To Crack Deep Calcified Plaque In Common Femoral Artery With Hydraulic Pressure.

Background:The patency of conventional peripheral intervention for atherosclerotic lesions in common femoral artery (CFA), called “no stenting zone”, are not superior to surgical endarterectomy due to calcified plaque occupying the area. Plaque modification strategies to obtain acute gain in CFA provide the better clinical outcome compared to standard balloon angioplasty. Atherectomy devices, which focus on modification of superficial calcification, contribute to the improvement of clinical outcomes. However, deep calcium resists vessel expansion so that luminal gain is not easily achieved. Main text:We propose a novel calcified plaque modification technique, named the” Fracking technique”. The term fracking refers to how a rock is fractured apart by the high hydraulic pressure. This technique is to crack deep calcification with hydraulic pressure with a balloon indeflator through 18-gauge needle, which punctures into calcification in order to obtain larger acute luminal gain. Case 1 involved an 81-year-old male with eccentric calcified plaque in right CFA. Conventional balloon angioplasty for the lesion provided the suboptimal minimal lumen area (MLA) from 6.2 to 10.7mm2 with intravascular ultrasound (IVUS) measurement. Fracking technique was implemented to obtain the larger MLA. After fracking was repeated three times until there were no more Fracking points, a much larger MLA of 27.1mm2 was achieved without complications. Case 2 involved a 72-year-old male undergoing hemodialysis presented with ischemic rest pain of his right limbs due to severe stenosis with eccentric calcification in distal CFA to proximal superficial femoral artery. MLAs with IVUS before and after ballooning were 10.0mm2, 13.1mm2, respectively. None of the results of MLA lived up to our expectation. Fracking technique was attempted, and MLA of 28.9mm2 was successfully obtained after this technique. No complications observed. Conclusions:Fracking technique was effective for severe calcified lesion in CFA to obtain significantly larger lumen area which will lead to long-term patency superior to conventional peripheral intervention.