Publications by authors named "Toshio Takayama"

49 Publications

Generation of Concentration Gradients by a Outer-Circumference-Driven On-Chip Mixer.

Micromachines (Basel) 2021 Dec 31;13(1). Epub 2021 Dec 31.

Department of Mechanical Engineering, Tokyo Institute of Technology, 2-12-1, Ookayama, Tokyo 152-8552, Japan.

The concentration control of reagents is an important factor in microfluidic devices for cell cultivation and chemical mixing, but it is difficult to realize owing to the characteristics of microfluidic devices. We developed a microfluidic device that can generate concentration gradients among multiple main chambers. Multiple main chambers are connected in parallel to the body channel via the neck channel. The main chamber is subjected to a volume change through a driving chamber that surrounds the main chamber, and agitation is performed on the basis of the inequality of flow caused by expansion or contraction. The neck channel is connected tangentially to the main chamber. When the main chamber expands or contracts, the flow in the main chamber is unequal, and a net vortex is generated. The liquid moving back and forth in the neck channel gradually absorbs the liquid in the body channel into the main chamber. As the concentration in the main chamber changes depending on the pressure applied to the driving chamber, we generated a concentration gradient by arranging chambers along the pressure gradient. This allowed for us to create an environment with different concentrations on a single microchip, which is expected to improve observation efficiency and save space.
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http://dx.doi.org/10.3390/mi13010068DOI Listing
December 2021

Ten-Hour Simulation Training Improved the Suturing Performance of Medical Students.

Ann Vasc Surg 2022 Jan 5. Epub 2022 Jan 5.

Division of Vascular Surgery, Department of Surgery, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo Japan.

Purpose: We evaluated the effectiveness of an original simulation training system in improving the suturing performance of medical students using a previously developed web application for scoring suturing performance.

Methods: Medical students were recruited for this study and trained on vascular graft anastomosis. Prosthetic grafts were anastomosed and evaluated after orientation, and after 1 hr and 10 hr after training. Vascular surgeons were recruited as controls. Using a previously developed web application, suturing performance was evaluated on the basis of procedural time, coefficient of variation of bite (length of a stitch across the graft), coefficient of variation of pitch (interval between stitches), and skewness (symmetry of the angles between stitches).

Results: Forty-eight medical students and 10 vascular surgeons were recruited. After 1 hr of training, only the students' procedural time improved. After 10 hr of training, all scores improved compared with those in the first trial, and all students' scores except procedural time were statistically similar to those of the vascular surgeons.

Conclusions: Ten-hour training improved all factors, including bite, pitch, skewness, and time. Our simple and inexpensive training system and web application for calculating anastomosis scores can be a useful open educational resource.
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http://dx.doi.org/10.1016/j.avsg.2021.12.076DOI Listing
January 2022

Impact of Inferior Mesenteric Artery Occlusion on the Calibre of Collateral Arteries of the Colon.

Anticancer Res 2021 Oct;41(10):5189-5193

Department of Surgical Oncology, The University of Tokyo, Tokyo, Japan.

Background/aim: The inferior mesenteric arteries (IMA) are occluded in some colorectal cancer patients. This study evaluated the impact of IMA occlusion on the calibre of collateral arteries.

Patients And Methods: As an IMA obstruction model, 20 patients who underwent abdominal aortic aneurysm surgery, with ligated, excluded, or embolised IMA, were enrolled. Changes in the calibre of the left colic arteries (LCAs) and marginal arteries after surgeries were evaluated.

Results: The cross-sectional area of the LCA significantly increased after surgery (4.34 mm vs. 6.34 mm, p=0.0009) and that of the marginal artery did not change significantly (2.69 mm vs. 3.01 mm, p=0.33).

Conclusion: The calibre of the LCA increased after IMA occlusion. The descending branch of the LCA should be confirmed preoperatively to preserve blood flow during a low tie procedure.
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http://dx.doi.org/10.21873/anticanres.15337DOI Listing
October 2021

A Radiation-Crosslinked Gelatin Hydrogel That Promotes Tissue Incorporation of an Expanded Polytetrafluoroethylene Vascular Graft in Rats.

Biomolecules 2021 07 27;11(8). Epub 2021 Jul 27.

Division of Vascular Surgery, Department of Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo 113-8655, Japan.

A prosthetic vascular graft that induces perigraft tissue incorporation may effectively prevent serious sequelae such as seroma formation and infection. Radiation-crosslinked gelatin hydrogel (RXgel) mimics the chemical and physical properties of the in vivo extracellular matrix and may facilitate wound healing by promoting tissue organization. Fibroblasts cultured on RXgel actively migrated into the gel for up to 7 days. RXgels of three different degrees of hardness (Rx[10], soft; Rx[15], middle; Rx[20], hard) were prepared, and small disc-like samples of RXgels were implanted into rats. In vitro and in vivo results indicated that Rx[10] was too soft to coat vascular grafts. Thus, expanded polytetrafluoroethylene (ePTFE) vascular grafts coated with RXgel were developed using Rx[15] and Rx[20] gels, and ring-shaped slices of the graft were implanted into rats. Alpha-smooth muscle actin (αSMA) and type III collagen (Col-III) levels were detected by immunohistochemistry. Immunohistochemical staining for αSMA and Col-III demonstrated that RXgel-coated vascular grafts induced more granulation tissue than non-coated grafts on days 14 and 28 after implantation. RXgel-coated ePTFE vascular grafts may provide a solution for patients by reducing poor perigraft tissue incorporation.
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http://dx.doi.org/10.3390/biom11081105DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8391276PMC
July 2021

Multilayered Human Skeletal Muscle Myoblast Sheets Promote the Healing Process After Colonic Anastomosis in Rats.

Cell Transplant 2021 Jan-Dec;30:9636897211009559

Cardiovascular Research Institute, 13155Yokohama City University, Yokohama, Kanagawa, Japan.

Colorectal anastomotic leakage is one of the most feared and fatal complications of colorectal surgery. To date, no external coating material that can prevent anastomotic leakage has been developed. As myoblasts possess anti-inflammatory capacity and improve wound healing, we developed a multilayered human skeletal muscle myoblast (HSMM) sheet by periodic exposure to supraphysiological hydrostatic pressure during repeated cell seeding. We assessed whether the application of an HSMM sheet can promote the healing process after colonic anastomosis. Partial colectomy and insufficient suturing were employed to create a high-risk colo-colonic anastomosis model in 60 nude rats. Rats were divided into a control group ( = 30) and an HSMM sheet group ( = 30). Macroscopic findings, anastomotic bursting pressure, and histology at the colonic anastomotic site were evaluated on postoperative day (POD) 3, 5, 7, 14, and 28. The application of an HSMM sheet significantly suppressed abscess formation at the anastomotic site compared to the control group on POD3 and 5. The anastomotic bursting pressure in the HSMM sheet group was higher than that in the control group on POD3 and 5. Inflammatory cell infiltration in the HSMM sheet group was significantly suppressed compared to that in the control group throughout the time course. Collagen deposition in the HSMM sheet group on POD3 was significantly abundant compared to that in the control group. Regeneration of the mucosa at the colonic anastomotic site was promoted in the HSMM sheet group compared to that in the control group on POD14 and 28. Immunohistochemical analysis demonstrated that surviving cells in the HSMM sheet gradually decreased with postoperative time and none were detected on POD14. These results suggest that the application of a multilayered HSMM sheet may prevent postoperative colonic anastomotic leakage.
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http://dx.doi.org/10.1177/09636897211009559DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8076781PMC
November 2021

Usefulness of duplex ultrasonography to detect collagen sponge misplacement into the arterial lumen during the use of Angio-Seal: A case report.

SAGE Open Med Case Rep 2021 30;9:2050313X211004818. Epub 2021 Mar 30.

Department of Clinical Laboratory Medicine, The University of Tokyo, Tokyo, Japan.

A 76-year-old man who had undergone percutaneous coronary intervention suffered intermittent claudication. Duplex ultrasonography revealed superficial femoral artery stenosis with an intraluminal heterogeneous echogenic mass. We suspected that stenosis was caused by the puncture procedure of the Angio-Seal. Open surgery revealed that a collagen sponge that should have been outside the arterial wall was misplaced in the wall with massive granulation, and atherectomy with patchplasty was performed. Vessel deterioration was considered due to several factors, including inappropriate access site, arterial wall calcification, and comorbidities like Behçet's disease. Ultrasonography is a convenient and useful method to evaluate arterial lesions.
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http://dx.doi.org/10.1177/2050313X211004818DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8013637PMC
March 2021

Carotid Stump Pressure and Contralateral Internal Carotid Stenosis Ratio During Carotid Endarterectomies: 1D-0D Hemodynamic Simulation of Cerebral Perfusion.

Ann Vasc Dis 2021 Mar;14(1):39-45

Division of Vascular Surgery, Department of Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.

We selectively place carotid shunting when ipsilateral mean stump pressure is less than 40 mmHg during carotid endarterectomy (CEA). This study aimed to assess the validity of our selective shunting criterion by 1D-0D hemodynamic simulation technology. We retrospectively reviewed 88 patients (95 cases) of CEA and divided them into two groups based on the degree of contralateral internal carotid artery (ICA) stenosis ratio, which was determined as severe when the peak systolic velocity ratio of the ICA to the common carotid artery was ≥4 by carotid duplex ultrasonography. Patients with severe stenosis or occlusion in contralateral ICA were classified as hypoperfusion group, and those without such contralateral ICA obstruction were classified as control group. Perioperatively, the mean carotid stump pressures were 33 mmHg in hypoperfusion group and 46 mmHg in the control group (P=0.006). We simulated changes in carotid stump pressure according to the changes in the contralateral ICA stenosis ratio. 1D-0D simulation indicated a sharp decline in carotid stump pressure when the contralateral stenosis ratio was >50%, while peripheral pressure of the middle cerebral arteries declined sharply at a ≥70% contralateral stenosis ratio. At this ratio, the direction of the ipsilateral cerebral arterial flow became inverted, the carotid stump pressure became dependent on the basilar artery circulation, and the ipsilateral middle cerebral artery became hypoperfused. Our clinical and computer-simulated results confirmed the validation of our carotid shunting criterion and suggested that contralateral ICA stenosis ratio over 70% is a safe indication of selective shunting during CEA.
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http://dx.doi.org/10.3400/avd.oa.20-00166DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7991701PMC
March 2021

The CR9 element is a novel mechanical load-responsive enhancer that regulates natriuretic peptide genes expression.

FASEB J 2021 04;35(4):e21495

Department of Medical Biochemistry, Graduate School of Medicine/Frontier Biosciences, Osaka University, Suita, Japan.

Enhancers regulate gene expressions in a tissue- and pathology-specific manner by altering its activities. Plasma levels of atrial and brain natriuretic peptides, encoded by the Nppa and Nppb, respectively, and synthesized predominantly in cardiomyocytes, vary depending on the severity of heart failure. We previously identified the noncoding conserved region 9 (CR9) element as a putative Nppb enhancer at 22-kb upstream from the Nppb gene. However, its regulatory mechanism remains unknown. Here, we therefore investigated the mechanism of CR9 activation in cardiomyocytes using different kinds of drugs that induce either cardiac hypertrophy or cardiac failure accompanied by natriuretic peptides upregulation. Chronic treatment of mice with either catecholamines or doxorubicin increased CR9 activity during the progression of cardiac hypertrophy to failure, which is accompanied by proportional increases in Nppb expression. Conversely, for cultured cardiomyocytes, doxorubicin decreased CR9 activity and Nppb expression, while catecholamines increased both. However, exposing cultured cardiomyocytes to mechanical loads, such as mechanical stretch or hydrostatic pressure, upregulate CR9 activity and Nppb expression even in the presence of doxorubicin. Furthermore, the enhancement of CR9 activity and Nppa and Nppb expressions by either catecholamines or mechanical loads can be blunted by suppressing mechanosensing and mechanotransduction pathways, such as muscle LIM protein (MLP) or myosin tension. Finally, the CR9 element showed a more robust and cell-specific response to mechanical loads than the -520-bp BNP promoter. We concluded that the CR9 element is a novel enhancer that responds to mechanical loads by upregulating natriuretic peptides expression in cardiomyocytes.
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http://dx.doi.org/10.1096/fj.202002111RRDOI Listing
April 2021

On-Chip Micro Mixer Driven by Elastic Wall with Virtual Actuator.

Micromachines (Basel) 2021 Feb 21;12(2). Epub 2021 Feb 21.

Department of Mechanical Engineering, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan.

In this paper, we propose an on-chip micromixer driven by an elastic wall with a virtual actuator. The on-chip micro mixer is composed of a circular chamber surrounded by a ring-shaped channel under isolation with an elastic wall. When vibrational pressure is put on the driving channel by an actuator, the volume of the circular chamber changes through the deformation of the elastic wall, as if there exists a virtual actuator near the wall. As a result, the liquid in the circular chamber is pushed out and pulled through the neck channel. This action creates a swirling flow in the circular chamber while maintaining isolation from the driving channel. Through experiments, we confirmed the swirling flow under an isolated environment using an air-based valve. The advantage of this approach is that the micromixer can be designed with a single layer having a simple mechanism.
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http://dx.doi.org/10.3390/mi12020217DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7926952PMC
February 2021

Scaffold-free tissue-engineered arterial grafts derived from human skeletal myoblasts.

Artif Organs 2021 Aug 18;45(8):919-932. Epub 2021 Mar 18.

Cardiovascular Research Institute, Yokohama City University, Yokohama, Japan.

Tissue-engineered vascular grafts (TEVGs) are in urgent demand for both adult and pediatric patients. Although several approaches have utilized vascular smooth muscle cells (SMCs) and endothelial cells as cell sources for TEVGs, these cell sources have a limited proliferative capacity that results in an inability to reconstitute neotissues. Skeletal myoblasts are attractive cell sources as they possess high proliferative capacity, and they are already being tested in clinical trials for patients with ischemic cardiomyopathy. Our previous study demonstrated that periodic hydrostatic pressurization (PHP) promoted fibronectin fibrillogenesis in vascular SMCs, and that PHP-induced extracellular matrix (ECM) arrangements enabled the fabrication of implantable arterial grafts derived from SMCs without using a scaffold material. We assessed the molecular response of human skeletal myoblasts to PHP exposure, and aimed to fabricate arterial grafts from the myoblasts by exposure to PHP. To examine the PHP-response genes, human skeletal myoblasts were subjected to bulk RNA-sequencing after PHP exposure. Gene-set enrichment analysis revealed significant positive correlations between PHP exposure and vascular development-related genes. Real-time polymerase chain reaction (RT-PCR) demonstrated that PHP significantly upregulated collagen and elastic fiber formation-related gene expression, such as fibronectin, lysyl oxidase, collagen type I α1, collagen type IV α1, and tropoelastin. Based on these findings showing the potential role of PHP in vessel formation, we fabricated arterial grafts by repeated cell seeding and exposure to PHP every 24 hours. The resultant 15-layered myoblast grafts had high collagen content, which provided a tensile rupture strength of 899 ± 104 mm Hg. Human skeletal myoblast grafts were implanted as patch grafts in the aorta of immunosuppressed rats and found to be endothelialized and completely patent until the endpoint of 60 postoperative days. Implanted human myoblasts were gradually replaced by host-derived cells, which successfully formed vascular neotissues with layered elastic fibers. These findings suggest that human skeletal myoblasts have the potential to be a feasible cell source for scaffold-free implantable arterial grafts under PHP culture conditions.
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http://dx.doi.org/10.1111/aor.13930DOI Listing
August 2021

High aneurysm wall enhancement values are associated with late sac shrinkage after endovascular repair of abdominal aortic aneurysms.

Medicine (Baltimore) 2021 Jan;100(2):e24133

Division of Vascular Surgery, Department of Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.

Abstract: To analyze the correlation between aneurysm wall enhancement (AWE) values and early and late sac shrinkage after endovascular aneurysm repair (EVAR).We retrospectively analyzed 28 patients who underwent EVAR for abdominal aortic aneurysms (AAA) using a bifurcated main body stent graft. The value of AWE in the slice of the maximum AAA diameter was measured using a volumetric analysis of computed tomography images. Sac measurements before EVAR and more than 10 months after EVAR were compared, and the maximum sac shrinkage rate was calculated.The AWE value immediately after (4 to 7 days) EVAR correlated positively with the sac shrinkage rate (R2 = 0.0139). The AWE value at 6 months after EVAR was also strongly correlated with the sac shrinkage rate (R2 = 0.4982).Higher AWE values at 6 months after EVAR were strongly associated with the sac volume shrinkage rate. High AWE values may be a predictive factor for sac shrinkage and may aid in the selection of the appropriate clinical strategy after EVAR.
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http://dx.doi.org/10.1097/MD.0000000000024133DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7808495PMC
January 2021

A comparison of subjective clinical and objective judgement of abdominal aortic aneurysm morphology.

Int Angiol 2021 Apr 19;40(2):138-142. Epub 2021 Jan 19.

Graduate School, Department of Mechanical Engineering, Shibaura Institute of Technology, Tokyo, Japan.

Background: We compared the subjective, clinical judgement of "saccular" morphology with the objective judgement of mechanical structural analysis.

Methods: Using structural analysis with the finite element method, we previously created a simple model of abdominal aortic aneurysm (AAA) that visualized the distribution of the maximum principal stress (MPS) in the aortic wall and identified the area of prominent stress. AAA "saccular" morphology was determined according to the area showing MPS>0.03 MPa. AAAs with low aspect ratio (horizontally long AAA sac) and small fillet radius were defined as "saccular." Twelve vascular surgeons were recruited. First, they judged the AAA as saccular or fusiform with 3-dimensional images at their clinical impression (subjective "eyeball" judgement). Second, they applied the deformable figure tools on the simple AAA-shaped sagittal view in the application model for 30 AAA cases. From the data of the tools applied, the mechanical structural analysis was performed semi-automatically and the morphology was judged with the objective "simple application."

Results: The structural analysis revealed that only one case was judged as saccular by 11 out of 12 surgeons and the other 29 AAAs were judged as fusiform by two-thirds or more of the surgeons. In contrast, 5 cases were subjectively judged as saccular by eight and more of the surgeons.

Conclusions: The clinical judgement of AAA saccular morphology by the vascular surgeons was different from the judgement derived from the mechanical structural analysis using the application model. The saccular morphology may be theoretically rare in AAAs.
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http://dx.doi.org/10.23736/S0392-9590.21.04591-0DOI Listing
April 2021

Push/Pull Inequality Based High-Speed On-Chip Mixer Enhanced by Wettability.

Micromachines (Basel) 2020 Oct 21;11(10). Epub 2020 Oct 21.

Graduate School of Science and Engineering, Meijo University, Aichi 468-8502, Japan.

In this paper, a high-speed on-chip mixer using two effects is proposed, i.e., push/pull inequality and wettability. Push/pull inequality and wettability are effective for generating a rotational fluid motion in the chamber and for enhancing the rotational speed by reducing the viscous loss between the liquid and channel wall, respectively. An on-chip mixer is composed of three components, a microfluidic channel for making the main fluid flow, a circular chamber connected to the channel for generating a rotational flow, and an actuator connected at the end of the channel allowing a push/pull motion to be applied to the liquid in the main channel. The flow patterns in the chamber under push/pull motions are nonreversible for each motion and, as a result, produce one-directional torque to the fluid in the circular chamber. This nonreversible motion is called push/pull inequality and eventually creates a swirling flow in the chamber. Using hydrophilic treatments, we executed the experiment with a straight channel and a circular chamber to clarify the mixing characteristics at different flow speeds. According to the results, it is confirmed that the swirling velocity under appropriately tuned wettability is 100 times faster than that without tuning.
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http://dx.doi.org/10.3390/mi11100950DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7589582PMC
October 2020

A case of endovascular therapy for treating idiopathic arterial deteriorations of unknown etiology.

Int J Surg Case Rep 2020 30;76:202-206. Epub 2020 Sep 30.

Division of Vascular Surgery, Department of Surgery, The University of Tokyo, Tokyo, Japan. Electronic address:

Introduction: Peripheral artery pseudoaneurysm as a consequence of arterial deterioration is relatively rare in young populations, who typically lack an atherosclerotic background. Such pseudoaneurysms are known to pose a risk of rupture, which is correlated with high mortality and morbidity rates. Pseudoaneurysms are more prone to rupture than true aneurysms are, as their vessel walls tear more easily. We present the case of a 50-year-old patient who had multiple arterial deteriorations.

Case Presentation: The patient experienced backache, and computed tomography revealed a tear of the right renal artery, and a pseudoaneurysm of the left internal iliac artery. He had a history of graft replacement for the right superficial artery pseudoaneurysm, which had been occluded. Although various tests were performed for differential diagnosis, the etiology was unidentified. Considering the suspected vascular fragility and failure of previous direct intervention, these 2 lesions were treated by placing endografts simultaneously.

Discussion: We investigated various diseases causing vascular fragility in the reported case, such as vascular Behçet disease, vascular Ehlers-Danlos syndrome, fibromuscular dysplasia, and segmental arterial mediolysis. However, these were all excluded and the etiology remains unclear. Progress in endovascular techniques enables the use of minimally invasive treatment in patients with vascular fragility.

Conclusion: When vascular fragility may exist, endovascular treatment is a desirable option, as it can be performed repetitively and is less invasive.
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http://dx.doi.org/10.1016/j.ijscr.2020.09.178DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7560634PMC
September 2020

Development of a Web Application That Evaluates Suture Performance in Off-the-Job Training.

Ann Vasc Dis 2020 Mar;13(1):52-55

Division of Vascular Surgery, Department of Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.

To create a web application that can evaluate suture performance and assess its quality. We developed the web application using a few cloud computing systems, servers, database, and computing languages. We used 20 anastomosed graft samples for optimizing the application. The images of the anastomosed grafts were captured two-dimensionally. Five vascular surgeons utilized the application to compute the objective score and rank the score of the anastomoses subjectively. Steps for using the application include uploading a two-dimensional image of sutures, tracing the stitch line manually, and pushing the button to have the score displayed. After using this system for more than 1,000 times without server issues or failures, we confirmed its stability and easy accessibility. The system calculated the score within several seconds. The score of the three factors (bite, pitch, and skewness of angle) ranged from 0.25 to 0.76. The error range of the application was acceptable. The interclass correlation coefficient (ICC (2,1)) of the three factors was 0.92. The quality of the application was acceptable considering the low range of interoperator variations in the scores.
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http://dx.doi.org/10.3400/avd.oa.19-00108DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7140167PMC
March 2020

Vascular Ehlers-Danlos Syndrome Diagnosed in a Patient Initiating Hemodialysis.

Kidney Int Rep 2019 Nov 8;4(11):1646-1648. Epub 2019 Aug 8.

Division of Nephrology and Endocrinology, The University of Tokyo Graduate School of Medicine, Tokyo, Japan.

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http://dx.doi.org/10.1016/j.ekir.2019.07.020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6933463PMC
November 2019

Effect of drug-coated balloons in treatment of stenosis of the femoral artery and vein bypass graft not responding to plain old balloon angioplasty: a case report.

Surg Case Rep 2019 Dec 23;5(1):204. Epub 2019 Dec 23.

Division of Vascular Surgery, Department of Surgery, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.

Background: The use of drug-coated balloons (DCBs) with anti-proliferative agents in treating femoropopliteal lesions was approved in Japan in 2017. A better limb salvage rate or amputation-free rate of DCBs relative to plain old balloon angioplasty (POBA) has been reported; however, there is little evidence of the direct effect on intimal hyperplasia (IH).

Case Presentation: A 70-year-old man with chronic limb-threatening ischemia and foot gangrene had undergone bypass surgery from the left common femoral artery to the dorsalis pedis artery 2 years earlier. We evaluated the bypass graft using ultrasonography and found stenosis around the proximal anastomotic site, presumably due to IH. POBA was performed every 3 months due to the repeated re-stenosis of the lesion. Since using the DCB, no restenosis has been detected to date (10 months).

Conclusion: DCB might be an effective tool for treating re-stenosis due to IH or vein grafts that do not respond to POBA.
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http://dx.doi.org/10.1186/s40792-019-0764-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6928170PMC
December 2019

Egg-shell like Calcification as a Protective Factor for Splenic Artery Aneurysm Dilatation.

Ann Vasc Surg 2020 Feb 15;63:193-197. Epub 2019 Oct 15.

Division of Vascular Surgery, Department of Surgery, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku Tokyo, Japan.

Background: The purpose of this study was to evaluate the factors associated with asymptomatic splenic artery aneurysm (SAA) dilatation.

Methods: Among patients with SAA admitted to our department from 2001 to 2018, 70 lesions in 59 patients were selected and analyzed retrospectively. There were no cases of rupture or pregnancy in the follow-up period. We defined egg-shell appearance as SAA with >75% calcification of the outer shell. We measured the dilatation rate (mm/year) and evaluated the comorbidity and anatomical factors using univariate and multiple linear regression models. Post-hoc multiple linear regression models were fitted to evaluate the possible interactions.

Results: The mean age was 61.4 years (range 35-85 years), and the initial aneurysm diameter was 15.1 mm (range 3-47 mm). The mean dilatation rate was 0.26 mm/year (range 0-3.2 mm/year) during the follow-up period (average 4.6 years). Univariate analysis revealed that, portal hypertension (PHT) (P = 0.0003), egg-shell appearance (P = 0.007), and aneurysm diameter > 20 mm (P = 0.05) were significantly associated with the dilatation rate. Multivariate analysis revealed that egg-shell appearance was found to be an independent inverse risk factor of dilatation rate (P = 0.006). The multivariate analysis, including interaction terms, revealed a stronger effect of PHT and diameter >20 mm in cases with no egg-shell appearance (P = 0.08 and P = 0.05 for interactions, respectively).

Conclusions: The egg-shell appearance of SAA was an independent inverse risk factor affecting the SAA dilatation rate. The dilatation rates in the case of PHT and diameter >20 mm were restricted in the presence of the egg-shell appearance.
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http://dx.doi.org/10.1016/j.avsg.2019.08.102DOI Listing
February 2020

A hybrid procedure for middle colic artery aneurysm complicated by chronic juxtarenal segmental aortic occlusion.

J Vasc Surg Cases Innov Tech 2019 Sep 29;5(3):327-331. Epub 2019 Jun 29.

Division of Vascular Surgery, Department of Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.

Here we describe a hybrid procedure, that is, a combination of open isolation and coil embolization, to treat a saccular middle colic artery aneurysm deep behind the pancreas. The middle colic artery provided the collateral blood flow necessary to bypass a chronic segmental aortic occlusion. For preservation of the collateral vessels, we surgically excluded and bypassed the aneurysm and then performed endovascular embolization of the pancreaticoduodenal arteries flowing into the aneurysm, resulting in complete isolation of the aneurysm without jeopardizing blood flow. This hybrid procedure for visceral artery aneurysms can be effective when the collateral vessels need to be preserved.
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http://dx.doi.org/10.1016/j.jvscit.2019.03.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6614582PMC
September 2019

Wound healing after revascularization for critical limb ischemia.

Int Angiol 2019 Jun 16;38(3):225-229. Epub 2019 May 16.

Division of Vascular Surgery, Department of Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.

Background: Wound healing is one of the most important endpoints after revascularization for critical limb ischemia. The purpose of this study was to evaluate the risk factors for wound healing after revascularization for critical limb ischemia (CLI).

Methods: A retrospective study was conducted at a single university hospital, and data were collected retrospectively between January 2005 and September 2016. All admitted patients who were diagnosed with CLI and underwent revascularization for the first time were enrolled. The risk factors for wound healing were analyzed.

Results: The risk factors for wound healing were analyzed in 153 patients. The cumulative rate of wound healing at 12 months after revascularization was 79%. The independent risk factors for wound healing were non-ambulatory status (hazard ratio, 1.95; 95% CI [1.22-3.21], P=0.004), and wound, ischemia and foot infection (WIfI) stage 4 (hazard ratio, 1.89; 95% CI [1.25-2.91], P=0.002).

Conclusions: In our study, non-ambulatory status and WIfI stage 4 were independent risk factors for wound healing after revascularization. WIfI criteria well reflected the prognosis of patients with CLI in wound healing, as well as limb salvage.
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http://dx.doi.org/10.23736/S0392-9590.19.04096-3DOI Listing
June 2019

Phlegmasia cerulea dolens as an initial manifestation of a fistula between a ruptured iliac artery aneurysm and the iliac vein.

J Vasc Surg Cases Innov Tech 2019 Mar 28;5(1):41-44. Epub 2019 Jan 28.

Division of Vascular Surgery, Department of Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.

Phlegmasia cerulea dolens (PCD) is caused by obstruction of limb venous return that may result in venous gangrene and limb loss. We present a case of a fistula between a ruptured right common iliac artery aneurysm and the left common iliac vein (ilioiliac arteriovenous fistula [AVF]), which initially manifested as left PCD and acute renal failure. Resection of the aneurysm and repair of the AVF immediately improved the PCD and acute renal failure. We should be aware that an iliac AVF might present as PCD and should keep this in mind.
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http://dx.doi.org/10.1016/j.jvscit.2018.11.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6355442PMC
March 2019

On-chip density mixer enhanced by air chamber.

Biomicrofluidics 2018 Jul 11;12(4):044108. Epub 2018 Jul 11.

Department of Mechanical Engineering, Osaka University, Suita 565-0871, Japan.

This paper proposes an on-chip density mixer that can achieve even density in a target chamber with a swirling flow enhanced by an air chamber. The system is composed of a main channel, a target chamber where two liquids with different densities are included, an isolated air chamber, and an external vibration pump driven by a piezo actuator at the entrance of the main channel. The air chamber is expected to amplify the vibration owing to structure softening. The amplification would be more pronounced at the resonance frequencies of the structure. We developed the system and conducted experiments. We showed that the swirling motion in the target chamber with an air chamber is stronger than that without an air chamber. We also confirmed that the time resulting in even density is shorter when the pump is driven at a resonance frequency. An air-based virtual valve is introduced for maintaining a constant density in the target chamber.
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http://dx.doi.org/10.1063/1.5033482DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6041114PMC
July 2018

Virtual vortex gear: Unique flow patterns driven by microfluidic inertia leading to pinpoint injection.

Biomicrofluidics 2018 May 20;12(3):034114. Epub 2018 Jun 20.

Department of Mechanical Engineering, Osaka University, Suita 565-0871, Japan.

An interesting phenomenon that vortices are sequentially generated on a microfluidic chip is investigated in this paper. The direction of every two adjacent vortices is opposite to each other, like a set of gears, and thus is named virtual vortex gear (VVG). Both experiments and computational simulations were conducted in order to make clear the mechanism of VVG. The experimental results show that only the flow from a particular point would form vortices and enter the target chamber. A technique of inverse mapping is proposed based on the phenomenon and it demonstrates that only a pinpoint injection is sufficient to control the contents of a microfluidic chamber. VVG can significantly reduce the volume of chemical usage in biological research and has potential for other on-chip applications, such as mixing and valving.
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http://dx.doi.org/10.1063/1.5031082DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6010358PMC
May 2018

Complete Lower Extremity Revascularization via a Hybrid Procedure for Patients with Critical Limb Ischemia.

Vasc Endovascular Surg 2018 May 27;52(4):255-261. Epub 2018 Feb 27.

1 Division of Vascular Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA.

Background: Complete revascularization, achieving inline flow to the foot through at least 1 patent tibioperoneal artery, is considered to be desirable for treating critical limb ischemia (CLI). Hybrid procedure, combined femoral endarterectomy and endovascular treatment, is commonly performed on patients with CLI because they often present with complicated lower extremity lesions involving the common femoral artery. This study aimed to investigate the efficacy of complete revascularization (CR) achieved by hybrid procedure on limb salvage in patients with CLI.

Methods: Between February 2010 and January 2016, 95 limbs (82 patients) were treated by lower extremity hybrid procedure; of these 95 procedures, 61 were for patients with CLI. We defined CR as achieving inline flow to the foot through at least 1 patent tibioperoneal artery. Complete revascularization was performed on 37 limbs, and incomplete revascularization (IR) was performed on 24 limbs. Specific variables, including patient age, male-female ratio, Rutherford classification, preoperative and postoperative ankle-brachial pressure indices (ABIs), follow-up duration (months), primary patency rate, assisted primary patency rate, secondary patency rate, and major amputation rate, were analyzed.

Results: The mean age was similar between the groups 67.2 years in the CR group and 70.7 years in the IR group ( P = .11). Limb ischemia severity was significantly higher in the CR group: 63% of the patients scored Rutherford 5 in the CR group, compared to 30% in the IR group ( P = .027). Mean postoperative ABI was significantly higher in the CR group (CR: 0.87, IR: 0.53; P = .0001). Major amputation rate was higher in the IR group (CR: 2.7%, IR: 13%; P = .29), and major amputation-free survival rate at 3 years after the index procedure was higher in the CR group (CR: 97%, IR: 81%; P = .054).

Conclusion: Complete lower extremity revascularization was beneficial for patients with CLI, avoiding major amputation.
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http://dx.doi.org/10.1177/1538574418761723DOI Listing
May 2018

The relationship between medical expenses and the severity of peripheral arterial disease in Japan.

Heart Vessels 2018 Aug 2;33(8):853-858. Epub 2018 Feb 2.

Division of Vascular Surgery, Department of Surgery, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.

The main objective is to examine whether the severity of peripheral arterial disease (PAD) affects the expenses and hospital stay of the patients who undergo bypass surgery below the inguinal ligament for PAD. Eighty consecutive patients who underwent infrainguinal bypass surgery for PAD between January 2012 and December 2014 were included in the study. Patients were divided into groups according to their critical limb ischemia (CLI) symptoms and the Wound, Ischemia, and Foot Infection (WIfI) classification. As endpoints, we assessed the duration of postoperative hospital stay and expenses during hospitalization. CLI was a significant factor for longer hospital stay and increased medical expenses (p = 0.009 and p = 0.001). In the patients with CLI, significant factors for longer hospital stay and increased medical expenses were (1) history of distal bypass (p = 0.33 and p = 0.003, respectively) and stage 4 local lower limb status in WIfI classification (p = 0.0007 and p = 0.053). PAD severity was associated with prolonged postoperative hospital stay and increased medical expenses. The presence or absence of CLI and its severity according to the WIfI classification correlated with medical expenses and hospital stay duration between the milder and severe groups.
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http://dx.doi.org/10.1007/s00380-018-1127-3DOI Listing
August 2018

Directional tip control technique for optimal stent graft alignment in angulated proximal aortic landing zones.

J Vasc Surg Cases Innov Tech 2017 Jun 25;3(2):51-56. Epub 2017 Apr 25.

Division of Vascular Surgery, University of Wisconsin School of Medicine and Public Health, Madison, Wisc.

Angulated anatomy in the aorta, such as tortuous infrarenal aortic necks or steep aortic arches, is a significant challenge for endovascular aortic repair because it often causes inadequate sealing and fixation, which may lead to treatment failure. We have developed a technique using off-the-shelf equipment to precisely control the deployment of stent grafts in challenging landing zones. The key of this technique is to create a through-and-through wire between two access sites and to use a guiding device over the wire. This technique is best used with stent grafts without nose cones. We present an endovascular aneurysm repair case and a thoracic endovascular aortic repair case with challenging proximal landing zones treated by this technique. In both cases, technical success was attained, and follow-up imaging demonstrated well-aligned stent grafts. Our directional tip control technique is easy and effective. It can be a good technical solution for endovascular aortic treatment in angulated anatomy.
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http://dx.doi.org/10.1016/j.jvscit.2017.02.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5757759PMC
June 2017

LED-CT Scan for pH Distribution on a Cross-Section of Cell Culture Medium.

Sensors (Basel) 2018 Jan 11;18(1). Epub 2018 Jan 11.

Department of Mechanical Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.

In cell culture, the pH of the culture medium is one of the most important conditions. However, the culture medium may have non-uniform pH distribution due to activities of cells and changes in the environment. Although it is possible to measure the pH distribution with an existing pH meter using distributed electrodes, the method involves direct contact with the medium and would greatly increase the risk of contamination. Here in this paper, we propose a computed tomography (CT) scan for measuring pH distribution using the color change of phenol red with a light-emitting diode (LED) light source. Using the principle of CT scan, we can measure pH distribution without contacting culture medium, and thus, decrease the risk of contamination. We have developed the device with a LED, an array of photo receivers and a rotation mechanism. The system is firstly calibrated with different shapes of wooden objects that do not pass light, we succeeded in obtaining their 3D topographies. The system was also used for measuring a culture medium with two different pH values, it was possible to obtain a pH distribution that clearly shows the boundary.
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http://dx.doi.org/10.3390/s18010191DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5795824PMC
January 2018

Thoracic endovascular aortic repair migration and aortic elongation differentiated using dual reference point analysis.

J Vasc Surg 2018 02 21;67(2):382-388. Epub 2017 Sep 21.

Division of Vascular Surgery, School of Medicine and Public Health, University of Wisconsin, Madison, Wisc.

Objective: We evaluated images of patients undergoing a thoracic endovascular aortic repair procedure using two reference points as a means for differentiating stent graft migration from aortic elongation. Conventional standards define migration of a stent graft as an absolute change in the distance from the distal graft ring to a distal landmark ≥10 mm compared with a baseline measurement. Aortic elongation occurs over time in both healthy individuals and patients with aortic disease. Aortic elongation in patients with stent grafts may result in increased distal thoracic aortic lengths over time. False-positive stent graft migration would be defined when these patients meet the standard definition for migration, even if the stent has not moved in relation to the elongating aorta.

Methods: This retrospective study evaluated the aortic length of 23 patients treated with the conformable GORE TAG thoracic endoprosthesis (W. L. Gore & Associates, Flagstaff, Ariz) in three clinical trials (dissection, traumatic injury, and aneurysm). Patients who met the standard definition for migration were selected. A standardized protocol was used to measure aortic centerline lengths, including the innominate artery (IA) to the most distal device ring, the IA to the celiac artery (CA), and the distal ring to the CA. Baseline lengths obtained from the first postoperative image were compared with length measurements obtained from the first interval at which they met the standard definition for migration. The conventional standards for migration using a single reference point were compared with the use of dual reference points.

Results: Of the 23 patients with endograft changes, 20 were deemed to have aortic elongation rather than true migration. The remaining three patients were deemed to have migration on the basis of the IA to distal ring position compared with the IA to CA length change. The IA to CA interval length change was markedly greater in those with elongation compared with migration (23.8 ± 8.4 mm vs -3.5 ± 5.4 mm, respectively; P < .05). The distal ring to CA interval length change was greater in patients showing elongation rather than migration (18.5 ± 6.6 mm vs -9.8 ± 5.4 mm, respectively; P < .05). The distance between the IA and distal ring was similar for elongation and migration.

Conclusions: These results highlight the dynamic changes that can occur in the aorta as a natural consequence of age. Employing two landmarks can account for these changes and proves to be an important factor, among others, in the differentiation of aortic elongation from true stent graft migration.
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http://dx.doi.org/10.1016/j.jvs.2017.07.108DOI Listing
February 2018

Esophagojejunostomy Using the Purse-String Suturing Device After Laparoscopic Total or Proximal Gastrectomy for Gastric Cancer.

World J Surg 2017 10;41(10):2605-2610

Department of Gastric Surgery, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo, Tokyo, Japan.

Background: Performing a safe esophagojejunostomy is important for the standardization of laparoscopic total gastrectomy. We have performed intracorporeal esophagojejunostomy by a circular stapler using the purse-string suturing device that we co-developed. The advantage of this device is that it makes use of the same surgical procedure as open surgery, but it does not depend on the surgeon's technical skills since this device does not require the laparoscopic hand-sewn technique. Furthermore, we have also adapted this device for double-tract reconstruction after laparoscopic proximal gastrectomy. In this study, we present the surgical procedures and postoperative short-term outcomes that were obtained using this novel technique.

Methods: We enrolled 94 patients that underwent intracorporeal esophagojejunostomy by circular stapler using our device after laparoscopic total or proximal gastrectomy for gastric cancer between November 2009 and October 2016.

Results: Postoperative complications related to esophagojejunostomy were due to anastomotic stenosis in two cases (2.1%) and leakage of the jejunum stump in one case (1.1%).

Conclusions: Intracorporeal esophagojejunostomy by circular stapler using the purse-string suturing device is safe and feasible. This method can be one of the standard procedures for performing intracorporeal esophagojejunostomy.
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http://dx.doi.org/10.1007/s00268-017-4033-4DOI Listing
October 2017

Effect of 2% Chlorhexidine Gluconate-Impregnated Cloth on Surgical Site Infections in Vascular Surgery.

Ann Vasc Surg 2017 Aug 22;43:197-202. Epub 2017 Mar 22.

Division of Vascular Surgery, Department of Surgery, University of Wisconsin Hospital and Clinics, Madison, WI.

Background: Surgical site infections (SSIs) are a significant burden to patients and health care systems. This retrospective study evaluates the observed rates of SSI after our institution implemented chlorhexidine gluconate-impregnated (CHG) cloth as a preoperative antiseptic preparation in elective vascular surgery.

Methods: Between March 2011 and January 2012, we reviewed 250 patients who underwent elective vascular surgery who used the CHG cloth preoperatively. Their rate of SSIs was compared with 252 control patients who received the CHG shower preoperatively during the preintervention period. Urgent and emergent cases were excluded. The primary outcome measured was SSI within 30 days of index operation.

Results: There was no baseline difference in mean age, gender distribution, smoking status, diabetes, chronic obstructive pulmonary disease, and the number of patients with body mass index >40 between the cohorts. There was no difference in the overall rate (5.6% vs. 5.6%, P = 1.00) and type of SSIs between the 2 groups, but the control group trended toward deeper infections (4 deep incisional and 2 organ space vs. none and 1, respectively). The control group also had more dirty or infected wound categories (10 vs. 21.4%, P < 0.01) and more perioperative antibiotic errors and hypothermia (P < 0.02).

Conclusions: There was no observed difference in SSI rates before and after implementation of the CHG as the preoperative method of skin decontamination in our retrospective case-control cohorts.
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http://dx.doi.org/10.1016/j.avsg.2016.11.011DOI Listing
August 2017
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