A low chromium diet increases body fat, energy intake and circulating triglycerides and insulin in male and female rats fed a moderately high-fat, high-sucrose diet from peripuberty to young adult age.

Trivalent chromium (Cr) may function to potentiate the action of insulin, but the effects of chromium intakes on metabolic parameters are unclear. Cr is listed as a potentially beneficial element for rodents based on studies that show feeding low quantities affect glucose metabolism. Cr is recommended at 1 mg per kg in rodent diets. This study examined the effects of different levels of dietary Cr on body weight, body composition, energy intake, food efficiency and metabolic parameters of lipid and glucose metabolism in male and female rats when fed from peripuberty to young adult age in the background of a moderately high-fat, high-sucrose diet. Sprague-Dawley CD rats (n = 10 males and 10 females/group) at 35 days of age were assigned by weight to the low (LCr, 0.33 ± 0.06 mg/kg), normal (NCr, 1.20 ± 0.11 mg/kg) or high (HCr, 9.15 ± 0.65 mg/kg) Cr diets. Diets were fed ad libitum for 12 weeks (83 days). At baseline, body weights and composition were similar (p≥0.05) among diet groups. Compared to the NCr group, the LCr group weighed more (p<0.01) and consumed more energy (food) from Day 56 onwards, but food efficiency was unaffected. Following an oral glucose challenge (Day 77), dietary chromium levels did not affect plasma glucose, but fasting plasma insulin and insulin at 30 and 60 min after dosing were higher in the LCr group compared to the NCr group. At the end of the study, whole-body fat, accrued body fat from baseline and fasting serum triglycerides were higher in the LCr group compared to the NCr group. Effects were similar in both sexes and not observed in the HCr group. These data show that low dietary Cr affects metabolic parameters common in chronic diseases underscoring the need for clinical trials to define the nutritional and/or pharmacological effects of Cr.

A soil-inspired dynamically responsive chemical system for microbial modulation.

Interactions between the microbiota and their colonized environments mediate critical pathways from biogeochemical cycles to homeostasis in human health. Here we report a soil-inspired chemical system that consists of nanostructured minerals, starch granules and liquid metals. Fabricated via a bottom-up synthesis, the soil-inspired chemical system can enable chemical redistribution and modulation of microbial communities. We characterize the composite, confirming its structural similarity to the soil, with three-dimensional X-ray fluorescence and ptychographic tomography and electron microscopy imaging. We also demonstrate that post-synthetic modifications formed by laser irradiation led to chemical heterogeneities from the atomic to the macroscopic level. The soil-inspired material possesses chemical, optical and mechanical responsiveness to yield write-erase functions in electrical performance. The composite can also enhance microbial culture/biofilm growth and biofuel production in vitro. Finally, we show that the soil-inspired system enriches gut bacteria diversity, rectifies tetracycline-induced gut microbiome dysbiosis and ameliorates dextran sulfate sodium-induced rodent colitis symptoms within in vivo rodent models.

Qualitative study informing the development and content validity of the HAND-Q: a modular patient-reported outcome measure for hand conditions.

OBJECTIVES: The purpose of this study was to identify and understand the issues that are relevant to patients with hand conditions. The data were used to develop a patient-reported outcome measure (PROM) for adults with hand conditions (HAND-Q) and refine it with input from patients and clinician experts. DESIGN: Semistructured qualitative interviews were used to understand what matters to patients. Cognitive debriefing was used to refine preliminary HAND-Q scales. SETTING: Hand clinics in tertiary healthcare centres in Canada, Australia and USA. PARTICIPANTS: Eligible participants were English-speaking adults who had experienced hand surgery in the preceding 12 months and were at least 4 weeks post-hand surgery A total of 62 in-depth interviews (females, n=34; mean age=65 years) were conducted to develop an item pool and draft the HAND-Q scales. The preliminary scales were refined through cognitive debriefing interviews with 20 participants and feedback from 25 clinician experts. All interviews were audiorecorded, transcribed verbatim and coded using a line-by-line approach. RESULTS: Qualitative data were organised into two top-level domains of health-related quality of life and satisfaction with treatment outcomes. The scales were refined iteratively, and the field-test version included 319 unique items and 20 independently functioning scales. CONCLUSIONS: The HAND-Q is a comprehensive PROM developed using extensive patient and clinician expert input, following established guidelines for PROM development and validation. In the next phase, the psychometric properties of the HAND-Q will be established in an international field test, following which the HAND-Q will be available for use in clinical research and practice .

The HAND-Q: Psychometrics of a New Patient-reported Outcome Measure for Clinical and Research Applications.

The perspective of the patient in measuring the outcome of their hand treatment is of key importance. We developed a hand-specific patient-reported outcome measure to provide a means to measure outcomes and experiences of care from the patient perspective, that is, HAND-Q. METHODS: Data were collected from people with a broad range of hand conditions in hand clinics in six countries between April 2018 and January 2021. Rasch measurement theory analysis was used to perform item reduction and to examine reliability and validity of each HAND-Q scale. RESULTS: A sample of 1277 patients was recruited. Participants ranged in age from 16 to 89 years, 54% were women, and a broad range of congenital and acquired hand conditions were represented. Rasch measurement theory analysis led to the refinement of 14 independently functioning scales that measure hand appearance, health-related quality of life, experience of care, and treatment outcome. Each scale evidenced reliability and validity. Examination of differential item functioning by age, gender, language, and type of hand condition (ie, nontraumatic versus traumatic) confirmed that a common scoring algorithm for each scale could be implemented. CONCLUSIONS: The HAND-Q was developed following robust psychometric methods to provide a comprehensive modular independently functioning set of scales. HAND-Q scales can be used to assess and compare evidence-based outcomes in patients with any type of hand condition.

A Smart Lithium Battery with Shape Memory Function.

Rapidly growing flexible and wearable electronics highly demand the development of flexible energy storage devices. Yet, these devices are susceptible to extreme, repeated mechanical deformations under working circumstances. Herein, the design and fabrication of a smart, flexible Li-ion battery with shape memory function, which has the ability to restore its shape against severe mechanical deformations, bending, twisting, rolling or elongation, is reported. The shape memory function is induced by the integration of a shape-adjustable solid polymer electrolyte. This Li-ion battery delivers a specific discharge capacity of ≈140 mAh g-1 at 0.2 C charge/discharge rate with ≈92% capacity retention after 100 cycles and ≈99.85% Coulombic efficiency, at 20 °C. Besides recovery from mechanical deformations, it is visually demonstrated that the shape of this smart battery can be programmed to adjust itself in response to an internal/external heat stimulus for task-specific and advanced applications. Considering the vast range of available shape memory polymers with tunable chemistry, physical, and mechanical characteristics, this study offers a promising approach for engineering smart batteries responsive to unfavorable internal or external stimulus, with potential to have a broad impact on other energy storage technologies in different sizes and shapes.

Synthetic Lubricants Derived from Plastic Waste and their Tribological Performance.

The energy efficiency, mechanical durability, and environmental compatibility of all moving machine components rely heavily on advanced lubricants for smooth and safe operation. Herein an alternative family of high-quality liquid (HQL) lubricants was derived by the catalytic conversion of pre- and post-consumer polyolefin waste. The plastic-derived lubricants performed comparably to synthetic base oils such as polyalphaolefins (PAOs), both with a wear scar volume (WSV) of 7.5×10-5  mm-3 . HQLs also performed superior to petroleum-based lubricants such as Group III mineral oil with a WSV of 1.7×10-4  mm-3 , showcasing a 44 % reduction in wear. Furthermore, a synergistic reduction in friction and wear was observed when combining the upcycled plastic lubricant with synthetic oils. Life cycle and techno-economic analyses also showed this process to be energetically efficient and economically feasible. This novel technology offers a cost-effective opportunity to reduce the harmful environmental impact of plastic waste on our planet and to save energy through reduction of friction and wear-related degradations in transportation applications akin to synthetic oils.

Calcium exacerbates the inhibitory effects of phytic acid on zinc bioavailability in rats.

BACKGROUND: Complementary feeding of breastfed infants with foods high in bioavailable zinc (Zn) can help meet physiological requirements for Zn. Some infant cereals contain high concentrations of phytic acid (PA) and calcium (Ca) that may reduce absorbable Zn. OBJECTIVES: This study measured PA, Zn and Ca concentrations in selected infant cereals sold in Canada and investigated the effects of dietary PA and Ca at concentrations present in infant cereals on Zn bioavailability in rats. METHODS AND RESULTS: Male Sprague-Dawley rats (36-day old) were fed a control diet containing normal Zn (29.1 mg/kg) and Ca (4.95 g/kg) or six test diets (n = 12/diet group). Test diets were low in Zn (8.91-9.74 mg/kg) and contained low (2.16-2.17 g/kg), normal (5.00-5.11 g/kg) or high (14.6-14.9 g/kg) Ca without or with added PA (8 g/kg). After 2 weeks, rats were killed and Zn status of the rats was assessed. PA, Zn and Ca concentrations in infant cereals (n = 20) differed widely. PA concentrations ranged from undetectable to 16.0 g/kg. Zn and Ca concentrations ranged from 7.0-29.1 mg/kg and 0.8-13.4 g/kg, respectively. The [PA]/[Zn] and [PA × Ca]/[Zn] molar ratios in infants cereals with detectable PA (16 of 20 cereals) ranged from 22-75 and 0.9-14.9 mol/kg, respectively, predicting low Zn bioavailability. Body weight, body composition (lean and fat mass), right femur weight and length measurements and Zn concentrations in serum and femur indicated that diets higher in Ca had a more pronounced negative effect on Zn status of rats fed a PA-supplemented diet. Addition of PA to the diet had a greater negative effect on Zn status when Ca concentration in the diet was higher. CONCLUSION: These results show that, in rats, higher concentrations of dietary Ca and PA interact to potentiate a decrease in bioavailable Zn and may suggest lower Zn bioavailability in infant cereals with higher PA and Ca concentrations.

Does breast reduction surgery improve health-related quality of life? A prospective cohort study in Australian women.

OBJECTIVES: To assess the health burden of breast hypertrophy and the comparative effectiveness of breast reduction surgery in improving health-related quality of life. DESIGN: Prospective cohort study. SETTING: A major public tertiary care hospital in Australia. PARTICIPANTS: Women with symptomatic breast hypertrophy who underwent breast reduction surgery were followed for 12 months. A comparison control cohort comprised women with breast hypertrophy who did not undergo surgery. INTERVENTIONS: Bilateral breast reduction surgery for women in the surgical cohort. MAIN OUTCOME MEASURES: The primary outcome measure was health-related quality of life measured preoperatively and at 3, 6 and 12 months postoperatively using the Short Form-36 (SF-36) questionnaire. Secondary outcome measures included post-surgical complications. RESULTS: 209 patients in the surgical cohort completed questionnaires before and after surgery. 124 patients in the control hypertrophy cohort completed baseline and 12-month follow-up questionnaires. At baseline, both groups had significantly lower scores compared with population norms across all scales (p<0.001). In the surgical cohort significant improvements were seen across all eight SF-36 scales (p<0.001) following surgery. Within 3 months of surgery scores were equivalent to those of the normal population and this improvement was sustained at 12 months. SF-36 physical and mental component scores both significantly improved following surgery, with a mean change of 10.2 and 9.2 points, respectively (p<0.001). In contrast, SF-36 scores for breast hypertrophy controls remained at baseline across 12 months. The improvement in quality of life was independent of breast resection weight and body mass index. CONCLUSION: Breast reduction significantly improved quality of life in women with breast hypertrophy. This increase was most pronounced within 3 months of surgery and sustained at 12-month follow-up. This improvement in quality of life is comparable to other widely accepted surgical procedures. Furthermore, women benefit from surgery regardless of factors including body mass index and resection weight.

Structured silicon for revealing transient and integrated signal transductions in microbial systems.

Bacterial response to transient physical stress is critical to their homeostasis and survival in the dynamic natural environment. Because of the lack of biophysical tools capable of delivering precise and localized physical perturbations to a bacterial community, the underlying mechanism of microbial signal transduction has remained unexplored. Here, we developed multiscale and structured silicon (Si) materials as nongenetic optical transducers capable of modulating the activities of both single bacterial cells and biofilms at high spatiotemporal resolution. Upon optical stimulation, we capture a previously unidentified form of rapid, photothermal gradient-dependent, intercellular calcium signaling within the biofilm. We also found an unexpected coupling between calcium dynamics and biofilm mechanics, which could be of importance for biofilm resistance. Our results suggest that functional integration of Si materials and bacteria, and associated control of signal transduction, may lead to hybrid living matter toward future synthetic biology and adaptable materials.

Prospective Randomized Cohort Study to Explore the Acceptability of Patient-Reported Outcome Measures to Patients of Hand Clinics.

Purpose: The purpose of this randomized prospective cohort study was to assess the acceptability of administering patient-reported outcome measures (PROMs) in the waiting room of hand clinics. Methods: Participants were randomly assigned to receive the Patient-Rated Wrist and Hand Evaluation (PRWHE), Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire, or Michigan Hand Questionnaire (MHQ). Acceptability was measured in terms of data quality, participation, and retention rates. Data quality was determined by the number of incomplete questionnaires, unanswered questions, and unscorable questionnaires. Most frequently unanswered questions were identified. The participant-reported time taken to complete the questionnaires was collected. Results: A total of 491 participants enrolled in this study. A participation rate of 85% with a retention rate of 94% indicated that patients found the administration of PROMs in the waiting room of the clinic to be acceptable. The proportion of missing data for each questionnaire was 4.2% for PRWHE, 3.9% for DASH and 6.3% for MHQ. Whether a questionnaire could be used to generate a score was determined by the scoring rules of each instrument. The proportion of questionnaires that were not completed sufficiently for a score to be generated was 0% for PRWHE, 9% for DASH, and 4% for MHQ. No association was found between whether a questionnaire could generate a score and participants' sex, age, or the nature of the condition. Over 80% of participants reported taking 10 minutes or less to complete the questionnaire. Conclusions: This study shows that hand clinic patients will complete PROMs while waiting for the clinical review. The PRWHE and MHQ groups demonstrated good usability, because less than 5% were unable to produce a score. The usability of the DASH group was lower, because 9% were unable to be scored. This indicates that PRWHE and MHQ are more suitable than DASH to application in a hand clinic setting. Type of study/level of evidence: Therapeutic III.

Outcomes of Breast Reduction Surgery Using the BREAST-Q: A Prospective Study and Comparison with Normative Data.

BACKGROUND: This study aimed to assess breast-related satisfaction and well-being in women with breast hypertrophy before and after breast reduction surgery, and to compare these scores with Australian general population norms, using the BREAST-Q Reduction module. METHODS: A prospective cohort study was conducted between March of 2010 and February of 2016. Participants self-completed the BREAST-Q preoperatively and 12 months postoperatively. Normative BREAST-Q data were generated from women aged 18 years and older for comparison. Statistical analysis was performed and values of p < 0.05 were considered significant. RESULTS: The BREAST-Q was completed by 132 participants preoperatively and 12 months postoperatively. Statistically significant improvements were found following surgery in Satisfaction with Breasts, Psychosocial Well-being, Sexual Well-being, and Physical Well-being. In comparison with normative data, patients with breast hypertrophy had significantly lower scores preoperatively, with scores significantly increasing postoperatively to levels representative of the general population. Satisfaction with outcome was not significantly different between patients who were eligible by traditional insurance requirements (Schnur sliding scale/500-g minimum rule) and those who were not. The presence of surgical complications did not affect change in BREAST-Q scores or postoperative satisfaction with outcome. Differences were observed in mean BREAST-Q scores when comparing generated Australian norms to published U.S. norms. CONCLUSIONS: Breast reduction surgery significantly improves the satisfaction and quality of life in women with breast hypertrophy to a level that is at least equivalent to that of the normative population. Surgery is of benefit to all women, including those who do not meet traditional insurance requirements. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.

International multiphase mixed methods study protocol to develop a cross-cultural patient-reported outcome and experience measure for hand conditions (HAND-Q).

INTRODUCTION: patient-reported outcome measures (PROMs) are instruments used to measure outcomes and experiences of healthcare from the patient perspective. The specific methodology used to develop a PROM should be communicated to establish the quality of the instrument. This mixed methods protocol describes the development of a cross-cultural, internationally applicable PROM for hand conditions, the HAND-Q. METHODS AND ANALYSIS: The multiphase approach used for this study has been previously used with the development of other PROMs by our team (eg, BODY-Q, BREAST-Q, CLEFT-Q, FACE-Q). In Phase I, we establish what important concepts matter to patients with hand conditions. A conceptual framework is developed from a systematic review of existing PROMs in the field and an extensive international qualitative study. Interpretive description is the qualitative approach used. Item generation is based on the qualitative data. The preliminary scales will be created for each theme identified in the conceptual framework. These scales will be refined by cognitive debriefing interviews with participants and expert input. Phase II involves a large international sample of patients with varied hand conditions completing the field-test version of the HAND-Q. The scales will be refined using the modern psychometric approach of Rasch Measurement Theory. Analysis will result in a shortened set of clinically meaningful and scientifically robust HAND-Q scales. ETHICS AND DISSEMINATION: This study is coordinated at Flinders University (Adelaide, Australia) where it has ethics board approval for phase I and phase II. Findings will be published in peer-reviewed journals and presented at local, national and international conferences.

Dietary calcium affects body composition and lipid metabolism in rats.

Calcium (Ca) intakes may affect cardiovascular disease risk by altering body composition (body weight and fat) and serum lipid profile, but results have been inconsistent and the underlying mechanisms are not well understood. The effects of dietary Ca on body composition and lipid metabolism were examined in rats. Male Sprague-Dawley rats were fed high-fat, high-energy diets containing (g/kg) low (0.75Ca, 0.86 ± 0.05; 2Ca, 2.26 ± 0.02), normal (5Ca, 5.55 ± 0.08) or high (10Ca, 11.03 ± 0.17; 20Ca, 21.79 ± 0.15) Ca for 10 weeks. Rats fed the lowest Ca diet (0.75Ca) had lower (p < 0.05) body weight and fat mass compared to other groups. Rats fed the high Ca diets had lower serum total and LDL cholesterol compared to rats fed normal or low Ca. Liver total cholesterol was lower in rats fed high compared to low Ca. In general, liver mRNA expression of genes involved in cholesterol uptake from the circulation (Ldlr), cholesterol synthesis (Hmgcr and Hmgcs1), fatty acid oxidation (Cpt2) and cholesterol esterification (Acat2) were higher in rats fed higher Ca. Apparent digestibility of total trans, saturated, monounsaturated and polyunsaturated fatty acids was lower in rats fed the high compared to the low Ca diets, with the largest effects seen on trans and saturated fatty acids. Fecal excretion of cholesterol and total bile acids was highest in rats fed the highest Ca diet (20Ca). The results suggest little effect of dietary Ca on body composition unless Ca intakes are very low. Decreased bile acid reabsorption and reduced absorption of neutral sterols and saturated and trans fatty acids may contribute to the better serum lipid profile in rats fed higher Ca.

Ultrasound Promoted Step-Growth Polymerization and Polymer Crosslinking Via Copper Catalyzed Azide-Alkyne "Click" Reaction.

Mechano-activated chemistry is a powerful tool for remodeling of synthetic polymeric materials, however, few reactions are currently available. Here we show that using piezochemical reduction of a CuII -based pre-catalyst, a step-growth polymerization occurs via the copper catalyzed azide-alkyne cycloaddition (CuAAC) reaction to form a linear polytriazole. Furthermore, we show that a linear polymer can be crosslinked mechanochemically using the same chemistry to form a solid organogel. We envision that this chemistry can be used to harness mechanical energy for constructive purposes in polymeric materials.

Grafted polymer chains suppress nanoparticle diffusion in athermal polymer melts.

We measure the center-of-mass diffusion of poly(methyl methacrylate) (PMMA)-grafted nanoparticles (NPs) in unentangled to slightly entangled PMMA melts using Rutherford backscattering spectrometry. These grafted NPs diffuse ∼100 times slower than predicted by the Stokes-Einstein relation assuming a viscosity equal to bulk PMMA and a hydrodynamic NP size equal to the NP core diameter, 2Rcore = 4.3 nm. This slow NP diffusion is consistent with an increased effective NP size, 2Reff ≈ 20 nm, nominally independent of the range of grafting density and matrix molecular weights explored in this study. Comparing these experimental results to a modified Daoud-Cotton scaling estimate for the brush thickness as well as dynamic mean field simulations of polymer-grafted NPs in athermal polymer melts, we find that 2Reff is in quantitative agreement with the size of the NP core plus the extended grafted chains. Our results suggest that grafted polymer chains of moderate molecular weight and grafting density may alter the NP diffusion mechanism in polymer melts, primarily by increasing the NP effective size.

Communication: Influence of nanophase segregation on ion transport in room temperature ionic liquids.

We report measurements of the ionic conductivity, shear viscosity, and structural dynamics in a homologous series of quaternary ammonium ionic liquids (ILs) and a prototypical imidazolium-based IL over a wide range of temperatures down to the glass transition. We find that the ionic conductivity of these materials generally decreases, while the shear viscosity correspondingly increases, with increasing volume fraction of aliphatic side groups. Upon crossing an aliphatic volume fraction of ∼0.40, we observe a sharp, order-of-magnitude decrease in ionic conductivity and enhancement of viscosity, which coincides with the presence of long-lived, nanometer-sized alkyl aggregates. These strong changes in dynamics are not mirrored in the ionicity of these ILs, which decreases nearly linearly with aliphatic volume fraction. Our results demonstrate that nanophase segregation in neat ILs strongly reduces ionic conductivity primarily due to an aggregation-induced suppression of dynamics.

l-Lysine supplementation does not affect the bioavailability of copper or iron in rats.

l-lysine (Lys) is an essential amino acid that is added to foods and dietary supplements. Lys may interact with mineral nutrients and affect their metabolism. This study examined the effect of dietary Lys supplementation on the bioavailability of copper (Cu) and iron (Fe). Weanling male Sprague-Dawley rats were fed one of five diets (20% casein) for 4 weeks containing normal Cu and Fe (control) or low Cu or Fe without (LCu, LFe) or with (LCu+Lys, LFe+Lys) addition of 1.5% Lys. Final body weights, body weight gains and food consumption of the rats did not differ (P≥0.05) among diet groups. Rats fed the low Cu or Fe diets showed changes in nutritional biomarkers compared to control rats, demonstrating reduced Cu and Fe status, respectively. Hematological parameters, serum ceruloplasmin activity and Cu and Fe concentrations in serum, liver, kidney and intestinal mucosa were unaffected (P≥0.05) by Lys supplementation. These results indicate that in the context of an adequate protein diet, Lys supplementation at a relatively high level does not affect Cu or Fe bioavailability in rats.

Temperature-Dependent Suppression of Polymer Diffusion in Polymer Nanocomposites.

The polymer center-of-mass tracer diffusion coefficient in athermal polymer nanocomposites (PNCs) composed of polystyrene and phenyl-capped, spherical silica nanoparticles was measured over a range of temperatures and nanoparticle concentrations using elastic recoil detection. The polymer tracer diffusion coefficient in the PNC relative to the bulk decreases with increasing nanoparticle concentration and is unexpectedly more strongly reduced at higher temperatures. This unusual temperature dependence of polymer diffusion in PNCs cannot be explained by the reptation model or a modified version incorporating an effective tube diameter. Instead we show that our results are consistent with a mechanism based on nanoparticle-imposed configurational entropy barriers.

Influence of the Bound Polymer Layer on Nanoparticle Diffusion in Polymer Melts.

We measure the center-of-mass diffusion of silica nanoparticles (NPs) in entangled poly(2-vinylpyridine) (P2VP) melts using Rutherford backscattering spectrometry. While these NPs are well within the size regime where enhanced, nonhydrodynamic NP transport is theoretically predicted and has been observed experimentally (2RNP/dtube ≈ 3, where 2RNP is the NP diameter and dtube is the tube diameter), we find that the diffusion of these NPs in P2VP is in fact well-described by the hydrodynamic Stokes-Einstein relation. The effective NP diameter 2Reff is significantly larger than 2RNP and strongly dependent on P2VP molecular weight, consistent with the presence of a bound polymer layer on the NP surface with thickness heff ≈ 1.1Rg. Our results show that the bound polymer layer significantly augments the NP hydrodynamic size in polymer melts with attractive polymer-NP interactions and effectively transitions the mechanism of NP diffusion from the nonhydrodynamic to hydrodynamic regime, particularly at high molecular weights where NP transport is expected to be notably enhanced. Furthermore, these results provide the first experimental demonstration that hydrodynamic NP transport in polymer melts requires particles of size ≳5dtube, consistent with recent theoretical predictions.

The Role of Shear Stress in Arteriovenous Fistula Maturation and Failure: A Systematic Review.

INTRODUCTION: Non-maturation and post-maturation venous stenosis are the primary causes of failure within arteriovenous fistulae (AVFs). Although the exact mechanisms triggering failure remain unclear, abnormal hemodynamic profiles are thought to mediate vascular remodelling and can adversely impact on fistula patency. AIM: The review aims to clarify the role of shear stress on outward remodelling during maturation and evaluate the evidence supporting theories related to the localisation and development of intimal hyperplasia within AVFs. METHODS: A systematic review of studies comparing remodelling data with hemodynamic data obtained from computational fluid dynamics of AVFs during and after maturation was conducted. RESULTS: Outward remodelling occurred to reduce or normalise the level of shear stress over time in fistulae with a large radius of curvature (curved) whereas shear stress was found to augment over time in fistulae with a small radius of curvature (straight) coinciding with minimal to no increases in lumen area. Although this review highlighted that there is a growing body of evidence suggesting low and oscillating shear stress may stimulate the initiation and development of intimal medial thickening within AVFs. Further lines of evidence are needed to support the disturbed flow theory and outward remodelling findings before surgical configurations and treatment strategies are optimised to conform to them. This review highlighted that variation between the time of analysis, classification of IH, resolution of simulations, data processing techniques and omission of various shear stress metrics prevented forming pooling of data amongst studies. CONCLUSION: Standardised measurements and data processing techniques are needed to comprehensively evaluate the relationship between shear stress and intimal medial thickening. Advances in image acquisition and flow quantifications coupled with the increasing prevalence of longitudinal studies commencing from fistula creation offer viable techniques and strategies to robustly evaluate the relationship between shear stress and remodelling during maturation and thereafter.