Predictors of clinical success after paroxysmal atrial fibrillation catheter ablation.

INTRODUCTION: Contact force (CF) guided ablation of paroxysmal atrial fibrillation (PAF) with stable catheter-tissue contact optimizes clinical success and may increase an operator's ability to achieve pulmonary vein isolation (PVI) in a single encirclement. First pass PVI reduces procedure time but the relationship with long term clinical success is not well understood. This study evaluated patient characteristics and procedural details as predictors of 1-year clinical success after PAF ablation, including first pass isolation. METHODS: Consecutive de novo PAF ablations were performed with a porous tip CF catheter in 2017 and 2018. All ablations used wide-area circumferential ablation, with first pass isolation captured separately for the left and right pulmonary veins (PVs). CF was held between 10 and 20 g and the catheter was moved every 10-20 s. Radiofrequency energy was set at 40-45 W throughout the atrium. Patient characteristics and procedural details were tested for association with clinical success, defined as freedom from recurrent atrial tachyarrhythmia through 1 year. RESULTS: A total of 404 patients were included in the study. Clinical success at 1 year was 86.6%. Achieving first pass isolation on at least one ipsilateral PV pair was the most significant predictor of clinical success (p = .0126). After controlling for first pass isolation, only recurrence within the 90-day blanking period was independently predictive (p = .0015). First pass isolation was not associated with early recurrence (p = .2454). CONCLUSION: In a real-world setting, first pass isolation was highly predictive of 12-month clinical success after CF-guided ablation in a PAF population.

Impact of Design Changes in Gastrostomy Tube (G-tube) Devices for Patients Who Rely on Home-Based Blenderized Diets for Enteral Nutrition.

OBJECTIVE: Blenderized diets are gaining increasing popularity among enteral tube users. Connectors in gastrostomy tubes (G-tubes) are undergoing standardization to reduce misconnections. These standardized G-tubes are referred to as ENFit G-tubes. This study was performed to quantify the in vitro performance of existing (legacy) G-tubes and compare them with ENFit G-tubes for blenderized diets. METHOD: Patient blenderized diet recipes and practices were obtained through patient advocacy groups. Different blenders and blending times were studied. Five legacy G-tube brands and three corresponding ENFit brands, sized between 14 Fr and 24 Fr, were studied under gravity and push modes of feeding. RESULTS: Considering both thin and thick blenderized gravity mode diets, an average increase in feeding time from 20 minutes to 32 ± 18 minutes in transitioning from legacy to ENFit was observed with standard G-tubes, compared to 22 ± 3.5 minutes for low profiles. For push-mode diets, a 60-second push with standard ENFit G-tubes was easier compared to standard legacy G-tubes (61% ± 21% as much force), but faster 5-second pushes required considerably more effort for ENFit standard G-tubes (167% ± 96%). Low-profile ENFit G-tubes required slightly less effort compared to low-profile legacies for both 60-second and 5-second pushes (72% ± 22% and 90% ± 19%, respectively). Clogging was common in both legacy and ENFit devices, particularly under gravity mode. CONCLUSIONS: For a push mode of feeding, patients will largely be unimpacted after the transition to ENFit. For a gravity mode of feeding, some ENFit users may need higher-powered blenders and should expect increased feeding times.

Communication: Relationship between solute localization and diffusion in a dynamically constrained polymer system.

We investigate the link between dynamic localization, characterized by the Debye-Waller factor, 〈u(2)〉, and solute self-diffusivity, D, in a polymer system using atomistic molecular dynamics simulations and vapor sorption experiments. We find a linear relationship between lnD and 1/〈u(2)〉 over more than four decades of D, encompassing most of the glass formation regime. The observed linearity is consistent with the Langevin dynamics in a periodically varying potential field and may offer a means to rapidly assess diffusion based on the characterization of dynamic localization.

Protein Adsorption on Chemically Modified Block Copolymer Nanodomains: Influence of Charge and Flow.

Understanding the interactions of biomacromolecules with nanoengineered surfaces is vital for assessing material biocompatibility. This study focuses on the dynamics of protein adsorption on nanopatterned block copolymers (BCPs). Poly(styrene)-block-poly(1,2-butadiene) BCPs functionalized with an acid, amine, amide, or captopril moieties were processed to produce nanopatterned films. These films were characterized using water contact angle measurements and atomic force microscopy in air and liquid to determine how the modification process affected. wettability and swelling. Protein adsorption experiments were conducted under static and dynamic conditions via a quartz crystal microbalance with dissipation. Proteins of various size, charge, and stability were investigated to determine whether their physical characteristics affected adsorption. Significantly decreased contact angles were caused by selective swelling of modified BCP domains. The results indicate that nanopatterned chemistry and experimental conditions strongly impact adsorption dynamics. Depending on the structural stability of the protein, polyelectrolyte surfaces significantly increased adsorption over controls. Further analysis suggested that protein stability may correlate with dissipation versus frequency plots.

Comparison between single- and multi-sensor oesophageal temperature probes during atrial fibrillation ablation: thermodynamic characteristics.

AIMS: Oesophageal temperature monitoring with single-sensor probe (SSP) has a variable ability to predict oesophageal ulceration as a consequence of pulmonary vein isolation (PVI). Multi-sensor self-expandable probes (MSPs) may offer improved thermal monitoring. The objective of this study was to compare the thermodynamic characteristics of both probes during PVI. METHODS AND RESULTS: This prospective study enrolled 20 patients undergoing index PVI. Ten patients (group A) underwent dual monitoring with SSP and MSP and 10 control patients (group B) were monitored with SSP alone. Time to initial rise (>0.2°C), time to 1.0°C rise, peak temperature, and decay were recorded with each posterior wall lesion (20 W, 198 applications). The operator was blinded to the MSP temperature data and ablation was only interrupted when SSP temperature increased by ≥2°C. All patients underwent endoscopy within 24 h. Initial temperature increase was detected earlier with MSP (13.4 ± 7.5 vs. 30.5 ± 15.4 s; P < 0.001); led to shorter time to 1.0°C rise (18.5 ± 10.1 vs. 32.1 ± 12.0 s; P < 0.001); and higher change in peak temperature (1.6 ± 2.0 vs. 0.60 ± 0.53°C; P < 0.001). Decay time was similar between the probes (146.1 ± 35.3 vs. 150.4 ± 48.4 s; P = 0.89). The incidence of oesophageal ulceration was similar between the Groups A and B (5 and 4, respectively). Multi-sensor self-expandable probe provided greater sensitivity (100 vs. 60%) and similar specificity (60%) for detection of oesophageal ulceration. Five swine underwent oesophageal mapping before and after MSP placement without alteration in size or position. CONCLUSION: Multi-sensor probes provide a superior thermodynamic profile. Its clinical value in reducing oesophageal injury requires further evaluation.

Prediction and validation of diffusion coefficients in a model drug delivery system using microsecond atomistic molecular dynamics simulation and vapour sorption analysis.

Diffusion of small to medium sized molecules in polymeric medical device materials underlies a broad range of public health concerns related to unintended leaching from or uptake into implantable medical devices. However, obtaining accurate diffusion coefficients for such systems at physiological temperature represents a formidable challenge, both experimentally and computationally. While molecular dynamics simulation has been used to accurately predict the diffusion coefficients, D, of a handful of gases in various polymers, this success has not been extended to molecules larger than gases, e.g., condensable vapours, liquids, and drugs. We present atomistic molecular dynamics simulation predictions of diffusion in a model drug eluting system that represent a dramatic improvement in accuracy compared to previous simulation predictions for comparable systems. We find that, for simulations of insufficient duration, sub-diffusive dynamics can lead to dramatic over-prediction of D. We present useful metrics for monitoring the extent of sub-diffusive dynamics and explore how these metrics correlate to error in D. We also identify a relationship between diffusion and fast dynamics in our system, which may serve as a means to more rapidly predict diffusion in slowly diffusing systems. Our work provides important precedent and essential insights for utilizing atomistic molecular dynamics simulations to predict diffusion coefficients of small to medium sized molecules in condensed soft matter systems.

High-frequency low-tidal volume ventilation improves procedural and long-term clinical outcomes in persistent atrial fibrillation ablation: Prospective multicenter registry.

BACKGROUND: High-frequency, low-tidal volume (HFLTV) ventilation increases the efficacy and efficiency of radiofrequency catheter ablation (RFCA) of paroxysmal atrial fibrillation. Whether those benefits can be extrapolated to RFCA of persistent atrial fibrillation (PeAF) is undetermined. OBJECTIVE: The purpose of this study was to evaluate whether using HFLTV ventilation during RFCA in patients with PeAF is associated with improved procedural and long-term clinical outcomes compared to standard ventilation (SV). METHODS: In this prospective multicenter registry (REAL-AF), patients who had undergone pulmonary vein isolation (PVI) + posterior wall isolation (PWI) for PeAF using either HFLTV ventilation or SV were included. The primary efficacy outcome was freedom from all-atrial arrhythmias at 12 months. Secondary outcomes included procedural and long-term clinical outcomes and complications. RESULTS: A total of 210 patients were included (HFLTV=95 vs. SV=115) in the analysis. There were no differences in baseline characteristics between the groups. Procedural time (80 [66-103.5] minutes vs 110 [85-141] minutes; P <.001), total radiofrequency (RF) time (18.73 [13.93-26.53] minutes vs 26.15 [20.30-35.25] minutes; P <.001), and pulmonary vein RF time (11.35 [8.78-16.69] minutes vs 18 [13.74-24.14] minutes; P <.001) were significantly shorter using HFLTV ventilation compared with SV. Freedom from all-atrial arrhythmias was significantly higher with HFLTV ventilation compared with SV (82.1% vs 68.7%; hazard ratio 0.41; 95% confidence interval [0.21-0.82]; P = .012), indicating a 43% relative risk reduction and a 13.4% absolute risk reduction in all-atrial arrhythmia recurrence. There was no difference in long-term procedure-related complications between the groups (HFLTV 1.1% vs SV 0%, P = .270). CONCLUSION: In patients undergoing RFCA with PVI + PWI for PeAF, the use of HFLTV ventilation was associated with higher freedom from all-atrial arrhythmias at 12-month follow-up, with significantly shorter procedural and RF times compared to SV, while reporting a similar safety profile.

Real-world data of radiofrequency catheter ablation in paroxysmal atrial fibrillation: Short- and long-term clinical outcomes from the prospective multicenter REAL-AF Registry.

BACKGROUND: The safety and long-term efficacy of radiofrequency (RF) catheter ablation (CA) of paroxysmal atrial fibrillation (PAF) has been well established. Contemporary techniques to optimize ablation delivery, reduce fluoroscopy use, and improve clinical outcomes have been developed. OBJECTIVE: The purpose of this study was to assess the contemporary real-world practice approach and short and long-term outcomes of RF CA for PAF through a prospective multicenter registry. METHODS: Using the REAL-AF (Real-world Experience of Catheter Ablation for the Treatment of Symptomatic Paroxysmal and Persistent Atrial Fibrillation; ClincalTrials.gov Identifier: NCT04088071) Registry, patients undergoing RF CA to treat PAF across 42 high-volume institutions and 79 experienced operators were evaluated. The procedures were performed using zero or reduced fluoroscopy, contact force sensing catheters, wide area circumferential ablation, and ablation index as a guide with a target of 380-420 for posterior and 500-550 for anterior lesions. The primary efficacy outcome was freedom from all-atrial arrhythmia recurrence at 12 months. RESULTS: A total of 2470 patients undergoing CA from January 2018 to December 2022 were included. Mean age was 65.2 ±11.14 years, and 44% were female. Most procedures were performed without fluoroscopy (71.5%), with average procedural and total RF times of 95.4 ± 41.7 minutes and 22.1±11.8 minutes, respectively. At 1-year follow-up, freedom from all-atrial arrhythmias was 81.6% with 89.7% of these patients off antiarrhythmic drugs. No significant difference was identified comparing pulmonary vein isolation vs pulmonary vein isolation plus ablation approaches. The complication rate was 1.9%. CONCLUSION: Refinement of RF CA to treat PAF using contemporary tools, standardized protocols, and electrophysiology laboratory workflows resulted in excellent short- and long-term clinical outcomes.

Idiopathic ventricular fibrillation originating from the moderator band.

We report a case of a 59-year-old man with idiopathic ventricular fibrillation storm. Ventricular fibrillation was pause-dependent and triggered by an early-coupled right ventricular premature complex. The characteristic premature beat was mapped and successfully ablated from Purkinje fibers of the moderator band.

Electrocardiogram Belt guidance for left ventricular lead placement and biventricular pacing optimization.

BACKGROUND: Patients with ischemic cardiomyopathy, non-left bundle branch block, or QRS duration <150 ms have a lower response rate to cardiac resynchronization therapy (CRT) than did other indicated patients. The ECG Belt system (EBS) is a novel surface mapping system designed to measure electrical dyssynchrony via the standard deviation of the activation times of the left ventricle. OBJECTIVES: The objectives of this study were to evaluate the efficacy of the EBS in patients less likely to respond to CRT and to determine whether EBS use in lead placement guidance and device programming was superior to standard CRT care. METHODS: This was a prospective randomized trial of patients with heart failure and EBS-guided CRT implantation and programming vs standard CRT care. The primary end point was relative change in left ventricular end-systolic volume from baseline to 6 months postimplantation. RESULTS: A total of 408 patients from centers in Europe and North America were randomized. Although both patients with EBS and control patients had a mean improvement in left ventricular end-systolic volume, there was no significant difference in relative change from baseline (P = .26). While patients with a higher baseline standard deviation of the activation times derived greater left ventricular reverse remodeling, improvement in electrical dyssynchrony did not correlate with the extent of reverse remodeling. CONCLUSION: The findings of the present study do not support EBS-guided therapy for CRT management of heart failure with reduced ejection fraction.

Performance of the REAL-AF Same-Day Discharge Protocol in Patients Undergoing Catheter Ablation of Atrial Fibrillation.

BACKGROUND: Same-day discharge (SDD) after catheter ablation of atrial fibrillation (AF) has been widely adopted. Nevertheless, planned SDD has been performed by using subjective criteria rather than standardized protocols. OBJECTIVES: The goal of this study was to determine the efficacy and safety of the previously described SDD protocol in a prospective multicenter study. METHODS: Using the REAL-AF (Real-world Experience of Catheter Ablation for the Treatment of Paroxysmal and Persistent Atrial Fibrillation) SDD protocol eligibility criteria (stable anticoagulation, no bleeding history, left ventricular ejection fraction >40%, no pulmonary disease, no procedures within 60 days, and body mass index <35 kg/m2), operators prospectively determined whether patients undergoing ablation of AF were candidates for SDD (SDD vs non-SDD groups). Successful SDD was achieved if the patient met the protocol discharge criteria. The primary efficacy endpoint was the success rate of SDD. The primary safety endpoints were readmission rates as well as acute and subacute complications. The secondary endpoints included procedural characteristics and freedom from all-atrial arrhythmias. RESULTS: A total of 2,332 patients were included. The REAL-AF SDD protocol identified 1,982 (85%) patients as potential candidates for SDD. The primary efficacy endpoint was achieved in 1,707 (86.1%) patients. The readmission rate for SDD vs non-SDD group was similar (0.8% vs 0.9%; P = 0.924). The SDD group had a lower acute complication rate than the non-SDD group (0.8% vs 2.9%; P < 0.001), and there was no difference in the subacute complication rate between groups (P = 0.513). Freedom from all-atrial arrhythmias was comparable between groups (P = 0.212). CONCLUSIONS: In this large, multicenter prospective registry, the use of a standardized protocol showed the safety of SDD after catheter ablation of paroxysmal and persistent AF. (Real-world Experience of Catheter Ablation for the Treatment of Paroxysmal and Persistent Atrial Fibrillation [REAL-AF]; NCT04088071).

High-Frequency Low-Tidal Volume Ventilation Improves Long-Term Outcomes in AF Ablation: A Multicenter Prospective Study.

BACKGROUND: High-frequency, low-tidal-volume (HFLTV) ventilation is a safe and simple strategy to improve catheter stability and first-pass isolation during pulmonary vein (PV) isolation. However, the impact of this technique on long-term clinical outcomes has not been determined. OBJECTIVES: This study sought to assess acute and long-term outcomes of HFLTV ventilation compared with standard ventilation (SV) during radiofrequency (RF) ablation of paroxysmal atrial fibrillation (PAF). METHODS: In this prospective multicenter registry (REAL-AF), patients undergoing PAF ablation using either HFLTV or SV were included. The primary outcome was freedom from all-atrial arrhythmia at 12 months. Secondary outcomes included procedural characteristics, AF-related symptoms, and hospitalizations at 12 months. RESULTS: A total of 661 patients were included. Compared with those in the SV group, patients in the HFLTV group had shorter procedural (66 [IQR: 51-88] minutes vs 80 [IQR: 61-110] minutes; P < 0.001), total RF (13.5 [IQR: 10-19] minutes vs 19.9 [IQR: 14.7-26.9] minutes; P < 0.001), and PV RF (11.1 [IQR: 8.8-14] minutes vs 15.3 [IQR: 12.4-20.4] minutes; P < 0.001) times. First-pass PV isolation was higher in the HFLTV group (66.6% vs 63.8%; P = 0.036). At 12 months, 185 of 216 (85.6%) in the HFLTV group were free from all-atrial arrhythmia, compared with 353 of 445 (79.3%) patients in the SV group (P = 0.041). HLTV was associated with a 6.3% absolute reduction in all-atrial arrhythmia recurrence, lower rate of AF-related symptoms (12.5% vs 18.9%; P = 0.046), and hospitalizations (1.4% vs 4.7%; P = 0.043). There was no significant difference in the rate of complications. CONCLUSIONS: HFLTV ventilation during catheter ablation of PAF improved freedom from all-atrial arrhythmia recurrence, AF-related symptoms, and AF-related hospitalizations with shorter procedural times.

Synthesis of research on ENFit gastrostomy tubes with potential implications for US patients using these devices.

Misconnections between enteral devices and other medical devices have been associated with patient death and serious injuries. To minimize such misconnections, the design of connectors on enteral devices has been standardized. The most common adaptation of the standardized enteral connector is called ENFit. Gastrostomy tubes (G-tubes), which may or may not possess the ENFit connector, are increasingly used to deliver commercial and blenderized diets in home settings to enteral device users. To investigate and compare the performance of G-tubes with and without ENFit connectors, research investigations have recently been performed. However, synthesis of such investigations and quantitative discussion of the consequences of transitioning to ENFit-based G-tube devices has not yet occurred. Here we review the research findings from these studies, with data on patient practices from a Mayo Clinic survey, to estimate the impact on tube feeders in home settings of transitioning to ENFit-based G-tube devices. Extrapolating the findings from these studies to US enteral G-tube patients, 1.5%-8.6% of adult patients and 0.2%-1.9% of pediatric patients may experience perceptible slowing in their gravity feeds if using ENFit-based G-tube devices. About 2.5%-8.6% of adult patients and 0.5%-5.5% of pediatric patients (or their caregivers) may need to push with perceptibly more force for syringe push-based feeding using ENFit-based G-tube devices. Lastly, the article offers suggestions for patients and device manufacturers. [Correction added on 2 May 2022, after first online publication: In the preceding sentence, the percentage of adult patients was revised from 2.5%-8.6% to 1.5%-8.6%.].

Designing an Efficient and Quality-focused Integrated Atrial Fibrillation Care Center.

Atrial fibrillation (AF) represents a significant health care burden in the United States that will continue to increase as the population ages; thus, the introduction of cost-effective strategies to limit this burden is critical. The establishment of dedicated electrophysiology programs focusing on AF care within hospitals can improve patient care while providing added financial benefits for institutions if properly planned and delivered. This paper explains how to develop an efficient and quality-focused AF ablation program as part of a larger AF center of excellence by highlighting the experience of a single center and demonstrating how the same principles were adopted to implement a similar program at another institution.

The behavior of iodine in stabilized granular activated carbon and silver mordenite in cementitious waste forms.

Both granular activated carbon (GAC) and silver mordenite (AgM) are utilized for the removal of contaminants and radionuclides (e.g., radioiodine) from off-gas streams in nuclear fuel reprocessing and high temperature immobilization of nuclear waste. Following their service lifetimes, the GAC and AgM contain an inventory of contaminants and radionuclides and require stabilization in a matrix for disposal. GAC and AgM are referred to as solid secondary waste (SSW) materials. Cementitious waste forms can be used as the stabilization matrix for SSW, however, for successful stabilization, the inclusion of GAC and AgM should not negatively impact the physical behavior of the cementitious waste form or increase release of the contaminants/radionuclides compared to the baseline case without stabilization. The present work focuses on evaluation of cement formulations, with and without slag, for the stabilization of iodine-loaded GAC or AgM. The results showed that both a slag-containing and slag-free formulations were able to stabilize GAC and AgM, up to 30 vol%, without deleterious impacts on the bulk physical properties of the encapsulating matrix. When monolithic samples of the GAC or AgM containing cement formulations were subjected to leach tests, it was observed that iodide leached from the SSW) had limited sorption to either of the cement matrices. Nonetheless, the iodine can interact with the SSW materials themselves. Specifically, iodine retention within monolithic samples containing the iodine-loaded GAC or AgM was improved for AgM containing waste forms while no improvement was observed for the GAC containing waste forms. The improvement for the AgM containing waste forms was likely due to an enrichment of Ag at the interface between the AgM particles and the cement matrix that can impede iodine migration out from the waste form. The results are significant in highlighting the potential for long-term retention of iodine in specific cementitious waste forms.

Pearlescent Mica-Doped Alginate as a Stable, Vibrant Medium for Two-Dimensional and Three-Dimensional Art.

Emergent technologies are driving forces in the development of innovative art media that progress the field of modern art. Recently, artists have capitalized on the versatility of a new technology to create, restore, and modify art: additive manufacturing or three-dimensional (3D) printing. Additively manufactured art relies heavily on plastic-based materials, which typically require high heat to induce melting for workability. The necessity for heat limits plastic media to dedicated 3D printers. In contrast, biologically derived polymers such as polysaccharides used to create "bioinks" often do not require heating the material for workability, broadening the types of techniques available for printing. Here, we detail the formulation of a bioink consisting of mica pigments suspended in alginate as a new, vibrant art medium for 2D and 3D compositions. The properties that make alginate an ideal colorant binder are detailed: low cost with wide availability, nontoxicity and biocompatibility, minimal color, and an array of attractive physicochemical properties that offer workability and processing into 2D and 3D structures. Further, the chemical composition, morphology, and dispersibility of an array of mica pigment additives are characterized in detail as they pertain to the quality of an art medium. Alginate-based media with eight mica colors were formulated, where mica addition resulted in vibrantly colored inks with moderate hiding power and coverage of substrates necessary for 2D printing with thin horizontal and vertical lines. The utility of the media is demonstrated via the generation of 2D and 3D vibrant structures.

A prospective multi-site registry of real-world experience of catheter ablation for treatment of symptomatic paroxysmal and persistent atrial fibrillation (Real-AF): design and objectives.

PURPOSE: Catheter ablation has become a mainstay therapy for atrial fibrillation (AF) with rapid innovation over the past decade. Variability in ablation techniques may impact efficiency, safety, and efficacy; and the ideal strategy is unknown. Real-world evidence assessing the impact of procedural variations across multiple operators may provide insight into these questions. The Real-world Experience of Catheter Ablation for the Treatment of Symptomatic Paroxysmal (PAF) and Persistent (PsAF) Atrial Fibrillation registry (Real-AF) is a multicenter prospective registry that will enroll patients at high volume centers, including academic institutions and private practices, with operators performing ablations primarily with low fluoroscopy when possible. The study will also evaluate the contribution of advent in technologies and workflows to real-world clinical outcomes. METHODS: Patients presenting at participating centers are screened for enrollment. Data are collected at the time of procedure, 10-12 weeks, and 12 months post procedure and include patient and detailed procedural characteristics, with short and long-term outcomes. Arrhythmia recurrences are monitored through standard of care practice which includes continuous rhythm monitoring at 6 and 12 months, event monitors as needed for routine care or symptoms suggestive of recurrence, EKG performed at every visit, and interrogation of implanted device or ILR when applicable. RESULTS: Enrollment began in January 2018 with a single site. Additional sites began enrollment in October 2019. Through May 2021, 1,243 patients underwent 1,269 procedures at 13 institutions. Our goal is to enroll 4000 patients. DISCUSSION: Real-AF's multiple data sources and detailed procedural information, emphasis on high volume operators, inclusion of low fluoroscopy operators, and use of rigorous standardized follow-up methodology allow systematic documentation of clinical outcomes associated with changes in ablation workflow and technologies over time. Timely data sharing may enable real-time quality improvements in patient care and delivery. Trial registration Clinicaltrials.gov: NCT04088071 (registration date: September 12, 2019).

Microstructural Assessment of a Multiple-Intermetallic-Strengthened Aluminum Alloy Produced from Gas-Atomized Powder by Hot Extrusion and Friction Extrusion.

An aluminum (Al) matrix with various transition metal (TM) additions is an effective alloying approach for developing high-specific-strength materials for use at elevated temperatures. Conventional fabrication processes such as casting or fusion-related methods are not capable of producing Al-TM alloys in bulk form. Solid phase processing techniques, such as extrusion, have been shown to maintain the microstructure of Al-TM alloys. In this study, extrusions are fabricated from gas-atomized aluminum powders (≈100-400 µm) that contain 12.4 wt % TM additives and an Al-based matrix reinforced by various Al-Fe-Cr-Ti intermetallic compounds (IMCs). Two different extrusion techniques, conventional hot extrusion and friction extrusion, are compared using fabricating rods. During extrusion, the strengthening IMC phases were extensively refined as a result of severe plastic deformation. Furthermore, the quasicrystal approximant IMC phase (70.4 wt % Al, 20.4 wt % Fe, 8.7 wt % Cr, 0.6 wt % Ti) observed in the powder precursor is replaced by new IMC phases such as Al3.2Fe and Al45Cr7-type IMCs. The Al3Ti-type IMC phase is partially dissolved into the Al matrix during extrusion. The combination of linear and rotational shear in the friction extrusion process caused severe deformation in the powders, which allowed for a higher extrusion ratio, eliminated linear voids, and resulted in higher ductility while maintaining strength comparable to that resulting from hot extrusion. Results from equilibrium thermodynamic calculations show that the strengthening IMC phases are stable at elevated temperatures (up to ≈ 600 °C), thus enhancing the high-temperature strength of the extrudates.

Technical considerations for medical device manufacturers when designing gastrostomy tubes (G-tubes) using the new ISO 80369-3 connector.

BACKGROUND: Gastrostomy tubes (G-tubes) are typically used when people cannot eat food by mouth. The connector section that allows G-tubes to connect to other devices, such as feeding sets or syringes, has been modified on some of the devices to reduce misconnections in hospital settings. The narrow internal diameter of the new connector, standardized under ISO 80369-3, has caused some users to express concern about a reduced flow rate. Previous studies performed on commercial devices determined that it was not conclusive how much the ISO 80369-3 connector contributed towards the reduced flow rate, because when manufacturers designed these new connector-based devices, they often changed other geometric variables (such as distal tube diameter, or length) at the same time. Thus, it became difficult isolating the effect of the connector from other geometric variables. METHOD: The key objective of this study was to investigate how different design variables impacted the flow rate through the G-tubes. 3D-printed devices were used to assess the geometric parameters in a systematic manner. Commercial diets and Newtonian analog fluids with matched viscosities were used for testing. RESULTS: The flow path length of the "transition section" encompassing the standardized ISO 80369-3 connector in the new devices was found to cause reduced flow. Additionally, results showed that a shortened (≤ 10 mm) transition section, along with a 10% increase in the distal inner diameter of large bore devices (e.g., 24 Fr), can restore flow rates to levels consistent with the previous devices prior to the connector standardization. CONCLUSIONS: The strategy for restoring flow rates to previous levels may help alleviate concerns raised by multiple stakeholders such as health care professionals, patients, caregivers and device manufacturers. In addition, the approach proposed here can be used as a tool for designing future G-tube devices.

Machine Learning Methods Predict Individual Upper-Limb Motor Impairment Following Therapy in Chronic Stroke.

Background. Accurate prediction of clinical impairment in upper-extremity motor function following therapy in chronic stroke patients is a difficult task for clinicians but is key in prescribing appropriate therapeutic strategies. Machine learning is a highly promising avenue with which to improve prediction accuracy in clinical practice. Objectives. The objective was to evaluate the performance of 5 machine learning methods in predicting postintervention upper-extremity motor impairment in chronic stroke patients using demographic, clinical, neurophysiological, and imaging input variables. Methods. A total of 102 patients (female: 31%, age 61 ± 11 years) were included. The upper-extremity Fugl-Meyer Assessment (UE-FMA) was used to assess motor impairment of the upper limb before and after intervention. Elastic net (EN), support vector machines, artificial neural networks, classification and regression trees, and random forest were used to predict postintervention UE-FMA. The performances of methods were compared using cross-validated R2. Results. EN performed significantly better than other methods in predicting postintervention UE-FMA using demographic and baseline clinical data (median REN2=0.91,RRF2=0.88,RANN2=0.83,RSVM2=0.79,RCART2=0.70;P < .05). Preintervention UE-FMA and the difference in motor threshold (MT) between the affected and unaffected hemispheres were the strongest predictors. The difference in MT had greater importance than the absence or presence of a motor-evoked potential (MEP) in the affected hemisphere. Conclusion. Machine learning methods may enable clinicians to accurately predict a chronic stroke patient's postintervention UE-FMA. Interhemispheric difference in the MT is an important predictor of chronic stroke patients' response to therapy and, therefore, could be included in prospective studies.