The Initial Molecular Interactions in the Course of Enthalpy Relaxation and Nucleation in Polyethylene Terephthalate (PET) as Monitored by Combined Nanocalorimetry and FTIR Spectroscopy

Fast scanning calorimetry (FSC) and Fourier transform infrared (FTIR) spectroscopy are combined to trace  the evolution of the calorimetric properties and of the molecular interactions in a strongly crystallizing polymer, polyethylene terephthalate (PET). The minute sample amount (≈5 ng) required for FSC allows for the realization of cooling rates up to 50 000 K s⁻¹ and to quench the sample into the amorphous state. By subsequent annealing at varying temperatures T_a and times t_a enthalpy relaxation, (homogeneous) nucleation and crystallization can be monitored with high precision. Determining the difference IR spectra between a quenched and an annealed sample unravels the development of the intra- and inter-molecular interactions in detail; i) as first response taking place during enthalpy relaxation, the far reaching Coulomb interactions between the polar carbonyl (C ═ O) moieties are active; ii) in contrast, the methylene unit (CH₂) and the aromatic ring show a response only, if homogeneous nucleation sets in, while the ester (COC) moiety remains uninfluenced; iii) a hierarchy is observed in of the response of the different molecular moieties; iv) if crystallization comes to play, all molecular units are involved. The results are compared with recently published findings for polyamide 66 demonstrating the high molecular specificity of homogeneous nucleation and crystallization.     

Atrial fibrillation: Epidemiology,pathophysiology, and clinical complications (literature review)

The last three decades have been characterized by an exponential increase in knowledge and advances in the clinical management of atrial fibrillation. The purpose of the study is to provide an overview of the pathogenesis of nonvalvular atrial fibrillation and a comprehensive investigation of the epidemiological data associated with various risk factors for atrial fibrillation. The leading research methods are analysis and synthesis, comparison, observation, induction and deduction, and grouping method. Research has shown that old age, male gender, and European descent are important risk factors for developing atrial fibrillation. Other modifiable risk factors include a sedentary lifestyle, smoking, obesity, diabetes mellitus, obstructive sleep apnea, and high blood pressure predisposing to atrial fibrillation, and each has been shown to induce structural and electrical atrial remodeling. Both heart failure and myocardial infarction increase the risk of developing atrial fibrillation and vice versa creating feedback that increases mortality. The review is a comprehensive study of the epidemiological data linking nonmodifiable and modifiable risk factors for atrial fibrillation, and the pathophysiological data supporting the relationship between each risk factor and the occurrence of atrial fibrillation. This may be necessary for the practice of the treatment of the cardiac system.     

Sex-related differences in outcome after left atrial appendage occlusion: Insights from Europe and the EWOLUTION registry

Background

Women with atrial fibrillation (AF) generally experience worse symptoms, poorer quality of life, and have a higher risk of stroke and death. There is limited availability of sex-related differences regarding left atrial appendage occlusion (LAAO).

Aims

The aim of this study was to evaluate the sex-related differences in patients undergoing LAAO in EWOLUTION.

Methods

A total of 1025 patients scheduled for elective LAAO therapy employing the WATCHMAN Gen 2.5 prospectively consented for participation; 1005 patients received a successful implant and were followed for 2 years. As we detected sex-related differences in baseline data we performed a propensity score matching. The primary endpoint is a combined endpoint of survival free from mortality, major bleeding, ischemic stroke, transitory ischemic attack (TIA) and systemic embolization (SE) up to 2-year clinical follow-up. Secondary Endpoints were periprocedural data and overall 2-year survival.

Results

Women were older but had less often vascular disease and hemorrhagic stroke. There was no sex-related significant difference after LAAO at 2 years in the combined endpoint of survival free from mortality, major bleeding, ischemic stroke, TIA, and SE (female vs. male: 79% vs.76%, p = 0.24) or in overall survival (female vs. male: 85% vs. 82%, p = 0.16). Procedural data showed a higher sealing rate after the implantation in women (complete sealing female 94% vs. male 90%, p = 0.033), significantly more pericardial effusions (female 1.2% vs. male 0.2%, p = 0.031) and a similar periprocedural risk profile.

Conclusions

Females undergoing LAAO differ in various baseline variables, but after adjustment, we observed similar safety and efficacy of LAAO with no significant difference in long-term outcomes between women and men.     

Transfusion of red blood cells in venoarterial extracorporeal membrane oxygenation: A multicenter retrospective observational cohort study

Background

Evidence-based recommendations for transfusion in patients with venoarterial extracorporeal membrane oxygenation (VA ECMO) are scarce. The current literature is limited to single-center studies with small sample sizes, therefore complicating generalizability. This study aims to create an overview of red blood cell (RBC) transfusion in VA ECMO patients.

Methods

This international mixed-method study combined a survey with a retrospective observational study in 16 centers. The survey inventoried local transfusion guidelines. Additionally, retrospective data of all adult patients with a VA ECMO run >24 h (January 2018 until July 2019) was collected of patient, ECMO, outcome, and daily transfusion parameters. All patients that received VA ECMO for primary cardiac support were included, including surgical (i.e., post-cardiotomy) and non-surgical (i.e., myocardial infarction) indications. The primary outcome was the number of RBC transfusions per day and in total. Univariable logistic regressions and a generalized linear mixed model (GLMM) were performed to assess factors associated with RBC transfusion.

Results

Out of 419 patients, 374 (89%) received one or more RBC transfusions. During a median ECMO run of 5 days (1st–3rd quartile 3–8), patients received a median total of eight RBC units (1st–3rd quartile 3–17). A lower hemoglobin (Hb) prior to ECMO, longer ECMO-run duration, and hemorrhage were associated with RBC transfusion. After correcting for duration and hemorrhage using a GLMM, a different transfusion trend was found among the regimens. No unadjusted differences were found in overall survival between either transfusion status or the different regimens, which remained after adjustment for potential confounders.

Conclusion

RBC transfusion in patients on VA ECMO is very common. The sum of RBC transfusions increases rapidly after ECMO initiation, and is dependent on the Hb threshold applied. This study supports the rationale for prospective studies focusing on indications and thresholds for RBC transfusion.     

Reversible Assembly of Conductive Supragel Building Blocks by Metallo-Complexes

The design of multicomponent, building block-based assemblies of polymer materials has gained tremendous interest due to the ability to combine functional variety and materials inside one integrated object. One such type of building blocks are polymer hydrogels that assemble into so-called supragels. For that, it is necessary to implement reliable intra- and innerparticle cross-linking methods that ensure mechanical stability and the supragels' adaptiveness over its life cycle, e.g., via selective assembly and disassembly. Here, a facile method for reversible interparticle cross-linking of vinylimidazole-based polymer hydrogel particles is presented. The method is based on supramolecular cross-linking via transition metal complexation. Supragels consisting of four to 27 individual 3 × 3 × 3 mm particles are successfully obtained. By swelling the preassembled hydrogels inside aqueous solutions of Zn²⁺, Cu²⁺, and Fe²⁺ ions, stable interparticle linkage is achieved within 15 min. These supragels resist mechanical forces, but can be quantitatively disassembled into their corresponding building blocks by simple ligand exchange with ethylenediaminetetraacetic acid (EDTA). With this method, it is possible to quickly build hydrogel macrostructures of any shape and complexity, which exemplarily also exhibit electrical conductivity due to the introduction of metal ions for cross-linking.