Mechanisms of organized atrial tachycardia during catheter ablation of chronic atrial fibrillation by stepwise approach

Background Extensive atrial fibrillation （AF） ablation is associated with an increased success rate of catheter ablation in chronic AF patients and an increased rate of atrial tachycardia （AT） during the procedure. The mechanism of these Ats varies in previous studies. Our study aimed to report the mechanism of organized AT occurring during the stepwise ablation procedure of chronic AF.Methods A prospective cohort of 86 consecutive patients who underwent an ablation procedure for chronic atrial fibrillation （CAF） was investigated. The stepwise procedure was performed in the following order： circumferential pulmonary vein ablation, complex fractionated atrial electrograms ablation, mapping and ablation of AT. The endpoint was noninducibility of AF/AT after sinus rhythm （SR） was restored or the procedure time was beyond 6 hours.Results Sixty-nine （80%） of patients converted to SR via AT. A total of 179 sustained ATs were observed in 69 patients during the procedure. There were 81% （n=145） macroreentrant ATs which included 65 perimitral circuits, 48 peritricuspid tachycardia and 32 roof dependent circuits, 12% （n=21） localized reentrant and 7% （n=13） focal ATs. Thirty （15%） patients experienced significant left atrium （LA） and LA appendage （LAA） conduction delay or dissociation in the procedure or during the follow-up period.Conclusions Most CAF patients converted to SR via ablation of organized AT occurring during the stepwise procedure. The mechanism of most of these ATs was macro-reentry.

Revealing the surface atomic arrangement of noble metal alkane dehydrogenation catalysts by a stepwise reduction-oxidation approach

Surface characterization of metal nanoparticles is a critical need in nanocatalysis for in-depth understanding of the structure-function relationships.The surface structure of nanoparticles is often different from the subsurface,and it is challenging to separately characterize the surface and the subsurface.In this work,theoretical calculations and extended X-ray absorption fine structure(EXAFS)analysis illustrate that the surface atoms of noble metals(Pt and Pd)are oxidized in the air,while the subsurface atoms are not easily oxidized.Taking advantage of the oxidation properties,we suggest a stepwise reduction-oxidation approach to determine the surface atomic arrangement of noble metal nanoparticles,and confirm the rationality of this approach by identifying the surface structure of typical 2-3 nm Pt and Pd nanoparticles.The reduction-oxidation approach is applied to characterize the surface structure of model Pd-Sb bimetallic catalyst,which illustrates that the surface Pd is well isolated by Sb atoms with short bond distance at 2.70Å,while there are still Pd-Pd bonds in the subsurface.Density functional theory(DFT)calculations and Pd L edge X-ray absorption near edge structure(XANES)indicate that the isolation of surface Pd significantly decreases the adsorption energies of Pd-hydrocarbon,which leads to the high propylene selectivity and turnover frequency Pd-Sb bimetallic catalyst for propane dehydrogenation.

Selecting and applying quantification models for ecosystem services to forest ecosystems in South Korea

There is growing interest in using ecosystem services to aid development of management strategies that target sustainability and enhance ecosystem support to humans. Challenges remain in the search for methods and indicators that can quantify ecosystem services using metrics that are meaningful in light of their high priorities. We developed a framework to link ecosystems to human wellbeing based on a stepwise approach. We evaluated prospective models in terms of their capacity to quantify national ecosystem services of forests. The most applicable models were subsequently used to quantify ecosystem services. The Korea Forest Research Institute model sat- isfied all criteria in its first practical use. A total of 12 key ecosystem services were identified. For our case study, we quantified four ecosystem functions, viz. water storage capacity in forest soil for water storage service, reduced suspended sediment for water purification service, reduced soil erosion for landslide prevention service, and reduced sediment yield for sediment regulation service. Water storage capacity in forest soil was estimated at 2142 t/ha, and reduced suspended sediment was estimated at 608 kg/ ha. Reduced soil erosion was estimated at 77 m^3/ha, and reduced sediment yield was estimated at 285 m^3/ha. These results were similar to those reported by previous studies. Mapped results revealed hotspots of ecosystem services around protected areas that were particularly rich in bio- diversity. In addition, the proposed framework illustrated that quantification of ecosystem services could be sup- ported by the spatial flow of ecosystem services. However, our approach did not address challenges faced when quantifying connections between ecosystem indicators and actual benefits of services described.

Pain in chronic pancreatitis:What can we do today?

The aim of this study is to illustrate the complexity of pain management in chronic pancreatitis(CP).In this context,pain represents the most common and debilitating symptom,and it deeply affects patient’s quality of life.Multiple rating scales(unidimensional,bidimensional and multidimensional)have been proposed to quantify CP pain.However,it represents the result of complex mechanisms,involving genetic,neuropathic and neurogenic factors.Considering all these aspects,the treatment should be discussed in a multidisciplinary setting and it should be approached in a stepwise manner.First,a lifestyle change is recommended and nonsteroidal anti-inflammatory drugs represent the gold standard among medical treatments for CP patients.The second step,after medical approach,is endoscopic therapy,especially for complicated CP.In case of failure,tailored surgery represents the third step and decompressive or resection procedures can be chosen.In conclusion,CP pain’s management is challenging considering all these complex aspects and the lack of international protocols.

Workup of difficult-to-treat asthma:implications from treatable

Traditional stepwise approach usually adjusts the treatment regimen based on changes in asthma symptoms and severity to achieve good asthma control.However,due to the generalized heterogeneity and complexity of asthma,its therapeutic efficacy in difficultto-treat asthma is limited.Recently,a precision medicine approach based on the identification and intervention of treatable traits of chronic airway disease has been proposed and appears to be of greater benefit to asthmatics.We reported a 71-year-old male with uncontrolled asthma and multiple exacerbations over the past year.He complained of persistent dyspnea despite high-dose of inhaled corticosteroids plus other controllers.Does this patient have some potential treatable traits contributing to difficult-to-treat asthma?Through a multidimensional assessment of three domains including pulmonary,extrapulmonary,and behavioral/risk factors,15 treatable traits were identified in the patient,mainly including airflow limitation,eosinophilic airway inflammation,small airway dysfunction,exacerbation prone,dilated cardiomyopathy,diabetes mellitus,inhaler device polypharmacy,smoking,and the absence of an asthma action plan.After targeted treatment for these treatable traits,the patient experienced significant improvement in dyspnea and he could maintain good asthma control with low-dose inhaled corticosteroids and long-acting β_(2)-agonist.This study shows that,in response to the limitation of a stepwise approach to therapy,treatable traits is a new strategy where patients are individually assessed for a specified set of treatable problems,and an individualized treatment program is developed and implemented based on this multidimensional assessment,especially for difficult-to-treat asthma.