A Computational Study of the Electrophysiological Substrate in Patients Suffering From Atrial Fibrillation.

In the context of cardiac electrophysiology, we propose a novel computational approach to highlight and explain the long-debated mechanisms behind atrial fibrillation (AF) and to reliably numerically predict its induction and sustainment. A key role is played, in this respect, by a new way of setting a parametrization of electrophysiological mathematical models based on conduction velocities; these latter are estimated from high-density mapping data, which provide a detailed characterization of patients' electrophysiological substrate during sinus rhythm. We integrate numerically approximated conduction velocities into a mathematical model consisting of a coupled system of partial and ordinary differential equations, formed by the monodomain equation and the Courtemanche-Ramirez-Nattel model. Our new model parametrization is then adopted to predict the formation and self-sustainment of localized reentries characterizing atrial fibrillation, by numerically simulating the onset of ectopic beats from the pulmonary veins. We investigate the paroxysmal and the persistent form of AF starting from electro-anatomical maps of two patients. The model's response to stimulation shows how substrate characteristics play a key role in inducing and sustaining these arrhythmias. Localized reentries are less frequent and less stable in case of paroxysmal AF, while they tend to anchor themselves in areas affected by severe slow conduction in case of persistent AF.

Robotic versus laparoscopic distal pancreatectomy: multicentre analysis.

BACKGROUND: The role of minimally invasive distal pancreatectomy is still unclear, and whether robotic distal pancreatectomy (RDP) offers benefits over laparoscopic distal pancreatectomy (LDP) is unknown because large multicentre studies are lacking. This study compared perioperative outcomes between RDP and LDP. METHODS: A multicentre international propensity score-matched study included patients who underwent RDP or LDP for any indication in 21 European centres from six countries that performed at least 15 distal pancreatectomies annually (January 2011 to June 2019). Propensity score matching was based on preoperative characteristics in a 1 : 1 ratio. The primary outcome was the major morbidity rate (Clavien-Dindo grade IIIa or above). RESULTS: A total of 1551 patients (407 RDP and 1144 LDP) were included in the study. Some 402 patients who had RDP were matched with 402 who underwent LDP. After matching, there was no difference between RDP and LDP groups in rates of major morbidity (14.2 versus 16.5 per cent respectively; P = 0.378), postoperative pancreatic fistula grade B/C (24.6 versus 26.5 per cent; P = 0.543) or 90-day mortality (0.5 versus 1.3 per cent; P = 0.268). RDP was associated with a longer duration of surgery than LDP (median 285 (i.q.r. 225-350) versus 240 (195-300) min respectively; P < 0.001), lower conversion rate (6.7 versus 15.2 per cent; P < 0.001), higher spleen preservation rate (81.4 versus 62.9 per cent; P = 0.001), longer hospital stay (median 8.5 (i.q.r. 7-12) versus 7 (6-10) days; P < 0.001) and lower readmission rate (11.0 versus 18.2 per cent; P = 0.004). CONCLUSION: The major morbidity rate was comparable between RDP and LDP. RDP was associated with improved rates of conversion, spleen preservation and readmission, to the detriment of longer duration of surgery and hospital stay.

Risk of conversion to open surgery during robotic and laparoscopic pancreatoduodenectomy and effect on outcomes: international propensity score-matched comparison study.

BACKGROUND: Minimally invasive pancreatoduodenectomy (MIPD) is increasingly being performed because of perceived patient benefits. Whether conversion of MIPD to open pancreatoduodenectomy worsens outcome, and which risk factors are associated with conversion, is unclear. METHODS: This was a post hoc analysis of a European multicentre retrospective cohort study of patients undergoing MIPD (2012-2017) in ten medium-volume (10-19 MIPDs annually) and four high-volume (at least 20 MIPDs annually) centres. Propensity score matching (1 : 1) was used to compare outcomes of converted and non-converted MIPD procedures. Multivariable logistic regression analysis was performed to identify risk factors for conversion, with results presented as odds ratios (ORs) with 95 per cent confidence intervals (c.i). RESULTS: Overall, 65 of 709 MIPDs were converted (9.2 per cent) and the overall 30-day mortality rate was 3.8 per cent. Risk factors for conversion were tumour size larger than 40 mm (OR 2.7, 95 per cent c.i.1.0 to 6.8; P = 0.041), pancreatobiliary tumours (OR 2.2, 1.0 to 4.8; P = 0.039), age at least 75 years (OR 2.0, 1.0 to 4.1; P = 0.043), and laparoscopic pancreatoduodenectomy (OR 5.2, 2.5 to 10.7; P < 0.001). Medium-volume centres had a higher risk of conversion than high-volume centres (15.2 versus 4.1 per cent, P < 0.001; OR 4.1, 2.3 to 7.4, P < 0.001). After propensity score matching (56 converted MIPDs and 56 completed MIPDs) including risk factors, rates of complications with a Clavien-Dindo grade of III or higher (32 versus 34 per cent; P = 0.841) and 30-day mortality (12 versus 6 per cent; P = 0.274) did not differ between converted and non-converted MIPDs. CONCLUSION: Risk factors for conversion during MIPD include age, large tumour size, tumour location, laparoscopic approach, and surgery in medium-volume centres. Although conversion during MIPD itself was not associated with worse outcomes, the outcome in these patients was poor in general which should be taken into account during patient selection for MIPD.

SUIHTER: a new mathematical model for COVID-19. Application to the analysis of the second epidemic outbreak in Italy.

The COVID-19 epidemic is the latest in a long list of pandemics that have affected humankind in the last century. In this paper, we propose a novel mathematical epidemiological model named SUIHTER from the names of the seven compartments that it comprises: susceptible uninfected individuals (S), undetected (both asymptomatic and symptomatic) infected (U), isolated infected (I), hospitalized (H), threatened (T), extinct (E) and recovered (R). A suitable parameter calibration that is based on the combined use of the least-squares method and the Markov chain Monte Carlo method is proposed with the aim of reproducing the past history of the epidemic in Italy, which surfaced in late February and is still ongoing to date, and of validating SUIHTER in terms of its predicting capabilities. A distinctive feature of the new model is that it allows a one-to-one calibration strategy between the model compartments and the data that are made available daily by the Italian Civil Protection Department. The new model is then applied to the analysis of the Italian epidemic with emphasis on the second outbreak, which emerged in autumn 2020. In particular, we show that the epidemiological model SUIHTER can be suitably used in a predictive manner to perform scenario analysis at a national level.

Purine Metabolism in Platelets and Heart Cells of Hyperlipidemic Rats.

PURPOSE: Hyperlipidemia, characterized by an increase in circulating lipid levels, doubles the chance of developing cardiovascular diseases. It prompts inflammation, immune activation, and oxidative stress in the bloodstream and organs of rats. Thus, we theorized that the metabolism of purines, an immunomodulatory mechanism, is altered in cells involved in the development of cardiovascular diseases. METHODS: Therefore, we induced acute hyperlipidemia in Wistar rats with Poloxamer-407 and euthanized the animals 36 h later. The leucocyte differential, the rate of purine metabolism on the surface of platelets and heart cells, and markers of oxidative stress in the heart tissue were evaluated. These parameters were also assessed in animals pretreated for 30 days with curcumin and/or rutin. RESULTS: Hyperlipidemia increased the hydrolyses of adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP) in platelets. In heart cells, the metabolism of ATP and adenosine (ADO) were increased, while ADP hydrolysis was reduced. Additionally, lipid damage and antioxidant defenses were increased in heart homogenates. Hyperlipidemic rats also exhibited a reduced percentage of eosinophils and lymphocytes. CONCLUSION: Together, these findings are indicative of an increased risk of developing cardiovascular diseases in hyperlipidemic rats. The pretreatments with antioxidants reverted some of the changes prompted by hyperlipidemia preventing detrimental changes in the cells and tissues. Graphical Abstract.

Phase separation in equiatomic AlCoCrFeNi high-entropy alloy.

The microstructure of the as-cast AlCoCrFeNi high entropy alloy has been investigated by transmission electron microscopy and atom probe tomography. The alloy shows a very pronounced microstructure with clearly distinguishable dendrites and interdendrites. In both regions a separation into an Al-Ni rich matrix and Cr-Fe-rich precipitates can be observed. Moreover, fluctuations of single elements within the Cr-Fe rich phase have been singled out by three dimensional atom probe measurements. The results of investigations are discussed in terms of spinodal decomposition of the alloying elements inside the Cr-Fe-rich precipitates.

Detection of human apolipoprotein E genotypes by DNA biosensors coupled with PCR.

Apolipoprotein E (apoE) is an important constituent of several plasma lipoproteins and has been associated with the risk of developing cardiovascular diseases and in familiar type III hyperlipoproteinemia. We developed new procedures for the detection of apolipoprotein E polymorphism in human blood based on coupling DNA electrochemical or piezoelectric sensors with polymerase chain reaction (PCR). The electrochemical sensor was obtained by immobilizing single-stranded oligonucleotides onto graphite screen-printed electrodes by adsorption at controlled potential. The hybridization reaction that occurred on the electrode surface was evidenced by chronopotentiometric stripping analysis-using daunomycin as indicator. In the piezoelectric sensor, biotinylated 23-mer probes were immobilized on the streptavidin-coated gold surface of a quartz crystal; streptavidin was covalently bound to the thiol/dextran modified gold surface. The hybridization of the immobilized probes with complementary and mismatched DNA was investigated. With the use of two different probes, it was possible to investigate both positions in which apoE polymorphism takes place and consequently, to distinguish the different genotypes. The procedure was validated with both kinds of biosensor with a reference method based on polyacrilamide gel electrophoresis.

Enzyme electrode for glucose determination in whole blood.

The development of a glucose sensor suitable for use with whole blood is described. It is based on anodic oxidation at +700 mV of hydrogen peroxide with a platinum electrode covered with a gas permeable membrane. Glucose reacts with glucose oxidase immobilised on the external side of the membrane, and forms hydrogen peroxide which is able to cross the gas permeable membrane due to its high vapour tension, while other electroactive substances that are important interferents are completely blocked. This principle was discovered several years ago but no practical application was presented up to now. Therefore in this work a number of different commercial membranes were tested, in order to obtain a resistant, rapidly responding and interference free sensor to be used in conjunction with a blood gas measurement apparatus. Coimmobilisation of glucose oxidase and catalase was found to be useful for fast response and recovery of the electrode. Using some of the tested membranes, the linearity range is 1-15 mM, CV 5%, response time 90 s, recovery time for the next sample 120 s. The membrane's working life is 2-3 weeks.

Ion effects in measurement of sodium and ionized calcium in direct potentiometry.

In some instruments that measure sodium directly in whole blood, plasma, or serum using ion selective electrodes (direct potentiometry), the higher the ionic strength of the solution, the lower is the sodium recovery in serum, as predicted by theory. The same could be expected for ionized calcium. When measuring the recovery of serum sodium on indirect potentiometric instrument and by flame photometry, which determine concentration in prediluted samples, and on direct potentiometric instruments, we observed that two out of the three direct potentiometry instruments showed a decreased recovery of sodium, as the ionic strength was increased, while on all the other instruments the recovery was complete. No effect of increased ionic strength was noted on the ionized calcium measurements in serum on all the instruments tested. Analysing pure aqueous solutions of sodium and calcium chloride with increased ionic strength on the same instruments, the sodium recovery was always complete or positive, and the same was true for ionized calcium. We postulate some effect of ionic strength on the salt bridge of the measuring systems, which is different when analysing serum or pure aqueous solutions.

Incomplete recovery of sodium determined in direct potentiometry in blood samples added with heparin salts.

The recent introduction on the market of apparatus for combined blood gas-electrolyte and ionized calcium analyses has raised the problem of whether the same sample can be submitted to all the analyses without generating problems for some analytes. The problem is basically connected to the common use of heparin as an anti-coagulant. To elucidate the possible effect of heparin on measurements we added pooled sera to tubes containing dried heparin/sodium chloride in increasing quantity. Our data demonstrate that, for one direct potentiometric instrument, the sodium recovery is reduced by a moderately high (70-130 IU ml-1) concentration of heparin or by the concomitant addition of the sodium ion which increases the ionic strength of the sample. The effect of the increased sodium chloride was studied separately, adding pooled sera to tubes containing dried sodium chloride in increasing quantity. The sodium recovery was reduced when the ionic strength of the sample was increased. We were unable to separate the negative effects on the sodium recovery due to heparin and due to the increased ionic strength in the sample.

A survey of helminth parasites in backyard flocks in Michigan by litter examination.

The prevalence of parasitic infections in backyard flocks was surveyed using litter samples from 74 pens located on 12 farms in central lower Michigan. Eight species of birds were represented. Two methods of litter examination (a sucrose flotation technique and a multiple washing/ZnCl2 flotation) were compared; the sucrose flotation technique was found to be more useful and was used in the survey. The following parasites eggs/oocysts were observed; ascarid-type eggs (in 34 pens from nine farms), Capillaria eggs (in 30 pens from nine farms), Strongyloides eggs (in nine pens from five farms), Syngamus eggs (in five pens from four farms), and coccidial oocysts (in 40 pens from 10 farms). Contamination of litter with ascarid-type eggs, Capillaria eggs, and coccidial oocysts was commonly found, irrespective of bird species. The contamination level in pens with more than one bird species was lower than in pens with a single species. The relatively high contamination rate may be an indication of the risk of parasitic disease in birds that are not raised under controlled conditions in confinement.