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Background: Multidetector computed tomography (MDCT) is the gold standard in annulus sizing before transcatheter aortic valve replacement (TAVR). However, MDCT has limited applicability in specific subgroups of patients, such as those with atrial fibrillation and chronic kidney disease. Two-dimensional transesophageal echocardiography (2DTEE) has traditionally been limited to the long-axis measurement of the anteroposterior diameter of the aortic annulus. We describe a new 2DTEE approach for the measurement of the major diameter of the aortic annulus. Methods: Seventy-six patients with symptomatic severe aortic valve stenosis and high surgical risk underwent MDCT and 2DTEE before TAVR. A modified five-chamber view was used to measure the major aortic annulus diameter. This was obtained starting from a mid-esophageal four chamber and retracting the TEE probe up until the left ventricular outflow tract and the left and noncoronary aortic cusps were visualized: major aortic annulus diameter was measured as the distance between their insertion points in systole. Results: Major aortic annulus diameters measured at 2DTEE showed good correlation with MDCT diameter (r = 0.79; P < 0.001) and perimeter (r = 0.87; P < 0.0001). Using factsheet-derived sizing criteria, 2DTEE alone would have allowed accurate sizing in 75% of patients, with 21% of oversizing predominantly with smaller annuli. Conclusions: We describe a new method for 2DTEE measurement of the major aortic annulus diameter; this approach is simple, correlates with MDCT, and allows adequate TAVR sizing in most patients. These findings may help in the assessment of patients with contraindications to or inadequate MDCT images.

Catheter-based or surgical procedures in patients with long-standing persistent atrial fibrillation (LSPAF) remain a challenge. As a result, different approaches including hybrid (surgical and endocardial) ablation have been developed. Bachmann’s bundle (BB) is a mainly epicardial structure capable of sustaining arrhythmic reentry that could be involved in the development and perpetuation of atrial fibrillation. We investigated the efficacy and safety of an adjunctive BB ablation in LSPAF patients undergoing hybrid ablation. In a two-arm non-randomized study, consecutive LSPAF patients undergoing epicardial isolation of pulmonary veins with left atrial posterior wall (box lesion) with (n = 30, BB group) and without additional BB ablation (n = 30, CONV group) were enrolled in the study. All patients underwent an endocardial procedure within 6 weeks post-surgery to assess for potential lesion gaps and additional atrial substrate modification. The primary endpoint was freedom from AF through 12 months of follow-up. The two-staged hybrid ablation was successfully completed in all patients. One-year freedom from atrial arrhythmias recurrence rates was 96.6% in the BB group vs 76.6% in the CONV group (p = 0.025). At procedure completion, 30 (100%) and 17 (56%) patients had a spontaneous cardioversion in BB and CONV group, respectively (p < 0.001). No significant differences in quality of life or complication rates were observed. This initial experience shows, for the first time, that adjunctive BB ablation in the setting of hybrid ablation for LSPAF is a feasible and effective approach in increasing maintenance of sinus rhythm without increasing complication rates.

Objective In nonvalvular atrial fibrillation (AF) patients at high bleeding risk, oral anticoagulants (OAC) may be contraindicated, and percutaneous left atrial appendage (LAA) closure has been advocated. However, following percutaneous procedure, either OAC or dual antiplatelet treatment is required. In this study, we present our experience in treating nonvalvular AF patients at high bleeding risk with thoracoscopic LAA closure with no subsequent antithrombotic therapy. Methods From April 2019 to January 2020, 20 consecutive AF patients, mean age 75.1 years, 16 (80%) males, underwent thoracoscopic LAA closure as a stand-alone procedure, using an epicardial clip device. OAC and antiplatelet therapy were contraindicated. Mean CHA2DS2-VASc score was 3.61, and the mean HAS-BLED score was 4.42. Successful LAA closure was assessed by transesophageal echocardiography. Primary endpoints were complete LAA closure (no residual LAA flow), operative complications, and all-cause mortality; secondary endpoints were 30-day and 6-month complications (death, ischemic stroke, hemorrhagic stroke, transient ischemic attack, any bleeding). Mean follow-up was 6 ± 4 months. Results Complete LAA closure was achieved in all patients. No operative clip-related complications or deaths occurred. At follow-up, freedom from postoperative complications was 95% and from any cerebrovascular events was 100%. Overall survival rate was 100%. Conclusions In nonvalvular AF patients at high bleeding risk (HAS-BLED score >3), thoracoscopic LAA closure appears to be a valid alternative to percutaneous techniques not requiring dual antiplatelet or OAC treatment. Apparently, external LAA clipping minimizes the risk of thromboembolic events as compared with percutaneous procedures.

Introduction. Catheter-based or surgical procedures in patients with long-standing persistent atrial fibrillation (LSPAF) remain a challenge. As a result, different approaches including hybrid (surgical and endocardial) ablation have been developed. Bachmann’s bundle (BB) is a mainly epicardial structure capable of sustaining arrhythmic reentry that could be involved in the development and perpetuation of atrial fibrillation. We investigated the efficacy and safety of an adjunctive BB ablation in LSPAF patients undergoing hybrid ablation. Methods. In a two arm non randomized study, consecutive LSPAF patients undergoing epicardial isolation of pulmonary veins with left atrial posterior wall (box-lesion) with (n=30, BB-group) and without additional BB ablation (n=30, CONV-group) were enrolled in the study. All patients underwent an endocardial procedure within 6 weeks post-surgery to assess for potential lesion gaps and additional atrial substrate modification. The primary endpoint was freedom from AF through 12 months of follow-up. Results. The two-staged hybrid ablation was successfully completed in all patients. One-year freedom from atrial arrhythmias recurrence rates was 96.6% in the BB group vs 76.6% in the CONV group (p=0.025). At procedure completion, 30 (100%) and 17 (56%) patients had a spontaneous cardioversion in BB and CONV group respectively (p < 0.001). No significant differences in quality of life or complication rates were observed. Conclusions. This initial experience shows, for the first time, that adjunctive BB ablation in the setting of hybrid ablation for LSPAF is a feasible and effective approach in increasing maintenance of sinus rhythm without increasing complication rates.

Surgical treatment of atrial fibrillation generally consists in the isolation of the pulmonary veins ("box-lesion"). Bachmann's bundle is a cardiac structure that may play an important role in the genesis of the atrial fibrillation. Surgical isolation of such bundle has not been reported before. We aim to describe how to perform minimally invasive epicardial pulmonary vein isolation along with the isolation of the Bachmann's bundle. Adding the surgical ablation line of Bachmann's bundle is a feasible, fast, and easy procedure that may be contribute to the reduction of atrial fibrillation relapses.

Silicon carbide (SiC) power MOSFETs are available only for high-power and medium-to-high-voltage applications, generally above 600 V, because for lower blocking voltages, they comparatively provide lower advantages in terms of efficiency. There are applications, however, for which ruggedness and reliability are as important as efficiency, such as power optimizers for photovoltaic (PV) modules, which fall within the low power, low voltage category of dc–dc converters. These circuits, which maximize the energy produced by each single PV module, operate in continuously changing and stressing conditions yet having to assure high performances in terms of efficiency as well as of temperature insensitivity and long-term reliability. The aim of this paper is to predict the basic characteristics of a 4H-SiC MOSFET tailored for this kind of applications and, therefore, characterized by a breakdown voltage BVDS of 150 V and currents of the order of 10 A. The study, based on numerical simulations, shows that, besides the expected higher ruggedness, the static characteristics would be comparable to those of silicon MOSFETs rated for a comparable BVDS, with $R_{\mathrm{\scriptscriptstyle ON}}$ in the order of 100 $\text{k}\Omega {\cdot} \mu \text{m}^{2}$ , while advantages would result in terms of dynamic characteristics, and in particular in terms of switching times.

The role of a non-uniform p-base doping concentration in determining the electrical characteristics of a metal oxide semiconductor field effect transistor (MOSFET) in 4H-SiC is investigated. In particular, the device is dimensioned for low voltage ratings and its on-resistance (Ron) behavior is analyzed by means of numerical simulations. The results reveal that the proposed MOSFET shows in forward bias a high drain current, a low threshold voltage, and a low Ron if compared with previous literature data on similar device structures. This study would help in obtaining an improved performance for a low breakdown voltage 4H-SiC MOSFET which could turn useful, for example, as power optimizer in photovoltaic module-level applications.

A numerical simulation study accounting for trap and defect effects on the current-voltage characteristics of a 4H-SiC-based power metal-oxide-semiconductor field effect transistor (MOSFET) is performed in a wide range of temperatures and bias conditions. In particular, the most penalizing native defects in the starting substrate (i.e., EH6/7 and Z1/2) as well as the fixed oxide trap concentration and the density of states (DoS) at the 4H-SiC/SiO2 interface are carefully taken into account. The temperature-dependent physics of the interface traps are considered in detail. Scattering phenomena related to the joint contribution of defects and traps shift the MOSFET threshold voltage, reduce the channel mobility, and penalize the device current capabilities. However, while the MOSFET on-state resistance (RON) tends to increase with scattering centers, the sensitivity of the drain current to the temperature decreases especially when the device is operating at a high gate voltage (VGS). Assuming the temperature ranges from 300 K to 573 K, RON is about 2.5 MΩ·µm2 for VGS &gt, 16 V with a percentage variation ΔRON lower than 20%. The device is rated to perform a blocking voltage of 650 V.

We construct a news spreading model with a time dependent contact rate which generalizes the classical Susceptible–Infected model of epidemiology. In particular, we are interested on the time-dynamics of the sharing and diffusion process of news on the Internet. We focus on the counting process describing the number of connections to a given website, characterizing the cumulative density function of its inter-arrival times. Moreover, starting from the general form of the finite dimensional distribution of the process, we determine a formula for the time-variable rate of the connections and establish its relationship with the probability density function of the interarrival times. We finally show the effectiveness of our theoretical framework analyzing a real-world dataset, the Memetracker dataset, whose parameters characterizing the diffusion process are determined.

Selenium is a trace element, nutritionally classified as an essential micronutrient, involved in maintaining the correct function of several enzymes incorporating the selenocysteine residue, namely the selenoproteins. The human selenoproteome including 25 proteins is extensively described here. The most relevant selenoproteins, including glutathione peroxidases, thioredoxin reductases and iodothyronine deiodinases are required for the proper cellular redox homeostasis as well as for the correct thyroid function, thus preventing oxidative stress and related diseases. This review summarizes the main advances on oxidative stress with a focus on selenium metabolism and transport. Moreover, thyroid-related disorders are discussed, considering that the thyroid gland contains the highest selenium amount per gram of tissue, also for future possible therapeutic implication.

The paper is concerned with the analysis of the error associated to a family of multi-value numerical methods for the solution of initial value problems based on special second order ordinary differential equations. Such methods, denoted as General Nystrom methods, provide at each step point an approximation to the Nordsieck vector associated to the solution of the problem. Order issues for such methods based on the theory of rooted trees are here provided, as well as an accuracy analysis is carried out, leading to a representation of the local truncation error.

Contact with cardiac tissue is an important determinant of lesion efficacy during atrial fibrillation (AF) ablation. The Sensei X™ robotic navigation system (RNS) (Hansen Medical, Mountain View, CA, USA) has been validated for contact force (CF) sensing expressed in grams (g). The Thermocool® SmartTouch™ catheter enables the measurement of catheter tip CF and direction inside the heart. We aimed to investigate the catheter CF with and without RNS during pulmonary vein isolation (PVI) procedures.Eighty patients with symptomatic AF (56 males, age 63 ± 18) were enrolled in this study. Fifty-seven patients had paroxysmal AF and 23 early persistent AF. All procedures were performed with the Thermocool® SmartTouch™ ablation catheter. Forty patients were randomized to perform PVI with the Sensei X™ RNS (group 1), while in the other 40 patients (group 2), PVI was performed without the RNS.AF ablation was performed successfully in all patients without complications, while contact force was kept in the established 10-40 g range. A significantly higher CF was documented on the PVs in group 1 compared to group 2. The 1-year freedom from AF recurrence was higher in group 1 compared to group 2 (90 vs. 65 %, p = 0.04). Moreover, a significant reduction of fluoroscopy time was noted in the RNS group (13 ± 10 vs. 20 ± 10 min, respectively, p = 0.05).The Sensei X™ RNS permits a significantly higher CF during transcatheter AF ablation with a low rate of AF recurrence at clinical follow-up.

Previous studies reported the usefulness of an irrigated circular radiofrequency ablation catheter (nMARQ(TM), Biosense Webster) for pulmonary vein isolation (PVI). We evaluated the role of intracardiac echocardiography (ICE) to optimize the manipulation of nMARQ(TM) catheter.Thirty-seven patients (pts), (mean age 55 ± 12 years; 28 males) were enrolled to perform PVI. All pts underwent PVI with the nMARQ(TM) catheter. In 20 pts (group 1), we utilized ICE to guide nMARQ(TM) catheter positioning at the PV ostia; in the other 17 pts (group 2), nMARQ(TM) catheter was positioned at the PV ostia guided by fluoroscopy and TissueConnect(TM) technology.Radiofrequency (RF) applications were significantly lower in group 1 compared to group 2 [left PVs: 6 (range 3 to 12) in group 1 and 12 (range 5 to 16) in group 2 (p0.001); right PVs: 7 (range 4 to 14) in group 1 and 10 (range 5 to 16) in group 2 (p = 0.04)]; similarly regarding the time of RF delivery [left PVs: 318 ± 194 s in group 1 vs. 542 ± 104 s in group 2 (p0.001); right PVs: 410 ± 270 s in group 1 vs. 550 ± 156 s in group 2 (p = 0.05)]. Fluoroscopy time (23 ± 9 min vs. 28 ± 5 min; p = 0.05), procedural time (83 ± 23 min vs. 160 ± 42 min; p0.001), and radiation dose (109 ± 20 Gy/cm(2) vs. 127 ± 29 Gy/cm(2); p = 0.04) were significantly lower in group 1 compared to group 2.ICE might be a useful tool to guide nMARQ(TM) catheter position in the left atrium during atrial fibrillation (AF) ablation procedures.

This paper is concerned with the numerical solution of Hamiltonian problems, by means of nearly conservative multivalue numerical methods. In particular, the method we propose is symmetric, G-symplectic, diagonally implicit and generates bounded parasitic components over suitable time intervals. Numerical experiments on a selection of separable Hamiltonian problems are reported, also based on real data provided by Nasa Horizons System.