Late arrhythmic disorders after transcatheter aortic valve implantation

L'avènement du remplacement de la valve aortique par cathéter (TAVI) a entraîné un changement de pratique dans le traitement de la sténose aortique. Le TAVI est devenu le traitement de choix pour les patients à risque chirurgical moyen à élevé et son expansion vers le traitement des patients à faible risque est déjà à l'étude. Au cours des dernières années, les améliorations successives apportées aux systèmes de valvules cardiaques par cathéter ont permis de réduire progressivement le nombre de complications péri-procédurales et de décès. Cependant, certains problèmes restent à résoudre. Les troubles de la conduction tels que le bloc de branche gauche nouvellement apparu ou le bloc auriculo-ventriculaire de haut degré nécessitant une implantation permanente de stimulateur cardiaque n'ont pas diminué avec le temps et restent la complication la plus fréquente de la procédure. Alors que les études précédentes se sont concentrées sur l'apparition des troubles de la conduction dans la période péri procédurale, il existe peu de données sur les épisodes tardifs (après la sortie de l'hôpital). D'autre part, la prévalence et l'impact clinique des tachyarythmies chez les patients après un TAVI ont été moins étudiés, en particulier après la sortie de l'hôpital. Différents inconvénients restent non résolus dans ce contexte (par exemple, l'évolution à long terme de l'ECG chez des patients sans troubles de la conduction, la prise en charge des patients avec nouveau bloc de branche gauche, les prédicteurs de la régression des anomalies à l'ECG chez des patients avec bloc de branche gauche). En outre, la surveillance électrocardiographique continue est apparue comme un outil utile pour diagnostiquer les troubles arythmiques (brady- et tachyarythmies) après le départ de l'hôpital, mais les données disponibles dans le cadre du TAVI sont rares. Leur sécurité et leur utilité clinique restent donc à élucider. Les principaux objectifs de ce projet de recherche doctoral sont les suivants: (i) évaluer l'incidence et l'impact clinique des troubles arythmiques tardifs (après le départ de l'hôpital) chez les patients avec TAVI, et (ii) démontrer la sécurité et l'utilité de la surveillance continue non invasive de l'ECG après une procédure TAVI.The advent of transcatheter aortic valve implantation (TAVI) has meant a paradigm shift in the treatment of aortic stenosis. TAVI has become the preferred treatment for patients at intermediate to high surgical risk and its expansion towards the treatment of low-risk patients is under study. During the last years, the successive improvements in transcatheter heart valve systems have led to a progressive reduction of periprocedural complications and death. However, some issues remain to be resolved. Conduction disturbances (CDs) such as new-onset left bundle branch block (LBBB) or high-degree atrioventricular block requiring permanent pacemaker (PPM) implantation have not decreased over time and remains the most frequent complication of the procedure. Whereas previous studies focused on the occurrence of CDs in the periprocedural period, scarce data exist on late (after discharge) episodes. On the other hand, the prevalence and clinical impact of new-onset tachyarrhythmias in patients following TAVI have been less studied, especially after the hospital discharge. Different drawbacks remain unsolved in this context (e.g. long-term ECG evolution in patients without ECG-CDs, management of new-onset LBBB, predictors of ECG regression in new-onset LBBB patients). Furthermore, continuous electrocardiographic monitoring has emerged as a useful tool to unravel arrhythmic disorders (either brady and tachyarrhythmias) in the early phase post-discharge, but data in the TAVI setting is scarce. Thus, their safety and clinical usefulness remain to be elucidated. The main objectives of this PhD research project are: (i) to assess the incidence and clinical impact of late arrhythmic disorders (post discharge) in TAVI recipients (ii) to demonstrate the safety and usefulness of non-invasive continuous ECG monitoring post-TAVI

Parametric approximation to optimal averaging in superimposed training schemes under realistic time-variant channels

Proceedings of: 13th IEEE/IET International Symposium on Communication Systems, Networks and Digital Signal Processing, 20-22 July 2022, Porto, Portugal.Superimposed Training (ST) with orthogonal frequency division multiplexing (OFDM) scheme has become an attractive solution to meet the goals of the fifth generation (5G) of mobile communications, by improving the channel estimation performance, which is one of the main challenge in multiple input multiple output (MIMO) systems. This technique does not hinder the throughput, however, it introduces an intrinsic interference since the data and the reference symbols are sent together. In order to mitigate it, several studies propose a time averaging over several OFDM received symbols, where the optimal length of this averaging can be analytically computed by solving a transcendental equation. In this paper, this optimal averaging is approximated by a low complexity parametric approach based on a multiple linear regression model that inputs two parameters, the signal-to-noise ratio (SNR) and the relative speed between the transmitter and receiver, which effectively represents the variability of the channel in time. Results show that the approximated solutions give an error of 0.05% on average and 7% at most in terms of the provided mean square error (MSE) of the channel estimation.This work has been supported by a fellowship from the Spanish Ministry of Science and Innovation, under grant PRE2018-084315, and, by the Spanish National Project IRENE-EARTH (PID2020-115323RB-C33/AEI/10.13039/501100011033)

Optimum Averaging of Superimposed Training Schemes in OFDM under Realistic Time-Variant Channels

The current global bandwidth shortage in orthogonal frequency division multiplexing (OFDM)-based systems motivates the use of more spectrally efficient techniques. Superimposed training (ST) is a candidate in this regard because it exhibits no information rate loss. Additionally, it is very flexible to deploy and it requires low computational cost. However, data symbols sent together with training sequences cause an intrinsic interference. Previous studies, based on an oversimplified channel (a quasi-static channel model) have solved this interference by averaging the received signal over the coherence time. In this paper, the mean square error (MSE) of the channel estimation is minimized in a realistic time-variant scenario. The optimization problem is stated and theoretical derivations are presented to attain the optimum amount of OFDM symbols to be averaged. The derived optimal value for averaging is dependent on the signal-to-noise ratio (SNR) and it provides a better MSE, of up to two orders of magnitude, than the amount given by the coherence time. Moreover, in most cases, the optimal number of OFDM symbols for averaging is much shorter, about 90% reduction of the coherence time, thus it provides a decrease of the system delay. Therefore, these results match the goal of improving performance in terms of channel estimation error while getting even better energy efficiency, and reducing delays.This work was supported by the Spanish National Project Hybrid Terrestrial/Satellite Air Interface for 5G and Beyond - Areas of Dif-cult Access (TERESA-ADA) [Ministerio de Economía y Competitividad (MINECO)/Agencia Estatal de Investigación (AEI)/Fondo Europeo de Desarrollo Regional (FEDER), Unión Europea (UE)] under Grant TEC2017-90093-C3-2-R

Parametric model and estimator classifier for optimal averaging in mobile OFDM systems with superimposed training

Proceedings of: 2023 International Technical Conference on Circuits/Systems, Computers, and Communications (ITC-CSCC), 25-28 June 2023, Jeju, Republic of Korea.Superimposed training (ST) is an attractive technique for channel estimation in orthogonal frequency division multiplexing (OFDM) modulation. However, its main challenge is the intrinsic interference due to the joint transmission of pilot and data symbols, which can be mitigated by averaging the received signal. Previous works analyzed the mean square error (MSE) of the channel estimation, for both least squares (LS) and minimum MSE (MMSE) estimators, and showed that, under realistic channel models, the optimum number of averaged symbols could be computed by solving a transcendental equation. In this paper, as a practical implementation proposal, these optimum averaging values are parametrically approximated with a multilinear regression model. Also, it is proposed an accurate classifier that, under delay and performance tolerances, is able to select the most suitable estimator between LS and MMSE

Creació automàtica de vídeos a partir de fotografies

El projecte consisteix en disenyar i crear un espai web on els usuaris puguin pujar col.leccions de fotografies, gestionant albums per directoris. A partir de les fotografies emmagatzemades en un album es podrà crear de forma automàtica un video-clip com a seqüencia de les fotografies. El video clip es podrà enviar a diversos terminals mòbils per la seva visualització

Altered protein expression and protein nitration pattern during d-galactosamine-induced cell death in human hepatocytes: a proteomic analysis

BACKGROUND/AIMS: Hepatic injury by d-galactosamine (d-GalN) is a suitable experimental model of hepatocellular injury. The induction of oxidative and nitrosative stress participates during d-GalN-induced cell death in cultured rat hepatocytes. This study aimed to identify protein expression changes during the induction of apoptosis and necrosis by d-GalN in cultured human hepatocytes. METHODS: A proteomic approach was used to identify the proteins involved and those altered by tyrosine nitration. A high dose of d-GalN (40 mM) was used to induce apoptosis and necrosis in primary culture of human hepatocytes. Cellular lysates prepared at different times after addition of d-GalN were separated by two-dimensional electrophoresis. Gel spots with an altered expression and those matching nitrotyrosine-immunopositive proteins were excised and analyzed by mass spectrometry. RESULTS: d-GalN treatment upregulated microsomal cytochrome b5, fatty acid binding protein and manganese superoxide dismutase, and enhanced annexin degradation. d-GalN increased tyrosine nitration of four cytosolic (Hsc70, Hsp70, annexin A4 and carbonyl reductase) and three mitochondrial (glycine amidinotransferase, ATP synthase beta chain, and thiosulfate sulfurtransferase) proteins in human hepatocytes. CONCLUSIONS: The results provide evidences that oxidative stress and nitric oxide-derived reactive oxygen intermediates induce specific alterations in protein expression that may be critical for the induction of apoptosis and necrosis by d-GalN in cultured human hepatocytes

Assessment of the temperature of waterproofing membrane when a recycled crushed glass finish layer is used on flat roofs to protect from sun radiance

The aim of this research was to determine the impact of the use of a recycled crushed glass finish coat on flat roofs to reduce the transmission of heat from sun radiance to indoor spaces in the buildings. This research forms part of previous studies carried out by LiTa on the application of cool roof products to reduce the energy required for air-conditioning inside buildings. Many flat roofs are finished with crushed stone aggregates of natural or artificial origin. The use of recycled crushed glass as a cool roof is potentially a double opportunity to reduce the environmental footprint: it is a recycled material and it may reduce air-conditioning demand. In order to evaluate the real efficiency of recycled crushed glass, this research compared the results with other technical alternatives that are generally applied in real conditions.Peer ReviewedPostprint (published version

Diminished Perisomatic GABAergic Terminals on Cortical Neurons Adjacent to Amyloid Plaques

One of the main pathological hallmarks of Alzheimer's disease (AD) is the accumulation of plaques in the cerebral cortex, which may appear either in the neuropil or in direct association with neuronal somata. Since different axonal systems innervate the dendritic (mostly glutamatergic) and perisomatic (mostly GABAergic) regions of neurons, the accumulation of plaques in the neuropil or associated with the soma might produce different alterations to synaptic circuits. We have used a variety of conventional light, confocal and electron microscopy techniques to study their relationship with neuronal somata in the cerebral cortex from AD patients and APP/PS1 transgenic mice. The main finding was that the membrane surfaces of neurons (mainly pyramidal cells) in contact with plaques lack GABAergic perisomatic synapses. Since these perisomatic synapses are thought to exert a strong influence on the output of pyramidal cells, their loss may lead to the hyperactivity of the neurons in contact with plaques. These results suggest that plaques modify circuits in a more selective manner than previously thought

Xenobiotic metabolism: the effect of acute kidney injury on non-renal drug clearance and hepatic drug metabolism.

Acute kidney injury (AKI) is a common complication of critical illness, and evidence is emerging that suggests AKI disrupts the function of other organs. It is a recognized phenomenon that patients with chronic kidney disease (CKD) have reduced hepatic metabolism of drugs, via the cytochrome P450 (CYP) enzyme group, and drug dosing guidelines in AKI are often extrapolated from data obtained from patients with CKD. This approach, however, is flawed because several confounding factors exist in AKI. The data from animal studies investigating the effects of AKI on CYP activity are conflicting, although the results of the majority do suggest that AKI impairs hepatic CYP activity. More recently, human study data have also demonstrated decreased CYP activity associated with AKI, in particular the CYP3A subtypes. Furthermore, preliminary data suggest that patients expressing the functional allele variant CYP3A5*1 may be protected from the deleterious effects of AKI when compared with patients homozygous for the variant CYP3A5*3, which codes for a non-functional protein. In conclusion, there is a need to individualize drug prescribing, particularly for the more sick and vulnerable patients, but this needs to be explored in greater depth