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| 2. |
- Bollmann, Andreas, et al.
(författare)
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Analysis of surface electrocardiograms in atrial fibrillation: techniques, research, and clinical applications
- 2006
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Ingår i: Europace. - : Oxford University Press (OUP). - 1532-2092. ; 8:11, s. 911-926
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Forskningsöversikt (refereegranskat)abstract
- Atrial. fibrillation (AF) is the most common arrhythmia encountered in clinical practice. Neither the natural history of AF nor its response to therapy is sufficiently predictable by clinical and echocardiographic parameters. The purpose of this article is to describe technical aspects of novel electrocardiogram (ECG) analysis techniques and to present research and clinical applications of these methods for characterization of both the fibrillatory process and the ventricular response during AF Atrial fibrillatory frequency (or rate) can reliably be assessed from the surface ECG using digital signal processing (extraction of atrial, signals and spectral analysis). This measurement shows large inter-individual variability and correlates well with intra-atriat cycle length, a parameter which appears to have primary importance in AF maintenance and response to therapy. AF with a tow fibrillatory rate is more likely to terminate spontaneously and responds better to antiarrhythmic drugs or cardioversion, whereas high-rate AF is more often persistent and refractory to therapy. Ventricular responses during AF can be characterized by a variety of methods, which include analysis of heart rate variability, RR-interval histograms, Lorenz plots, and non-linear dynamics. These methods have all shown a certain degree of usefulness, either in scientific explorations of atrioventricular (AV) nodal function or in selected clinical questions such as predicting response to drugs, cardioversion, or AV nodal modification. The role of the autonomic nervous system for AF sustenance and termination, as well as for ventricular rate responses, can be explored by different ECG analysis methods. In conclusion, non-invasive characterization of atrial fibrillatory activity and ventricular response can be performed from the surface ECG in AF patients. Different signal processing techniques have been suggested for identification of underlying AF pathomechanisms and prediction of therapy efficacy.
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| 3. |
- Corino, Valentina D. A., et al.
(författare)
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Atrioventricular nodal function during atrial fibrillation: Model building and robust estimation
- 2013
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Ingår i: Biomedical Signal Processing and Control. - : Elsevier BV. - 1746-8094. ; 8:6, s. 1017-1025
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Tidskriftsartikel (refereegranskat)abstract
- Statistical modeling of atrioventricular (AV) nodal function during atrial fibrillation (AF) is revisited for the purpose of defining model properties and improving parameter estimation. The characterization of AV nodal pathways is made more detailed and the number of pathways is now determined by the Bayesian information criterion, rather than just producing a probability as was previously done. Robust estimation of the shorter refractory period (i.e., of the slow pathway) is accomplished by a Hough-based technique which is applied to a Poincare plot of RR intervals. The performance is evaluated on simulated data as well as on ECG data acquired from AF patients during rest and head-up tilt test. The simulation results suggest that the refractory period of the slow pathway can be accurately estimated even in the presence of many artifacts. They also show that the number of pathways can be accurately determined. The results from ECG data show that the refined AV node model provides significantly better fit than did the original model, increasing from 85 +/- 5% to 88 +/- 4% during rest, and from 86 +/- 5% to 87 +/- 3% during tilt. When assessing the effect of sympathetic stimulation, the AF frequency increased significantly during tilt (6.25 +/- 0.58 Hz vs. 6.32 +/- 0.61 Hz, p <0.05, rest vs. tilt) and the prolongation of the refractory periods of both pathways decreased significantly (slow pathway: 0.23 +/- 0.20 s vs. 0.11 +/- 0.10 s, p <0.001, rest vs. tilt; fast pathway: 0.24 +/- 0.31 s vs. 0.16 +/- 0.19s, p <0.05, rest vs. tilt). The results show that AV node characteristics can be assessed noninvasively for the purpose of quantifying changes induced by autonomic stimulation. (C) 2012 Elsevier Ltd. All rights reserved.
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| 4. |
- Corino, Valentina D A, et al.
(författare)
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Statistical modeling of atrioventricular nodal function during atrial fibrillation : An update
- 2013
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Ingår i: BIOSIGNALS 2013 - Proceedings of the International Conference on Bio-Inspired Systems and Signal Processing. - 9789898565365 ; , s. 25-29
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Konferensbidrag (refereegranskat)abstract
- This paper introduces a number of advancements of our recently proposed model of atrioventricular (AV) node function during atrial fibrillation (AF). The model is defined by parameters characterizing the arrival rate of atrial impulses, the probability of an impulse choosing either one of the two AV nodal pathways, the refractory periods of these pathways, and their prolongation. In the updated model, the characterization of AV nodal pathways is made more detailed and the number of pathways is determined by the Bayesian information criterion. The performance is evaluated on ECG data acquired from twenty-five AF patients during rest and head-up tilt test. The results show that the refined AV node model provides significantly better fit than did the original model. During tilt, the AF frequency increased (6.25 ±0.58 Hz vs. 6.32 ±0.61 Hz, p < 0.05, rest vs. tilt) and the prolongation of the refractory periods decreased for both pathways (slow pathway: 0.23 ±0.20 s vs. 0.11 ±0.10 s, p < 0.001, rest vs. tilt; fast pathway: 0.24±0.31 s vs. 0.16±0.19 s, p < 0.05, rest vs. tilt). These results show that AV node characteristics can be assessed noninvasively for the purpose of quantifying changes induced by autonomic stimulation.
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| 5. |
- Corino, Valentina D. A., et al.
(författare)
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Statistical Modeling of Atrioventricular Nodal Function During Atrial Fibrillation Focusing on the Refractory Period Estimation
- 2014
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Ingår i: Biomedical Engineering Systems and Technologies (Biostec 2013). - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1865-0929. ; 452, s. 258-268
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Konferensbidrag (refereegranskat)abstract
- We have recently proposed a statistical AV node model defined by a set of parameters characterizing the arrival rate of atrial impulses, the probability of an impulse passing through the fast or the slow pathway, the refractory periods of the pathways, and the prolongation of refractory periods. All parameters are estimated from the RR interval series using maximum likelihood (ML) estimation, except for the mean arrival rate of atrial impulses which is estimated by the AF frequency derived from the f-waves. In this chapter, we compare four different methods, based either on the Poincare plot or ML estimation, for determining the refractory period of the slow pathway. Simulation results show better performance of the ML estimator, especially in the presence of artifacts due to premature ventricular beats or misdetected beats. The performance was also evaluated on ECG data acquired from 26 AF patients during rest and head-up tilt test. During tilt, the AF frequency increased (6.08 +/- 1.03 Hz vs. 6.20 +/- 0.99 Hz, p < 0.05, rest vs. tilt) and the refractory periods of both pathways decreased (slow pathway: 0.43 +/- 0.12 s vs. 0.38 +/- 0.12 s, p = 0.001, rest vs. tilt; fast pathway: 0.55 +/- 0.14 s vs. 0.47 +/- 0.11 s, p < 0.05, rest vs. tilt). These results show that AV node characteristics can be assessed non-invasively to quantify changes induced by autonomic stimulation.
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| 6. |
- Husser, Oliver, et al.
(författare)
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Exercise testing for non-invasive assessment of atrial electrophysiological properties in patients with persistent atrial fibrillation
- 2007
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Ingår i: Europace. - : Oxford University Press (OUP). - 1532-2092. ; 9:8, s. 627-632
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Tidskriftsartikel (refereegranskat)abstract
- Aims Experimental studies suggest that the autonomic nervous system modulates atrial refractoriness and conduction velocity in atrial. fibrillation (AF). These modulatory effects are, however, difficult to assess in the clinical setting. This study sought to non-invasively characterize in patients with persistent AF, the influence of autonomic modulation induced by exercise on atrial fibrillatory rate as marker of atrial refractoriness and to identify clinical and electrocardiographic predictors of atrial rate response. Methods and results In 24 patients (16 mates, mean age 60 +/- 13 years) with persistent AF (16 +/- 25 months), continuous ECGs were recorded during bicycle exercise testing. Fibrillatory rate (in fibrillations per minute, fpm) was assessed at baseline and immediately after termination of exercise with spatiotemporal QRST cancellation and time-frequency analysis. Ventricular response was characterized by time-domain HRV indices. Exercise had no influence on mean fibrillatory rate (409 +/- 42 vs. 414 +/- 43 fpm, P = NS). Seven patients responded to exercise with an increase in fibrillatory rate (26 10 fpm, P < 0.001 and three with a decrease (-21 +/- 8 fpm, P < 0.001), while the remaining 14 patients did not show a response. Responders' HRV indices changed in response to exercise similarly to that of non-responders. Their baseline fibrillatory rate was, however, lower than that of non-responders (387 +/- 18 vs. 425 +/- 48 fpm, P = 0.028). No other clinical or echocardiographic variable was associated with fibrillatory rate response. Twelve weeks after cardioverson, responders were more likely to remain in sinus rhythm than non-responders (88 vs. 46 %, P = 0.04). Conclusions Exercise-induced autonomic activation produces changes in atrial. etectrophysiological properties that can be detected by time-frequency analysis. Higher baseline fibrillatory rates are associated with an impaired atrial response to exercise that suggests advanced electrical remodelling and reduced sensitivity to autonomic stimuli.
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| 7. |
- Manca, Nicola, et al.
(författare)
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Strain, Young’s modulus, and structural transition of EuTiO 3 thin films probed by micro-mechanical methods
- 2023
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Ingår i: APL Materials. - 2166-532X. ; 11:10
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Tidskriftsartikel (refereegranskat)abstract
- EuTiO3 (ETO) is a well-known complex oxide mainly investigated for its magnetic properties and its incipient ferro-electricity. In this work, we demonstrate the realization of suspended micro-mechanical structures, such as cantilevers and micro-bridges, from 100 nm-thick single-crystal epitaxial ETO films deposited on top of SrTiO3(100) substrates. By combining profile analysis and resonance frequency measurements of these devices, we obtain the Young’s modulus, strain, and strain gradients of the ETO thin films. Moreover, we investigate the ETO anti-ferro-distortive transition by temperature-dependent characterizations, which show a non-monotonic and hysteretic mechanical response. The comparison between experimental and literature data allows us to weight the contribution from thermal expansion and softening to the tuning slope, while a full understanding of the origin of such a wide hysteresis is still missing. We also discuss the influence of oxygen vacancies on the reported mechanical properties by comparing stoichiometric and oxygen-deficient samples.
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| 8. |
- Stacchi, Claudio, et al.
(författare)
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The 1st Baltic Osseointegration Academy and Lithuanian University of Health Sciences Consensus Conference 2016. Summary and Consensus Statements : Group I - Peri-Implantitis Aetiology, Risk Factors and Pathogenesis
- 2016
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Ingår i: Journal of Oral & Maxillofacial Research. - : Stilus Optimus. - 2029-283X. ; 7:3:e7
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Forskningsöversikt (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: The task of Group 1 was to review and update the existing data concerning aetiology, risk factors and pathogenesis of peri-implantitis. Previous history of periodontitis, poor oral hygiene, smoking and presence of general diseases have been considered among the aetiological risk factors for the onset of peri-implant pathologies, while late dental implant failures are commonly associated with peri-implantitis and/or with the application of incorrect biomechanical forces. Special interest was paid to the bone cells dynamics as part of the pathogenesis of peri-implantitis. Material and Methods: The main areas indagated by this group were as follows: in uence of smoking, history of periodontitis and general diseases on peri-implantitis development, bio-mechanics of implant loading and its in uence on peri-implant bone and cellular dynamics related to the pathogenesis of peri-implantitis. The systematic reviews and/or meta- analyses were registered in PROSPERO, an international prospective register of systematic reviews: http://www.crd.york. ac.uk/PROSPERO/. The literature in the corresponding areas of interest was screened and reported following the PRISMA (Preferred Reporting Item for Systematic Review and Meta-Analysis) Statement: http://www.prisma-statement.org/. Method of preparation of the systematic reviews, based on comprehensive search strategies, was discussed and standardized. The summary of the materials and methods employed by the authors in preparing the systematic reviews and/or meta-analyses is presented in Preface chapter. Results: The results and conclusions of the review process are presented in the respective papers. One systematic review with meta-analysis, three systematic reviews and one theoretical analysis were performed. The group′s general commentaries, consensus statements, clinical recommendations and implications for research are presented in this article.
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| 9. |
- Glasbey, JC, et al.
(författare)
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- 2021
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swepub:Mat__t
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