| 1. |
- Bachi, Lorenzo, et al.
(författare)
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ECG Modeling for Simulation of Arrhythmias in Time-Varying Conditions
- 2023
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Ingår i: IEEE Transactions on Biomedical Engineering. - 0018-9294. ; 70:12, s. 3449-3460
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Tidskriftsartikel (refereegranskat)abstract
- The present paper proposes an ECG simulator that advances modeling of arrhythmias and noise by introducing time-varying signal characteristics. The simulator is built around a discrete-time Markov chain model for simulating atrial and ventricular arrhythmias of particular relevance when analyzing atrial fibrillation (AF). Each state is associated with statistical information on episode duration and heartbeat characteristics. Statistical, time-varying modeling of muscle noise, motion artifacts, and the influence of respiration is introduced to increase the complexity of simulated ECGs, making the simulator well suited for data augmentation in machine learning. Modeling of how the PQ and QT intervals depend on heart rate is also introduced. The realism of simulated ECGs is assessed by three experienced doctors, showing that simulated ECGs are difficult to distinguish from real ECGs. Simulator usefulness is illustrated in terms of AF detection performance when either simulated or real ECGs are used to train a neural network for signal quality control. The results show that both types of training lead to similar performance.
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| 2. |
- Grut, Viktor, et al.
(författare)
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Cytomegalovirus seropositivity is associated with reduced risk of multiple sclerosis : a presymptomatic case-control study
- 2021
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Ingår i: European Journal of Neurology. - : Blackwell Publishing. - 1351-5101 .- 1468-1331. ; 28:9, s. 3072-3079
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Epstein-Barr virus (EBV) and Human herpesvirus 6A (HHV-6A) are associated with increased risk of multiple sclerosis (MS). Conversely, infection with Cytomegalovirus (CMV) has been suggested to reduce the risk of MS but supporting data from presymptomatic studies are lacking. Here, we sought to increase the understanding of CMV in MS aetiology.METHODS: We performed a nested case-control study with presymptomatically collected blood samples identified through cross-linkage of MS registries and Swedish biobanks. Serological antibody response against CMV, EBV and HHV-6A was determined using a bead-based multiplex assay. Odds ratio (OR) with 95 % confidence intervals (CI) for CMV seropositivity as risk factor for MS was calculated by conditional logistic regression and adjusted for EBV and HHV-6A seropositivity. Potential interactions on the additive scale were analysed by calculating attributable proportion due to interaction (AP).RESULTS: Serum samples from 670 pairs of matched cases and controls were included. CMV seropositivity was associated with a reduced risk for MS (OR = 0.70, 95% CI 0.56-0.88, p = 0.003). Statistical interactions on the additive scale were observed between seronegativity for CMV and seropositivity against HHV-6A (AP 0.34, 95% CI 0.06-0.61) and EBV antigen EBNA-1 (amino acid 385-420) at age 20-39 years (AP 0.37, 95% CI 0.09-0.65).CONCLUSIONS: CMV seropositivity is associated with a decreased risk for MS. The protective role for CMV infection in MS aetiology is further supported by the interactions between CMV seronegativity and EBV and HHV-6A seropositivity.
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| 3. |
- Grut, Viktor, et al.
(författare)
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Free vitamin D3 index and vitamin D-binding protein in multiple sclerosis : A presymptomatic case-control study
- 2022
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Ingår i: European Journal of Neurology. - : John Wiley & Sons. - 1351-5101 .- 1468-1331. ; 29:8, s. 2335-2342
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND PURPOSE: High levels of 25-hydroxyvitamin D3 (25[OH]D3 ) are associated with a lower risk for multiple sclerosis (MS). The bioavailability of 25(OH)D3 is regulated by its main plasma carrier, vitamin D-binding protein (DBP). Free 25(OH)D3 can be estimated by also measuring DBP concentration. In addition, DBP has immunomodulatory functions that may independently affect MS pathogenesis. No previous studies have assessed free 25(OH)D3 or DBP in presymptomatically collected samples. This study was undertaken to assess free 25(OH)D3 and DBP as risk factors for MS.METHODS: A nested case-control study was performed with presymptomatic serum samples identified through cross-linkage of MS registries and Swedish biobanks. Concentration of 25(OH)D3 was measured with liquid chromatography and DBP levels with sandwich immunoassay. Free 25(OH)D3 was approximated as free vitamin D3 index: (25[OH]D3 /DBP) × 103 . MS risk was analyzed by conditional logistic regression, calculating odds ratios (ORs) with 95% confidence intervals (CIs).RESULTS: Serum samples from 660 pairs of matched cases and controls were included. At <20 years of age, high levels of free vitamin D3 index were associated with a lower risk of MS (highest vs. lowest quintile: OR = 0.37, 95% CI = 0.15-0.91, p for trend across quintiles = 0.04). At age 30-39 years, high levels of DBP were associated with a lower MS risk (highest vs. lowest quintile: OR = 0.36, 95% CI = 0.15-0.85, p for trend = 0.02).CONCLUSIONS: These findings support the hypothesis that high levels of free 25(OH)D3 at a young age reduce the risk of MS later in life. They also implicate a role for DBP in MS etiology.
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| 4. |
- Grut, Viktor, et al.
(författare)
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Systemic inflammation and risk of multiple sclerosis – A presymptomatic case-control study
- 2022
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Ingår i: Multiple Sclerosis Journal - Experimental, Translational and Clinical. - : SAGE Publications. - 2055-2173. ; 8:4
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Tidskriftsartikel (refereegranskat)abstract
- Background: C-reactive protein (CRP) is a marker of systemic inflammation. Increased levels of CRP in young persons have been suggested to decrease the risk of multiple sclerosis (MS). Objectives: To assess CRP as a risk factor for MS. Methods: Levels of CRP were measured with a high-sensitive immunoassay in biobank samples from 837 individuals who later developed MS and 984 matched controls. The risk of developing MS was analysed by conditional logistic regression on z-scored CRP values. Results: Levels of CRP were not associated with MS risk. Conclusions: We found no association between CRP levels and risk of MS development.
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| 5. |
- Andersson, Richard, et al.
(författare)
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One algorithm to rule them all? : An evaluation and discussion of ten eye movement event-detection algorithms
- 2017
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Ingår i: Behavior Research Methods. - : Springer Science and Business Media LLC. - 1554-3528. ; 49:2, s. 616-637
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Tidskriftsartikel (refereegranskat)abstract
- Almost all eye-movement researchers use algorithms to parse raw data and detect distinct types of eye movement events, such as fixations, saccades, and pursuit, and then base their results on these. Surprisingly, these algorithms are rarely evaluated. We evaluated the classifications of ten eye-movement event detection algorithms, on data from an SMI HiSpeed 1250 system, and compared them to manual ratings of two human experts. The evaluation focused on fixations, saccades, and post-saccadic oscillations. The evaluation used both event duration parameters, and sample-by-sample comparisons to rank the algorithms. The resulting event durations varied substantially as a function of what algorithm was used. This evaluation differed from previous evaluations by considering a relatively large set of algorithms, multiple events, and data from both static and dynamic stimuli. The main conclusion is that current detectors of only fixations and saccades work reasonably well for static stimuli, but barely better than chance for dynamic stimuli. Differing results across evaluation methods make it difficult to select one winner for fixation detection. For saccade detection, however, the algorithm by Larsson, Nyström and Stridh (IEEE Transaction on Biomedical Engineering, 60(9):2484–2493,2013) outperforms all algorithms in data from both static and dynamic stimuli. The data also show how improperly selected algorithms applied to dynamic data misestimate fixation and saccade properties.
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| 6. |
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| 7. |
- Aunes-Jansson, Maria, et al.
(författare)
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Decrease of the atrial fibrillatory rate, increased organization of the atrial rhythm and termination of atrial fibrillation by AZD7009
- 2013
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Ingår i: Journal of Electrocardiology. - : Elsevier BV. - 1532-8430 .- 0022-0736. ; 46:1, s. 29-35
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Tidskriftsartikel (refereegranskat)abstract
- Background: The atrial fibrillatory rate (APR), on AZD7009 as compared to placebo, was investigated as a potential biomarker for electrophysiological effect in early antiarrhythmic drug development. Methods: Patients with permanent AF received infusions of AZD7009 and placebo in an exploratory two-way, single-blind, randomized cross-over study. The ECG was continuously recorded, and following QRST cancellation the APR, its standard deviation (SD), the exponential decay and the atrial electrogram amplitude were determined as 3-min averages. Results: The mean APR rapidly decreased by 43% from baseline (394 +/- 38 to 225 +/- 61 fibrillations/min, p = 0.0003) on AZD7009, but not on placebo. The SD of the AFR and the exponential decay decreased in parallel. In 2 of 8 patients, termination of AF occurred after the APR had decreased by 58% and 53%, respectively. Conclusions: The APR may potentially serve as a biomarker of electrophysiological effects in early evaluation of rhythm control agents. (C) 2013 Elsevier Inc. All rights reserved.
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| 8. |
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| 9. |
- 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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| 10. |
- Bollmann, Andreas, et al.
(författare)
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Atrial fibrillatory rate and risk of left atrial thrombus in atrial fibrillation.
- 2007
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Ingår i: Europace. - : Oxford University Press (OUP). - 1532-2092. ; 9:8, s. 6-621
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Tidskriftsartikel (refereegranskat)abstract
- ims In atrial fibrillation (AF), a relation between electrocardiogram (ECG) fibrillatory wave amplitude and thrombus formation has been sought for long with conflicting results. In contrast, the possible relation between atrial fibrillatory rate obtained from the surface ECG and left atrial thrombus formation in patients with AF is unknown and was consequently evaluated in this study. Methods and results One-hundred and twenty-five patients (mean age 64 ± 12 years, 72% male) with persistent non-valvular AF (mean duration 28 ± 80 days) undergoing transesophageal echocardiography were studied. In all patients, standard 12-lead ECG recordings were acquired before the examination. Atrial fibrillatory rate was determined using spatiotemporal QRST cancellation and time–frequency analysis of lead V1. Atrial fibrillatory rate measured 401 ± 63 fibrillations per minute (fpm, range 235–566 fpm) and was related with age (R = −0.326, P < 0.001), ventricular rate (R = −0.202, P = 0.024), gender (407 ± 62 in males vs. 387 ± 64 fpm in females, P = 0.038) but not AF duration (R = 0.088, P = 0.374), presence of lone AF (408 ± 66 vs. 394 ± 58 fpm, P = 0.228), or beta-blocker or calcium channel blocker treatment (398 ± 63 vs. 405 ± 62 fpm, P = 0.556). Age was the only independent predictor of fibrillatory rate (B = −1.714, P < 0.001). In patients with left atrial thrombus (n = 10), spontaneous echo contrast (SEC) was more frequently present (70 vs. 29 %, p = 0.007) and left atrial appendage (LAA) outflow velocity was lower (26 ± 20 vs. 37 ± 15 cm/s, P = 0.012) than in patients without thrombus (n = 115). In contrast, mean fibrillatory rate, which showed a weak inverse correlation with LAA velocity (R = −0.118, P = 0.048) was not different between both groups (380 ± 56 vs. 403 ± 63 fpm, P = 0.226). Similarly, presence of thrombus and SEC combined was not related with fibrillatory rate. Conclusion Atrial fibrillatory rate obtained from surface ECG lead V1 is not a risk marker for left atrial thrombus formation in AF.
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