| 1. |
- Corino, Valentina D.A., et al.
(författare)
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A Mathematical Model of The Atrioventricular Node during Atrial Fibrillation
- 2010
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Ingår i: [Host publication title missing]. - 0276-6574. ; 37, s. 117-120
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Konferensbidrag (refereegranskat)abstract
- The atrioventricular (AV) node plays a crucial role during atrial fibrillation (AF). The aim of this study is to present an AV node model which can be fitted to short-term ECG recordings in order to infer certain AV node characteristics. The proposed model is characterized by: i) the arrival rate of atrial impulses; ii) two different refractory periods, corresponding to dual AV nodal paths; iii) the probability of an atrial impulse choosing either of these pathways; iv) a parameter modeling prolongation of the refractory period due to different physiological reasons. The model was tested on atrial fibrillatory ECGs recorded from 33 patients; the average normalized absolute error between the normalized RR histogram and the estimated model probability density function was 0.0023 ± 0.0016, (20-ms bin size, 0–2 s interval). These preliminary results are encouraging as AV nodal properties can be noninvasively assessed by a set of statistical parameters with a simple electrophysiological interpretation.
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| 2. |
- Corino, Valentina D. A., et al.
(författare)
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An Atrioventricular Node Model for Analysis of the Ventricular Response During Atrial Fibrillation
- 2011
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Ingår i: IEEE Transactions on Biomedical Engineering. - 1558-2531. ; 58:12, s. 3386-3395
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Tidskriftsartikel (refereegranskat)abstract
- This paper introduces a model of the atrioventricular node function during atrial fibrillation (AF), and describes the related ECG-based estimation method. The proposed model is defined by parameters that characterize the arrival rate of atrial impulses, the probability of an impulse choosing either one of the two atrioventricular nodal pathways, the refractory periods of these pathways, and the prolongation of the refractory periods. These parameters are estimated from the RR intervals using maximum likelihood estimation, except for the shorter refractory period which is estimated from the RR interval Poincare plot, and the mean arrival rate of atrial impulses by the AF frequency. Simulations indicated that 200-300 RR intervals are generally needed for the estimates to be accurate. The model was evaluated on 30-min ECG segments from 36 AF patients. The results showed that 88% of the segments can be accurately modeled when the estimated probability density function (PDF) and an empirical PDF were at least 80% in agreement. The model parameters were estimated during head-up tilt test to assess differences caused by sympathetic stimulation. Both refractory periods decreased as a result of stimulation, and the likelihood of an impulse choosing the pathway with the shorter refractory period increased.
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| 3. |
- Corino, Valentina D. A., et al.
(författare)
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Association between Atrial Fibrillatory Rate and Heart Rate Variability in Patients with Atrial Fibrillation and Congestive Heart Failure
- 2013
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Ingår i: Annals of Noninvasive Electrocardiology. - : Wiley. - 1082-720X. ; 18:1, s. 41-50
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Tidskriftsartikel (refereegranskat)abstract
- Background Even if atrial fibrillatory rate (AFR) has been related to clinical outcome in patients with atrial fibrillation (AF), its relation with ventricular response has not been deeply studied. The aim of this study was to investigate the relation between AFR and RR series variability in patients with AF. Methods Twenty-minute electrocardiograms in orthogonal leads were processed to extract AFR, using spatiotemporal QRST cancellation and time frequency analysis, and RR series in 127 patients (age 69 +/- 11 years) with congestive heart failure (NYHA IIIII) enrolled in the MUSIC study (MUerte Subita en Insufficiencia Cardiaca). Heart rate variability and irregularity were assessed by time domain parameters and entropy-based indices, respectively and their correlation with AFR investigated. Results Variability measures seem not to be related to AFR, while irregularity measures do. A significant correlation between AFR and variability parameters of heart rate variability during AF was found only in patients not treated with antiarrhythmics drugs (correlation = 0.56 P < 0.05 for pNN50), while this correlation was lost in patients taking rate- or rhythm-control drugs. A significant positive correlation between AFR and indices of RR irregularity was found, showing that a higher AFR is related to a less organized RR series (correlation = 0.33 P < 0.05 for regularity index for all patients, correlation increased in subgroups of patients treated with the same drug). Conclusions These results suggest that a higher AFR is associated with a higher degree of irregularity of ventricular response that is observed regardless of the use of rate-controlling drugs. Ann Noninvasive Electrocardiol 2013;18(1):41-50
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| 4. |
- 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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| 5. |
- Corino, Valentina D. A., et al.
(författare)
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Beta-blockade and A1-adenosine receptor agonist effects on atrial fibrillatory rate and atrioventricular conduction in patients with atrial fibrillation
- 2014
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Ingår i: Europace. - : Oxford University Press (OUP). - 1532-2092 .- 1099-5129. ; 16:4, s. 587-594
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Tidskriftsartikel (refereegranskat)abstract
- Reduced irregularity of RR intervals in permanent atrial fibrillation (AF) has been associated with poor outcome. It is not fully understood, however, whether modification of atrioventricular (AV) conduction using rate-control drugs affects RR variability and irregularity measures. We aimed at assessing whether atrial fibrillatory rate (AFR) and variability and irregularity of the ventricular rate are modified by a selective A1-adenosine receptor agonist tecadenoson, beta-blocker esmolol, and their combination. Twenty-one patients (age 58 7 years, 13 men) with AF were randomly assigned to either 75, 150, or 300 g intravenous tecadenoson. Tecadenoson was administered alone (Dose Period 1) and in combination (Dose Period 2) with esmolol (100 g/kg/min for 10 min then 50 g/kg/min for 50 min). Heart rate (HR) and AFR were estimated for every 10 min long recording segment. Similarly, for every 10 min segment, the variability of RR intervals was assessed, as standard deviation, pNN20, pNN50, pNN80, and the root of the mean squared differences of successive RR intervals, and irregularity was assessed by non-linear measures such as regularity index (R) and approximate entropy. A marked decrease in HR was observed after both tecadenoson injections, whereas almost no changes could be seen in the AFR. The variability parameters were increased after the first tecadenoson bolus injection. In contrast, the irregularity parameters did not change after tecadenoson. When esmolol was infused, all the variability parameters further increased. Modification of AV node conduction can increase RR variability but does not affect regularity of RR intervals or AFR.
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| 6. |
- Corino, Valentina D.A., et al.
(författare)
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Clinical use and limitations of non-invasive electrophysiological tests in patients with atrial fibrillation
- 2016
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Ingår i: Journal of Atrial Fibrillation. - 1941-6911. ; 9:1, s. 62-67
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Tidskriftsartikel (refereegranskat)abstract
- Atrial fibrillation (AF) is a complex arrhythmia, that has been studied non-invasively assessing atrial refractory period, atrioventricular node (AV) node refractory period, and ventricular response. The AV node plays a fundamental role as it filters many of the numerous irregular atrial impulses bombarding the node. Despite its importance, the electrophysiological (EP) characteristics of the AV node are not routinely evaluated since conventional EP techniques for assessment of refractory period or conduction velocity of the AV node are not applicable in AF. Since rate-control drugs control ventricular response through their effect on the AV node, noninvasive assessment of AV node electrophysiology may be useful. The RR series, though being highly irregular, contains information that can be used for risk stratification and prediction of outcome. In particular, RR irregularity measures during AF have been shown to be related to clinical outcome. This paper reviews the attempts done to noninvasively characterize the AV node and the ventricular response, highlighting clinical applications and limitations of the noninvasive techniques.
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| 7. |
- Corino, Valentina D. A., et al.
(författare)
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Improved Time-Frequency Analysis of Atrial Fibrillation Signals Using Spectral Modeling
- 2008
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Ingår i: IEEE Transactions on Biomedical Engineering. - 1558-2531. ; 55:12, s. 2723-2730
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Tidskriftsartikel (refereegranskat)abstract
- In patients with atrial fibrillation (AF), the fibrillatory frequency trend and the time-dependent spectral characteristics can be investigated using a spectral profile technique. The spectral profile is updated by fitting each short-time spectrum. The aim of this study is to develop model-based means for stricter control on the update of the spectral profile. A spectral model defined by a superposition of Gaussian functions is suggested for describing the fundamental and harmonics of the atrial waves during AF, thereby accounting for basic characteristics of the typical AF spectrum. The model parameters are obtained from weighted least squares fitting of the model to the observed spectrum. The method was tested on simulated signals as well as on 48 ECG recordings from 15 patients with persistent AF. Using simulated signals, we assessed the accuracy in terms of magnitude and width or the spectral peaks. For SNR = 0 dB, the maximum normalized error was less than 0.2 when estimating magnitude of both the fundamental and the harmonics, whereas it was less than 0.15 for the fundamental and 0.7 for the harmonics with respect to the estimation of the width. We observed a marked Improvement while tracking the main fibrillatory frequency as the error was reduced by more than 50% In comparison with the original method. Analyzing ECGs, reliable spectral profiles were obtained In all recordings, even In those cases (5/48) that were not well characterized by the original method.
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| 8. |
- Corino, Valentina D.A., et al.
(författare)
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Non-invasive evaluation of the effect of metoprolol on the atrioventricular node during permanent atrial fibrillation
- 2014. - January
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Ingår i: Computing in Cardiology 2014. - : Oxford University Press (OUP). - 2325-8861. - 9781479943463 - 9781479943470 ; 41, s. 889-892
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Konferensbidrag (refereegranskat)abstract
- The aim of this study was to evaluate changes in AV nodal properties during administration of metoprolol, using a novel ECG-based method for parameter estimation. The AV nodal parameters account for the probability of an impulse not passing through the fast pathway, the absolute refractory periods of the slow and fast pathways (aRPs and aRPf), representing the functional refractory period, and related prolongation in the respective refractory periods. Twenty patients (age 71±8 years, 14 men) with permanent AF from the RATe control in Atrial Fibrillation (RATAF) database were included in this study. Recordings during baseline and metoprolol administration were analyzed. Furthermore, simulated RR series were generated mimicking metoprolol administration. During metoprolol administration, aRP was significantly prolonged in both pathways (aRPs: 342±39 vs. 408±81 ms, p<0.001; aRPf: 432±74 vs. 527±83 ms, p<0.001). Similar results were found for the simulated RR series: both aRPs and aRPf were significantly prolonged with metoprolol. The AV nodal parameters reflect expected changes after metoprolol administration, i.e., a prolongation in functional refractory period. The simulations suggest that aRP may serve as an estimate of the functional refractory period.
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| 9. |
- Corino, Valentina D. A., et al.
(författare)
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Noninvasive Assessment of Atrioventricular Nodal Function: Effect of Rate-Control Drugs during Atrial Fibrillation
- 2015
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Ingår i: Annals of Noninvasive Electrocardiology. - : Wiley. - 1082-720X. ; 20:6, s. 534-541
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Tidskriftsartikel (refereegranskat)abstract
- Background: During atrial fibrillation (AF), conventional electrophysiological techniques for assessment of refractory period or conduction velocity of the atrioventricular (AV) node cannot be used. We aimed at evaluating changes in AV nodal properties during administration of tecadenoson and esmolol using a novel ECG-based method. Methods: Fourteen patients (age 58 +/- 8 years, 10 men) with AF were randomly assigned to either 75 or 300 mu g intravenous tecadenoson. After tecadenoson wash-out, patients received esmolol continuously (100 mu g/kg per min for 10 mins, then 50 mu g/kg per min for 50 mins). Atrial fibrillatory rate (AFR) and heart rate (HR) were assessed in 15-min segments. Using the novel method, we assessed the absolute refractory periods of the slow and fast pathways (aRPs and aRPf) of the AV node to produce an estimate of the functional refractory period. Results: During esmolol infusion, AFR and HR were significantly decreased and the absolute refractory period was significantly prolonged in both pathways (aRPs: 387 +/- 73 vs 409 +/- 62 ms, P < 0.05; aRPf: 490 +/- 80 vs 529 +/- 58 ms, P < 0.05). During both tecadenoson doses, HR decreased significantly and AFR was unchanged. Both aRPs and aRPf were prolonged for a 75 mu g dose (aRPs: 322 +/- 97 vs 476 +/- 75 ms, P < 0.05; aRPf: 456 +/- 102 vs 512 +/- 55 ms, P < 0.05) whereas a trend toward prolongation was observed for a 300 mu g dose. Conclusions: The estimated parameters reflect expected changes in AV nodal properties, i.e., slower conduction through the AV node for tecadenoson and prolongation of the AV node refractory period for esmolol. Thus, the proposed approach may be used to assess drug effects on the AV node in AF patients.
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| 10. |
- Corino, Valentina D A, et al.
(författare)
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Noninvasive characterization of atrioventricular conduction in patients with atrial fibrillation.
- 2015
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Ingår i: Journal of Electrocardiology. - : Elsevier BV. - 1532-8430 .- 0022-0736. ; 48:6, s. 938-942
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Tidskriftsartikel (refereegranskat)abstract
- The atrioventricular (AV) node plays a fundamental role in patients with atrial fibrillation (AF), acting as a filter to the numerous irregular atrial impulses which bombard the node. A phenomenological approach to better understand AV nodal electrophysiology is to analyze the ventricular response with respect to irregularity. In different cohorts of AF patients, such analysis has been performed with the aim to evaluate the association between ventricular response characteristics and long-term clinical outcome and to determine whether irregularity is affected by rate-control drugs. Another approach to studying AV nodal characteristics is to employ a mathematical model which accounts for the refractory periods of the two AV nodal pathways. With atrial fibrillatory rate and RR intervals as input, the model has been considered for analyzing data during (i) rest and head-up tilt test, (ii) tecadenoson and esmolol, and (iii) rate-control drugs. The present paper provides an overview of our recent work on the characterization and assessment of AV nodal conduction using these two approaches.
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