| 1. |
- Abdollahpur, Mostafa, et al.
(författare)
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A subspace projection approach to quantify respiratory variations in the f-wave frequency trend
- 2022
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Ingår i: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Background: The autonomic nervous system (ANS) is known as a potent modulator of the initiation and perpetuation of atrial fibrillation (AF), hence information about ANS activity during AF may improve treatment strategy. Respiratory induced ANS variation in the f-waves of the ECG may provide such information. Objective: This paper proposes a novel approach for improved estimation of such respiratory induced variations and investigates the impact of deep breathing on the f-wave frequency in AF patients. Methods: A harmonic model is fitted to the f-wave signal to estimate a high-resolution f-wave frequency trend, and an orthogonal subspace projection approach is employed to quantify variations in the frequency trend that are linearly related to respiration using an ECG-derived respiration signal. The performance of the proposed approach is evaluated and compared to that of a previously proposed bandpass filtering approach using simulated f-wave signals. Further, the proposed approach is applied to analyze ECG data recorded for 5 min during baseline and 1 min deep breathing from 28 AF patients from the Swedish cardiopulmonary bioimage study (SCAPIS). Results: The simulation results show that the estimates of respiratory variations obtained using the proposed approach are more accurate than estimates obtained using the previous approach. Results from the analysis of SCAPIS data show no significant differences between baseline and deep breathing in heart rate (75.5 ± 22.9 vs. 74 ± 22.3) bpm, atrial fibrillation rate (6.93 ± 1.18 vs. 6.94 ± 0.66) Hz and respiratory f-wave frequency variations (0.130 ± 0.042 vs. 0.130 ± 0.034) Hz. However, individual variations are large with changes in heart rate and atrial fibrillatory rate in response to deep breathing ranging from -9% to +5% and -8% to +6%, respectively and there is a weak correlation between changes in heart rate and changes in atrial fibrillatory rate ( r = 0.38, p < 0.03). Conclusion: Respiratory induced f-wave frequency variations were observed at baseline and during deep breathing. No significant changes in the magnitude of these variations in response to deep breathing was observed in the present study population.
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| 2. |
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| 3. |
- Abdollahpur, Mostafa, et al.
(författare)
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Respiratory Induced Modulation in f-Wave Characteristics During Atrial Fibrillation
- 2021
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Ingår i: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- The autonomic nervous system (ANS) is an important factor in cardiac arrhythmia, and information about ANS activity during atrial fibrillation (AF) may contribute to personalized treatment. In this study we aim to quantify respiratory modulation in the f-wave frequency trend from resting ECG. First, an f-wave signal is extracted from the ECG by QRST cancelation. Second, an f-wave model is fitted to the f-wave signal to obtain a high resolution f-wave frequency trend and an index for signal quality control ((Formula presented.)). Third, respiratory modulation in the f-wave frequency trend is extracted by applying a narrow band-pass filter. The center frequency of the band-pass filter is determined by the respiration rate. Respiration rate is estimated from a surrogate respiration signal, obtained from the ECG using homomorphic filtering. Peak conditioned spectral averaging, where spectra of sufficient quality from different leads are averaged, is employed to obtain a robust estimate of the respiration rate. The envelope of the filtered f-wave frequency trend is used to quantify the magnitude of respiratory induced f-wave frequency modulation. The proposed methodology is evaluated using simulated f-wave signals obtained using a sinusoidal harmonic model. Results from simulated signals show that the magnitude of the respiratory modulation is accurately estimated, quantified by an error below 0.01 Hz, if the signal quality is sufficient ((Formula presented.)). The proposed method was applied to analyze ECG data from eight pacemaker patients with permanent AF recorded at baseline, during controlled respiration, and during controlled respiration after injection of atropine, respectively. The magnitude of the respiratory induce f-wave frequency modulation was 0.15 ± 0.01, 0.18 ± 0.02, and 0.17 ± 0.03 Hz during baseline, controlled respiration, and post-atropine, respectively. Our results suggest that parasympathetic regulation affects the magnitude of respiratory induced f-wave frequency modulation.
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| 4. |
- Abdollahpur, Mostafa, et al.
(författare)
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Respiratory Modulation in Permanent Atrial Fibrillation
- 2020
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Ingår i: 2020 Computing in Cardiology, CinC 2020. - 2325-8861 .- 2325-887X. - 9781728173825 ; 2020-September
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Konferensbidrag (refereegranskat)abstract
- Several studies have shown that the autonomic nervous system (ANS) can induce changes during atrial fibrillation (AF). There is currently a lack of methods for quantifying ANS induced variations during AF. The purpose of this study is to quantify respiratory induced modulation in the f-wave frequency trend. Following qrst-cancellation, the local f-wave frequency is estimated by fitting a harmonic f-wave model signal and a quality index (SQI) is computed based on the model fit. The resulting frequency trend is filtered using a narrow bandpass filter with a center frequency corresponding to the local respiration rate. The magnitude of the respiratory induced f-wave frequency modulation is estimated by the envelope of the filtered frequency trend. The performance of the method is validated using simulations and the method is applied to analyze ECG data from eight patients with permanent AF recorded during 0.125 Hz frequency controlled respiration before and after the full vagal blockade, respectively. Results from simulated data show the magnitude of the respiratory induced f-wave frequency modulation can be estimated with an error of less than = 0.005Hz if the SQI is above 0.45. The signal quality was sufficient for analysis in 7 out of 8 patients. In 4 patients the magnitude decreased and in 3 patients there was no change.
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| 5. |
- Celotto, Chiara, et al.
(författare)
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Dependence of Atrial Fibrillatory Rate Variations Induced by Head-Up/Down Tilt-Test on Autonomic Action
- 2023
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Ingår i: Computing in Cardiology, CinC 2023. - 2325-887X .- 2325-8861. - 9798350382525 ; 50
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Konferensbidrag (refereegranskat)abstract
- In atrial fibrillation (AF), autonomic nervous system (ANS) differences among individuals may have a substantial influence on the varying effectiveness of anti-AF treatments. This work aimed to assess the relationship between changes in autonomic balance and in atrial fibrillatory rate (AFR) oscillations (F_{mathrm{f}}(t)) induced by head-up (HUT) and head-down (HDT) tilt test. 22 persistent AF (psAF) patients underwent a tilt test protocol and ECGs were recorded and analyzed to extract F_{mathrm{f}}(t) and its respiratory modulation (Delta F_{mathrm{f}}). Electrophysiological simulations of stable reentrant rotors in 2D human atrial psAF tissues were performed. Combinations of different levels of parasympathetic stimulation (PSS) by acetylcholine (ACh) and sympathetic stimulation (SS) by isoproterenol (Iso) were tested. The respiratory-related modulation of ACh was modeled by a cyclic temporal variation of ACh. In the patients, HUT/HDT resulted in an increase/decrease in AFR with respect to baseline (BL). Variations in Delta F_{mathrm{f}} from HDT/HUT to BL/HDT were significantly positively correlated with the variations in mean F_{mathrm{f}}(t)(overline{F}_{mathrm{f}}). In the simulations, higher Iso and/or ACh led to an increase in overline{F}_{mathrm{f}}, while Delta F_{mathrm{f}} was correlated to the range of ACh variation. HUT/HDT increased/decreased AFR, which could be explained by an increase/reduction in SS. The concomitant variation in Delta F_{mathrm{f}} could be linked to changes in PSS.
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| 6. |
- Celotto, Chiara, et al.
(författare)
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Effects of Acetylcholine Release Spatial Distribution on the Frequency of Atrial Reentrant Circuits : a Computational Study
- 2022
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Ingår i: 2022 Computing in Cardiology, CinC 2022. - 2325-887X .- 2325-8861. - 9798350300970 ; 2022-September
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Konferensbidrag (refereegranskat)abstract
- The frequency of the ECG fibrillatory f-waves (Ff) in atrial fibrillation (AF) shows significant variations over time. Cardiorespiratory interactions through the autonomic nervous system have been suggested to play a role in such variations. Here, we tested whether the spatial distribution associated with the release of the parasympathetic neurotransmitter acetylcholine (ACh) could affect the frequency of atrial reentrant circuits. Computational simulations in a human persistent-AF 3D atrial model were performed. We evaluated two different patterns of atrial innervation: ACh release restricted to the area of the ganglionated plexi (GP) and the nerves departing from them, following the so-called octopus hypothesis, and ACh release distributed uniformly randomly throughout the atria. In both cases, ACh release sites occupied 8% of the atria. The temporal pattern of ACh release was simulated following a sinusoidal waveform of frequency 0.125 Hz (respiratory frequency). Different mean levels and peak-to-peak variation ranges of ACh were tested. We found that variations in the dominant frequency Ff followed the simulated temporal ACh pattern in all cases, with Ff modulation being more pronounced for increasingly larger ACh variation ranges. For the tested percentage of ACh release sites (8%), the spatial distribution of ACh did not have an impact on Ff modulation.
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| 7. |
- Celotto, Chiara, et al.
(författare)
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Relationship between Atrial Oscillatory Acetylcholine Release Pattern and f-wave Frequency Modulation : A Computational and Experimental Study
- 2020
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Ingår i: 2020 Computing in Cardiology, CinC 2020. - 2325-8861 .- 2325-887X. - 9781728173825 ; 2020-September
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Konferensbidrag (refereegranskat)abstract
- The frequency of fibrillatory waves (f-waves), Ff, exhibits significant variation over time, and previous studies suggest that some of this variation is related to respiratory modulation through the autonomic nervous system. In this study, we tested the hypothesis that this variation (?Ff) could be related to acetylcholine concentration ([ACh]) release pattern. Electrocardiograms were recorded from seven patients during controlled respiration before and after full vagal blockade, from which f-wave frequency modulation was characterized. Computational simulations in human atrial tissues were performed to assess the effects of [ACh] release pattern on Ff and compared to experimental results in humans. A cross-stimulation protocol was applied onto the tissue to initiate a rotor while cyclically varying [ACh] following a sinusoidal waveform of frequency equal to 0.125 Hz. Different mean levels (0.05, 0.075µM/l) and peak-to-peak ranges (0.1, 0.05, 0.025 µM/l) of [ACh] variation were tested. In all patients, an f-wave frequency modulation could be observed. In 57% of the patients, this modulation was significantly reduced after vagal blockade. Simulations confirmed that rotor frequency variations followed the induced [ACh] patterns. Mean Ff was dependent on mean [ACh] level, while?Ffwas dependent on [ACh] variation range.
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| 8. |
- Celotto, Chiara, et al.
(författare)
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The frequency of atrial fibrillatory waves is modulated by the spatiotemporal pattern of acetylcholine release : a 3D computational study
- 2024
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Ingår i: Frontiers in Physiology. - 1664-042X. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- In atrial fibrillation (AF), the ECG P-wave, which represents atrial depolarization, is replaced with chaotic and irregular fibrillation waves (f waves). The f-wave frequency, F f, shows significant variations over time. Cardiorespiratory interactions regulated by the autonomic nervous system have been suggested to play a role in such variations. We conducted a simulation study to test whether the spatiotemporal release pattern of the parasympathetic neurotransmitter acetylcholine (ACh) modulates the frequency of atrial reentrant circuits. Understanding parasympathetic involvement in AF may guide more effective treatment approaches and could help to design autonomic markers alternative to heart rate variability (HRV), which is not available in AF patients. 2D tissue and 3D whole-atria models of human atrial electrophysiology in persistent AF were built. Different ACh release percentages (8% and 30%) and spatial ACh release patterns, including spatially random release and release from ganglionated plexi (GPs) and associated nerves, were considered. The temporal pattern of ACh release, ACh( t), was simulated following a sinusoidal waveform of frequency 0.125 Hz to represent the respiratory frequency. Different mean concentrations ( A C h ¯ ) and peak-to-peak ranges of ACh (ΔACh) were tested. We found that temporal variations in F f, F f( t), followed the simulated temporal ACh( t) pattern in all cases. The temporal mean of F f( t), F ¯ f , depended on the fibrillatory pattern (number and location of rotors), the percentage of ACh release nodes and A C h ¯ . The magnitude of F f( t) modulation, Δ F f, depended on the percentage of ACh release nodes and ΔACh. The spatial pattern of ACh release did not have an impact on F ¯ f and only a mild impact on Δ F f. The f-wave frequency, being indicative of vagal activity, has the potential to drive autonomic-based therapeutic actions and could replace HRV markers not quantifiable from AF patients.
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| 9. |
- Plappert, Felix, et al.
(författare)
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An atrioventricular node model incorporating autonomic tone
- 2022
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Ingår i: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 13:976468
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Tidskriftsartikel (refereegranskat)abstract
- The response to atrial fibrillation (AF) treatment is differing widely among patients, and a better understanding of the factors that contribute to these differences is needed. One important factor may be differences in the autonomic nervous system (ANS) activity. The atrioventricular (AV) node plays an important role during AF in modulating heart rate. To study the effect of the ANS-induced activity on the AV nodal function in AF, mathematical modelling is a valuable tool. In this study, we present an extended AV node model that incorporates changes in autonomic tone. The extension was guided by a distribution-based sensitivity analysis and incorporates the ANS-induced changes in the refractoriness and conduction delay. Simulated RR series from the extended model driven by atrial impulse series obtained from clinical tilt test data were qualitatively evaluated against clinical RR series in terms of heart rate, RR series variability and RR series irregularity. The changes to the RR series characteristics during head-down tilt were replicated by a 10% decrease in conduction delay, while the changes during head-up tilt were replicated by a 5% decrease in the refractory period and a 10% decrease in the conduction delay. We demonstrate that the model extension is needed to replicate ANS-induced changes during tilt, indicating that the changes in RR series characteristics could not be explained by changes in atrial activity alone.
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| 10. |
- Saiz-Vivo, Javier, et al.
(författare)
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Atrial Fibrillatory Rate Characterization Extracted from Implanted Cardiac Monitor Data
- 2021
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Ingår i: 2021 Computing in Cardiology, CinC 2021. - 2325-8861 .- 2325-887X. - 9781665479165 ; 48
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Konferensbidrag (refereegranskat)abstract
- The aim of this study is to characterize atrial fibrillatory rate (AFR) extracted from a cohort of continuously monitored atrial fibrillation (AF) patients as function of episode duration and onset time. The f-wave signal used to compute the AFR was extracted from a single lead ECG strip of the AF episodes stored in an Implantable Cardiac Monitor (ICM) in a cohort of 99 patients. The f-wave signals were obtained from 1400 AF episodes using a spatiotemporal QRST cancellation process and the AFR was estimated as the fundamental frequency of a model fitted to the extracted f-waves. We studied the relationship between AFR and episode duration and episode onset time, respectively. AFR (median (interquartile range)) was significantly lower (p-value<0.05) in short episodes (<20 min) (5.15 (0.66) Hz) than in longer episodes (5.30 (0.74) Hz). AFR was significantly higher for episodes with onset time at night (00-06) (5.34 (0.82) Hz) than for episodes with onset during the day (10-20) (5.21 (0.70) Hz). Significant differences were also found between the relative AFR (ratio between the AFR and the average AFR of the patient) and episode duration (Short: 99.2 (9.3) %; Long: 100.0 (8.9) %). Data extracted from ICMs shows that that nighttime AF onset and longer duration AF episodes are more common in patients with higher AFR.
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