| 1. |
- 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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| 2. |
- Gomez, Neurys, et al.
(författare)
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Changes in T-Peak-to-T-End Morphology Measured by Time-Warping are Associated with Ischemia-Induced Ventricular Fibrillation in a Porcine Model
- 2023
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Ingår i: Computing in Cardiology, CinC 2023. - 2325-8861 .- 2325-887X. - 9798350382525
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Konferensbidrag (refereegranskat)abstract
- In this work, we use a time-warping-based morphology variation index, d_{w}, computed between the peak and the end of the T-wave, and assess its association with the occurrence of ventricular fibrillation (VF) episodes in ischemic conditions. ECG recordings from 26 pigs under-going a 40-minute coronary occlusion were analyzed. The d_{w} series was obtained by quantifying the morphological differences between the final part of the T wave at different stages of the occlusion and a reference T wave in the control recording. During control recordings, d_{w} remained stationary with a median value along each recording of 1.76 ms, IQR of 1.80, while during artery occlusion followed a well-marked gradual increasing trend as ischemia progressed, with median of 15.47 ms, IQR of 18.53. At the 20-to-25 min period from occlusion onset (and during 5 min prior to VF episode) dw averages in the VF group was significantly higher than in the non-VF group with median values of 40.0 (and 34.4) vs 7.8 (and 7.7) ms, with p-values of 0.002 (and 0.001), respectively. In conclusion, dynamic increases of the d_{w} index during ischaemia progression in pigs are associated with VF occurrence.
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| 3. |
- Karlsson, Mattias, et al.
(författare)
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ECG-based Assessment and Therapeutic Implications of AV Nodal Conduction Dynamics During Atrial Fibrillation
- 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
- The conduction properties of the atrioventricular (AV) node have a significant impact on heart rate during permanent atrial fibrillation (AF), and can be modulated through the use of β-blockers or calcium channel blockers. These drugs have different physiological effects and are often selected empirically. Hence, an improved understanding of how these drugs affect the AV node conduction properties may contribute to personalized treatment of AF. We propose a novel methodology for estimating the refractory period and conduction delay dynamics of the fast and slow pathways of the AV node from 24-hour ambulatory ECG recordings. Our approach comprises a network model of the AV node, a problem-specific genetic algorithm, and an approximate Bayesian computation algorithm for estimating the posterior distribution of the AV node properties. We analyzed 24-hour ambulatory ECG recordings at baseline from 51 patients with permanent AF. Interestingly, a moderate correlation between the short-term variability in the refractory period for the fast pathway and reduction in heart rate during treatment with metoprolol (ρ = 0.48, p < 0.005) was found. Thus, the proposed methodology enables individualized characterization of the AV node and can potentially assist in treatment selection.
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| 4. |
- Perez, Cristina, et al.
(författare)
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Evaluation of a QT Adaptation Time Estimator for ECG Exercise Stress Test in Controlled Simulation
- 2023
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Ingår i: Computing in Cardiology, CinC 2023. - 2325-887X .- 2325-8861. - 9798350382525
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Konferensbidrag (refereegranskat)abstract
- Slowed adaptation of the QT interval to sudden abrupt heart rate (HR) changes has been identified as a marker of ventricular arrhythmic risk. However, abrupt HR changes are difficult to induce in patients. Quantifying the QT adaptation time in gradual HR changes, as observed in ECGs recording during an exercise stress test, has been recently proposed. The time lag between the QT series and an instantaneous memoryless HR-dependent QT series along stress test was computed as QT memory. Here, this method was evaluated in a control scenario using simulated exercise stress test ECG signals presenting different QT adaptation times. The method robustness was studied by contaminating the ECGs with muscular noise (MN) signals with different Signal-to-Noise ratio (SNR) values, either synthetic or extracted from real recordings. We found that delineation of the T-wave end point in the first transformed lead from Periodic Component Analysis offers the best performance for low SNR. Moreover, we confirmed that the estimator provides an unbiased estimate of the QT memory introduced in the simulations for the studied range of SNR values (25 to 50 dB).
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| 5. |
- Plusciauskaite, Vilma, et al.
(författare)
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Detection of Pre-and Post-Trigger Atrial Fibrillation in Long-Term Photoplethysmogram Signals Acquired in Free-Living
- 2023
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Ingår i: Computing in Cardiology, CinC 2023. - 9798350382525
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Konferensbidrag (refereegranskat)abstract
- Modifiable factors, such as alcohol or physical exertion, may trigger atrial fibrillation (AF) episodes. Identifying and eliminating these triggers can lead to effective strategies which reduce risk of AF recurrence. This study aims to evaluate pre-and post-trigger AF in long-term photo-plethysmogram (PPG) signals obtained during daily living from patients with paroxysmal AF. Thirty-seven patients were instructed to wear a wrist-worn device for a week. They were also asked to log suspected triggers using a smartphone app. Of these patients, 15 experienced AF episodes, resulting in an average AF burden of 0.15. The results indicate that longer post-trigger analysis time intervals resulted in better performance of PPG-based AF detection. The sensitivity was highest for the 16-h post-trigger interval (0.76) and lowest for the 4-h interval (0.43). In contrast, the specificity slightly decreased with an increasing longer post-trigger analysis time interval, being 0.98 and 0.95 for the 4-h and 16-h intervals, respectively. The PPG-based post-trigger AF burden was approximately half of that determined by the annotated ECG-based AF pattern. The study suggests that long-term PPG-based monitoring is a suitable alternative for detecting post-trigger AF instead of ECG-based. However, the accuracy of AF burden estimation using PPG-based technology still calls for improvement.
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