| 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. |
- Barquero-Perez, Oscar, et al.
(författare)
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On the influence of heart rate and coupling interval prematurity on heart rate turbulence
- 2017
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Ingår i: IEEE Transactions on Biomedical Engineering. - 1558-2531. ; 64:2, s. 302-309
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Heart rate turbulence (HRT) has been successfully explored for cardiac risk stratification. While HRT is known to be influenced by the heart rate (HR) and the coupling interval (CI), nonconcordant results have been reported on how the CI influences HRT. The purpose of this study is to investigate HRT changes in terms of CI and HR by means of an especially designed protocol. Methods: A dataset was acquired from 11 patients with structurally normal hearts for which CI was altered by different pacing trains and HR by isoproterenol during electrophysiological study (EPS). The protocol was designed so that, first, the effect of HR changes on HRT and, second, the combined effect of HR and CI could be explored. As a complement to the EPS dataset, a database of 24-h Holters from 61 acute myocardial infarction (AMI) patients was studied for the purpose of assessing risk. Data analysis was performed by using different nonlinear ridge regression models, and the relevance of model variables was assessed using resampling methods. The EPS subjects, with and without isoproterenol, were analyzed separately. Results: The proposed nonlinear regression models were found to account for the influence of HR and CI on HRT, both in patients undergoing EPS without isoproterenol and in low-risk AMI patients, whereas this influence was absent in high-risk AMI patients. Moreover, model coefficients related to CI were not statistically significant, p > 0.05, on EPS subjects with isoproterenol. Conclusion: The observed relationship between CI and HRT, being in agreement with the baroreflex hypothesis, was statistically significant (p < 0.05), when decoupling the effect of HR and normalizing the CI by the HR. Significance: The results of this study can help to provide new risk indicators that take into account physiological influence on HRT, as well as to model how this influence changes in different cardiac conditions.
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| 3. |
- Demidova, Marina, et al.
(författare)
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T wave alternans in experimental myocardial infarction: Time course and predictive value for the assessment of myocardial damage.
- 2013
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Ingår i: Journal of Electrocardiology. - : Elsevier BV. - 1532-8430 .- 0022-0736. ; 46:3, s. 263-269
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: T-wave alternans (TWA) is associated with prognosis after myocardial infarction (MI), however its link to the extent of ischemic injury has not been clarified. We analyzed the course of TWA and its relation to myocardial damage in experimental myocardial infarction. METHODS: In 21 pigs, infarction was induced by 40-minute long balloon inflation in LAD under continuous 12-lead ECG monitoring. TWA was assessed in a 32-beat sliding window, using periodic component analysis and the Laplacian Likelihood Ratio method. Myocardium at risk (MaR) and infarct size (IS) were evaluated by SPECT and magnetic resonance imaging respectively. RESULTS: TWA appeared at 7.2±4.5minutes of occlusion, reached its maximum at 12.7±6.3 and lasted until 26.5±9.2minutes. The maximal level of TWA was associated with both MaR (r=0.499, p=0.035) and IS (r=0.65, p=0.004). CONCLUSION: TWA magnitude is associated with both MaR and IS in experiment, which encourages further studies in clinical settings.
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| 4. |
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| 5. |
- Gil, Eduardo, et al.
(författare)
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Heart Rate Turbulence Analysis Based on Photoplethysmography
- 2013
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Ingår i: IEEE Transactions on Biomedical Engineering. - 1558-2531. ; 60:11, s. 3149-3155
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Tidskriftsartikel (refereegranskat)abstract
- The goal of this paper is to determine whether the photoplethysmography (PPG) can replace the ECG-based detection of heart rate turbulence. Using the PPG, classification of ventricular premature beats (VPBs) is accomplished with a linear classifier. The two conventional parameters turbulence onset and slope are studied together with a recently introduced parameter characterizing turbulence shape. Performance is studied on a dataset with 4131 VPBs, recorded from a total of 27 patients in different clinical contexts (hemodialysis treatment, intensive care monitoring, and electrophysiological study). The sensitivity/specificity of VPB classification was found to be 90.5/99.9%, with an accuracy of 99.3%, suggesting that classification of VPBs can be reliable made from the PPG. The main difference between the two types of turbulence analysis stems from the fact that the pulse transit time varies largely immediately after the VPB. Out of the 22 patients which had a sufficient number of VPBs, the outcome of the ECG-and PPG-based analysis was identical in 21. It is concluded that the PPG may serve as a surrogate technique for the ECG in turbulence analysis.
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| 6. |
- 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. - 2325-887X .- 2325-8861. - 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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| 7. |
- Gomez, Neurys, et al.
(författare)
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T-wave Peak-to-End Changes Quantified by Time-Warping Predicts Ventricular Fibrillation in a Porcine Myocardial Infarction Model
- 2024
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Ingår i: IEEE Transactions on Biomedical Engineering. - 0018-9294. ; , s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- Background: The T-peak-to-T-end ($\mathrm{T}_{pe}$) interval has shown potential in predicting ventricular arrhythmic risk. It is an appealing index to be measured during ischemia since it is less influenced by ST-segment changes than the early part of the T wave. A time-warping-based index, derived from a spatially transformed PCA lead, $d^{{\kern0.28436pt}\text{PCA}}_{w,{\scriptscriptstyle \mathrm{T}_{pe}}}$, quantifying changes in the $\mathrm{T}_{pe}$ morphology, has previously demonstrated utility in tracking repolarization changes induced by a 5-minute ischemia model in humans. The value of $d^{{\kern0.28436pt}\text{PCA}}_{w,{\scriptscriptstyle \mathrm{T}_{pe}}}$ as a predictor of ventricular fibrillation (VF) episodes is assessed in a porcine model of myocardial ischemia with ischemia maintained for 40 minutes. Methods: From 32 pigs undergoing a coronary occlusion, pre-occlusion and occlusion ECG recordings from 10 pigs suffering a VF episode after 10 min of occlusion (Delayed VF) and 16 that did not had any episode during the recording were analyzed. The $d^{{\kern0.28436pt}\text{PCA}}_{w,{\scriptscriptstyle \mathrm{T}_{pe}}}$ series was measured by comparing $\mathrm{T}_{pe}$ morphologies at different stages of the occlusion relative to the peak-to-end morphology of a baseline T-wave. Results: During baseline, $d^{{\kern0.28436pt}\text{PCA}}_{w,{\scriptscriptstyle \mathrm{T}_{pe}}}$ remained stationary with an intra-recording median [IQR] value of 1.60 [1.33] ms. During artery occlusion, $d^{{\kern0.28436pt}\text{PCA}}_{w,{\scriptscriptstyle \mathrm{T}_{pe}}}$ followed a well-marked gradual increasing trend as ischemia progressed, reaching a median of 14.58 [17.72] ms. $d^{{\kern0.28436pt}\text{PCA}}_{w,{\scriptscriptstyle \mathrm{T}_{pe}}}$ averages were significantly higher (${p< 0.05}$) in the VF group than in the Non-VF group at time intervals 0-5, 5-10, 10-15, 15-20, 20-25 min after occlusion onset and at 10-15, 5-10 and 5-0 minutes prior to VF episode, with median values of 12.5, 18.8, 26.8, 24.0, 31.0, 18.6, 25.0 and 28.8 vs 6.3, 7.6, 8.0, 7.8, 7.8, 8.5, 7.2 and 6.0 ms, respectively. The $\mathrm{T}_{pe}^{\text{PCA}}$ interval was also significantly higher in the VF group at all analyzed time periods, but with a lower significance level. Pigs with maximum $d^{{\kern0.28436pt}\text{PCA}}_{w,{\scriptscriptstyle \mathrm{T}_{pe}}}$ $\geq$ 20.0 ms and $\mathrm{T}_{pe}^{\text{PCA}}$ $\geq$ 85.4 ms had significantly higher risk for VF occurring in the early 5-10 minutes interval, with 90.0%/75.0% and 80.0%/69.0% sensitivity/specificity, respectively. Univariate Cox analysis yielded hazard ratios of 12.5 for $d^{{\kern0.28436pt}\text{PCA}}_{w,{\scriptscriptstyle \mathrm{T}_{pe}}}$ vs 5.5 for $\mathrm{T}_{pe}^{\text{PCA}}$. Conclusions and Significance: The time-warping-based index, $d^{{\kern0.28436pt}\text{PCA}}_{w,{\scriptscriptstyle \mathrm{T}_{pe}}}$, is a stronger VF predictor than $\mathrm{T}_{pe}^{\text{PCA}}$ during ischemia in a porcine model, advising for further clinical exploration studies in humans.
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| 8. |
- Martinez, Juan Pablo, et al.
(författare)
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Assessment of QT-measurement accuracy using the 12-lead electrocardiogram derived from EASI leads
- 2007
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Ingår i: Journal of Electrocardiology. - : Elsevier BV. - 1532-8430 .- 0022-0736. ; 40:2, s. 172-179
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the present study is to assess QT-interval measurements from the EASI 12-lead electrocardiogram (ECG) as compared with the standard 12-lead ECG. The QT interval was automatically determined in simultaneously recorded standard and EASI 12-lead ECGs, using a validated wavelet-based delineator. The agreement between the 2 sets of measurements was quantified both on a lead-by-lead basis and a multilead basis with global definitions of QRS onset and T-wave end. The results show that the agreement between QT-interval measurements from the 2 lead systems is acceptable, with negligible mean differences and with correlation coefficients ranging from 0.91 to 0.98 depending on the lead studied. Although the SD shows a clear dependence on the selected lead (ranging from 9.2 to 26.4 milliseconds), differences are within the accepted tolerances for automatic delineation. In a few patients, large differences were found, mainly because of changes in morphology present in both lead systems. QT intervals measured by the multilead approach were considerably more stable than single-lead measurements and resulted in a much better agreement between the 2 lead systems (correlation coefficient, 0.98; QT difference, 1.1 +/- 9.8 milliseconds). Thus, the EASI 12-lead ECG may be used for reliable QT monitoring when the multilead delineation approach is adopted. (c) 2007 Elsevier Inc. All rights reserved.
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| 9. |
- Martínez, Juan Pablo, et al.
(författare)
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The STAFF III Database : ECGs recorded during acutely induced myocardial ischemia
- 2017
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Ingår i: Computing in Cardiology. - 2325-8861. ; 44
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Tidskriftsartikel (refereegranskat)abstract
- The STAFF III database was acquired with the aim of better understanding the ECG signatures observed during acute ischemia, with special focus on high-frequency QRS components. The database contains recordings from 104 patients undergoing elective balloon percutaneous coronary intervention. The database has not only been analyzed in numerous clinical studies, but also turned out to be an excellent tool for methodological development. Its use has, by far, exceeded the original aim. Inspired by this fact, the database has now been made publicly available at Physionet.
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| 10. |
- Pablo Martinez, Juan, et al.
(författare)
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Detection Performance and Risk Stratification Using a Model-Based Shape Index Characterizing Heart Rate Turbulence
- 2010
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Ingår i: Annals of Biomedical Engineering. - : Springer Science and Business Media LLC. - 1573-9686 .- 0090-6964. ; 38:10, s. 3173-3184
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Tidskriftsartikel (refereegranskat)abstract
- A detection-theoretic approach to quantify heart rate turbulence (HRT) following a ventricular premature beat is proposed and validated using an extended integral pulse frequency modulation (IPFM) model which accounts for HRT. The modulating signal of the extended IPFM model is projected into a three-dimensional subspace spanned by the Karhunen-Loeve basis functions, characterizing HRT shape. The presence or absence of HRT is decided by means of a likelihood ratio test, the Neyman-Pearson detector, resulting in a quadratic detection statistic. Using a labeled dataset built from different interbeat interval series, detection performance is assessed and found to outperform the two widely used indices: turbulence onset (TO) and turbulence slope (TS). The ability of the proposed method to predict the risk of cardiac death is evaluated in a population of patients (n = 90) with ischemic cardiomyopathy and mild-to-moderate congestive heart failure. While both TS and the novel HRT index differ significantly in survivors and cardiac death patients, mortality analysis shows that the latter index exhibits much stronger association with risk of cardiac death (hazard ratio = 2.8, CI = 1.32-5.97, p = 0.008). It is also shown that the model-based shape indices, but not TO and TS, remain predictive of cardiac death in our population when computed from 4-h instead of 24-h ambulatory ECGs.
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