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Gomez N, Ramirez J, Martinez JP, Laguna P. Time-Warping Analysis of the T-Wave Peak-to-End Interval to Quantify Ventricular Repolarization Dispersion During Ischemia. IEEE J Biomed Health Inform 2023; 27:5314-5325. [PMID: 37651478 DOI: 10.1109/jbhi.2023.3310878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
Abstract
Variations in the dispersion of ventricular repolarization can be quantified by T-wave time-warping based index, dw. However, the early phase of the T-wave can be affected by ST-segment changes during ischemia. We hypothesized that restricting dw to the T-wave peak-to-end ( Tpe) would circumvent this limitation while still quantifying variations in repolarization dispersion. A total of 101 ECG recordings from patients undergoing coronary occlusion, together with their control recordings, were analyzed. A series of dw values was calculated by quantifying the Tpe morphological variations between the T-waves at different occlusion stages and a baseline T-wave. We introduced a normalized version of dw, Rd, reflecting variations of dw during occlusion relative to control recordings ( Rd = 1 corresponds to the same level of variation). The dw series followed a gradually increasing trend with occlusion time, reaching median [range] Rd values of 9.44 [1.01, 80.74] at the occlusion end. Rd at occlusion end was significantly higher than threshold values of 1, 2, 5, and 10 in 94.1%, 85.11%, 64.4% and 48.5% of patients, respectively. The spatial lead-wise analysis of dw showed distinct distributions depending on the occluded artery, suggesting a relation with the ischemia location. The relative variation R with ischemia of index dw (9.4) is greater than that of the T-wave amplitude (7.7), Tpe interval (2.7) and T-wave width (3.0). In conclusion, dw tracks ischemic-induced variations in repolarization dispersion in a more robust manner than classical indexes, avoiding the impact of ST segment elevation/depression or early T-wave distortions, thus warranting further clinical studies.
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Bukhari HA, Sánchez C, Laguna P, Potse M, Pueyo E. Differences in ventricular wall composition may explain inter-patient variability in the ECG response to variations in serum potassium and calcium. Front Physiol 2023; 14:1060919. [PMID: 37885805 PMCID: PMC10598848 DOI: 10.3389/fphys.2023.1060919] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Accepted: 09/18/2023] [Indexed: 10/28/2023] Open
Abstract
Objective: Chronic kidney disease patients have a decreased ability to maintain normal electrolyte concentrations in their blood, which increases the risk for ventricular arrhythmias and sudden cardiac death. Non-invasive monitoring of serum potassium and calcium concentration, [K+] and [Ca2+], can help to prevent arrhythmias in these patients. Electrocardiogram (ECG) markers that significantly correlate with [K+] and [Ca2+] have been proposed, but these relations are highly variable between patients. We hypothesized that inter-individual differences in cell type distribution across the ventricular wall can help to explain this variability. Methods: A population of human heart-torso models were built with different proportions of endocardial, midmyocardial and epicardial cells. Propagation of ventricular electrical activity was described by a reaction-diffusion model, with modified Ten Tusscher-Panfilov dynamics. [K+] and [Ca2+] were varied individually and in combination. Twelve-lead ECGs were simulated and the width, amplitude and morphological variability of T waves and QRS complexes were quantified. Results were compared to measurements from 29 end-stage renal disease (ESRD) patients undergoing hemodialysis (HD). Results: Both simulations and patients data showed that most of the analyzed T wave and QRS complex markers correlated strongly with [K+] (absolute median Pearson correlation coefficients, r, ranging from 0.68 to 0.98) and [Ca2+] (ranging from 0.70 to 0.98). The same sign and similar magnitude of median r was observed in the simulations and the patients. Different cell type distributions in the ventricular wall led to variability in ECG markers that was accentuated at high [K+] and low [Ca2+], in agreement with the larger variability between patients measured at the onset of HD. The simulated ECG variability explained part of the measured inter-patient variability. Conclusion: Changes in ECG markers were similarly related to [K+] and [Ca2+] variations in our models and in the ESRD patients. The high inter-patient ECG variability may be explained by variations in cell type distribution across the ventricular wall, with high sensitivity to variations in the proportion of epicardial cells. Significance: Differences in ventricular wall composition help to explain inter-patient variability in ECG response to [K+] and [Ca2+]. This finding can be used to improve serum electrolyte monitoring in ESRD patients.
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Affiliation(s)
- Hassaan A. Bukhari
- BSICoS Group, I3A Institute, University of Zaragoza, IIS Aragón, Zaragoza, Spain
- CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Zaragoza, Spain
- Carmen Team, Inria Bordeaux—Sud-Ouest, Talence, France
- University of Bordeaux, IMB, UMR 5251, Talence, France
| | - Carlos Sánchez
- BSICoS Group, I3A Institute, University of Zaragoza, IIS Aragón, Zaragoza, Spain
- CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Zaragoza, Spain
| | - Pablo Laguna
- BSICoS Group, I3A Institute, University of Zaragoza, IIS Aragón, Zaragoza, Spain
- CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Zaragoza, Spain
| | - Mark Potse
- Carmen Team, Inria Bordeaux—Sud-Ouest, Talence, France
- University of Bordeaux, IMB, UMR 5251, Talence, France
- IHU Liryc, Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, Bordeaux, France
| | - Esther Pueyo
- BSICoS Group, I3A Institute, University of Zaragoza, IIS Aragón, Zaragoza, Spain
- CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Zaragoza, Spain
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3
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Ramírez J, Kiviniemi A, van Duijvenboden S, Tinker A, Lambiase PD, Junttila J, Perkiömäki JS, Huikuri HV, Orini M, Munroe PB. ECG T-Wave Morphologic Variations Predict Ventricular Arrhythmic Risk in Low- and Moderate-Risk Populations. J Am Heart Assoc 2022; 11:e025897. [PMID: 36036209 PMCID: PMC9496440 DOI: 10.1161/jaha.121.025897] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background Early identification of individuals at risk of sudden cardiac death (SCD) remains a major challenge. The ECG is a simple, common test, with potential for large-scale application. We developed and tested the predictive value of a novel index quantifying T-wave morphologic variations with respect to a normal reference (TMV), which only requires one beat and a single-lead ECG. Methods and Results We obtained reference T-wave morphologies from 23 962 participants in the UK Biobank study. With Cox models, we determined the association between TMV and life-threatening ventricular arrhythmia in an independent data set from UK Biobank study without a history of cardiovascular events (N=51 794; median follow-up of 122 months) and SCD in patients with coronary artery disease from ARTEMIS (N=1872; median follow-up of 60 months). In UK Biobank study, 220 (0.4%) individuals developed life-threatening ventricular arrhythmias. TMV was significantly associated with life-threatening ventricular arrhythmias (hazard ratio [HR] of 1.13 per SD increase [95% CI, 1.03-1.24]; P=0.009). In ARTEMIS, 34 (1.8%) individuals reached the primary end point. Patients with TMV ≥5 had an HR for SCD of 2.86 (95% CI, 1.40-5.84; P=0.004) with respect to those with TMV <5, independently from QRS duration, corrected QT interval, and left ventricular ejection fraction. TMV was not significantly associated with death from a cause other than SCD. Conclusions TMV identifies individuals at life-threatening ventricular arrhythmia and SCD risk using a single-beat single-lead ECG, enabling inexpensive, quick, and safe risk assessment in large populations.
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Affiliation(s)
- Julia Ramírez
- Clinical Pharmacology and Precision Medicine William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London London United Kingdom.,Aragon Institute of Engineering Research University of Zaragoza Zaragoza Spain.,Centro de Investigación Biomédica en Red - Bioingeniería, Biomateriales y Nanomedicina Zaragoza Spain
| | - Antti Kiviniemi
- Research Unit of Internal Medicine Medical Research Center Oulu, University of Oulu and Oulu University Hospital Oulu Finland
| | - Stefan van Duijvenboden
- Clinical Pharmacology and Precision Medicine William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London London United Kingdom.,Institute of Cardiovascular Science University College London London United Kingdom
| | - Andrew Tinker
- Clinical Pharmacology and Precision Medicine William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London London United Kingdom.,National Institute for Health and Care Research Barts Cardiovascular Biomedical Research Centre Barts and The London School of Medicine and Dentistry, Queen Mary University of London London United Kingdom
| | - Pier D Lambiase
- Institute of Cardiovascular Science University College London London United Kingdom.,Barts Heart Centre St Bartholomew's Hospital London United Kingdom
| | - Juhani Junttila
- Research Unit of Internal Medicine Medical Research Center Oulu, University of Oulu and Oulu University Hospital Oulu Finland
| | - Juha S Perkiömäki
- Research Unit of Internal Medicine Medical Research Center Oulu, University of Oulu and Oulu University Hospital Oulu Finland
| | - Heikki V Huikuri
- Research Unit of Internal Medicine Medical Research Center Oulu, University of Oulu and Oulu University Hospital Oulu Finland
| | - Michele Orini
- Institute of Cardiovascular Science University College London London United Kingdom.,Barts Heart Centre St Bartholomew's Hospital London United Kingdom
| | - Patricia B Munroe
- Clinical Pharmacology and Precision Medicine William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London London United Kingdom.,National Institute for Health and Care Research Barts Cardiovascular Biomedical Research Centre Barts and The London School of Medicine and Dentistry, Queen Mary University of London London United Kingdom
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Bukhari HA, Sánchez C, Ruiz JE, Potse M, Laguna P, Pueyo E. Monitoring of Serum Potassium and Calcium Levels in End-Stage Renal Disease Patients by ECG Depolarization Morphology Analysis. SENSORS 2022; 22:s22082951. [PMID: 35458934 PMCID: PMC9027214 DOI: 10.3390/s22082951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 04/05/2022] [Accepted: 04/07/2022] [Indexed: 11/16/2022]
Abstract
Objective: Non-invasive estimation of serum potassium, [K+], and calcium, [Ca2+], can help to prevent life-threatening ventricular arrhythmias in patients with advanced renal disease, but current methods for estimation of electrolyte levels have limitations. We aimed to develop new markers based on the morphology of the QRS complex of the electrocardiogram (ECG). Methods: ECG recordings from 29 patients undergoing hemodialysis (HD) were processed. Mean warped QRS complexes were computed in two-minute windows at the start of an HD session, at the end of each HD hour and 48 h after it. We quantified QRS width, amplitude and the proposed QRS morphology-based markers that were computed by warping techniques. Reference [K+] and [Ca2+] were determined from blood samples acquired at the time points where the markers were estimated. Linear regression models were used to estimate electrolyte levels from the QRS markers individually and in combination with T wave morphology markers. Leave-one-out cross-validation was used to assess the performance of the estimators. Results: All markers, except for QRS width, strongly correlated with [K+] (median Pearson correlation coefficients, r, ranging from 0.81 to 0.87) and with [Ca2+] (r ranging from 0.61 to 0.76). QRS morphology markers showed very low sensitivity to heart rate (HR). Actual and estimated serum electrolyte levels differed, on average, by less than 0.035 mM (relative error of 0.018) for [K+] and 0.010 mM (relative error of 0.004) for [Ca2+] when patient-specific multivariable estimators combining QRS and T wave markers were used. Conclusion: QRS morphological markers allow non-invasive estimation of [K+] and [Ca2+] with low sensitivity to HR. The estimation performance is improved when multivariable models, including T wave markers, are considered. Significance: Markers based on the QRS complex of the ECG could contribute to non-invasive monitoring of serum electrolyte levels and arrhythmia risk prediction in patients with renal disease.
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Affiliation(s)
- Hassaan A. Bukhari
- BSICoS Group, I3A Institute, IIS Aragón, University of Zaragoza, 50018 Zaragoza, Spain; (C.S.); (P.L.); (E.P.)
- CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), 50018 Zaragoza, Spain
- Carmen Team, Inria Bordeaux—Sud-Ouest, 33405 Talence, France;
- Université de Bordeaux, IMB, UMR 5251, 33400 Talence, France
- Correspondence:
| | - Carlos Sánchez
- BSICoS Group, I3A Institute, IIS Aragón, University of Zaragoza, 50018 Zaragoza, Spain; (C.S.); (P.L.); (E.P.)
- CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), 50018 Zaragoza, Spain
| | - José Esteban Ruiz
- Nephrology Department, Hospital Clínico Universitario Lozano Blesa, 50009 Zaragoza, Spain;
| | - Mark Potse
- Carmen Team, Inria Bordeaux—Sud-Ouest, 33405 Talence, France;
- Université de Bordeaux, IMB, UMR 5251, 33400 Talence, France
| | - Pablo Laguna
- BSICoS Group, I3A Institute, IIS Aragón, University of Zaragoza, 50018 Zaragoza, Spain; (C.S.); (P.L.); (E.P.)
- CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), 50018 Zaragoza, Spain
| | - Esther Pueyo
- BSICoS Group, I3A Institute, IIS Aragón, University of Zaragoza, 50018 Zaragoza, Spain; (C.S.); (P.L.); (E.P.)
- CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), 50018 Zaragoza, Spain
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5
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Bukhari HA, Sánchez C, Srinivasan S, Palmieri F, Potse M, Laguna P, Pueyo E. Estimation of potassium levels in hemodialysis patients by T wave nonlinear dynamics and morphology markers. Comput Biol Med 2022; 143:105304. [PMID: 35168084 DOI: 10.1016/j.compbiomed.2022.105304] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Revised: 02/01/2022] [Accepted: 02/05/2022] [Indexed: 12/11/2022]
Abstract
OBJECTIVE Noninvasive screening of hypo- and hyperkalemia can prevent fatal arrhythmia in end-stage renal disease (ESRD) patients, but current methods for monitoring of serum potassium (K+) have important limitations. We investigated changes in nonlinear dynamics and morphology of the T wave in the electrocardiogram (ECG) of ESRD patients during hemodialysis (HD), assessing their relationship with K+ and designing a K+ estimator. METHODS ECG recordings from twenty-nine ESRD patients undergoing HD were processed. T waves in 2-min windows were extracted at each hour during an HD session as well as at 48 h after HD start. T wave nonlinear dynamics were characterized by two indices related to the maximum Lyapunov exponent (λt, λwt) and a divergence-related index (η). Morphological variability in the T wave was evaluated by three time warping-based indices (dw, reflecting morphological variability in the time domain, and da and daNL, in the amplitude domain). K+was measured from blood samples extracted during and after HD. Stage-specific and patient-specific K+ estimators were built based on the quantified indices and leave-one-out cross-validation was performed separately for each of the estimators. RESULTS The analyzed indices showed high inter-individual variability in their relationship with K+. Nevertheless, all of them had higher values at the HD start and 48 h after it, corresponding to the highest K+. The indices η and dw were the most strongly correlated with K+ (median Pearson correlation coefficient of 0.78 and 0.83, respectively) and were used in univariable and multivariable linear K+ estimators. Agreement between actual and estimated K+ was confirmed, with averaged errors over patients and time points being 0.000 ± 0.875 mM and 0.046 ± 0.690 mM for stage-specific and patient-specific multivariable K+ estimators, respectively. CONCLUSION ECG descriptors of T wave nonlinear dynamics and morphological variability allow noninvasive monitoring of K+ in ESRD patients. SIGNIFICANCE ECG markers have the potential to be used for hypo- and hyperkalemia screening in ESRD patients.
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Affiliation(s)
- Hassaan A Bukhari
- BSICoS group, I3A Institute, University of Zaragoza, IIS Aragón, Zaragoza, Spain; CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Zaragoza, Spain; Carmen team, Inria Bordeaux - Sud-Ouest, Talence, France; University of Bordeaux, IMB, UMR 5251, Talence, France.
| | - Carlos Sánchez
- BSICoS group, I3A Institute, University of Zaragoza, IIS Aragón, Zaragoza, Spain; CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Zaragoza, Spain
| | - Sabarathinam Srinivasan
- BSICoS group, I3A Institute, University of Zaragoza, IIS Aragón, Zaragoza, Spain; CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Zaragoza, Spain
| | - Flavio Palmieri
- CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Zaragoza, Spain; Centre de Recerca en Enginyeria Biomèdica, Universitat Politècnica de Catalunya, Barcelona, Spain
| | - Mark Potse
- Carmen team, Inria Bordeaux - Sud-Ouest, Talence, France; University of Bordeaux, IMB, UMR 5251, Talence, France
| | - Pablo Laguna
- BSICoS group, I3A Institute, University of Zaragoza, IIS Aragón, Zaragoza, Spain; CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Zaragoza, Spain
| | - Esther Pueyo
- BSICoS group, I3A Institute, University of Zaragoza, IIS Aragón, Zaragoza, Spain; CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Zaragoza, Spain
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Palmieri F, Gomis P, Ferreira D, Pueyo E, Martinez JP, Laguna P, Ramirez J. Weighted Time Warping Improves T-wave Morphology Markers Clinical Significance. IEEE Trans Biomed Eng 2022; 69:2787-2796. [PMID: 35196223 DOI: 10.1109/tbme.2022.3153791] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Background: T-wave (TW) morphology indices based on time-warping (dw) have shown significant cardiovascular risk stratification value. However, errors in the location of TW boundaries may impact their prognostic power. Our aim was to test the hypothesis that a weighted time-warping function (WF) would reduce the sensitivity of dw to these errors and improve their clinical significance. Methods: The WFs were proportional to (i) the reference TW (T), and (ii) the absolute value of its derivative (D). The index dw was recalculated using these WFs, and its performance was compared to the unweighted control case (C) in four different scenarios: 1) robustness against simulated TW boundaries location errors; 2) ability to retain physiological information in an electrophysiological cardiac model; 3) ability to monitor blood potassium concentration changes ([K+]) in 29 hemodialysis (HD) patients; 4) and the sudden cardiac death (SCD) risk stratification value of the TW morphology restitution (TMR) index, derived from dw, in 651 chronic heart failure (CHF) patients. Results and Discussion: The WFs led to a reduced sensitivity (R) of dw to TW boundary location errors as compared to C (median R=0.19 and 0.22 and 0.35 for T, D and C, respectively). They also preserved the physiological relationship between dw and repolarization dispersion changes at ventricular level. No improvements in [K+] tracking were observed for the HD patients (Pearsons median correlation [r] between [K+] and dw was 0.86r0.90 for T, D and C). In CHF patients, the SCD risk stratification value of TMR was improved by applying T (hazard ratio, HAR, of 2.80), followed by D (HAR=2.32) and C (HAR=2.23). Conclusions and Significance: The proposed WFs, with T showing the best performance, increased the robustness of time-warping based markers against TW location errors preserving their physiological information content and boosting their SCD risk stratification value. Results from this work support the use of T when deriving dw for future clinical applications.
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Palmieri F, Gomis P, Ruiz JE, Ferreira D, Martín-Yebra A, Pueyo E, Martínez JP, Ramírez J, Laguna P. ECG-based monitoring of blood potassium concentration: Periodic versus principal component as lead transformation for biomarker robustness. Biomed Signal Process Control 2021. [DOI: 10.1016/j.bspc.2021.102719] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Camps J, Lawson B, Drovandi C, Minchole A, Wang ZJ, Grau V, Burrage K, Rodriguez B. Inference of ventricular activation properties from non-invasive electrocardiography. Med Image Anal 2021; 73:102143. [PMID: 34271532 PMCID: PMC8505755 DOI: 10.1016/j.media.2021.102143] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 06/17/2021] [Accepted: 06/18/2021] [Indexed: 12/13/2022]
Abstract
The realisation of precision cardiology requires novel techniques for the non-invasive characterisation of individual patients’ cardiac function to inform therapeutic and diagnostic decision-making. Both electrocardiography and imaging are used for the clinical diagnosis of cardiac disease. The integration of multi-modal datasets through advanced computational methods could enable the development of the cardiac ‘digital twin’, a comprehensive virtual tool that mechanistically reveals a patient's heart condition from clinical data and simulates treatment outcomes. The adoption of cardiac digital twins requires the non-invasive efficient personalisation of the electrophysiological properties in cardiac models. This study develops new computational techniques to estimate key ventricular activation properties for individual subjects by exploiting the synergy between non-invasive electrocardiography, cardiac magnetic resonance (CMR) imaging and modelling and simulation. More precisely, we present an efficient sequential Monte Carlo approximate Bayesian computation-based inference method, integrated with Eikonal simulations and torso-biventricular models constructed based on clinical CMR imaging. The method also includes a novel strategy to treat combined continuous (conduction speeds) and discrete (earliest activation sites) parameter spaces and an efficient dynamic time warping-based ECG comparison algorithm. We demonstrate results from our inference method on a cohort of twenty virtual subjects with cardiac ventricular myocardial-mass volumes ranging from 74 cm3 to 171 cm3 and considering low versus high resolution for the endocardial discretisation (which determines possible locations of the earliest activation sites). Results show that our method can successfully infer the ventricular activation properties in sinus rhythm from non-invasive epicardial activation time maps and ECG recordings, achieving higher accuracy for the endocardial speed and sheet (transmural) speed than for the fibre or sheet-normal directed speeds. Estimation of the ventricular speeds and earliest activation sites from ECG and CMR. Evaluation with twenty virtual subjects shows the effect of anatomical variability. Bayesian-inspired simultaneous estimation of continuous and discrete parameters. Efficient dynamic time warping-based comparison of electrocardiograms (ECG). Changing fibre and sheet-normal speed does not affect healthy activation sequence.
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Affiliation(s)
- Julia Camps
- Department of Computer Science, University of Oxford, Oxford, United Kingdom.
| | - Brodie Lawson
- Australian Research Council Centre of Excellence for Mathematical and Statistical Frontiers (ACEMS), Queensland University of Technology (QUT), Brisbane, Australia; QUT Centre for Data Science (CDS), Queensland University of Technology, Brisbane, Australia
| | - Christopher Drovandi
- Australian Research Council Centre of Excellence for Mathematical and Statistical Frontiers (ACEMS), Queensland University of Technology (QUT), Brisbane, Australia; QUT Centre for Data Science (CDS), Queensland University of Technology, Brisbane, Australia
| | - Ana Minchole
- Department of Computer Science, University of Oxford, Oxford, United Kingdom
| | - Zhinuo Jenny Wang
- Department of Computer Science, University of Oxford, Oxford, United Kingdom
| | - Vicente Grau
- Institute of Biomedical Engineering (IBME), University of Oxford, Oxford, United Kingdom
| | - Kevin Burrage
- Department of Computer Science, University of Oxford, Oxford, United Kingdom; Australian Research Council Centre of Excellence for Mathematical and Statistical Frontiers (ACEMS), Queensland University of Technology (QUT), Brisbane, Australia
| | - Blanca Rodriguez
- Department of Computer Science, University of Oxford, Oxford, United Kingdom
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Ramírez J, van Duijvenboden S, Young WJ, Orini M, Jones AR, Lambiase PD, Munroe PB, Tinker A. Analysing electrocardiographic traits and predicting cardiac risk in UK biobank. JRSM Cardiovasc Dis 2021; 10:20480040211023664. [PMID: 34211707 PMCID: PMC8202245 DOI: 10.1177/20480040211023664] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 05/04/2021] [Accepted: 05/19/2021] [Indexed: 11/16/2022] Open
Abstract
The electrocardiogram (ECG) is a commonly used clinical tool that reflects cardiac excitability and disease. Many parameters are can be measured and with the improvement of methodology can now be quantified in an automated fashion, with accuracy and at scale. Furthermore, these measurements can be heritable and thus genome wide association studies inform the underpinning biological mechanisms. In this review we describe how we have used the resources in UK Biobank to undertake such work. In particular, we focus on a substudy uniquely describing the response to exercise performed at scale with accompanying genetic information.
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Affiliation(s)
- Julia Ramírez
- Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK.,Institute of Cardiovascular Science, University College London, London, UK
| | - Stefan van Duijvenboden
- Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK.,Institute of Cardiovascular Science, University College London, London, UK
| | - William J Young
- Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK.,Barts Heart Centre, St Bartholomew's Hospital, London, UK
| | - Michele Orini
- Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK.,Institute of Cardiovascular Science, University College London, London, UK.,Barts Heart Centre, St Bartholomew's Hospital, London, UK
| | - Aled R Jones
- Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Pier D Lambiase
- Institute of Cardiovascular Science, University College London, London, UK.,Barts Heart Centre, St Bartholomew's Hospital, London, UK
| | - Patricia B Munroe
- Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK.,NIHR Barts Cardiovascular Biomedical Research Unit, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Andrew Tinker
- Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK.,NIHR Barts Cardiovascular Biomedical Research Unit, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
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10
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Palmieri F, Gomis P, Ruiz JE, Ferreira D, Martín-Yebra A, Pueyo E, Martínez JP, Ramírez J, Laguna P. Nonlinear T-Wave Time Warping-Based Sensing Model for Non-Invasive Personalised Blood Potassium Monitoring in Hemodialysis Patients: A Pilot Study. SENSORS 2021; 21:s21082710. [PMID: 33921468 PMCID: PMC8069025 DOI: 10.3390/s21082710] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 03/16/2021] [Accepted: 03/30/2021] [Indexed: 11/24/2022]
Abstract
Background: End-stage renal disease patients undergoing hemodialysis (ESRD-HD) therapy are highly susceptible to malignant ventricular arrhythmias caused by undetected potassium concentration ([K+]) variations (Δ[K+]) out of normal ranges. Therefore, a reliable method for continuous, noninvasive monitoring of [K+] is crucial. The morphology of the T-wave in the electrocardiogram (ECG) reflects Δ[K+] and two time-warping-based T-wave morphological parameters, dw and its heart-rate corrected version dw,c, have been shown to reliably track Δ[K+] from the ECG. The aim of this study is to derive polynomial models relating dw and dw,c with Δ[K+], and to test their ability to reliably sense and quantify Δ[K+] values. Methods: 48-hour Holter ECGs and [K+] values from six blood samples were collected from 29 ESRD-HD patients. For every patient, dw and dw,c were computed, and linear, quadratic, and cubic fitting models were derived from them. Then, Spearman’s (ρ) and Pearson’s (r) correlation coefficients, and the estimation error (ed) between Δ[K+] and the corresponding model-estimated values (Δ^[K+]) were calculated. Results and Discussions: Nonlinear models were the most suitable for Δ[K+] estimation, rendering higher Pearson’s correlation (median 0.77 ≤r≤ 0.92) and smaller estimation error (median 0.20 ≤ed≤ 0.43) than the linear model (median 0.76 ≤r≤ 0.86 and 0.30 ≤ed≤ 0.40), even if similar Spearman’s ρ were found across models (median 0.77 ≤ρ≤ 0.83). Conclusion: Results support the use of nonlinear T-wave-based models as Δ[K+] sensors in ESRD-HD patients.
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Affiliation(s)
- Flavio Palmieri
- Centre de Recerca en Enginyeria Biomèdica, Universitat Politècnica de Catalunya, 08028 Barcelona, Spain; (F.P.); (P.G.)
- CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), 50018 Zaragoza, Spain; (A.M.-Y.); (E.P.); (J.P.M.)
- Laboratorios Rubió, Castellbisbal, 08755 Barcelona, Spain;
| | - Pedro Gomis
- Centre de Recerca en Enginyeria Biomèdica, Universitat Politècnica de Catalunya, 08028 Barcelona, Spain; (F.P.); (P.G.)
- Escuela Superior de Ingeniería, Ciencia y Tecnología, Universidad Internacional de Valencia, 46002 Valencia, Spain
| | - José Esteban Ruiz
- Nephrology Ward, Hospital Clínico Universitario Lozano Blesa, 50009 Zaragoza, Spain;
| | - Dina Ferreira
- Laboratorios Rubió, Castellbisbal, 08755 Barcelona, Spain;
| | - Alba Martín-Yebra
- CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), 50018 Zaragoza, Spain; (A.M.-Y.); (E.P.); (J.P.M.)
- BSICoS Group, I3A, IIS Aragón, Universidad de Zaragoza, 50018 Zaragoza, Spain
| | - Esther Pueyo
- CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), 50018 Zaragoza, Spain; (A.M.-Y.); (E.P.); (J.P.M.)
- BSICoS Group, I3A, IIS Aragón, Universidad de Zaragoza, 50018 Zaragoza, Spain
| | - Juan Pablo Martínez
- CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), 50018 Zaragoza, Spain; (A.M.-Y.); (E.P.); (J.P.M.)
- BSICoS Group, I3A, IIS Aragón, Universidad de Zaragoza, 50018 Zaragoza, Spain
| | - Julia Ramírez
- William Harvey Research Institute, Queen Mary University of London, London E1 4NS, UK;
| | - Pablo Laguna
- CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), 50018 Zaragoza, Spain; (A.M.-Y.); (E.P.); (J.P.M.)
- BSICoS Group, I3A, IIS Aragón, Universidad de Zaragoza, 50018 Zaragoza, Spain
- Correspondence:
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11
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Palmieri F, Gomis P, Ferreira D, Ruiz JE, Bergasa B, Martín-Yebra A, Bukhari HA, Pueyo E, Martínez JP, Ramírez J, Laguna P. Monitoring blood potassium concentration in hemodialysis patients by quantifying T-wave morphology dynamics. Sci Rep 2021; 11:3883. [PMID: 33594135 PMCID: PMC7887245 DOI: 10.1038/s41598-021-82935-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 01/27/2021] [Indexed: 12/29/2022] Open
Abstract
We investigated the ability of time-warping-based ECG-derived markers of T-wave morphology changes in time (\documentclass[12pt]{minimal}
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\begin{document}$$d_{w}$$\end{document}dw) and amplitude (\documentclass[12pt]{minimal}
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\begin{document}$$d_a$$\end{document}da), as well as their non-linear components (\documentclass[12pt]{minimal}
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\begin{document}$${d_w^{{\mathrm{NL}}}}$$\end{document}dwNL and \documentclass[12pt]{minimal}
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\begin{document}$${d_a^{\mathrm{NL}}}$$\end{document}daNL), and the heart rate corrected counterpart (\documentclass[12pt]{minimal}
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\begin{document}$$d_{w,c}$$\end{document}dw,c), to monitor potassium concentration (\documentclass[12pt]{minimal}
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\begin{document}$$[K^{+}]$$\end{document}[K+]) changes (\documentclass[12pt]{minimal}
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\begin{document}$$\Delta [K^+]$$\end{document}Δ[K+]) in end-stage renal disease (ESRD) patients undergoing hemodialysis (HD). We compared the performance of the proposed time-warping markers, together with other previously proposed \documentclass[12pt]{minimal}
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\begin{document}$$[K^{+}]$$\end{document}[K+] markers, such as T-wave width (\documentclass[12pt]{minimal}
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\begin{document}$$T_w$$\end{document}Tw) and T-wave slope-to-amplitude ratio (\documentclass[12pt]{minimal}
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\begin{document}$$T_{S/A}$$\end{document}TS/A), when computed from standard ECG leads as well as from principal component analysis (PCA)-based leads. 48-hour ECG recordings and a set of hourly-collected blood samples from 29 ESRD-HD patients were acquired. Values of \documentclass[12pt]{minimal}
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\begin{document}$${d_w^{\mathrm{NL}}}$$\end{document}dwNL, \documentclass[12pt]{minimal}
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\begin{document}$${d_a^{\mathrm{NL}}}$$\end{document}daNL and \documentclass[12pt]{minimal}
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\begin{document}$$d_{w,c}$$\end{document}dw,c were calculated by comparing the morphology of the mean warped T-waves (MWTWs) derived at each hour along the HD with that from a reference MWTW, measured at the end of the HD. From the same MWTWs \documentclass[12pt]{minimal}
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\begin{document}$$T_w$$\end{document}Tw and \documentclass[12pt]{minimal}
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\begin{document}$$T_{S/A}$$\end{document}TS/A were also extracted. Similarly, \documentclass[12pt]{minimal}
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\begin{document}$$\Delta [K^+]$$\end{document}Δ[K+] was calculated as the difference between the \documentclass[12pt]{minimal}
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\begin{document}$$[K^{+}]$$\end{document}[K+] values at each hour and the \documentclass[12pt]{minimal}
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\begin{document}$$[K^{+}]$$\end{document}[K+] reference level at the end of the HD session. We found that \documentclass[12pt]{minimal}
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\begin{document}$$d_{w}$$\end{document}dw and \documentclass[12pt]{minimal}
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\begin{document}$$d_{w,c}$$\end{document}dw,c showed higher correlation coefficients with \documentclass[12pt]{minimal}
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\begin{document}$$\Delta [K^+]$$\end{document}Δ[K+] than \documentclass[12pt]{minimal}
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\begin{document}$$T_{S/A}$$\end{document}TS/A—Spearman’s (\documentclass[12pt]{minimal}
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\begin{document}$$\rho$$\end{document}ρ) and Pearson’s (r)—and \documentclass[12pt]{minimal}
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\begin{document}$$T_w$$\end{document}Tw—Spearman’s (\documentclass[12pt]{minimal}
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\begin{document}$$\rho$$\end{document}ρ)—in both SL and PCA approaches being the intra-patient median \documentclass[12pt]{minimal}
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\begin{document}$$\rho \ge 0.82$$\end{document}ρ≥0.82 and \documentclass[12pt]{minimal}
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\begin{document}$$r \ge 0.87$$\end{document}r≥0.87 in SL and \documentclass[12pt]{minimal}
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\begin{document}$$r \ge 0.89$$\end{document}r≥0.89 in PCA respectively. Our findings would point at \documentclass[12pt]{minimal}
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\begin{document}$$d_{w,c}$$\end{document}dw,c as the most suitable surrogate of \documentclass[12pt]{minimal}
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\begin{document}$$\Delta [K^+]$$\end{document}Δ[K+], suggesting that they could be potentially useful for non-invasive monitoring of ESRD-HD patients in hospital, as well as in ambulatory settings. Therefore, the tracking of T-wave morphology variations by means of time-warping analysis could improve continuous and remote \documentclass[12pt]{minimal}
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\begin{document}$$[K^{+}]$$\end{document}[K+] monitoring of ESRD-HD patients and flagging risk of \documentclass[12pt]{minimal}
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\begin{document}$$[K^{+}]$$\end{document}[K+]-related cardiovascular events.
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Affiliation(s)
- Flavio Palmieri
- Centre de Recerca en Enginyeria Biomèdica, Universitat Politècnica de Catalunya, Barcelona, Spain. .,CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Zaragoza, Spain. .,Laboratorios Rubió, Castellbisbal, Barcelona, Spain.
| | - Pedro Gomis
- Centre de Recerca en Enginyeria Biomèdica, Universitat Politècnica de Catalunya, Barcelona, Spain.,Valencian International University, Valencia, Spain
| | | | - José Esteban Ruiz
- Nephrology Department, Hospital Clínico Universitario Lozano Blesa, Zaragoza, Spain
| | - Beatriz Bergasa
- Nephrology Department, Hospital Clínico Universitario Lozano Blesa, Zaragoza, Spain
| | - Alba Martín-Yebra
- CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Zaragoza, Spain.,BSICoS Group, I3A, IIS Aragón, Universidad de Zaragoza, Zaragoza, Spain
| | - Hassaan A Bukhari
- CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Zaragoza, Spain.,BSICoS Group, I3A, IIS Aragón, Universidad de Zaragoza, Zaragoza, Spain
| | - Esther Pueyo
- CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Zaragoza, Spain.,BSICoS Group, I3A, IIS Aragón, Universidad de Zaragoza, Zaragoza, Spain
| | - Juan Pablo Martínez
- CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Zaragoza, Spain.,BSICoS Group, I3A, IIS Aragón, Universidad de Zaragoza, Zaragoza, Spain
| | - Julia Ramírez
- William Harvey Research Institute, Queen Mary University of London, London, UK
| | - Pablo Laguna
- CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Zaragoza, Spain.,BSICoS Group, I3A, IIS Aragón, Universidad de Zaragoza, Zaragoza, Spain
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Sadiq I, Perez-Alday EA, Shah AJ, Clifford GD. Breathing rate and heart rate as confounding factors in measuring T wave alternans and morphological variability in ECG. Physiol Meas 2021; 42:015002. [PMID: 33296886 DOI: 10.1088/1361-6579/abd237] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE High morphological variability magnitude (MVM) and microvolt T wave alternans (TWA) within an electrocardiogram (ECG) signifies increased electrical instability and risk of sudden cardiac death. However, the influence of breathing rate (BR), heart rate (HR), and signal-to-noise ratio (SNR) is unknown and may inflate measured values. APPROACH We synthesize ECGs with morphologies derived from the Physikalisch-Technische Bundesanstalt Database. We calculate MVM and TWA at varying BRs, HRs and SNRs. We compare the MVM and TWA of signal with versus without breathing at varying HRs and SNRs. We then quantify the percentage of MVM and TWA estimates affected by BR and HR in a healthy population and assess the effect of removing these affected estimates on a method for classifying individuals with and without post-traumatic stress disorder (PTSD). MAIN RESULTS For signals with high SNR (>15 dB), MVM is significantly increased when BRs are > 9 respirations/minute (rpm) and HRs are < 100 beats/minute (bpm). Increased TWAs are detected for HR/BR pairs of 60/15, 60/30 and 120/30 bpm/rpm. For 18 healthy participants, 8.33% of TWA windows and 66.76% of MVM windows are affected by BR and HR. On average, the number of windows with TWA elevations > 47 μV decreases by 23% after excluding regions with significant BR and HR effect. Adding HR and BR to a morphological variability feature increases the classification performance by 6% for individuals with and without PTSD. SIGNIFICANCE Physiological BR and HR significantly increase MVM and TWA , indicating that BR and HR should be considered separately as confounders. The code for this work has been released as part of an open-source toolbox.
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Affiliation(s)
- Ismail Sadiq
- Department of Electrical & Computer Engineering, Georgia Institute of Technology, Atlanta, GA, United States of America
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13
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Young WJ, van Duijvenboden S, Ramírez J, Jones A, Tinker A, Munroe PB, Lambiase PD, Orini M. A Method to Minimise the Impact of ECG Marker Inaccuracies on the Spatial QRS-T angle: Evaluation on 1,512 Manually Annotated ECGs. Biomed Signal Process Control 2021; 64:102305. [PMID: 33537064 PMCID: PMC7762839 DOI: 10.1016/j.bspc.2020.102305] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Inaccuracies of QRS and T-wave markers significantly impact QRS-Ta estimation. These errors influence the classification of clinically relevant abnormal values. Our algorithm provides robust measurements in the presence of inaccurate VCG markers. We present for the first time, the distribution of the QRS-Ta in a large cohort.
The spatial QRS-T angle (QRS-Ta) derived from the vectorcardiogram (VCG) is a strong risk predictor for ventricular arrhythmia and sudden cardiac death with potential use for mass screening. Accurate QRS-Ta estimation in the presence of ECG delineation errors is crucial for its deployment as a prognostic test. Our study assessed the effect of inaccurate QRS and T-wave marker placement on QRS-Ta estimation and proposes a robust method for its calculation. Reference QRS-Ta measurements were derived from 1,512 VCGs manually annotated by three expert reviewers. We systematically changed onset and offset timings of QRS and T-wave markers to simulate inaccurate placement. The QRS-Ta was recalculated using a standard approach and our proposed algorithm, which limits the impact of VCG marker inaccuracies by defining the vector origin as an interval preceding QRS-onset and redefines the beginning and end of QRS and T-wave loops. Using the standard approach, mean absolute errors (MAE) in peak QRS-Ta were >40% and sensitivity and precision in the detection of abnormality (>105°) were <80% and <65% respectively, when QRS-onset was delayed or QRS-offset anticipated >15 ms. Using our proposed algorithm, MAE for peak QRS-Ta were reduced to <4% and sensitivity and precision of abnormality were >94% for inaccuracies up to ±15 ms. Similar results were obtained for mean QRS-Ta. In conclusion, inaccuracies of QRS and T-wave markers can significantly influence the QRS-Ta. Our proposed algorithm provides robust QRS-Ta measurements in the presence of inaccurate VCG annotation, enabling its use in large datasets.
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Affiliation(s)
- William J Young
- Clinical Pharmacology Department, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, EC1M 6BQ, United Kingdom.,Barts Heart Centre, St Bartholomew's Hospital, Barts Health NHS trust, London, EC1A 7BE, United Kingdom
| | - Stefan van Duijvenboden
- Clinical Pharmacology Department, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, EC1M 6BQ, United Kingdom.,Institute of Cardiovascular Sciences, University of College London, WC1E 6BT, United Kingdom
| | - Julia Ramírez
- Clinical Pharmacology Department, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, EC1M 6BQ, United Kingdom.,Institute of Cardiovascular Sciences, University of College London, WC1E 6BT, United Kingdom
| | - Aled Jones
- Clinical Pharmacology Department, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, EC1M 6BQ, United Kingdom
| | - Andrew Tinker
- Clinical Pharmacology Department, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, EC1M 6BQ, United Kingdom
| | - Patricia B Munroe
- Clinical Pharmacology Department, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, EC1M 6BQ, United Kingdom
| | - Pier D Lambiase
- Institute of Cardiovascular Sciences, University of College London, WC1E 6BT, United Kingdom.,Barts Heart Centre, St Bartholomew's Hospital, Barts Health NHS trust, London, EC1A 7BE, United Kingdom
| | - Michele Orini
- Institute of Cardiovascular Sciences, University of College London, WC1E 6BT, United Kingdom.,Barts Heart Centre, St Bartholomew's Hospital, Barts Health NHS trust, London, EC1A 7BE, United Kingdom
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Bukhari HA, Palmieri F, Ramirez J, Laguna P, Ruiz JE, Ferreira D, Potse M, Sanchez C, Pueyo E. Characterization of T Wave Amplitude, Duration and Morphology Changes During Hemodialysis: Relationship With Serum Electrolyte Levels and Heart Rate. IEEE Trans Biomed Eng 2020; 68:2467-2478. [PMID: 33301399 DOI: 10.1109/tbme.2020.3043844] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE Chronic kidney disease affects more than 10% of the world population. Changes in serum ion concentrations increase the risk for ventricular arrhythmias and sudden cardiac death, particularly in end-stage renal disease (ESRD) patients. We characterized how T wave amplitude, duration and morphology descriptors change with variations in serum levels of potassium and calcium and in heart rate, both in ESRD patients and in simulated ventricular fibers. METHODS Electrocardiogram (ECG) recordings from twenty ESRD patients undergoing hemodialysis (HD) and pseudo-ECGs (pECGs) calculated from twenty-two simulated ventricular fibers at varying transmural heterogeneity levels were processed to quantify T wave width ( Tw), T wave slope-to-amplitude ratio ([Formula: see text]) and four indices of T wave morphological variability based on time warping ( dw, [Formula: see text], da and [Formula: see text]). Serum potassium and calcium levels and heart rate were measured along HD. RESULTS [Formula: see text] was the marker most strongly correlated with serum potassium, dw with calcium and da with heart rate, after correction for covariates. Median values of partial correlation coefficients were 0.75, -0.74 and -0.90, respectively. For all analyzed T wave descriptors, high inter-patient variability was observed in the pattern of such relationships. This variability, accentuated during the first HD time points, was reproduced in the simulations and shown to be influenced by differences in transmural heterogeneity. CONCLUSION Changes in serum potassium and calcium levels and in heart rate strongly affect T wave descriptors, particularly those quantifying morphological variability. SIGNIFICANCE ECG markers have the potential to be used for monitoring serum ion concentrations in ESRD patients.
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Romero D, Jane R. Hypoxia-induced Effects on ECG Depolarization by Time Warping Analysis during Recurrent Obstructive Apnea. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2020:2626-2629. [PMID: 33018545 DOI: 10.1109/embc44109.2020.9176409] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In this work, we evaluated a non-linear approach to estimate morphological variations in ECG depolarization, in the context of intermittent hypoxia (IH). Obstructive apnea sequences were provoked for 15 minutes in anesthetized Sprague-Dawley rats, alternating with equal periods of normal breathing, in a recurrent obstructive sleep apnea (OSA) model. Each apnea episode lasted 15 s, while the frequency used for each sequence was randomly selected. Average heartbeats obtained before the start and at the end of each episode, were delineated to extract only the QRS wave. Then, the segmented QRS waves were non-linearly aligned using the dynamic time warping (DWT) algorithm. Morphological QRS changes in both the amplitude and temporal domains were estimated from this alignment procedure. The hypoxic and basal segments were analyzed using ECG (lead I) recordings acquired during the experiment. To assess the effects of IH over time, the changes relative to the basal QRS wave were determined, in the intervals prior to each successive events until the end of the experiment. The results showed a progressive increase in the amplitude and time-domain morphological markers of the QRS wave along the experiment, which were strongly correlated with the changes in traditional QRS markers (r ≈ 0.9). Significant changes were found between pre-apnea and hypoxic measures only for the time-domain analysis (p<0.001), probably due to the short duration of the simulated apnea episodes.Clinical relevance Increased variability in ECG depolarization morphology during recurrent hypoxic episodes would be closely related to the expression of cardiovascular dysfunction in OSA patients.
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Palacios S, Caiani EG, Landreani F, Martínez JP, Pueyo E. Long-Term Microgravity Exposure Increases ECG Repolarization Instability Manifested by Low-Frequency Oscillations of T-Wave Vector. Front Physiol 2019; 10:1510. [PMID: 31920714 PMCID: PMC6928004 DOI: 10.3389/fphys.2019.01510] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Accepted: 11/29/2019] [Indexed: 11/13/2022] Open
Abstract
Ventricular arrhythmias and sudden cardiac death during long-term space missions are a major concern for space agencies. Long-duration spaceflight and its ground-based analog head-down bed rest (HDBR) have been reported to markedly alter autonomic and cardiac functioning, particularly affecting ventricular repolarization of the electrocardiogram (ECG). In this study, novel methods are developed, departing from previously published methodologies, to quantify the index of Periodic Repolarization Dynamics (PRD), an arrhythmic risk marker that characterizes sympathetically-mediated low-frequency oscillations in the T-wave vector. PRD is evaluated in ECGs from 42 volunteers at rest and during an orthostatic tilt table test recorded before and after 60-day –6° HDBR. Our results indicate that tilt test, on top of enhancing sympathetic regulation of heart rate, notably increases PRD, both before and after HDBR, thus supporting previous evidence on PRD being an indicator of sympathetic modulation of ventricular repolarization. Importantly, long-term microgravity exposure is shown to lead to significant increases in PRD, both when evaluated at rest and, even more notably, in response to tilt test. The extent of microgravity-induced changes in PRD has been associated with arrhythmic risk in prior studies. An exercise-based, but not a nutrition-based, countermeasure is able to partially reverse microgravity-induced effects on PRD. In conclusion, long-term exposure to microgravity conditions leads to elevated low-frequency oscillations of ventricular repolarization, which are potentiated following sympathetic stimulation and are related to increased risk for repolarization instabilities and arrhythmias. Tested countermeasures are only partially effective in counteracting microgravity effects.
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Affiliation(s)
- Saúl Palacios
- BSICoS Group, Aragón Institute of Engineering Research, IIS Aragón, Universidad de Zaragoza, Zaragoza, Spain
| | - Enrico G Caiani
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy
| | - Federica Landreani
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy
| | - Juan Pablo Martínez
- BSICoS Group, Aragón Institute of Engineering Research, IIS Aragón, Universidad de Zaragoza, Zaragoza, Spain.,CIBER en Bioingeniería, Biomateriales y Nanomedicina, Madrid, Spain
| | - Esther Pueyo
- BSICoS Group, Aragón Institute of Engineering Research, IIS Aragón, Universidad de Zaragoza, Zaragoza, Spain.,CIBER en Bioingeniería, Biomateriales y Nanomedicina, Madrid, Spain
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Ramírez J, van Duijvenboden S, Aung N, Laguna P, Pueyo E, Tinker A, Lambiase PD, Orini M, Munroe PB. Cardiovascular Predictive Value and Genetic Basis of Ventricular Repolarization Dynamics. Circ Arrhythm Electrophysiol 2019; 12:e007549. [PMID: 31607149 DOI: 10.1161/circep.119.007549] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Early prediction of cardiovascular risk in the general population remains an important issue. The T-wave morphology restitution (TMR), an ECG marker quantifying ventricular repolarization dynamics, is strongly associated with cardiovascular mortality in patients with heart failure. Our aim was to evaluate the cardiovascular prognostic value of TMR in a UK middle-aged population and identify any genetic contribution. METHODS We analyzed ECG recordings from 55 222 individuals from a UK middle-aged population undergoing an exercise stress test in UK Biobank (UKB). TMR was used to measure ventricular repolarization dynamics, exposed in this cohort by exercise (TMR during exercise, TMRex) and recovery from exercise (TMR during recovery, TMRrec). The primary end point was cardiovascular events; secondary end points were all-cause mortality, ventricular arrhythmias, and atrial fibrillation with median follow-up of 7 years. Genome-wide association studies for TMRex and TMRrec were performed, and genetic risk scores were derived and tested for association in independent samples from the full UKB cohort (N=360 631). RESULTS A total of 1743 (3.2%) individuals in UKB who underwent the exercise stress test had a cardiovascular event, and TMRrec was significantly associated with cardiovascular events (hazard ratio, 1.11; P=5×10-7), independent of clinical variables and other ECG markers. TMRrec was also associated with all-cause mortality (hazard ratio, 1.10) and ventricular arrhythmias (hazard ratio, 1.16). We identified 12 genetic loci in total for TMRex and TMRrec, of which 9 are associated with another ECG marker. Individuals in the top 20% of the TMRrec genetic risk score were significantly more likely to have a cardiovascular event in the full UKB cohort (18 997, 5.3%) than individuals in the bottom 20% (hazard ratio, 1.07; P=6×10-3). CONCLUSIONS TMR and TMR genetic risk scores are significantly associated with cardiovascular risk in a UK middle-aged population, supporting the hypothesis that increased spatio-temporal heterogeneity of ventricular repolarization is a substrate for cardiovascular risk and the validity of TMR as a cardiovascular risk predictor.
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Affiliation(s)
- Julia Ramírez
- Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry (J.R., S.v.D., A.T., M.O., P.B.M.), Queen Mary University of London, United Kingdom.,Institute of Cardiovascular Science, University College London, United Kingdom (J.R., S.v.D., P.D.L., M.O.)
| | - Stefan van Duijvenboden
- Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry (J.R., S.v.D., A.T., M.O., P.B.M.), Queen Mary University of London, United Kingdom.,Institute of Cardiovascular Science, University College London, United Kingdom (J.R., S.v.D., P.D.L., M.O.)
| | - Nay Aung
- Centre for Advanced Cardiovascular Imaging, William Harvey Research Institute (N.A.), Queen Mary University of London, United Kingdom.,Barts Heart Centre, St Bartholomew's Hospital, London, United Kingdom (N.A., P.D.L.)
| | - Pablo Laguna
- Biomedical Signal Interpretation and Computational Simulation (BSICoS) group, Aragón Institute of Engineering Research, IIS Aragón, University of Zaragoza, Spain (P.L., E.P.).,Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Spain (P.L., E.P.)
| | - Esther Pueyo
- Biomedical Signal Interpretation and Computational Simulation (BSICoS) group, Aragón Institute of Engineering Research, IIS Aragón, University of Zaragoza, Spain (P.L., E.P.).,Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Spain (P.L., E.P.)
| | - Andrew Tinker
- Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry (J.R., S.v.D., A.T., M.O., P.B.M.), Queen Mary University of London, United Kingdom.,National Institute of Health Research Barts Cardiovascular Biomedical Research Centre, Barts and The London School of Medicine and Dentistry (A.T., P.B.M.), Queen Mary University of London, United Kingdom
| | - Pier D Lambiase
- Institute of Cardiovascular Science, University College London, United Kingdom (J.R., S.v.D., P.D.L., M.O.).,Barts Heart Centre, St Bartholomew's Hospital, London, United Kingdom (N.A., P.D.L.)
| | - Michele Orini
- Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry (J.R., S.v.D., A.T., M.O., P.B.M.), Queen Mary University of London, United Kingdom.,Institute of Cardiovascular Science, University College London, United Kingdom (J.R., S.v.D., P.D.L., M.O.)
| | - Patricia B Munroe
- Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry (J.R., S.v.D., A.T., M.O., P.B.M.), Queen Mary University of London, United Kingdom.,National Institute of Health Research Barts Cardiovascular Biomedical Research Centre, Barts and The London School of Medicine and Dentistry (A.T., P.B.M.), Queen Mary University of London, United Kingdom
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Sampedro-Puente DA, Fernandez-Bes J, Porter B, van Duijvenboden S, Taggart P, Pueyo E. Mechanisms Underlying Interactions Between Low-Frequency Oscillations and Beat-to-Beat Variability of Celullar Ventricular Repolarization in Response to Sympathetic Stimulation: Implications for Arrhythmogenesis. Front Physiol 2019; 10:916. [PMID: 31427979 PMCID: PMC6687852 DOI: 10.3389/fphys.2019.00916] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2018] [Accepted: 07/04/2019] [Indexed: 12/12/2022] Open
Abstract
Background and Objectives: Enhanced beat-to-beat variability of ventricular repolarization (BVR) has been linked to arrhythmias and sudden cardiac death. Recent experimental studies on human left ventricular epicardial electrograms have shown that BVR closely interacts with low-frequency (LF) oscillations of activation recovery interval during sympathetic provocation. In this work human ventricular computational cell models are developed to reproduce the experimentally observed interactions between BVR and its LF oscillations, to assess underlying mechanisms and to establish a relationship with arrhythmic risk. Materials and Methods: A set of human ventricular action potential (AP) models covering a range of experimental electrophysiological characteristics was constructed. These models incorporated stochasticity in major ionic currents as well as descriptions of β-adrenergic stimulation and mechanical effects to investigate the AP response to enhanced sympathetic activity. Statistical methods based on Automatic Relevance Determination and Canonical Correlation Analysis were developed to unravel individual and common factors contributing to BVR and LF patterning of APD in response to sympathetic provocation. Results: Simulated results reproduced experimental evidences on the interactions between BVR and LF oscillations of AP duration (APD), with replication of the high inter-individual variability observed in both phenomena. ICaL, IKr and IK1 currents were identified as common ionic modulators of the inter-individual differences in BVR and LF oscillatory behavior and were shown to be crucial in determining susceptibility to arrhythmogenic events. Conclusions: The calibrated family of human ventricular cell models proposed in this study allows reproducing experimentally reported interactions between BVR and LF oscillations of APD. Ionic factors involving ICaL, IKr and IK1 currents are found to underlie correlated increments in both phenomena in response to sympathetic provocation. A link to arrhythmogenesis is established for concomitantly elevated levels of BVR and its LF oscillations.
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Affiliation(s)
| | | | - Bradley Porter
- Department of Imaging Sciences and Biomedical Engineering, Kings College London, London, United Kingdom
| | | | - Peter Taggart
- Department of Cardiovascular Sciences, University College London, London, United Kingdom
| | - Esther Pueyo
- BSICOS Group, I3A, IIS Aragón, University of Zaragoza, Zaragoza, Spain.,CIBER-BBN, Madrid, Spain
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Ramírez J, Orini M, Mincholé A, Monasterio V, Cygankiewicz I, Bayés de Luna A, Martínez JP, Laguna P, Pueyo E. Sudden cardiac death and pump failure death prediction in chronic heart failure by combining ECG and clinical markers in an integrated risk model. PLoS One 2017; 12:e0186152. [PMID: 29020031 PMCID: PMC5636125 DOI: 10.1371/journal.pone.0186152] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 09/26/2017] [Indexed: 11/20/2022] Open
Abstract
Background Sudden cardiac death (SCD) and pump failure death (PFD) are common endpoints in chronic heart failure (CHF) patients, but prevention strategies are different. Currently used tools to specifically predict these endpoints are limited. We developed risk models to specifically assess SCD and PFD risk in CHF by combining ECG markers and clinical variables. Methods The relation of clinical and ECG markers with SCD and PFD risk was assessed in 597 patients enrolled in the MUSIC (MUerte Súbita en Insuficiencia Cardiaca) study. ECG indices included: turbulence slope (TS), reflecting autonomic dysfunction; T-wave alternans (TWA), reflecting ventricular repolarization instability; and T-peak-to-end restitution (ΔαTpe) and T-wave morphology restitution (TMR), both reflecting changes in dispersion of repolarization due to heart rate changes. Standard clinical indices were also included. Results The indices with the greatest SCD prognostic impact were gender, New York Heart Association (NYHA) class, left ventricular ejection fraction, TWA, ΔαTpe and TMR. For PFD, the indices were diabetes, NYHA class, ΔαTpe and TS. Using a model with only clinical variables, the hazard ratios (HRs) for SCD and PFD for patients in the high-risk group (fifth quintile of risk score) with respect to patients in the low-risk group (first and second quintiles of risk score) were both greater than 4. HRs for SCD and PFD increased to 9 and 11 when using a model including only ECG markers, and to 14 and 13, when combining clinical and ECG markers. Conclusion The inclusion of ECG markers capturing complementary pro-arrhythmic and pump failure mechanisms into risk models based only on standard clinical variables substantially improves prediction of SCD and PFD in CHF patients.
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Affiliation(s)
- Julia Ramírez
- Clinical Pharmacology Department, William Harvey Research Institute, John Vane Science Centre, Queen Mary University of London, Charterhouse Square, London, United Kingdom
- * E-mail:
| | - Michele Orini
- Institute of Cardiovascular Science, University College London, London, United Kingdom
- Barts Heart Centre, St Bartholomeus Hospital, London, United Kingdom
| | - Ana Mincholé
- Department of Computer Science, University of Oxford, Oxford, United Kingdom
| | - Violeta Monasterio
- Universidad San Jorge, Campus Universitario, Villanueva de Gállego, Spain
| | - Iwona Cygankiewicz
- Department of Electrocardiology, Medical University of Lodz, Sterling Regional Center for Heart Diseases, Lodz, Poland
| | - Antonio Bayés de Luna
- Catalan Institute of Cardiovascular Sciences, Santa Creu I Sant Pau Hospital, Barcelona, Spain
| | - Juan Pablo Martínez
- Biomedical Signal Interpretation and Computational Simulation (BSICoS) group, Aragón Institute of Engineering Research, IIS Aragón, University of Zaragoza, Zaragoza, Spain
- Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Zaragoza, Spain
| | - Pablo Laguna
- Biomedical Signal Interpretation and Computational Simulation (BSICoS) group, Aragón Institute of Engineering Research, IIS Aragón, University of Zaragoza, Zaragoza, Spain
- Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Zaragoza, Spain
| | - Esther Pueyo
- Biomedical Signal Interpretation and Computational Simulation (BSICoS) group, Aragón Institute of Engineering Research, IIS Aragón, University of Zaragoza, Zaragoza, Spain
- Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Zaragoza, Spain
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Orini M, Tinker A, Munroe PB, Lambiase PD. Long-term intra-individual reproducibility of heart rate dynamics during exercise and recovery in the UK Biobank cohort. PLoS One 2017; 12:e0183732. [PMID: 28873397 PMCID: PMC5584807 DOI: 10.1371/journal.pone.0183732] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 08/09/2017] [Indexed: 12/26/2022] Open
Abstract
Background The heart rate (HR) response to exercise provides useful information about the autonomic function and has prognostic value, but its reproducibility over a long period of time, a critical requirement for using it as a clinical biomarker, is undetermined. Aim To determine the intra-individual reproducibility of HR dynamics during sub-maximum exercise and one minute recovery. Methods 1187 individuals from the Cardio physical fitness assessment test of the UK Biobank repeated a standard exercise stress test twice (recall time 34.2 ± 2.8 months) and were prospectively studied. Results 821 individuals complied with inclusion criteria for reproducibility analysis, including peak workload differences between assessments ≤10 W. Intra-individual correlation between HR profile during the first and the second assessment was very high and higher than inter-individual correlation (0.92±0.08 vs 0.87±0.11, p<0.01). Intra-individual correlation of indices describing HR dynamics was: ρ = 0.81 for maximum HR during exercise; ρ = 0.71 for minimum HR during recovery; ρ = 0.70 for HR changes during both exercise and recovery; Intra-individual correlation was higher for these indices of HR dynamics than for resting HR (ρ = 0.64). Bland-Altman plots demonstrated good agreement between HR indices estimated during the first and second assessment. A small but consistent bias was registered for all repeated measurements. The intra-individual consistency of abnormal values was about 60–70%. Conclusions The HR dynamics during exercise and recovery are reproducible over a period of 3 years, with moderate to strong intra-individual reproducibility of abnormal values.
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Affiliation(s)
- Michele Orini
- Institute of Cardiovascular Science, University College London, London, United Kingdom
- Barts Heart Centre, St Bartholomew’s Hospital, London, United Kingdom
- * E-mail:
| | - Andrew Tinker
- William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Patricia B. Munroe
- William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Pier D. Lambiase
- Institute of Cardiovascular Science, University College London, London, United Kingdom
- Barts Heart Centre, St Bartholomew’s Hospital, London, United Kingdom
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Ramírez J, Orini M, Mincholé A, Monasterio V, Cygankiewicz I, Bayés de Luna A, Martínez JP, Pueyo E, Laguna P. T-Wave Morphology Restitution Predicts Sudden Cardiac Death in Patients With Chronic Heart Failure. J Am Heart Assoc 2017; 6:JAHA.116.005310. [PMID: 28526702 PMCID: PMC5524085 DOI: 10.1161/jaha.116.005310] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND Patients with chronic heart failure are at high risk of sudden cardiac death (SCD). Increased dispersion of repolarization restitution has been associated with SCD, and we hypothesize that this should be reflected in the morphology of the T-wave and its variations with heart rate. The aim of this study is to propose an electrocardiogram (ECG)-based index characterizing T-wave morphology restitution (TMR), and to assess its association with SCD risk in a population of chronic heart failure patients. METHODS AND RESULTS Holter ECGs from 651 ambulatory patients with chronic heart failure from the MUSIC (MUerte Súbita en Insuficiencia Cardiaca) study were available for the analysis. TMR was quantified by measuring the morphological variation of the T-wave per RR increment using time-warping metrics, and its predictive power was compared to that of clinical variables such as the left ventricular ejection fraction and other ECG-derived indices, such as T-wave alternans and heart rate variability. TMR was significantly higher in SCD victims than in the rest of patients (median 0.046 versus 0.039, P<0.001). When TMR was dichotomized at TMR=0.040, the SCD rate was significantly higher in the TMR≥0.040 group (P<0.001). Cox analysis revealed that TMR≥0.040 was strongly associated with SCD, with a hazard ratio of 3.27 (P<0.001), independently of clinical and ECG-derived variables. No association was found between TMR and pump failure death. CONCLUSIONS This study shows that TMR is specifically associated with SCD in a population of chronic heart failure patients, and it is a better predictor than clinical and ECG-derived variables.
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Affiliation(s)
- Julia Ramírez
- Biomedical Signal Interpretation and Computational Simulation (BSICoS) Group, Aragón Institute of Engineering Research, IIS Aragón University of Zaragoza, Spain .,Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Madrid, Spain
| | - Michele Orini
- Institute of Cardiovascular Science, University College London, London, United Kingdom.,Barts Heart Centre, London, United Kingdom
| | - Ana Mincholé
- Department of Computer Science, University of Oxford, Oxford, United Kingdom
| | | | - Iwona Cygankiewicz
- Department of Electrocardiology, Medical University of Lodz, Lodz, Poland
| | - Antonio Bayés de Luna
- Catalan Institute of Cardiovascular Sciences, Santa Creu I Sant Pau Hospital, Barcelona, Spain
| | - Juan Pablo Martínez
- Biomedical Signal Interpretation and Computational Simulation (BSICoS) Group, Aragón Institute of Engineering Research, IIS Aragón University of Zaragoza, Spain.,Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Madrid, Spain
| | - Esther Pueyo
- Biomedical Signal Interpretation and Computational Simulation (BSICoS) Group, Aragón Institute of Engineering Research, IIS Aragón University of Zaragoza, Spain.,Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Madrid, Spain
| | - Pablo Laguna
- Biomedical Signal Interpretation and Computational Simulation (BSICoS) Group, Aragón Institute of Engineering Research, IIS Aragón University of Zaragoza, Spain.,Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Madrid, Spain
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