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The Application of Computer Techniques to ECG Interpretation

A special issue of Hearts (ISSN 2673-3846).

Deadline for manuscript submissions: closed (30 June 2021) | Viewed by 106735

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editor


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Guest Editor
Institute of Health and Wellbeing, University of Glasgow, Glasgow G31 2ER, UK
Interests: electrocardiogaphy; automated interpretation of ECGs

Special Issue Information

Dear Colleagues,

This issue sets out to provide truly up-to-date information on a variety of computer techniques applied to electrocardiography. These include a review of the latest international guidelines for developers of software for ECG interpretation through a variety of uses of artificial intelligence in ECG analysis. The use of the ECG for specific diagnostic purposes such as exercise testing, patient monitoring, treatment of cardiac arrhythmias, ambulatory monitoring and population surveys is also included.  Body surface mapping and modelling as well as a review of more recently introduced criteria for conduction defects complement the other presentations.

Prof. Dr. Peter Macfarlane
Guest Editor

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Keywords

  • electrocardiogram
  • artificial intelligence
  • automated interpretation
  • ECGI
  • body surface mapping
  • patient monitoring
  • ambulatory monitoring
  • inverse modelling

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Published Papers (12 papers)

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Editorial

Jump to: Research, Review

5 pages, 158 KiB  
Editorial
The Application of Computer Techniques to ECG Interpretation
by Peter W. Macfarlane
Hearts 2022, 3(1), 1-5; https://doi.org/10.3390/hearts3010001 - 11 Jan 2022
Cited by 1 | Viewed by 3585
Abstract
It is over 120 years since Einthoven introduced the electrocardiogram [...] Full article
(This article belongs to the Special Issue The Application of Computer Techniques to ECG Interpretation)

Research

Jump to: Editorial, Review

29 pages, 6464 KiB  
Article
Body Surface Potential Mapping: Contemporary Applications and Future Perspectives
by Jake Bergquist, Lindsay Rupp, Brian Zenger, James Brundage, Anna Busatto and Rob S. MacLeod
Hearts 2021, 2(4), 514-542; https://doi.org/10.3390/hearts2040040 - 5 Nov 2021
Cited by 21 | Viewed by 7267
Abstract
Body surface potential mapping (BSPM) is a noninvasive modality to assess cardiac bioelectric activity with a rich history of practical applications for both research and clinical investigation. BSPM provides comprehensive acquisition of bioelectric signals across the entire thorax, allowing for more complex and [...] Read more.
Body surface potential mapping (BSPM) is a noninvasive modality to assess cardiac bioelectric activity with a rich history of practical applications for both research and clinical investigation. BSPM provides comprehensive acquisition of bioelectric signals across the entire thorax, allowing for more complex and extensive analysis than the standard electrocardiogram (ECG). Despite its advantages, BSPM is not a common clinical tool. BSPM does, however, serve as a valuable research tool and as an input for other modes of analysis such as electrocardiographic imaging and, more recently, machine learning and artificial intelligence. In this report, we examine contemporary uses of BSPM, and provide an assessment of its future prospects in both clinical and research environments. We assess the state of the art of BSPM implementations and explore modern applications of advanced modeling and statistical analysis of BSPM data. We predict that BSPM will continue to be a valuable research tool, and will find clinical utility at the intersection of computational modeling approaches and artificial intelligence. Full article
(This article belongs to the Special Issue The Application of Computer Techniques to ECG Interpretation)
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<p>BSPM analysis approaches. BSPM signals are analyzed using one of three different pathways and using two types of mathematical models. Signal analysis methods generally operate on the BSP signals isolated from their geometry. Map analysis extends signal analysis by including the geometry of the torso from which the BSP are recorded. Both signal analysis and map analysis usually rely predominately on statistical models. ECG imaging is based predominately on a deterministic model to reconstructing the cardiac activity at the heart (see the cutaway in the last panel) using the BSP signals and the geometry of the thorax.</p>
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<p>Body surface mapping lead arrangements and torso geometry examples. Bordeaux Torso Tank array (<b>A</b>) [<a href="#B88-hearts-02-00040" class="html-bibr">88</a>]. Utah Torso Tank array (<b>B</b>) [<a href="#B89-hearts-02-00040" class="html-bibr">89</a>]. Utah Large Animal Body Surface Map (<b>C</b>) [<a href="#B90-hearts-02-00040" class="html-bibr">90</a>]. Maastricht Dog Torso Map (<b>D</b>) [<a href="#B58-hearts-02-00040" class="html-bibr">58</a>]. EP Solutions patient 24 (<b>E</b>) [<a href="#B91-hearts-02-00040" class="html-bibr">91</a>]. KIT 20 PVC torso (<b>F</b>) Karlsruhe Institute of Technology. Nijmegen Human Torso 2004-12-09 (<b>G</b>) University of Nijmegen. Dalhausi Human Torso (<b>H</b>) ([<a href="#B82-hearts-02-00040" class="html-bibr">82</a>]). These geometries and associated body surface data (except C) can be found on EDGAR, a cardiac electrophysiology open database (edgar.sci.utah.edu) (accessed date 29 October 2021) [<a href="#B92-hearts-02-00040" class="html-bibr">92</a>].</p>
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<p>An example BSP map with timepoint of interest visualized. The signal shown is from a stimulated ventricular activation from the anterior left ventricle. The time singnal (bottom) is the RMS of the torso surface signals. The time instances shown are the peak of the RMS QRS, the end of the QRS, and the peak of the T-wave.</p>
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<p>Custom signal acquisition system described by Zenger et al. [<a href="#B90-hearts-02-00040" class="html-bibr">90</a>]. This system includes custom electrode arrays, a front-end interface for connecting various electrode array configurations, analog processing, analog to digital conversion by a commercial intan recording system, and data visualization and saving software. The ADC and display software are designed by Intan Technologies (<a href="http://intantech.com" target="_blank">intantech.com</a>) (accessed date 29 October 2021).</p>
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<p>Example ECGI implementation. Recorded body surface potentials (left) are combined with a geometric model and a source model. The geometric model is made up of the relative positions of the cardiac geometry and torso geometry. The source model in this case is extracelular potentials, and the relationship used for the forward model is the boundary element method. The resulting inverse estimation is extracellular potentials on the cardiac surface. The final column shows a comparison between the inverse solution and the measured extracellular potentials on a flattened version of the cardiac geometry. The cardiac and torso geometries were generated as described in Bergquist et al. [<a href="#B111-hearts-02-00040" class="html-bibr">111</a>] where the cardiac geometry is a 256 electrode pericardiac cage array and the torso geometry is a 192 electrode torso tank. Tikhonov 2nd order regularization with L curve was used. The peak of the RMS of the QRS was visualized in all steps.</p>
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<p>Transformation of BSP maps into inputs for various types of machine learning. BSPM signals are first preprocessed, which varies depending on the type of ML model. For feature-based models, characteristics of the BSP signals (QRS integral, T wave peak, activation time, etc.) are calculated and provided as the input signals. For simple linear neural networks and other vector-based ML models the BSP signals are linearized, concatenating the signal form each electrodes into a single vector. For image- and natural language-based ML models, the BSP signals are arranged into a matrix of <span class="html-italic">m</span> leads by <span class="html-italic">n</span> electrodes, which can then be spilt into <span class="html-italic">s</span> length words. For graph-based ML models, the torso geometry is used to create a computational graph that relates the BSP signals to each other based on their spatial relationships.</p>
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10 pages, 948 KiB  
Article
Electrocardiographic Predictors of Mortality: Data from a Primary Care Tele-Electrocardiography Cohort of Brazilian Patients
by Gabriela M. M. Paixão, Emilly M. Lima, Paulo R. Gomes, Derick M. Oliveira, Manoel H. Ribeiro, Jamil S. Nascimento, Antonio H. Ribeiro, Peter W. Macfarlane and Antonio L. P. Ribeiro
Hearts 2021, 2(4), 449-458; https://doi.org/10.3390/hearts2040035 - 29 Sep 2021
Cited by 1 | Viewed by 3665
Abstract
Computerized electrocardiography (ECG) has been widely used and allows linkage to electronic medical records. The present study describes the development and clinical applications of an electronic cohort derived from a digital ECG database obtained by the Telehealth Network of Minas Gerais, Brazil, for [...] Read more.
Computerized electrocardiography (ECG) has been widely used and allows linkage to electronic medical records. The present study describes the development and clinical applications of an electronic cohort derived from a digital ECG database obtained by the Telehealth Network of Minas Gerais, Brazil, for the period 2010–2017, linked to the mortality data from the national information system, the Clinical Outcomes in Digital Electrocardiography (CODE) dataset. From 2,470,424 ECGs, 1,773,689 patients were identified. A total of 1,666,778 (94%) underwent a valid ECG recording for the period 2010 to 2017, with 1,558,421 patients over 16 years old; 40.2% were men, with a mean age of 51.7 [SD 17.6] years. During a mean follow-up of 3.7 years, the mortality rate was 3.3%. ECG abnormalities assessed were: atrial fibrillation (AF), right bundle branch block (RBBB), left bundle branch block (LBBB), atrioventricular block (AVB), and ventricular pre-excitation. Most ECG abnormalities (AF: Hazard ratio [HR] 2.10; 95% CI 2.03–2.17; RBBB: HR 1.32; 95%CI 1.27–1.36; LBBB: HR 1.69; 95% CI 1.62–1.76; first degree AVB: Relative survival [RS]: 0.76; 95% CI0.71–0.81; 2:1 AVB: RS 0.21 95% CI0.09–0.52; and RS 0.36; third degree AVB: 95% CI 0.26–0.49) were predictors of overall mortality, except for ventricular pre-excitation (HR 1.41; 95% CI 0.56–3.57) and Mobitz I AVB (RS 0.65; 95% CI 0.34–1.24). In conclusion, a large ECG database established by a telehealth network can be a useful tool for facilitating new advances in the fields of digital electrocardiography, clinical cardiology and cardiovascular epidemiology. Full article
(This article belongs to the Special Issue The Application of Computer Techniques to ECG Interpretation)
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<p>Diagram for ECG abnormality diagnosis. Concordance between the cardiologist’s report and one of the automatic systems (Glasgow or Minnesota) was required for a diagnosis to be accepted without manual revision.</p>
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<p>Kaplan–Meier curves for overall mortality.</p>
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19 pages, 3999 KiB  
Article
Excitation and Contraction of the Failing Human Heart In Situ and Effects of Cardiac Resynchronization Therapy: Application of Electrocardiographic Imaging and Speckle Tracking Echo-Cardiography
by Christopher M. Andrews, Gautam K. Singh and Yoram Rudy
Hearts 2021, 2(3), 331-349; https://doi.org/10.3390/hearts2030027 - 23 Jul 2021
Cited by 1 | Viewed by 3760
Abstract
Despite the success of cardiac resynchronization therapy (CRT) for treating heart failure (HF), the rate of nonresponders remains 30%. Improvements to CRT require understanding of reverse remodeling and the relationship between electrical and mechanical measures of synchrony. The objective was to utilize electrocardiographic [...] Read more.
Despite the success of cardiac resynchronization therapy (CRT) for treating heart failure (HF), the rate of nonresponders remains 30%. Improvements to CRT require understanding of reverse remodeling and the relationship between electrical and mechanical measures of synchrony. The objective was to utilize electrocardiographic imaging (ECGI, a method for noninvasive cardiac electrophysiology mapping) and speckle tracking echocardiography (STE) to study the physiology of HF and reverse remodeling induced by CRT. We imaged 30 patients (63% male, mean age 63.7 years) longitudinally using ECGI and STE. We quantified CRT-induced remodeling of electromechanical parameters and evaluated a novel index, the electromechanical delay (EMD, the delay from activation to peak contraction). We also measured dyssynchrony using ECGI and STE and compared their effectiveness for predicting response to CRT. EMD values were elevated in HF patients compared to controls. However, the EMD values were dependent on the activation sequence (CRT-paced vs. un-paced), indicating that the EMD is not intrinsic to the local tissue, but is influenced by factors such as opposing wall contractions. After 6 months of CRT, patients had increased contraction in native rhythm compared to baseline pre-CRT (baseline: −8.55%, 6 months: −10.14%, p = 0.008). They also had prolonged repolarization at the location of the LV pacing lead. The pre-CRT delay between mean lateral LV and RV electrical activation time was the best predictor of beneficial reduction in LV end systolic volume by CRT (Spearman’s Rho: −0.722, p < 0.001); it outperformed mechanical indices and 12-lead ECG criteria. HF patients have abnormal EMD. The EMD depends upon the activation sequence and is not predictive of response to CRT. ECGI-measured LV activation delay is an effective index for CRT patient selection. CRT causes persistent improvements in contractile function. Full article
(This article belongs to the Special Issue The Application of Computer Techniques to ECG Interpretation)
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Figure 1
<p>Schematic of the ECGI procedure. Body-surface potentials are recorded from the torso surface using a portable recording system (top). The heart-torso geometry is obtained using a computed tomography (CT) or magnetic resonance imaging (MRI) scan (bottom). The heart-torso geometry and torso potentials are combined and the inverse problem is solved to reconstruct unipolar epicardial electrograms. Electrograms are processed to determine local electrical parameters of interest (right frame).</p>
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<p>The LV was segmented using a modified version of the American Heart Association 17-Segment Model. Apical segments were modified from the standard model because ECGI images the epicardium which does not include any septal segments. The apical LV segments from the ECGI maps were divided into Apical Anterolateral and Apical Inferolateral segments.</p>
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<p>Healthy adult activation and contraction. (<b>A</b>) Activation isochrones. Atria and left anterior descending coronary artery are shown in gray. Right ventricular outflow tract is shown in blue. Left ventricular outflow tract is shown in pink. Asterisk indicates epicardial breakthrough site. (<b>B</b>) Speckle tracking echocardiography (STE) strain curves plotted below the ECG. Electrical activation times are indicated in the plot with vertical lines (dashed lines indicate right ventricular activation as an approximation of septal activation time). Dotted line indicates aortic valve closure. The timing of peak strain within anatomical segments (top bullseye plot) was homogeneous within the LV. Regional electromechanical delay (EMD) values (bottom bullseye plot) were computed by subtracting the electrical activation time from the time of peak strain within regions. EMD values were not computed for septal regions (shown in gray) because ECGI does not image the septum. RV: right ventricle; LV: left ventricle; RA: right atrium; LA: left atrium.</p>
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<p>Activation isochrone maps in HF-CRT patients in native rhythm prior to CRT pacing (left) and at pacing onset (right). Pacing lead locations are indicated with black spheres. CRT pacing decreases LV activation delay absolute value (“Improvement”). Echocardiographic responders (top 2 rows) generally had high levels of dyssynchrony at baseline which was substantially improved by CRT pacing. Nonresponders often had less baseline dyssynchrony (row 3) or ineffective lead placement (row 4). RV: right ventricle; LV: left ventricle.</p>
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<p>Native rhythm strains in HF-CRT patients (top) were dyssynchronous and lower in amplitude than controls. Lateral regions often stretched prior to contraction (arrow) and reached peak strain after aortic valve closure (dotted line). Many regions reached peak strain later than controls (top bullseye). The mean EMD in HF patients was the same as in controls, but values within the LV showed greater dispersion (bottom bullseye). The acute onset of CRT (bottom) decreased pre-systolic lateral wall stretch. Peak strain timing values did not capture synchrony improvements effectively. Regional EMDs were different for each activation sequence (native rhythm vs. CRT pacing), indicating that EMD is not a purely intrinsic property.</p>
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<p>Left ventricular views of electrogram fractionation maps (first column), native rhythm activation (middle column), and CRT-paced activation (right column). Representative fractionated and un-fractionated electrograms are provided to the left of the maps. Numbers indicate electrogram locations. Pacing electrodes are indicated with black or white spheres. Pacing within regions of fractionation was less effective at activating nearby regions outside the scar (top row). Patients with large regions of fractionation could still be resynchronized effectively when paced outside of the fractionated region (bottom row). NICM: Nonischemic cardiomyopathy.</p>
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<p>Peak contraction magnitudes improved during the course of CRT. Values at each visit were determined from un-paced native rhythm beats, indicating persistent improvements in contraction as a result of chronic CRT pacing. Global longitudinal strain values (in percent) are indicated below each bullseye plot.</p>
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<p>Native rhythm epicardial activation-recovery interval (ARI) maps in heart failure (<b>left</b>) and after 6 months of CRT pacing (<b>right</b>). After 6 months of CRT pacing, ARI values were prolonged at and around the location of the left ventricle (LV) pacing lead.</p>
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Review

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9 pages, 23257 KiB  
Review
ECG Interpretation: Clinical Relevance, Challenges, and Advances
by Nikita Rafie, Anthony H. Kashou and Peter A. Noseworthy
Hearts 2021, 2(4), 505-513; https://doi.org/10.3390/hearts2040039 - 2 Nov 2021
Cited by 30 | Viewed by 38072
Abstract
Since its inception, the electrocardiogram (ECG) has been an essential tool in medicine. The ECG is more than a mere tracing of cardiac electrical activity; it can detect and diagnose various pathologies including arrhythmias, pericardial and myocardial disease, electrolyte disturbances, and pulmonary disease. [...] Read more.
Since its inception, the electrocardiogram (ECG) has been an essential tool in medicine. The ECG is more than a mere tracing of cardiac electrical activity; it can detect and diagnose various pathologies including arrhythmias, pericardial and myocardial disease, electrolyte disturbances, and pulmonary disease. The ECG is a simple, non-invasive, rapid, and cost-effective diagnostic tool in medicine; however, its clinical utility relies on the accuracy of its interpretation. Computer ECG analysis has become so widespread and relied upon that ECG literacy among clinicians is waning. With recent technological advances, the application of artificial intelligence-augmented ECG (AI-ECG) algorithms has demonstrated the potential to risk stratify, diagnose, and even interpret ECGs—all of which can have a tremendous impact on patient care and clinical workflow. In this review, we examine (i) the utility and importance of the ECG in clinical practice, (ii) the accuracy and limitations of current ECG interpretation methods, (iii) existing challenges in ECG education, and (iv) the potential use of AI-ECG algorithms for comprehensive ECG interpretation. Full article
(This article belongs to the Special Issue The Application of Computer Techniques to ECG Interpretation)
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<p>ECG showing traditional computer-generated interpretation versus AI-ECG interpretation. The AI-ECG interpretation provides a more accurate interpretation of the ECG, while the traditional computer-generated interpretation mislabels sinus arrhythmia for premature atrial complexes and overestimates the QT interval.</p>
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<p>ECG showing traditional computer-generated interpretation versus AI-ECG interpretation. The AI-ECG interpretation provides a more specific and accurate interpretation of the ECG, while the computer-generated interpretation does not identify the first-degree AV block. While the AI-ECG algorithm is able to identify the AV conduction defect, it does not report a PR interval duration like traditional computer-generated algorithms.</p>
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<p>Proposed incorporation of AI-ECG into the clinical workflow.</p>
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23 pages, 2398 KiB  
Review
Applications of Machine Learning in Ambulatory ECG
by Joel Xue and Long Yu
Hearts 2021, 2(4), 472-494; https://doi.org/10.3390/hearts2040037 - 13 Oct 2021
Cited by 16 | Viewed by 5944
Abstract
The ambulatory ECG (AECG) is an important diagnostic tool for many heart electrophysiology-related cases. AECG covers a wide spectrum of devices and applications. At the core of these devices and applications are the algorithms responsible for signal conditioning, ECG beat detection and classification, [...] Read more.
The ambulatory ECG (AECG) is an important diagnostic tool for many heart electrophysiology-related cases. AECG covers a wide spectrum of devices and applications. At the core of these devices and applications are the algorithms responsible for signal conditioning, ECG beat detection and classification, and event detections. Over the years, there has been huge progress for algorithm development and implementation thanks to great efforts by researchers, engineers, and physicians, alongside the rapid development of electronics and signal processing, especially machine learning (ML). The current efforts and progress in machine learning fields are unprecedented, and many of these ML algorithms have also been successfully applied to AECG applications. This review covers some key AECG applications of ML algorithms. However, instead of doing a general review of ML algorithms, we are focusing on the central tasks of AECG and discussing what ML can bring to solve the key challenges AECG is facing. The center tasks of AECG signal processing listed in the review include signal preprocessing, beat detection and classification, event detection, and event prediction. Each AECG device/system might have different portions and forms of those signal components depending on its application and the target, but these are the topics most relevant and of greatest concern to the people working in this area. Full article
(This article belongs to the Special Issue The Application of Computer Techniques to ECG Interpretation)
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<p>There are a wide range of AECG devices and applications. The recording length can be from 30 s to 30 days, and the number of leads of ECG can be from 1 to 12. At the center of all these lies the AECG algorithms including filtering, beat detection and classifications, and event detection and prediction. For devices with 1 or 2 leads, the events are mainly in rhythm abnormalities, such as sinus, AFIB, or tachycardia/bradycardia. For devices with more leads, some morphology analysis can be added such as ST, QT, LVH, or BBB.</p>
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<p>A diagram for the most widely used statistical learning algorithms. Most of the non-deep learning algorithms listed here can work on moderate-sized data since their independent parameters are limited. These algorithms mostly work on previously extracted features, or they can help to identify the best features such as PCA. On the left is unsupervised learning mainly used for clustering and feature optimization; on the right are supervised learning algorithms, requiring pairs of inputs and labels. All these methods have been used widely in AECG applications in the last several decades.</p>
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<p>A diagram of a summary of DL algorithms. DL models rely on big data. For AECG, a large ECG waveform database with corresponding labels is needed for training purposes. In the list, CNN and RNN are the most popular DL models. Transfer learning and ensemble learning also become practical for AECG. However, there has been limited use of reinforcement learning and self-supervised learning thus far. AE and VAE are very useful for noise detection and feature extraction.</p>
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<p>Signal preprocessing can have 2 parallel paths, one (the upper path) is mainly for noise reduction and SNR improvement, but with some signal distortion, while the other (the bottom path) is also for noise reduction but with minimal signal distortion. The results from the first path can be used to assist the second path, e.g., signal averaging; as shown in the figure, an average beat is formed with the trigger points detected from the first path.</p>
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<p>DL models can be trained for beat detection and classification directly from ECG waveform. The key is to define the input/reference pair. The label can indicate beat type and noise segment.</p>
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<p>A diagram of CNN model for AECG classifications. The model input can be a single beat or multiple beats. Multiple ECG leads can form an ECG image. If only 1 lead is presented, then 1-D CNN can be used. However, if there are multiple leads as inputs, 2-D CNN can be used. There are multiple CNN blocks to form a deep layer structure. Usually, the number of filters is gradually increased, but the size of the output of each block is reduced by down-sampling after each block of max/average pooling and stride operation. The final block of the model consists of fully connected layers. The final output can be either binary or multiple classifications.</p>
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<p>RNN model includes one or multiple RNN layers with multiple cells in each layer. Here, LSTM cells are used. The input of RNN is a series of ECG waveforms or ECG parameters, e.g., R-R intervals or P-R-T components. The last block of the model consists of fully connected layers. The final output can be either binary or multiple classifications.</p>
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13 pages, 4079 KiB  
Review
Computer Assisted Patient Monitoring: Associated Patient, Clinical and ECG Characteristics and Strategy to Minimize False Alarms
by Michele M. Pelter, David Mortara and Fabio Badilini
Hearts 2021, 2(4), 459-471; https://doi.org/10.3390/hearts2040036 - 1 Oct 2021
Cited by 2 | Viewed by 6860
Abstract
This chapter is a review of studies that have examined false arrhythmia alarms during in-hospital electrocardiographic (ECG) monitoring in the intensive care unit. In addition, we describe an annotation effort being conducted at the UCSF School of Nursing, Center for Physiologic Research designed [...] Read more.
This chapter is a review of studies that have examined false arrhythmia alarms during in-hospital electrocardiographic (ECG) monitoring in the intensive care unit. In addition, we describe an annotation effort being conducted at the UCSF School of Nursing, Center for Physiologic Research designed to improve algorithms for lethal arrhythmias (i.e., asystole, ventricular fibrillation, and ventricular tachycardia). Background: Alarm fatigue is a serious patient safety hazard among hospitalized patients. Data from the past five years, showed that alarm fatigue was responsible for over 650 deaths, which is likely lower than the actual number due to under-reporting. Arrhythmia alarms are a common source of false alarms and 90% are false. While clinical scientists have implemented a number of interventions to reduce these types of alarms (e.g., customized alarm settings; daily skin electrode changes; disposable vs. non-disposable lead wires; and education), only minor improvements have been made. This is likely as these interventions do not address the primary problem of false arrhythmia alarms, namely deficient and outdated arrhythmia algorithms. In this chapter we will describe a number of ECG features associated with false arrhythmia alarms. In addition, we briefly discuss an annotation effort our group has undertaken to improve lethal arrhythmia algorithms. Full article
(This article belongs to the Special Issue The Application of Computer Techniques to ECG Interpretation)
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<p>Frequency of all unique physiologic alarms from bedside ICU monitors over a 31-day study period. Figure from Drew, B.J. et al. [<a href="#B2-hearts-02-00036" class="html-bibr">2</a>] (open access with permission to use Figure). Abbreviations: ACC Vent = accelerated ventricular rhythm; Afib = atrial fibrillation; ART = arterial blood pressure; HR = heart rate; ICP = intracranial pressure; NIBP = non-invasive blood pressure; PVC = premature ventricular complexes; RR = respiratory rate; Sp02 = saturation of peripheral oxygen; ST = ST-segment; Vtach = ventricular tachycardia; V brady = ventricular bradycardia; and Vfib = ventricular fibrillation.</p>
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<p>The figures above are rhythm strips showing leads I, II, III, and V (V1—at our hospital) and an arterial blood pressure waveform (AR1) in an intensive care unit patient. The top rhythm strip is an alarm for ventricular tachycardia (VT) during acute respiratory distress. Note the arterial blood pressure is unchanged at 146/89 mmHg and the Sp02 is 96% during the alarm. The bottom figure is a rhythm strip prior to the VT alarm showing normal sinus rhythm, first degree atrioventricular block with right bundle branch block (BBB). The arterial blood pressure is 138/59 and Sp02 is 99%. The QRS morphology in lead V1 in the top strip is identical to that of in the bottom tracings; hence, the top strip in not VT, but rather sinus tachycardia in a patient with right BBB during acute respiratory distress. This patient had a total of 79 false VT alarms (wide QRS heart rate &gt; 100 beats/min) and 120 alarms for accelerated ventricular rhythm (wide QRS &lt; 100 beats/min) during a seven-day ICU stay, illustrating the issue of false alarms due to BBB. Figure from the ECG Monitoring Research Lab, UCSF School of Nursing.</p>
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<p>False alarm for accelerated ventricular rhythm defined as &gt;6 ventricular beats with a heart rate between 50 and 100 beats/min in a patient with a ventricular paced rhythm. Figure from the ECG Monitoring Research Lab, UCSF School of Nursing. The Pacer Mode feature was not turned on (star) in this patient, which led to non-stop false AVR alarms.</p>
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<p>Low amplitude QRS complexes in the limb leads in a patient with left bundle branch block. The * (red) denotes the leads available on the bedside ECG monitor. Reprinted from Ref. [<a href="#B2-hearts-02-00036" class="html-bibr">2</a>].</p>
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<p>False alarms for ventricular fibrillation. As noted by the *, in lead III, this patient is in a normal sinus rhythm. This particular manufacturer requires a clean ECG signal in at least two ECG leads. Figure from the ECG Monitoring Research Lab, UCSF School of Nursing.</p>
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<p>Illustrates an arrhythmia alarm for ventricular tachycardia ready for annotation using the Continuous ECG Recording Suite (CER-S) software program. The annotator selected a response (true, false, etc.) and then selected “Next Alarm” to move onto the next annotation. Note that an Sp02 waveform is shown in the bottom context view for use by the annotator when making a decision. Arterial blood pressure is also available if the patient has this device in place. Figure from the Center for Physiologic Research, UCSF School of Nursing.</p>
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16 pages, 1688 KiB  
Review
Automated ECG Interpretation—A Brief History from High Expectations to Deepest Networks
by Peter W. Macfarlane and Julie Kennedy
Hearts 2021, 2(4), 433-448; https://doi.org/10.3390/hearts2040034 - 23 Sep 2021
Cited by 14 | Viewed by 8532
Abstract
This article traces the development of automated electrocardiography from its beginnings in Washington, DC around 1960 through to its current widespread application worldwide. Changes in the methodology of recording ECGs in analogue form using sizeable equipment through to digital recording, even in wearables, [...] Read more.
This article traces the development of automated electrocardiography from its beginnings in Washington, DC around 1960 through to its current widespread application worldwide. Changes in the methodology of recording ECGs in analogue form using sizeable equipment through to digital recording, even in wearables, are included. Methods of analysis are considered from single lead to three leads to twelve leads. Some of the influential figures are mentioned while work undertaken locally is used to outline the progress of the technique mirrored in other centres. Applications of artificial intelligence are also considered so that the reader can find out how the field has been constantly evolving over the past 50 years. Full article
(This article belongs to the Special Issue The Application of Computer Techniques to ECG Interpretation)
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<p>Dr. C. Caceres (<b>left</b>) and Dr. H. Pipberger (<b>right</b>).</p>
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<p>The first automated ECG interpretation system in operation in Glasgow Royal Infirmary around 1971. One technician controlled the tape recorder and listened to the patient details which were also recorded. The second technician monitored the three orthogonal lead ECG on the oscilloscope and started the analogue to digital conversion. The software was stored on the small digital tapes (DECtapes) and retrieved as necessary.</p>
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<p>The CSE steering committee pictured in 1987 laughing at each other wearing glasses. The picture was taken by PWM. From left to right: (inset) Peter Macfarlane (1987); Christoph Zywietz; Jan van Bemmel; Rosanna Degani; Pierre Arnaud; Jos Willems; (inset) Paul Rubel (1992), who took over from Pierre Arnaud.</p>
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<p>One of the earliest standalone electrocardiographs with automated ECG interpretation.</p>
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<p>Participants in the comparative study of ECG measurements gather together in 2012 in Birmingham, Alabama anxiously listening to Dr. Paul Kligfield on the extreme left explaining the rules. He is being assisted by Dr. Cindy Green and Dr. Fabio Badilini. Representatives (from centre to right) from Mortara Inc, Philips, GE and Glasgow make up the remainder of those present.</p>
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15 pages, 10705 KiB  
Review
Current ECG Aspects of Interatrial Block
by Antoni Bayés-de-Luna, Miquel Fiol-Sala, Manuel Martínez-Sellés and Adrian Baranchuk
Hearts 2021, 2(3), 419-432; https://doi.org/10.3390/hearts2030033 - 8 Sep 2021
Cited by 7 | Viewed by 4383
Abstract
Interatrial blocks like other types of block may be of first degree or partial second degree, also named transient atrial block or atrial aberrancy, and third degree or advanced. In first degree, partial interatrial block (P-IAB), the electrical impulse is conducted to the [...] Read more.
Interatrial blocks like other types of block may be of first degree or partial second degree, also named transient atrial block or atrial aberrancy, and third degree or advanced. In first degree, partial interatrial block (P-IAB), the electrical impulse is conducted to the left atrium, through the Bachmann’s region, but with delay. The ECG shows a P-wave ≥ 120 ms. In third-degree, advanced interatrial block (A-IAB), the electrical impulse is blocked in the upper part of the interatrial septum (Bachmann region); the breakthrough to LA has to be performed retrogradely from the AV junction zone. This explains the p ± in leads II, III and aVF. In typical cases of A-IAB, the P-wave morphology is biphasic (±) in leads II, III and aVF, because the left atrium is activated retrogradely and, therefore, the last part of the atrial activation falls in the negative hemifield of leads II, III and aVF. Recently, some atypical cases of A-IAB have been described. The presence of A-IAB is a risk factor for atrial fibrillation, stroke, dementia, and premature death. Full article
(This article belongs to the Special Issue The Application of Computer Techniques to ECG Interpretation)
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<p>(<b>A</b>) Diagram of atrial conduction under normal circumstances; (<b>B</b>) partial interatrial block, and (<b>C</b>) typical advanced interatrial block with left atrial retrograde activation (IAB with LARA).</p>
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<p>Transient changes of P-wave recorded in lead II after applying ice to the Bachmann’s region. Surface electrocardiogram (ECG) of an open-chest anesthetized healthy adult swine, before, during, and after direct application of ice at the transversus sinus of the pericardium (Bachmann’s region). A change in P-wave duration and morphology, constituting a transient interatrial block (IAB), is observed as rapidly evolving from partial to advanced IAB (A-IAB). Subsequently, as the ice melts, the ECG pattern normalizes. Please note that P-wave duration in pigs is different (shorter) than in humans. (Taken from reference 22).</p>
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<p>Examples of the 3 types of atrial activity: (<b>A</b>) normal P-wave (P-wave duration &lt;120 ms), (<b>B</b>) partial interatrial block (P-wave duration ≥120 ms), (<b>C</b>) advanced interatrial block (P-wave duration ≥120 ms with biphasic morphology (+/− in leads II, III, and aVF).</p>
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<p>Typical ECG of advanced interatrial block (P-wave ± in leads II, III, and aVF and duration ≥120 ms) in a patient with ischemic heart disease. When amplified (left) we can see the beginning and the end of the P-wave in the three leads.</p>
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<p>(<b>A</b>). P-wave ± morphology in leads II and III typical of advanced IAB with retrograde conduction to the left atrium. Note how the ÂP and the angle between the direction of the activation in the first and second parts of the P-wave are measured. (<b>B</b>). Note also the open <span class="html-italic">P</span> loops with the last part upwards (FP and RSP). (<b>C</b>). Intra-esophageal ECG (HE) and endocavitary registrations (HRA: high right atrium; LRA: low right atrium) demonstrate that the electrical stimulus moves first downwards (HRA–LRA) and then upwards (LRA–HE). (Taken from reference 5).</p>
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<p>Virtual anatomic rendering of the LA in a patient with typical biphasic (±) P-wave in leads II, III, and aVF suggestive of A-IAB (Bachmann’s region block). Note that early left atrial activation (white) occurs at the high septal wall, as expected for Bachmann region conduction. Activation does not progress through the left atrial roof because of the presence of a large zone of low voltage (gray) that diverts activation toward the low septal (orange-yellow) then the low posterior (green) and finally the high posterior (violet) left atrial wall. (Taken from reference 19).</p>
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<p>Probability of remaining free of supraventricular tachyarrhythmias (atrial flutter and atrial fibrillation) in patients with advanced interatrial block (IAB) and controls (partial IAB). (Take from reference 13).</p>
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<p>(<b>A</b>). Typical A-IAB. (<b>B</b>). Atypical A-IAB by duration. (<b>C</b>). Type 1 atypical A-IAB due to morphology. The P-wave is biphasic in leads III, and aVF, but the terminal component of the P wave in lead II is isodiphasic. (<b>D</b>). Type II atypical A-IAB. The P-wave is biphasic in leads III and aVF, but triphasic in lead II (+ − +). (<b>E</b>). Type III atypical A-IAB. The P-wave morphology is negative in leads III and aVF, and biphasic in lead II with the initial component of the P-wave in leads III and aVF isodiphasic. (Taken from reference 23).</p>
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<p>(<b>A</b>,<b>B</b>): Normal P-waves. In panel B, there is a biphasic (±) pattern in lead III. This is considered normal because the last part of the P loop falls in the negative hemifield of lead III, that start at +30° but it is positive in leads II and aVF, because the P loop falls in positive hemifield of these leads that starts −30° and 0° (<b>C</b>) typical A-IAB. The second part of the P loop falls in the negative hemifield of leads II, III and aVF. (<b>D</b>–<b>F</b>): the 3 atypical A-IAB patterns by morphology. (Taken from reference 23).</p>
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<p>(<b>A</b>) P-wave in a case of A-IAB atypical type 3 by morphology. Note that the P-wave is negative in III and aVF, but with a first part isodiphasic as may be seen with vertical lines. It may be confused with junctional rhythm, but in this case (see <b>B</b>) all the P-wave is negative and, furthermore, the P-wave is also negative in V4–V6. (Taken from reference 37).</p>
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<p>(<b>A</b>,<b>B</b>) A case of a 73-year old man found to have a large lipoma (4 × 5 cm) located on the interatrial septum. Cardiac magnetic resonance imaging allowed for complete characterization. As the atrial fibrosis is not extended in all atria, the duration of the P-wave in spite of A-IAB is &lt;120 ms. (Taken from reference 38).</p>
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<p>Lead II ECG strip from an 82-year-old man with frequent PVCs. The first two beats show typical advanced IAB (P-wave in lead II is biphasic, with P-wave duration &gt;120 ms). After the premature ventricular contraction (PVC), there is a pause followed by a P-wave of normal duration and morphology. The next P wave again depicts advanced IAB. This case serves as an example of second degree IAB induced by a pause after a PVC.</p>
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<p>(<b>A</b>) Leads II, III and aVF of a 77-year-old man with hypertrophic cardiomyopathy. Heart rate 70 bpm: P-wave 160 ms (partial IAB). (<b>B</b>) Same patient was hospitalized due to a febrile episode (39°). The heart rate increased to 100 bpm, and the P-wave depicts a typical pattern of advanced IAB (biphasic morphology in leads II, III, and aVF) and duration of 175 ms. The advanced IAB pattern is associated with a tachycardia-dependent (Phase 3) block. This ECG pattern normalized after fever was controlled and heart rate decreased.</p>
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<p>A case that describes the temporal evolution (<b>A</b>–<b>C</b>) of IAB. (<b>A</b>) P-wave of partial IAB to a definitive A-IAB pattern (<b>C</b>) with extremely low voltages. See in the lower part (<b>D</b>), magnetic resonance image with advanced fibrosis.</p>
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9 pages, 341 KiB  
Review
The New ISO/IEC Standard for Automated ECG Interpretation
by Brian Young and Johann-Jakob Schmid
Hearts 2021, 2(3), 410-418; https://doi.org/10.3390/hearts2030032 - 27 Aug 2021
Cited by 5 | Viewed by 8571
Abstract
Updates to industry consensus standards for ECG equipment is a work-in-progress by the ISO/IEC Joint Work Group 22. This work will result in an overhaul of existing industry standards that apply to ECG electromedical equipment and will result in a new single international [...] Read more.
Updates to industry consensus standards for ECG equipment is a work-in-progress by the ISO/IEC Joint Work Group 22. This work will result in an overhaul of existing industry standards that apply to ECG electromedical equipment and will result in a new single international industry, namely 80601-2-86. The new standard will be entitled “80601, Part 2-86: Particular requirements for the basic safety and essential performance of electrocardiographs, including diagnostic equipment, monitoring equipment, ambulatory equipment, electrodes, cables, and leadwires”. This paper will provide a high-level overview of the work in progress and, in particular, will describe the impact it will have on requirements and testing methods for computerized ECG interpretation algorithms. The conclusion of this work is that manufacturers should continue working with clinical ECG experts to make clinically meaningful improvements to automated ECG interpretation, and the clinical validation of ECG analysis algorithms should be disclosed to guide appropriate clinical use. More cooperation is needed between industry, clinical ECG experts and regulatory agencies to develop new data sets that can be made available for use by industry standards for algorithm performance evaluation. Full article
(This article belongs to the Special Issue The Application of Computer Techniques to ECG Interpretation)
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<p>Examples of simulated waveforms from the CTS database used for algorithm performance testing in current ECG standards [<a href="#B2-hearts-02-00032" class="html-bibr">2</a>]. (<b>a</b>) Example of a calibration ECG waveform with ECG waves and interval nomenclature indicated; (<b>b</b>) example of an analytic ECG waveform with ECG waves and interval nomenclature indicated.</p>
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26 pages, 3457 KiB  
Review
The History and Challenges of SCP-ECG: The Standard Communication Protocol for Computer-Assisted Electrocardiography
by Paul Rubel, Jocelyne Fayn, Peter W. Macfarlane, Danilo Pani, Alois Schlögl and Alpo Värri
Hearts 2021, 2(3), 384-409; https://doi.org/10.3390/hearts2030031 - 24 Aug 2021
Cited by 9 | Viewed by 6776
Abstract
Ever since the first publication of the standard communication protocol for computer-assisted electrocardiography (SCP-ECG), prENV 1064, in 1993, by the European Committee for Standardization (CEN), SCP-ECG has become a leading example in health informatics, enabling open, secure, and well-documented digital data exchange at [...] Read more.
Ever since the first publication of the standard communication protocol for computer-assisted electrocardiography (SCP-ECG), prENV 1064, in 1993, by the European Committee for Standardization (CEN), SCP-ECG has become a leading example in health informatics, enabling open, secure, and well-documented digital data exchange at a low cost, for quick and efficient cardiovascular disease detection and management. Based on the experiences gained, since the 1970s, in computerized electrocardiology, and on the results achieved by the pioneering, international cooperative research on common standards for quantitative electrocardiography (CSE), SCP-ECG was designed, from the beginning, to empower personalized medicine, thanks to serial ECG analysis. The fundamental concept behind SCP-ECG is to convey the necessary information for ECG re-analysis, serial comparison, and interpretation, and to structure the ECG data and metadata in sections that are mostly optional in order to fit all use cases. SCP-ECG is open to the storage of the ECG signal and ECG measurement data, whatever the ECG recording modality or computation method, and can store the over-reading trails and ECG annotations, as well as any computerized or medical interpretation reports. Only the encoding syntax and the semantics of the ECG descriptors and of the diagnosis codes are standardized. We present all of the landmarks in the development and publication of SCP-ECG, from the early 1990s to the 2009 International Organization for Standardization (ISO) SCP-ECG standards, including the latest version published by CEN in 2020, which now encompasses rest and stress ECGs, Holter recordings, and protocol-based trials. Full article
(This article belongs to the Special Issue The Application of Computer Techniques to ECG Interpretation)
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<p>Example of the high compression obtained by subtracting a reference beat from all complexes (including extrasystoles), filtering and sample decimation of the non-protected areas, and second difference calculations [<a href="#B42-hearts-02-00031" class="html-bibr">42</a>]. These types of lossy compression schemes, e.g., filtering, sample decimation, and beat subtraction, are no longer allowed in SCP-ECG V3.0 (See Chapter 4 and [<a href="#B39-hearts-02-00031" class="html-bibr">39</a>]). Figure adapted from EN 1064:2020 [<a href="#B39-hearts-02-00031" class="html-bibr">39</a>].</p>
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<p>Snapshot of the conceptual ECG data acquisition reference model developed during the AIM A1015 SCP-ECG project and fully implemented during the OEDIPE project [<a href="#B40-hearts-02-00031" class="html-bibr">40</a>,<a href="#B43-hearts-02-00031" class="html-bibr">43</a>,<a href="#B48-hearts-02-00031" class="html-bibr">48</a>,<a href="#B49-hearts-02-00031" class="html-bibr">49</a>,<a href="#B50-hearts-02-00031" class="html-bibr">50</a>,<a href="#B51-hearts-02-00031" class="html-bibr">51</a>].</p>
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<p>Generic bi-directional SCP-ECG message to database interface schema. This is an updated version of the original “File to Database” schema developed by the OEDIPE project [<a href="#B49-hearts-02-00031" class="html-bibr">49</a>], where eXtensible Markup Language (XML) and eXtensible Stylesheet Language Transformations (XSLT) tools were based on Abstract Syntax Notation 1 (ASN.1) [<a href="#B50-hearts-02-00031" class="html-bibr">50</a>,<a href="#B51-hearts-02-00031" class="html-bibr">51</a>]. The interface updates the database with electrocardiographic information coming from the messages and gives the message handler data retrieved from the database. The solution contains generic software modules independent of the database and SCP-ECG protocol layout. It accesses a descriptive data dictionary containing the database structure, the data format layout, and the mapping between both. The design involves issues related to structure description and standard query language generation and allows automating the development of SCP-ECG Vx.i to Vy.j converters. For more details, see [<a href="#B50-hearts-02-00031" class="html-bibr">50</a>,<a href="#B62-hearts-02-00031" class="html-bibr">62</a>,<a href="#B63-hearts-02-00031" class="html-bibr">63</a>].</p>
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<p>Snapshot of the data part of Section 7 (global measurements), highlighting the structure of the additional global measurements data block and of one of the optional tagged fields, e.g., Tag 8, “QRS Maximum Vector Magnitudes”. SCP-ECG V3.0 defines 17 tagged global ECG measurement data fields, numbered from 0 to 16. The structure and content of tag 8 are detailed in the bottom left (tag, length, value) table. The number of tagged fields actually stored may vary from one SCP-ECG record to another.</p>
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19 pages, 4768 KiB  
Review
Computer Modeling of the Heart for ECG Interpretation—A Review
by Olaf Dössel, Giorgio Luongo, Claudia Nagel and Axel Loewe
Hearts 2021, 2(3), 350-368; https://doi.org/10.3390/hearts2030028 - 26 Jul 2021
Cited by 16 | Viewed by 7356
Abstract
Computer modeling of the electrophysiology of the heart has undergone significant progress. A healthy heart can be modeled starting from the ion channels via the spread of a depolarization wave on a realistic geometry of the human heart up to the potentials on [...] Read more.
Computer modeling of the electrophysiology of the heart has undergone significant progress. A healthy heart can be modeled starting from the ion channels via the spread of a depolarization wave on a realistic geometry of the human heart up to the potentials on the body surface and the ECG. Research is advancing regarding modeling diseases of the heart. This article reviews progress in calculating and analyzing the corresponding electrocardiogram (ECG) from simulated depolarization and repolarization waves. First, we describe modeling of the P-wave, the QRS complex and the T-wave of a healthy heart. Then, both the modeling and the corresponding ECGs of several important diseases and arrhythmias are delineated: ischemia and infarction, ectopic beats and extrasystoles, ventricular tachycardia, bundle branch blocks, atrial tachycardia, flutter and fibrillation, genetic diseases and channelopathies, imbalance of electrolytes and drug-induced changes. Finally, we outline the potential impact of computer modeling on ECG interpretation. Computer modeling can contribute to a better comprehension of the relation between features in the ECG and the underlying cardiac condition and disease. It can pave the way for a quantitative analysis of the ECG and can support the cardiologist in identifying events or non-invasively localizing diseased areas. Finally, it can deliver very large databases of reliably labeled ECGs as training data for machine learning. Full article
(This article belongs to the Special Issue The Application of Computer Techniques to ECG Interpretation)
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<p>Simulated P-waves of the 12-lead ECG with various atrial shapes, several orientations of the atria inside the torso and a variety of body shapes. The colors represent the total atrial volume in blue, the torso size in red and the orientation angle around the medial-lateral axis in orange [<a href="#B50-hearts-02-00028" class="html-bibr">50</a>].</p>
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<p>Examples of ischemic regions with varying transmural extent due to occlusion of the left anterior descending coronary artery and the related levels of hyperkalemia, acidosis, and hypoxia (<b>A</b>). ECG lead V4 for ischemia of varying transmural extent in temporal stage 2 (<b>B</b>) and varying duration of a transmural ischemia (<b>C</b>). Ventricular transmembrane voltage and body surface potential distribution during the action potential plateau (t = 200 ms) for ischemia of varying transmural extent in stage 2 (<b>D</b>). The QRS complex was not optimized in this study. (Images reproduced with permission from [<a href="#B28-hearts-02-00028" class="html-bibr">28</a>].)</p>
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<p>Modeling of ectopic beats and the corresponding ECG: for three different trigger locations in the right ventricle (RV) and left ventricle (LV), the transmembrane voltage (<b>left column</b>), the extracellular potentials (<b>middle column</b>) and corresponding ECGs (<b>right column</b>) are shown. Excitation propagation was computed by solving the anisotropic Eikonal equation.</p>
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<p>Examples of simulated AFlut transmembrane voltage distributions and the corresponding BSPMs and 12-lead ECGs. Top row: AFlut around the tricuspid valve in the counter-clockwise direction. Bottom row: figure-8 macro-re-entry around the left and right pulmonary veins in the anterior direction of rotation [<a href="#B45-hearts-02-00028" class="html-bibr">45</a>].</p>
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