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ABSTRACT In medical practice, it is common to perform electrocardiography exams and by mathematical transformations to obtain the vectorcardiogram. The vectorcardiogram provides important information for medical diagnosis, such as the angle of inclination of the heart. This article aims to present a methodology for estimating the QRS vector-related angle of the heart using a posteroanterior chest radiograph image. We used an open source image processing software (Icy software version 2.3.0.0, Institut Pasteur, France, 2021) to perform a manual measurement of the target angle by analyzing relevant morphological structures from the x-ray images and using some functions to help the user to measure it. 18 radiographic images were selected to measure the angle of the heart by two independent individuals. The measured angles were compared using the mean absolute error (MAE). We then computed the QRS peak elevation angles of the vectorcardiogram (VCG) of the 57 patients collected at Dante Pazzanese Institute of Cardiology. In addition, an individual was randomly selected to measure a set of 57 radiographic images of these same patients. We performed the statistical treatments and the results suggested that the proposed manual method may be an alternative, viable and fast approach to estimating the anatomical heart axis for the purpose of aiding in medical diagnosis. However, further comparisons with more data and information are needed to determine its validity and possible method improvements.

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Alteration of muscle activation sequence is a key mechanism in heart failure with reduced ejection fraction. Successful cardiac resynchronization therapy (CRT), which has become standard therapy in these patients, is limited by the lack of precise dyssynchrony quantification. We implemented a computational pipeline that allows assessment of ventricular dyssynchrony by vectorcardiogram reconstruction from the patient's electrocardiogram. We defined a ventricular dyssynchrony index as the distance between the voltage and speed time integrals of an individual observation and the linear fit of these variables obtained from a healthy population. The pipeline was tested in a 1914-patient population. The dyssynchrony index showed minimum values in heathy controls and maximum values in patients with left bundle branch block (LBBB) or with a pacemaker (PM). We established a critical dyssynchrony index value that discriminates electrical dyssynchronous patterns (LBBB and PM) from ventricular synchrony. In 10 patients with PM or CRT devices, dyssynchrony indexes above the critical value were associated with high time to peak strain standard deviation, an echocardiographic measure of mechanical dyssynchrony. Our index proves to be a promising tool to evaluate ventricular activation dyssynchrony, potentially enhancing the selection of candidates for CRT, device configuration during implantation, and post-implant optimization.

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Objectives: Thousands of people suffer from cardiovascular diseases. Even though the electrocardiogram is an exam consolidated. The lack of methodological observation in the placement of sensors can compromise the results. This article proposes a wearable vest capable of conditioning cardiac signals from three simultaneous channels, reducing the chance of failures in the exam due to the smaller number of electrodes attached to the patient's body. Methods: It adds the vectorcardiogram technique to the electrocardiogram wearable, which consists of three orthonormal derivations Vx, Vy, and Vz, measuring dynamic components of the heart vector. Results: The display of the cardiac biopotential in the web-mobile application represents the visualization of the twelve derivations synthesized from the Dower transform and the spatial projections of the cardiac loop under a three-dimensional view. Conclusion: Feasibility of integrating the vectorcardiogram with the electrocardiogram exam.

Objetivos: Milhares de pessoas sofrem com doenças cardiovasculares, apesar do Eletrocardiograma ser um exame consolidado, a falta de observação metodológica na colocação dos sensores pode comprometer os resultados. O presente artigo propõe um colete vestível capaz de condicionar sinais cardíacos de três canais simultâneos, reduzindo a chance de falhas na execução do exame em função da menor quantidade de eletrodos fixados ao corpo do paciente. Métodos: Acrescenta a técnica do vetocardiograma ao vestível de eletrocardiograma, que consiste em três derivações ortonormais Vx, Vy e Vz, medindo componentes dinâmicos do vetor coração. Resultados: Exibição do biopotencial cardíaco na aplicação web-mobile representa de forma satisfatória a visualização das doze derivações sintetizadas a partir da transformada de Dower, bem como, as projeções espaciais do loop cardíaco sob uma visão tridimensional. Conclusão: Viabilidade de integração do vetocardiograma ao exame de eletrocardiograma.

Objetivos: Miles de personas padecen enfermedades cardiovasculares, a pesar de que el electrocardiograma es un examen consolidado, la falta de observación metodológica en la colocación de sensores puede comprometer los resultados. Este artículo propone una tecnología vestible capaz de acondicionar las señales cardíacas de tres canales simultáneos, reduciendo la posibilidad de fallas en el examen por la menor cantidad de electrodos adheridos al cuerpo del paciente. Métodos: Agrega la técnica del vetocardiograma al electrocardiograma vestible, que consta de tres derivaciones ortonormales Vx, Vy y Vz, midiendo los componentes dinámicos del vector cardíaco. Resultados: La visualización del biopotencial cardíaco en la aplicación web-móvil representa satisfactoriamente la visualización de las doce derivaciones sintetizadas a partir de la transformada de Dower, así como las proyecciones espaciales del bucle cardíaco bajo una vista tridimensional. Conclusión: Viabilidad de integrar el vetocardiograma con el examen electrocardiográfico.

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INTRODUÇÃO: O eletrocardiograma (ECG) é uma ferramenta diagnóstica primordial em cardiologia. Através de técnicas de pós-processamento do ECG digital é possível extrair dados do clássico vetorcardiograma (VCG) e ampliar as possibilidades do método. OBJETIVO: Comparar os dados matriciais do ECG entre os pacientes portadores de hipertrofia ventricular patológica (Cardiomiopatia Hipertrófica e Amiloidose Cardíaca) e o grupo controle utilizando duas matrizes diferentes de transformação de ECG para VCG: a matriz inversa de Dower (iDower) e a matriz de Kors. MÉTODOS: Foram analisados VCGs sintetizados a partir das duas matrizes, iDower e Kors, e tais exames foram obtidos para o grupo hipertrófico, composto por 11 pacientes, e para o grupo controle, com cinco pacientes. O tempo de coleta do ECG foi de 10 minutos e, para cada paciente, foram analisados 10 VCGs, referentes a cada minuto da coleta. Foram analisados a amplitude cúbica (mV), por meio da análise da variação dos valores, e o ângulo do complexo QRS e da onda T, por meio da análise de dados circulares. RESULTADOS: Em relação aos ângulos, as médias dos ângulos de cada grupo tiveram maior proximidade no grupo controle e menor no grupo hipertrófico. A variação destes ângulos foi maior utilizando a matriz de Kors para o grupo controle (Figura.1); no entanto, no grupo hipertrófico a maior variação no observada na matriz iDower (Figura 2). Em relação à amplitude cúbica das ondas, a variação foi pequena para ambos os grupos, porém com proximidade maior na onda T, e não houve diferença notável em relação às matrizes. CONCLUSÃO: Analisando as variáveis angulares e de amplitude cúbica nas ondas QRS e T para o grupo controle e hipertrófico, não foi observada diferença significativa entre os grupos. Tal proximidade entre as variáveis também foi observada considerando as matrizes de transformação.

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Until the mid-1980s, it was believed that the vectorcardiogram (VCG) presented a greater specificity, sensitivity and accuracy in comparison to the 12-lead electrocardiogram (ECG), in the cardiology diagnosis. Currently, the VCG still is superior to the ECG in specific situations, such as in the evaluation of myocardial infarctions when associated with intraventricular conduction disturbances, in the identification and location of accessory pathways in ventricular preexcitation, in the differential diagnosis of patterns varying from normal of electrical axis deviation, in the evaluation of particular aspects of Brugada syndrome, Brugada phenocopies, concealed form of arrhythmogenic right ventricular cardiomyopathy and zonal or fascicular blocks of the right bundle branch on right ventricular free wall.VCG allows us to analyze the presence of left septal fascicular block more accurately than ECG and in the diagnosis of the interatrial blocks and severity of some chambers enlargements. The three-dimensional spatial orientation of both the atrial and the ventricular activity provides a far more complete observation tool than the linear ECG. We believe that the ECG/VCG binomial simultaneously obtained by the technique called electro-vectorcardiography (ECG/VCG) brought a significant gain for the differential diagnosis of several pathologies. Finally, in the field of education and research, VCG provided a better and more rational tridimensional insight into the electrical phenomena that occurs spatially, and represented an important impact on the progress of electrocardiography.

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Electrical activity of the heart can be presented using different methods, and the standard is ECG, in which the changes in electric amplitude in one axis are written on paper that moves at a known velocity. Vectorcardiography uses Cartesian (rectangular) coordinates and plots points defined by the simultaneous values in the x and y axes. In this paper, a new graphic display of electrical heart activity based on Polar coordinates is presented. In polar coordinates, the point is defined by the magnitude of the vector (electrical amplitude) and the angle in relation to x or y or z axes, and all the leads can be overlapped. The information used by this method is the same that for simultaneous 12 leads standard ECG and it needs no additional cables or technician labor. Polar coordinates are very good for comparison of time/amplitude mismatch in different leads, to detect the cardiac axis and to explore the impulse conduction. Also, it facilitates the learning of ECG physical basis. This method differs from the classic Dower's Polarcardiography because it uses the classic leads instead of the X, Y and Z leads, and it does not apply magnitude tracings.

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Resumen Introducción: El ángulo QRS-T espacial es la diferencia entre el vector del QRS y la T. Se conoce el valor diagnóstico y pronóstico de este marcador en enfermedades cardíacas. Es prioritario determinar si estas mediciones son reproducibles con confiabilidad en nuestro medio. Métodos: En 30 adultos se obtuvieron electrocardiogramas, independientemente del diagnóstico. Las mediciones las realizaron dos estudiantes de Medicina de quinto año, un médico interno y un cardiólogo, posterior a un reentrenamiento sobre la medición del ángulo por el método de transformación visual. Con identificación cegada, ingresaron en un aplicativo web las mediciones del QRS y la T. El ángulo fue estimado a partir de la plantilla de Cortez y colaboradores. Sobre el 20% de las lecturas se estimó un acuerdo intraobservador y en el 100% de las lecturas un acuerdo interobservador. Los puntos de corte para estimar el acuerdo Kappa fueron < 105s (normal), 105° a 135° (limítrofe) y > 135° (anormal). Resultados: Se excluyó un ECG por calidad deficiente. El rango del ángulo estuvo entre 72.9° y 176.2°. El acuerdo interobservador entre los 4 evaluadores fue kappa = 0.786 (IC95% 0.728-0.823, p < 0.0001) y el intraobservador kappa = 1.0 (p 0.007). Conclusión: Es el primer estudio sobre el ángulo QRS-T espacial realizado en Colombia. Se logró un acuerdo inter- e intraobservador adecuado en la medición del ángulo por el método de transformación visual, en observadores con diferente experticia, con un kappa mayor de 0,75. Este resultado apoya la reproducibilidad de esta medición en estudios posteriores en Colombia.

Abstract Introduction: The spatial QRS-T angle is the difference between the QRS vector and T vector. The diagnostic and prognostic value of this marker in heart disease is well-known. It is essential to determine whether these measurements are reproducible and reliable in Colombia. Methods: Electrocardiograms (ECG) were obtained from 30 adults, regardless of the diagnosis. The measurements were made by two fifth-year medical students, a houseman/ intern, and a cardiologist. They were all re-trained on the measurement of the angle using the visual transformation method. With blinded identification, they entered the QRS and T measurements into a web application. The angle was estimated from the template of Cortez et al. About 20% of the readers showed an intra-observer agreement and an inter-observer agreement in 100%. The cut-off points to estimate the agreement Kappa were < 105° (normal), 105° a 135° (borderline), and >135° (abnormal). Results: One ECG was excluded due to poor quality. The range of the angle was between 72.9° and 176.2°. The inter-observer agreement between the 4 evaluators gave a kappa = 0.786 (95% CI; 0.728-0.823, P < .0001), and the intra-observer agreement a kappa = 1.0 (P = .007). Conclusion: This the first study on the spatial QRS-T angle performed in Colombia. A good inter- and intra-observer agreement was achieved in the measurement of the angle by the visual transformation method by observers with different levels of expertise, with a Kappa greater than 0.75. These results support the reproducibility of this measurement in subsequent studies in Colombia.

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INTRODUCTION: The vectorcardiography (VCG) is a method of representing the heart's electrical activity in three dimensions that is not frequently used in clinical practice due to the higher complexity compared to electrocardiography (ECG). A way around this problem was the development of regression techniques to obtain the VCG from the 12 lead ECG and the evaluation of these techniques is done by comparing the parameters obtained by the gold standard method and by the VCG obtained by the alternative methods. In this paper it is proposed instead a comparison between the images of the VCG planes using the values returned by digital image processing metrics such as PSNR, SSIM and PW-SSIM. METHODS: The signals used were obtained from the Physikalisch-Technische Bundesanstalt Diagnostic ECG Database, which contains both the VCGs obtained by the gold standard method and the 12 lead ECG signals. They were divided into five groups that contained a control group and according to the region of the wall infarction. The ECG signals were then filtered using a Butterworth Finite Impulse Response bandpass filter, with cutoff frequencies of 3 Hz and 45 Hz and then the VCGs were by a computer application using the Kors inverse matrix method, the Kors quasi-orthogonal method and the Dower Inverse Matrix method. The reconstructed signals were then compared using the PSNR, SSIM and PW-SSIM methods. The returned values were presented in tables for each group containing the average value and standard deviance for each method in each VCG plane. RESULTS: Using image processing techniques, it was possible to perceive that the alternative methods to obtain the VCG have a high confiability that could be compared to the gold standard in signals from healthy subjects. However, signals from pathological subjects present variations that could be caused by a deficit of these alternative methods to represent the pathology in these cases. Considering the PW-SSIM, the frontal plane by the reconstructions was considered the most similar to the gold standard, having PW-SSIM values higher than 0.93 and for the horizontal plane two groups had PW-SSIM values lower than 0.90 and for the Sagittal plane all groups had values lower than this value. DISCUSSION: The values yielded by the PSNR and SSIM had low variance, worsening the perception of the effect of the reconstruction method used or the infarction effect over the reconstruction. The values lower than 0.90 could indicate that these planes have their generation most affected by the infarction. CONCLUSION: The three methods of obtaining the VCG Frank leads, the Kors Quasi-Orthogonal method, the Kors Linear Regression method and the Dower Inverse Matrix, presented differences in the metrics: PSNR, SSIM and PW-SSIM in normal subjects according to the planes frontal, horizontal and sagittal and in subjects with Myocardial Infarction according to its topography: anterior, inferolateral, inferior or multiarterials. Considering only the PW-SSIM, the QO method had the best performance in different signals, followed by the Dower method. (AU)

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INTRODUCTION: The vectorcardiography (VCG) is a method of representing the heart's electrical activity in three dimensions that is not frequently used in clinical practice due to the higher complexity compared to electrocardiography (ECG). A way around this problem was the development of regression techniques to obtain the VCG from the 12­lead ECG and the evaluation of these techniques is done by comparing the parameters obtained by the gold standard method and by the VCG obtained by the alternative methods. In this paper it is proposed instead a comparison between the images of the VCG planes using the values returned by digital image processing metrics such as PSNR, SSIM and PW-SSIM. METHODS: The signals used were obtained from the Physikalisch-Technische Bundesanstalt Diagnostic ECG Database, which contains both the VCGs obtained by the gold standard method and the 12 lead ECG signals. They were divided into five groups that contained a control group and according to the region of the wall infarction. The ECG signals were then filtered using a Butterworth Finite Impulse Response bandpass filter, with cutoff frequencies of 3 Hz and 45 Hz and then the VCGs were by a computer application using the Kors inverse matrix method, the Kors quasi-orthogonal method and the Dower Inverse Matrix method. The reconstructed signals were then compared using the PSNR, SSIM and PW-SSIM methods. The returned values were presented in tables for each group containing the average value and standard deviance for each method in each VCG plane. RESULTS: Using image processing techniques, it was possible to perceive that the alternative methods to obtain the VCG have a high confiability that could be compared to the gold standard in signals from healthy subjects. However, signals from pathological subjects present variations that could be caused by a deficit of these alternative methods to represent the pathology in these cases. Considering the PW-SSIM, the Frontal plane by the reconstructions was considered the most similar to the gold standard, having PW-SSIM values higher than 0.93 and for the Horizontal plane two groups had PW-SSIM values lower than 0.90 and for the Sagittal plane all groups had values lower than this value. DISCUSSION: The values yielded by the PSNR and SSIM had low variance, worsening the perception of the effect of the reconstruction method used or the infarction effect over the reconstruction. The values lower than 0.90 could indicate that these planes have their generation most affected by the infarction. CONCLUSION: The three methods of obtaining the VCG Frank leads, the Kors Quasi-Orthogonal method, the Kors Linear Regression method and the Dower Inverse Matrix, presented differences in the metrics: PSNR, SSIM and PW-SSIM in normal subjects according to the planes frontal, horizontal and sagittal and in subjects with Myocardial Infarction according to its topography: anterior, inferolateral, inferior or multiarterials. Considering only the PW-SSIM, the QO method had the best performance in different signals, followed by the Dower method.

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