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Background Objectives Animals Methods Results Conclusions and Clinical Importance Reliable ECGs are crucial for diagnosing arrhythmias, yet a lack of standardization impedes arrhythmia diagnosis and treatment in horses.To objectively determine an optimal position of Einthoven's triangle for ECG recordings in horses at rest, which can form the basis for standardized ECG recording and improve diagnosis and treatment of arrhythmias.The study involved 72 healthy, warmblood horses aged between 3 and 20 years.In view of future 12‐lead studies and vectorcardiography, requiring an orthogonal system, Einthoven's triangle was positioned around the heart, in the transverse plane. Therefore, 11 electrodes were placed encircling the thorax behind the olecranon, to construct triangles with a horizontal base. Electrocardiogram recordings from different triangles were analyzed. Signal processing involved filtering, R peak detection, and median complex generation. Principal component analysis (PCA) and Euclidean distance measures were employed for data analysis.The left mid‐thoracic and ventral regions had high PCA scores, indicating high information content. Base‐down triangles exhibited higher summed Euclidean distances, contributing to enhanced diagnostic capabilities. A base‐down triangle, called “Delta (Δ) configuration” emerged as most informative, while meeting all criteria.The base‐down “Delta configuration” is the optimal Einthoven's triangle adapted for horses, providing large amplitudes and potential to provide basic insights into the mechanisms and origins of cardiac arrhythmias. Because the Delta configuration is positioned in the transverse plane, it forms the ideal basis for 12‐lead ECG recordings that provide vectorcardiograms in an orthogonal coordinate system. Standardizing electrode positioning could improve ECG data comparability in equine cardiology. [ABSTRACT FROM AUTHOR]

Context: Cardiogoniometry (CGM) is a noninvasive technique for quantitative three-dimensional vectorial analysis of myocardial depolarization and repolarization. We describe a method of surface electrophysiological cardiac assessment using CGM performed at rest to detect variables helpful in identifying coronary artery disease (CAD) and interplaying factors in patients who underwent coronary artery bypass graft (CABG). Materials and Methods: In this study, all patients with CAD undergoing CABG were enrolled. Echocardiography, CGM, and electrocardiography (ECG) were obtained before surgery and a month later. The ECG and CGM alterations were compared before and after CABG and the accuracy of those two methods was evaluated. Results: In this study, 50 patients were enrolled, of which 33 (66%) were male versus 17 (44%) female, with a mean age of 39.12 ± 60 years. The mean ejection fraction before and after surgery was 44.3 ± 7.9% (range: 20–55) and 40.9 ± 12.5% (20–50), respectively. Before surgery, all patients had sinus rhythm, five cases had left bundle-branch block (LBBB), and one case was with right bundle-branch block (RBBB). Subsequently, after surgery, five cases had LBBB, and two cases were found to have RBBB. The rate of postoperation bleeding was 20%. There was no significant change in echocardiographic characteristics before and after operation (P = 0.81); likewise, no significant change was seen in ECG criteria before and after operation (P = 0.96). A significant correlation was seen regarding CGM characteristics before and after CABG (P = 0.003). Conclusions: A significant association was seen regarding CGM characteristics before and after undergoing an operation. In addition, the specificity and sensitivity of the CGM and ECG before and after operation improved well.

Aims Typical electrocardiogram (ECG) features of apical hypertrophic cardiomyopathy (ApHCM) include tall R waves and deep or giant T-wave inversion in the precordial leads, but these features are not always present. The ECG is used as the gatekeeper to cardiac imaging for diagnosis. We tested whether explainable advanced ECG (A-ECG) could accurately diagnose ApHCM. Methods and results Advanced ECG analysis was performed on standard resting 12-lead ECGs in patients with ApHCM [ n = 75 overt, n = 32 relative (<15 mm hypertrophy); a subgroup of which underwent cardiovascular magnetic resonance (n = 92)], and comparator subjects (n = 2449), including healthy volunteers (n = 1672), patients with coronary artery disease (n = 372), left ventricular electrical remodelling (n = 108), ischaemic (n = 114) or non-ischaemic cardiomyopathy (n = 57), and asymmetrical septal hypertrophy HCM (n = 126). Multivariable logistic regression identified four A-ECG measures that together discriminated ApHCM from other diseases with high accuracy [area under the receiver operating characteristic (AUC) curve (bootstrapped 95% confidence interval) 0.982 (0.965–0.993)]. Linear discriminant analysis also diagnosed ApHCM with high accuracy [AUC 0.989 (0.986–0.991)]. Conclusion Explainable A-ECG has excellent diagnostic accuracy for ApHCM, even when the hypertrophy is relative, with A-ECG analysis providing incremental diagnostic value over imaging alone. The electrical (ECG) and anatomical (wall thickness) disease features do not completely align, suggesting that future diagnostic and management strategies may incorporate both features. [ABSTRACT FROM AUTHOR]

3DQRSarea is a strong marker for cardiac resynchronization therapy and can be obtained by taking the (i) summation or the (ii) difference of the areas subtended by positive and negative deflections in X, Y, Z vectorcardiographic electrocardiogram (ECG) leads. We correlated both methods with the instantaneous‐absolute‐3D‐voltage‐time‐integral (VTIQRS‐3D). 3DQRSarea consistently underestimated the VTIQRS‐3D, but the summation method was a closer and more reliable approximation. The dissimilarity was less apparent in left bundle branch block (r2 summation.996 vs. difference.972) and biventricular paced ECGs (r2.996 vs..957) but was more apparent in normal ECGs (r2.988 vs..653). [ABSTRACT FROM AUTHOR]

Abstract Background Coronary artery calcification (CAC) is associated with poor outcome in critically ill patients. A deterioration in cardiac conduction and loss of myocardial tissue could be an underlying cause. Vectorcardiography (VCG) and cardiac biomarkers provide insight into these underlying causes. The aim of this study was to investigate whether a high degree of CAC is associated with VCG-derived variables and biomarkers, including high-sensitivity troponin-T (hs-cTnT) and N-terminal pro-B-type natriuretic peptide (NT-proBNP). Methods Mechanically ventilated coronavirus-19 (COVID-19) patients with an available chest computed tomography (CT) and 12-lead electrocardiogram (ECG) were studied. CAC scores were determined using chest CT scans. Patients were categorized into 3 sex-specific tertiles: low, intermediate, and high CAC. Daily 12 leads-ECGs were converted to VCGs. Daily hs-cTnT and NT-proBNP levels were determined. Linear mixed-effects regression models examined the associations between CAC tertiles and VCG variables, and between CAC tertiles and hs-cTnT or NT-proBNP levels. Results In this study, 205 patients (73.2% men, median age 65 years [IQR 57.0; 71.0]) were included. Compared to the lowest CAC tertile, the highest CAC tertile had a larger QRS area at baseline (6.65 µVs larger [1.50; 11.81], p = 0.012), which decreased during admission (− 0.27 µVs per day [− 0.43; − 0.11], p = 0.001). Patients with the highest CAC tertile also had a longer QRS duration (12.02 ms longer [4.74; 19.30], p = 0.001), higher levels of log hs-cTnT (0.79 ng/L higher [0.40; 1.19], p

Background: Coronary artery calcification (CAC) is associated with poor outcome in critically ill patients. A deterioration in cardiac conduction and loss of myocardial tissue could be an underlying cause. Vectorcardiography (VCG) and cardiac biomarkers provide insight into these underlying causes. The aim of this study was to investigate whether a high degree of CAC is associated with VCG-derived variables and biomarkers, including high-sensitivity troponin-T (hs-cTnT) and N-terminal pro-B-type natriuretic peptide (NT-proBNP). Methods: Mechanically ventilated coronavirus-19 (COVID-19) patients with an available chest computed tomography (CT) and 12-lead electrocardiogram (ECG) were studied. CAC scores were determined using chest CT scans. Patients were categorized into 3 sex-specific tertiles: low, intermediate, and high CAC. Daily 12 leads-ECGs were converted to VCGs. Daily hs-cTnT and NT-proBNP levels were determined. Linear mixed-effects regression models examined the associations between CAC tertiles and VCG variables, and between CAC tertiles and hs-cTnT or NT-proBNP levels. Results: In this study, 205 patients (73.2% men, median age 65 years [IQR 57.0; 71.0]) were included. Compared to the lowest CAC tertile, the highest CAC tertile had a larger QRS area at baseline (6.65 µVs larger [1.50; 11.81], p = 0.012), which decreased during admission (− 0.27 µVs per day [− 0.43; − 0.11], p = 0.001). Patients with the highest CAC tertile also had a longer QRS duration (12.02 ms longer [4.74; 19.30], p = 0.001), higher levels of log hs-cTnT (0.79 ng/L higher [0.40; 1.19], p < 0.001) and log NT-proBNP (0.83 pmol/L higher [0.30; 1.37], p = 0.002). Conclusion: Patients with a high degree of CAC had the largest QRS area and higher QRS amplitude, which decreased more over time when compared to patients with a low degree of CAC. These results suggest that CAC might contribute to loss of myocardial tissue during critical illness. These insights could improve risk stratification and prognostication of patients with critical illness. [ABSTRACT FROM AUTHOR]

Joint coordination variability during walking that is associated with patellofemoral joint cartilage degeneration after anterior cruciate ligament reconstruction are not well understood. The purpose of this study was to assess between-limb differences in joint coordination variability and to determine the relationship of coordination variability with postoperative patellofemoral joint cartilage composition. Thirty-five patients underwent bilateral gait analysis and a magnetic resonance exam of the reconstructed knee joint at 6 months post anterior cruciate ligament reconstruction. Vector coding was used to assess coordination variability during the early (1%-33%), mid (34%-66%), and late (67%-100%) stance phase. The T1ρ/T2 mapping was used to evaluate the glycosaminoglycan--collagen matrix of the patellar and femoral trochlear cartilage. Compared with the uninjured limb, the reconstructed limb exhibited higher hip sagittal/knee sagittal plane coordination variability during midstance as well as higher knee sagittal/ankle sagittal plane coordination variability during both mid and late stance. The hip sagittal/knee sagittal plane coordination variability during midstance predicted 14.6% of the variance in patellar cartilage T1ρ values within the reconstructed limb. In addition, sex of participants was able to predict 32.4% and 13.7% of the variance in femoral trochlea T1ρ and T2 values, respectively. The study results demonstrate that a multijoint mechanism may be associated with early patellofemoral joint cat-tilage degeneration at 6 months after anterior cruciate ligament reconstruction. [ABSTRACT FROM AUTHOR]

Congenital long QT syndrome (LQTS) carries an increased risk for syncope and sudden death. QT prolongation promotes ventricular extrasystoles, which, in the presence of an arrhythmia substrate, might trigger ventricular tachycardia degenerating into fibrillation. Increased electrical heterogeneity (dispersion) is the suggested arrhythmia substrate in LQTS. In the most common subtype LQT1, physical exercise predisposes for arrhythmia and spatiotemporal dispersion was therefore studied in this context. Thirty-seven patients (57% on b-blockers) and 37 healthy controls (mean age, 31 vs. 35; range, 6--68 vs. 6--72 yr) performed an exercise test. Frank vectorcardiography was used to assess spatiotemporal dispersion as Tampl, Tarea, the ventricular gradient (VG), and the Tpeak-end interval from 10-s signal averages before and 7 ± 2 min after exercise; during exercise too much signal disturbance excluded analysis. Baseline and maximum heart rates as well as estimated exercise intensity were similar, but heart rate recovery was slower in patients. At baseline, QT and heart rate-corrected QT (QTcB) were significantly longer in patients (as expected), whereas dispersion parameters were numerically larger in controls. After exercise, QTpeakcB and Tpeak-endcB increased significantly more in patients (18 ± 23 vs. 7 ± 10 ms and 12 ± 17 vs. 2 ± 6 ms; P < 0.001 and P < 0.01). There was, however, no difference in the change in Tampl, Tarea, and VG between groups. In conclusion, although temporal dispersion of repolarization increased significantly more after exercise in patients with LQT1, there were no signs of exercise-induced increase in global dispersion of action potential duration and morphology. The arrhythmia substrate/mechanism in LQT1 warrants further study. [ABSTRACT FROM AUTHOR]

Introduction: Measurement of the spatial ventricular gradient (SVG), spatial QRST angles, and other vectorcardiographic measures of myocardial electrical heterogeneity have emerged as novel risk stratification methods for sudden cardiac death and other adverse cardiovascular events. Prior studies of normal limits of these measurements included primarily young, healthy, White volunteers, but normal limits in older patients are unknown. The influence of race and body mass index (BMI) on these measurements is also unclear. Methods: Normal 12‐lead electrocardiograms (ECGs) from a single center were identified. Patients with abnormal cardiovascular, pulmonary, or renal history (assessed by International Classification of Disease [ICD‐9/ICD‐10] codes) or abnormal cardiovascular imaging were excluded. The SVG and QRST angles were measured and stratified by age, sex, and race. Multivariable linear regression was used to assess the influence of age, BMI, and heart rate (HR) on these measurements. Results: Among 3292 patients, observed ranges of SVG and QRST angles (peak and mean) differed significantly based on sex, age, and race. Sex differences attenuated with increasing age. Men tended to have larger SVG magnitude (60.4 [46.1–77.8] vs. 52.5 [41.3–65.8] mv*ms, p <.0001) and elevation, and more anterior/negative SVG azimuth (−14.8 [−25.1 to −4.3] vs. 1.3 [−9.8 to 10.5] deg, p <.0001) compared to women. Men also had wider QRST angles. Observed ranges varied significantly with BMI and HR. SVG and QRST angle measurements were robust to different filtering bandwidths and moderate fiducial point annotation errors, but were heavily affected by changes in baseline correction. Conclusions: Age, sex, race, BMI, and HR significantly affect the range of SVG and QRST angles in patients with normal ECGs and no known cardiovascular disease, and should be accounted for in future studies. An online calculator for prediction of these "normal limits" given demographics is provided at https://bivectors.github.io/gehcalc/. [ABSTRACT FROM AUTHOR]

This paper reviews the literature on assessing electrical dyssynchrony for patient selection in cardiac resynchronization therapy (CRT). The guideline-recommended electrocardiographic (ECG) criteria for CRT are QRS duration and morphology, established through inclusion criteria in large CRT trials. However, both QRS duration and LBBB morphology have their shortcomings. Over the past decade, various alternative measures of ventricular dyssynchrony have been proposed, ranging from simple options such as vectorcardiography (VCG), ultra-high frequency ECG, and electrical dyssynchrony mapping to more advanced techniques such as ECG imaging electro-anatomic mapping. Despite promising results, none of these methods have yet been widely adopted in daily clinical practice. The VCG is a relatively cost-effective option for potential clinical implementation, as it can be reconstructed from the standard 12‑lead ECG.With the emergence of conduction system pacing, in addition to predicting the outcome of conventional biventricular CRT, the assessment of electrical dyssynchrony holds promise for defining and optimizing the type of resynchronization strategy. Additionally, artificial intelligence has the potential to reveal unknown features for CRT outcomes, and computer models can provide deeper insights into the underlying mechanisms of these features.

Vectorcardiography (VCG) is a valuable diagnostic tool that complements the standard 12-lead ECG by offering additional spatiotemporal information to clinicians. However, due to the need for additional measurement hardware and too many electrodes in a clinical scenario if performed along with a standard 12-lead, there is a need to find methods to derive the VCG from the ECG. We have evaluated the use of Long Short-term Memory (LSTM) neural networks to learn the transformation from 12-lead ECG to VCG that is applicable across subjects and for each subject. We refer to these networks as generalized and personalized, respectively. We calculated the Root Mean Square Error (RMSE), R2, and Pearson correlation coefficient to compare waveforms of derived and actual VCG. We also extracted and compared diagnostic parameters from VCG, namely the QRS-loop magnitude, T-loop magnitude, and QRS-T spatial angle, from actual and derived VCGs using the Pearson correlation coefficient and Bland Altman limits of agreement. The personalized models performed better than generalized models in waveform comparisons and in the error of extracted diagnostic parameters from VCG waveforms. The use of personalized transformations for the derivation of VCG from standard 12-lead has the potential to improve and augment the diagnostic yield and accuracy of a standard 12-lead interpretation.

SARS-CoV-2 infection is associated with an increased risk of late cardiovascular (CV) outcomes. However, more data is needed to describe the electrophysiologic (EP) manifestation of post-acute CV sequelae of COVID-19. We compared two cohorts of adult patients with SARS-CoV-2 polymerase chain reaction (PCR) test and an electrocardiogram (ECG) performed between March 1, 2020, and September 13, 2020, in a retrospective double-cohort study, "Cardiovascular Risk Stratification in Covid-19" (CaVaR-Co19; NCT04555187). Patients with positive PCR comprised a COVID-19(+) cohort (n = 41; 61% women; 80% symptomatic), whereas patients with negative tests formed the COVID-19(−) cohort (n = 155; 56% women). In longitudinal analysis, comparing 3 ECGs recorded before, during, and on average 40 days after index COVID-19 episode, after adjustment for demographic and socioeconomic characteristics, baseline CV risk factors and comorbidities, use of prescription medications (including QT-prolonging drugs) before and during index COVID-19 episode, and the longitudinal changes in RR' intervals, heart rhythm, and ventricular conduction type, only in the COVID-19(+) cohort QTc increased by +30.2(95% confidence interval [CI] 0.1–60.3) ms and the spatial ventricular gradient (SVG) elevation increased by +13.5(95%CI 1.2–25.9)°. In contrast, much smaller, statistically nonsignificant changes were observed in the COVID-19(−) cohort. In conclusion, post-acute CV sequelae of SARS-CoV-2 infection manifested on ECG by QTc prolongation and rotation of the SVG vector upward. [ABSTRACT FROM AUTHOR]

OBJECTIVE Atherosclerosis and associated coronary artery disease may complicate the stenosis of larger sized arteries such as abdominal aorta, ileac and carotid arteries. Undetected stable coronary artery disease may increase the morbidity and mortality of such surgical interventions. In traditional medical approach, a coronary angiography is usually performed prior to peripheral arterial revascularization in order to rule out coronary arterial involvement. Herein, we would like to share two cases whom an artificial intelligence (AI) analyzed vectorcardiography was used for the abovementioned purpose. The sensitivity of AI-assisted Cardisiography in order to exclude stable coronary artery disease is 97% for males and 90% for females. METHODS Cardisiography focuses on spatial and temporal heterogeneity of cardiac excitation using vectorcardiography with a five-fold nested cross-validation in comparison to angiographic findings1. Two patients, one male with the diagnosis of Leriche Syndrome and one female with bilateral carotid artery stenosis were evaluated with AI-assisted Cardisiography prior to coronary angiography. Cardisiography revealed no significant probability with regard to vectorcardiography and AI based supervised machine learning algorhythms. Afterwards, conventional coronary angiographies were performed and any stenosis in the coronary vascular bed was excluded. Case-1: 42 years old male who had symptoms and clinical findings of Leriche Syndrome (claudication, erectile impotence and diminished peripheral pulses) (Figure-1). Following preoperative evaluation, an aorta-bifemoral bypass graft was interposed uneventfully. Case-2: 55 years old female patient was admitted to our clinic with dizziness and transient ischemic attack. Carotis artery angiography revealed critical stenosis at the left and moderate stenosis at the right internal carotid arteries (Figure-2). A carotid endarterectomy and saphenous vein patch plasty were uneventfully performed. RESULTS Coronary artery involvement in peripheral arterial disease is an important association, since ruling out a critical coronary artery stenosis is deemed mandatory prior to revascularization of carotid arteries, abdominal aorta, ileac arteries and distal branches. AI-assisted Cardisiography may be used as a noninvasive alternative method in the diagnosis of stable coronary artery disease, especially when surgery for carotid artery stenosis is based on Doppler ultrasonographic findings alone (i.e., without performing CT angiography or conventional angiography prior to surgery). CONCLUSIONS AI-assisted Cardisiography may be used as an alternative non-invasive method in order to rule out stable coronary artery disease in patients undergoing peripheral vascular surgery, decreasing the need for conventional angiography. Further large-scale clinical trials will be needed, before further assumptions can be drawn. [ABSTRACT FROM AUTHOR]

Vectorcardiography (VCG) is a valuable diagnostic tool that complements the standard 12-lead ECG by offering additional spatiotemporal information to clinicians. However, due to the need for additional measurement hardware and too many electrodes in a clinical scenario if performed along with a standard 12-lead, there is a need to find methods to derive the VCG from the ECG. We have evaluated the use of Long Short-term Memory (LSTM) neural networks to learn the transformation from 12-lead ECG to VCG that is applicable across subjects and for each subject. We refer to these networks as generalized and personalized, respectively. We calculated the Root Mean Square Error (RMSE), R2, and Pearson correlation coefficient to compare waveforms of derived and actual VCG. We also extracted and compared diagnostic parameters from VCG, namely the QRS-loop magnitude, T-loop magnitude, and QRS-T spatial angle, from actual and derived VCGs using the Pearson correlation coefficient and Bland Altman limits of agreement. The personalized models performed better than generalized models in waveform comparisons and in the error of extracted diagnostic parameters from VCG waveforms. The use of personalized transformations for the derivation of VCG from standard 12-lead has the potential to improve and augment the diagnostic yield and accuracy of a standard 12-lead interpretation. [ABSTRACT FROM AUTHOR]

Background: The spatial ventricular gradient (SVG) is a vectorcardiographic measurement that reflects cardiac loading conditions via electromechanical coupling. Objectives: We hypothesized that the SVG is correlated with right ventricular (RV) strain and is prognostic of adverse events in patients with acute pulmonary embolism (PE). Methods: Retrospective, single‐center study of patients with acute PE. Electrocardiogram (ECG), imaging, and outcome data were obtained. SVG components were regressed on tricuspid annular plane systolic excursion (TAPSE), qualitative RV dysfunction, and RV/left ventricular (LV) ratio. Odds of adverse outcomes (30‐day mortality, vasopressor requirement, or advanced therapy) after PE were regressed on demographics, RV/LV ratios, traditional ECG signs of RV dysfunction, and SVG components using a logit model. Results: ECGs from 317 patients (48% male, age 63.1 ± 16.6 years) with acute PE were analyzed; 36 patients (11.4%) experienced an adverse event. Worse RV hypokinesis, larger RV/LV ratio, and smaller TAPSE were associated with smaller SVG X and Y components, larger SVG Z components, and smaller SVG vector magnitude (p <.001 for all). In multivariable logistic regression, odds of adverse events after PE decreased with increasing SVG magnitude and TAPSE (OR 0.32 and 0.54 per standard deviation increase; p =.03 and p =.004, respectively). Receiver operating characteristic (ROC) analysis showed that, when combined with imaging, replacing traditional ECG criteria with the SVG significantly improved the area under the ROC from 0.70 to 0.77 (p =.01). Conclusion: The SVG is correlated with RV dysfunction and adverse outcomes in acute PE and has a better prognostic value than traditional ECG markers. [ABSTRACT FROM AUTHOR]

The vector concept in the analysis of the electrical signals of the heart began to be used at the dawn of the development of electrocardiology. For several decades, vectorcardiography has developed in parallel with electrocardiography; reached its peak in the 60s, and after a period of cooling experienced a resurgence since the early 90s, when it became possible to mathematically synthesize vectorcardiograms (VCG) from digital electrocardiograms in 12 leads. VCG reflects the same phenomena as electrocardiography, but allows you to calculate and visualize a number of three-dimensional characteristics of the electrical signals of the heart. The article describes the main milestones in the development of the VCG, the history of international cooperation in this area, the contribution of domestic scientists to this field of science. Modern promising areas of research related to the vector concept of the analysis of the electrical signals of the heart are briefly reflected.

In this paper, an attempt is made to simulate and compare spatio-temporal VCG and VMCG derived from epicardial potentials. Electric (EHV) and Magnetic heart vectors (MHV) are computed from the ECG and MCG at various time instants and their orientations with respect to time are found to show a reasonable tilt of 90 to 100 degrees. The complimentary information with reference to the orientation of cardiac vector offered by MHV could be attributed to its sensitivity to intracellular myocardial currents, while EHV exhibits the orientation associated with only the extracellular currents owing to volume conduction. By comparing the orientations of EHV and MHV generated from a simulated equivalent current dipole model, the present work demonstrates the usefulness of these spatiotemporal vectors in tracing the cardiac current flow inside the thorax for a healthy heart. It could be thus expected that clinically relevant information could be obtained if the present analysis is extended to highly complex and irregular cardiac activation sequences that could be seen in arrhythmia and myocardial infarction. The main contribution of this paper is to mathematically model and derive the magnetic heart vectors from the MCG system extracted from IGCAR lab and verify it with the conventional VCG extraction.. [ABSTRACT FROM AUTHOR]

Introduction: Cryotherapy is a therapeutic method used to reduce pain associated with, among others, injuries and inflammation by both young athletes and the elderly. Aim of the research: To investigate the effect of a single cryochamber session on basic ECG-derived parameters in adult non-athletes. Material and methods: A hundred and eight participants without significant cardiac disorders were included in the study. A single session in the cryochamber lasted for 3 min, and the temperature within the appropriate chamber ranged from -150°C to -160°C. When in the cryochamber, each participant wore a tank top, shorts, a surgical mask, a cap, woollen gloves, socks, and wooden clogs. ECG parameters, as well as systolic and diastolic blood pressure were recorded both before and immediately after the cryochamber session. Moreover, vectorcardiographic parameters were generated according to the inverse Dower matrix. Results: The study was performed on 72 females and 36 males with an average age of 50 years; no significant differences were demonstrated between these groups. We observed a statistically significant decrease in the heart rate and QTc interval after the cryochamber session, as well as a minor increase of QRS interval following the cryochamber session. No changes in the spatial QRS-T angle were observed. Conclusions: Based on the collected results, whole-body cryotherapy in a cryochamber seems to be a harmless additional treatment for non-athlete adults without known contraindications for such therapy. Long-term prospective studies are necessary to confirm these results and to prove the safety of cryochambers on a larger group of subjects. [ABSTRACT FROM AUTHOR]

Abstract Background The spatial ventricular gradient (SVG) is a vectorcardiographic measurement that reflects cardiac loading conditions via electromechanical coupling. Objectives We hypothesized that the SVG is correlated with right ventricular (RV) strain and is prognostic of adverse events in patients with acute pulmonary embolism (PE). Methods Retrospective, single‐center study of patients with acute PE. Electrocardiogram (ECG), imaging, and outcome data were obtained. SVG components were regressed on tricuspid annular plane systolic excursion (TAPSE), qualitative RV dysfunction, and RV/left ventricular (LV) ratio. Odds of adverse outcomes (30‐day mortality, vasopressor requirement, or advanced therapy) after PE were regressed on demographics, RV/LV ratios, traditional ECG signs of RV dysfunction, and SVG components using a logit model. Results ECGs from 317 patients (48% male, age 63.1 ± 16.6 years) with acute PE were analyzed; 36 patients (11.4%) experienced an adverse event. Worse RV hypokinesis, larger RV/LV ratio, and smaller TAPSE were associated with smaller SVG X and Y components, larger SVG Z components, and smaller SVG vector magnitude (p

Vectorcardiography (VCG) as an alternative form of 12-lead ECG is another method of measuring the electrical activity of the heart. The use of vectorcardiography in clinical practice is not common, but VCG leads can be derived from 12-lead ECG. VCG has proven to be a useful and more accurate tool for diagnosing various heart diseases within automated detection. This paper presents the application of four transformation methods namely: Kors regression, IDT, QLSV and Quasi-Orthogonal transformation to obtain a derived VCG. A total of 20 physiological and 20 records with the diagnosis of myocardial infarction were used. For physiological records, the Kors regression method achieved the best results in leads X and Y with relative deviation 99%. In lead Z, the QLSV method achieved the most accurate results with relative deviation 98% and percentage similarity >99%. For pathological records, the most accurate method in all leads was Kors regression with relative deviation 93% and percentage similarity >97%. From these results, there is the possibility of creating a new transformation method from the existing ones in order to obtain a more accurate transformation.

BackgroundWhile primarily a right heart disease, pulmonary arterial hypertension (PAH) can impact left heart function and aortic flow through a shifted interventricular septum from right ventricular pressure overload and reduced left ventricular preload, among other mechanisms. In this study, we used phase contrast (PC) MRI and a modest exercise challenge to examine the effects of PAH on systemic circulation. While exercise challenges are typically performed with ultrasound in the clinic, MRI exercise studies allow for more reproducible image alignment, more accurate flow quantification, and improved tissue contrast.MethodsSix PAH patients and fifteen healthy controls (8 older age-matched, 7 younger) exercised in the magnet bore with an MRI-compatible exercise device that allowed for scanning immediately following cessation of exercise. PC scans were performed in the ascending aorta during a breath hold immediately after modest exercise to non-invasively measure stroke volume (SV), cardiac output (CO), aortic peak systolic flow (PSF), and aortic wall stiffness via relative area change (RAC).ResultsImages following exercise showed mild blurring, but were high enough quality to allow for segmentation of the aorta. While SV was approximately 30% lower in PAH patients (SVPAH,rest = 67 ± 16 mL; SVPAH,stress = 90 ± 42 mL) than age-matched controls (SV,older,rest = 93 ± 16 mL; SVolder,stress = 133 ± 40 mL) at both rest and following exercise, CO was similar for both groups following exercise (COPAH,stress = 10.8 ± 5.7 L/min; COolder,stress = 11.8 ± 5.0 L/min). This was achieved through a compensatory increase in heart rate in the PAH subjects (74% increase as compared to 29% in age-matched controls). The PAH subjects also demonstrated reduced aortic peak systolic flow relative to the healthy controls (PSFPAH,rest = 309 ± 52 mL/s; PSFolder,rest = 416 ± 114 mL/s; PSFPAH,stress = 388 ± 113 mL/s; PSFolder,stress = 462 ± 176 mL/s). PAH patients and older controls demonstrated stiffer aortic walls when compared to younger controls (RACPAH,rest = 0.15 ± 0.05; RAColder,rest = 0.17 ± 0.05; RACyoung,rest = 0.28 ± 0.08).ConclusionsPC MRI following a modest exercise challenge was capable of detecting differences in left heart dynamics likely induced from PAH. These results demonstrated that PAH can have a significant influence on systemic flow, even when the patient has no prior left heart disease. Image quantification following exercise could likely be improved in future studies through the implementation of free-breathing or real-time MRI acquisitions.Trial registrationRetrospectively registered on 02/26/2018 (TRN: NCT03523910 ).

There are numerous sex-related differences in cardiac electrophysiology and arrhythmia propensity but very little knowledge about the reasons. Difference in body size has been proposed as one reason and was tested in this study of >20 cardiac electrophysiology parameters in 319 (158 women) apparently healthy 50- to 64-yr-old subjects from a randomly enrolled population sample, the pilot SCAPIS (Swedish Cardiopulmonary Bioimaging Study), using Frank vectorcardiography. We studied conventional conduction intervals, parameters reflecting electrical heterogeneity (dispersion) in the ventricles, QRS- and T-vector directions, spatial QRS-T angles, and T-vector loop morphology. Body surface area (BSA; 2 methods) and lean body mass (LBM), both estimated from body weight and height, were used as body size parameters. According to multivariable linear regression analysis adjusted for sex, there was no association between electrophysiological parameters and body size apart from QRS duration and QRSarea. In conclusion, most electrophysiological parameters assessed completely noninvasively and showing statistically significant differences between women and men on the group level show no association with BSA or LBM. Scaling (indexing) the electrophysiological parameters for body size parameters is therefore not an option. Consequently, the explanation for the sex-related electrophysiological differences should be sought along other lines. NEW & NOTEWORTHY We sought explanations for sex-related differences in >20 cardiac electrophysiology parameters including conventional conduction intervals in 319 (158 women) apparently healthy 50- to 64-yr-old subjects using Frank vectorcardiography, a novelty. Our hypothesis that body size was partly explanatory for such differences had to be refuted apart from QRS duration and QRSarea. Scaling (indexing) electrophysiological parameters for body size is therefore not an option and explanations for electrophysiological sex-related differences are to be sought elsewhere. [ABSTRACT FROM AUTHOR]

This paper deals with a wavelet-based algorithm for automatic detection of isoelectric coordinates of individual QRS loops of VCG record. Fiducial time instants of QRS peak, QRS onset, QRS end, and isoelectric PQ interval are evaluated on three VCG leads (X, Y, Z) together with global QRS boundaries of a record to spatiotemporal QRS loops alignment. The algorithm was developed and optimized on 161 VCG records of PTB diagnostic database of healthy control subjects (HC), patients with myocardial infarction (MI) and patients with bundle branch block (BBB) and validated on CSE multilead measurement database of 124 records of the same diagnostic groups. The QRS peak was evaluated correctly for all of 1,467 beats. QRS onset, QRS end were detected with standard deviation of 5,5 ms and 7,8 ms respectively from the referee annotation. The isoelectric 20 ms length PQ interval window was detected correctly between the P end and QRS onset for all the cases. The proposed algorithm complies the (2sCSE) limits for the QRS onset and QRS end detection and provides comparable or better results to other well-known algorithms. The algorithm evaluates well a wide QRS based on automated wavelet scale switching. The designed multi-lead approach QRS loop detector accomplishes diagnostic VCG processing, aligned QRS loops imaging and it is suitable for beat-to-beat variability assessment and further automatic VCG classification. [ABSTRACT FROM AUTHOR]

Theoretical grounds of integral vectors of ventricular depolarization and repolarization and their sum, i.e., the spatial ventricular gradient, have been studied. A systematic description and biophysical interpretation of these parameters are presented based on the distribution of cardiomyocyte action potential parameters in the inhomogeneous bidomain model of the myocardium. Recent medical studies have shown high efficiency and predictive value of the ventricular gradient, its constituents and related parameters, such as the angle between the con-stituents, the acceleration of repolarization, etc. Simple examples for a myocardial strip clarify the relationship between the action potential parameters and the resulting ventricular gradient. An explanation with graphic illustration is given for the very informative decartogram of repolarization acceleration. The results obtained here are useful in the modeling of vectorcardiograms for various pathological conditions of the heart ventricles and for various characteristics of the cardiomyocyte action potential, which determine its shape.

Objective: Vectorcardiography (VCG) as an alternative form of ECG provides important spatial information about the electrical activity of the heart. It achieves higher sensitivity in the detection of some pathologies such as myocardial infarction, ischemia and hypertrophy. However, vectorcardiography is not commonly measured in clinical practice, and for this reason mathematical transformations have been developed to obtain derived VCG leads, which in application in current systems and subsequent analysis can contribute to early diagnosis and obtaining other useful information about the electrical activity of the heart. Methods and procedures: The most frequently used transformation methods are compared, namely the Kors regression method, the Inverse Dower transformation, QLSV and the Quasi-orthogonal transformation. These transformation methods were used on 30 randomly selected records with a diagnosis of myocardial infarction from the Physikalisch-Technische Bundesanstalt (PTB) database and their accuracy was evaluated based on the calculation of the mean square error (MSE). MSE was subjected to statistical evaluation at a significance level of 0.05. Results: Based on statistical testing using the nonparametric multiselective Kruskall-Wallis test and subsequent post-hoc analysis using the Dunn method, the Kors regression as a whole method achieved the most accurate transformation. Conclusion: The results of statistical analysis provide an evaluation of the accuracy of several transformation methods for deriving orthogonal leads, for possible application in measuring and evaluation systems, which may contribute to the correct choice of method for subsequent analysis of electrical activity of the heart at orthogonal leads to predict various diseases.

Abnormal QRS-T angles are prognostic markers for cardiovascular deaths including sudden cardiac death. They occur in ∼5–6% of population-based cohorts but in ∼20% of patients with diabetes. The mechanistic background, electrical activation and/or recovery disturbances, is not known and the topic of this study. Applying Frank vectorcardiography (VCG) and simultaneously recorded scalar 12‑lead ECG, electrical activation and recovery of abnormal QRS-T angles were studied in 311 participants (5.4%) from a population-based cohort of 5796 women and men in the main Swedish CArdio-Pulmonary bio-Imaging Study (SCAPIS) in Gothenburg. Cut-off values for the peak and mean QRS-T angles were > 124° and > 119°, based on the >95th percentile among all 1080 participants in the pilot SCAPIS and reference values for normal directions (Q1-Q3) from 319 apparently healthy (30%) of them. Of 311 cases 17% had known cardiac disease. Deviations of QRS and QRSarea-vectors from reference limits (90%) were significantly more common than deviations of T- and Tarea-vectors (65%). Standard ECG signs suggested pathophysiology in 20%; left bundle branch block (LBBB) and voltage criteria for left ventricular hypertrophy being most frequent (9–10%) each. Sub-group analysis of the 30 with LBBB showed very large variability in vector directions. Our observations provide mechanistic insights about abnormal QRS-T angles of potential value for future prognostic and interventional studies. The results also have potential implications for LBB area pacing and the approach to left ventricular hypertrophy. • Abnormally wide QRS-T angles are strong predictors regarding all cardiac deaths. • Frank VCG defined whether they were due to activation and/or recovery alterations. • Activation alterations dominated in 311 cases out of altogether 5796 participants. • Only 17% had known cardiac disease and scalar ECG provided insights on pathophysiology in 20%. • These new observations provide mechanistic insights about abnormal QRS-T angles. [ABSTRACT FROM AUTHOR]

Background. The incidence of arterial hypertension continues to grow. By 2025 the number of patients will increase to 1.5 billion that makes it necessary to develop and implement effective approaches in the diagnosis and treatment of hypertension in practical health care. Aim. Evaluate the effectiveness of two-level diagnostics of left ventricular hypertrophy (LVH). Materials and methods. The distance of the first level of LVH diagnostics in outpatient departments with a territorial is more than 20 km. It was performed by remote electrocardiography, including medical examination of the population. Automatic conclusion of the devices was sent to the personal office of the functional diagnostics doctor. At the second level, the electrocardiograph software was used to convert ECG-12 into a vectorcardiogram (VKG) to clarify LVH. The ECG reports were returned to the device of the doctor/paramedic for further work with the patient. When using scalar ECG criteria for LVH, the most sensitive index was the SokolovLyon index 24.2% of cases, then the Cornell product 19.8% of cases. In the second level of ECG diagnostics, the sensitivity of the method in detecting LVH increased more than 3 times: in terms of the maximum loop vector modulus (M QRS 1.8 mV), 72%, the sensitivity of the total index Rx+Sz (2.7 mV) was 58% of cases, the deviation of the spatial angle QRS-T90 was 42.5%, the spatial area of the loop QRS (S QRSxyz 2.7 mV2), the area of the loop QRS in the horizontal plane (S QRSxz2.2 mV2) 41.5%, the orientation angle of the maximum loop vector t in the horizontal plane (angle Txz70) was detected in 38% of patients. These indicators were found with the same frequency in both groups of examined individuals. Conclusion. The use of remote two-level ECG and ECG diagnostics allowed to increase the detection of LVH in rural and urban populations by 3 times.

This paper deals with a wavelet-based algorithm for automatic detection of isoelectric coordinates of individual QRS loops of VCG record. Fiducial time instants of QRS peak, QRS onset, QRS end, and isoelectric PQ interval are evaluated on three VCG leads (X, Y, Z) together with global QRS boundaries of a record to spatiotemporal QRS loops alignment. The algorithm was developed and optimized on 161 VCG records of PTB diagnostic database of healthy control subjects (HC), patients with myocardial infarction (MI) and patients with bundle branch block (BBB) and validated on CSE multilead measurement database of 124 records of the same diagnostic groups. The QRS peak was evaluated correctly for all of 1,467 beats. QRS onset, QRS end were detected with standard deviation of 5,5 ms and 7,8 ms respectively from the referee annotation. The isoelectric 20 ms length PQ interval window was detected correctly between the P end and QRS onset for all the cases. The proposed algorithm complies the (2σCSE) limits for the QRS onset and QRS end detection and provides comparable or better results to other well-known algorithms. The algorithm evaluates well a wide QRS based on automated wavelet scale switching. The designed multi-lead approach QRS loop detector accomplishes diagnostic VCG processing, aligned QRS loops imaging and it is suitable for beat-to-beat variability assessment and further automatic VCG classification.

Application of the chronic thromboembolic pulmonary hypertension (CTEPH) rule out criteria (manual electrocardiogram [ECG] reading and N-terminal pro-brain natriuretic peptide [NTproBNP] test) can rule out CTEPH in pulmonary embolism (PE) patients with persistent dyspnea (InShape II algorithm). Increased pulmonary pressure may also be identified using automated ECG-derived ventricular gradient optimized for right ventricular pressure overload (VG-RVPO). A predefined analysis of the InShape II study was performed. The diagnostic performance of the VG-RVPO for the detection of CTEPH and the incremental diagnostic value of the VG-RVPO as new rule-out criteria in the InShape II algorithm were evaluated. 60 patients were included; 5 (8.3%) were ultimately diagnosed with CTEPH. The mean baseline VG-RVPO (at time of PE diagnosis) was −18.12 mV·ms for CTEPH patients and − 21.57 mV·ms for non-CTEPH patients (mean difference 3.46 mV·ms [95%CI −29.03 to 35.94]). The VG-RVPO (after 3–6 months follow-up) normalized in patients with and without CTEPH, without a clear between-group difference (mean Δ VG-RVPO of −8.68 and − 8.42 mV·ms respectively; mean difference of −0.25 mV·ms, [95%CI −12.94 to 12.44]). The overall predictive accuracy of baseline VG-RVPO, follow-up RVPO and Δ VG-RVPO for CTEPH was moderate to poor (ROC AUC 0.611, 0.514 and 0.539, respectively). Up to 76% of the required echocardiograms could have been avoided with VG-RVPO criteria replacing the InShape II rule-out criteria, however at cost of missing up to 80% of the CTEPH diagnoses. We could not demonstrate (additional) diagnostic value of VG-RVPO as standalone test or as on top of the InShape II algorithm. • The VG-RVPO improved over time after acute PE for CTEPH and non-CTEPH patients. • The VG-RVPO as a standalone test does not accurately discriminate CTEPH from non-CTEPH patients. • Additional diagnostic value of VG-RVPO on top of the InShape II algorithm could not be shown. • Our findings should be regarded as hypothesis generating due to low sample size. [ABSTRACT FROM AUTHOR]

Introduction: The changes in ventricular repolarization after cardiac resynchronization therapy (CRT) are poorly understood. This knowledge gap is addressed using a multimodality approach including electrocardiographic and echocardiographic measurements in patients and using patient‐specific computational modeling. Methods: In 33 patients electrocardiographic and echocardiographic measurements were performed before and at various intervals after CRT, both during CRT‐ON and temporary CRT‐OFF. T‐wave area was calculated from vectorcardiograms, and reconstructed from the 12‐lead electrocardiography (ECG). Computer simulations were performed using a patient‐specific eikonal model of cardiac activation with spatially varying action potential duration (APD) and repolarization rate, fit to a patient's ECG. Results: During CRT‐ON T‐wave area diminished within a day and remained stable thereafter, whereas QT‐interval did not change significantly. During CRT‐OFF T‐wave area doubled within 5 days of CRT, while QT‐interval and peak‐to‐end T‐wave interval hardly changed. Left ventricular (LV) ejection fraction only increased significantly increased after 1 month of CRT. Computer simulations indicated that the increase in T‐wave area during CRT‐OFF can be explained by changes in APD following chronic CRT that are opposite to the change in CRT‐induced activation time. These APD changes were associated with a reduction in LV dispersion in repolarization during chronic CRT. Conclusion: T‐wave area during CRT‐OFF is a sensitive marker for adaptations in ventricular repolarization during chronic CRT that may include a reduction in LV dispersion of repolarization. [ABSTRACT FROM AUTHOR]

Artificial intelligence (AI) aided cardiac arrhythmia (CA) classification has been an emerging research topic. Existing AI-based classification methods commonly analyze electrocardiogram (ECG) signals in lower dimensions, using one-dimensional (1D) temporal signals or two-dimensional (2D) images, which, however, may have limited capability in characterizing lead-wise spatiotemporal correlations, which are critical to the classification accuracy. In addition, existing methods mostly assume that the ECG data are linear temporal signals. This assumption may not accurately represent the nonlinear, nonstationary nature of the cardiac electrophysiological process. In this work, we have developed a three-dimensional (3D) recurrence plot (RP)-based deep learning algorithm to explore the nonlinear recurrent features of ECG and Vectorcardiography (VCG) signals, aiming to improve the arrhythmia classification performance. The 3D ECG/VCG images are generated from standard 12 lead ECG and 3 lead VCG signals for neural network training, validation, and testing. The superiority and effectiveness of the proposed method are validated by various experiments. Based on the PTB-XL dataset, the proposed method achieved an average F1 score of 0.9254 for the 3D ECG-based case and 0.9350 for the 3D VCG-based case. In contrast, recently published 1D and 2D ECG-based CA classification methods yielded lower average F1 scores of 0.843 and 0.9015, respectively. Thus, the improved performance and visual interpretability make the proposed 3D RP-based method appealing for practical CA classification. [ABSTRACT FROM AUTHOR]

BACKGROUND: Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) carries a risk of sudden death. We aimed to assess whether vectorcardiographic (VCG) parameters directed toward the right heart and a measured angle of the S-wave would help differentiate ARVD/C with otherwise normal electrocardiograms from controls. METHODS: Task Force 2010 definite ARVD/C criteria were met for all patients. Those who did not fulfill Task Force depolarization or repolarization criteria (-ECG) were compared with age and gender-matched control subjects. Electrocardiogram measures of a 3-dimentional spatial QRS-T angle, a right-precordial-directed orthogonal QRS-T (RPD) angle, a root mean square of the right sided depolarizing forces (RtRMS-QRS), QRS duration (QRSd) and the corrected QT interval (QTc), and a measured angle including the upslope and downslope of the S-wave (S-wave angle) were assessed. RESULTS: Definite ARVD/C was present in 155 patients by 2010 Task Force criteria (41.7 ± 17.6 years, 65.2% male). -ECG ARVD/C patients (66 patients) were compared to 66 control patients (41.7 ± 17.6 years, 65.2% male). All parameters tested except the QRSd and QTc significantly differentiated -ECG ARVD/C from control patients (p

Vectorcardiography (VCG) as an alternative form of 12-lead ECG is another method of measuring the electrical activity of the heart. The use of vectorcardiography in clinical practice is not common, but VCG leads can be derived from 12-lead ECG. VCG has proven to be a useful and more accurate tool for diagnosing various heart diseases within automated detection. This paper presents the application of four transformation methods namely: Kors regression, IDT, QLSV and Quasi-Orthogonal transformation to obtain a derived VCG. A total of 20 physiological and 20 records with the diagnosis of myocardial infarction were used. For physiological records, the Kors regression method achieved the best results in leads X and Y with relative deviation < 1%, correlation and percentage similarity > 99%. In lead Z, the QLSV method achieved the most accurate results with relative deviation < 1%, correlation > 98% and percentage similarity > 99%. For pathological records, the most accurate method in all leads was Kors regression with relative deviation < 2.2%, correlation > 93% and percentage similarity > 97%. From these results, there is the possibility of creating a new transformation method from the existing ones in order to obtain a more accurate transformation. [ABSTRACT FROM AUTHOR]

The ST-segment elevation myocardial infarction (STEMI) paradigm requires ST-segment elevation (STE) in contiguous leads on electrocardiography (ECG). STEMI criteria overlook numerous patients with acute coronary occlusion (ACO). The Aslanger pattern describes an ECG without contiguous STE, indicating acute inferior occlusion myocardial infarction (OMI) with concomitant multi-vessel disease. We describe one case of inferior OMI with one STE in lead III on initial ECG; however acute inferior STEMI was later identified. Coronary angiography showed thrombosis in the proximal right coronary artery and severe stenosis in non-infarct-related arteries. Awareness of the limitations of current STEMI criteria is crucial for timely intervention. [ABSTRACT FROM AUTHOR]

Objective: Bundle Branch Block (BBB) is the most serious asymptomatic, cardiovascular complication caused due to obstruction or delay across the pathways of electrical signals. Vectorcardiography (VCG) is the most useful method for measuring heart activities, containing information about the different physiological states of the heart. It is a powerful tool for detecting blockage inside the lower chamber of the heart. Clinically, posterior sensing electrodes are used to record VCG signals. Manual inspection of BBB-induced VCG changes is a time-consuming, labor-intensive, and error-prone procedure. This is the first work that integrates a deep learning technique with S-T spectrograms of smoothed VCG signals for the accurate diagnosis of BBB. A novel filter-fusion technique has also been proposed, to remove the various artifacts from the signals, which considerably increased the BBB diagnosis performance. Methods: VCG signals are divided into fragments of 4- ${s}$. A newly introduced filter-fusion technique is utilized to remove baseline wander and smooth the signal. Stock-well transform (S-T) is applied to extract spectrograms from de-noised smoothed VCG fragments. Obtained S-T spectrograms are fed to pre-trained Alex-Net, Squeeze-Net, and a newly developed less complex deep learning model with data augmentation technique utilizing a 10-fold cross-validation scheme. Results: Proposed improved deep learning model (IDLM) yielded the highest detection accuracy of 98.80%, true positive rate of 98.74%, and true negative rate of 98.80%. Conclusion: The findings show that developed DLM is computationally fast and efficient than benchmark models. The proposed IDLM is available for testing with other datasets. [ABSTRACT FROM AUTHOR]

BACKGROUND: Patients with tetralogy of Fallot (TOF) have increased risk of atrial arrhythmias. HYPOTHESIS: A measure of atrial dispersion, the P-wave vector magnitude (Pvm), can identify patients at risk for perioperative atrial flutter (AFL) or intra-atrial re-entrant tachycardia (IART) in a large TOF cohort. METHODS: We performed a blinded, retrospective analysis of 158 TOF patients undergoing pulmonary valve replacement between 1997 and 2015. History of AFL/IART was documented using electrocardiogram, Holter monitor, exercise stress test, implanted cardiac device, and electrophysiology study. P-R intervals, Pvm, QRS duration, and QRS vector magnitude were assessed from resting sinus-rhythm 12-lead electrocardiograms and identification of those with AFL/IART was determined. RESULTS: Fourteen patients (8.9%) were found to have AFL/IART. Pvm, QRS duration, and QRS vector magnitude significantly differentiated those with AFL/IART from those without on univariate analysis: 0.09 ± 0.04 vs 0.18 ± 0.07 mV, 161.3 ± 21.9 vs 137.7 ± 31.4 ms, and 1.2 (interquartile range, 1.0-1.2) vs 1.6 mV (1.0-2.3), respectively (P < 0.05 for each). The Pvm had the highest area under the ROC curve (0.88) and was the only significant predictor on multivariate analysis, with odds ratio of 0.02 (95% confidence interval: 0.01-0.53). P-R duration, MRI volumes, and right-heart hemodynamics did not significantly differentiate those with vs those without AFL/IART. CONCLUSIONS: In TOF patients undergoing pulmonary valve replacement, Pvm has significant value in predicting those with perioperative AFL/IART. These clinical features may help further evaluate TOF patients at risk for perioperative atrial arrhythmias. Prospective studies are warranted.

Vectorcardiography (VCG) is another useful method that provides us with useful spatial information about the electrical activity of the heart. The use of vectorcardiography in clinical practice is not common nowadays, mainly due to the well-established 12-lead ECG system. However, VCG leads can be derived from standard 12-lead ECG systems using mathematical transformations. These derived or directly measured VCG records have proven to be a useful tool for diagnosing various heart diseases such as myocardial infarction, ventricular hypertrophy, myocardial scars, long QT syndrome, etc., where standard ECG does not achieve reliable accuracy within automated detection. With the development of computer technology in recent years, vectorcardiography is beginning to come to the forefront again. In this review we highlight the analysis of VCG records within the extraction of functional parameters for the detection of heart disease. We focus on methods of processing VCG functionalities and their use in given pathologies. Improving or combining current or developing new advanced signal processing methods can contribute to better and earlier detection of heart disease. We also focus on the most commonly used methods to derive a VCG from 12-lead ECG. [ABSTRACT FROM AUTHOR]

OBJECTIVE: The frontal plane QRS-T [f(QRS-T)] angle refers to the mean difference between the depolarization and repolarization vectors and can easily be measured by digital electrocardiography (ECG). Pacemaker leads can cause fibrosis of the myocardium adjacent to the electrode-tissue interface. We aimed to evaluate whether a right ventricular implantable cardioverter-defibrillator (ICD) lead modifies the f(QRS-T) angle in patients with systolic heart failure (HF). PATIENTS AND METHODS: We prospectively analyzed 101 systolic HF patients who underwent single- lead ICD implantation. The f(QRS) angle before and after ICD implantation was compared with the Wilcoxon signed-rank test. RESULTS: No significant difference in the f(QRS-T) angle was observed before and 6 months after ICD implantation (89.5° ± 97.8° vs. 93.0° ± 90.3°, p=0.211). CONCLUSIONS: Histopathological studies showed that the irritating effect of ICD leads may cause fibrosis and scar tissue. However, we found that fibrosis and scar tissue did not affect the f(QRS-T) angle, which suggests that these pathologies may not have clinical significance. Further studies on the f(QRS-T) angle are warranted to understand its clinical significance in ICD-induced local fibrosis. [ABSTRACT FROM AUTHOR]

The 12-lead electrocardiogram is a key component of cardiac screening in elite adolescent footballers. Current technology hampers mobile electrocardiogram monitoring that could reduce the time-to-diagnosis in symptomatic athletes. Recently, a 22-lead mobile electrocardiogram monitor, CardioSecur (Personal MedSystems GmbH), has been approved for use in adults. In this study, the differences in parameter accuracy between CardioSecur's 22-lead electrocardiogram and the gold standard 12-lead electrocardiogram were assessed in elite adolescent footballers (n=31) using Bland-Altman and paired t -tests/Wilcoxon analysis. Agreement between the two devices was clinically acceptable for heart rate (bias=− 0.633 bpm), PR Interval (bias=− 1.73 ms), Bazzett's corrected QTc interval (bias=2.03 ms), T-wave axis (bias=6.55°), P-wave duration (bias=− 0.941 ms), Q-wave amplitude (bias=0.0195 mV), Q-wave duration (bias=1.98 ms), rhythm (bias=0.0333), ST-segment (bias=− 0.0629), J-point analysis (bias=− 0.01) and extended T wave and QRS duration analysis. Unsatisfactory agreement was observed in QRS axis (bias=− 19.4°), P-wave axis (bias=− 0.670°), QRS amplitude (bias=− 0.660 mV), P-wave amplitude (bias=0.0400 mV) and T-wave amplitude (bias=− 0.0675 mV). CardioSecur's 22-lead electrocardiogram agrees with the gold standard in rhythm, durations, T-wave determination in all leads assessed, permitting its use in adolescent footballers for immediate pitch- or track-side analysis. [ABSTRACT FROM AUTHOR]

Background: QRS area, a three‐dimensional QRS complex, is a novel vectorcardiography method of measuring the magnitude of electrical forces in the heart. Hypothetically, a greater QRS area denotes higher dyssynchrony and indicates potential benefits from cardiac resynchronization therapy (CRT). Previous studies suggest a positive correlation between QRS area and the degree of response to CRT, but its clinical use remains unclear. We performed a meta‐analysis of the relationship between QRS area and survival benefit following CRT. Methods: We comprehensively searched the MEDLINE, EMBASE, and Cochrane databases from inception to August 2021. We included studies with prospective and retrospective cohort designs that reported QRS area before CRT and total mortality. Data from each study were analyzed using a random‐effects model. The results were reported as a hazard ratio (HR) and 95% confidence intervals. Results: Five observational studies including 4931 patients were identified. The cut‐off values between large and small QRS areas ranged from 102 to 116 μVs. Our analysis showed a larger QRS area was statistically associated with increased 5‐year survival in patients implanted with CRT (HR pooled 0.48, 95% CI 0.46–0.51, I2 = 54%, p <.0001). Greater QRS area reduction (pre‐ and post‐implantation) were associated with a lower total mortality rate (HR pooled 0.45, 95% CI 0.38–0.52, I2 = 0%, p <.0001). Conclusion: Larger pre‐implantation QRS area was associated with increased survival after CRT. QRS area reduction following CRT implantation was also associated with lower mortality. QRS area may potentially become an additional selection criterion for CRT implantations. [ABSTRACT FROM AUTHOR]

Background: Patients with atrial septal defects and pulmonary hypertension would benefit from early identification and treatment of pulmonary hypertension prior to closure. Noninvasive screening tools for pulmonary hypertension are inadequate. Electrocardiography, though readily available, has so far been of limited screening utility in patients with pulmonary hypertension. We hypothesize that derived vectorcardiographic parameters will aid in identifying increased right ventricular afterload and thus provide an additional screening tool for pulmonary hypertension in patients with secundum atrial septal defects.Objective: Establish whether vectorcardiography can be used to screen for pulmonary hypertension.Methods: A retrospective review of patients with secundum atrial septal defects (ASD) who underwent cardiac catheterization at the University of Minnesota from 2012 to 2020 was performed. We excluded patients with other congenital heart diagnoses, insufficient hemodynamic data, or lacking sinus rhythm electrocardiogram at time of cardiac catheterization. Parameters analyzed included: Sokolow-Lion right ventricular hypertrophy criteria, PR duration, QRS duration, corrected QT intervals, QRS and T wave frontal plane axes, rSR', R' amplitude, as well as vectorcardiographic parameters (Kors regression-related method), the QRS vector magnitude, T wave vector magnitude, and the spatial QRS-T angle. These were compared to measures of pulmonary hypertension obtained at cardiac catheterization.Results: The spatial QRS-T angle significantly differentiated ASD patients with pulmonary hypertension (median 104 degrees, interquartile range 55-137 degrees) from ASD patients without pulmonary hypertension (median 37 degrees, interquartile range 21-63 degrees, p-value of 0.002). At a cut-off of 124 degrees, the positive and negative predictive values for identification of pulmonary hypertension were 36.4% and 96.4%, respectively, with an odds ratio of 13.4 (95% confidence interval of 2.9 to 63.7). The positive predictive value was significantly improved when combined with echocardiographic data to screen for pulmonary hypertension.Conclusion: The spatial QRS-T angle is associated with pulmonary hypertension in patients with secundum atrial septal defects. [ABSTRACT FROM AUTHOR]

Cardiac resynchronization therapy (CRT) is a good treatment for heart failure accompanied by ventricular conduction abnormalities. Current ECG criteria in international guidelines seem to be suboptimal to select heart failure patients for CRT. The criteria QRS duration and left bundle branch block (LBBB) QRS morphology insufficiently detect left ventricular activation delay, which is required for benefit from CRT. Additionally, there are various definitions for LBBB, in which each one has a different association with CRT benefit and is prone to subjective interpretation. Recent studies have shown that the objectively measured vectorcardiographic QRS area identifies left ventricular activation delay with higher accuracy than any of the current ECG criteria. Indeed, various studies have consistently shown that a high QRS area prior to CRT predicts both echocardiographic and clinical improvement after CRT. The beneficial relation of QRS area with CRT-outcome was largely independent from QRS morphology, QRS duration, and patient characteristics known to affect CRT-outcome including ischemic etiology and sex. On top of QRS area prior to CRT, the reduction in QRS area after CRT further improves benefit. QRS area is easily obtainable from a standard 12-lead ECG though it currently requires off-line analysis. Clinical applicability will be significantly improved when QRS area is automatically determined by ECG equipment. [ABSTRACT FROM AUTHOR]

Background: Women seem to derive more benefit from cardiac resynchronization therapy (CRT) than men, even after accounting for the higher burden of risk factors for nonresponse often observed in men. Objective: To assess for sex-specific differences in left ventricular (LV) electrical dyssynchrony as a contributing electrophysiological explanation for the greater degree of CRT benefit among women. Methods: We compared the extent of baseline LV electrical dyssynchrony, as measured by the QRS area (QRSA), among men and women with left bundle branch block (LBBB) undergoing CRT at Duke University (n = 492, 35% women) overall and in relation to baseline QRS characteristics using independent sample t tests and Pearson correlation coefficients. Cox regression analyses were used to relate sex, QRSA, and QRS characteristics to the risk of cardiac transplantation, LV assist device implant, or death. Results: Although the mean QRS duration (QRSd) did not differ by sex, QRSA was greater for women vs men (113.8 μVs vs 98.2 μVs, P < .001), owing to differences in the QRSd

Vectorcardiography (VCG) is another useful method that provides us with useful spatial information about the electrical activity of the heart. The use of vectorcardiography in clinical practice is not common nowadays, mainly due to the well-established 12-lead ECG system. However, VCG leads can be derived from standard 12-lead ECG systems using mathematical transformations. These derived or directly measured VCG records have proven to be a useful tool for diagnosing various heart diseases such as myocardial infarction, ventricular hypertrophy, myocardial scars, long QT syndrome, etc., where standard ECG does not achieve reliable accuracy within automated detection. With the development of computer technology in recent years, vectorcardiography is beginning to come to the forefront again. In this review we highlight the analysis of VCG records within the extraction of functional parameters for the detection of heart disease. We focus on methods of processing VCG functionalities and their use in given pathologies. Improving or combining current or developing new advanced signal processing methods can contribute to better and earlier detection of heart disease. We also focus on the most commonly used methods to derive a VCG from 12-lead ECG.

Background: QRS duration and morphology including left bundle branch block (LBBB) are the most widely used electrocardiogram (ECG) markers for assessing ventricular dyssynchrony and predicting heart failure (HF). However, the vectorcardiographic QRS area may more accurately identify delayed left ventricular activation and HF development.Objective: We investigated the association between QRS area and incident HF risk in patients with LBBB.Methods: By crosslinking data from Danish nationwide registries, we identified patients with a first-time digital LBBB ECG between 2001 and 2015. The vectorcardiographic QRS area was derived from a 12‑lead ECG using the Kors transformation method and grouped into quartiles. The endpoint was a composite of HF diagnosis, filled prescriptions for loop diuretics, or death from HF. Cause-specific multivariable Cox regression was used to compute hazard ratios(HR) with 95% confidence intervals(CI).Results: We included 3316 patients with LBBB free from prior HF-related events (median age, 72 years; male, 40%). QRS area quartiles comprised Q1, 36-98 μVs; Q2, 99-119 μVs; Q3, 120-145 μVs; and Q4, 146-295 μVs. During a 5-year follow-up, 31% of patients reached the composite endpoint, with a rate of 39% in the highest quartile Q4. A QRS area in quartile Q4 was associated with increased hazard of the composite endpoint (HR:1.48, 95%CI:1.22-1.80) compared with Q1.Conclusions: Among primary care patients with newly discovered LBBB, a large vectorcardiographic QRS area (146-295 μVs) was associated with an increased risk of incident HF diagnosis, filling prescriptions for loop diuretics, or dying from HF within 5-years. [ABSTRACT FROM AUTHOR]

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 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 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

Background: One of the most common cardiovascular diseases (CVDs) in the world is myocardial infarction (MI). By analyzing electrocardiogram and vectorcardiography (VCG) signals, it is possible to identify and characterize heart diseases such as MI. One of the new methods of detection is the use of spatio-temporal parameters of VCG signals. This study aimed to correctly distinguish healthy signals from patients, achieve acceptable accuracy, and show the benefits of VCG and its application as a method to cover the shortcoming of electrocardiography. Methods: In this study, in addition to applying electrocardiogram signals in the time domain, spatio-temporal patterns of VCG signals were used to identify 80 patients with MI, and differentiate them from 80 healthy individuals. Findings: When combining the 12-lead electrocardiography (ECG) and the 3-lead VCG features applied to the Feedforward Neural Network classifier input, an accuracy of 91.2%, specificity of 92.6%, and specificity of 90% were obtained. The results were in higher values than when applied separately. Conclusion: The observations indicate that combined ECG and VCG methods can be effective in distinguishing MI cases from healthy cases. It is hoped that this method may be useful in the clinical evaluation and heart failure diagnosis.

Abstract Background The risk of sudden cardiac death (SCD) is known to be dynamic. However, the accuracy of a dynamic SCD prediction is unknown. We aimed to measure the dynamic predictive accuracy of ECG biomarkers of SCD and competing non-sudden cardiac death (non-SCD). Methods Atherosclerosis Risk In Community study participants with analyzable ECGs in sinus rhythm were included (n = 15,716; 55% female, 73% white, age 54.2 ± 5.8 y). ECGs of 5 follow-up visits were analyzed. Global electrical heterogeneity and traditional ECG metrics (heart rate, QRS, QTc) were measured. Adjudicated SCD was the primary outcome; non-SCD was the competing outcome. Time-dependent area under the receiver operating characteristic curve (ROC(t) AUC) analysis was performed to assess the prediction accuracy of a continuous biomarker in a period of 3,6,9 months, and 1,2,3,5,10, and 15 years using a survival analysis framework. Reclassification improvement as compared to clinical risk factors (age, sex, race, diabetes, hypertension, coronary heart disease, stroke) was measured. Results Over a median 24.4 y follow-up, there were 577 SCDs (incidence 1.76 (95%CI 1.63–1.91)/1000 person-years), and 829 non-SCDs [2.55 (95%CI 2.37–2.71)]. No ECG biomarkers predicted SCD within 3 months after ECG recording. Within 6 months, spatial ventricular gradient (SVG) elevation predicted SCD (AUC 0.706; 95%CI 0.526–0.886), but not a non-SCD (AUC 0.527; 95%CI 0.303–0.75). SVG elevation more accurately predicted SCD if the ECG was recorded 6 months before SCD (AUC 0.706; 95%CI 0.526–0.886) than 2 years before SCD (AUC 0.608; 95%CI 0.515–0.701). Within the first 3 months after ECG recording, only SVG azimuth improved reclassification of the risk beyond clinical risk factors: 18% of SCD events were reclassified from low or intermediate risk to a high-risk category. QRS-T angle was the strongest long-term predictor of SCD (AUC 0.710; 95%CI 0.668–0.753 for ECG recorded within 10 years before SCD). Conclusion Short-term and long-term predictive accuracy of ECG biomarkers of SCD differed, reflecting differences in transient vs. persistent SCD substrates. The dynamic predictive accuracy of ECG biomarkers should be considered for competing SCD risk scores. The distinction between markers predicting short-term and long-term events may represent the difference between markers heralding SCD (triggers or transient substrates) versus markers identifying persistent substrate.

To localize the unusual cardiac activities non-invasively, one has to build a prior forward model that relates the heart, torso, and detectors. This model has to be constructed to mathematically relate the geometrical and functional activities of the heart. Several methods are available to model the prior sources in the forward problem, which results in the lead field matrix generation. In the conventional technique, the lead field assumed the fixed prior sources, and the source vector orientations were presumed to be parallel to the detector plane with the unit strength in all directions. However, the anomalies cannot always be expected to occur in the same location and orientation, leading to misinterpretation and misdiagnosis. To overcome this, the work proposes a new forward model constructed using the VCG signals of the same subject. Furthermore, three transformation methods were used to extract VCG in constructing the time-varying lead fields to steer to the orientation of the source rather than just reconstructing its activities in the inverse problem. In addition, the unit VCG loop of the acute ischemia patient was extracted to observe the changes compared to the normal subject. The abnormality condition was achieved by delaying the depolarization time by 15ms. The results involving the unit vectors of VCG demonstrated the anisotropic nature of cardiac source orientations, providing information about the heart's electrical activity., (Creative Commons Attribution license.)