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Congenital short QT syndrome is a very low prevalence inherited primary arrhythmia syndrome first reported in 2000 by Gussak et al., who described two families with a short QT interval, syncope, and sudden cardiac death. In 2004, Ramon Brugada et al. identified the first genetic type of this entity. To date, a total of nine genotypes have been described. The diagnosis is easy from the electrocardiogram (ECG), not only due to the short QT duration, but also based on other aspects covered in this review. During 24-h Holter monitoring, paroxysmal atrial fibrillation spontaneously converting to sinus rhythm may be found. Even though the T wave may appear symmetric on the ECG, the T loop of the vectorcardiogram confirms that the T wave is constantly asymmetric due to the presence of dashes closer to each other in the efferent branch. In this review, we also describe the minus-plus T wave sign that we have described in a previously published article. In addition to congenital causes, we briefly highlight the existence of numerous acquired causes of short QT interval. [ABSTRACT FROM AUTHOR]

Background: The electrocardiogram (ECG) is a powerful tool for differential diagnosis among a group of pathologies with different therapeutic approaches/prognoses, the so-called J-wave syndrome. The vectorcardiogram (VCG) can be used as a complementary method to the ECG in several dubious electrocardiographic alterations.Objective: We carried out a VCG analysis after conceiving and measuring a novel parameter (JT-distance) that allows diagnosis of the Brugada ECG pattern.Methods: A retrospective cohort study selected ninety-six ECGs with J-point elevation in V1/V2, ECG superior leads and VCGs, all performed on the same day. A new VCG measurement by Frank method (JT-distance) was conceived and designed in transverse and right sagittal planes by 3 lines drawn 1) at the final third of the QRS loop, comprehending the J-point; 2) at the initial portion of the T loop; 3) a parallel of the J-point line at the beginning of the T loop. JT measure was determined by the distance between parallels. A validation cohort was established in a new sample of thirty-five patients.Results: JT-distance ≥1.5 mm (tranverse plane) and JT-distance >1.25 mm, in the sagittal plane, differentiated Brugada type-1 from Brugada type-2, early repolarization and others, with 95% sensitivity and 68% specificity. JT-distance <1.5 mm (transverse plane) and JT >1.25 mm (sagittal plane) had 100% sensitivity and 85% specificity for Brugada type-1 diagnosis. A validation cohort showed very similar Cohen's kappa levels (0.65 and 0.77, test and validation cohorts, respectively), with overlapping 95% confidence intervals.Conclusions: The novel vectorcardiogram measurement (JT-distance) presented a new diagnostic criterion to identify Brugada pattern. Nevertheless, prospective studies should be performed by other centers to confirm these findings. [ABSTRACT FROM AUTHOR]

Objective: Vectorcardiographic (VCG) global electrical heterogeneity (GEH) metrics showed clinical usefulness. We aimed to assess the reproducibility of GEH metrics.Methods: GEH was measured on two 10-s 12‑lead ECGs recorded on the same day in 4316 participants of the Multi-Ethnic Study of Atherosclerosis (age 69.4 ± 9.4 y; 2317(54%) female, 1728 (40%) white, 1138(26%) African-American, 519(12%) Asian-American, 931(22%) Hispanic-American). GEH was measured on a median beat, comprised of the normal sinus (N), atrial fibrillation/flutter (S), and ventricular-paced (VP) beats. Spatial ventricular gradient's (SVG's) scalar was measured as sum absolute QRST integral (SAIQRST) and vector magnitude QT integral (VMQTi).Results: Two N ECGs with heart rate (HR) bias of -0.64 (95% limits of agreement [LOA] -5.68 to 5.21) showed spatial area QRS-T angle (aQRST) bias of -0.12 (95%LOA -14.8 to 14.5). Two S ECGs with HR bias of 0.20 (95%LOA -15.8 to 16.2) showed aQRST bias of 1.37 (95%LOA -33.2 to 35.9). Two VP ECGs with HR bias of 0.25 (95%LOA -3.0 to 3.5) showed aQRST bias of -1.03 (95%LOA -11.9 to 9.9). After excluding premature atrial or ventricular beat and two additional beats (before and after extrasystole), the number of cardiac beats included in a median beat did not affect the GEH reproducibility. Mean-centered log-transformed values of SAIQRST and VMQTi demonstrated perfect agreement (Bias 0; 95%LOA -0.092 to 0.092).Conclusion: GEH measurements on N, S, and VP median beats are reproducible. SVG's scalar can be measured as either SAIQRST or VMQTi.Significance: Satisfactory reproducibility of GEH metrics supports their implementation. [ABSTRACT FROM AUTHOR]

The outcome in the Brugada syndrome (BrS) is more benign in female than in male individuals. However, outcome could be adversely affected by sinus node dysfunction (SND). Long sinus pauses indicate an overlap between the phenotypes of BrS and SND. We present a 29-year-old woman with syncopal episodes at rest since adolescence. [ABSTRACT FROM AUTHOR]

Electrocardiographic (ECG) and vectorcardiographic (VCG) analyses are used to diagnose current cardiovascular disease and for risk stratification for future adverse cardiovascular events. With increasing use of digital ECGs, research into novel ECG/VCG parameters has increased, but widespread computer-based ECG/VCG analysis is limited because there are no currently available, open-source, and easily customizable software packages designed for automated and reproducible analysis. We present BRAVEHEART, an open-source, modular, customizable, and easy to use software package implemented in the MATLAB programming language, for scientific analysis of standard 12-lead ECGs acquired in a digital format. BRAVEHEART accepts a wide variety of digital ECG formats and provides complete and automatic ECG/VCG processing with signal denoising to remove high- and low-frequency artifact, non-dominant beat identification and removal, accurate fiducial point annotation, VCG construction, median beat construction, customizable measurements on median beats, and output of measurements and results in numeric and graphical formats. The BRAVEHEART software package provides easily customizable scientific analysis of ECGs and VCGs. We hope that making BRAVEHART available will allow other researchers to further the field of ECG/VCG analysis without having to spend significant time and resources developing their own ECG/VCG analysis software and will improve the reproducibility of future studies. Source code, compiled executables, and a detailed user guide can be found at http://github.com/BIVectors/BRAVEHEART. The source code is distributed under the GNU General Public License version 3. • BRAVEHEART is open-source software for processing electrocardiograms (ECGs) and vectorcardiograms (VCGs) for research purposes. • BRAVEHEART provides complete and automatic ECG/VCG processing with output of measurements in numeric and graphical formats. • BRAVEHEART's modular design allows easy addition of new ECG formats or ECG/VCG measurements with minimal need for coding. • Large ECG datasets can be processed automatically in parallel, and poor quality ECGs can be flagged for review. • Source code and documentation are available at http://github.com/BIVectors/BRAVEHEART under the GNU GPL version 3. [ABSTRACT FROM AUTHOR]

Background: Many variants of the spatial QRS-T angle (QRS-Ta) are in use. We aimed to identify the best QRS-Ta for all-cause mortality prediction among different variants.Methods: 6667 individuals from the Inter99 General Population Study were followed for a median of 12.7 years. Vectorcardiograms were calculated using the Kors and Inverse Dower matrices. The QRS-Ta was calculated using both mean and peak vectors of the QRS- and T-loops. Hazard ratios (HR) for abnormal QRS-Tas were calculated using a Cox's Proportional Hazard Model.Results: The highest HR and largest AUC for all-cause mortality was obtained with the Kors matrix and the mean vector (HR = 2.2, 95% confidence interval: [1.38;3.43] p < 0.001, in men). There was interaction with the orientation of the QRS-T plane.Conclusion: For optimal prediction of all-cause mortality, the mean vectors in the QRS- and T-loops of the Kors-derived vectorcardiogram should be used. QRS-T plane orientation affects mortality prediction. [ABSTRACT FROM AUTHOR]

Aims: To objectively characterize and mathematically justify the observation that vectorcardiographic QRS loops in normal individuals are more planar than those from patients with ST elevation myocardial infarction (STEMI).Methods: Vectorcardiograms (VCGs) were constructed from three simultaneously recorded quasi-orthogonal leads, I, aVF and V2 (sampled at 1000 samples/s). The planarity of these QRS loops was determined by fitting a surface to each loop. Goodness of fit was expressed in numerical terms.Results: 15 healthy individuals aged 35-65years (73% male) and 15 patients aged 45-70years (80% male) with diagnosed acute STEMI were recruited. The spatial-QRS loop was found to lie in a plane in normal controls. In STEMI patients, this planarity was lost. Calculation of goodness of fit supported these visual observations.Conclusions: The degree of planarity of the VCG loop can differentiate healthy individuals from patients with STEMI. This observation is compatible with our basic understanding of the electrophysiology of the human heart. [ABSTRACT FROM AUTHOR]

The purpose of this study was to develop optimal configuration of adhesive ECG patches placement on the torso, which would provide the best agreement with the Frank orthogonal ECGs. Ten seconds of orthogonal ECG followed by 3-5min of ECGs using patches at 5 different locations simultaneously on the torso were recorded in 50 participants at rest in sitting position. Median beat was generated for each ECG and 3 patch ECGs that best correlate with orthogonal ECGs were selected for each participant. For agreement analysis, spatial QRS-T angle, spatial QRS and T vector characteristics, spatial ventricular gradient, roundness, thickness and planarity of vectorcardiographic (VCG) loops were measured. Key VCG parameters showed high agreement in Bland-Altman analysis (spatial QRS-T angle on 3-patch ECG vs. Frank ECG bias 0.3 (95% limits of agreement [-6.23;5.71 degrees]), Lin's concordance coefficient=0.996). In conclusion, newly developed orthogonal 3-patch ECG can be used for long-term VCG monitoring. [ABSTRACT FROM AUTHOR]

Background: Intra-abdominal hypertension (IAH) impairs cardiovascular function, however an effect of IAH on cardiac electrophysiology has been poorly documented. The aim of this study was to evaluate the effect of IAH following pneumoperitoneum on vectorcardiographic variables reflecting cardiac repolarisation and depolarisation.Methods: Otherwise healthy women undergoing elective gynaecological laparoscopy were studied. Intra-abdominal pressure (IAP), spatial QRS-T angle and ST-segment J-point (STJ) were observed during surgery and the early postoperative period.Results: Forty women, ages 22 to 43 were examined. Induction of IAH to 15mmHg significantly widened the spatial QRS-T angle, whereas the Trendelenburg position subsequently reduced this widening. IAH also increased STJ voltage in leads III, aVF, V2 and V3 during surgery, with increased STJ voltage persisting in several leads through the morning of postoperative day 1.Conclusion: Induction of IAH impacts the relationship between cardiac depolarisation and repolarisation and increases spatial QRS-T angle and STJ voltage. [ABSTRACT FROM AUTHOR]

The detection of proarrhythmic effects of many current drugs has prompted the search for complementary non-invasive markers of cardiotoxicity risk. Indices based on studies of cardiac vector dynamics have emerged. We use quaternions to quantify symmetry changes in cardiac vector velocity during ventricular repolarization, which could signal the arrhythmia risk. Principal component analysis is used to homogenize the information and reduce the space to three dimensions. A comparison with the ratio of normalized areas of the repolarization loop (T-wave) and two standard measurements was made: QT and T peak-end intervals. Assessment was conducted by comparing 52 healthy subjects with patients undergoing treatment with Sotalol: 7 recordings with Torsade de Pointes events and 15 without arrhythmic effects. Significant differences (p ¡ 5E-4) were found in both phases of repolarization in terms of absolute velocities and areas. The ratio between the maximums of each parameter in both halves of the T-wave showed a trend towards 1 in the proximity of an arrhythmic event. Angular velocity ratios reached a sensitivity/specificity pair of 100 (95%CI: 59–100)/90 (95%CI: 79–97) with an AUC of 98.6 (95%CI: 95.7–100) in the comparison of healthy population with at-risk patients. Linear discriminant analysis improved the classification by reaching sensitivity and specificity values of 100 (95%CI: 59–100) and 96 (5%CI: 87–100), respectively. The high performance of the method exceeded the diagnostic power of standard measurements, thus showing its potential to contribute to drug evaluation methods. Further research with a larger number of events is required to generalize the method. • Study on cardiac vector velocity and non-invasive risk markers of Torsade de Pointes. • Principal component analysis homogenizes and reduces the information to three axes. • The angular velocity of T-wave shows a trend towards symmetry in at-risk patients. • Novel symmetry indices enhance the differences between at-risk and healthy subjects. [ABSTRACT FROM AUTHOR]

The ventricular gradient, an electrocardiographic concept calculated by integrating the area under the QRS complex and T-wave, represents the degree and direction of myocardial electrical heterogeneity. Although the concept of the ventricular gradient was first introduced in the 1930s, it has not yet found a place in routine electrocardiography. In the modern era, it is relatively simple to calculate the ventricular gradient in three dimensions (the spatial ventricular gradient (SVG)), and there is now renewed interest in using the SVG as a tool for risk stratification of ventricular arrhythmias and sudden cardiac death. This manuscript will review the history of the ventricular gradient, describe its electrophysiological meaning and significance, and discuss its clinical utility. [ABSTRACT FROM AUTHOR]

Early diagnosis and localization of myocardial infarction (MI) assist clinicians in saving numerous lives through the timely treatment for patients with MI. Vectorcardiogram (VCG) can reflect the characteristic changes of cardiac electrical activity in MI in detail. In this context, the present study reports a multi-branch weight sharing network model based on 2-D VCG constructed to realize the automatic localization of MI. The three-branch network extracted the spatial morphological features of the three planes of the 2-D VCG, respectively, and the weight-sharing part of the network obtained the spatial correlation information among the three planes. Subsequently, the Softmax classifier was employed to classify normal individuals and MI patients (11 class infarct sites). To evaluate the performance of the proposed method for MI localization, PTB(Physikalisch-Technische Bundesanstalt) diagnostic ECG database was employed. The localization accuracy, sensitivity, and specificity achieved using the proposed method were 99.87%, 99.92%, and 99.99%, respectively. Thus, the proposed scheme is expected to be useful in assisting cardiologists in interpreting VCG for clinical diagnosis. [ABSTRACT FROM AUTHOR]

Introduction: The conventional ECG is commonly used to screen for hypertrophic cardiomyopathy (HCM), but up to 25% of adults and possibly larger percentages of children with HCM have no distinctive abnormalities on the conventional ECG, whereas 5 to 15% of healthy young athletes do. Recently, a 5-min resting advanced 12-lead ECG test ("A-ECG score") showed superiority to pooled criteria from the strictly conventional ECG in correctly identifying adult HCM. The purpose of this study was to evaluate whether in children and young adults, A-ECG scoring could detect echocardiographic HCM associated with the MYBPC3 genetic mutation with greater sensitivity than conventional ECG criteria and distinguish healthy young controls and athletes from persons with MYBPC3 HCM with greater specificity.Methods: Five-minute 12-lead ECGs were obtained from 15 young patients (mean age 13.2years, range 0-30years) with MYBPC3 mutation and phenotypic HCM. The conventional and A-ECG results of these patients were compared to those of 198 healthy children and young adults (mean age 13.2, range 1month-30years) with unremarkable echocardiograms, and to those of 36 young endurance-trained athletes, 20 of whom had athletic (physiologic) left ventricular hypertrophy.Results: Compared with commonly used, age-specific pooled criteria from the conventional ECG, a retrospectively generated A-ECG score incorporating results from just 2 derived vectorcardiographic parameters (spatial QRS-T angle and the change in the vectorcardiographic QRS azimuth angle from the second to the third eighth of the QRS interval) increased the sensitivity of ECG for identifying MYBPC3 HCM from 46% to 87% (p<0.05). Use of the same score also demonstrated superior specificity in a set of 198 healthy controls (94% vs. 87% for conventional ECG criteria; p<0.01) including in a subset of 36 healthy, young endurance-trained athletes (100% vs. 69% for conventional ECG criteria, p<0.001).Conclusions: In children and young adults, a 2-parameter 12-lead A-ECG score is retrospectively significantly more sensitive and specific than pooled, age-specific conventional ECG criteria for detecting MYBPC3-HCM and in distinguishing such patients from healthy controls, including endurance-trained athletes. [ABSTRACT FROM AUTHOR]

The spectrum of frequencies producing the QRS complex has not been fully explored. In this manuscript we review previous studies of QRS frequency content, and discuss our novel method of the conjoint analysis of the ECG signal in six dimensions: in the domain of three space dimensions, in time domain, and in frequency domain. Orbital frequency of QRS loop is introduced as a six-dimensional characteristic of ventricular conduction, which helped to reveal inapparent ventricular conduction, and to characterize electrophysiological substrate. In this paper, we review our novel method in the historical context. [ABSTRACT FROM AUTHOR]

Introduction Serial analysis could improve ECG diagnosis of myocardial ischemia caused by acute coronary occlusion. Methods We analyzed ECG pairs of 84 cases and 398 controls. In case-patients, who underwent elective percutaneous coronary intervention, ischemic ECGs during balloon occlusion were compared with preceding non-ischemic ECGs. In control-patients, two elective non-ischemic ECGs were compared. In each ECG the ST vector at the J point and the ventricular gradient (VG) vector was computed, after which difference vectors ΔST and ΔVG were computed within patients. Finally, receiver operating characteristic analysis was done. Results Areas under the curve were 0.906 ( P < 0.001; CI 0.862–0.949; SE 0.022) for ΔST and 0.880 ( P < 0.001; CI 0.833–0.926; SE 0.024) for ΔVG. Sensitivity and specificity of conventional ST-elevation myocardial infarction (STEMI) criteria were 70.2% and 89.1%, respectively. At matched serial analysis specificity and STEMI specificity, serial analysis sensitivity was 78.6% for ΔST and 71.4% for ΔVG (not significantly different from STEMI sensitivity). At matched serial analysis sensitivity and STEMI sensitivity, serial analysis specificity was 96.5% for ΔST and 89.3% for ΔVG; ΔST and STEMI specificities differed significantly ( P < 0.001). Conclusion Detection of acute myocardial ischemia by serial ECG analysis of ST and VG vectors has equal or even superior performance than the STEMI criteria. This concept should be further evaluated in triage ECGs of patients suspected from having acute myocardial ischemia. [ABSTRACT FROM AUTHOR]

Patient-specific computational models have promise to improve cardiac disease diagnosis and therapy planning. Here a new method is described to simulate left-bundle branch block (LBBB) and RV-paced ventricular activation patterns in three dimensions from non-invasive, routine clinical measurements. Activation patterns were estimated in three patients using vectorcardiograms (VCG) derived from standard 12-lead electrocardiograms (ECG). Parameters of a monodomain model of biventricular electrophysiology were optimized to minimize differences between the measured and computed VCG. Electroanatomic maps of local activation times measured on the LV and RV endocardial surfaces of the same patients were used to validate the simulated activation patterns. For all patients, the optimal estimated model parameters predicted a time-averaged mean activation dipole orientation within 6.7 ± 0.6° of the derived VCG. The predicted local activation times agreed within 11.5 ± 0.8 ms of the measured electroanatomic maps, on the order of the measurement accuracy. [ABSTRACT FROM AUTHOR]

Abstract: Background: The ECG is important in the diagnosis and triage of the acute coronary syndrome (ACS), especially in the hyperacute phase, the “golden hours,” during which myocardial salvage possibilities are largest. An important triaging decision to be taken is whether or not a patient requires primary PCI, for which, as mentioned in the guidelines, the presence of an ST elevation (STE) pattern in the ECG is a major criterion. However, preexisting non-zero ST amplitudes (diagnostic, but also non-diagnostic) can obscure or even preclude this diagnosis. Methods: In this study, we investigated the potential diagnostic possibilities of ischemia detection by means of changes in the ST vector, ΔST, and changes in the VG (QRST integral) vector, ΔVG. We studied the vectorcardiograms (VCGs) synthesized of the ECGs of 84 patients who underwent elective PTCA. Mean±SD balloon occlusion times were 260±76s. The ECG ischemia diagnosis (ST elevation, STE, or non-ST-elevation, NSTE), magnitudes and orientations of the ST and VG vectors, and the differences ΔST and ΔVG with the baseline ECG were measured after 3min of balloon occlusion. Results: Planar angles between the ΔST and ΔVG vectors were 14.9±14.0°. Linear regression of ΔVG on ΔST yielded ΔVG=324·ΔST (r =0.85; P <0.0001, ΔST in mV). We adopted ΔST>0.05mV, and the corresponding ΔVG>16.2mV·ms as ischemia thresholds. The classical criteria characterized the ECGs of 46/84 (55%) patients after 3min of occlusion as STE ECGs. Combined application of the ΔST and ΔVG criteria identified 73/84 (87%) of the patients as ischemic. Conclusion: Differential diagnosis by ΔST and ΔVG (requiring an earlier made non-ischemic baseline ECG) could dramatically improve ECG guided detection of patients who urgently require catheter intervention. [Copyright &y& Elsevier]

Abstract: Introduction: Current criteria for electrocardiographic (ECG) diagnosis of left ventricular hypertrophy (LVH) have a low diagnostic accuracy. Addition of demographic, anthropomorphic, and additional ECG variables may improve accuracy. As hypertrophy affects action potential morphology and intraventricular conduction, QRS prolongation and T-wave morphology may occur and become manifest in the vectorcardiographic variables spatial QRS-T angle (SA) and spatial ventricular gradient. In this study, we attempted to improve the diagnostic accuracy for LVH by using a combination of demographic, anthropomorphic, ECG, and vectorcardiographic variables. Methods: The study group (n = 196) was divided in 4 subgroups with, on one hand, echocardiographically diagnosed LVH or a normal echocardiogram and, on the other hand, with any of the conventional ECG signs for LVH or with normal ECGs. Each subgroup was randomly split into halves, yielding 2 equally-sized (n = 98) data sets A and B. Age, sex, height, weight, body mass index, body surface area (BSA), frontal QRS axis, QRS duration, QT duration, maximal QRS vector magnitude, SA, and ventricular gradient magnitude and orientation were univariate studied by receiver operating characteristic analysis and were used to build a stepwise linear discriminant model using P < .05 as entry and P > .10 as removal criterion. The discriminant model was built in set A (model A) and tested on set B. Stability checks were done by building a discriminant model on set B and testing on set A and by cross-validation analysis in the complete study group. Results: The discriminant model equation was D = 5.130 × BSA − 0.014 × SA − 8.74, wherein D greater than or equal to 0 predicts a normal echocardiogram and D less than 0 predicts LVH. The diagnostic accuracy (79%) was better than the diagnostic accuracy of conventional ECG criteria for LVH (57%). Conclusion: The combination of BSA and SA yields a diagnostic accuracy of LVH that is superior to that of the conventional ECG criteria. [Copyright &y& Elsevier]

Background: Although pulmonary vein (PV)–left atrium (LA) reconnection is associated with recurrence of atrial fibrillation (AF) in patients who undergo pulmonary vein isolation (PVI), no noninvasive method for evaluating PV reconnection has yet been established. Objective: The purpose of this study was to examine whether PV–LA reconnection could be detected noninvasively by analyzing the change of P-loop configuration by vectorcardiography (VCG). Methods: The study included 80 patients with paroxysmal AF (8 female; mean age 58 ± 10 years) who underwent PVI. VCG was prospectively analyzed by recording during the procedure (before and after PVI) and 1 year after the procedure to noninvasively evaluate PV–LA reconnection. Results: All patients showed a significant antero-leftward shift in the middle portion of the P loop on the horizontal plane of VCG, with an increase of the area within the P loop after the initial PVI (2.4 ± 1.7 vs 4.6 ± 2.7 × 103 mV2, P <.001). Sixty-three (78.8%) patients without AF recurrence demonstrated no remarkable change in the P-loop area after 16 ± 11 months of follow-up (4.4 ± 2.7 vs 4.1 ± 2.5 × 103 mV2, P = .51), whereas 17 (21.2%) patients with AF recurrence demonstrated P-loop reversion to the preprocedural P-loop morphology, with a decrease of P-loop area (5.6 ± 2.7 vs 3.2 ± 1.7 × 103 mV2, P <.001). Conclusion: Change of the P loop on VCG was associated with subsequent PV–LA reconnection. VCG is helpful as a noninvasive method for detecting PV–LA reconnection after PVI for paroxysmal AF. [ABSTRACT FROM AUTHOR]

Abstract: Background and Purpose: Several studies have demonstrated that the spatial mean QRS-T angle (SA) predicts cardiac events and mortality. Spatial mean QRS-T angle is a vectorcardiographic variable. Because in clinical practice, 12-lead standard electrocardiograms (ECGs) are recorded rather than vectorcardiograms (VCGs) according to Frank, VCGs are commonly obtained by synthesizing them from 12-lead ECGs, by using a VCG synthesis matrix. Hence, the thus computed SA is an estimate of the real SA measured in the Frank VCG. Recent studies have shown that Kors VCG synthesis matrix yields better estimates of SA than the inverse Dower VCG synthesis matrix. Our current study aims to compare the predictive power of these SA variants for the occurrence of potentially lethal arrhythmias. Methods: The study group consisted of patients with ischemic heart disease and left ventricular systolic dysfunction who received an implantable cardioverter-defibrillator (ICD) for primary prevention. During follow-up, the occurrence of appropriate device therapy (occurrence of ventricular arrhythmia) was noted. Alternative SAs were computed in VCGs synthesized from standard 12-lead ECGs by using either the inverse Dower matrix (SA-Dower) or the Kors matrix (SA-Kors). Comparison of the predictive power of SA-Dower and SA- Kors was performed by receiver operating characteristic analysis, by Kaplan-Meier analysis, and by univariate and multivariate Cox regression analysis, using every 10th percentile of SA as a cutoff value. Results: The study group consisted of 412 patients (361 men; mean ± SD age 63 ± 11 years), in which 56 patients had appropriate ICD therapy during follow-up. Receiver operating characteristic analysis revealed that the area under the curve of SA-Kors was significantly larger than area under the curve of SA-Dower (0.646 vs 0.607, P = .043). The discriminative power of SA-Kors for the absence/presence of appropriate ICD therapy in patients during follow-up was generally superior to SA-Dower over a wide range of cutoff values in the Kaplan-Meier analysis and generally yielded stronger hazard ratios in the univariate and multivariate Cox regression analyses. Conclusion: If there is no specific reason to use the inverse Dower matrix, VCG synthesis from standard 12-lead ECGs should preferably be done by using the Kors matrix. It is likely to assume that already published studies in which the predictive value of SA-Dower was demonstrated would yield stronger results if the SA-Dower angles were substituted by SA-Kors angles. [Copyright &y& Elsevier]

Background: Methodological difficulties associated with QT measurements prompt the search for new electrocardiographic markers of repolarization heterogeneity. Objective: We hypothesized that beat-to-beat 3-dimensional vectorcardiogram variability predicts ventricular arrhythmia (VA) in patients with structural heart disease, left ventricular systolic dysfunction, and implanted implantable cardioverter-defibrillators (ICDs). Methods: Baseline orthogonal electrocardiograms were recorded in 414 patients with structural heart disease (mean age 59.4 ± 12.0; 280 white [68%] and 134 black [32%]) at rest before implantation of ICD for primary prevention of sudden cardiac death. R and T peaks of 30 consecutive sinus beats were plotted in 3 dimensions to form an R peaks cloud and a T peaks cloud. The volume of the peaks cloud was calculated as the volume within the convex hull. Patients were followed up for at least 6 months; sustained VA with appropriate ICD therapies served as an end point. Results: During a mean follow-up time of 18.4 ± 12.5 months, 61 of the 414 patients (14.73% or 9.6% per person-year of follow-up) experienced sustained VA with appropriate ICD therapies: 41 of them were white and 20 were black. In the multivariate Cox model that included inducibility of VA and use of beta-blockers, the highest tertile of T/R peaks cloud volume ratio significantly predicted VA (hazard ratio 1.68, 95% confidence interval 1.01 to 2.80; P = .046) in all patients. T peaks cloud volume and T/R peaks cloud volume ratio were significantly smaller in black subjects (median 0.09 [interquartile range 0.04 to 0.15] vs. median 0.11 [interquartile range 0.06 to 0.22], P = .002). Conclusion: A relatively large T peaks cloud volume is associated with increased risk of VA in patients with structural heart disease and systolic dysfunction. [ABSTRACT FROM AUTHOR]

Abstract: Background and purpose: Normal limits of the spatial QRS-T angle and spatial ventricular gradient (SVG) are only available from Frank vectorcardiograms (VCGs) of male subjects. We determined normal limits for these variables derived from standard 12-lead electrocardiograms (ECGs) of 660 male and female students aged 18 to 29 years. Methods: A computer algorithm was used that constructed approximated VCG leads by inverse Dower matrix transformation of the 12-lead ECG and subsequently calculated the spatial QRS-T angle, SVG magnitude, and orientation. Results: In female subjects, the QRS-T angle was more acute (females, 66° ± 23°; normal, 20°-116°; males, 80° ± 24°; normal, 30°-130°; P < .001), and the SVG magnitude was smaller (females, 81 ± 23 mV·ms; normal, 39-143 mV·ms; males, 110 ± 29 mV·ms; normal, 59-187 mV·ms; P < .001) than in male subjects. The male SVG magnitude in our study was larger than that computed in Frank VCGs (79 ± 28 mV·ms; P < .001). Conclusions: The spatial QRS-T angle and SVG depend strongly on sex. Furthermore, normal limits of SVG derived from Frank VCGs differ markedly from those derived from VCGs synthesized from the standard ECG. As nowadays, VCGs are usually synthesized from the 12-lead ECG; normal limits derived from the standard ECG should preferably be used. [Copyright &y& Elsevier]

Background: Although the electrocardiographic (ECG) features of early repolarization (ER) have been studied extensively, no systematic quantification of ventricular repolarization in subjects with ER has been conducted so far. Methods: The objective of the present study was to evaluate ECG and spatial vectorcardiographic (VCG) descriptors of ventricular repolarization in ER subjects and to associate them with the respective indices of ventricular depolarization. A digital 12-lead surface ECG was obtained from 108 young, healthy men with ER and 108 age-matched healthy controls. The maximum Q-onset–T-end interval (QT maximum), the maximum Q-onset–T-peak interval (QTp maximum), the respective QT dispersion values (QT maximum–QT minimum), the rate-corrected QTC maximum and QTpC maximum, the QRS duration, and the VCG markers spatial T amplitude, spatial QRS amplitude and spatial QRS–T angle, were evaluated in ER subjects and controls. Results: QT maximum (P=0.05) and QTp maximum (P=0.003) were higher in ER subjects than in controls, while QTC maximum (P<0.0001) and QTpC maximum (P=0.002) were lower in ER subjects than in controls. The QRS duration (P=0.013), as well as the spatial T amplitude, the spatial QRS amplitude, and the spatial QRS–T angle were higher in ER subjects than in controls (P<0.0001). The spatial T amplitude was not associated with the indices of ventricular depolarization neither in ER subjects, nor in controls. Conclusions: Ventricular repolarization, as well as depolarization, is altered in young, healthy males with ER compared to age-matched healthy controls. Ventricular depolarization and repolarization indices in ER subjects are not associated to each other. [Copyright &y& Elsevier]

Wide frequency band ECG and vectorcardiogram in anesthetized pigeon and mouse were studied from the standpoint of comparison. The key results were as follows: in pigeon, the direction of the main QRS was inverted in leads II, III and aVF, and upright in lead aVR, which was contrary to that in mouse. The T wave was upright in leads II, III and aVF, but inverted in lead aVR in pigeon, which was the same as that in mouse. In pigeon, there was a large notch on the upstroke of the S wave in lead II without exception, but there was no such notch in the corresponding lead in mouse. The QRS vector loop in the frontal plane lay between −90 and −180° in pigeon, while that of mouse lay between 0 and 90°. The relative power of high frequency range (80–1000 Hz) of the QRS in lead II was approximately 15% in pigeon, but 55% in mouse. The direction of the main QRS was contrary in pigeon and mouse because the subepicardial muscles were depolarized before the subendocardial muscles in pigeon, but the latter were depolarized before the former in mouse. The direction of the T waves was the same in both pigeon and mouse because subepicardial muscles were all repolarized before subendocardial muscles. [Copyright &y& Elsevier]

• A novel approach to detect and classify PMI from derived VCG signal is proposed. • The FBSE-EWT method with principal component analysis is used to extract features. • Performance of SVM, DT, and KNN classifier is compared. • The KNN classifier resulted in better performance compared to other classifiers. • The proposed method has achieved classification accuracy of 97.92%. The early detection of posterior myocardial infarction (PMI) is an important task as it can cause cardiac failure. Due to the absence of extra posterior leads in the standard 12-lead electrocardiogram (ECG), the PMI detection sensitivity degrades. To improve it, additional posterior leads can be included in standard 12-lead ECG system. Another approach utilizing vectorcardiogram (VCG) has been in practice with specific 7 electrodes with one posterior lead. Although the VCG approach is promising, the arrangement of posterior lead causes patient discomfort. To overcome aforesaid issue, derived VCG (dVCG) obtained through the Dowers inverse transformation has been proposed, wherein, from the standard 12-lead ECG, a three lead VCG is derived, which then can be utilized for PMI detection. Relying on the dVCG approach, in the present paper, we have proposed a novel methodology for PMI detection using Fourier-Bessel series expansion based empirical wavelet transform (FBSE-EWT). The non-stationary behavior of dVCG has been captured using FBSE-EWT, followed by the principal component analysis employing eigenvalues of covariance matrix. The constructed feature space is then fed to decision tree (DT), support vector machine (SVM), and K-nearest neighbor (KNN) classifiers. The KNN classifier with inverse squared city block distance resulted in the overall classification accuracy of 97.92% with sensitivity and specificity of 96.63% and 98.50%, respectively. The experiments were performed over Physikalisch-Technische Bundesanstalt Diagnostic (PTBD) dataset. The proposed method has the potential to be utilized in accurate and robust PMI detection from dVCG signals in the clinical settings. [ABSTRACT FROM AUTHOR]

• A non-invasive methodology is proposed to characterise different AFL circuits. • The VCG trajectory is evaluated to characterise AFL. • Consistency in the slow regions is determined for cases from the same AFL type. • The proposed method helps to identify AFL types in a non-invasive way. • The provided information prior to ablation may improve medical interventions. Macroreentrant atrial tachyarrhythmias (MRATs) can be caused by different reentrant circuits. The treatment for each MRAT type may require ablation at different sites, either at the right or left atria. Unfortunately, the reentrant circuit that drives the arrhythmia cannot be ascertained previous to the electrophysiological intervention. A noninvasive approach based on the comparison of atrial vectorcardiogram (VCG) loops is proposed. An archetype for each group was created, which served as a reference to measure the similarity between loops. Methods were tested in a variety of simulations and real data obtained from the most common right (peritricuspid) and left (perimitral) macroreentrant circuits, each divided into clockwise and counterclockwise subgroups. Adenosine was administered to patients to induce transient AV block, allowing the recording of the atrial signal without the interference of ventricular signals. From the vectorcardiogram, we measured intrapatient loop consistence, similarity of the pathway to archetypes, characterisation of slow velocity regions and pathway complexity. Results show a considerably higher similarity with the loop of its corresponding archetype, in both simulations and real data. We found the capacity of the vectorcardiogram to reflect a slow velocity region, consistent with the mechanisms of MRAT, and the role that it plays in the characterisation of the reentrant circuit. The intra-patient loop consistence was over 0.85 for all clinical cases while the similarity of the pathway to archetypes was found to be 0.85 ± 0.03, 0.95 ± 0.03, 0.87 ± 0.04 and 0.91 ± 0.02 for the different MRAT types (and p < 0.02 for 3 of the 4 groups), and pathway complexity also allowed to discriminate among cases (with p < 0.05). We conclude that the presented methodology allows us to differentiate between the most common forms of right and left MRATs and predict the existence and location of a slow conduction zone. This approach may be useful in planning ablation procedures in advance. [ABSTRACT FROM AUTHOR]

• Inaccuracies of QRS and T-wave markers significantly impact QRS-Ta estimation. • These errors influence the classification of clinically relevant abnormal values. • Our algorithm provides robust measurements in the presence of inaccurate VCG markers. • We present for the first time, the distribution of the QRS-Ta in a large cohort. The spatial QRS-T angle (QRS-Ta) derived from the vectorcardiogram (VCG) is a strong risk predictor for ventricular arrhythmia and sudden cardiac death with potential use for mass screening. Accurate QRS-Ta estimation in the presence of ECG delineation errors is crucial for its deployment as a prognostic test. Our study assessed the effect of inaccurate QRS and T-wave marker placement on QRS-Ta estimation and proposes a robust method for its calculation. Reference QRS-Ta measurements were derived from 1,512 VCGs manually annotated by three expert reviewers. We systematically changed onset and offset timings of QRS and T-wave markers to simulate inaccurate placement. The QRS-Ta was recalculated using a standard approach and our proposed algorithm, which limits the impact of VCG marker inaccuracies by defining the vector origin as an interval preceding QRS-onset and redefines the beginning and end of QRS and T-wave loops. Using the standard approach, mean absolute errors (MAE) in peak QRS-Ta were >40% and sensitivity and precision in the detection of abnormality (>105°) were <80% and <65% respectively, when QRS-onset was delayed or QRS-offset anticipated >15 ms. Using our proposed algorithm, MAE for peak QRS-Ta were reduced to <4% and sensitivity and precision of abnormality were >94% for inaccuracies up to ±15 ms. Similar results were obtained for mean QRS-Ta. In conclusion, inaccuracies of QRS and T-wave markers can significantly influence the QRS-Ta. Our proposed algorithm provides robust QRS-Ta measurements in the presence of inaccurate VCG annotation, enabling its use in large datasets. [ABSTRACT FROM AUTHOR]

Vectorcardiogram (VCG) represents the trajectory of the tip of cardiac vectors in three dimensional space with varying time. It is a recurring, near-periodic pattern of cardiac dynamics that is constructed by drawing the instantaneous vectors from a zero reference point according to direction, magnitude and polarity in the space. Being a three dimensional entity, it is more informative and more sensitive than conventional ECG as an evaluation tool of the physiology of cardiac dynamics, because of its extra degree of freedom. Accordingly, it is possible to find out even a minute and early electrophysiological alteration in diseases. Each cardiac cycle primarily consists of three loops in VCG corresponding to P, QRS, and T wave activities. The morphological assessment of the QRS loop was carried out in three dimensional space in order to analyze the spatial vectors of the ventricles and their patho-physiological correlation in various cardiac diseases. Spatial Velocity (SV) is a virtual velocity that represents the rate of movement of the tip of the cardiac vector through space, coordinated by three orthogonal leads, and can be estimated by using simple mathematical formula. It is the rate of change in amplitude and the directionality of instantaneous vectors in seriatim in the three dimensional space to quantify their the temporo-spatial characteristic pattern. We propose to evaluate this novel VCG descriptor SV, in normal individuals and patients of ventricular dysfunction. The possible mechanisms consistent with the patho-physiological basis of ventricular dysfunction or heart failure with altered SV would enrich the current understanding of the disease. Heart failure is the final common pathway of multitude of cardiac pathologies. Despite etiological heterogeneity, there are common mechanisms involved in the complex electrophysiological alteration of the failing myocardium. The changes observed as a consequence of ventricular dysfunction involve ion channel remodeling, intercellular uncoupling, myocardial ischemia, alterations in calcium handling, remodeling of the extracellular matrix, the presence of scars, activation of the sympathetic & the renin-angiotensin-aldosterone system, dilatation as well as stretch of viscous etc. The source modulation of the depolarization wave and its propagation in the heart and body fluid volume conductor also influence the visual pattern of cardiac vectors. In addition, patients with heart failure receive pharmacological or non-pharmacological therapies that also influence the electrophysiological changes. We hypothesize that the spatial velocity of ventricular depolarization and repolarization vectors of the VCG loop alters with a characteristic pattern in the patients with ventricular dysfunction and can differentiate healthy individuals from patients with ventricular dysfunction and also differentiate various categories, gradations and severity stratifications of the patients with ventricular dysfunction. [ABSTRACT FROM AUTHOR]

Vectorcardiogram (VCG) is a recurring, near-periodic pattern of cardiac dynamics that graphically represents the trajectory of the tip of cardiac vectors in three dimensional space with varying time. VCG is constructed by drawing the instantaneous vectors from a zero reference point according to direction, magnitude and polarity in the space. It is more informative and sensitive than conventional ECG as an evaluation tool of the physiology of cardiac dynamics. Each heart cycle consists of three loops corresponding to P, QRS, and T wave activities in VCG. The morphological assessment of the QRS loop was carried out in order to analyze the spatial vectors of the ventricles and their patho-physiological correlation in various cardiac diseases. It was found that, the three dimensional QRS loop in healthy individuals lies in a plane. It is rather surprising that the normal spatial QRS loop lies in a single plane, considering the complex structure of the ventricular musculature together with the numerous possible pathways along which the depolarization impulse passes. The highly curious phenomenon of planarity of the spatial QRS loop was explained by uniform double layer (UDL) theory, which postulates the phenomenon of activation wave-fronts that propagate with a constant & uniform rate throughout the myocardium. Acute myocardial infarction results in loss of structural and functional integrity of the different layers of heart, perturbation of the uniformity in wave propagation due to the disturbance in directional symmetry, development of nonlinear relationships among the concerned variables, loss of homogeneity and complete loss of planarity of the 3D-QRS loop. The planarity of the 3D-QRS loop is a highly restricted and sensitive parameter and a characteristic feature of normal heart and can be utilized as a test for diagnostic screening of cardiac normalcy and the loss of planarity may be a conspicuous feature of AMI. It will be reasonable to study the morphology of the spatial QRS loop in patients of AMI throughout the course of disease and also in a regular interval through the long-term follow up period. It is expected that with the reperfusion, recovery and salvage of the diseased myocardium; the homogeneity and the intensity of the line density of the membrane current of the UDL would gradually recover with retrieval of the planarity of the spatial QRS loop. The temporal pattern of characteristics alteration of the QRS loop planarity with the natural course of the disease requires intensive evaluation. We propose that, the planarity of the spatial QRS loop, its loss, involution and reversal is a temporal series of events in AMI and also a crucial diagnostic and prognostic parameter. [ABSTRACT FROM AUTHOR]