A novel method combining gated SPECT and vectorcardiography to guide left ventricular lead placement to improve response to cardiac resynchronization therapy: A proof of concept study.

BACKGROUND: The segment of the latest mechanical contraction (LMC) does not always overlap with the site of the latest electrical activation (LEA). By integrating both mechanical and electrical dyssynchrony, this proof-of-concept study aimed to propose a new method for recommending left ventricular (LV) lead placements, with the goal of enhancing response to cardiac resynchronization therapy (CRT). METHODS: The LMC segment was determined by single-photon emission computed tomography myocardial perfusion imaging (SPECT MPI) phase analysis. The LEA site was detected by vectorcardiogram. The recommended segments for LV lead placement were as follows: (1) the LMC viable segments that overlapped with the LEA site; (2) the LMC viable segments adjacent to the LEA site; (3) If no segment met either of the above, the LV lateral wall was recommended. The response was defined as ≥15% reduction in left ventricular end-systolic volume (LVESV) 6-months after CRT. Patients with LV lead located in the recommended site were assigned to the recommended group, and those located in the non-recommended site were assigned to the non-recommended group. RESULTS: The cohort comprised of 76 patients, including 54 (71.1%) in the recommended group and 22 (28.9%) in the non-recommended group. Among the recommended group, 74.1% of the patients responded to CRT, while 36.4% in the non-recommended group were responders (P = .002). Compared to pacing at the non-recommended segments, pacing at the recommended segments showed an independent association with an increased response by univariate and multivariable analysis (odds ratio 5.00, 95% confidence interval 1.73-14.44, P = .003; odds ratio 7.33, 95% confidence interval 1.53-35.14, P = .013). Kaplan-Meier curves showed that pacing at the recommended LV lead position demonstrated a better long-term prognosis. CONCLUSION: Our findings indicate that pacing at the recommended segments, by integrating of mechanical and electrical dyssynchrony, is significantly associated with an improved CRT response and better long-term prognosis.

Different methods of 3D QRS area calculation from vectorcardiographic X, Y, and Z Leads.

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).

Monitoring of myocardial injury by serial measurements of QRS area and T area: The MaastrICCht cohort.

BACKGROUND: Manually derived electrocardiographic (ECG) parameters were not associated with mortality in mechanically ventilated COVID-19 patients in earlier studies, while increased high-sensitivity cardiac troponin-T (hs-cTnT) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) were. To provide evidence for vectorcardiography (VCG) measures as potential cardiac monitoring tool, we investigated VCG trajectories during critical illness. METHODS: All mechanically ventilated COVID-19 patients were included in the Maastricht Intensive Care Covid Cohort between March 2020 and October 2021. Serum hs-cTnT and NT-proBNP concentrations were measured daily. Conversion of daily 12-lead ECGs to VCGs by a MATLAB-based script provided QRS area, T area, maximal QRS amplitude, and QRS duration. Linear mixed-effect models investigated trajectories in serum and VCG markers over time between non-survivors and survivors, adjusted for confounders. RESULTS: In 322 patients, 5461 hs-cTnT, 5435 NT-proBNP concentrations and 3280 ECGs and VCGs were analyzed. Non-survivors had higher hs-cTnT concentrations at intubation and both hs-cTnT and NT-proBNP significantly increased compared with survivors. In non-survivors, the following VCG parameters decreased more when compared to survivors: QRS area (-0.27 (95% CI) (-0.37 to -0.16, p < .01) µVs per day), T area (-0.39 (-0.62 to -0.16, p < .01) µVs per day), and maximal QRS amplitude (-0.01 (-0.01 to -0.01, p < .01) mV per day). QRS duration did not differ. CONCLUSION: VCG-derived QRS area and T area decreased in non-survivors compared with survivors, suggesting that an increase in myocardial damage and tissue loss play a role in the course of critical illness and may drive mortality. These VCG markers may be used to monitor critically ill patients.

Congenital short QT syndrome: A review focused on electrocardiographic features.

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.

Limits of the spatial ventricular gradient and QRST angles in patients with normal electrocardiograms and no known cardiovascular disease stratified by age, sex, and race.

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/.

A Deep Learning Architecture Using 3D Vectorcardiogram to Detect R-Peaks in ECG with Enhanced Precision.

Providing reliable detection of QRS complexes is key in automated analyses of electrocardiograms (ECG). Accurate and timely R-peak detections provide a basis for ECG-based diagnoses and to synchronize radiologic, electrophysiologic, or other medical devices. Compared with classical algorithms, deep learning (DL) architectures have demonstrated superior accuracy and high generalization capacity. Furthermore, they can be embedded on edge devices for real-time inference. 3D vectorcardiograms (VCG) provide a unifying framework for detecting R-peaks regardless of the acquisition strategy or number of ECG leads. In this article, a DL architecture was demonstrated to provide enhanced precision when trained and applied on 3D VCG, with no pre-processing nor post-processing steps. Experiments were conducted on four different public databases. Using the proposed approach, high F1-scores of 99.80% and 99.64% were achieved in leave-one-out cross-validation and cross-database validation protocols, respectively. False detections, measured by a precision of 99.88% or more, were significantly reduced compared with recent state-of-the-art methods tested on the same databases, without penalty in the number of missed peaks, measured by a recall of 99.39% or more. This approach can provide new applications for devices where precision, or positive predictive value, is essential, for instance cardiac magnetic resonance imaging.

Contribution of the vectorcardiogram in the differential diagnosis of Brugada electrocardiographic pattern.

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.

[Features of vectorcardiograms in patients with hypertension complicated by chronic heart failure with reduced left ventricle ejection fraction].

AIM: To explore the features of vectorcardiograms (VCG) of patients with essential hypertension complicated by chronic heart failure with reduced left ventricular ejection fraction (CHFrLVEF). MATERIALS AND METHODS: We analyzed VCGs of 70 hypertensive patients with CHFrLVEF and 275 hypertensive patients without clinical signs of CHF and with LVEF50%. We assessed the presence of rhythm and conduction disturbances, and the parameters of the synthesized VCG, i.e., module of the maximum QRS vector, planarity index of the spatial QRS loop (P/S), and spatial angle between the integral QRS and T vectors (sQRS-Ta). RESULTS: In hypertensive patients with CHF, certain conditions were detected more often as compared with hypertensive patients without CHF, i.e., atrial fibrillation (AF) in 52.9% vs 5.1%; p0.0001, and left bundle branch block (LBBB) in 38.6% vs 0.4%; p0.0001. The module of the maximum QRS vector and sQRS-Ta were significantly greater and P/S was significantly less in VCGs of patients with CHF. ROC-analysis showed that the presence of AF and LBBB just as VCG parameters assessed in this study provide clear discrimination between hypertensive patients with or without CHF both in the group as a whole and in the subgroups (1) without LBBB, (2) with sinus rhythm, and (3) with AF. sQRS-Ta was the most informative parameter (threshold 137, sensitivity 91%, specificity 92%). The P/S indicator at the optimal threshold value 0.92 was characterized by lower specificity (68%) with rather high sensitivity (79%). CONCLUSION: AF, LBBB, increased module of the maximum QRS vector and sQRS-Ta, and decreased P/S index are present in hypertensive patients with CHFrLVEF as compared with patients without CHF.

Atlas-based methods for efficient characterization of patient-specific ventricular activation patterns.

AIMS: Ventricular activation patterns can aid clinical decision-making directly by providing spatial information on cardiac electrical activation or indirectly through derived clinical indices. The aim of this work was to derive an atlas of the major modes of variation of ventricular activation from model-predicted 3D bi-ventricular activation time distributions and to relate these modes to corresponding vectorcardiograms (VCGs). We investigated how the resulting dimensionality reduction can improve and accelerate the estimation of activation patterns from surface electrogram measurements. METHODS AND RESULTS: Atlases of activation time (AT) and VCGs were derived using principal component analysis on a dataset of simulated electrophysiology simulations computed on eight patient-specific bi-ventricular geometries. The atlases provided significant dimensionality reduction, and the modes of variation in the two atlases described similar features. Utility of the atlases was assessed by resolving clinical waveforms against them and the VCG atlas was able to accurately reconstruct the patient VCGs with fewer than 10 modes. A sensitivity analysis between the two atlases was performed by calculating a compact Jacobian. Finally, VCGs generated by varying AT atlas modes were compared with clinical VCGs to estimate patient-specific activation maps, and the resulting errors between the clinical and atlas-based VCGs were less than those from more computationally expensive method. CONCLUSION: Atlases of activation and VCGs represent a new method of identifying and relating the features of these high-dimensional signals that capture the major sources of variation between patients and may aid in identifying novel clinical indices of arrhythmia risk or therapeutic outcome.

Reproducibility of global electrical heterogeneity measurements on 12-lead ECG: The Multi-Ethnic Study of Atherosclerosis.

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 12­lead 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.

Relevance of the vectorcardiogram in the Brugada syndrome with "northwest QRS axis".

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.

Characterization of Changes in P-Wave VCG Loops Following Pulmonary-Vein Isolation.

Atrial fibrillation is the most common type of cardiac arrhythmia in clinical practice. Currently, catheter ablation for pulmonary-vein isolation is a well-established treatment for maintaining sinus rhythm when antiarrhythmic drugs do not succeed. Unfortunately, arrhythmia recurrence after catheter ablation remains common, with estimated rates of up to 45%. A better understanding of factors leading to atrial-fibrillation recurrence is needed. Hence, the aim of this study is to characterize changes in the atrial propagation pattern following pulmonary-vein isolation, and investigate the relation between such characteristics and atrial-fibrillation recurrence. Fifty patients with paroxysmal atrial fibrillation who had undergone catheter ablation were included in this study. Time-segment and vectorcardiogram-loop-morphology analyses were applied to characterize P waves extracted from 1 min long 12-lead electrocardiogram segments before and after the procedure, respectively. Results showed that P-wave vectorcardiogram loops were significantly less round and more planar, P waves and PR intervals were significantly shorter, and heart rate was significantly higher after the procedure. Differences were larger for patients who did not have arrhythmia recurrences at 2 years of follow-up; for these patients, the pre- and postprocedure P waves could be identified with 84% accuracy.

Left Axis Deviation in Brugada Syndrome: Vectorcardiographic Evaluation during Ajmaline Provocation Testing Reveals Additional Depolarization Abnormalities.

Patients with Brugada syndrome (BrS) can show a leftward deviation of the frontal QRS-axis upon provocation with sodium channel blockers. The cause of this axis change is unclear. In this study, we aimed to determine (1) the prevalence of this left axis deviation and (2) to evaluate its cause, using the insights that could be derived from vectorcardiograms. Hence, from a large cohort of patients who underwent ajmaline provocation testing (n = 1430), we selected patients in whom a type-1 BrS-ECG was evoked (n = 345). Depolarization and repolarization parameters were analyzed for reconstructed vectorcardiograms and were compared between patients with and without a >30° leftward axis shift. We found (1) that the prevalence of a left axis deviation during provocation testing was 18% and (2) that this left axis deviation was not explained by terminal conduction slowing in the right ventricular outflow tract (4th QRS-loop quartile: +17 ± 14 ms versus +13 ± 15 ms, nonsignificant) but was associated with a more proximal conduction slowing (1st QRS-loop quartile: +12[8;18] ms versus +8[4;12] ms, p < 0.001 and 3rd QRS-loop quartile: +12 ± 10 ms versus +5 ± 7 ms, p < 0.001). There was no important heterogeneity of the action potential morphology (no difference in the ventricular gradient), but a left axis deviation did result in a discordant repolarization (spatial QRS-T angle: 122[59;147]° versus 44[25;91]°, p < 0.001). Thus, although the development of the type-1 BrS-ECG is characterized by a terminal conduction delay in the right ventricle, BrS-patients with a left axis deviation upon sodium channel blocker provocation have an additional proximal conduction slowing, which is associated with a subsequent discordant repolarization. Whether this has implications for risk stratification is still undetermined.

An initial exploration of subtraction electrocardiography to detect myocardial ischemia in the prehospital setting.

BACKGROUND: In the prehospital triage of patients presenting with symptoms suggestive of acute myocardial ischemia, reliable myocardial ischemia detection in the electrocardiogram (ECG) is pivotal. Due to large interindividual variability and overlap between ischemic and nonischemic ECG-patterns, incorporation of a previous elective (reference) ECG may improve accuracy. The aim of the current study was to explore the potential value of serial ECG analysis using subtraction electrocardiography. METHODS: SUBTRACT is a multicenter retrospective observational study, including patients who were prehospitally evaluated for acute myocardial ischemia. For each patient, an elective previously recorded reference ECG was subtracted from the ambulance ECG. Patients were classified as myocardial ischemia cases or controls, based on the in-hospital diagnosis. The diagnostic performance of subtraction electrocardiography was tested using logistic regression of 28 variables describing the differences between the reference and ambulance ECGs. The Uni-G ECG Analysis Program was used for state-of-the-art single-ECG interpretation of the ambulance ECG. RESULTS: In 1,229 patients, the mean area-under-the-curve of subtraction electrocardiography was 0.80 (95%CI: 0.77-0.82). The performance of our new method was comparable to single-ECG analysis using the Uni-G algorithm: sensitivities were 66% versus 67% (p-value > .05), respectively; specificities were 80% versus 81% (p-value > .05), respectively. CONCLUSIONS: In our initial exploration, the diagnostic performance of subtraction electrocardiography for the detection of acute myocardial ischemia proved equal to that of state-of-the-art automated single-ECG analysis by the Uni-G algorithm. Possibly, refinement of both algorithms, or even integration of the two, could surpass current electrocardiographic myocardial ischemia detection.

[Diagnostic and prognostic significance of QRS-T angle].

The angle between theQRSandTvectors reflects the consistency or inconsistency of the processes of de- and repolarization of the ventricles of the heart and is considered one of the indicators of global electrical heterogeneity of myocardium. In recent years, the prognostic value of theQRS-Tangle has been demonstrated in relation to total and cardiovascular mortality, both in the population and in various groups of patients. The mechanisms of this phenomenon are not completely clear. The review analyses studies published over the past five years on the relationship between theQRS-Tangle and mortality, as well as coronary heart disease and heart failure. Possible mechanisms for increasing theQRS-Tangle are discussed. Data are given on the use of theQRS-Tangle in diagnostic and prognostic scales, including in combination with other indicators of global electrical heterogeneity of myocardium.

Vectorcardiogram in athletes: The Sun Valley Ski Study.

BACKGROUND: Global electrical heterogeneity (GEH) is associated with sudden cardiac death (SCD) in adults of 45 years and above. However, GEH has not been previously measured in young athletes. The goal of this study was to establish a reference for vectorcardiograpic (VCG) metrics in male and female athletes. METHODS: Skiers (n = 140; mean age 19.2 ± 3.5 years; 66% male, 94% white; 53% professional athletes) were enrolled in a prospective cohort. Resting 12-lead ECGs were interpreted per the International ECG criteria. Associations of age, sex, and athletic performance with GEH were studied. RESULTS: In age and training level-adjusted analyses, male sex was associated with a larger T vector [T peak magnitude +186 (95% CI 106-266) µV] and a wider spatial QRS-T angle [+28.2 (17.3-39.2)°] as compared to women. Spatial QRS-T angle in the ECG left ventricular hypertrophy (LVH) voltage group (n = 21; 15%) and normal ECG group did not differ (67.7 ± 25.0 vs. 66.8 ± 28.2; p = 0.914), suggesting that ECG LVH voltage in athletes reflects physiological remodeling. In contrast, skiers with right ventricular hypertrophy (RVH) voltage (n = 26, 18.6%) had wider QRS-T angle (92.7 ± 29.6 vs. 66.8 ± 28.2°; p = 0.001), larger SAI QRST (194.9 ± 30.2 vs. 157.8 ± 42.6 mV × ms; p < 0.0001), but similar peak SVG vector magnitude (1976 ± 548 vs. 1939 ± 395 µV; p = 0.775) as compared to the normal ECG group. Better athletic performance was associated with the narrower QRS-T angle. Each 10% worsening in an athlete's Federation Internationale de' Ski downhill ranking percentile was associated with an increase in spatial QRS-T angle by 2.1 (95% CI 0.3-3.9) degrees (p = 0.013). CONCLUSION: Vectorcardiograpic adds nuances to ECG phenomena in athletes.

Electro-vectorcardiographic and electrophysiological aspects of Ebstein's anomaly.

Ebstein's anomaly is a congenital heart disease where the most important anatomic feature is the inferior displacement of the tricuspid valve leaflets. Vectorcardiographic features are mainly forgotten and electrocardiographic features may be unrecognized by cardiologists handling adult patients.

Comparison of the integral indices of the vectorcardiogram with the data of echocardiography in patients with idiopathic and chronic thromboembolic pulmonary hypertension.

AIM: The aim of the work is to compare vectorcardiographic (VCG) variables - spatial QRS-T angle and electrocardiographic ventricular gradient (VG) with echocardiography (EchoCG) data in patients with idiopathic pulmonary hypertension (IPH) and chronic thromboembolic pulmonary hypertension (CTEPH). MATERIALS AND METHODS: In 40 patients with IPH and 40 patients with CTEPH at the age of 45±12 years, systolic pulmonary artery pressure (SPAP); the sizes of heart chambers, parameters of RV systolic and diastolic function were evaluated with EchoCG. The QRS-T and VG angles were calculated on the VCG, derived from 12-lead digital ECG. RESULTS: In all patients SPAP was greater than 40 mm Hg (mean 83±18 mm Hg), EchoCG data indicated hypertrophy and dilatation of RV, its systolic and diastolic function; dilatation of the right atrium (RA). Prognostically unfavorable changes in EchoCG were observed: the presence of pericardial effusion in 35 (44%) patients, RA area greater than 26 cm2 in 18 (23%) patients; TAPSE less than 1.5 cm in 37 (46%) patients. EchoCG and VCG variables had statistically significant differences in patients with III-IV functional class in comparison with I-II functional class. Statistically significant moderate correlations between VCG and EchoCG variables were revealed. VCG variables allowed to separate patient groups with the presence and absence of prognostically unfavorable changes in EchoCG with sensitivity from 54 to 78% and specificity from 66 to 87%. CONCLUSION: In patients with IPH and CTEPH, changes of QRS-T angle and VG correlate with SPAP, the size of RV and RA, parameters of RV systolic and diastolic function. The possibility of the use of QRS-T angle and VG for the detection of patients with prognostically unfavorable echocardiographic changes in the general group of patients with IPH and CTEPH has been shown.

Spatial QRS-T angle variants for prediction of all-cause mortality.

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.

Optimal configuration of adhesive ECG patches suitable for long-term monitoring of a vectorcardiogram.

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.