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).

Vectorcardiography Predicts Heart Failure in Patients Following ST Elevation Myocardial Infarction.

BACKGROUND: Modeling outcomes, such as onset of heart failure (HF) or mortality, in patients following ST elevation myocardial infarction (STEMI) is challenging but clinically very useful. The acute insult following a myocardial infarction and chronic degeneration seen in HF involve a similar process where a loss of cardiomyocytes and abnormal remodeling lead to pump failure. This process may alter the strength and direction of the heart's net depolarization signal. We hypothesize that changes over time in unique parameters extracted using vectorcardiography (VCG) have the potential to predict outcomes in patients post-STEMI and could eventually be used as a noninvasive and cost-effective surveillance tool for characterizing the severity and progression of HF to guide evidence-based therapies. METHODS: We identified 162 patients discharged from Michigan Medicine between 2016 and 2021 with a diagnosis of acute STEMI. For each patient, a single 12-lead ECG > 1 week pre-STEMI and > 1 week post-STEMI were collected. A set of unique VCG parameters were derived by analyzing features of the QRS complex. We used LASSO regression analysis incorporating clinical variables and VCG parameters to create a predictive model for HF, mortality, or the composite at 90, 180, and 365 days post-STEMI. RESULTS: The VCG model is most predictive for HF onset at 90 days with a robust AUC. Variables from the HF model mitigating or driving risk, at a p < 0.05, were primarily parameters that assess the area swept by the depolarization vector including the 3D integral and convex hull in select spatial octants and quadrants.

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.

Abnormal QRS-T angles in 5796 women and men aged 50-64: an electrocardiographic analysis providing mechanistic insights.

INTRODUCTION: 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. METHODS: Applying Frank vectorcardiography (VCG) and simultaneously recorded scalar 12­lead 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. RESULTS: 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. CONCLUSIONS: 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.

Ventricular injury in acute left circumflex occlusion: Exploration using precordial bipolar leads and regional vectorcardiograms.

BACKGROUND: Precordial Bipolar Leads (PBLs) provide new electrocardiographic information derived from standard 12­lead ECG recordings. OBJECTIVES: To explore the usefulness of PBLs in patients with acute circumflex coronary artery (CxCA) occlusion. METHODS: Twelve patients undergoing elective percutaneous transluminal coronary angioplasty (PTCA) were studied before and after acute CxCA occlusion and their data were processed with new methods based on PBLs. RESULTS: The findings were: 1. In right PBL V2-V1, a strong systolic current of injury moving in the left-to-right direction coexists with a strong right-to-left current of injury displayed in left standard unipolar precordial leads (V4, V5 and V6). 2. Ischemic changes lead to a significant increase (approximately 10 ms) in the QRS duration in different leads, although changes in the QRS loop rotation and folding were absent. 3. In the transverse, sagittal, and frontal planes, superimposing two PBLs and the corresponding Regional VCG facilitates the location of the J-point. 4. In the Regional VCGs of this group of patients, J-point and ST segment shifts produced an image that reminds the Greek letter omega (Ω). 5. The currents of injury flowing in opposite directions could result in electrical cancellation that minimizes ECG changes in the standard 12­lead recordings. CONCLUSIONS: Computerized processing of digital, standard 12­lead ECG recordings, provides new valuable diagnostic data in patients with acute CxCA occlusion. The loops revealed important information related to systolic currents of injury. Because these methods use routine 12­lead ECG data, the procedure is based only in software applications. CONDENSED ABSTRACT: Twelve patients undergoing PTCA were studied before and after acute CxCA occlusion and their data were processed with the new methods based on Precordial Bipolar Leads (PBLs) to explore their usefulness. The results showed strong systolic currents of injury in different and sometimes opposite directions in the right-to-left axis and ischemic alterations in the time and amplitude of the QRS waves. The superimposition of two-dimensional coordinates planes (x-y, x-z or z-y) helped to locate the J-point and to display the Regional VCG omega sign (Ω) of myocardial injury. In conclusion, computerized processing of digital ECG data provides new diagnostic information in patients with acute CxCA occlusion.

Exploring vectorcardiography: An extensive vectocardiogram analysis across age, sex, BMI, and cardiac conditions.

BACKGROUND: The vectocardiogram (VCG) offers a three-dimensional view of the heart's electrical activity, yet many VCG parameters remain unexplored in diverse clinical contexts. OBJECTIVES: This study aims to explore the relationships between various VCG parameters and specific patient characteristics. METHODS: ECG signals from adults were transformed into VCGs utilizing the Kors matrix, yielding 315 parameters per patient from the P, QRS and T loops. Univariable analysis, circular statistics, and stepwise logistic regression were employed to examine the relationships between VCG parameters and factors such as age, sex, BMI, hypertension, echocardiographic ischemic heart disease (Echo-IHD), and left ventricular hypertrophy (Echo-LVH). RESULTS: We included 664 adults and considered an alpha value of 0.05 and a power of 90%. The study revealed significant associations, such as age with P loop roundness index (RI) (OR = 3.825, 95% confidence interval [95%CI] = 2.079-7.04), male sex with QRS loop RI (OR = 6.08, 95%CI = 1.835-20.153), abnormal BMI with the T loop's RI (OR = 0.544, 95%CI = 0.325-0.909), hypertension with the T loop planarity index (PI) (OR = 8.01, 95%CI = 2.134-30.117), Echo-IHD with QRS loop curvature at the 4/10th segment (OR = 7.58, 95%CI = 1.954-29.458), and Echo-LVH with the T loop lag-1/10 dihedral angle (OR = 10.3, 95%CI = 1.822-58.101). In the study, several additional VCG parameters demonstrated statistically significant, albeit smaller, associations with patient demographics and cardiovascular conditions. CONCLUSIONS: The findings enhance our understanding of the intricate relationships between VCG parameters and patient characteristics, emphasizing the potential role of VCG analysis in assessing cardiovascular diseases. These insights may guide future research and clinical applications in cardiology.

Vectorcardiography signs of a failing Fontan: Heart rate, PR interval, RtQRSvm, QRSvm and SPQRS-T angle as noninvasive markers of late Fontan complications and mortality.

BACKGROUND: Limited data exists on interpreting vectorcardiography (VCG) parameters in the Fontan population. OBJECTIVE: The purpose of this study was to demonstrate the associations between ECG/VCG parameters and Fontan failure (FF). METHODS/RESULTS: 107 patients with a Fontan operation after 1990 and without significant ventricular pacing were included. FF and Fontan survival (FS) groups were compared. The average follow-up after Fontan operation was 11.8 years ±7.1 years. 14 patients had FF (13.1%) which was defined as having protein-losing-enteropathy (1.9%), plastic bronchitis (2.8%), Fontan takedown (1.9%), heart transplant (5.6%), NYHA class III-IV (2.8%) or death (0.9%). A 12­lead ECG at last follow up or prior to FF was assessed for heart rate, PR interval, QRS duration, Qtc and left/right sided precordial measures (P-wave, QRS and T-wave vector magnitudes, spatial P-R and QRS-T angles). Transthoracic echocardiogram evaluated atrioventricular valve regurgitation and ventricular dysfunction at FF or last follow up. A cox multivariate regression analysis adjusted for LV dominance, ventricular dysfunction, HR, PR, QTc, Pvm, QRSvm, SPQRST-angle, RtPvm, RtQRSvm and RtTvm. Ventricular dysfunction, increased heart rate and prolonged PR interval were significantly associated to FF at the multivariate analysis. ROC analysis and Kaplan-meier analysis revealed an increased total mortality associated with a heart rate > 93 bpm, PR interval > 155 mv, QRSvm >1.91 mV, RtQRSvm >1.8 mV and SPQRST angle >92.3 mV with p values <0.001 to 0.018. CONCLUSION: We demonstrate the importance of ECG/VCG monitoring in the Fontan population and suggest specific indicators of late complications and mortality.

Noninvasive electrophysiological differences between women and men: differences in body size not an explanation.

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.

QRS area as a predictor of cardiac resynchronization therapy response: A systematic review and meta-analysis.

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.

Is derived vectorcardiography a potential screening tool for pulmonary hypertension?

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.

[On the history of vectorcardiography: past, present, future].

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.

Re-evaluating the electro-vectorcardiographic criteria for left bundle branch block.

The criteria for left bundle branch block have gained growing interest in the last few years. In this overview, we discuss diagnostic and prognostic aspects of different criteria. It was already shown that stricter criteria, including longer QRS duration and slurring/notching of the QRS, better identify responders to cardiac resynchronization therapy. We also include aspects of ST/T concordance and discordance and vectorcardiography, which could further improve in the fine-tuning of the left bundle branch criteria.

Electro-vectorcardiographic demonstration of rate-independent transient left posterior fascicular block.

Left posterior fascicular block (LPFB) is a rare intraventricular conduction disorder of rare occurrence, especially as an isolated entity. Its transient form is even rarer and maybe rate-independent or rate-dependent intermittent LPFB (phase 3 block, tachycardia-dependent and phase 4 block or bradycardia-dependent). We present a case of a young adult male whose baseline ECG/VCG showed the typical LPFB pattern. A treadmill stress test revealed rate-independent intermittent LPFB with random occurrence. Imaging exams ruled out structural heart disease. To our knowledge, this is the first case in the literature of a rate-independent intermittent LPFB with no underlying structural heart disease.

Left bundle branch block: Epidemiology, etiology, anatomic features, electrovectorcardiography, and classification proposal.

In left bundle branch block (LBBB), the ventricles are activated in a sequential manner with alterations in left ventricular mechanics, perfusion, and workload resulting in cardiac remodeling. Underlying molecular, cellular, and interstitial changes manifest clinically as changes in size, mass, geometry, and function of the heart. Cardiac remodeling is associated with progressive ventricular dysfunction, arrhythmias, and impaired prognosis. Clinical and diagnostic notions about LBBB have evolved from a simple electrocardiographic alteration to a critically important finding affecting diagnostic and clinical management of many patients. Advances in cardiac magnetic resonance imaging have significantly improved the assessment of patients with LBBB and provided additional insights into pathophysiological mechanisms of left ventricular remodeling. In this review, we will discuss the epidemiology, etiologies, and electrovectorcardiographic features of LBBB and propose a classification of the conduction disturbance.

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.

Electro-vectorcardiographic demonstration of bifascicular block associated with ventricular preexcitation.

Down syndrome occurs more frequently in the offsprings of older pregnant women and may be associated with atrioventricular septal defect. This refers to a broad spectrum of malformations characterized by a deficiency of the atrioventricular septum and abnormalities of the atrioventricular valves caused by an abnormal fusion of the superior and inferior endocardial cushions with the midportion of the atrial septum and the muscular portion of the ventricular septum.

Comparison of Different Electrocardiography with Vectorcardiography Transformations.

This paper deals with transformations from electrocardiographic (ECG) to vectorcardiographic (VCG) leads. VCG provides better sensitivity, for example for the detection of myocardial infarction, ischemia, and hypertrophy. However, in clinical practice, measurement of VCG is not usually used because it requires additional electrodes placed on the patient's body. Instead, mathematical transformations are used for deriving VCG from 12-leads ECG. In this work, Kors quasi-orthogonal transformation, inverse Dower transformation, Kors regression transformation, and linear regression-based transformations for deriving P wave (PLSV) and QRS complex (QLSV) are implemented and compared. These transformation methods were not yet compared before, so we have selected them for this paper. Transformation methods were compared for the data from the Physikalisch-Technische Bundesanstalt (PTB) database and their accuracy was evaluated using a mean squared error (MSE) and a correlation coefficient (R) between the derived and directly measured Frank's leads. Based on the statistical analysis, Kors regression transformation was significantly more accurate for the derivation of the X and Y leads than the others. For the Z lead, there were no statistically significant differences in the medians between Kors regression transformation and the PLSV and QLSV methods. This paper thoroughly compared multiple VCG transformation methods to conventional VCG Frank's orthogonal lead system, used in clinical practice.

Value of Cardiogoniometry in Diagnosis of Coronary Artery Disease in Patients with Suspected Stable Ischemic Heart Disease: A Systematic Review and Meta-Analysis.

Cardiogoniometry (CGM) has been proposed as a new diagnostic tool for coronary artery disease (CAD) in recent years. Although different studies have evaluated the diagnostic value of CGM in CAD diagnosis, no pooled analysis of its diagnostic accuracy has been performed so far. This study aimed to assess the value of CGM in diagnosing CAD in patients with suspected stable ischemic heart disease (SIHD).This was a systematic review and meta-analysis conducted on available literature until May 2018. Studies considered coronary angiography as the reference standard for CAD diagnosis and reported CGM diagnostic value parameters were included. No language and time restrictions for enrolling the studies were considered. Statistical analysis was performed using Meta-DiSc software.The findings of the 10 studies published in 9 articles were enrolled in the meta-analysis. Overall pooled sensitivity was 71.7% (69.1 to 74.1; Cochrane Q = 39.5; P < 0.00001; I2 = 77.3%), and pooled specificity was 78.8% (76.3 to 81.1; Cochrane Q = 37.39; P < 0.00001; I2 = 75.9%). Regarding Egger's regression test (P = 0.32), there was no published bias in the studies.It seems that CGM, as an easy-to-use and non-invasive modality, should be considered as a part of risk stratifying strategies for CAD in patients with SIHD, mainly in patients with contraindications for stress tests. However, further studies with a high quality of methodology are still needed to assess the diagnostic value of CGM for CAD in patients with suspected SIHD.