T-wave Amplitude Research Articles

Smoothing filter design: A general framework

Signal filtering/smoothing is a challenging problem arising in many applications ranging from image, speech, radar and biological signal processing. In this paper, we present a general framework to signal smoothing. The key idea is to use a suitable linear (time-variant or time-invariant) differential equation model in the regularization of an optimization problem. The presented approach has many applications in signal processing. Specifically, the quadratic variation (QV) regularization and smoothness priors are special cases of the proposed framework. These two methods are particularly suited for polynomial signal smoothing, as they use the derivatives of the signal in the regularization term of the optimization problem. Therefore, their performance is significantly decreased for signals that cannot be well modeled with a low order polynomial function. The approach presented in this paper was used to overcome this limitation. As proof of other applications, it was employed for designing an extension of QV regularization to remove the baseline wander in electrocardiogram (ECG), simultaneous tracking of powerline interference and baseline wander, and T-wave amplitude computation.

Prevalence and diagnostic significance of de-novo 12-lead ECG changes after COVID-19 infection in elite soccer players

Background and aimThe efficacy of pre-COVID-19 and post-COVID-19 infection 12-lead ECGs for identifying athletes with myopericarditis has never been reported. We aimed to assess the prevalence and significance of de-novo...

Using a Smartwatch to Record Precordial Electrocardiograms: A Validation Study

Smartwatches that support the recording of a single-lead electrocardiogram (ECG) are increasingly being used beyond the wrist, by placement on the ankle and on the chest. However, the reliability of frontal and precordial ECGs other than lead I is unknown. This clinical validation study assessed the reliability of an Apple Watch (AW) to obtain conventional frontal and precordial leads as compared to standard 12-lead ECGs in both subjects without known cardiac anomalies and patients with underlying heart disease. In 200 subjects (67% with ECG anomalies), a standard 12-lead ECG was performed, followed by AW recordings of the standard Einthoven leads (leads I, II, and III) and precordial leads V1, V3, and V6. Seven parameters (P, QRS, ST, and T-wave amplitudes, PR, QRS, and QT intervals) were compared through a Bland-Altman analysis, including the bias, absolute offset, and 95% limits of agreement. AW-ECGs recorded on the wrist but also beyond the wrist had similar durations and amplitudes compared to standard 12-lead ECGs. Significantly greater amplitudes were measured by the AW for R-waves in precordial leads V1, V3, and V6 (+0.094 mV, +0.149 mV, +0.129 mV, respectively, all p < 0.001), indicating a positive bias for the AW. AW can be used to record frontal, and precordial ECG leads, paving the way for broader clinical applications.

Possibilities of a portable electrocardiogram and pulse wave recorder in detecting left ventricular systolic dysfunction

Highlights. The article presents a novel and unique method for assessment of left ventricular systolic disfunction using electrocardiography and photoplethysmography data. This method will improve and simplify the detection of cardiovascular diseases.Aim. To evaluate left ventricular (LV) systolic function using electrocardiogram (ECG) and photoplethysmogram (PPG) signals recorded by a single-channel ECG and PPG-based monitor.Methods. The prospective study included 489 patients over 18 years old with various cardiovascular diseases. All participants underwent echocardiography to determine the main indicators of LV systolic function: LV ejection fraction (EF), LV outflow tract velocity time integral (LVOT VTI), and global longitudinal strain (GLS). Moreover, all patients underwent 1-lead ECG and PPG recording using a single-channel ECG and PPG-based monitor (CardioQvark). The obtained data were analyzed, and ROC curve analysis was performed.Results. We have identified ECG and PPG parameters associated with a decrease in LV contractile function. During the analysis, the ECG, T-wave amplitude (TA) and RonsF parameters showed the highest diagnostic accuracy. With EF below 55%, the area under the ROC curve (AUC) was 0.822, sensitivity (Se) 80%, specificity (Sp) 69% in EF below 55% in TA; in RonsF AUC was 0.743, Se 81%, Sp 77%. With EF below 40%, AUC was 0.915, Se 85%, Sp 83% in TA, and in RonsF AUC was 0.844, Se 82%, Sp 82%. Diagnostic accuracy of ECG signals in case of LVOT VTI lower than 16 cm was measured: TA (AUC 0.755, Se 82%, Sp 70%), RonsF (AUC 0.620, Se 77%, Sp 72%). PPG signals were not significantly associated with reduced EF; however, the pulse wave parameters were associated with lower LVOT VTI: in DP-B0 AUC was 0.687, Se 71%, Sp 74%. The combination of ECG and PPG signals was significantly associated with EF below 40% (RonsF * DP-SEP (AUC 0.877, Se 86%, Sp 85%). ECG and PPG signals were not associated with LV GLS.Conclusion. Assessment of LV systolic function can be performed by analyzing ECG and PPG signals recorded using a portable single-channel CardioQvark monitor.

Electrocardiogram-based deep learning improves outcome prediction following cardiac resynchronization therapy.

This study aims to identify and visualize electrocardiogram (ECG) features using an explainable deep learning-based algorithm to predict cardiac resynchronization therapy (CRT) outcome. Its performance is compared with current guideline ECG criteria and QRSAREA. A deep learning algorithm, trained on 1.1 million ECGs from 251 473 patients, was used to compress the median beat ECG, thereby summarizing most ECG features into only 21 explainable factors (FactorECG). Pre-implantation ECGs of 1306 CRT patients from three academic centres were converted into their respective FactorECG. FactorECG predicted the combined clinical endpoint of death, left ventricular assist device, or heart transplantation [c-statistic 0.69, 95% confidence interval (CI) 0.66-0.72], significantly outperforming QRSAREA and guideline ECG criteria [c-statistic 0.61 (95% CI 0.58-0.64) and 0.57 (95% CI 0.54-0.60), P < 0.001 for both]. The addition of 13 clinical variables was of limited added value for the FactorECG model when compared with QRSAREA (Δ c-statistic 0.03 vs. 0.10). FactorECG identified inferolateral T-wave inversion, smaller right precordial S- and T-wave amplitude, ventricular rate, and increased PR interval and P-wave duration to be important predictors for poor outcome. An online visualization tool was created to provide interactive visualizations (https://crt.ecgx.ai). Requiring only a standard 12-lead ECG, FactorECG held superior discriminative ability for the prediction of clinical outcome when compared with guideline criteria and QRSAREA, without requiring additional clinical variables. End-to-end automated visualization of ECG features allows for an explainable algorithm, which may facilitate rapid uptake of this personalized decision-making tool in CRT.

Prevalence and diagnostic significance of novel 12-lead ECG patterns following COVID-19 infection in elite soccer players

Abstract Background Identification of athletes with cardiac inflammation following COVID-19 can prevent exercise fatalities. The efficacy of pre and post COVID-19 infection electrocardiograms (ECGs) for detecting athletes with myopericarditis has never been reported. We aimed to assess the prevalence and diagnostic significance of novel 12-lead ECG patterns following COVID-19 infection in elite soccer players. Methods We conducted a multicentre study over a 2-year period involving 5 centres and 34 clubs and compared pre COVID and post COVID ECG changes in 455 consecutive athletes. ECGs were reported in accordance with the International recommendations for ECG interpretation in athletes. The following patterns were considered abnormal if they were not detected on the pre COVID-19 infection ECG: (a) biphasic T-waves; (b) reduction in T-wave amplitude by 50% in contiguous leads; (c) ST-segment depression; (d) J-point and ST-segment elevation &amp;gt;0.2 mV in the precordial leads and &amp;gt;0.1 mV in the limb leads; (e) tall T-waves ≥1.0 mV (f) low QRS-amplitude in &amp;gt;3 limb leads and (g) complete right bundle branch block. Athletes exhibiting novel ECG changes underwent cardiovascular magnetic resonance (CMR) scans. One club mandated CMR scans for all 28 (6%) athletes, despite the absence of cardiac symptoms or ECG changes. Results Athletes were aged 22±5 years (89% male and 57% white). 65 (14%) athletes reported cardiac symptoms. The mean duration of illness was 3±4 days. The post COVID ECG was performed 14±16 days following a positive PCR. 440 (97%) athletes had an unchanged post COVID-19 ECG. Of these, 3 (0.6%) had cardiac symptoms and CMRs resulted in a diagnosis of pericarditis. 15 (3%) athletes demonstrated novel ECG changes following COVID-19 infection. Among athletes who demonstrated novel ECG changes, 10 (67%) reported cardiac symptoms. 13 (87%) athletes with novel ECG changes were diagnosed with inflammatory cardiac sequelae; pericarditis (n=6), healed myocarditis (n=3), definitive myocarditis (n=2), and possible/probable myocarditis (n=2). The overall prevalence of inflammatory cardiac sequelae based on novel ECG changes was 2.8%. None of the 28 (6%) athletes, who underwent a CMR, in the absence of cardiac symptoms or novel ECG changes revealed any abnormalities. Athletes revealing novel ECG changes, had a higher prevalence of cardiac symptoms (67% v 12% p&amp;lt;0.0001) and longer symptom duration (8±8 days v 2±4 days; p&amp;lt;0.0001) compared with athletes without novel ECG changes. Among athletes without cardiac symptoms, the additional yield of novel ECG changes to detect cardiac inflammation was 20% (n=3). Conclusions 3% of elite soccer players demonstrated novel ECG changes post COVID-19 infection, of which almost 90% were diagnosed with cardiac inflammation during subsequent investigation. Most athletes with novel ECG changes exhibited cardiac symptoms. Novel ECGs changes contributed to a diagnosis of cardiac inflammation in 20% of athletes without cardiac symptoms. Funding Acknowledgement Type of funding sources: None.

Twenty-four hour variability of inverted T-waves in patients with apical hypertrophic cardiomyopathy.

BackgroundPatients with apical hypertrophic cardiomyopathy (ApHCM) have marked inverted T-waves that vary over several years. Inverted T-waves in ApHCM are unstable, but it is unclear whether this change is due to coronary artery disease (CAD) or if it is a characteristic of ApHCM itself. We aimed to study the characteristics of inverted T-waves in patients with ApHCM over the course of 24 h to improve the diagnostic indices of ApHCM.MethodsWe examined 83 patients with ApHCM and 89 patients with CAD (who served as the control group). All patients underwent a 24-h dynamic electrocardiogram (ECG). We analyzed the average depth of inverted T-waves per minute and sorted them from shallow to deep; the sorted ECG segments at the 10th, 50th, and 90th positions of the T-wave were subsequently analyzed.ResultsThe amplitudes of inverted T-waves in ApHCM corresponding to the 10th, 50th, and 90th percentiles were −5.13 ± 4.11, −8.10 ± 4.55, and −10.9 ± 5.04 mm, respectively. Changes in the degree of inverted T-waves were greater in ApHCM than in CAD. T-wave amplitudes in ApHCM were strongly associated with heart rate and circadian rhythm and only weakly associated with CAD and posture. Maximum T-wave amplitudes in the CAD group were <10 mm, while 68% of patients with ApHCM had maximum T-wave amplitudes >10 mm, and all patients with ApHCM aged <50 years had maximum T-wave amplitudes >10 mm.ConclusionNotable variations in the T-waves of patients with ApHCM were observed over 24 h. ECG examinations during states of inactivity (comparable to sleep) improved the sensitivity of the diagnosis of ApHCM. Inverted T-wave amplitudes correlated with heart rate and circadian rhythm, where T-wave changes in ApHCM may be due to the normalization of abnormal T-waves effect. Identifying T-wave amplitudes >10 mm can effectively improve the diagnostic rate of ApHCM, especially in patients aged <50 years. The short-term change in T-waves in patients with ApHCM could serve as a novel index that will help in the diagnosis of ApHCM.

Electrocardiography and heart rate variability in Göttingen Minipigs: Impact of diurnal variation, lead placement, repeatability and streptozotocin-induced diabetes

BackgroundThe Göttingen Minipig is widely used in preclinical research and safety pharmacology, but standardisation of porcine electrocardiography (ECG) is lacking. The aim of this study was to investigate diurnal effects, change over time and choice of lead on ECG morphology and heart rate variability (HRV) in healthy and streptozotocin (STZ) induced diabetic Göttingen Minipigs. MethodsDiabetes was experimentally induced using STZ in 11 Göttingen Minipigs (DIA). Seven controls (CON) were included. 24-h ECG was recorded at baseline and four months. Morphological parameters (QRS and T wave duration, P- and T-wave amplitude, PR and QT (Bazett's (QTcb) or Fridericia (QTcf) correction) intervals and ST segment), presence of cardiac arrhythmias, heart rate (HR) and HRV (time and frequency domain) were analysed. ResultsFour months after induction, DIA had decreased P-wave amplitude (P < 0.0001) and T-wave duration (P = 0.017), compared to CON. QTcb was lower in DIA, but not in CON. Both groups had decreased HR (P < 0.0001) and QRS duration (lead II, P = 0.04) and length of PR-segment increased (lead I and II, P < 0.01) while selected HRV parameters also increased (all P < 0.01). Time of day influenced HR, QRS duration, PR segment, ST segment, T- and P-wave amplitude and some parameters of HRV. Inter- and intra-observer variability of morphological measurements was low (<6%). ConclusionECG parameters were influenced by time setting, diurnal variation and lead. Some ECG and HRV changes were found in diabetic minipigs four months after STZ induction. The findings underline the need for standardisation of ECG and HRV in Göttingen Minipigs.

An ECG generative model of myocardial infarction

Background and Objective Computer-aided diagnosis (CAD) of Myocardial Infarction (MI) using machine learning depends on a large amount of clinical Electrocardiogram (ECG) data. Existing infarct ECG databases face the problem of class imbalance. Data augmentation using generative simulation models is a new approach to effectively address this problem.Methods A multiscale ECG generative model was established for ECG data augmentation. In the cellular layer, an ischemic Action Potential (AP) model was established to generate APs in cardiomyocytes with different transmural regions of infraction or different ischemic durations. In the tissue layer, a probability-driven cellular automata excitation propagation model was established to simulate the propagation speed and direction of excitation. An infarct tissue model and a coronary artery model were established to describe the spatiotemporal diversity of MI. A ventricle model, a human torso model, and a computational model of surface ECG based on field source theory were established in the heart-torso layer.Results The model generated pathological 12-lead ECGs of MI with different topography and different extent. When simulating different ventricular wall infarction, the lesions appear in the same leads as the clinical 12-lead ECG. The ST-segment decreases and the T-wave amplitude decreases, similar to the clinical ECG features when simulating subendocardial ischemia. The average fidelity of the 12-lead ECG the model generated is 95.6%, according to the designed DTW-GRA distance algorithm.Conclusions The generative model considers the electrophysiological properties of the natural heart, the pathology of myocardial infarction, and the diversity of clinical ECGs. The model can provide many reliable samples for machine learning of MI.

Early ischemic ST-segment and T-wave changes during balloon angioplasty

BackgroundAcute coronary occlusion results in increased T-wave amplitude and ST-segment elevation in the ECG leads facing the ischemic region. Material and methodsWe performed continuous ECG recording in 34 patients during balloon occlusion of the left anterior descending (LAD), left circumflex (LCx) and right coronary artery (RCA). Delta (Δ) ST and ΔT amplitudes were calculated by subtracting the preinflation values from the values measured during balloon inflation. ResultsOcclusion of the LAD resulted in greater increase in the amplitude of the T wave than of the ST segment in lead V2 (ΔT +3.4 mm, inter-quartile range [IQR] 1—6 mm; ΔST +1.4 mm, 0.5—3 mm). During RCA occlusion, ΔST and ΔT didn't differ significantly. LCx occlusion resulted in significant differences between ΔST and ΔT in all leads, except aVF and V3-V4. In two patients (LCx), we observed a biphasic ST-T response: an initial negative change of the T-wave amplitude was followed by a positive change in leads V1-V2. In leads II, III, aVF and V4-V6, there was an initial positive change, followed by a final negative change towards the end of the occlusion. ConclusionContinuous 12‑lead ECG recording during balloon occlusion of the LCx resulted in significant differences between the ΔST and ΔT values in all leads except aVF and V3-V4. LAD and RCA occlusion resulted in less evident differences between the ST-segment and T-wave changes. A change in polarity of T-wave changes during balloon occlusion (initial negative and final positive change, or vice versa) proved to be a rare finding.

Pathophysiological study of the loss of function of the Tbx5 gene in the ventricular conduction system

Patients with Holt-Oram syndrome suffer from cardiac conduction disorders and are often associated with mutations in the gene encoding the cardiac transcription factor Tbx5. In mice, it has been shown that Tbx5 is essential for maintaining the structure and function of the atrioventricular node and His bundle. Conditional deletion of Tbx5 in the adult mouse heart is associated with conduction defects, slowing of the ventricular conduction system (VCS), QRS prolongation, bundle branch blocks and atrial fibrillation. However, there were no data on the morphological and functional consequences of a cardiac deletion of Tbx5 during embryonic development. The aim is to analyze the morphological and functional consequences in the adult heart of the deletion of the Tbx5 gene in the progenitor cells of the cardiac VCS at the fetal stage. Tbx5 gene was inactivated in VCS progenitors using Cx40-CreERT2:Tbx5 floxed/floxed transgenic mice. Cre-mediated recombination was induced by oral gavage of pregnant females at E13-14 during trabecular compaction. Surface ECGs were achieved monthly until 3 months of age, when immunofluorescence staining was performed on mouse hearts. In 3-week-old Tbx5Fl/Fl mice ( n = 16), ECG analysis showed a decrease in P- ( P < 0.01) and T-wave amplitudes ( P < 0.01) and an increased QRS interval duration ( P < 0.05) compared to controls ( n = 12). At 2 months, the mice did not show any worsening of the phenotype. In addition, severe functional defects in Tbx5Fl/Fl mice, including atrial susceptibility, extrasystoles, and arrhythmias were observed by 3 weeks of age. Moreover, left bundle branches block and slowing of ventricular depolarization were also detected in Tbx5Fl/Fl mice. A β-adrenergic stimulation revealed a large tendency for atrial fibrillation and extrasystoles in 88% of Tbx5Fl/Fl mice against 50% of Tbx5Fl/+ mice and 43% of control mice. In 2-month-old Tbx5Fl/Fl mice, Purkinje Fiber cells composing the fast-VCS are still present, however, they lose the expression of Contactin-2 and Connexin-40. Furthermore, we observed a drastic loss of Connexin-43 in Tbx5-deleted contractile cardiomyocytes that are close to the VCS, which may have resulted in decreased signal propagation. In this study, we demonstrated that Tbx5 deletion in VCS progenitors prevents their maturation and hence the expression of rapid conduction markers causing disturbances in the propagation of ventricular electrical activity.

Impact of right ventricular pacing site on the subcutaneous ICD sensing-a step towards personalised device therapy?

Patients with an existing subcutaneous implantable cardiac defibrillator (S-ICD) may develop a pacing indication. When transvenous pacing is not feasible, combining an S-ICD and a leadless pacemaker (LP) can be a reasonable option. There are reports of concomitant use of both devices. However, the effect of pacing on the S-ICD sensing is not well studied. We hypothesise that pacing changes R and T-wave amplitudes, causing changes in R:T ratios as perceived by a S-ICD, increasing the risk for T wave oversensing (TWO) during paced rhythm with a subsequent risk of inappropriate shocks. This is a prospective study in patients undergoing electrophysiological studies. Participants were fitted with a Holter®, and the leads were placed to correspond to the vectors of an S-ICD. The right ventricle was paced at four positions for 10 beats each at 8mA/2ms. The Holter® traces were analysed, using two-way analysis of variance (ANOVA) to assess the effect of pacing on the R:T ratio. Forty-seven patients (age 56.02 ± 16.02, 72% male) were enrolled (81% structurally normal heart, 15% dilated cardiomyopathy, 2% ischaemic cardiomyopathy, and 2% adult congenital heart disease). Age, sex, and aetiology had no effect on the R:T ratio. Pacing caused significant changes in the R:T ratio. There was no significant difference in the R:T ratios between the pacing sites (p < 0.001). Pacing alters the R:T ratio significantly in most patients, theoretically increasing the risk for TWO and inappropriate shocks. Tailored programming for both devices is important for concomitant use of LPs and S-ICDs.

Changes in the Cardiotoxic Effects of Lead Intoxication in Rats Induced by Muscular Exercise.

Exposure to lead is associated with an increased risk of cardiovascular diseases. Outbred white male rats were injected with lead acetate intraperitoneally three times a week and/or were forced to run at a speed of 25 m/min for 10 min 5 days a week. We performed noninvasive recording of arterial pressure, electrocardiogram and breathing parameters, and assessed some biochemical characteristics. Electrophoresis in polyacrylamide gel was used to determine the ratio of myosin heavy chains. An in vitro motility assay was employed to measure the sliding velocity of regulated thin filaments on myosin. Isolated multicellular preparations of the right ventricle myocardium were used to study contractility in isometric and physiological modes of contraction. Exercise under lead intoxication normalized the level of calcium and activity of the angiotensin-converting enzyme in the blood serum, normalized the isoelectric line voltage and T-wave amplitude on the electrocardiogram, increased the level of creatine kinase-MB and reduced the inspiratory rate. Additionally, the maximum sliding velocity and the myosin heavy chain ratio were partly normalized. The effect of exercise under lead intoxication on myocardial contractility was found to be variable. In toto, muscular loading was found to attenuate the effects of lead intoxication, as judged by the indicators of the cardiovascular system.

Comparison of TWA and PEP as indices of α2- and ß-adrenergic activation.

Pre-ejection period (PEP) and T-wave amplitude (TWA) have been used to assess sympathetic nervous system (SNS) activity. Here we report two single-blinded, placebo-controlled intravenous (IV) drug application studies in which we pharmacologically modified SNS activity with epinephrine (study 1) as well as dexmedetomidine (alpha2-agonist) and yohimbine (alpha2-antagonist) (study 2). Restricted heart rate (HR) intervals were analyzed to avoid confounding effects of HR changes. Study 1 served to replicate previous findings and to validate our approach, whereas study 2 aimed to investigate how modulation of central SNS activity affects PEP and TWA. Forty healthy volunteers (58% females) participated in study 1 (between-subject design). Twelve healthy men participated in study 2 (within-subject design). TWA and PEP were derived from ECG and impedance cardiography, respectively. Epinephrine shortened PEP and induced statistically significant biphasic TWA changes. However, although the two alpha2-drugs significantly affected PEP as expected, no effects on TWA could be detected. PEP is better suited to reflect SNS activity changes than TWA.

Clinical utility of aVR lead T-wave in electrocardiogram of patients with ST-elevation myocardial infarction

BackgroundaVR lead is often neglected in routine clinical practice largely because of its undefined clinical utility specifications. Nevertheless, positive T-wave in aVR lead has been reported to be associated with poor clinical outcomes in some cardiovascular diseases. This study aimed to prospectively investigate the prognostic value and clinical utility of T-wave amplitude in aVR lead in patients with acute ST-elevation myocardial infarction (STEMI).MethodsA total of 340 STEMI patients admitted to a tertiary heart center were consecutively included. Patients were categorized into four strata, based on T wave amplitude in aVR lead in their admission ECG (i.e. < − 2, − 1 to − 2, − 1 to 0, and ≥ 0 mV). Patients’ clinical outcomes were also recorded and statistically analyzed.ResultsIn-hospital mortality, re-hospitalization, and six-month-mortality significantly varied among four T wave strata and were higher in patients with a T wave amplitude of ≥ 0 mV (p 0.001–0.002). The groups of patients with higher T wave amplitude in aVR, had progressively increased relative risk (RR) of in-hospital mortality (RRs ≤ 0.01, 0.07, 1.00, 2.30 in four T wave strata, respectively). T wave amplitude in the cutoff point of − 1 mV exhibited a sensitivity and specificity of 95.83 (95% CI 78.88–99.89) and 49.68 (95% CI 44.04–55.33).ConclusionOur study demonstrated a significant association of positive T wave in aVR lead and adverse clinical outcomes in STEMI patients. Nevertheless, the clinical utility of T-wave amplitude at aVR lead is limited by its low discriminative potential toward prognosis of STEMI.

Electrocardiogram-based index for the assessment of drug-induced hERG potassium channel block

IntroductionDrug-induced block of the hERG potassium channel could predispose to torsade de pointes, depending on occurrence of concomitant blocks of the calcium and/or sodium channels. Since the hERG potassium channel block affects cardiac repolarization, the aim of this study was to propose a new reliable index for non-invasive assessment of drug-induced hERG potassium channel block based on electrocardiographic T-wave features. MethodsERD30% (early repolarization duration) and TS/A (down-going T-wave slope to T-wave amplitude ratio) features were measured in 22 healthy subjects who received, in different days, doses of dofetilide, ranolazine, verapamil and quinidine (all being hERG potassium channel blockers and the latter three being also blockers of calcium and/or sodium channels) while undergoing continuous electrocardiographic acquisition from which ERD30% and TS/A were evaluated in fifteen time points during the 24 h following drug administration (“ECG Effects of Ranolazine, Dofetilide, Verapamil, and Quinidine in Healthy Subjects” database by Physionet). A total of 1320 pairs of ERD30% and TS/A measurements, divided in training (50%) and testing (50%) datasets, were obtained. Drug-induced hERG potassium channel block was modelled by the regression equation BECG(%) = a·ERD30% + b·TS/A+ c·ERD30%·TS/A + d; BECG(%) values were compared to plasma-based measurements, BREF(%). ResultsRegression coefficients values, obtained on the training dataset, were: a = −561.0 s−1, b = −9.7 s, c = 77.2 and d = 138.9. In the testing dataset, correlation coefficient between BECG(%) and BREF(%) was 0.67 (p < 10−81); estimation error was −11.5 ± 16.7%. ConclusionBECG(%) is a reliable non-invasive index for the assessment of drug-induced hERG potassium channel block, independently from concomitant blocks of other ions.

Detection of T-wave Alternans in ECG Signals Using FRFT and Tensor Decomposition

T-wave alternans (TWA) refers to the periodic beat-to-beat variation in the amplitude of T-wave in the electrocardiogram (ECG) signal in an ABAB-pattern. TWA has been proven to be a very important indicator of malignant arrhythmia risk stratification. A new method to detect TWA by combining fractional Fourier transform (FRFT) and tensor decomposition is proposed. First, the T-wave vector is extracted from the ECG of each heartbeat, and its FRFT amplitudes at multiple orders are arranged to form a T-wave matrix. Then, a third-order tensor is composed of T-wave matrices of several consecutive heart beats. After tensor decomposition, projection matrices are obtained in three dimensions. The complexity of the projection matrix is measured by Shannon entropy to obtain feature vector to detect the presence of TWA. Results show that the sensitivity, specificity, and accuracy of the algorithm on the MIT-BIH database are 91.16%, 94.25%, and 92.68%, respectively. This method effectively utilizes the fractional domain information of ECG, and shows the promising potential of the FRFT in ECG signal processing.

Assessment of a Novel, 22-lead Mobile Electrocardiogram in Elite, Adolescent Footballers.

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

The Changes of T-Wave Amplitude and QT Interval Between the Supine and Orthostatic Electrocardiogram in Children With Dilated Cardiomyopathy.

Objectives: Electrocardiogram (ECG) can be affected by autonomic nerves with body position changes. The study aims to explore the ECG changes of children with dilated cardiomyopathy (DCM) when their posture changes.Materials and methods: Sixty-four children diagnosed with DCM were recruited as research group and 55 healthy children as control group. T-wave amplitude and QT interval in ECG were recorded, and their differences between supine and orthostatic ECG were compared in both groups. Subsequently, the children with DCM were followed up and the differences before and after treatment compared.Results: ① Comparisons in differences: Differences of T-wave amplitude in lead II and III, aVF, and V5 and differences of QT interval in lead II, aVL, aVF, and V5 were lower in the research group than in the control group. ② Logistic regression analysis and diagnostic test evaluation: The differences of T-wave amplitude in lead III and QT interval in lead aVL may have predictive value for DCM diagnosis. When their values were 0.00 mV and 30 ms, respectively, the sensitivity and specificity of the combined index were 37.5 and 83.6%. ③ Follow-up: In the response group, the T-wave amplitude difference in lead aVR increased and the difference of QT interval in lead V6 decreased after treatment. In the non-response group, there was no difference before and after treatment. When the combined index of the differences of T-wave amplitude difference in lead aVR and QT interval difference in lead V6, respectively, were −0.05 mV and 5 ms, the sensitivity and specificity of estimating the prognosis of DCM were 44.4 and 83.3%.Conclusions: The differences of T-wave amplitude and QT interval may have a certain value to estimate DCM diagnosis and prognosis.

CARDIAC EXAMINATIONS OF ANESTHETIZED STELLER SEA LIONS (EUMETOPIAS JUBATUS), NORTHERN FUR SEALS (CALLORHINUS URSINUS), AND A WALRUS (ODOBENUS ROSMARUS).

Pinniped hearts have been well described via dissection, but in vivo measurements of cardiac structure, function, and electrophysiology are lacking. Electrocardiograms (ECGs) were recorded under anesthesia from eight Steller sea lions (Eumetopias jubatus), five northern fur seals (Callorhinus ursinus), and one walrus (Odobenus rosmarus) to investigate cardiac electrophysiology in pinnipeds. In addition, echocardiograms were performed on all eight anesthetized Steller sea lions to evaluate in vivo cardiac structure and function. Measured and calculated ECG parameters included P-wave, PQ, QRS, and QT interval durations, P-, R-, and T-wave amplitudes, P- and T-wave polarities, and the mean electrical axis (MEA). Measured and calculated echocardiographic parameters included left ventricular internal diameter, interventricular septum thickness, and left ventricular posterior wall thickness in systole and diastole (using M-mode), left atrium and aortic root dimensions (using 2D), and maximum aortic and pulmonary flow velocities (using pulsed-wave spectral Doppler). ECG measurements were similar to those reported for other pinniped species, but there was considerable variation in the MEAs of Steller sea lions and northern fur seals. Echocardiographic measurements were similar to those reported for southern sea lions (Otaria flavenscens), including five out of eight Steller sea lions having a left atrial to aortic root ratio <1, which may indicate that they have an enlarged aortic root compared to awake terrestrial mammals. Isoflurane anesthesia likely affected some of the measurements as evidenced by the reduced fractional shortening found in Steller sea lions compared to awake terrestrial mammals. The values reported are useful reference points for assessing cardiac health in pinnipeds under human care.