Ventricular Activation Research Articles

Assessment of left ventricular activation conduction during left bundle branch area pacing in heart failure patients: A novel criterion to determine left bundle branch capture

Assessment of left ventricular activation conduction during left bundle branch area pacing in heart failure patients: A novel criterion to determine left bundle branch capture

Ultra-high-frequency ECG volumetric and negative derivative epicardial ventricular electrical activation pattern

From precordial ECG leads, the conventional determination of the negative derivative of the QRS complex (ND-ECG) assesses epicardial activation. Recently we showed that ultra-high-frequency electrocardiography (UHF-ECG) determines the activation of a larger volume of the ventricular wall. We aimed to combine these two methods to investigate the potential of volumetric and epicardial ventricular activation assessment and thereby determine the transmural activation sequence. We retrospectively analyzed 390 ECG records divided into three groups-healthy subjects with normal ECG, left bundle branch block (LBBB), and right bundle branch block (RBBB) patients. Then we created UHF-ECG and ND-ECG-derived depolarization maps and computed interventricular electrical dyssynchrony. Characteristic spatio-temporal differences were found between the volumetric UHF-ECG activation patterns and epicardial ND-ECG in the Normal, LBBB, and RBBB groups, despite the overall high correlations between both methods. Interventricular electrical dyssynchrony values assessed by the ND-ECG were consistently larger than values computed by the UHF-ECG method. Noninvasively obtained UHF-ECG and ND-ECG analyses describe different ventricular dyssynchrony and the general course of ventricular depolarization. Combining both methods based on standard 12-lead ECG electrode positions allows for a more detailed analysis of volumetric and epicardial ventricular electrical activation, including the assessment of the depolarization wave direction propagation in ventricles.

How to treat cardiac dyssynchrony in heart failure with reduced ejection fraction

Abstract Cardiac resynchronization therapy (CRT) has become part of the standard of care for symptomatic patients with heart failure, reduced ejection fraction (HRrEF), and wide QRS, despite optimal medical therapy. Device technology, operator experience, and post-implant optimization on follow-up have significantly improved CRT response during the last decade. In parallel, conduction system pacing (CSP) has emerged as a new and potentially better tool for maintaining physiological ventricular activation in patients with antibradycardia pacing, as well as an alternative for dyssynchrony correction in HFrEF patients. The current review focuses on cardiac dyssynchrony pathophysiology and correction methods, clinical evidence on CRT and CSP as therapies for cardiac dyssynchrony, and the role of each according to clinical evidence and current guidelines for HFrEF treatment.

Digital twinning of the human ventricular activation sequence to Clinical 12-lead ECGs and magnetic resonance imaging using realistic Purkinje networks for in silico clinical trials

Cardiac in silico clinical trials can virtually assess the safety and efficacy of therapies using human-based modelling and simulation. These technologies can provide mechanistic explanations for clinically observed pathological behaviour. Designing virtual cohorts for in silico trials requires exploiting clinical data to capture the physiological variability in the human population. The clinical characterisation of ventricular activation and the Purkinje network is challenging, especially non-invasively. Our study aims to present a novel digital twinning pipeline that can efficiently generate and integrate Purkinje networks into human multiscale biventricular models based on subject-specific clinical 12-lead electrocardiogram and magnetic resonance recordings. Essential novel features of the pipeline are the human-based Purkinje network generation method, personalisation considering ECG R wave progression as well as QRS morphology, and translation from reduced-order Eikonal models to equivalent biophysically-detailed monodomain ones. We demonstrate ECG simulations in line with clinical data with clinical image-based multiscale models with Purkinje in four control subjects and two hypertrophic cardiomyopathy patients (simulated and clinical QRS complexes with Pearson's correlation coefficients > 0.7). Our methods also considered possible differences in the density of Purkinje myocardial junctions in the Eikonal-based inference as regional conduction velocities. These differences translated into regional coupling effects between Purkinje and myocardial models in the monodomain formulation. In summary, we demonstrate a digital twin pipeline enabling simulations yielding clinically consistent ECGs with clinical CMR image-based biventricular multiscale models, including personalised Purkinje in healthy and cardiac disease conditions.

Ultra-High-Frequency ECG in Cardiac Pacing and Cardiac Resynchronization Therapy: From Technical Concept to Clinical Application.

Identifying electrical dyssynchrony is crucial for cardiac pacing and cardiac resynchronization therapy (CRT). The ultra-high-frequency electrocardiography (UHF-ECG) technique allows instantaneous dyssynchrony analyses with real-time visualization. This review explores the physiological background of higher frequencies in ventricular conduction and the translational evolution of UHF-ECG in cardiac pacing and CRT. Although high-frequency components were studied half a century ago, their exploration in the dyssynchrony context is rare. UHF-ECG records ECG signals from eight precordial leads over multiple beats in time. After initial conceptual studies, the implementation of an instant visualization of ventricular activation led to clinical implementation with minimal patient burden. UHF-ECG aids patient selection in biventricular CRT and evaluates ventricular activation during various forms of conduction system pacing (CSP). UHF-ECG ventricular electrical dyssynchrony has been associated with clinical outcomes in a large retrospective CRT cohort and has been used to study the electrophysiological differences between CSP methods, including His bundle pacing, left bundle branch (area) pacing, left ventricular septal pacing and conventional biventricular pacing. UHF-ECG can potentially be used to determine a tailored resynchronization approach (CRT through biventricular pacing or CSP) based on the electrical substrate (true LBBB vs. non-specified intraventricular conduction delay with more distal left ventricular conduction disease), for the optimization of CRT and holds promise beyond CRT for the risk stratification of ventricular arrhythmias.

Structure of cardiac rhythm disorders in patients with obesity and associated with it dyslipidemia as an arrhythmogenic factor

Obesity is a global public health problem in the twenty-first century. The most adverse it’s effects are associated with visceral type, with accumulation of epicardial fat, showing high metabolic activity, dysfunction and important role in the development of lipotoxic cardiomyopathy linked with significant morphological and functional myocardial changes, accompanying by high risk of heart rhythm disorders. The aim of the study: to identify structure (frequency and character) of cardiac arrhythmias in men of employable age with visceral obesity, to establish the relationship of arrhythmias with features of the blood lipid spectrum of these patients. Material and methods. 98 men with abdominal obesity and 46 overweight patients were examined. The control group consisted of 40 healthy patients with normal body weight. All the patients were undergone ECG monitoring, echocardiography and analysis of serum lipid levels. Results. The presence of obesity is statistically significantly associated with the risk of supraventricular couplets, frequent ventricular extrasystoles, sinus arrhythmia and atrial fibrillation. The increase in the severity of obesity was accompanied by a tendency to a greater frequency of arrhythmias: in obesity of I degree, the frequency of atrial fibrillation was 12.3%, II–III degree — 21.2%, p = 0.25; frequent ventricular extrasystoles with similar degrees of obesity — 13.8% and 21.1%, respectively. Atrial fibrillation was significantly more often detected against the background of lipid disorders, mainly with a decrease in HDLP. Conclusion. The main type of heart rhythm disturbance in patients with obesity are supraventricular arrhythmias, mainly atrial fibrillation, the frequency of which increases in proportion to the increase in the patient's body weight. Abdominal obesity leads to an increase in ventricular ectopic activity. Dyslipidemia is the one of risk factors for arrhythmias in these patients.

Dyssynchronous heart failure models in canines: New insights into electrocardiographic, echocardiographic and histological features.

We investigated the similarities and differences between two experimental approaches using tachy-pacing technology to induce desynchronized heart failure in canines. A total of eight dogs were included in the experiment, four were tachy-paced in right ventricle apex (RVAP) and 4 were paced in right atrium after the ablation of left bundle branch to achieve left bundle branch block (RAP+LBBB). Three weeks of follow-up were conducted to observe the changes in cardiac function and myocardial staining was performed at the end of the experiment. Both experimental approaches successfully established heart failure with reduced ejection fraction models, with similar trends in declining cardiac function. The RAP+LBBB group exhibited a prolonged overall ventricular activation time, delayed left ventricular activation, and lesser impact on the right ventricle. The RVAP approach led to a reduction in overall right ventricular compliance and right ventricular enlargement. The RAP+LBBB group exhibited significant reductions in left heart compliance (LVGLS, %: RAP+LBBB -12.60 ± 0.12 to -5.93 ± 1.25; RVAP -13.28 ± 0.62 to -8.05 ± 0.63, p = 0.023; LASct, %: RAP+LBBB -15.75 ± 6.85 to -1.50 ± 1.00; RVAP -15.75 ± 2.87 to -10.05 ± 6.16, p = 0.035). Histological examination revealed more pronounced fibrosis in the left ventricular wall and left atrium in the RAP+LBBB group while the RVAP group showed more prominent fibrosis in the right ventricular myocardium. Both approaches establish HFrEF models with comparable trends. The RVAP group shows impaired right ventricular function, while the RAP+LBBB group exhibits more severe decreased compliance and fibrosis in left ventricle.

In Vivo Cardiac Electrophysiology in Mice: Determination of Atrial and Ventricular Arrhythmic Substrates.

Cardiac arrhythmias are a common cardiac condition that might lead to fatal outcomes. A better understanding of the molecular and cellular basis of arrhythmia mechanisms is necessary for the development of better treatment modalities. To aid these efforts, various mouse models have been developed for studying cardiac arrhythmias. Both genetic and surgical mouse models are commonly used to assess the incidence and mechanisms of arrhythmias. Since spontaneous arrhythmias are uncommon in healthy young mice, intracardiac programmed electrical stimulation (PES) can be performed to assess the susceptibility to pacing-induced arrhythmias and uncover the possible presence of a proarrhythmogenic substrate. This procedure is performed by positioning an octopolar catheter inside the right atrium and ventricle of the heart through the right jugular vein. PES can provide insights into atrial and ventricular electrical activity and reveal whether atrial and/or ventricular arrhythmias are present or can be induced. Here, we explain detailed procedures used to perform this technique, possible troubleshooting scenarios, and methods to interpret the results obtained. © 2024 Wiley Periodicals LLC. Basic Protocol: Programmed electrical stimulation in mice.

Difficulties in selecting antiarrhythmic therapy in a patient with left ventricular noncompaction and atrial septal defect: a case report

Introduction. Left ventricular noncompaction (LVNC) is a rare heterogeneous pathology characterized by a two-layered structure with a predominance of non-compact layer in the form of multiple trabeculations and pockets between them, communicating with the left ventricular cavity. One of the rare LVNC phenotypes is a combination with congenital heart defects, including atrial septal defect (ASD).Brief description. The article presents a case report describing the difficulties of selecting antiarrhythmic therapy in a patient with LVNC and ASD, complicated by arrhythmias due to heart failure. The diagnosis of LVNC was confirmed by the Petersen criterion using magnetic resonance imaging.Discussion. Cardiac arrhythmias in patients with LVNC and congenital heart defects, as a result of both anatomical and hemodynamic causes of electrical heart instability, constitute a danger of thromboembolism and sudden cardiac death, and also contribute to heart failure progression. The case is of interest due to the rare combination of LVNC and ASD, complicated by frequent episodes atrial fibrillation and premature ventricular contractions in the form of parasystoles, as well as difficulties in selecting antiarrhythmic therapy. Pulmonary vein cryoballoon ablation eliminated the source of atrial fibrillation. Ventricular ectopic activity was stopped using the anticonvulsant drug carbamazepine.

CineECG for visualization of changes in ventricular electrical activity during ischemia

BackgroundCineECG offers a visual representation of the location and direction of the average ventricular electrical activity throughout a single cardiac cycle, based on the 12‑lead ECG. Currently, CineECG has not been used to visualize ventricular activation patterns during ischemia. PurposeTo determine the changes in ventricular activity during acute ischemia with the use of CineECG, and relating this to changes in the ECG. MethodsContinuous ECG's during percutaneous coronary intervention with prolonged balloon inflation from the STAFF III database were analyzed with CineECG at baseline and every 10 s throughout the first 150 s of balloon inflation. The CineECG direction was determined for the initial QRS-complex, terminal QRS-complex, ST-segment and T-wave. Changes in the CineECG were quantified by calculating the Δangle between the direction at baseline and the direction at every 10 s of inflation. Additionally, the root mean square amplitude (rmsA) of the ST-segment was computed. Results94 patients were included. At start inflation, the median Δangle was 14.7° [7.5–33.4], 21.8° [11.4–34.2], 20.6° [8.0–43.9], and 23.5° [11.8–48.0] for the initial QRS-complex, terminal QRS-complex, ST-segment and T-wave, respectively. Meanwhile, the median rmsA increased from 0.039 mV [0.027–0.058] at baseline to 0.045 mV [0.033–0.075] at start of inflation. ConclusionsCineECG was able to detect immediate changes in ventricular electrical activity during induced ischemia, while changes in the ST-segment of the ECG were still subtle. Therefore, CineECG might support the early detection of acute ischemia, even before distinct ECG changes become visible.

Left bundle branch pacing vs biventricular pacing in heart failure patients with left bundle branch block: A systematic review and meta-analysis.

Left bundle branch pacing (LBBP) is a novel pacing modality of cardiac resynchronization therapy (CRT) that achieves more physiologic native ventricular activation than biventricular pacing (BiVP). To explore the validity of electromechanical resynchronization, clinical and echocardiographic response of LBBP-CRT. Systematic review and Meta-analysis were conducted in accordance with the standard guidelines as mentioned in detail in the methodology section. In our analysis, the success rate of LBBP-CRT was determined to be 91.1%. LBBP-CRT significantly shortened QRS duration, with significant improvement in echocardiographic parameters, including left ventricular ejection fraction, left ventricular end-diastolic diameter and left ventricular end-systolic diameter in comparison with BiVP-CRT. A significant reduction in New York Heart Association class and B-type natriuretic peptide levels was also observed in the LBBP-CRT group vs BiVP-CRT group. Lastly, the LBBP-CRT cohort had a reduced pacing threshold at follow-up as compared to BiVP-CRT.

Current Role of Electrocardiographic Imaging in Patient Selection for Cardiac Resynchronization Therapy.

Cardiac resynchronization therapy (CRT) is a recognized therapy for heart failure with altered ejection fraction and abnormal left ventricular activation time. Since the introduction of the therapy, a 30% rate of non-responders is observed and unchanged. The 12-lead ECG remains the only recommended tool for patient selection to CRT. The 12-lead ECG is, however, limited in its inability to provide a precise pattern of regional electrical activity. Electrocardiographic imaging (ECGi) provides a non-invasive detailed mapping of cardiac activation and therefore appears as a promising tool for CRT candidates. The non-invasive ventricular activation maps acquired by ECGi have been primarily explored for the diagnosis and guidance of therapy in patients with atrial or ventricular tachyarrhythmia. However, the accuracy of the system in this field is lacking and needs further improvement before considering a clinical application. On the other hand, its use for patient selection for CRT is encouraging. In this review, we introduce the technical considerations and we describe how ECGi can precisely characterize ventricular activation, especially in patients with left bundle branch block, thus identifying the electrical substrate responsive to CRT.

Long QT syndrome induced by elevated dose of Fluoxetine Cloridrate: case report

Introduction: Long QT syndrome is a clinical condition that affects cardiac repolarization with an increased risk for the development of severe ventricular arrhythmias. The acquired form can be induced by drugs, such as selective serotonin reuptake inhibitors. Case report: E.A.C.G., female, 83 years-old, previously diagnosed with major depressive disorder in use of Fluoxetine the 80mg/day, was admitted in the emergency department after a syncopal event. An important widening of the QT interval was noted on the occasion, with a corrected value of 580ms. A 24-hour Holter monitoring showed increased ectopic ventricular activity (18% of beats), prolonged QT interval (up to 630 ms), and high-complexity ectopic ventricular beats. Non-sustained ventricular tachycardia was also observed (1030 episodes). The prolonged QT interval was associated to an elevated dose of Fluoxetine. Discussion: We believe that the coexistence between a high dose of Fluoxetine and other risk factor such as female sex and increased age contributed to the development of the case presentation. Conclusion: The rising prevalence of depression in the geriatric population and the indiscriminate use of antidepressive agents such as selective serotonin reuptake inhibitors may contribute to an increase in potentially severe cardiovascular complications.

Surpoint algorithm for improved guidance of ablation for ventricular tachycardia (SURFIRE-VT): A pilot study.

The utility of ablation index (AI) to guide ventricular tachycardia (VT) ablation in patients with structural heart disease is unknown. The aim of this study was to assess procedural characteristics and clinical outcomes achieved using AI-guided strategy (target value 550) or conventional non-AI-guided parameters in patients undergoing scar-related VT ablation. Consecutive patients (n = 103) undergoing initial VT ablation at a single center from 2017 to 2022 were evaluated. Patient groups were 1:1 propensity-matched for baseline characteristics. Single lesion characteristics for all 4707 lesions in the matched cohort (n = 74) were analyzed. The impact of ablation characteristics was assessed by linear regression and clinical outcomes were evaluated by Cox proportional hazard model. After propensity-matching, baseline characteristics were well-balanced between AI(n = 37) and non-AI(n = 37) groups. Lesion sets were similar (scar homogenization [41% vs. 27%;p = .34], scar dechanneling [19% vs. 8%;p = .18], core isolation [5% vs.11%;p = .4],linear and elimination late potentials/local abnormal ventricular activities[35% vs. 44%;p = .48], epicardial mapping/ablation [11% vs.14%;p = .73]). AI-guided strategy had 21% lower procedure duration (-47.27 min, 95% confidence interval[CI][-81.613, -12.928];p = .008), 49% lower radiofrequency time per lesion (-13.707 s, 95%CI[-17.86, -9.555];p < .001), 21% lower volume of fluid administered (1664 cc[1127, 2209] vs. 2126 cc [1750, 2593];p = .005). Total radiofrequency duration (-339 s [-24%], 95%CI[-776, 62];p = .09) and steam pops (-155.6%, 95%CI[19.8%,-330.9%];p = .08) were nonsignificantly lower in the AI group. Acute procedural success (95% vs.89%;p = .7) and VT recurrence (0.97, 95% CI[0.42-2.2];p = .93) were similar for both groups. Lesion analysis (n = 4707) demonstrated a plateau in the magnitude of impedance drops once reaching an AI of 550-600. In this pilot study, an AI-guided ablation strategy for scar-related VT resulted in shorter procedure time and average radiofrequency time per lesion with similar acute procedural and intermediate-term clinical outcomes to a non-AI-guided approach utilizing traditional ablation parameters.

Transfiguration of Human Atrioventricular Conduction Axis with His bundle Pacing: Effect on Underlying Bundle Branch Block

His bundle pacing comes with the expectation of avoiding morbidity and mortality associated with pacing the ventricular myocardium. The paced complex typically exhibits a delta wave and resembles the relatively normal QRS complex of fasciculoventricular preexcitation. In patients with atrioventricular conduction disease, His bundle pacing ‘corrects’ both right and left bundle branch block. Conduction block is known to have a diffuse substrate and mechanism of correction remains unclear. In 51 patients with normal QRS complex, 35 patients with right bundle branch block and left axis deviation, and 41 patients with left bundle branch block we analyzed the changes in the paced QRS complex. In all patients His bundle pacing caused a decrease in ventricular activation time, an increase in lead 1 voltage, an inferior shift in the frontal QRS axis, and a rightward shift in R wave transition in the precordial leads. In patients with normal QRS, despite these changes, the paced QRS remained in normal range. In left bundle branch block, these changes resulted in decrease of prolonged ventricular activation time, increased lead 1 voltage , and normalized the delayed R wave transition in precordial leads. The correction of right bundle branch block suggested that the right ventricular free wall was being activated earlier. This was consistent with early rightward transition of precordial R waves and the inferior QRS axis and the known base to apex activation of right ventricular wall in fasciculoventricular preexcitation. We conclude that the QRS complex in normal range, seen in fasciculoventricular preexcitation, is caused by rapidly conducting, base-to-apex, and septum to lateral wall activation in both left and right ventricles. This would explain the correction of left axis deviation and reversal of delayed lateral wall activation in right and left bundle branch block, by His bundle pacing.

A porcine large animal model of radiofrequency ablation-induced left bundle branch block.

Electrocardiographic (ECG) features of left bundle branch (LBB) block (LBBB) can be observed in up to 20%-30% of patients suffering from heart failure with reduced ejection fraction. However, predicting which LBBB patients will benefit from cardiac resynchronization therapy (CRT) or conduction system pacing remains challenging. This study aimed to establish a translational model of LBBB to enhance our understanding of its pathophysiology and improve therapeutic approaches. Fourteen male pigs underwent radiofrequency catheter ablation of the proximal LBB under fluoroscopy and ECG guidance. Comprehensive clinical assessments (12-lead ECG, bloodsampling, echocardiography, electroanatomical mapping) were conducted before LBBB induction, after 7, and 21days. Three pigs received CRT pacemakers 7days after LBB ablation to assess resynchronization feasibility. Following proximal LBB ablation, ECGs displayed characteristic LBBB features, including QRS widening, slurring in left lateral leads, and QRS axis changes. QRS duration increased from 64.2 ± 4.2ms to 86.6 ± 12.1ms, and R wave peak time in V6 extended from 21.3 ± 3.6ms to 45.7 ± 12.6ms. Echocardiography confirmed cardiac electromechanical dyssynchrony, with septal flash appearance, prolonged septal-to-posterior-wall motion delay, and extended ventricular electromechanical delays. Electroanatomical mapping revealed a left ventricular breakthrough site shift and significantly prolonged left ventricular activation times. RF-induced LBBB persisted for 3weeks. CRT reduced QRS duration to 75.9 ± 8.6ms, demonstrating successful resynchronization. This porcine model accurately replicates the electrical and electromechanical characteristics of LBBB observed in patients. It provides a practical, cost-effective, and reproducible platform to investigate molecular and translational aspects of cardiac electromechanical dyssynchrony in a controlled and clinically relevant setting.

Visualization of Left Ventricular Endocardium Activation Time during Cardiac Conduction System Pacing

Introduction. Right ventricular myocardial pacing leads to asynchronous contraction of the left ventricle (LV) and can impair its contractility over time. Stimulation of the conduction system of the heart ensures physiological activation of the ventricles.&#x0D; The aim. To visualize the pattern of propagation of the electrical front on the activation map of the LV endocardium during conduction system pacing and during right ventricular myocardial pacing.&#x0D; Materials and methods. In two patients with the conduction system pacing, who were operated at the National Amosov Institute of Cardiovascular Surgery, invasive LV activation mapping was performed on various options of cardiac pacing using the EnSite Precision TM navigation system. One patient with complete atrioventricular block had nonselective His bundle pacing. The second patient had dilated cardiomyopathy and indications for cardiac resynchronization therapy and ablation of the atrioventricular junction due to chronic tachyform of atrial fibrillation. After an unsuccessful attempt to place LV lead in coronary sinus, a lead for left bundle branch pacing was implanted. Different activation maps of the LV endocardium were built in two patients with two types of cardiac pacing: right ventricular myocardial pacing and cardiac conduction system pacing.&#x0D; Results. The total LV endocardial activation time was significantly different in the two studied patients with different pacing options. In a patient with non-selective stimulation of His bundle, the total LV endocardial activation time was 43 ms (QRS width 126 ms, the interval from the stimulus to the peak of the R wave in lead V6 78 ms). After switching to right ventricular myocardial pacing with a decrease in the pacing amplitude, the total LV endocardial activation time prolonged to 90 ms (QRS width 165 ms, the interval from the stimulus to the peak of the R wave in lead V6 117 ms). In a patient with left bundle branch pacing, total LV endocardial activation time was 51 ms (QRS width 160 ms, the interval from the stimulus to the peak of the R wave in lead V6 66 ms). With switching exclusively to right ventricular pacing the total LV endocardial activation time prolonged to 93 ms (stimulated QRS width 180 ms). At the same time, the activation pattern of the LV endocardium was significantly different, since the right ventricular lead was located closer to the apex.&#x0D; Conclusions. Conduction system pacing provides rapid physiological LV activation and potentially avoids the negative consequences of asynchronous slow ventricular activation during right ventricular pacing.

Short-term paroxysmal atrial fibrillation detection with intra- and inter-patient paradigm based on R-R intervals

Paroxysmal Atrial Fibrillation (PAF) may lead to the decline of atrial mechanism and hemodynamic disturbance, which is the major risk factor for stroke, myocardial infarction, heart failure and other diseases. Although a number of methods have been developed to detect PAF, they rely on long ECG signals. Furthermore, most studies are only for the intra-patient test, ignoring individual specificity. Therefore, this paper proposes an automatic detection algorithm based on the combination of RR interval time-domain and nonlinear features to detect short-term PAF. The proposed features reflect the underlying physiological phenomenon of highly irregular ventricular activity caused by atrial unstable conduction. These include changes in morphological features and intrinsic changes in the cardiac dynamic system, which can capture subtle changes in early short-term PAF episodes and attenuate specificity between individuals. Finally, the random forest algorithm was used to detect the MIT-BIH Atrial Fibrillation Database and MIT-BIH Arrhythmia Database with intra-patient and inter-patient paradigm. The results show that the two databases’ algorithm accuracy in different paradigms of intra-patient and inter-patient have achieved more than 99.50% and 95.50%, respectively. Therefore, the proposed algorithm has a potential application for clinical monitoring.

A new bipolar precordial electrocardiographic lead configuration for specific evaluation of atrial depolarization in healthy dogs.

The Lewis lead is an EGC configuration used to detect atrial activity and its relationship with ventricular activity. However, no equivalent configuration has been proposed in veterinary medicine. Therefore, this study explored new bipolar lead configurations to evaluate atrial depolarization and investigated their characteristics by comparing them with conventional leads. The authors hypothesized that a lead with a high absolute value of the P wave (|P|) and a high ratio of the P wave to the QRS complex (|P|/|QRS|) might be an appropriate configuration. 6 laboratory Beagles were used. Electrocardiograms were recorded using bipolar limb leads (I, II, III, aVL, aVF, and aVR) and unipolar precordial leads (C2, C3, C4, C5, C6, M1, M2, M5, M6, 1st-R, CV6LL, and V10) in the standing position. The new bipolar leads were attached in the following configuration: the negative electrode was attached to M6, and the positive electrode was sequentially applied to M1 and M2. The leads were named M6M1 and M6M2. The waveforms obtained using the new bipolar leads M6M1 and M6M2 showed significantly higher |P|/|QRS| and |P| values than those obtained using conventional limb leads and precordial leads. The new leads achieved a specific enhancement of atrial activity conducted at a reduced ventricular amplitude and increased atrial amplitude, similar to the Lewis lead in human medicine. These findings suggest that M6M1 and M6M2 could be supplemental lead configurations to identify P waves without amplifying the QRS waves compared to conventional methods.

Emerging Technologies in Cardiac Pacing.

Cardiac pacing to treat bradyarrhythmias has evolved in recent decades. Recognition that a substantial proportion of pacemaker-dependent patients can develop heart failure due to electrical and mechanical dyssynchrony from traditional right ventricular apical pacing has led to development of more physiologic pacing methods that better mimic normal cardiac conduction and provide synchronized ventricular contraction. Conventional biventricular pacing has been shown to benefit patients with heart failure and conduction system disease but can be limited by scarring and fibrosis. His bundle pacing and left bundle branch area pacing are novel techniques that can provide more physiologic ventricular activation as an alternative to conventional or biventricular pacing. Leadless pacing has emerged as another alternative pacing technique to overcome limitations in conventional transvenous pacemaker systems. Our objective is to review the evolution of cardiac pacing and explore these new advances in pacing strategies.