Ventricular Activation Research Articles

PO-03-023 OUTCOMES OF LEFT BUNDLE BRANCH AREA PACING AND ATRIOVENTRICULAR NODE ABLATION IN PATIENTS WITH GROUP III PULMONARY HYPERTENSION AND ATRIAL FIBRILLATION IN REDUCING RECURRENT HOSPITALIZATION

Data on the feasibility of left bundle branch area pacing (LBBAP) and atrioventricular node (AVN) ablation in patients with pulmonary hypertension (PH) are limited. This study investigated the characteristics and outcomes of LBBAP and AVN ablation in patients with PH. This is a retrospective study of patients with PH and AF who underwent LBBAP and AVN ablation at the Cleveland Clinic between January 1, 2019 and August 1, 2022. Pre-procedural, post-procedural, and follow-up patient data were obtained. A total of 11 patients (mean age 74±10 years old, 100% female) with PH and AF who underwent concomitant LBBAP and AVN ablation were included. The etiology of PH was Group III PH in all patients (55% had COPD and 91% had restrictive lung disease), with the average pulmonary arterial systolic pressure (PASP) of 42 mmHg by echocardiogram, FEV1 of 61.9±17.4% predicted, and FVC of 59.9±7.8% predicted. Baseline ejection fraction was 57±10%, QRS duration was 96±20 ms. Concomitant LBBAP and AVN ablation was successful in all patients. Final implant characteristics included: QRS duration was 124±8 ms, left ventricular activation time was 73.7±5.4 ms; threshold 0.6±0.2 mV @ 0.4 ms and was 0.7±0.2 mV @ 0.4 ms on follow-up; impedance was 618±119 ohms and was 545±145 ohms on follow-up. Prior to the LBBAP and AVN ablation procedure, the average number of AF or heart failure (HF) hospitalizations 24 months prior to the procedure was 4.9±5.3, 64% of patients were on antiarrhythmic drugs, and 100% were on either beta-blockers or calcium channel blockers. During a mean follow-up of 21.9±15.3 months after the LBBAP and AVN ablation procedure, the average AF or HF hospitalization was 0.4±0.9, and all patients were no longer on any antiarrhythmic drugs, beta-blockers, or calcium channel blockers. There were no cases of lead dislodgement. In patients with elevated PA systolic pressure, successful LBBAP and AVN ablation with good two-year outcomes are achievable.Tabled 1Pre LBBAP and AVN ablation*Post LBBAP and AVN ablation**P-valueAF or HF hospitalizations4.9 ± 5.30.4 ± 0.9P<0.01On antiarrhythmic drugs7 (63.6%)0 (0%)P<0.01On rate control drugs11 (100%)0 (0%)NALead dislodgement-0 (0%)NALead capture threshold, mV-0.7 ± 0.2NAValues are mean ± SD or n (%) *24 months prior to LBBAP and AVN ablation **Average follow-up of 22±15 months after LBBAP and AVN ablation Open table in a new tab

PO-02-021 DIRECTION OF REPOLARIZATION IN BASELINE ECG IS PREDICTIVE OF RESPONSE TO CARDIAC RESYNCHRONIZATION THERAPY

Cardiac resynchronization therapy (CRT) is a cornerstone of treatment for advanced heart failure, but not all patients derive equal benefit from this intervention. Current approaches of using electrocardiographic and echocardiographic parameters to identify likely CRT responders demonstrate poor predictive ability. We seek to identify electrocardiographic parameters that can improve prediction of benefit with CRT This was a retrospective analysis of patients who underwent CRT-D placement at University of Pittsburgh Medical Center from 2014-2020. Patients were excluded if pre-implantation EKG or pre- and post-implantation echocardiograms were not available. Each patient’s immediate pre-implantation ECG was processed using the CineECG software (EKG Excellence) to obtain the mean temporospatial isochrone of ventricular activation. 192 features quantifying the activation and recovery pathways were computed for each patient. Response to CRT was defined as an improvement in ejection fraction (EF) of 5% on follow-up transthoracic echocardiogram 3-12 months after CRT implantation. Forward sequential feature selection was used to identify the features of highest importance based on negative logistic loss. 276 patients were included in this analysis (36% female, mean age 69 years, mean pre-procedural EF 27%). The 10 most important CineECG features were identified. When these features were used in a multivariate logistic regression, three features were independently predictive of CRT response: left bundle branch block (LBBB); leftward direction of late repolarization potentials (i.e., Tpeak - Tend rotated toward LV in the horizontal plane); and location of center-of-mass of terminal cardiac activation. Compared to CRT responders (n=169, 62%), non-responders were more likely to have abnormal direction of late repolarization potentials in both LBBB group (-0.34±0.30 vs. -0.45±0.30 vs, p=0.027) and RBBB group (0.25±0.51 vs. 0.61±0.27, p=0.031). In the latter group, direction of later repolarization potentials correlated with magnitude of change in post-procedural EF (r=0.23, p=0.016). Our findings confirm that the presence of LBBB is predictive of response to CRT. In addition, our data suggests that in patients with RBBB, a more leftward direction of late repolarization potentials is independently predictive of CRT response. Further studies into repolarization dynamics as a predictor of CRT response in RBBB are warranted.

Loss of the Tbx5 gene in the ventricular conduction system induces spontaneous ventricular arrhythmias

The ventricular conduction system (VCS) and the working myocardium (WM) derive from the same myogenic progenitors during the embryonic development. The VCS development is regulated by numerous genes including the T-box transcription factor 5 (Tbx5). In human, Tbx5 mutations cause Holt-Oram syndrome, an autosomal dominant disease associated with heart abnormalities such as arrhythmias. In adult mice, the deletion of the Tbx5 gene provoked a slowing of ventricular conduction due to a loss of the gap junction Connexin 40 and dysfunction of cardiac channels. However, it is still unknown how Tbx5 deletion affects the development and the function of the VCS. The aim is to study the consequences of the Tbx5 deletion in embryonic progenitors of the ventricular conduction system on cardiac function in adult mice. Conditional deletion of Tbx5 alleles in mice was induced by expressing the Cre recombinase under the control of the Connexin 40 (Cx40) gene. We studied two groups of mutants: Tbx5 deletion at embryonic days E13-14 targeting both the ventricular conduction system and the working myocardium (“VCS + WM” group; n = 40) and mice deleted at E18-P2 targeting only the ventricular conduction system (“VCS” group; n = 17). Surface ECGs were achieved monthly until 3 months of age, when immunostaining was performed on the left VCS. Immunostaining showed a reduced expression of the two major connexines in the ventricle (Cx40 and Cx43) and a reduced number of conductive cells in both mutants, suggesting a defective maturation of the VCS (Fig. 1). Furthermore, the loss of Cx43 was correlated with that of Tbx5, reflecting a direct transcriptional effect. Surface ECG revealed a significant increase of the ventricular activation duration in both mutants (P < 0.01). Moreover, premature ventricular contractions (PVCs) and a left QRS axis deviation were observed in both mutants. Finally, these PVCs disappeared with age in both mutants under resting conditions, and are unmasked when the heart is challenged with a β-1 adrenergic agonist. Our results provide new insights into Tbx5 targets in the VCS. Tbx5 deletion impacts the maturation and the anatomy of the VCS as proved by the deviation of the ventricular electrical axis, which even occurs when the VCS is already formed. Tbx5 appears to have a direct impact on the Gja1 gene, encoding the gap junction Cx43, which is reduced at the junction between the VCS and the WM in both mutants and may be responsible for PVCs.

Forecasting patient instability: Current advances & future opportunities

The adverse effects of conventional right ventricular (RV) apical pacing prompted the search for more physiological pacing sites, such as selective and nonselective His bundle pacing (HBP), a variant of nonselective HBP (para-Hisian pacing), and mid-septal pacing. However, knowledge of their true benefit on the physiology of ventricular activation, lead stability, and pacing thresholds is limited.We included 152 consecutive patients (mean age 61 ± 24, 63% men) in this retrospective study. Of these, 137 patients with different bradyarrhythmias underwent active fixation lead implantation at the RV apex (n = 54), para-Hisian region (n = 66), or mid interventricular septum (n = 17). Fifteen patients with ventricular preexcitation due to an accessory pathway not undergoing pacing were included as controls. A 12‑lead ECG was recorded in all patients, and cardiac electrical synchrony was assessed using the Synchromax® cross-correlation cardiac synchrony index (CSI).QRS duration was prolonged in all pacing sites: from 114 ± 28 to 160 ± 29 (RV apex), from 110 ± 28 to 122 ± 29 (para-Hisian), and from 121 ± 24 to 154 ± 30 (mid interventricular septum). The CSI was significantly improved only in patients undergoing para-Hisian pacing, despite a slight widening of the QRS interval. There was no difference in pacing thresholds and sensed R-wave voltage between pacing sites. Only 1 lead, implanted at the para-Hisian region (1.5%), was dislodged towards the mid septum 48 h after implantation but did not require repositioning.QRS duration was not associated with changes in CSI, meaning that QRS width does not significantly affect electrical synchrony.

PO-03-009 3830 LEAD TIP POSITION ON COMPUTED TOMOGRAPHY AND ELECTROPHYSIOLOGIC OUTCOMES IN LEFT BUNDLE BRANCH AREA PACING

Prior studies have evaluated the impact of lead tip distance from the LV blood pool on pacing parameters during left bundle branch area pacing (LBBAP). Few studies to date have evaluated lead tip angulation within the interventricular septum (IVS) in relation to pacing morphology on surface 12-lead ECG. To establish the observed lead tip trajectories within the interventricular septum encountered during LBBAP. Patients who underwent LBBAP implantation between 02/2019-07/2022 were retrospectively analyzed. Patients who underwent computed tomography (CT) of the chest or thorax post-implantation for any indication were included for analysis. Lead distance from the mitral annulus, lead tip distance from LV blood pool (DEBP), lead tip angle of incidence (AOI), and post-implantation electrocardiographic and pacing parameters were analyzed (Figure 1a). 38 pts were identified, out of whom 37 pts had CT images available for analysis. In the 20 pts with contrast enhanced imaging, DEBP was 2.1±1.8mm. Average observed AOI was 10.9±20.6 degrees in the axial plane (long axis; Figure 1b) and 12.4±22.2 degrees in the saggital plane (short axis; Figure 1c). Lead impedance at time of implant did not correlate strongly with axial or sagittal angle of incidence (R2=0.01 and 0.03 respectively) or with distance from LV endocardial blood pool (R2=0.04). The most commonly encountered lead insertion locations included the mid-septal (22, 59.5%), basal septal (4, 10.8%), and mid antero-septal (3, 8.1%) positions (Figure 1d). Average lead tip distance from the AV annulus was 36.6±8.2mm. Mean paced QRSd for the basal, mid, and apical cohorts were 122.5±8.1ms, 118.5±10.7ms, and 120±15.9ms, respectively. Left ventricular activation time in lead V6 numerically decreased for more apical positions, with basal, mid and apical values of 84.4±11.9ms, 73.9±10.6ms, and 69.5±6.0ms, respectively. Lead threshold, impedance, and sensed R waves were stable at time of 2 year follow-up. No analyzed patients underwent lead revision. Multiple lead tip orientations are observed in relation to the IVS during successful LBBAP. More apical lead tip positioning may result in numerically lower LVAT values, despite similar overall QRS duration.

AP-452681-1 NIRVANA: LEFT BUNDLE AREA PACING AND ATRIOVENTRICULAR NODAL ABLATION HAS AN EXCELLENT PROCEDURAL SAFETY PROFILE

Conduction system pacing in the form of Left Bundle Area Pacing (LBAP) has become an accepted form of pacing in patients who will have a high degree of pacing from the right ventricle or/and have a history of heart failure. In patients with persistent or poorly controlled AF, that are not ablation candidates or fail medical therapy, atrioventricular nodal (AVN) ablation with permanent pacemaker is an acceptable alternative. LBAP is a more complex procedure than standard right ventricular pacing. Relatively little data exists, on the safety of using LBAP instead of standard right ventricular pacing (RVP) in patients undergoing AVN ablation. To describe the complication profile of left bundle area pacing in comparison to right ventricular with atrioventricular nodal ablation over a six-month follow up at a large volume center. We identified all patients that underwent LBAP or right ventricular pacing with AVN ablation over the last 2 years and had 6 months of follow-up. Left bundle capture was defined by several accepted criteria (septal 3830 leads on or near the left bundle, pacing left ventricular activation timing (pLVAT) ≤80 msec in V5/V6, left bundle potential, appropriate narrowing of the QRS complex). Only patients with AVN ablation who underwent pacemaker implant at the same time (within 24 hours) were included. Any patients with advanced heart failure with severely reduced ejection fraction that failed left ventricular lead placement was excluded from analysis. 156 patients met the inclusion criteria. As illustrated in Table I, 115 patients were in the LBAP group and 41 where in the right ventricular pacing group. Baseline characteristics were not statistically different. The population was predominantly female, had a preserved ejection fraction (EF) and were patients with paroxysmal atrial fibrillation (38.3% LBAP vs 43.9%). Total complications were not different between the groups (5.2% LBAP vs 0% RVP, p=0.34). Absolute complications in any category in any group were low, Figure 1. All complications were seen in the first 30 days post implant, except for a TIA in the LBAP group, seen at 163 days post procedure. Left bundle area pacing as compared to standard right ventricular pacing with concomitant atrioventricular nodal ablation in patients with atrial fibrillation have a similar safety profile during a six month follow-up.

Catheter ablation of intramural outflow tract premature ventricular complexes: a multicentre study.

Ablation of outflow tract ventricular arrhythmias may be limited by a deep intramural location of the arrhythmogenic source. This study evaluates the acute and long-term outcomes of patients undergoing ablation of intramural outflow tract premature ventricular complexes (PVCs). This multicenter series included patients with structurally normal heart or nonischemic cardiomyopathy and intramural outflow tract PVCs defined by: (a) ≥ 2 of the following criteria: (1) earliest endocardial or epicardial activation < 20ms pre-QRS; (2) Similar activation in different chambers; (3) no/transient PVC suppression with ablation at earliest endocardial/epicardial site; or (b) earliest ventricular activation recorded in a septal coronary vein. Ninety-two patients were included, with a mean PVC burden of 21.5±10.9%. Twenty-six patients had had previous ablations. All PVCs had inferior axis, with LBBB pattern in 68%. In 29 patients (32%) direct mapping of the intramural septum was performed using an insulated wire or multielectrode catheter, and in 13 of these cases the earliest activation was recorded within a septal vein. Most patients required special ablation techniques (one or more), including sequential unipolar ablation in 73%, low-ionic irrigation in 26%, bipolar ablation in 15% and ethanol ablation in 1%. Acute PVC suppression was achieved in 75% of patients. Following the procedure, the PVC burden was reduced to 5.8±8.4%. The mean follow-up was 15±14 months and 16 patients underwent a repeat ablation. Ablation of intramural PVCs is challenging; acute arrhythmia elimination is achieved in 3/4 patients, and non-conventional approaches are often necessary for success.

Comparison of methods for delivering cardiac resynchronization therapy: electrical treatment targets and mechanisms of action

ABSTRACT Introduction Cardiac resynchronization therapy (CRT) has been developed as a treatment for patients with conduction system dysfunction and impairment of ventricular performance. The aim is to restore more physiological cardiac activation and thereby improve cardiac function, symptoms, and outcomes. Areas covered In this review, we discuss potential electrical treatment targets for patients with heart failure and how these electrical treatment targets may determine the optimal pacing approach for delivering CRT. Expert Opinion The most well-established method for delivering CRT is biventricular pacing (BVP). BVP improves symptoms and reduces mortality in patients with left bundle branch block (LBBB). However, patients continue to suffer from heart failure symptoms and decompensations despite receiving BVP. There may be scope to deliver more effective CRT since BVP does not restore physiological ventricular activation. Furthermore, the results with BVP in patients with non-LBBB conduction system disease have been generally disappointing. Alternative pacing approaches to BVP are now available, including conduction system pacing and left ventricular endocardial pacing. These newer pacing approaches offer exciting potential to not only offer an alternative to coronary sinus lead implantation in the case of implant failure but to potentially deliver more effective treatment in LBBB and maybe even extend the indications for CRT beyond LBBB.

An explainable artificial intelligence-enabled electrocardiogram analysis model for the classification of reduced left ventricular function.

The black box nature of artificial intelligence (AI) hinders the development of interpretable AI models that are applicable in clinical practice. We aimed to develop an AI model for classifying patients of reduced left ventricular ejection fraction (LVEF) from 12-lead electrocardiograms (ECG) with the decision-interpretability. We acquired paired ECG and echocardiography datasets from the central and co-operative institutions. For the central institution dataset, a random forest model was trained to identify patients with reduced LVEF among 29 907 ECGs. Shapley additive explanations were applied to 7196 ECGs. To extract the model's decision criteria, the calculated Shapley additive explanations values were clustered for 192 non-paced rhythm patients in which reduced LVEF was predicted. Although the extracted criteria were different for each cluster, these criteria generally comprised a combination of six ECG findings: negative T-wave inversion in I/V5-6 leads, low voltage in I/II/V4-6 leads, Q wave in V3-6 leads, ventricular activation time prolongation in I/V5-6 leads, S-wave prolongation in V2-3 leads, and corrected QT interval prolongation. Similarly, for the co-operative institution dataset, the extracted criteria comprised a combination of the same six ECG findings. Furthermore, the accuracy of seven cardiologists' ECG readings improved significantly after watching a video explaining the interpretation of these criteria (before, 62.9% ± 3.9% vs. after, 73.9% ± 2.4%; P = 0.02). We visually interpreted the model's decision criteria to evaluate its validity, thereby developing a model that provided the decision-interpretability required for clinical application.

Ventricular Conduction Stability Noninvasively Identifies an Arrhythmic Substrate in Survivors of Idiopathic Ventricular Fibrillation.

Background Idiopathic ventricular fibrillation (VF) is a diagnosis of exclusion following normal cardiac investigations. We sought to determine if exercise-induced changes in electrical substrate could distinguish patient groups with various ventricular arrhythmic pathophysiological conditions and identify patients susceptible to VF. Methods and Results Computed tomography and exercise testing in patients wearing a 252-electrode vest were combined to determine ventricular conduction stability between rest and peak exercise, as previously described. Using ventricular conduction stability, conduction heterogeneity in idiopathic VF survivors (n=14) was compared with those surviving VF during acute ischemia with preserved ventricular function following full revascularization (n=10), patients with benign ventricular ectopy (n=11), and patients with normal hearts, no arrhythmic history, and negative Ajmaline challenge during Brugada family screening (Brugada syndrome relatives; n=11). Activation patterns in normal subjects (Brugada syndrome relatives) are preserved following exercise, with mean ventricular conduction stability of 99.2±0.9%. Increased heterogeneity of activation occurred in the idiopathic VF survivors (ventricular conduction stability: 96.9±2.3%) compared with the other groups combined (versus 98.8±1.6%; P=0.001). All groups demonstrated periodic variation in activation heterogeneity (frequency, 0.3-1 Hz), but magnitude was greater in idiopathic VF survivors than Brugada syndrome relatives or patients with ventricular ectopy (7.6±4.1%, 2.9±2.9%, and 2.8±1.2%, respectively). The cause of this periodicity is unknown and was not replicable by introducing exercise-induced noise at comparable frequencies. Conclusions In normal subjects, ventricular activation patterns change little with exercise. In contrast, patients with susceptibility to VF experience activation heterogeneity following exercise that requires further investigation as a testable manifestation of underlying myocardial abnormalities otherwise silent during routine testing.

Attenuation of stretch-induced arrhythmias following chemical ablation of Purkinje fibres, in isolated rabbit hearts.

Purkinje fibres (PFs) play an important role in some ventricular arrhythmias and acute ventricular stretch can evoke mechanically-induced arrhythmias. We tested whether Purkinje fibres, play a role in these arrhythmias. Pseudo-ECGs were recorded in isolated, Langendorff-perfused, rabbit hearts in which the left ventricular endocardial surface was also irrigated with Tyrode, via an indwelling catheter placed in the left ventricular lumen. The number and period of ectopic activations was measured during left ventricular lumen inflation via an indwelling fluid-filled balloon (500μL added over 2s and maintained for 15s in total). Mechanically-induced arrhythmias occurred in 70% of balloon inflations: they were maximal in the first 5s and ceased within 15s. Brief, (10s) irrigation of the left ventricular lumen with Lugol solution (IK/I2), via the indwelling catheter, reduced inflation-induced ectopics by 98% (p < 0.05). Ablation of endocardial PFs by Lugol was confirmed by Triphenyltetrazolium Chloride staining. Optical mapping revealed the left ventricular epicardial activation patterns of ectopics could have PF-mediated and focal sources. In silico modelling predicted ectopic sources originating in the endocardial region propagate to and through the Purkinje fibres network. Acute distention-induced ectopics are multi-focal, their attenuation by Lugol, their activation patterns and in silico modelling indicate a participation of Purkinje fibres in these arrhythmias.

High predictive value of paced QRS frequency in verification of left bundle branch pacing.

Left bundle branch area pacing (LBBAP) is a newer technique to deliver more synchronous left ventricular activation. Several criteria have been proposed, but not fully validated, to confirm LBBAP during implantation of the pacing lead. Spectral analysis has been used to characterize the frequency components of the clinical QRS utilizing the Fourier transform algorithm. We hypothesized that higher frequency content of the paced QRS complex may show predictive value of successful LBBAP. We evaluated 84 patients with ejection fraction > 50%, who underwent LBB lead placement (n = 42) using ≥ 1 current criteria and right ventricular midseptal (RVsp) lead placement (n = 42) from 2000 to 2022. Time frequency analysis (Matlab) was used to determine the frequency content of the paced QRS complex. The centroid frequency (CF), which is the weighted average QRS frequency, was calculated. Patients in RVsp group had a longer paced QRS duration (155.6 ± 28.0 vs 127.1 ± 17.2, p < 0.002) compared to the LBBAP group. Of all standard ECG leads, the paced QRS in V2 gave the greatest difference of the CF of the LBBAP group at 8.8 ± 1.6 Hz versus 5.7 ± 0.7 Hz of the RVsp group. This difference was significant by both univariate (p < 0.003) and multivariate (p < 0.010) analysis. Predictive value of the CF for successful LBB pacing in lead V2 was highest with an AUC of 0.98. The sensitivity and specificity were 88.1% and 97.6%, respectively. Spectral analysis predicts successful LBBAP with higher frequency content when compared to RVsp pacing. Given the limitations to the current criteria to confirm LBBAP, intraprocedural use of frequency content analysis of the paced QRS complex in patients may prove useful at verifying LBB capture if verified by prospective clinical trials.

The Protective Effect of 11-Keto-β-Boswellic Acid against Diabetic Cardiomyopathy in Rats Entails Activation of AMPK

This study examined the protective effect of 11-keto-β-boswellic acid (AKBA) against streptozotocin (STZ)-induced diabetic cardiomyopathy (DC) in rats and examined the possible mechanisms of action. Male rats were divided into 5 groups (n = 8/each): (1) control, AKBA (10 mg/kg, orally), STZ (65 mg/kg, i.p.), STZ + AKBA (10 mg/kg, orally), and STZ + AKBA + compound C (CC/an AMPK inhibitor, 0.2 mg/kg, i.p.). AKBA improved the structure and the systolic and diastolic functions of the left ventricles (LVs) of STZ rats. It also attenuated the increase in plasma glucose, plasma insulin, and serum and hepatic levels of triglycerides (TGs), cholesterol (CHOL), and free fatty acids (FFAs) in these diabetic rats. AKBA stimulated the ventricular activities of phosphofructokinase (PFK), pyruvate dehydrogenase (PDH), and acetyl CoA carboxylase (ACC); increased levels of malonyl CoA; and reduced levels of carnitine palmitoyltransferase I (CPT1), indicating improvement in glucose and FA oxidation. It also reduced levels of malondialdehyde (MDA); increased mitochondria efficiency and ATP production; stimulated mRNA, total, and nuclear levels of Nrf2; increased levels of glutathione (GSH), heme oxygenase (HO-1), superoxide dismutase (SOD), and catalase (CAT); but reduced the expression and nuclear translocation of NF-κB and levels of tumor-necrosis factor-α (TNF-α) and interleukin-6 (IL-6). These effects were concomitant with increased activities of AMPK in the LVs of the control and STZ-diabetic rats. Treatment with CC abolished all these protective effects of AKBA. In conclusion, AKBA protects against DC in rats, mainly by activating the AMPK-dependent control of insulin release, cardiac metabolism, and antioxidant and anti-inflammatory effects.

Estimation of left ventricular activation sequence in patients with heart failure using two-dimensional speckle tracking echocardiography

Evaluation of longitudinal strain (LS) from two-dimensional echocardiography is useful for global and regional left ventricular (LV) dysfunction assessment. We determined whether the LS reflects contraction process in patients with asynchronous LV activation. We studied 144 patients with an ejection fraction ≤ 35%, who had left bundle branch block (LBBB, n = 42), right ventricular apical (RVA) pacing (n = 34), LV basal- or mid-lateral pacing (n = 23), and no conduction block (Narrow-QRS, n = 45). LS distribution maps were constructed using 3 standard apical views. The times from the QRS onset-to-early systolic positive peak (Q-EPpeak) and late systolic negative peak (Q-LNpeak) were measured to determine the beginning and end of contractions in each segment. Negative strain in LBBB initially appeared in the septum and basal-lateral contracted late. In RVA and LV pacing, the contracted area enlarged centrifugally from the pacing site. Narrow-QRS showed few regional differences in strain during the systolic period. The Q-EPpeak and Q-LNpeak exhibited similar sequences characterized by septum to basal-lateral via the apical regions in LBBB, apical to basal regions in RVA pacing, and lateral to a relatively large delayed contracted area between the apical- and basal-septum in LV pacing. Differences in Q-LNpeaks between the apical and basal segments in delayed contracted wall were 107 ± 30 ms in LBBB, 133 ± 46 ms in RVA pacing, and 37 ± 20 ms in LV pacing (p < 0.05, between QRS groups). Specific LV contraction processes were demonstrated by evaluating the LS distribution and time-to-peak strain. These evaluations may have potential to estimate the activation sequence in patients with asynchronous LV activation.

Left bundle branch area pacing: How to prevent a coronary venous fistula.

Left bundle branch area pacing: How to prevent a coronary venous fistula.

Bipolar anodal septal pacing with direct LBB capture preserves physiological ventricular activation better than unipolar left bundle branch pacing.

Left bundle branch pacing (LBBP) produces delayed, unphysiological activation of the right ventricle. Using ultra-high-frequency electrocardiography (UHF-ECG), we explored how bipolar anodal septal pacing with direct LBB capture (aLBBP) affects the resultant ventricular depolarization pattern. In patients with bradycardia, His bundle pacing (HBP), unipolar nonselective LBBP (nsLBBP), aLBBP, and right ventricular septal pacing (RVSP) were performed. Timing of local ventricular activation, in leads V1-V8, was displayed using UHF-ECG, and electrical dyssynchrony (e-DYS) was calculated as the difference between the first and last activation. Durations of local depolarizations were determined as the width of the UHF-QRS complex at 50% of its amplitude. aLBBP was feasible in 63 of 75 consecutive patients with successful nsLBBP. aLBBP significantly improved ventricular dyssynchrony (mean -9 ms; 95% CI (-12;-6) vs. -24 ms (-27;-21), ), p < 0.001) and shortened local depolarization durations in V1-V4 (mean differences -7 ms to -5 ms (-11;-1), p < 0.05) compared to nsLBBP. aLBBP resulted in e-DYS -9 ms (-12; -6) vs. e-DYS 10 ms (7;14), p < 0.001 during HBP. Local depolarization durations in V1-V2 during aLBBP were longer than HBP (differences 5-9 ms (1;14), p < 0.05, with local depolarization duration in V1 during aLBBP being the same as during RVSP (difference 2 ms (-2;6), p = 0.52). Although aLBBP improved ventricular synchrony and depolarization duration of the septum and RV compared to unipolar nsLBBP, the resultant ventricular depolarization was still less physiological than during HBP.

Evidence for concealed fasciculo-ventricular connections as revealed by His bundle pacing.

It is almost 100 years ago since Mahaim described the so-called paraspecific connections between the ventricular conduction axis and the crest of the muscular ventricular septum, believing such pathways to be ubiquitous. These pathways, however, have yet to be considered as potential pathways for septal activation during His bundle pacing. So as to explore the hypothesis that specialised septal pathways might provide the substrate for septal activation during His bundle pacing, we compared the findings from 22 serially sectioned histological datasets and 34 different individuals undergoing His bundle pacing. We found histologically specialised pathways connecting the branching component of the atrioventricular conduction axis with the crest of the muscular ventricular septum in almost four-fifths of the histological datasets. In 32 of 34 patients undergoing His bundle pacing, the QRS complex closely resembled published images of known conduction through fasciculo-ventricular pathways. In only two patients was a delta wave not seen at any pacing voltages. Capture of these connections varied according to pacing voltage, a finding which correlated with the distance of the pathways from the site of penetration of the ventricular conduction axis. Ventricular activation times remained normal in the presence of the delta wave at higher pacing voltage but were prolonged at lower voltages. Our histologic findings confirm fasciculo-ventricular connections, initially described by Mahaim as being paraspecific, are likely ubiquitous. Analysis of 12-lead electrocardiograms leads us to conclude that fasciculo-ventricular pathways, concealed during sinus rhythm, become manifest with His bundle pacing.

Reappraisal and New Observations on Idiopathic Ventricular Arrhythmias Ablated From the Noncoronary Aortic Sinus

BackgroundThe electrophysiological characteristics of idiopathic ventricular arrhythmias (VAs) from the noncoronary sinus (NCS) have not been fully described. ObjectivesThis study sought to investigate electrophysiological characteristics and catheter ablation in patients with idiopathic NCS-VA. MethodsThis study comprised 11 patients undergoing radiofrequency (RF) catheter ablation for idiopathic NCS-VA. Angiography was performed to confirm the origin in the aortic sinus before RF ablation. ResultsClinical arrhythmias presented left bundle block/inferior axis morphology in all patients. QRS morphology of R’ and R/s’ pattern was dominantly found in lead III. Mapping in the right ventricle demonstrated the earliest ventricular activation (EVA) site at the His Bundle region, whereas mapping in the NCS demonstrated that the EVA preceded the activation at the His Bundle region by 12.1 ± 7.9 milliseconds. All VAs were successfully ablated in <2.5 seconds within the NCS with 1 RF application. The successful ablation site was at the nadir of NCS in 10 patients, and near the junction of NCS and the right coronary sinus in the remaining one. A discrete potential can be observed at the EVA site within the NCS in 10 patients (91%); however, an excellent pace mapping at the EVA site was obtained in only 2 patients. Junctional beats did not occur during RF application in all 11 patients. There were no complications or clinical recurrence during a mean follow-up of 26.0 ± 9.8 months. ConclusionsNCS-VA presents a peculiar electrocardiogram. A discrete potential can be mapped within the NCS during VA and sinus rhythm, and can be used in guiding ablation.

Deep learning-based image segmentation model using an MRI-based convolutional neural network for physiological evaluation of the heart.

Background and Objective: Cardiovascular disease is a high-fatality health issue. Accurate measurement of cardiovascular function depends on precise segmentation of physiological structure and accurate evaluation of functional parameters. Structural segmentation of heart images and calculation of the volume of different ventricular activity cycles form the basis for quantitative analysis of physiological function and can provide the necessary support for clinical physiological diagnosis, as well as the analysis of various cardiac diseases. Therefore, it is important to develop an efficient heart segmentation algorithm. Methods: A total of 275 nuclear magnetic resonance imaging (MRI) heart scans were collected, analyzed, and preprocessed from Huaqiao University Affiliated Strait Hospital, and the data were used in our improved deep learning model, which was designed based on the U-net network. The training set included 80% of the images, and the remaining 20% was the test set. Based on five time phases from end-diastole (ED) to end-systole (ES), the segmentation findings showed that it is possible to achieve improved segmentation accuracy and computational complexity by segmenting the left ventricle (LV), right ventricle (RV), and myocardium (myo). Results: We improved the Dice index of the LV to 0.965 and 0.921, and the Hausdorff index decreased to 5.4 and 6.9 in the ED and ES phases, respectively; RV Dice increased to 0.938 and 0.860, and the Hausdorff index decreased to 11.7 and 12.6 in the ED and ES, respectively; myo Dice increased to 0.889 and 0.901, and the Hausdorff index decreased to 8.3 and 9.2 in the ED and ES, respectively. Conclusion: The model obtained in the final experiment provided more accurate segmentation of the left and right ventricles, as well as the myocardium, from cardiac MRI. The data from this model facilitate the prediction of cardiovascular disease in real-time, thereby providing potential clinical utility.

12-lead ECG signal processing and atrial fibrillation prediction in clinical practice.

Because clinically used 12-lead electrocardiography (ECG) devices have high falsepositive errors in automatic interpretations of atrial fibrillation (AF), they require substantial improvements before use. A clinical 12-lead ECG pre-processing method with a parallel convolutional neural network (CNN) model for 12-lead ECG automatic AF recognition is introduced. Raw AF diagnosis data from a 12-lead ECG device were collected and analyzed by two cardiologists to differentiate between true- and false-positives. Using a stationary wavelet transform (SWT) and independent component analysis (ICA) noise reduction was conducted and baseline wandering was corrected for the raw signals. AF patterns were learned and predicted using a parallel CNN deep learning (DL) model. (1) The proposed method alleviates the decreased ECG QRS amplitude enhances the signal-to-noise ratio and clearly shows atrial and ventricular activities. (2) After training, the CNNbased AF detector significantly reduced false-positive errors. The precision of AF diagnosis increased from 77.3% to 94.0 ± 1.5% as compared to ECG device interpretation. For AF screening, the model showed an average sensitivity of 96.8 ± 2.2%, specificity of 79.0 ± 5.8%, precision of 94.0 ± 1.5%, F1-measure of 95.2 ± 1.0%, and overall accuracy of 92.7 ± 1.5%. The method can bridge the gap between the research and clinical practice The ECG signal pre-processing and DL-based AF interpretation can be rapidly implemented clinically.