Detailed analysis of electrogram peak frequency to guide ventricular tachycardia substrate mapping.

AIMS: Differentiating near-field (NF) and far-field (FF) electrograms (EGMs) is crucial in identifying critical arrhythmogenic substrate during ventricular tachycardia (VT) ablation. A novel algorithm annotates NF-fractionated signals enabling EGM peak frequency (PF) determination using wavelet transformation. This study evaluated the algorithms' effectiveness in identifying critical components of the VT circuit during substrate mapping. METHODS AND RESULTS: A multicentre, international cohort undergoing VT ablation was investigated. VT activation maps were used to demarcate the isthmus zone (IZ). Offline analysis was performed to evaluate the diagnostic performance of low-voltage area (LVA) PF substrate mapping. A total of 30 patients encompassing 198 935 EGMs were included. The IZ PF was significantly higher in sinus rhythm (SR) compared to right ventricular paced (RVp) substrate maps (234 Hz (195-294) vs. 197 Hz (166-220); P = 0.010). Compared to LVA PF, the IZ PF was significantly higher in both SR and RVp substrate maps (area under curve, AUC: 0.74 and 0.70, respectively). The LVA PF threshold of ≥200 Hz was optimal in SR maps (sensitivity 69%; specificity 64%) and RVp maps (sensitivity 60%; specificity 64%) in identifying the VT isthmus. In amiodarone-treated patients (n = 20), the SR substrate map IZ PF was significantly lower (222 Hz (186-257) vs. 303 Hz (244-375), P = 0.009) compared to amiodarone-naïve patients (n = 10). The ≥200 Hz LVA PF threshold resulted in an 80% freedom from VT with a trend towards reduced ablation lesions and radiofrequency times. CONCLUSION: LVA PF substrate mapping identifies critical components of the VT circuit with an optimal threshold of ≥200 Hz. Isthmus PF is influenced by chronic amiodarone therapy with lower values observed during RV pacing.

Same-day discharge after atrial fibrillation ablation under a nurse-coordinated standardized protocol.

AIMS: Same-day discharge (SDD) after atrial fibrillation (AF) ablation is an effective means to spare healthcare resources. However, safety remains a concern, and besides structural adaptations, SDD requires more efficient logistics and coordination. Therefore, in this study, we implement a streamlined, nurse-coordinated SDD programme following a standardized protocol. METHODS AND RESULTS: As a dedicated SDD coordinator, a nurse specialized in ambulatory cardiac interventions was in charge of the full SDD protocol, including eligibility, patient flow, in-hospital logistics, patient education, and discharge as well as early post-discharge follow-up by smartphone-based virtual visits. Patients planned for AF ablation were considered eligible if they had a left ventricular ejection fraction (LVEF) ≥35%, with basic support at home and accessibility of the hospital within 60 min also forming a part of the eligibility criteria. A total of 420 consecutive patients were screened by the SDD coordinator, of whom 331 were eligible for SDD. The reasons for exclusion were living remotely (29, 6.9%), lack of support at home (19, 4.5%), or LVEF <35% (17, 4.0%). Of the eligible patients, 300 (91%) were successfully discharged the same day. There were no major post-SDD complications. Rates of unplanned medical attention (19, 6.3%) and 30-day readmission (5, 1.6%) were extremely low and driven by femoral access-site complications. These were significantly reduced upon the introduction of compulsory ultrasound-guided punctures after the initial 150 SDD patients (P = 0.0145). Standardized SDD coordination resulted in efficient workflows and reduced the total workload of the medical staff. CONCLUSION: Same-day discharge after AF ablation following a nurse-coordinated standardized protocol is safe and efficient. The concept of ambulatory cardiac intervention nurses functioning as dedicated coordinators may be key in the future transition of hospitals to SDD. Ultrasound-guided femoral puncture virtually eliminated relevant femoral access-site complications in our cohort and should therefore be a prerequisite for SDD.

2024 updated European Heart Rhythm Association core curriculum for physicians and allied professionals: a statement of the European Heart Rhythm Association of the European Society of Cardiology.

Heart rhythm management is a continuously evolving sub-speciality of cardiology. Every year, many physicians and allied professionals (APs) start and complete their training in cardiac implantable electronic devices (CIEDs) or electrophysiology (EP) across the European Heart Rhythm Association (EHRA) member countries. While this training ideally ends with an EHRA certification, the description of the learning pathway (what, how, when, and where) through an EHRA core curriculum is also a prerequisite for a successful training. The first EHRA core curriculum for physicians was published in 2009. Due to the huge developments in the field of EP and device therapy, this document needed updating. In addition, a certification process for APs has been introduced, as well as a recertification process and accreditation of EHRA recognized training centres. Learning pathways are more individualized now, with Objective Structured Assessment of Technical Skills (OSATS) to monitor learning progression of trainees. The 2024 updated EHRA core curriculum for physicians and APs describes, for both CIED and EP, the syllabus, OSATS, training programme and certification, and recertification for physicians and APs and stresses the importance of continued medical education after certification. In addition, requirements for accreditation of training centres and trainers are given. Finally, suggested reading lists for CIED and EP are attached as online supplements.

Non-invasive detection of slow conduction with cardiac magnetic resonance imaging for ventricular tachycardia ablation.

AIMS: Non-invasive myocardial scar characterization with cardiac magnetic resonance (CMR) has been shown to accurately identify conduction channels and can be an important aid for ventricular tachycardia (VT) ablation. A new mapping method based on targeting deceleration zones (DZs) has become one of the most commonly used strategies for VT ablation procedures. The aim of the study was to analyse the capability of CMR to identify DZs and to find predictors of arrhythmogenicity in CMR channels. METHODS AND RESULTS: Forty-four consecutive patients with structural heart disease and VT undergoing ablation after CMR at a single centre (October 2018 to July 2021) were included (mean age, 64.8 ± 11.6 years; 95.5% male; 70.5% with ischaemic heart disease; a mean ejection fraction of 32.3 ± 7.8%). The characteristics of CMR channels were analysed, and correlations with DZs detected during isochronal late activation mapping in both baseline maps and remaps were determined. Overall, 109 automatically detected CMR channels were analysed (2.48 ± 1.15 per patient; length, 57.91 ± 63.07 mm; conducting channel mass, 2.06 ± 2.67 g; protectedness, 21.44 ± 25.39 mm). Overall, 76.1% of CMR channels were associated with a DZ. A univariate analysis showed that channels associated with DZs were longer [67.81 ± 68.45 vs. 26.31 ± 21.25 mm, odds ratio (OR) 1.03, P = 0.010], with a higher border zone (BZ) mass (2.41 ± 2.91 vs. 0.87 ± 0.86 g, OR 2.46, P = 0.011) and greater protectedness (24.97 ± 27.72 vs. 10.19 ± 9.52 mm, OR 1.08, P = 0.021). CONCLUSION: Non-invasive detection of targets for VT ablation is possible with CMR. Deceleration zones found during electroanatomical mapping accurately correlate with CMR channels, especially those with increased length, BZ mass, and protectedness.

Novel systematic processing of cardiac magnetic resonance imaging identifies target regions associated with infarct-related ventricular tachycardia.

AIMS: There is lack of agreement on late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) imaging processing for guiding ventricular tachycardia (VT) ablation. We aim at developing and validating a systematic processing approach on LGE-CMR images to identify VT corridors that contain critical VT isthmus sites. METHODS AND RESULTS: This is a translational study including 18 pigs with established myocardial infarction and inducible VT undergoing in vivo characterization of the anatomical and functional myocardial substrate associated with VT maintenance. Clinical validation was conducted in a multicentre series of 33 patients with ischaemic cardiomyopathy undergoing VT ablation. Three-dimensional LGE-CMR images were processed using systematic scanning of 15 signal intensity (SI) cut-off ranges to obtain surface visualization of all potential VT corridors. Analysis and comparisons of imaging and electrophysiological data were performed in individuals with full electrophysiological characterization of the isthmus sites of at least one VT morphology. In both the experimental pig model and patients undergoing VT ablation, all the electrophysiologically defined isthmus sites (n = 11 and n = 19, respectively) showed overlapping regions with CMR-based potential VT corridors. Such imaging-based VT corridors were less specific than electrophysiologically guided ablation lesions at critical isthmus sites. However, an optimized strategy using the 7 most relevant SI cut-off ranges among patients showed an increase in specificity compared to using 15 SI cut-off ranges (70 vs. 62%, respectively), without diminishing the capability to detect VT isthmus sites (sensitivity 100%). CONCLUSION: Systematic imaging processing of LGE-CMR sequences using several SI cut-off ranges may improve and standardize procedure planning to identify VT isthmus sites.

Myocardial scarring and recurrence of ventricular arrhythmia in patients surviving an out-of-hospital cardiac arrest.

INTRODUCTION: Prediction of recurrent ventricular arrhythmia (VA) in survivors of an out-of-hospital cardiac arrest (OHCA) is important, but currently difficult. Risk of recurrence may be related to presence of myocardial scarring assessed with late gadolinium enhancement cardiac magnetic resonance (LGE-CMR). Our study aims to characterize myocardial scarring as defined by LGE-CMR in survivors of a VA-OHCA and investigate its potential role in the risk of new VA events. METHODS: Between 2015 and 2022, a total of 230 VA-OHCA patients without ST-segment elevation myocardial infarction had CMR before implantable cardioverter-defibrillator implantation for secondary prevention at Copenhagen University Hospital, Rigshospitalet, and Hospital Clínic, University of Barcelona, of which n = 170 patients had a conventional (no LGE protocol) CMR and n = 60 patients had LGE-CMR (including LGE protocol). Scar tissue including core, border zone (BZ) and BZ channels were automatically detected by specialized investigational software in patients with LGE-CMR. The primary endpoint was recurrent VA. RESULTS: After exclusion, n = 52 VA-OHCA patients with LGE-CMR and a mean left ventricular ejection fraction of 49 ± 16% were included, of which 18 (32%) patients reached the primary endpoint of VA. Patients with recurrent VA in exhibited greater scar mass, core mass, BZ mass, and presence of BZ channels compared with patients without recurrent VA. The presence of BZ channels identified patients with recurrent VA with 67% sensitivity and 85% specificity (area under the ROC curve (AUC) 0.76; 95% CI: 0.63-0.89; p < .001) and was the strongest predictor of the primary endpoint. CONCLUSIONS: The presence of BZ channels was the strongest predictor of recurrent VA in patients with an out of-hospital cardiac arrest and LGE-CMR.

Magnetic resonance detection of advanced atrial cardiomyopathy increases the risk for atypical atrial flutter occurrence following atrial fibrillation ablation.

AIMS: Recurrence of arrhythmia after catheter ablation of atrial fibrillation (AF) in the form of atypical atrial flutter (AFL) is common among a significant number of patients and often requires redo ablation with limited success rates. Identifying patients at high risk of AFL after AF ablation could aid in patient selection and personalized ablation approach. The study aims to assess the relationship between pre-existing atrial cardiomyopathy and the occurrence of AFL following AF ablation. METHODS AND RESULTS: We analysed a cohort of 1007 consecutive AF patients who underwent catheter ablation and were included in a prospective registry. Patients who did not have baseline cardiac magnetic resonance imaging and late gadolinium enhancement (LGE-CMR) or did not experience any recurrences were excluded. A total of 166 patients were included gathering 56 patients who underwent re-ablation due to AFL recurrences and 110 patients who underwent re-ablation due to AF recurrences (P = 0.11). A multiparametric assessment of atrial cardiomyopathy was based on basal LGE-CMR, including left atrial (LA) volume, LA sphericity, and global and segmental LA fibrosis using semiautomated post-processing software. Out of the initial cohort of 1007 patients, AFL and AF occurred in 56 and 110 patients, respectively. An age higher than 65 [odds ratio (OR) = 5.6, 95% confidence interval (CI): 2.2-14.4], the number of previous ablations (OR = 3.0, 95% CI: 1.2-7.8), and the management of ablation lines in the index procedure (OR = 2.5, 95% CI: 1.0-6.3) were independently associated with AFL occurrence. Furthermore, several characteristics assessed by LGE-CMR were identified as independent predictors of AFL recurrence after the index ablation for AF, such as enhanced LA sphericity (OR = 1.3, 95% CI: 1.1-1.6), LA global fibrosis (OR = 1.03, 95% CI: 1.01-1.07), and increased fibrosis in the lateral wall (OR = 1.03, 95% CI: 1.01-1.04). CONCLUSION: Advanced atrial cardiomyopathy assessed by LGE-CMR, such as increased LA sphericity, global LA fibrosis, and fibrosis in the lateral wall, is independently associated with arrhythmia recurrence in the form of AFL following AF ablation.

Stepwise application of ECG and electrogram-based criteria to ensure electrical resynchronization with left bundle branch pacing.

AIMS: To define a stepwise application of left bundle branch pacing (LBBP) criteria that will simplify implantation and guarantee electrical resynchronization. Left bundle branch pacing has emerged as an alternative to biventricular pacing. However, a systematic stepwise criterion to ensure electrical resynchronization is lacking. METHODS AND RESULTS: A cohort of 24 patients from the LEVEL-AT trial (NCT04054895) who received LBBP and had electrocardiographic imaging (ECGI) at 45 days post-implant were included. The usefulness of ECG- and electrogram-based criteria to predict accurate electrical resynchronization with LBBP were analyzed. A two-step approach was developed. The gold standard used to confirm resynchronization was the change in ventricular activation pattern and shortening in left ventricular activation time, assessed by ECGI. Twenty-two (91.6%) patients showed electrical resynchronization on ECGI. All patients fulfilled pre-screwing requisites: lead in septal position in left-oblique projection and W paced morphology in V1. In the first step, presence of either right bundle branch conduction delay pattern (qR or rSR in V1) or left bundle branch capture Plus (QRS ≤120 ms) resulted in 95% sensitivity and 100% specificity to predict LBBP resynchronization, with an accuracy of 95.8%. In the second step, the presence of selective capture (100% specificity, only 41% sensitivity) or a spike-R <80 ms in non-selective capture (100% specificity, sensitivity 46%) ensured 100% accuracy to predict resynchronization with LBBP. CONCLUSION: Stepwise application of ECG and electrogram criteria may provide an accurate assessment of electrical resynchronization with LBBP (Graphical abstract).

Non-invasive assessment of pulmonary vein isolation durability using late gadolinium enhancement magnetic resonance imaging.

AIMS: Electrical reconnection of pulmonary veins (PVs) is considered an important determinant of recurrent atrial fibrillation (AF) after pulmonary vein isolation (PVI). To date, AF recurrences almost automatically trigger invasive repeat procedures, required to assess PVI durability. With recent technical advances, it is becoming increasingly common to find all PVs isolated in those repeat procedures. Thus, as ablation of extra-PV targets has failed to show benefit in randomized trials, more and more often these highly invasive procedures are performed only to rule out PV reconnection. Here we aim to define the ability of late gadolinium enhancement (LGE)-magnetic resonance imaging (MRI) to rule out PV reconnection non-invasively. METHODS AND RESULTS: This study is based on a prospective registry in which all patients receive an LGE-MRI after AF ablation. Included were all patients that-after an initial PVI and post-ablation LGE-MRI-underwent an invasive repeat procedure, which served as a reference to determine the predictive value of non-invasive lesion assessment by LGE-MRI.: 152 patients and 304 PV pairs were analysed. LGE-MRI predicted electrical PV reconnection with high sensitivity (98.9%) but rather low specificity (55.6%). Of note, LGE lesions without discontinuation ruled out reconnection of the respective PV pair with a negative predictive value of 96.9%, and patients with complete LGE lesion sets encircling all PVs were highly unlikely to show any PV reconnection (negative predictive value: 94.4%). CONCLUSION: LGE-MRI has the potential to guide selection of appropriate candidates and planning of the ablation strategy for repeat procedures and may help to identify patients that will not benefit from a redo-procedure if no ablation of extra-PV targets is intended.

Decrement Evoked Potential (DEEP) Mapping of the Atria: Unmasking Atrial Fibrillation Substrate.

BACKGROUND: Atrial myopathy may underlie the progression of atrial fibrillation (AF) from a treatable disease to an irreversible condition with poor ablation outcomes. Electrophysiological methods to unmask areas prone to re-entry initiation could be key to defining latent atrial myopathy. METHODS: Consecutive patients referred for AF ablation were prospectively included at four institutions. Decrement evoked potential mapping (DEEP) was performed in eight left atrial sites and five right atrial sites, from two different pacing locations (endocardially from the left atrial appendage, epicardially from the proximal coronary sinus). The electrograms (EGMs) during S1 600 ms drive and after an extra stimulus (S2 at +30 ms above atrial refractoriness) were studied at each location and assessed for decremental properties. Follow-up was 12 months. RESULTS: Seventy-four patients were included and 85% had persistent AF. A total of 17,614 EGMs were individually analysed and measured. Nine percent of the EGMs showed DEEP properties (local delay of >10 ms after S2) with a mean decrement of 33±26 ms. DEEPs were more frequent in the left atrium than the right atrium (9.4% vs 8.0%; p<0.001) and more prevalent in persistent AF patients than paroxysmal AF patients (9.8% vs 4.6% p=0.001). Atrial DEEPs were more frequently unmasked in normal bipolar voltage areas and by epicardial pacing than endocardial pacing (9.6% vs 8.4%, respectively; p=0.004). Within the left atrium, the roof had the highest prevalence of DEEP EGMs. CONCLUSIONS: DEEP mapping of both atria is useful for highlighting areas with a tendency for unidirectional block and re-entry initiation. Those areas are more easily unmasked by epicardial pacing from the coronary sinus and more prevalent in persistent AF patients than in paroxysmal AF patients.

Exit sites on the epicardium rarely subtend critical diastolic path of ischemic VT on the endocardium: Implications for noninvasive ablation.

BACKGROUND: Noninvasive electrocardiographic mapping of ventricular tachycardia (VT) and ablation using stereotactic radiotherapy was recently reported. This strategy does not directly evaluate the critical diastolic components and assumes that the epicardial exit site of VT subtends closely over the endocardial mid-diastolic isthmus. OBJECTIVE: To determine if the epicardial exit site of VT spatially corresponds to the critical diastolic components of ischemic scar-related VT. MATERIALS AND METHODS: Intraoperative simultaneous endocardial and epicardial mapping were performed during VT using a 112-bipole endocardial balloon and 112-bipole epicardial sock array. In eight patients, nine VTs having entire diastolic circuit mapped were included in the study. The diastolic path and VT-exit sites (epicardial and endocardial) were determined. RESULTS: The diastolic path was mapped in the endocardium for all nine VTs (median length, 50; interquartile range [IQR], 28 mm). The tachycardia cycle length ranged from 210-500 ms. The VT-exit site was early in the endocardium for six VTs and on the epicardium for three VTs. The mid-diastolic isthmus and endocardial exit site of the six endocardial VTs were spatially distant from their epicardial exit site by a median distance of 32 and 27 mm, respectively. For the three VTs with an early epicardial exit, the isthmus and endocardial exit sites were distant from the epicardial exit site by a median distance of 34 and 38 mm, respectively. CONCLUSION: The epicardial exit site and the mid-diastolic isthmus sites were spatially distant and discrepant. Surface electrocardiography (ECG)-derived strategy in identifying epicardial exit site to select noninvasive ablation targets is prone to identify epicardial exit sites and may not identify critical targets in ischemic scar VT.

Reduction of Left Ventricular Dilation Beyond the First Year After Anterior Myocardial Infarction.

BACKGROUND: Reduction of left ventricular (LV) dilation (RD) beyond the first year after ST-segment-elevation myocardial infarction (STEMI) is unknown. We investigated its potential occurrence in comparison with stationary (SD) and progressive (PD) dilation. METHODS AND RESULTS: Perfusion gated SPECT features at 1 and 3 years were evaluated in 168 3-year survivors of a first anterior STEMI. Comparisons were made among patients with RD (≥15% reduction of LV end-systolic volume [LVESV]), SD (<15% reduction or increase), and PD (≥15% increase). There were 35 patients with RD (21%), 84 with SD (50%), and 49 with PD (29%). At 1 year, ejection fraction, wall motion and perfusion scores, and LV volumes were similar. In RD patients, the fall in LVESV, nearly 22%, was apparent in those with frank (>51 mL; P < .001) or little/moderate LV dilation at 1 year (LVESV ≤51 mL; P = .002) and was associated with increased ejection fraction (P values .008 and .009, respectively). In the 3 groups, however, LVESV changes were unrelated to 1-year LV volumes, ejection fraction, or contractility score. CONCLUSIONS: At 3 years following anterior STEMI there is reduction of LV dilation in about 21% of patients associated with increases in ejection fraction in those with or without clearly dilated ventricles at 1year. These findings add to the complexity of LV remodeling and possibly suggest very late changes in infarct size.

Omnipolarity applied to equi-spaced electrode array for ventricular tachycardia substrate mapping.

AIMS: Bipolar electrogram (BiEGM)-based substrate maps are heavily influenced by direction of a wavefront to the mapping bipole. In this study, we evaluate high-resolution, orientation-independent peak-to-peak voltage (Vpp) maps obtained with an equi-spaced electrode array and omnipolar EGMs (OTEGMs), measure its beat-to-beat consistency, and assess its ability to delineate diseased areas within the myocardium compared against traditional BiEGMs on two orientations: along (AL) and across (AC) array splines. METHODS AND RESULTS: The endocardium of the left ventricle of 10 pigs (three healthy and seven infarcted) were each mapped using an Advisor™ HD grid with a research EnSite Precision™ system. Cardiac magnetic resonance images with late gadolinium enhancement were registered with electroanatomical maps and were used for gross scar delineation. Over healthy areas, OTEGM Vpp values are larger than AL bipoles by 27% and AC bipoles by 26%, and over infarcted areas OTEGM Vpp values are 23% larger than AL bipoles and 27% larger than AC bipoles (P < 0.05). Omnipolar EGM voltage maps were 37% denser than BiEGM maps. In addition, OTEGM Vpp values are more consistent than bipolar Vpps showing less beat-by-beat variation than BiEGM by 39% and 47% over both infarcted and healthy areas, respectively (P < 0.01). Omnipolar EGM better delineate infarcted areas than traditional BiEGMs from both orientations. CONCLUSION: An equi-spaced electrode grid when combined with omnipolar methodology yielded the largest detectable bipolar-like voltage and is void of directional influences, providing reliable voltage assessment within infarcted and non-infarcted regions of the heart.

Essential role of ryanodine receptor 2 phosphorylation in the effect of azumolene on ventricular arrhythmia vulnerability in a rabbit heart model.

INTRODUCTION: Following long-duration ventricular fibrillation (LDVF), reinitiation of ventricular fibrillation (VF) poses a major challenge during resuscitation. Ryanodine receptor 2 (RyR2) becomes dysfunctional following VF. The relationship between LDVF, RyR2 modulation, and ventricular refibrillation, as well as the role of RyR2 phosphorylation, remains unknown. METHODS: Langendorff-perfused rabbit hearts were subjected to global ischemia and treated with azumolene (or vehicle alone in controls) upon reperfusion. After electrical induction of an initial LDVF episode, each heart was further stimulated electrically to assess reinducibility of VF. Myocardial calcium dynamics were assessed by optical mapping. RyR2 phosphorylation in left ventricular tissue extracts was analyzed by Western blot analysis. RESULTS: Fewer episodes of refibrillation (lasting ≥ 10 seconds) were induced in azumolene-treated hearts than in controls (P = 0.01); however, this reduction in refibrillation was abrogated in the presence of the protein kinase A inhibitor H89. Spontaneous calcium elevation was significantly lower in azumolene-treated hearts than in control hearts ( P = 0.002) and in hearts pretreated with H89 before azumolene ( P = 0.01). RyR2 phosphorylation at Ser2808 was higher in hearts subjected to LDVF than in non-VF hearts ( P = 0.029), while no significant difference was found at Ser2814. Pretreatment with H89 led to significantly less RyR2 phosphorylation at Ser2808 ( P = 0.04) after LDVF, while pretreatment with KN93 or azumolene alone showed no effects on RyR2 phosphorylation. CONCLUSION: Ventricular refibrillation following LDVF was reduced by azumolene, which also improves calcium dynamics. RyR2 phosphorylation at Ser2808 is a prerequisite for the beneficial effects of azumolene.

The effect of left ventricular pacing on transmural activation delay in myopathic human hearts.

Aims: Left ventricular (LV) epicardial pacing (LVEpiP) in human myopathic hearts does not decrease global epicardial activation delay compared with right ventricular (RV) endocardial pacing (RVEndoP); however, the effect on transmural activation delay has not been evaluated. To characterize the transmural electrical activation delay in human myopathic hearts during RVEndoP and LVEpiP compared with global epicardial activation delay. Methods and results: Explanted hearts from seven patients (5 male, 46 ± 10 years) undergoing cardiac transplantation were Langendorff-perfused and mapped using an epicardial sock electrode array (112 electrodes) and 25 transmural plunge needles (four electrodes, 2 mm spacing), for a total of 100 unipolar transmural electrodes. Electrograms were recorded during LVEpiP and RVEndoP, and epicardial (sock) and transmural (needle) activation times, along with patterns of activation, were compared. There was no difference between the global epicardial activation times (LVEpiP 147 ± 8 ms vs. RVEndoP 156 ± 17 ms, P = 0.46). The mean LV transmural activation time during LVEpiP was significantly shorter than that during RVEndoP (125 ± 44 vs. 172 ± 43 ms, P < 0.001). During LVEpiP, of the transmural layers endo-, mid-myocardium and epicardium, LV endocardial layer was often the earliest compared with other transmural layers. Conclusion: In myopathic human hearts, LVEpiP did not decrease global epicardial activation delays compared with RVEndoP. LV epicardial pacing led to early activation of the LV endocardium, revealing the importance of the LV endocardium even when pacing from the LV epicardium.

Personalized voltage maps guided by cardiac magnetic resonance in the era of high-density mapping.

BACKGROUND: Voltage mapping could identify the conducting channels potentially responsible for ventricular tachycardia (VT). Standard thresholds (0.5-1.5 mV) were established using bipolar catheters. No thresholds have been analyzed with high-density mapping catheters. In addition, channels identified by cardiac magnetic resonance (CMR) has been proven to be related with VT. OBJECTIVE: The purpose of this study was to analyze the diagnostic yield of a personalized voltage map using CMR to guide the adjustment of voltage thresholds. METHODS: All consecutive patients with scar-related VT undergoing ablation after CMR (from October 2018 to December 2020) were included. First, personalized CMR-guided voltage thresholds were defined systematically according to the distribution of the scar and channels. Second, to validate these new thresholds, a comparison with standard thresholds (0.5-1.5 mV) was performed. Tissue characteristics of areas identified as deceleration zones (DZs) were recorded for each pair of thresholds. In addition, the relation of VT circuits with voltage channels was analyzed for both maps. RESULTS: Thirty-two patients were included [mean age 66.6 ± 11.2 years; 25 (78.1%) ischemic cardiomyopathy]. Overall, 52 DZs were observed: 44.2% were identified as border zone tissue with standard cutoffs vs 75.0% using personalized voltage thresholds (P = .003). Of the 31 VT isthmuses detected, only 35.5% correlated with a voltage channel with standard thresholds vs 74.2% using adjusted thresholds (P = .005). Adjusted cutoff bipolar voltages that better matched CMR images were 0.51 ± 0.32 and 1.79 ± 0.71 mV with high interindividual variability (from 0.14-1.68 to 0.7-3.21 mV). CONCLUSION: Personalized voltage CMR-guided personalized voltage maps enable a better identification of the substrate with a higher correlation with both DZs and VT isthmuses than do conventional voltage maps using fixed thresholds.

Predictors of failed left bundle branch pacing implant in heart failure with reduced ejection fraction: Importance of left ventricular diameter and QRS morphology.

BACKGROUND: Left bundle branch pacing (LBBP) is considered an alternative to cardiac resynchronization therapy (CRT). However, LBBP is not suitable for all patients with heart failure. OBJECTIVE: The aim of our study was to identify predictors of unsuccessful LBBP implantation in CRT candidates. METHODS: A cohort of consecutive patients with indications for CRT were included. Clinical, echocardiographic, and electrocardiographic variables were prospectively recorded. RESULTS: A total of 187 patients were included in the analysis. LBBP implantation was successful in 152 of 187 patients (81.2%) and failed in 35 of 187 patients (18.7%). The causes of unsuccessful implantation were unsatisfactory paced QRS morphology (28 of 35 [80%]), inability to screw the helix (4 of 35 [11.4%]), lead instability (2 of 35 [5.7%]), and high pacing thresholds (1 of 35 [2.8%]). The left ventricular end-diastolic diameter (LVEDD), non-LBBB (left bundle branch block) QRS morphology, and QRS width were predictors of failed implantation according to the univariate analysis. According to the multivariate regression analysis, LVEDD (odds ratio 1.31 per 5-mm increase; 95% confidence interval 1.05-1.63 per 5-mm increase; P = .02) and non-LBBB (odds ratio 3.07; 95% confidence interval 1.08-8.72; P = .03) were found to be independent predictors of unsuccessful LBBP implantation. An LVEDD of 60 mm has 60% sensitivity and 71% specificity for predicting LBBP implant failure. CONCLUSION: When LBBP was used as CRT, LVEDD and non-LBBB QRS morphology predicted unsuccessful implantation. Non-LBBB triples the likelihood of failed implantation independent of LVEDD. Caution should be taken when considering these parameters to plan the best pacing strategy for patients.

Longitudinal comparison of dyssynchrony correction and 'strain' improvement by conduction system pacing: LEVEL-AT trial secondary findings.

AIMS: Longitudinal dyssynchrony correction and 'strain' improvement by comparable cardiac resynchronization therapy (CRT) techniques is unreported. Our purpose was to compare echocardiographic dyssynchrony correction and 'strain' improvement by conduction system pacing (CSP) vs. biventricular pacing (BiVP) as a marker of contractility improvement during 1-year follow-up. METHODS AND RESULTS: A treatment-received analysis was performed in patients included in the LEVEL-AT trial (NCT04054895), randomized to CSP or BiVP, and evaluated at baseline (ON and OFF programming) and at 6 and 12 months (n = 69, 32% women). Analysis included intraventricular (septal flash), interventricular (difference between left and right ventricular outflow times), and atrioventricular (diastolic filling time) dyssynchrony and 'strain' parameters [septal rebound, global longitudinal 'strain' (GLS), LBBB pattern, and mechanical dispersion). Baseline left ventricular ejection fraction (LVEF) was 27.5 ± 7%, and LV end-systolic volume (LVESV) was 138 ± 77 mL, without differences between groups. Longitudinal analysis showed LVEF and LVESV improvement (P < 0.001), without between-group differences. At 12-month follow-up, adjusted mean LVEF was 46% with CSP (95% CI 42.2 and 49.3%) vs. 43% with BiVP (95% CI 39.6 and 45.8%), (P = 0.31), and LVESV was 80 mL (95% CI 55.3 and 104.5 mL) vs. 100 mL (95% CI 78.7 and 121.6 mL), respectively (P = 0.66). Longitudinal analysis showed a significant improvement of all dyssynchrony parameters and GLS over time (P < 0.001), without differences between groups. Baseline GLS significantly correlated with LVEF and LVESV at 12-month follow-up. CONCLUSION: CSP and BiVP provided similar dyssynchrony and 'strain' correction over time. Baseline global longitudinal 'strain' predicted ventricular remodelling at 12-month follow-up.