Electrogram Duration Research Articles

Near-field detection and peak frequency metric for substrate and activation mapping of ventricular tachycardias in two- and three-dimensional circuits.

Successful ventricular arrhythmia (VA) ablation requires identification of functionally critical sites during contact mapping. Estimation of the peak frequency (PF) component of the electrogram (EGM) may improve correct near-field (NF) annotation to identify circuit segments on the mapped surface. In turn, assessment of NF and far-field (FF) EGMs may delineate the three-dimensional path of a ventricular tachycardia (VT) circuit. A proprietary NF detection algorithm was applied retrospectively to scar-related re-entry VT maps and compared with manually reviewed maps employing first deflection (FDcorr) for VT activation maps and last deflection (LD) for substrate maps. Ventricular tachycardia isthmus location and characteristics mapped with FDcorr vs. NF were compared. Omnipolar low-voltage areas, late activating areas, and deceleration zones (DZ) in LD vs. NF substrate maps were compared. On substrate maps, PF estimation was compared between isthmus and bystander sites. Activation mapping with entrainment and/or VT termination with radiofrequency (RF) ablation confirmed critical sites. Eighteen patients with high-density VT activation and substrate maps (55.6% ischaemic) were included. Near-field detection correctly located critical parts of the circuit in 77.7% of the cases compared with manually reviewed VT maps as reference. In substrate maps, NF detection identified deceleration zones in 88.8% of cases, which overlapped with FDcorr VT isthmus in 72.2% compared with 83.3% overlap of DZ assessed by LD. Applied to substrate maps, PF as a stand-alone feature did not differentiate VT isthmus sites from low-voltage bystander sites. Omnipolar voltage was significantly higher at isthmus sites with longer EGM durations compared with low-voltage bystander sites. The NF algorithm may enable rapid high-density activation mapping of VT circuits in the NF of the mapped surface. Integrated assessment and combined analysis of NF and FF EGM-components could support characterization of three-dimensional VT circuits with intramural segments. For scar-related substrate mapping, PF as a stand-alone EGM feature did not enable the differentiation of functionally critical sites of the dominant VT from low-voltage bystander sites in this cohort.

Functional substrate analysis in patients with persistent atrial fibrillation.

The aim of this study was to describe the correlation between atrial electrogram duration map (AEDUM), spatiotemporal electrogram dispersion (STED) and low voltage areas (LVA) in patients with persistent atrial fibrillation (PsAF). The degree of left atrial (LA) tissue remodelling and augmented anisotropic conduction is one of the major issues related to PsAF ablation outcome. This study enrolled consecutive patients with PsAF undergoing pulmonary vein isolation. In all patients, voltage, AEDUM and STED maps were created, and the correlation was reported between these three mapping methods. A total of 40 patients with PsAF were enrolled. The mean age was 62.2 ± 7.4years, and males were 72.5% (n = 29). The overall bipolar voltage of the LA was 3.06 ± 1.87mV. All patients had at least one AEDUM area (overall AEDUM area: 21.8 ± 8.2 cm2); the mean longest electrogram (EGMs) duration was 90 ± 19ms. STED areas with < 120ms was 46.3 ± 20.2 cm2 which covered 45 ± 22% of the LA surface. AEDUM and STED areas were most frequently reported on the roof, the anterior wall and the septum. The extension of the AEDUM areas was significantly smaller than STED areas with CL < 120ms (21.8 ± 8.2 vs 46.3 ± 20.2; p-value < 0.0001). In 24 patients (60%), AEDUM areas was entirely included in the STED areas with CL < 120ms. In the three (7.5%) patients with LVA, no correspondence with STED and AEDUM was noted. AEDUM and STED maps allow to identify areas of conductive dysfunction as a possible atrial substrate even if a normal voltage is detected.

Ablation of persistent atrial fibrillation based on atrial electrogram duration map: methodology and clinical outcomes from the AEDUM pilot study

Abstract Background Catheter ablation of persistent atrial fibrillation (PsAF) represents a challenge for the electrophysiologist and there are still divergences regarding the best ablative approach to adopt. Objectives Create a new map of the duration of atrial bipolar electrograms (Atrial Electrogram DUration Map, AEDUM) to recognize a functional substrate during sinus rhythm and guide a patient-tailored ablative strategy for PsAF. Methods 40 PsAF subjects were assigned in a 1:1 ratio to either for PVI alone (Group B1) or PVI+AEDUM areas ablation (Group B2). A cohort of 15 patients without AF history undergoing left-sided accessory pathway ablation was used as a control group (Group A). In all patients, voltage and AEDUM maps were created during sinus rhythm. The minimum follow-up was 12-months, with rhythm monitoring via 48-h ECG Holter or by implantable cardiac device. Results Electrogram (EGM) duration was higher in Group B than in Group A (49±16.2ms vs 34.2±3.8ms; p-value&amp;lt;0.001). In Group B the mean cumulative AEDUM area was 21.8±8.2cm2; no difference between the two subgroups was observed (22.3±9.1cm2 vs 21.2±7.2cm2; p-value=0.45). The overall bipolar voltage recorded inside the AEDUM areas was lower than in the remaining atrial areas [median:1.30mV (IQR:0.71–2.38mV) vs 1.54mV (IQR:0.79–2.97mV); p-value:&amp;lt;0.001)]. Low voltage areas (&amp;lt;0.5mV) were recorded in three (7.5%) patients in Group B. During the follow-up [median 511 days(376-845days)] patients who underwent PVI-only experienced more AF recurrence than those receiving a tailored approach (65% vs 35%; p-value=0.04). Conclusions All PsAF patients exhibited AEDUM areas. An ablation approach targeting these areas resulted in a more effective strategy compared with PVI only.AEDUM mapAEDUM map and lesion set

Ablation of persistent atrial fibrillation based on atrial electrogram duration map: methodology and clinical outcomes from the AEDUM pilot study

BackgroundCatheter ablation of persistent atrial fibrillation (PsAF) represents a challenge for the electrophysiologist and there are still divergences regarding the best ablative approach to adopt. Create a new map of the duration of atrial bipolar electrograms (Atrial Electrogram DUration Map, AEDUM) to recognize a functional substrate during sinus rhythm and guide a patient-tailored ablative strategy for PsAF.MethodsForty PsAF subjects were assigned in a 1:1 ratio to either for PVI alone (Group B1) or PVI+AEDUM areas ablation (Group B2). A cohort of 15 patients without AF history undergoing left-sided accessory pathway ablation was used as a control group (Group A). In all patients, voltage and AEDUM maps were created during sinus rhythm. The minimum follow-up was 12 months, with rhythm monitoring via 48-h ECG Holter or by implantable cardiac device.ResultsElectrogram (EGM) duration was higher in Group B than in Group A (49±16.2ms vs 34.2±3.8ms; p-value<0.001). In Group B the mean cumulative AEDUM area was 21.8±8.2cm2; no difference between the two subgroups was observed (22.3±9.1cm2 vs 21.2±7.2cm2; p-value=0.45). The overall bipolar voltage recorded inside the AEDUM areas was lower than in the remaining atrial areas [median: 1.30mV (IQR: 0.71–2.38mV) vs 1.54mV (IQR: 0.79–2.97mV); p-value: <0.001)]. Low voltage areas (<0.5mV) were recorded in three (7.5%) patients in Group B. During the follow-up [median 511 days (376–845days)] patients who underwent PVI-only experienced more AF recurrence than those receiving a tailored approach (65% vs 35%; p-value= 0.04).ConclusionsAll PsAF patients exhibited AEDUM areas. An ablation approach targeting these areas resulted in a more effective strategy compared with PVI only.Graphical

Functional mapping to reveal slow conduction and substrate progression in atrial fibrillation.

The aim of our study was to analyse the response to short-coupled atrial extrastimuli to identify areas of hidden slow conduction (HSC) and their relationship with the atrial fibrillation (AF) phenotype. Twenty consecutive patients with paroxysmal AF and persistent AF (10:10) underwent the first pulmonary vein isolation procedure. Triple short-coupled extrastimuli were delivered in sinus rhythm (SR), and the evoked response was analysed: sites exhibiting double or highly fragmented electrograms (EGM) were defined as positive for HSC (HSC+). The delta of the duration of the bipolar EGM was analysed, and bipolar EGM duration maps were built. High-density maps were acquired using a multipolar catheter during AF, SR, and paced rhythm. Spatial co-localization of HSC+ and complex fractionated atrial EGMs (CFAE) during AF was evaluated. Persistent AF showed a higher number and percentage of HSC+ than paroxysmal AF (13.9% vs. 3.3%, P < 0.001). The delta of EGM duration was 53 ± 22 ms for HSC+ compared with 13 ± 11 (10) ms in sites with negative HSC (HSC-) (P < 0.001). The number and density of HSC+ were lower than CFAE during AF (19 vs. 56 per map, P < 0.001). The reproducibility and distribution of HSC+ in repeated maps were superior to CFAE (P = 0.19 vs. P < 0.001). Sites with negative and positive responses showed a similar bipolar voltage in the preceding sinus beat (1.65 ± 1.34 and 1.48 ± 1.47 mV, P = 0.12). Functional mapping identifies more discrete and reproducible abnormal substrates than mapping during AF. The HSC+ sites in response to triple extrastimuli are more frequent in persistent AF than in paroxysmal AF.

Ventricular Electrograms Duration Map to Detect Ventricular Arrhythmia Substrate: the VEDUM Project Study.

The analysis of the wave-front activation patterns is crucial for the comprehension and treatment of ventricular tachycardia (VT). The ventricular electrograms duration map (VEDUM) is a potential method to identify areas (VEDUM area) with slow and inhomogeneous activation. There is no available data on the characteristics and the arrhythmogenic role of VEDUM areas identified during sinus/paced rhythm. Patients referred for VT ablation were enrolled at 3 different centers. VEDUM maps during sinus/paced rhythm as well as substrate and functional maps were created; activation mapping was performed for all hemodynamically tolerated VT. Thirty-two patients (mean age:70.1±9.4 years; males 93.8%) were enrolled. The VEDUM approach was achieved in all patients and the mean size of the VEDUM area was 12.1±6.9 cm2 (interquartile range, 7.8-14.9 cm2). A significative difference was observed between the electrogram duration in the VEDUM area and the normal tissue (163.7 ms [interquartile range, 142.3-199.2 ms]; versus 65.5 ms [interquartile range, 59.5-76.2 ms]; P<0.001). The VEDUM area was visualized in a dense scar (<0.5 mV) in 19 (59.4%) patients. A deceleration zone and late potentials were recorded inside the VEDUM area in 56.3% and 81.3%, respectively. When a complete VT activation mapping was available, the isthmus projected in the VEDUM area in 93.5% of patients; 8 of them had multiple VTs mapped and in the 87.5% all VT isthmuses were included in the VEDUM area. VEDUM maps allow the identification of discrete areas of inhomogeneous and slow conduction. They represent a potential target for VT ablation, including patients with multiple morphologies.

Electroanatomical features of biopsy-proven cardiac amyloidosis

Abstract Funding Acknowledgements Type of funding sources: None. Background Cardiac amyloidoses (CA) are an increasingly recognized group of infiltrative cardiomyopathies associated with high risk of heart failure, thromboembolic events, arrhythmias, and sudden death. Endomyocardial biopsy may be required to differentiate the amyloid type (mainly, Immunoglobulin light chain [AL] versus transthyretin-related [ATTR]) in some cases. Purpose to provide a first description of electroanatomical characteristics of amyloid cardiomyopathy, and relate them to endomyocardial biopsy findings. Methods we enrolled ten consecutive patients (median age, 68 [63-77]; male, 50%) in an observational, retrospective study. All of them had a clinical diagnosis of CA, but a diagnosis of CA type was hampered by the presence of inconclusive or discordant laboratory-imaging findings (abnormal serum free light chain assay and positive bone scintigraphy, n=5; ambiguous imaging results, n=4; abnormal serum free light chain assay and TTR gene mutation, n=1). Therefore, all patients underwent right ventricular high-density electroanatomical mapping (EAM) using a multipolar catheter (Advisor HD Grid, Abbott), and EAM-guided endomyocardial biopsy (EMB). We recorded electrogram features at EMB sampling site, and explored their correlation with histological findings with mixed effect models. Results The clinical, electroanatomical, and histological features of enrolled patients according to the EMB-proven type of CA (AL, n=6; ATTR, n=4) are resumed in Table. Electrogram amplitudes in both the bipolar and the unipolar configuration were generally normal both in the overall right ventricle, and at EMB sites. We found a significant correlation between both unipolar and bipolar electrogram amplitude and the percentage of both amyloid tissue (p&amp;lt;0.01 and p=0.016, respectively) and fibrous tissue (both p&amp;lt;0.01) at EMB (Figure). We observed the strongest linear association (i.e., highest R2) between unipolar electrogram amplitude and amyloid tissue, as well as between bipolar electrogram amplitude and fibrous tissue. On the other hand, electrogram duration and the number of electrogram peaks were unrelated to histological findings. The unipolar voltage cutoff that best identified regions with &amp;gt;15% amyloid tissue infiltration according to Youden index was 9.1 mV (sensitivity, 43%; specificity, 100%; accuracy, 77%). Conclusion CA is associated with normal electrogram amplitudes using ahigh density mapping catheter and conventional voltage cutoffs. Nevertheless, unipolar electrogram amplitude is strongly related to the extent of amyloid infiltration, and unipolar voltage&amp;lt;9.1 mV is 100% specific for &amp;gt;15% amyloid tissue deposition.

A novel method to define critical isthmus of left atrial tachycardia; late potential mapping during sinus rhythm

Abstract Funding Acknowledgements Type of funding sources: None. Background Atrial tachycardia (AT) is a commonly encountered rhythm disorder in patients with underlying atrial scar. The role of late potential (LP) based mapping in the detection of AT critical isthmus has yet to be systematically evaluated. Purpose We aimed to investigate the relationship between the atrial LPs (ALP) localization in sinus rhythm and the critical isthmus of re-entrant ATs in patients with underlying atrial low-voltage areas. Methods Thirty-five symptomatic patients [mean age: 62 ±9, gender: 25 (71.4%) female] with left AT, who had undergone catheter ablation, were enrolled. Voltage and LP mapping were performed in sinus rhythm in both atriums. Low voltage areas and signals with continuous-fragmented morphology were tagged. Isochronal late activation mapping (ILAM) was also performed in all procedures. After induction of AT, activation mapping was performed during tachycardia in all patients to detect critical sites of the tachycardia. Results Activation mapping indicated single re-entry in 30 patients and ≥1 re-entry in 5 patients. Localized re-entry was observed in 20 (51.2%) patients, macro re-entry in 18 (46.1%), and biatrial re-entry in 1(2.5%). The mean fractionated electrogram duration in the AT termination site was calculated at 134.3±46.7 ms and the mean bipolar voltage at 0.17±0.12 mV. The ALPs were tagged in 25 (64.1%) patients on the anterior wall, 12 (34.3%) on the roof, 5 (12.8%) on the septal wall and 2 (5.7%) in the Bachmann’s Bundle region. All ALPs were in the latest activated zones of ILAM in patients with localized re-entry and predicted successful ablation sites to terminate the AT. Freedom from atrial tachyarrhythmias (ATAs) was 78.7% at six months during a mean follow-up duration of 338 ±226 days. Conclusion Our findings demonstrated the utility of ALPs during sinus rhythm to predict the successful termination sites for left ATs. These areas displayed continuous-fragmented signal morphology during sinus/paced rhythm in correlation with the critical isthmus of AT detected during activation mapping.

Systematic identification of low voltage-high frequency electrogram zones at sites of left atrial reentrant tachycardia termination

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Abbott Laboratories Background Localization of the critical isthmus of conduction of LAMRT circuits within scar tissue is challenging (Panel A). Low voltage (LV) has been used as a marker for the arrhythmic substrate. However, voltage amplitudes due to near field (NF) vs. far-field (FF) electrogram (EGM) components are not clearly differentiated. The peak frequency (PF) associated with bipolar EGM’s is a novel parameter which may distinguish them (Panel B). Purpose To compare the ability of LV vs. LVHF to discriminate the LAMRT termination region Methods Bipolar voltage and activation maps were generated with a 16-pole grid catheter (Advisor HD Grid) during LAMRT (Panels A,C). Peak frequency maps were retrospectively computed (Panels B,D). LAMRT’s were included if acute termination could be achieved by focal RF lesion set restricted to a boundary &amp;lt;1.5cm diameter. The left atrial (LA) mapped surface was sub-regioned into the termination (T-ZONE) and non-termination (NT-ZONE) zones. The T-ZONE surface was centered about the site of termination and was allowed to extend to a rectangular kernel &amp;gt;0.5cm and &amp;lt;1.5cm across perpendicular axes, with the NT-ZONE encompassing the remainder of the mapped surface area (SA). Sensitivity (SE) and specificity (SP) of discrimination of the T-ZONE vs. NT-ZONE was measured according to the %T-ZONE vs. %NT-ZONE SA occupied at LV thresholds ranging from 0.1-1.0mV in increments of 0.1mV (Panel E). In addition to LV, LVHF at peak frequency cutoffs of 150Hz (LVHF150), 200Hz (LVHF200), 250Hz (LVHF250) and 300Hz (LVHF300) were also assessed for T-ZONE discrimination (Panels F,G). Results Of 16 consecutive patients with 24 ATs prospectively enrolled, 13 LAMRT’s from 13 patients met the termination criteria for inclusion. LAMRT termination consisted of a mean of 2.85±2.82 focal RF lesions. The T-ZONE occupied a mean SA of 0.82±0.30cm2 (41±19 EGM points) vs. 158.6±42.2cm2 (2967±1227 points) for the NT-ZONE. While the mean voltage from the T-ZONE was significantly lower vs. the NT-Zone (0.12±0.05mV vs. 0.60±0.28mV respectively), mean T-ZONE peak frequency of the was significantly higher vs. the NT-ZONE (345±76Hz vs. 255±34Hz). The maximum EGM duration in the T-ZONE was 172±63ms. ROC discrimination of the T-ZONE resulted in AUC’s of 0.69- LV, 0.76- LVHF150, 0.80- LVHF200, 0.81- LVHF250 and 0.76- LVHF300. LVHF200 and LVHF250 yielded the best improvements in AUC vs. LV unconstrained by high PF (11.3% and 12.2% respectively)(Panel G). LVHF200 with a cutoff of 0.2mV yielded a balanced SE/SP of 0.86/0.83 respectively, while LVHF250 with a cutoff of 0.3mV yielded a balanced SE/SP of 0.85/0.84. Conclusion During AT, systematic identification of EGM regions of high frequency within low voltage can significantly improve discrimination of the site of AT. termination, beyond.

PO-02-213 ELECTROANATOMICAL ASPECTS OF BIOPSY-PROVEN CARDIAC AMYLOIDOSIS

Cardiac amyloidoses (CA) are a common and increasingly recognized group of infiltrative cardiomyopathies associated with high risk of heart failure, thromboembolic events, arrhythmias, and sudden death. Endomyocardial biopsy may be required to differentiate the amyloid type (mainly, Immunoglobulin light chain [AL] versus transthyretin-related [ATTR]) in selected cases. To describe electroanatomical characteristics of amyloid cardiomyopathy, and relate them to endomyocardial biopsy findings. We included ten consecutive patients (median age, 68 [63-77]; male, 50%) in an observational, retrospective study. All of them had a clinical diagnosis of CA, but a diagnosis of CA type was uncertain based on non-invasive findings. Therefore, all patients underwent right ventricular high-density electroanatomical mapping (EAM) using a multipolar catheter (Advisor HD Grid, Abbott), and EAM-guided endomyocardial biopsy (EMB). We recorded electrogram features at EMB sampling site, and assessed their correlation with histological findings with mixed effect models. The clinical, electroanatomical, and histological features of enrolled patients according to the EMB-proven type of CA (AL, n=6; ATTR, n=4) are resumed in Table. Electrogram amplitudes in both the bipolar and the unipolar configurations were largely preserved in the overall right ventricle, and at EMB sites. There were highly significant correlations among electrogram amplitudes in both the unipolar and bipolar configurations, and the extent of amyloid and fibrous tissue substitution at EMB (all p<0.01, Figure). We observed the strongest linear associations (i.e., highest R2) between unipolar electrogram amplitude and the percentage of amyloid tissue, as well as between bipolar electrogram amplitude and the percentage of fibrous tissue. On the other hand, electrogram duration and the number of electrogram peaks were unrelated to histological findings. The unipolar voltage cutoff that best identified regions with >15% amyloid tissue infiltration according to Youden index was 9.1 mV (sensitivity, 43%; specificity, 100%; accuracy, 77%). CA is associated with preserved electrogram amplitudes at high-density electroanatomical mapping with conventional voltage cutoffs. Nevertheless, unipolar electrogram amplitude is strongly related to the extent of amyloid infiltration, and unipolar voltage<9.1 mV is 100% specific for >15% amyloid tissue deposition.

Epicardial electrical heterogeneity after amiodarone treatment increases vulnerability to ventricular arrhythmias under therapeutic hypothermia.

Amiodarone is commonly used during therapeutic hypothermia (TH) following cardiac arrest due to ventricular arrhythmias. However, electrophysiological changes and proarrhythmic risk after amiodarone treatment have not yet been explored in TH. Epicardial high-density bi-ventricular mapping was performed in pigs under baseline temperature (BT), TH (32-34°C), and amiodarone treatment during TH. The total activation time (TAT), conduction velocity (CV), local electrogram (LE) duration, and wavefront propagation from pre-specified segments were analyzed during sinus rhythm (SR) or right ventricular (RV) pacing (RVP), along with tissue expression of connexin 43. The vulnerability to ventricular arrhythmias was assessed. Compared to BT, TH increased the global TAT, decreased the CV, and generated heterogeneous electrical substrate during SR and RVP. During TH, the CV reduction and LE duration prolongation were greater in the anterior mid RV than in the other areas, which changed the wavefront propagation in all animals. Compared to TH alone, amiodarone treatment during TH further increased the TAT and LE duration and decreased the CV. Heterogeneous conduction was partially attenuated after amiodarone treatment. After TH and amiodarone treatment, the connexin 43 expression in the anterior mid RV was lower than that in the other areas, compatible with the heterogeneous CV reduction. The animals under TH and amiodarone treatment had a higher incidence of inducible ventricular arrhythmias than those under BT or TH without amiodarone. Electrical heterogeneity during amiodarone treatment and TH was associated with vulnerability to ventricular arrhythmias.

The transmural activation interval: a new mapping tool to identify ventricular tachycardia substrates in right ventricular cardiomyopathy.

In right ventricular cardiomyopathy (RVCM), intramural scar may prevent rapid transmural activation, which may facilitate subepicardial ventricular tachycardia (VT) circuits. A critical transmural activation delay determined during sinus rhythm (SR) may identify VT substrates in RVCM. Consecutive patients with RVCM who underwent detailed endocardial-epicardial mapping and ablation for scar-related VT were enrolled. The transmural activation interval (TAI, first endocardial to first epicardial activation) and maximal activation interval (MAI, first endocardial to last epicardial activation) were determined in endocardial-epicardial point pairs located <10 mm apart. VT-related sites were determined by conventional substrate mapping and limited activation mapping when possible. Nineteen patients (46 ± 16 years, 84% male, 63% arrhythmogenic right ventricular cardiomyopathy, 37% exercise-induced arrhythmogenic remodelling) were inducible for 44 VT [CL 283 (interquartile range, IQR 240-325)ms]. A total of 2569 endocardial-epicardial coupled point pairs were analysed, including 98 (4%) epicardial VT-related sites.The TAI and MAI were significantly longer at VT-related sites compared with other electroanatomical scar sites [TAI median 31 (IQR 11-50) vs. 2 (-7-11)ms, P < 0.001; MAI median 65 (IQR 45-87) vs. 23 (13-39)ms, P < 0.001]. TAI and MAI allowed highly accurate identification of epicardial VT-related sites (optimal cut-off TAI 17 ms and MAI 45 ms, both AUC 0.81). Both TAI and MAI had a better predictive accuracy for VT-related sites than endocardial and epicardial voltage and electrogram (EGM) duration (AUC 0.51-0.73). The transmural activation delay in SR can be used to identify VT substrates in patients with RVCM and predominantly hemodynamically non-tolerated VT, and may be an important new mapping tool for substrate-based ablation.

Fixed complex electrograms during sinus rhythm and local pacing: potential ablation targets for persistent atrial fibrillation

In atrial fibrillation (AF) patients, complex electrograms during sinus rhythm (C-EGMs) could be pathological or not. We aimed to demonstrate whether local pacing was helpful to discern pathological C-EGMs. 126 persistent AF patients and 27 patients with left-side accessory pathway (LAP) underwent left atrial mapping during sinus rhythm. If C-EGMs were detected, local pacing was performed. If the electrograms turned normal, we defined them as non-fixed C-EGMs, otherwise as fixed C-EGMs. No difference was detected in the incidence and proportion of non-fixed C-EGMs between AF patients and LAP patients (101/126 vs. 19/27, P = 0.26; 9.1 ± 6.0% vs. 7.7 ± 5.7%, P = 0.28). However, the incidence and proportion of fixed C-EGMs were higher in persistent AF patients (87/126 vs. 1/27, P < 0.01; 4.3 ± 3.4% vs. 0.1 ± 0.5%, P < 0.01). Compared with non-fixed C-EGMs, fixed C-EGMs had lower amplitudes, longer electrogram durations and longer Stimuli-P wave internals. All AF patients received circumferential pulmonary vein isolation. Among AF patients with fixed C-EGMs, 45 patients received fixed C-EGMs ablation and 42 patients underwent linear ablation. Compared with linear ablation, fixed C-EGMs ablation reduced recurrence (HR: 0.43; 95% CI 0.21‐0.81; P = 0.011). Among patients without fixed C-EGMs ablation, the proportion of fixed C-EGMs was an independent predictor of ablation outcomes (HR for per percent: 1.13, 95% CI 1.01–1.28, P = 0.038). C-EGMs could be classified into fixed and non-fixed C-EGMs through local pacing. Fixed rather than non-fixed C-EGMs might indicate abnormal atrial substrates and fixed C-EGMs ablation improve outcomes of persistent AF ablation.

Multisite conduction block in the epicardial substrate of Brugada syndrome.

The Brugada pattern manifests as a spontaneous variability of the electrocardiographic marker, suggesting a variability of the underlying electrical substrate. The purpose of this study was to investigate the response of the epicardial substrate of Brugada syndrome (BrS) to programmed ventricular stimulation and to Na blocker infusion. We investigated 6 patients (all male; mean age 54 ± 14 years) with BrS and recurrent ventricular fibrillation. Five had no type 1 BrS electrocardiogram pattern at admission. They underwent combined epicardial-endocardial mapping using multielectrode catheters. Changes in epicardial electrograms were evaluated during single endocardial extrastimulation and after low-dose ajmaline infusion (0.5 mg/kg in 5 minutes). All patients had a region in the anterior epicardial right ventricle with prolonged multicomponent electrograms. Single extrastimulation prolonged late epicardial components by 59 ± 31 ms and in 4 patients abolished epicardial components at some sites, without reactivation by surrounding activated sites. These localized blocks occurred at an initial coupling interval of 335 ± 58 ms and then expanded to other sites, being observed in up to 40% of epicardial sites. Ajmaline infusion prolonged electrogram duration in all and produced localized blocks in 62% of sites in the same patients as during extrastimulation. Epicardial conduction recovery after ajmaline occurred intermittently and at discontinuous sites and produced beat-to-beat changes in local repolarization, resulting in an area of marked electrical disparity. These changes were consistent with models based on microstructural alterations under critical propagation conditions. In BrS, localized functional conduction blocks occur at multiple epicardial sites and with variable patterns, without being reactivated from the surrounding sites.

Mechanism of the effects of sodium channel blockade on the arrhythmogenic substrate of Brugada syndrome.

The mechanisms by which sodium channel blockade and high-rate pacing modify electrogram (EGM) substrates of Brugada syndrome (BrS) have not been elucidated. The purpose of this study was to determine the effect of ajmaline and high pacing rate on the BrS substrates. Thirty-two patients with BrS (mean age 40 ± 12 years) and frequent ventricular fibrillation episodes underwent right ventricular outflow tract substrate electroanatomical and electrocardiographic imaging (ECGI) mapping before and after ajmaline administration and during high-rate atrial pacing. In 4 patients, epicardial mapping was performed using open thoracotomy with targeted biopsies. Ajmaline increased the activation time delay in the substrate (33%; P = .002), ST-segment elevation in the right precordial leads (74%; P < .0001), and the area of delayed activation (170%; P < .0001), coinciding with the increased substrate size (75%; P < .0001). High atrial pacing rate increased the abnormal EGM duration at the right ventricular outflow tract areas from 112 ± 48 to 143 ± 66 ms (P = .003) and produced intermittent conduction block and/or excitation failure at the substrate sites, especially after ajmaline administration. Biopsies from the 4 patients with thoracotomy showed epicardial fibrosis where EGMs were normal at baseline but became fractionated after ajmaline administration. In some areas, local activation was absent and unipolar EGMs had a monophasic morphology resembling the shape of the action potential. Sodium current reduction with ajmaline severely compromises impulse conduction at the BrS fibrotic substrates by producing fractionated EGMs, conduction block, or excitation failure, leading to the Brugada ECG pattern and favoring ventricular fibrillation genesis.

Effect of electrode size and spacing on electrograms: Optimized electrode configuration for near-field electrogram characterization.

Detailed effects of electrode size on electrograms (EGMs) have not been systematically examined. We aimed to elucidate the effect of electrode size on EGMs and investigate an optimal configuration of electrode size and interelectrode spacing for gap detection and far-field reduction. This study included 8 sheep in which probes with different electrode size and interelectrode spacing were epicardially placed on healthy, fatty, and lesion tissues for measurements. Between 3 electrode sizes (0.1 mm/0.2 mm/0.5 mm) with 3 mm spacing. As indices of capability in gap detection and far-field reduction, in different electrode sizes (0.1 mm/0.2 mm/0.5 mm) and interelectrode spacing (0.1 mm/0.2 mm/0.3 mm/0.5 mm/3mm) and the optimized electrode size and interelectrode spacing were determined. Compared between PentaRay and the optimal probe determined in study2. Study 1 demonstrated that unipolar voltage and the duration of EGMs increased as the electrode size increased in any tissue (P < .001). Bipolar EGMs had the same tendency in healthy/fat tissues, but not in lesions. Study 2 showed that significantly higher gap to lesion volume ratio and healthy to fat tissue voltage ratio were provided by a smaller electrode (0.2 mm or 0.3mm electrode) and smaller spacing (0.1 mm spacing), but 0.3 mm electrode/0.1 mm spacing provided a larger bipolar voltage (P < .05). Study 3 demonstrated that 0.3 mm electrode/0.1 mm spacing provided less deflection with more discrete EGMs (P<.0001) with longer and more reproducible AF cycle length (P< .0001) compared to PentaRay. Electrode size affects both unipolar and bipolar EGMs. Catheters with microelectrodes and very small interelectrode spacing may be superior in gap detection and far-field reduction. Importantly, this electrode configuration could dramatically reduce artifactual complex fractionated atrial electrograms and may open a new era for AF mapping.

Abstract 13947: Catheter-Induced Ectopy During Ventricular Electroanatomical Mapping: Simply Annoying or Potentially Useful?

Background: During ventricular catheter mapping to guide catheter ablation of scar-related ventricular tachycardia (VT), creating an electroanatomical map can be frustrated by catheter-induced ventricular ectopy. However, we observed anecdotally that catheter-induced ventricular ectopy may unmask local abnormal ventricular activities (LAVA). The aim of this study was to compare LAVA characteristics between catheter-induced ventricular ectopy and intrinsic ventricular conduction in post-infarction patients undergoing electroanatomic mapping. Methods: We performed a retrospective review of electroanatomical maps from 136 consecutive post-infarction VT patients who had undergone mapping using a contact force-sensing catheter (Thermocool STSF &amp; CARTO, Biosense Webster Inc). Patients who had any diagnostic catheters inside the ventricular were excluded. From 8 patients, 1154 discrete points were screened during sinus rhythm or right atrial pacing, and 443 points were identified to have ectopic and intrinsic beats - confirmed to be colocalized using show-catheter functionality. Results: Among 443 points, LAVA were identified in 151 points - either during catheter-induced ectopy or intrinsic rhythm. The interval from onset of QRS to ventricular electrogram (EGM) were measured: ectopy revealed negative values compared to intrinsic rhythm (-43.5 (-65.5, 0) vs 18.5 (0, 35.0), P&lt;0.001). Catheter-induced ectopy had significantly longer EGM duration (206.0ms (161.0, 285.0) vs 140.0 (123.8, 168.3), P&lt;0.001) and smaller EGM amplitude (0.59mV (0.34, 0.82) vs 0.66 (0.36, 1.06), P=0.003) compared to intrinsic rhythm. For 77 of 151 (51.0%) points, LAVA potentials were unmasked only during catheter-induced ectopy. Conclusions: During mapping of infarcted ventricles, catheter-induced ectopy offers potential insights into the underlying tissue, warranting further investigation as a guide to VT ablation.

A novel algorithm for 3-D visualization of electrogram duration for substrate-mapping in patients with ischemic heart disease and ventricular tachycardia.

BackgroundMyocardial slow conduction is a cornerstone of ventricular tachycardia (VT). Prolonged electrogram (EGM) duration is a useful surrogate parameter and manual annotation of EGM characteristics are widely used during catheter-based ablation of the arrhythmogenic substrate. However, this remains time-consuming and prone to inter-operator variability. We aimed to develop an algorithm for 3-D visualization of EGM duration relative to the 17-segment American Heart Association model.MethodsTo calculate and visualize EGM duration, in sinus rhythm acquired high-density maps of patients with ischemic cardiomyopathy undergoing substrate-based VT ablation using a 64-mini polar basket-catheter with low noise of 0.01 mV were analyzed. Using a custom developed algorithm based on standard deviation and threshold, the relationship between EGM duration, endocardial voltage and ablation areas was studied by creating 17-segment 3-D models and 2-D polar plots.Results140,508 EGMs from 272 segments (n = 16 patients, 94% male, age: 66±2.4, ejection fraction: 31±2%) were studied and 3-D visualization of EGM duration was performed. Analysis of signal processing parameters revealed that a 40 ms sliding SD-window, 15% SD-threshold and >70 ms EGM duration cutoff was chosen based on diagnostic odds ratio of 12.77 to visualize rapidly prolonged EGM durations. EGMs > 70 ms matched to 99% of areas within dense scar (<0.2 mV), in 95% of zones within scar border zone (0.2–1.0 mV) and detected ablated areas having resulted in non-inducibility at the end of the procedure. Ablation targets were identified with a sensitivity of 65.6% and a specificity of 94.6% avoiding false positive labeling of prolonged EGMs in segments with healthy myocardium.ConclusionThe novel algorithm allows rapid visualization of prolonged EGM durations. This may facilitate more objective characterization of arrhythmogenic substrate in patients with ischemic cardiomyopathy.

A novel ventricular map of electrograms duration as a method to identify areas of slow conduction during ablation of ventricular tachycardia

Abstract Funding Acknowledgements Type of funding sources: None. Background – Wave front inhomogeneous propagation is crucial for reentry circuit generation. Bipolar EGM duration is indicative of local conduction delay and may identify areas of low conduction as a functional substrate. This study aimed to create a map of EGM duration during the VT (VEDUM Map) to identify the area of the slowest conduction and to verify if RF delivery at this area allows to rapidly interrupt the VT. Methods – 24 high-density VTs maps (21 patients) were analyzed. Activation maps and voltage maps during SR were performed. An offline remap confirmed with MathLab software was customized to visualize the longest duration electrogram during VT. Results – All of the VTs were interrupted during the first RF delivery (mean time 7,3 ± 5,4 sec (range 3-25 sec)) at the area with the longest EGM duration (212 ± 47 ms (range 113-330 ms)). . In 9 pts (37,5%) the longest EGM was located at the entrance or exit area of the activation maps while in 5 pts (21%) the EGM covered the full diastolic phase. Finally, in 10 pts the longest EGM occurred in the mid-exit-diastolic phase. Conclusions - A novel Ventricular map of Electrograms DUration (VEDUM Map) is highly accurate in defining a conductive vulnerable zone of the VT circuit. The longest EGM duration within the isthmus is highly predictive of rapid VT termination. Quantitative variablesQualitative variablesMeanMedianStandard DeviationAge71738.40BMI26.624.54.02LV EDV16315442.7LV EDD61.2629.9LV EF38.7369.74VT cycle lenght (TCL)35537556.4EGM max. duration in VT21220847EGM max dur / TCL58.260.512Maximum EGM duration localization in CLProto = 12.5%Meso = 33.3%Tele = 25%Full = 20.8%Myocardium voltage characteristics in VEDUM EGMHealthy = 25%Transition = 20.8%Scar = 41.7%Critical Isthmus area12.3107.3VT Interruption during RFYes = 79.2%No = 20.8%Time (seconds) to interruption765Access typeEndo = 58.3%Epi = 29.2%Clinical and procedural dataAbstract Figure.

A novel Ventricular map of Electrograms DUration as a Method to identify areas of slow conduction for ventricular tachycardia ablation: The VEDUM pilot study

Bipolar electrogram (EGM) duration is indicative of local activation property and, if prolonged, is useful to discover areas of slow conduction favoring arrhythmias. The present study aimed to create a map of EGM duration during the ventricular tachycardia (VT) (Ventricular Electrograms DUration as a Method map [VEDUM map]) to verify if the slowest activation area is crucial for reentry and could represent a suitable target for rapid VT interruption during ablation. Prospectively 30 patients were enrolled for this study. Twenty-one patients were selected, and 24 VT maps with complete circuit delineation (>90% tachycardia cycle length) were analyzed. Activation and VEDUM maps during VT as well as voltage maps during sinus rhythm were created. Twenty-two of 24 VTs (88%) were interrupted during the first radiofrequency delivery (mean time 7.3 ± 5.4 seconds; range 3-25 seconds) at the area with the longest EGM duration (212±47 ms; range 113-330 ms). The mean percentage of the cycle length of VT covered by the EGM with the longest duration was 58% ± 12%. In 9 patients (37%), the longest EGM was located at the isthmus entrance, at the exit in 7 maps (30%), and the mid-isthmuses in 8 maps (33%). In 6 patients (25%), the EGM covered the full diastolic phase. The mean isthmus width was 28 ± 11 mm (range 16-48 mm; median 25 mm). A VEDUM map is highly accurate in defining a conductive vulnerable zone of the VT circuit. The longest EGM duration within the isthmus is highly predictive of rapid VT termination at the first radiofrequency delivery even in the case of large isthmuses.